AWUS01 KWNH 220603
FFGMPD
MNZ000-SDZ000-221200-

Mesoscale Precipitation Discussion 0972
NWS Weather Prediction Center College Park MD
202 AM EDT Fri Aug 22 2025

Areas affected...central and eastern SD into some adjacent
portions of MN

Concerning...Heavy rainfall...Flash flooding possible

Valid 220600Z - 221200Z

Summary...Training and repeating of very heavy rainfall (up to
2-4"/hr rates) may lead to isolated to scattered instances of
flash flooding overnight.

Discussion...Discrete convection is beginning to backbuild and
proliferate this evening, in the vicinity of a sharp baroclinic
zone with strong low-level frontogenesis. The mesoscale
environment is otherwise characterized by MLCAPE of 1000-2500
J/kg, PWs of 1.2-1.5" (near the 90th percentile, per ABR sounding
climatology), and effective bulk shear of 35-45 kts. While
steering flow is relatively strong at 20-30 kts towards the ESE
with Corfidi vectors favoring southward propagation, current
storms are anchored in the boundary layer near where low-level
convergence is maximized with backbuilding towards the west
favoring training/repeating of very heavy rainfall (with MRMS
estimates indicating rates as high as 2-4"/hr).

Latest hi-res guidance (00z HREF suite) is in remarkably good
agreement with regard to the spatial axis of heavy rainfall,
located in excellent proximity to where convection has
proliferated. While the guidance is not in as good agreement with
regard to the intensity of convection, the HREF does still
indicate the extreme potential well with probabilities for 3" and
5" exceedance of 40-50% and 5-10%, respectively (with the 00z ARW2
and NAM-nest being the most aggressive in depicting 3-5" totals,
along with some recent hourly runs of the experimental RRFS).
Isolated to scattered instances of flash flooding are possible
(with 3-hr FFGs generally ranging from 1.5-2.5" and associated
HREF FFG exceedance probs of 30-40%), though impacts to life and
property will likely be rather limited given how rural/sparsely
populated the region is.

Churchill

...Please see https://urldefense.com/v3/__http://www.wpc.ncep.noaa.gov__;!!= DZ3fjg!62MjQZu1P30gFyRVFCIkljS7l3mHwOxLYzCOgJ7Dhz2d6bPgwec8ea20I81V77QKnax1= MBzyilZJvirpO1vs87e3uGc$ for graphic product...

ATTN...WFO...ABR...FSD...MPX...UNR...

ATTN...RFC...KRF...MSR...NWC...

LAT...LON 45309819 44869613 43889656 43699801 44049944=20
44800116 45270021=20

=3D =3D =3D
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AWUS01 KWNH 221553
FFGMPD
SCZ000-FLZ000-GAZ000-222152-

Mesoscale Precipitation Discussion 0973
NWS Weather Prediction Center College Park MD
1153 AM EDT Fri Aug 22 2025

Areas affected...portions of South Carolina, eastern Georgia, and
far northeastern Florida

Concerning...Heavy rainfall...Flash flooding likely

Valid 221552Z - 222152Z

Summary...Scattered, slow-moving storms will increase in coverage
through the afternoon, with areas of 2-3 inch/hr rain rates
becoming likely. Flash flooding is expected, especially in
urban/low-lying areas.

Discussion...Scattered, shallow convection has persisted across
much of central South Carolina this morning downstream of a weak
mid-level trough along the southern Appalachians. Over the past
hour or so, deeper, more intense convection has materialized
mainly along weak front extending from southern Georgia
east-northeastward near the South Carolina coastline. The deeper
convection has materialized in a very favorable environment for
heavy rainfall (2-2.3 inch PW values, 1500+ J/kg MLCAPE, weak
steering flow aloft). Areas of 2-3 inch/hr rain rates have
materialized near the Charleston Metro area (including 0.9 inch in
15 minutes at WFO Charleston and 2.25 inches in 30 minutes at KCHS
recently).

Over time, convection is expected to deepen and expand in coverage
across the discussion area as surface heating promotes continued destabilization along with convergence along the aforementioned
front. Heavy rain may also concentrate along any subtle
sea-breeze boundaries that develop along the Georgia and Florida
coastlines. Additional areas of 2-3 inch/hr rain rates are
expected that should promote inundation especially in
sensitive/urban locales. Convection should also be slow-moving
given the relatively weak kinematics for steering flow aloft. FFG
thresholds vary across the discussion area and peak at around 3
inches/hr in less-sensitive spots, although these rates could
still be exceeded occasionally given the moisture-rich environment
in place supporting convective activity. Several instances of
flash flooding are likely in this scenario.

Cook

...Please see https://urldefense.com/v3/__http://www.wpc.ncep.noaa.gov__;!!= DZ3fjg!_LxZGx6JC90Ce7XuKT6ir5Rk5UuRYcke3vtuIUfuTIvsZ_ip0pM9QlWoQ2w1Q3gwtA1s= 1pGz8GUa9wNbHm9Vr2OXYQA$ for graphic product...

ATTN...WFO...CAE...CHS...FFC...ILM...JAX...TAE...

ATTN...RFC...ALR...NWC...

LAT...LON 33697952 33017912 32048012 30058119 29668148=20
30268266 31078390 32068362 33078250 33658108=20 =20=20=20=20=20=20=20=20=20=20=20=20

=3D =3D =3D
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AWUS01 KWNH 221612
FFGMPD
LAZ000-TXZ000-222211-

Mesoscale Precipitation Discussion 0974
NWS Weather Prediction Center College Park MD
1212 PM EDT Fri Aug 22 2025

Areas affected...southeast Texas, southwestern Louisiana

Concerning...Heavy rainfall...Flash flooding likely

Valid 221611Z - 222211Z

Summary...Slow-moving convection continues to expand in coverage
this morning, with areas of 2-3 inch/hr rain rates becoming likely
beneath the strongest storms. Flash flooding is expected.

Discussion...Deep convection has been focused mainly along coastal
areas of Texas and Louisiana for most of the morning. Over the
past hour or so, storms has materialized just inland across the
discussion area (nearer to I-10) due to 1) strong surface heating/destabilization, 2) abundant moisture (2.3 inch PW), and
3) convergence along a weak front across the region (generally
from Houston Metro east to Baton Rouge, LA). Kinematics/steering
flow aloft are very weak (<5 knots), suggestive of slow-moving
cells/clusters that are outflow dominant and propagate erratically
through the afternoon. A few of these clusters were forming near
Lake Charles and just north of Houston while already producing
spots of 1-2 inch/hr rain rates.

With continued surface heating, convective clusters are expected
to expand in coverage. The orientation of storms relative to
outflow from prior activity over the Gulf suggests potential for
several cell mergers as well. 2-3 inch/hr rain rates will
eventually materialize, and may impact populated/flashy urban
centers such as Lake Charles, Beaumont, and Houston through 20Z.=20
FFGs near those areas are as low as 1-1.5 inches/hr and should be
readily exceeded. Surrounding areas have higher FFGs (in the 3
inch/hr range) that should still be exceeded as stronger
convection develops through the morning and early afternoon.=20
Areas of flash flooding are expected given the developing scenario.

Cook

...Please see https://urldefense.com/v3/__http://www.wpc.ncep.noaa.gov__;!!= DZ3fjg!_wnU-7iT7MQkYAxXh3Al7S-FyxNAXNu1ZJgZgdIZDhdtW2AyLf32LS_uGSkr5tNcXItn= 2FSdcby0QR_ZutRo08dJZtc$ for graphic product...

ATTN...WFO...CRP...EWX...HGX...LCH...

ATTN...RFC...FWR...ORN...NWC...

LAT...LON 31019345 30519193 29869179 29589269 29619471=20
28749616 29029737 29879728 30399670 30939521=20 =20=20=20=20=20=20=20=20=20=20=20=20

=3D =3D =3D
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AWUS01 KWNH 221701
FFGMPD
ALZ000-MSZ000-LAZ000-222259-

Mesoscale Precipitation Discussion 0975
NWS Weather Prediction Center College Park MD
100 PM EDT Fri Aug 22 2025

Areas affected...southeastern Louisiana, coastal areas of
Mississippi, far southern Alabama

Concerning...Heavy rainfall...Flash flooding possible

Valid 221659Z - 222259Z

Summary...Spotty/isolated flash flood potential exists with
slow-moving thunderstorms across the discussion area through
22Z/4p CDT.

Discussion...Recent satellite imagery indicates deepening
convection along a variety of subtle low-level confluence
boundaries across the discussion area. Surface heating across the
region has enabled development of 4000 J/kg SBCAPE in the
pre-convective airmass amid 2.2 inch PW values. Deep, efficient
convective process are already supporting spots of 1 inch/hr rain
rates (estimated per MRMS). Additional areas of 1-2 inch/hr rain
rates should develop through the afternoon as additional cells
develop and mergers begin to occur.

The rainfall will occur on locally sensitive areas due to
urbanized/hydrophobic surfaces in/near New Orleans, Baton Rouge,
and Northshore Lake Pontchartrain near Covington and Slidell.=20
Isolated instances of flash flooding will become more probable
during the afternoon hours.

Much of the convective (and flash flood) threat will be diurnally
driven today, although the degree of convective overturning will
ultimately modulate the spatiotemporal threat of the flash flood
risk through 22Z/4p CDT. Eventually, widespread low-level
stabilization should result in a lower flash flood threat,
although this scenario should take a few hours to play out.

Cook

...Please see https://urldefense.com/v3/__http://www.wpc.ncep.noaa.gov__;!!= DZ3fjg!4qmc1xLRNtT4GBhZO9kPhmytNW_ywPaqGJSGgUV5OvmQLj-QXoTwpVyk4C-FDmcBh5nS= 6pa-9XnEC6gwK6RtEZ0osA4$ for graphic product...

ATTN...WFO...LCH...LIX...MOB...

ATTN...RFC...ALR...ORN...NWC...

LAT...LON 30989045 30788866 30468810 29618895 29148912=20
28969035 29399160 29889234 30659225=20

=3D =3D =3D
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AWUS01 KWNH 222102
FFGMPD
AZZ000-UTZ000-NVZ000-CAZ000-230300-

Mesoscale Precipitation Discussion 0976
NWS Weather Prediction Center College Park MD
500 PM EDT Fri Aug 22 2025

Areas affected...Far Eastern CA...Southern NV...Central to
Northwest AZ...Central and Southwest UT

Concerning...Heavy rainfall...Flash flooding possible

Valid 222100Z - 230300Z

SUMMARY...Scattered monsoonal showers and thunderstorms are
expected going through the afternoon and early evening hours
across portions of the Southwest U.S. Some localized concerns for
flash flooding will exist for the more sensitive slot canyon
locations and burn scar areas.

DISCUSSION...The early-afternoon GOES-W visible satellite imagery
shows a substantial CU/TCU field over the Mogollon Rim of central
to northwest AZ and also across much of southwest UT where a
combination of orographics along with diurnally enhanced
instability and the presence of monsoonal moisture are working to
initiate additional areas of convection. Already there are
scattered small-scale clusters of locally heavy showers and
thunderstorms where differential boundaries and nearby
terrain-induced circulations have been helping to initiate and
locally concentrate pockets of convection.

Early day cloud cover has locally helped to mitigate the level of
surface-based instability, but satellite trends show substantial
heating occurring over much of central to northwest AZ and into
southwest UT which should help to facilitate additional scattered
areas of showers and thunderstorms over the next several hours.
There is also proximity of an MCV near the CA/AZ/NV border region,
and differential heating along the eastern and northern flanks of
this energy and associated cloud canopy may also help drive
convective initiation this afternoon.

The region is relatively moist today with PW anomalies coming in
as high as 1.5 standard deviations above normal in close proximity
to a 700 mb high center. CIRA-ALPW data generally shows some of
the greater moisture concentrations in the 700/500 mb layer and
this will help to support some relatively efficient convection for
heavier rainfall rates.

Some rainfall rates may reach as high as 1 inch in 20 to 30
minutes with the stronger cells, with some spotty rainfall totals
through this evening reaching as high as 1.5 to 2.5 inches where
any cells tend to become anchored near areas of higher terrain.
Some of the RRFS/REFS guidance supports this which seems plausible
given the satellite and radar trends. This may result in there
being localized areas of flash flooding. There are some sensitive
burn scar concerns (especially over northern AZ) along with the
normally sensitive slot canyon locations (southwest to
south-central UT) that are vulnerable to any high rainfall rate
activity, so these areas should be closely monitored.

Orrison

...Please see https://urldefense.com/v3/__http://www.wpc.ncep.noaa.gov__;!!= DZ3fjg!6YDKnBG52iNQy2dp4u55cuA3H6DEvnr6GvljAi0db6MzWMTR4mtzjPNmMZaJFgSeFft9= I8oOgLEK3VFG52FX71C-Dhc$ for graphic product...

ATTN...WFO...FGZ...LKN...PSR...SLC...VEF...

ATTN...RFC...RSA...STR...NWC...

LAT...LON 39181115 39001068 37981065 36701168 35571155=20
34731061 34291023 33791048 33641127 33651273=20
33791397 34251523 35121602 36071625 36881610=20
37781544 38421455 38751351 38861244=20

=3D =3D =3D
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AWUS01 KWNH 222156
FFGMPD
COZ000-230355-

Mesoscale Precipitation Discussion 0977
NWS Weather Prediction Center College Park MD
555 PM EDT Fri Aug 22 2025

Areas affected...Eastern CO

Concerning...Heavy rainfall...Flash flooding possible

Valid 222155Z - 230355Z

SUMMARY...Showers and thunderstorms should gradually expand in
coverage this evening. Some cell-merger and cell-training concerns
may cause some isolated areas of flash flooding.

DISCUSSION...The latest GOES-E IR satellite imagery shows cooling
convective tops near the Front Range and Palmer Divide which are
expected to gradually grow upscale a bit this evening with some
gradual consolidation into some loosely organized MCS activity
over eastern CO this evening. The convection is forming in close
proximity to a stationary front with the additional aid of
orographic ascent/forcing within a moderately unstable environment.

Much of the instability pool is along and just north of the front
in this case with MLCAPE values across north-central to northeast
CO as high as 1500 J/kg. This is mainly due to the fact that
surface dew points (locally 55 to 60+) just north of the front are
quite a bit higher than they are to the south out ahead of it.
Weak shortwave energy rounding the top of a mid-level ridge near
the Four Corners region will eject down across eastern CO this
evening and interact with this instability axis and the
aforementioned frontal zone to support the upscale growth of
convection.

A consensus of the latest 12Z HREF/REFS guidance suggests some
spotty areas of 2 to 4 inch rainfall totals will be possible where
some localized cell-merger and cell-training activity occurs. Both
the HREF and REFS depict some low to moderate probabilities
(generally 30 to 50 percent) of seeing the 3-hour FFG values
exceeded this evening as this shower and thunderstorm activity
continues to grow in coverage and intensity. As a result, some
isolated areas of flash flooding will be possible.

Orrison

...Please see https://urldefense.com/v3/__http://www.wpc.ncep.noaa.gov__;!!= DZ3fjg!681kSBXyaO26XX5rMnmZmakGChP-LhLm_c90fIFh-sXfDp-iV-DoBI83gR2vw9ltl-a2= 6C4esbBRDCgavWH6nVFlFtU$ for graphic product...

ATTN...WFO...BOU...GLD...PUB...

ATTN...RFC...KRF...TUA...NWC...

LAT...LON 40310271 39540211 38850248 38240349 37880472=20
38070552 38580579 39360560 40030443=20

=3D =3D =3D
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AWUS01 KWNH 222232
FFGMPD
SCZ000-FLZ000-GAZ000-230430-

Mesoscale Precipitation Discussion 0978
NWS Weather Prediction Center College Park MD
630 PM EDT Fri Aug 22 2025

Areas affected...Southern and Eastern GA...SC Lowcountry

Concerning...Heavy rainfall...Flash flooding likely

Valid 222230Z - 230430Z

SUMMARY...Additional areas of very heavy shower and thunderstorm
activity going through the evening hours will maintain a
likelihood for more areas of flash flooding.

DISCUSSION...The late-day GOES-E IR satellite imagery in
conjunction with regional radar shows broken areas of very heavy
shower and thunderstorm activity continuing to impact areas of the
SC Lowcountry on down through eastern and southern GA. A
combination of a stationary front along with multiple mesoscale
outflow boundary collisions within a very moist and unstable
airmass continues to facilitate the ongoing convection, and
additional clusters of convection should continue into the evening
hours.

MLCAPE values are as high as 1500 to 2500 J/kg and this coupled
with PWs of 2.2 to 2.4 inches will drive rainfall rates to locally
still be well into the 2 to 3 inch/hour range with the stronger
storms at least through early this evening.

The additional rainfall footprint this evening will be dictated by
the longevity of the instability pool along the front, but also
mitigated by the proximity of convergent and moist low-level flow
near the front, and with some weak right-entrance region upper jet
forcing overhead.

Recent runs of the experimental WoFS along with the HRRR and RRFS
guidance suggest the convection may linger well into the evening
hours, with some rather heavy additional totals. The steering flow
over the region is also rather weak, and this is supporting slow
cell-motions which with the high rainfall rates will favor some
additional rainfall totals locally reaching 3 to 5 inches. In
fact, the 90th percentile of the 6-hour QPF from the 21Z WoFS run
suggests parts of south-central GA may see additional rainfall
totals locally exceeding 6+ inches.

Given the setup and additional rainfall potential, more areas of
flash flooding are likely to occur going into the evening hours.

Orrison

...Please see https://urldefense.com/v3/__http://www.wpc.ncep.noaa.gov__;!!= DZ3fjg!-98S0FHjnkcohEfm_nUkKVaiZlQrId7Kl_gFVyksAPYyKlrHPOkpHeJVtfjDnAFk0Lus= qEVHPwURi9hindXil4gpUDM$ for graphic product...

ATTN...WFO...CAE...CHS...FFC...ILM...JAX...TAE...

ATTN...RFC...ALR...NWC...

LAT...LON 33668279 33588217 32958109 33387968 32897949=20
32587992 32028077 30918166 30608323 30948457=20
31638505 32268485 32918396=20

=3D =3D =3D
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AWUS01 KWNH 222315
FFGMPD
NVZ000-CAZ000-230500-

Mesoscale Precipitation Discussion 0979
NWS Weather Prediction Center College Park MD
713 PM EDT Fri Aug 22 2025

Areas affected...Portions of the Sierra Nevada

Concerning...Heavy rainfall...Flash flooding possible

Valid 222313Z - 230500Z

SUMMARY...Scattered slow-moving areas of showers and thunderstorms
over the Sierra Nevada late this afternoon and early this evening
may cause some localized concerns for flash flooding.

DISCUSSION...The mid-afternoon GOES-W Day Cloud Phase RGB
satellite imagery along with LightningCast data shows convection
initiating and gradually increasing in coverage over portions of
the Sierra Nevada. The convection that is initiating is in
response to strong diurnal heating with increasing instability and terrain-driven circulations in a rather moist monsoonal regime.

SBCAPE values have risen to over 1000 K/kg along the western
flanks of the Sierra Nevada involving eastern CA with surface data
showing modest upslope flow into the higher terrain. The latest
RAP analysis generally suggests about 10 to 15 kts of southerly
flow in the 850/700 mb layer from Lake Tahoe southward down
Bishop.

Coinciding with this is a rather moist mid-level column with
CIRA-ALPW showing elevated moisture in the 700/500 mb layer and
this is supporting PW anomalies across the region of 2.0 to 2.5
standard deviations above normal. Deep layer southerly flow around
the western periphery of the subtropical ridge over the Southwest
U.S. is facilitating the poleward transport of monsoonal moisture
up across these areas, and this is expected to help drive a threat
for scattered heavy shower and thunderstorm activity going through
the evening hours.

Overall, the latest hires model guidance is rather ill-defined
with the convective footprint. However, the satellite and radar
trends suggest concerns for showers and thunderstorms to be
locally anchored near the higher terrain this evening with some
backbuilding characteristics which is further supported by weak
propagation vectors and the orographic focus that is in place for
development.

Rainfall rates with the stronger storms may reach 0.75 to 1.0
inch/hour, with potential for much of this to fall in as little as
30 minutes. Spotty storm totals of 1.5 to 2.5 inches will be
possible where any repeating cell-activity occurs. Given the
setup, some localized areas of flash flooding will be possible
going through this evening, and this will include potential for
some burn scar impacts.

Orrison

...Please see https://urldefense.com/v3/__http://www.wpc.ncep.noaa.gov__;!!= DZ3fjg!_OhMyc7fizNcmV1Zhs2kWs62h4JevC1T6VoPZceqfq68OcDmk6RuxOXJXenwnfgBNS3a= 4WNIU4xmsTc3C9scPSrd_d8$ for graphic product...

ATTN...WFO...HNX...REV...VEF...

ATTN...RFC...RSA...NWC...

LAT...LON 39371907 39131865 38311816 37671790 37091777=20
36501775 36361800 36391833 36691869 37431910=20
38031941 38741982 39181969=20

=3D =3D =3D
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AWUS01 KWNH 231117
FFGMPD
SCZ000-231616-

Mesoscale Precipitation Discussion 0980
NWS Weather Prediction Center College Park MD
716 AM EDT Sat Aug 23 2025

Areas affected...coastal areas of South Carolina

Concerning...Heavy rainfall...Flash flooding possible

Valid 231116Z - 231616Z

Summary...Localized areas of flooding are expected over the next
4-6 hours (through 16Z/noon EDT) as convection over the Gulf
Stream slowly migrates inland toward coastal areas of South
Carolina.

Discussion...Recent radar/satellite imagery indicates a fetch of
deep convection along an axis from near Charleston to about 80-100
miles east-southeast of Charleston. The convection was likely
being maintained by several synoptic features, including 1) a
mid-level vorticity maximum over Georgia that was providing ascent
aloft over the region and 2) low-level easterly flow just north of
a weak low near Savannah that was helping to maintain moderate
instability (1000+ J/kg SBCAPE) right along coastal areas. An
abundantly moist airmass (2.3 inch PW) remains in place,
supporting efficient rainfall processes with stronger cells that
develop. Additionally, parts of the region experienced 3-8 inches
of rainfall over the past 24 hours, and onshore flow was
persisting during this morning's high tide, which was likely
resulting in inundation of low-lying coastal areas along with
hindered runoff/drainage.

The ongoing convective trends should continue for the next 4-6
hours. Areas of 1 inch/hr rain rates have began near Charleston
over the past 30 minutes, and these rates should continue
periodically while the convective axis in maintained in the
region. Areas of 2-3 inch rainfall totals are expected. Over
time, the convective axis should drift northward and/or weaken (as
depicted by CAMs), although this process should take several hours
to unfold.

Flooding is possible along coastal areas this morning and could be
enhanced by the locally heavy rainfall that periodially moves
onshore.

Cook

...Please see https://urldefense.com/v3/__http://www.wpc.ncep.noaa.gov__;!!= DZ3fjg!5WIE0gVjrnZ8e9Dfw0R5PBJGhSnKCAAZNTQaNH8c6g0ZibOBmamIJ7VmmBabubuODsTR= z-GQ0iQ1w7YJ2rxtgEZwLLA$ for graphic product...

ATTN...WFO...CHS...ILM...

ATTN...RFC...ALR...NWC...

LAT...LON 33677915 33507868 32378027 32728065 33387996=20 =20=20=20=20=20=20=20=20=20=20=20=20

=3D =3D =3D
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AWUS01 KWNH 231334
FFGMPD
SCZ000-GAZ000-231933-

Mesoscale Precipitation Discussion 0981
NWS Weather Prediction Center College Park MD
934 AM EDT Sat Aug 23 2025

Areas affected...central/southern Georgia

Concerning...Heavy rainfall...Flash flooding likely

Valid 231333Z - 231933Z

Summary...A few instances of flash flooding are expected today
across Georgia. Heavy rainfall, with rain rates approaching 2
inches/hr at times, are expected through 19Z/3p EDT.

Discussion...An axis of shallow, slow-moving convection was
located along subtle low-level confluence zone extending from near
Peachtree City to Sandersville/east of Macon this morning.=20 Ascent/convergence along this axis and the presence of a mid-level
wave aloft has aided in persistence of convection across the
region despite modest amounts of surface-based instability (~500
J/kg). The convection is in an abundantly moist environment (2+
inch PW values), supporting efficient rainfall processes. Spots
of 2 inch/hr rain rates are estimated per MRMS currently, which
isn't surprising given the moist airmass and slow movement of
convection along the convergence axis.

The ongoing scenario for heavy rainfall should persist for a few
hours - and perhaps through 19Z/3p EDT today. SPC mesoanalysis
indicate an axis of deep moist convergence collocated with the
axis of convection that should migrate very slowly or even stall.
Areas of heavy rainfall are expected, and local rainfall totals
exceeding 3-5 inches are possible depending on the persistence of
convection at any one locale. Breaks in the cloud cover south of
this confluence axis suggests that additional convection may
develop and produce heavy rainfall (>1 inch/hr rain rates) that
may also cause flash flood instances - especially in areas that
received 2-5 inches yesterday in/near Macon. Flash flooding is
likely given the aforementioned scenario.

Cook

...Please see https://urldefense.com/v3/__http://www.wpc.ncep.noaa.gov__;!!= DZ3fjg!44rJHtEiQZGfgSQQTHfuh8tyvC4bKOVRlLnGaj0EwACrdxHIU2cyGTRRbwrZc7ZCNQjy= UNVISK16-GTon4POigRl_OY$ for graphic product...

ATTN...WFO...CAE...CHS...FFC...JAX...TAE...

ATTN...RFC...ALR...NWC...

LAT...LON 33938451 33868302 33228107 32328070 31748183=20
31608442 33198502=20

=3D =3D =3D
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AWUS01 KWNH 231627
FFGMPD
SCZ000-GAZ000-232025-

Mesoscale Precipitation Discussion 0982
NWS Weather Prediction Center College Park MD
1226 PM EDT Sat Aug 23 2025

Areas affected...far southern South Carolina, coastal areas of
Georgia

Concerning...Heavy rainfall...Flash flooding possible

Valid 231625Z - 232025Z

Summary...Heavy rainfall will continue to impact coastal areas
near Savannah, GA over the next 3 hours or so. Flash flooding
remains possible, and could be locally enhanced by coastal
flooding/inundation.

Discussion...Although widespread convective overturning has
stabilized much of the state of South Carolina, a small/focused
area of instability resides across far southern portions of the
state and in/near the Savannah, GA area. Weak low-level onshore
flow just north of a low has maintained ~1500 J/kg SBCAPE in that
area. PW values approaching 2.4 inches are also maximized there.
The buoyancy/moisture combo is combining with weak steering flow
aloft to foster deep convection with slow storm motions and
1.5-2.5 inch/hr rain rates currently.

The heavy rainfall continues to migrate inland toward areas that
have experienced high tide earlier this morning and 3-9 inch
rainfall totals over the past 24 hours. Wet soils and onshore
flow should continue to hinder runoff/drainage and - when combined
with heavy rainfall - may continue to pose flood/flash flood risk
over the next 2-4 hours (through 20Z/4p EDT).

Cook

...Please see https://urldefense.com/v3/__http://www.wpc.ncep.noaa.gov__;!!= DZ3fjg!_UC_6F2jmHZTTzSvk22UUH3dyf-73ZfElHqEmsdA96Xt6LGDaoxt7ZeHReqjyolQH_3n= ZWX8ZbuhPBFajMKMkGWMNFo$ for graphic product...

ATTN...WFO...CHS...JAX...

ATTN...RFC...ALR...NWC...

LAT...LON 32728052 32358055 31258117 31258178 31708196=20
32368162=20

=3D =3D =3D
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AWUS01 KWNH 231838
FFGMPD
NVZ000-CAZ000-240037-

Mesoscale Precipitation Discussion 0983
NWS Weather Prediction Center College Park MD
237 PM EDT Sat Aug 23 2025

Areas affected...Southern and Eastern CA...Sierra Nevada

Concerning...Heavy rainfall...Flash flooding likely

Valid 231837Z - 240037Z

SUMMARY...Deep layer monsoonal moisture advancing up across
southern and eastern CA and into the higher terrain of the Sierra
Nevada will foster scattered to broken areas of heavy showers and
thunderstorms this afternoon. Scattered areas of flash flooding
are likely, and especially over the Sierra Nevada.

DISCUSSION...The deeper layer subtropical ridge over the Southwest
is in a very favorable position to facilitate the northwestward
transport of monsoonal moisture up across southern and eastern CA
and well into the Sierra Nevada. The latest CIRA-ALPW data shows
moisture near or above the 90th percentile of climatology in the
700/500 mb and 500/300 mb layers respectively across the region,
with PW anomalies overall running a solid 2 to 3 standard
deviations above normal.

This moisture coupled with placement of elongated mid-level vort
energy and deeper layer upslope flow over the higher terrain will
combine with increasing boundary layer instability for scattered
to eventually broken areas of heavy shower and thunderstorm
activity. Cloud cover over portions of the Transverse and
Peninsular Ranges of southern CA have mitigated the build up of
instability to a degree, but the proximity of vort energy and
steeper mid-level lapse rates have already been focusing an axis
of showers and thunderstorms. This activity should tend to expand
a bit in coverage as differential heating boundaries and greater
instability adjacent to the terrain help to drive additional
mesoscale-enhanced circulations for new convective development.

The Sierra Nevada overall is the area that will likely see the
greatest concentration of heavier rainfall though given the level
of anomalous moisture in place along with upslope flow. Even the
hires CAM model guidance which can suffer with convective details
over the Sierra Nevada has a footprint for impactful rainfall,
including a signal for locally repeating cell-activity. The most
recent visible satellite imagery along with LightningCast data
shows convective initiation underway and suggestive of multiple
rounds of convective potential in conjunction with the full
diurnal heating cycle.

Given the high moisture environment, rainfall rates up to 1.5
inches/hour will be possible, with some localized storm total
amounts by late this afternoon of 2 to 4 inches possible where any
cells tend to become more terrain-anchored. Scattered areas of
flash flooding are likely with today's convection, with the
greatest threat over the Sierra Nevada where there will also be
some burn scar sensitivities.

Orrison

...Please see https://urldefense.com/v3/__http://www.wpc.ncep.noaa.gov__;!!= DZ3fjg!6jxbe72gLfvIl9oz_JQC2znK8LlCdDdfWl3Xj-JLfB9zPHkxSOiX7WrfOspbc1NhzrPw= ZSbUFG5s2dL5xWppXQEBwZU$ for graphic product...

ATTN...WFO...HNX...LOX...PSR...REV...SGX...STO...VEF...

ATTN...RFC...RSA...STR...NWC...

LAT...LON 39211974 39091885 38021760 36821708 35361691=20
34501635 33481530 32731533 32551597 32621671=20
33251717 33711785 34061855 34571913 35431918=20
36151891 37041920 38001996 38692010=20

=3D =3D =3D
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AWUS01 KWNH 231850
FFGMPD
SCZ000-FLZ000-GAZ000-240048-

Mesoscale Precipitation Discussion 0984
NWS Weather Prediction Center College Park MD
250 PM EDT Sat Aug 23 2025

Areas affected...southern/southeastern Georgia, southern/coastal
South Carolina, northern Florida

Concerning...Heavy rainfall...Flash flooding possible

Valid 231848Z - 240048Z

Summary...Scattered, slow-moving storms will continue to produce
areas of 1-2.5 inch/hr rain rates at times. Flash flooding is
possible - especially where heavy rain falls on
sensitive/urbanized ground conditions.

Discussion...Flash flood potential continues across much of
southern Georgia and coastal areas of Georgia and South Carolina.
Most of the deep convection was focused along and south of a weak
differential heating and zone currently across central Georgia
from just south of Atlanta through Macon to just north of
Savannah. Along and south of this confluence zone, pockets of
heating with an abundantly moist airmass (2+ inch PW values) has
contributed to scattered development of deep convection. Weak
steering flow aloft has allowed for slow and at times erratic
storm motions along with several mergers, enabling rain rates to
exceed 2 inches/hr at times in a few spots. Some of the heavy
rain was falling on areas experiencing local inundation/poor
drainage due to onshore flow along coastal areas, resulting in
several instances of flooding impacts. In other areas, rainfall
was occurring atop spots of 3-9 inch rainfall totals over the past
24 hours, resulting in wet soils and increased potential for
runoff.

Ongoing convective trends will continue through at least 00Z/8p
EDT tonight, with locally sensitive areas experiencing a continued
threat of heavy rainfall. Several instances of flash flooding are
possible, and local enhancement of flash flood risk from onshore
flow near coastal areas should continue. Modest destabilization
has also occurred along South Carolina coastal areas near
Charleston, and although a lull in deep convective activity has
been observed over the past 1-2 hours, redevelopment of rainfall
(and 1 inch/hr rates) may occur through the evening, renewing the
flash flood risk in that area.

Cook=20

...Please see https://urldefense.com/v3/__http://www.wpc.ncep.noaa.gov__;!!= DZ3fjg!5L-IkteKJH6e1ootPivcfjqIomPwV-vQ-l3ndi3zZ3msMBGXcVhgEgfOSrp73PGeFUD0= PnuOhvSz8UytAWnDiq-wlL0$ for graphic product...

ATTN...WFO...CHS...FFC...JAX...TAE...

ATTN...RFC...ALR...NWC...

LAT...LON 33227991 33137938 31438111 30298167 30118367=20
30148500 30808506 31298437 31998462 32748465=20
32768322 32788091=20

=3D =3D =3D
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AWUS01 KWNH 231932
FFGMPD
AZZ000-UTZ000-NVZ000-CAZ000-240130-

Mesoscale Precipitation Discussion 0985
NWS Weather Prediction Center College Park MD
331 PM EDT Sat Aug 23 2025

Areas affected...Central to Southwest UT...Central to Northwest
AZ...Southern NV...Far Eastern CA

Concerning...Heavy rainfall...Flash flooding likely

Valid 231930Z - 240130Z

SUMMARY...Monsoonal moisture entrenched over the Southwest U.S.
will support locally heavy showers and thunderstorms through this
afternoon. Scattered areas of flash flooding will be likely today,
and especially near and around the more sensitive slot canyon and
burn scar locations.

DISCUSSION...A deep layer subtropical ridge near the Four Corners
region has allowed monsoonal moisture to become rather well
entrenced around its western flank over the last couple of days,
with PW anomalies this morning reaching as high as 2 to 3 standard
deviations above normal across far eastern CA up through southern
NV and into far northwest AZ and adjacent areas of central to
southwest UT.

The moisture is quite concentrated in the 700/300 mb layer based
on the latest CIRA-ALPW data and this coupled with orographics and
additional daytime heating/surface-based instability will favor
expanding areas of showers and thunderstorms with elevated
rainfall rates capable of reaching 1.5+ inches/hour. SBCAPE values
of 1000+ J/kg are already noted over portions of central AZ and
also over southern UT where there has also been recent convective
development, and these values should continue to increase in the
near-term.

Given the influence of orographics/terrain-driven circulations and
eventually convectively-driven outflow boundaries, there should be
pockets of locally focused convection where some of the rainfall
totals may reach as high as 2 to 4 inches. This will be supported
by the anomalous moist monsoonal environment that is generally in
place.

These rainfall totals may result in there being enhanced
runoff/debris flow concerns near any burn scar locations, and
portions of northern AZ in particular are notably sensitive due to
recent fire activity. Adjacent areas of southwest to central UT
will also have concerns once again for slot canyon flash flooding
which may be locally significant today. The flash flood threat is
more conditional across southern NV and adjacent areas of far
eastern CA, but in general across the MPD area, scattered areas of
flash flooding are likely going through the afternoon hours as
convection develops and expands in coverage.

Orrison

...Please see https://urldefense.com/v3/__http://www.wpc.ncep.noaa.gov__;!!= DZ3fjg!65ZV872x4R4Qvt_5TfR9p-kqddEwY-iXRwyh16S5PczJCf7cD-cJfgjOZNR9ot_2JdbC= eJf8ehBmU-TSd3v0mkXwugw$ for graphic product...

ATTN...WFO...FGZ...PSR...SLC...VEF...

ATTN...RFC...RSA...STR...NWC...

LAT...LON 39341208 38941097 37831070 35911120 34661037=20
33741076 33661308 34531532 35851597 37191572=20
37961485 38631382=20

=3D =3D =3D
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AWUS01 KWNH 231956
FFGMPD
COZ000-NMZ000-240155-

Mesoscale Precipitation Discussion 0986
NWS Weather Prediction Center College Park MD
356 PM EDT Sat Aug 23 2025

Areas affected...Central and Southern CO...Northern NM

Concerning...Heavy rainfall...Flash flooding likely

Valid 231955Z - 240155Z

SUMMARY...Heavy showers and thunderstorms will continue to expand
in coverage over the next few hours. Scattered areas of flash
flooding will be likely which may include some localized burn scar
impacts.

DISCUSSION...The early-afternoon GOES-W IR satellite imagery shows
broken areas of heavy showers and thunderstorms impacting portions
of central and southern CO on down into northern NM. Additional
expansion of convection is expected over the next few hours as
diurnal heating/instability coupled with very favorable orographic ascent/terrain-induced circulations continues to support vertical
updrafts for convective initiation and sustenance.

MLCAPE values over northern NM and southern CO are locally over
1000+ J/kg and the region is quite moist with PW anomalies of 1.5+
standard deviations above normal. Some mid to high-level monsoonal
moisture wrapping around the northeast flank of the Four Corners
subtropical ridge is contributing to this more anomalous moisture
profile.

The latest hires guidance strongly suggests that some of the
heaviest rainfall this afternoon will tend to be over the Sangre
De Cristo Range where some spotty 2 to 4 inch rainfall totals will
be possible. Both the 12Z HREF and 06Z REFS guidance support these
amounts. Locally heavy rainfall totals are expected though as far
north as central CO by later this afternoon as diurnal heating,
orographics and even some stronger shear profiles help to support
stronger updrafts and locally heavy rainfall rates which may reach
1.5+ inches/hour.

Given the higher rainfall rates and localized storm potential near
the more orographically favored terrain, there will likely be
scattered areas of flash flooding including potential for burn
scar impacts.

Orrison

...Please see https://urldefense.com/v3/__http://www.wpc.ncep.noaa.gov__;!!= DZ3fjg!7f21XVrSoxBvMaDDMJaSrE9OEHsvFlVtoddxZ7FFhHb20NIoniLTJZaFXBtcd0ZDQVAi= wannQMIr9rc4u3oWCR7OX2k$ for graphic product...

ATTN...WFO...ABQ...BOU...GJT...PUB...

ATTN...RFC...FWR...KRF...STR...TUA...NWC...

LAT...LON 39920493 39550433 38830420 37840448 37350425=20
36750370 35830381 35080455 34590558 34580648=20
35160711 36220725 37170824 38130837 39220763=20
39860642=20

=3D =3D =3D
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AWUS01 KWNH 232102
FFGMPD
VAZ000-NCZ000-WVZ000-GAZ000-TNZ000-KYZ000-ALZ000-240300-

Mesoscale Precipitation Discussion 0987
NWS Weather Prediction Center College Park MD
501 PM EDT Sat Aug 23 2025

Areas affected...TN Valley...Southern Appalachians

Concerning...Heavy rainfall...Flash flooding possible

Valid 232100Z - 240300Z

SUMMARY...Scattered slow-moving areas of showers and thunderstorms
may pose an isolated threat for flash flooding going through this
evening.

DISCUSSION...The late-afternoon GOES-E GeoColor satellite imagery
shows scattered areas of showers and thunderstorms impacting
portions of the TN Valley and the southern Appalachians with an
emphasis on the Cumberland Plateau.

Moderate buoyancy with MLCAPE values of near 1500 J/kg coupled
with modest moisture convergence near the terrain should help
sustain the convective threat through early this evening. PWs are
seasonably moist with values of 1.5 to 1.75 inches and this
coupled with the available instability will support rainfall rates
reaching as high as 1.5 to 2.5 inches/hour with the stronger
storms.

Overall, a lack of shear should keep the convection in pulse mode
through the remainder of the afternoon and evening. However, with
weak steering currents and the orographic focus of the activity
near areas of higher terrain, there may be sufficient persistence
of convection locally to yield some spotty rainfall totals of 2 to
4 inches.

The FFG values across portions of far southwest VA down through
eastern TN are relatively low, and the 12Z HREF/06Z REFS suite of
guidance shows some low to moderate probabilities (20 to 50
percent) of seeing the 3-hour FFG values exceeded going through
this evening. This suggests a threat for isolated areas of flash
flooding with these pulse areas of convection.

Orrison

...Please see https://urldefense.com/v3/__http://www.wpc.ncep.noaa.gov__;!!= DZ3fjg!_fDX79rI7xtOdKs1du2XA6IQ6eBLAMkKpP7Y6Bvjs91vWQLp5-aGgT2C6nkbskQp6VRs= ZzhsJ3Hn_Xs9PTNu2Q3ATGs$ for graphic product...

ATTN...WFO...BMX...FFC...GSP...HUN...JKL...LMK...MRX...OHX...
RLX...RNK...

ATTN...RFC...ALR...ORN...TIR...NWC...

LAT...LON 38328199 38218097 37628098 36628167 36028248=20
35288382 35068463 34978543 34618589 33938660=20
34108758 35018756 35738685 37138449=20

=3D =3D =3D
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AWUS01 KWNH 232237
FFGMPD
NVZ000-CAZ000-240330-

Mesoscale Precipitation Discussion 0988
NWS Weather Prediction Center College Park MD
635 PM EDT Sat Aug 23 2025

Areas affected...Sierra Nevada

Concerning...Heavy rainfall...Flash flooding likely

Valid 232235Z - 240330Z

SUMMARY...Locally heavy showers and thunderstorms will continue
into the evening hours along the foothills and near the crest of
the Sierra Nevada. Scattered areas of flash flooding are likely
which will include localized burn scar impacts.

DISCUSSION...GOES-W IR satellite imagery shows expanding and
cooling convective tops across the Sierra Nevada along with some
of the adjacent foothills. The convection is being strongly aided
by orographic ascent/upslope flow into the terrain coupled with
increasingly divergent flow aloft and an anomalously moist
monsoonal moisture flow pattern.

SBCAPE values of 500 to 1000 J/kg are noted along the western
slopes of the Sierra Nevada with some modest effective bulk shear
in place of 20 to 30 kts. The latest RAP analysis along with IR
satellite imagery shows evidence of a weak upper-level jet streak
lifting north up across the Central Valley of CA which is favoring
some divergent and resulting diffluent flow structures aloft.

This subtle uptick in deeper layer ascent along with the ongoing
orographic and thermodynamic support should favor additional
rounds of heavy showers and thunderstorms near the high terrain
going into the evening hours. Rainfall rates will be capable of
reaching 1 to 1.5 inches/hour given PWs running locally in the
95th+ percentile of climatology and with the aid of upslope flow.

Additional rainfall totals of 2 to 3 inches will be possible
locally through this evening where any repeating cell-activity
occurs, and this will continue to favor a likelihood for scattered
areas of flash flooding. This will include localized burn scar
impacts.

Orrison

...Please see https://urldefense.com/v3/__http://www.wpc.ncep.noaa.gov__;!!= DZ3fjg!4Ss8JmzyebEdu7vaw0Og0C1U3OsLnYIXxOKcMGCcFvSqz8Dn3Lw3KvJBnUbuRUa1EEzk= tOxO41DYm0PQsL9OYApTu4I$ for graphic product...

ATTN...WFO...HNX...REV...STO...VEF...

ATTN...RFC...RSA...NWC...

LAT...LON 40931974 40431929 39481892 38041865 36691819=20
36621906 37612001 39382058 40132048 40802021=20 =20=20=20=20=20=20=20=20=20=20=20=20

=3D =3D =3D
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AWUS01 KWNH 240121
FFGMPD
SCZ000-GAZ000-240720-

Mesoscale Precipitation Discussion 0989
NWS Weather Prediction Center College Park MD
920 PM EDT Sat Aug 23 2025

Areas affected...Coastal SC/GA

Concerning...Heavy rainfall...Flash flooding possible

Valid 240120Z - 240720Z

SUMMARY...New bands of heavy showers and a few thunderstorms may
focus along coastal areas of SC and GA overnight bringing a new
threat of flash flooding.

DISCUSSION...The early to mid-evening satellite imagery along with
surface data shows an area of low pressure beginning to take shape
along a frontal zone just off the SC/GA coast. This area of low
pressure is forecast tonight to gradually lift off to the
northeast, but be not far offshore of the SC Lowcountry. The
latest suite of guidance including the evening runs of the
experimental WoFS suggest the low center becoming better defined
and strengthening a tad along the front which should facilitate an
increase in low-level moisture convergence back into the coastal
areas of SC and GA.

An instability gradient along with an inverted surface trough is
already noted along the coast, and radar imagery is showing a new
band of warm-topped convection advancing westward back into some
of the coastal areas of the SC Lowcountry, with some separate
slow-moving cells over far eastern GA.

The recent runs of the WoFS have been trending toward somewhat
greater concentrations of warm-topped convection along the coast
over the next several hours with a trend toward somewhat heavier
rainfall totals. Some of the recent HRRR guidance has also
exhibited a similar trend.

Given the highly tropical environment with PWs of 2.2 to 2.4
inches, the rainfall will be very efficient with some of these
warm-topped convective bands capable of rates reaching 2+
inches/hour. A localized concern for cell-training will exist as
well, and thus some additional rainfall totals of as much as 3 to
5 inches cannot be ruled out overnight right along the immediate
coast.

Additional areas of flash flooding for the coastal communities
will be possible as a result, and especially with the already
saturated soil conditions and concerns locally with tidal
flooding/inundation.

Orrison

...Please see https://urldefense.com/v3/__http://www.wpc.ncep.noaa.gov__;!!= DZ3fjg!9HzLpxUO0IxceXLcfcnt7amZjmOh1qKtuez0yQTIQNUQko5TWlf18JVHM8cOOXDcsunp= 2N3ZPXxhKPjI7c5qCDhQv_c$ for graphic product...

ATTN...WFO...CHS...ILM...JAX...

ATTN...RFC...ALR...NWC...

LAT...LON 33677907 33457879 32867953 32278038 31478102=20
30948124 30958159 31508155 32318107 33118012=20 =20=20=20=20=20=20=20=20=20=20=20=20

=3D =3D =3D
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AWUS01 KWNH 241842
FFGMPD
COZ000-UTZ000-250041-

Mesoscale Precipitation Discussion 0990
NWS Weather Prediction Center College Park MD
242 PM EDT Sun Aug 24 2025

Areas affected...eastern Utah, western Colorado

Concerning...Heavy rainfall...Flash flooding possible

Valid 241841Z - 250041Z

Summary...Robust convective development is occurring ahead of a
weak disturbance over northeastern Utah. Areas of rain rates
reaching 1 inch/hr are possible. Flash flooding could occur -
especially near burn scars and other low-lying, sensitive areas.

Discussion...Recent radar/satellite imagery depicts a localized
areas of robust thunderstorm development near/just south of
Meeker, CO. The storms are being supporting by 1) a quickly
destabilizing airmass (around 1000 J/kg SBCAPE), 2) anomalously
moist PW values (near 1 inch), and ascent from a weak mid-level
disturbance over northeastern UT/southwestern WY. Mean wind
fields aloft are fairly weak, allowing ongoing convection to
exhibit only slow eastward motions. Meanwhile, ground conditions
are supporting runoff with only 0.5-1.0 inch/hr FFG thresholds
and, with burn scars noted across the region representing enhanced
runoff potential.

Most of the convection across the discussion area should be
diurnally driven today. Convective coverage will continue to
increase through peak heating hours, and slow movement/cell
mergers should all support local FFG exceedance/1 inch/hr rain
rates at times beneath the deepest convection. The flash flood
risk should be highest near burn scars and
low-lying/terrain-favored areas. Flash flood potential should
persist through at least 00Z/6p MDT this evening on an isolated
basis.

Cook

...Please see https://urldefense.com/v3/__http://www.wpc.ncep.noaa.gov__;!!= DZ3fjg!-XgB761n-7HR79fQWmNLHDJ5Tt41fnz3IYepC3Bp4ZcpBm6IeBn7hq9Bh296IYQQiH2E= 1JfK9kXDWOLKE7BDM3Z9Sic$ for graphic product...

ATTN...WFO...BOU...GJT...PUB...SLC...

ATTN...RFC...FWR...KRF...STR...TUA...NWC...

LAT...LON 40670853 40630674 39770585 38630573 37630593=20
37090752 37291008 38661082 40160981=20

=3D =3D =3D
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AWUS01 KWNH 241900
FFGMPD
NVZ000-CAZ000-250100-

Mesoscale Precipitation Discussion 0991
NWS Weather Prediction Center College Park MD
300 PM EDT Sun Aug 24 2025

Areas affected...Sierra Nevada...Western Nevada

Concerning...Heavy rainfall...Flash flooding likely

Valid 241900Z - 250100Z

SUMMARY...Deep layer monsoonal moisture entrenched across large
areas of the Southwest and into the Great Basin will favor showers
and thunderstorms through this afternoon with locally high
rainfall rates. Scattered areas of flash flooding will be likely
which include potential impacts to burn scar locations.

DISCUSSION...The deeper layer subtropical ridge near the Four
Corners region remains in a conducive position to drive and
sustain the transport of monsoonal moisture up across southern and
eastern CA including the Sierra Nevada and adjacent areas of the
Great Basin. The latest CIRA-ALPW data shows moisture near or
above the 90th percentile of climatology in the 700/500 mb and
500/300 mb layers respectively, with the 12Z RAOB sounding at KREV
(Reno, NV) showing an impressive PW of 0.98 which is near a record
for the date.

This moisture coupled with placement of mid-level vort energy near
the western foothills of the central Sierra Nevada and modest
deeper upslope flow over the higher terrain will combine with
increasing boundary layer instability for scattered to eventually
broken areas of heavy shower and thunderstorm activity once again
for this afternoon. The latest GOES-W Day Cloud Phase RGB
satellite imagery along with LightningCast data suggests CI
(convective initiation) is imminent along the terrain of the
Sierra Nevada.

Convection is also expected to develop farther east across the
plateau areas of western NV to the east of the terrain where there
will also be a combination of orographics and diurnal heating
within this very moist monsoon pattern to support locally heavy
showers and thunderstorms.

Given the high moisture environment, rainfall rates up to 1.5
inches/hour will be possible, with some localized storm total
amounts by late this afternoon of 2 to 4 inches possible where any
cells tend to become more terrain-focused. Scattered areas of
flash flooding are likely going through this afternoon, and there
will be localized concerns for burn scar impacts.

Orrison

...Please see https://urldefense.com/v3/__http://www.wpc.ncep.noaa.gov__;!!= DZ3fjg!-chfZMgdqkkHXqNCzQafAo4wMaeKktUOQSGJ94k_fUZxLvJ6v_f_0PN5-O35REqj2g3Z= 3K0HPjRbfnc9Teb1D9pZIP4$ for graphic product...

ATTN...WFO...HNX...LKN...MFR...REV...STO...VEF...

ATTN...RFC...RSA...NWC...

LAT...LON 41782021 41451909 40421804 39771769 38961699=20
37921676 37261712 36391738 35751751 35501782=20
35421828 35891866 36621899 37781987 38842074=20
40212148 41362128=20

=3D =3D =3D
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AWUS01 KWNH 241904
FFGMPD
AZZ000-UTZ000-NVZ000-250103-

Mesoscale Precipitation Discussion 0992
NWS Weather Prediction Center College Park MD
304 PM EDT Sun Aug 24 2025

Areas affected...northwestern Arizona, southern Utah, and
southeastern Nevada

Concerning...Heavy rainfall...Flash flooding likely

Valid 241903Z - 250103Z

Summary...Scattered thunderstorms are quickly expanding in
coverage across the Colorado River Valley and vicinity. The
storms are in a favorable environment for localized rain rates
exceeding 1 inch per hour. Flash flooding is likely - especially
in terrain-favored areas and near burn scars.

Discussion...Recent satellite/lightning data indicates a distinct
increase in convective activity across terrain-favored ridgelines
in northwestern Arizona and south-central Utah over the past hour.
The storms are forming in response to 1) strong
insolation/destabilization across the area, with MLCAPE values
exceeding 1000 J/kg, 2) anomalously high moisture content (PW
values as high as 1.4 inch), and 3) very subtle mid-level
vorticity maxima rotating northward along the western periphery of
a stout mid/upper ridge near the Four Corners region. Wind fields
aloft were strong enough to favor slow northward storm motions
(around 10-15 knots). Despite these storm motions, localized
backbuilding (evident per radar/MRMS) and overall convective
intensity has still supported local instances of rain rates
reaching 1 inch/hr at times.

These rain rates should occur across locally sensitive ground
conditions resulting from several burn scars. Slot canyons in
southern Utah and vicinity area also at risk of locally heavy rain
rates. As convection continues to mature and expand in coverage,
several instances of flash flooding are expected.

Most of the convection should be diurnally driven, with model
guidance suggestive of flash flood potential existing through at
least 01Z/7p MDT.

Cook

...Please see https://urldefense.com/v3/__http://www.wpc.ncep.noaa.gov__;!!= DZ3fjg!4wTGC0DCHOW0D4pa35mAoBzjW8mKtcs0Th9B2gQwnpoNKsxWRuOw_12vfU808w1DB7Bn= yG5SPS2Y4ZHnRRycX2nSfXw$ for graphic product...

ATTN...WFO...FGZ...GJT...LKN...SLC...VEF...

ATTN...RFC...RSA...STR...NWC...

LAT...LON 39581229 39111117 37681086 37011072 35701114=20
34911127 34151232 34631405 35071456 36321543=20
37901527 39131400=20

=3D =3D =3D
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AWUS01 KWNH 241945
FFGMPD
COZ000-NMZ000-AZZ000-250045-

Mesoscale Precipitation Discussion 0993
NWS Weather Prediction Center College Park MD
345 PM EDT Sun Aug 24 2025

Areas affected...Southern CO...Northern NM

Concerning...Heavy rainfall...Flash flooding possible

Valid 241945Z - 250045Z

SUMMARY...Heavy showers and thunderstorms developing and expanding
in coverage across southern CO and northern NM will pose a threat
for isolated to scattered areas of flash flooding going into the
early evening hours. The area burn scar locations and normally dry
washes will be most susceptible to impacts.

DISCUSSION...Convective initiation is well underway across the
high country of southern CO and down into northern NM, with
locally heavy shower and thunderstorm activity in particular
beginning to focus over and near the Sangre De Cristo Range.

MLCAPE values along the CO/NM border have locally increased to
over 1000 J/kg and this coupled with deeper layer concentrations
of monsoonal moisture and orographic ascent near the terrain
should favor an additional expansion of convection over the next
several hours.

Facilitating some of the convective potential today will also be
proximity of a well-defined mid-level vort center over northwest
NM which should drift slowly off to the east over the next several
hours. This energy coupled with the orographic nature of the
convection may foster some smaller scale enhancement to the
convection with locally enhanced rainfall totals.

Rainfall rates of as much as 1 to 2 inches/hour are generally
expected with the stronger convective cells, and with relatively
slow cell-motions, there may be some totals by early this evening
of 2 to 3+ inches. These rains will foster concerns for isolated
to scattered areas of flash flooding, and primarily involving the
more sensitive burn scar locations and normally dry washes.

Orrison

...Please see https://urldefense.com/v3/__http://www.wpc.ncep.noaa.gov__;!!= DZ3fjg!9yF0FLyYFMlGe97an5m30LV4NHo2pw7X0zCWYuwPoVYlwxEIbZOU85ttYZTOBB_Jz9HO= d7bpl-XUAotofkyvlHriDSQ$ for graphic product...

ATTN...WFO...ABQ...FGZ...GJT...PUB...

ATTN...RFC...FWR...STR...TUA...NWC...

LAT...LON 38140516 37750444 36600454 35370516 34920608=20
34830704 34960828 35360889 35850909 36620910=20
36960875 37070724 37490622 37800571=20

=3D =3D =3D
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AWUS01 KWNH 242256
FFGMPD
NYZ000-PAZ000-250345-

Mesoscale Precipitation Discussion 0994
NWS Weather Prediction Center College Park MD
655 PM EDT Sun Aug 24 2025

Areas affected...Northern PA...Southern and Central NY

Concerning...Heavy rainfall...Flash flooding possible

Valid 242255Z - 250345Z

SUMMARY...A few bands of heavy showers and thunderstorms may be
capable of locally training over the same area this evening. This
coupled with high rainfall rates may yield at least an isolated
threat of flash flooding.

DISCUSSION...The latest surface analysis shows a cold front
gradually making progress into the northern Mid-Atlantic and
Northeast as an upper-level trough digs across the Great Lakes and
OH Valley. The airmass ahead of this cold front is moderately
unstable with MLCAPE values of 1000 to 1500 J/kg, and is
seasonably moist with PWs of 1.3 to 1.5 inches.

This coupled with some relatively strong moisture convergence
along the front and favorable upper-level forcing/divergence
should support multiple bands of rather heavy showers and
thunderstorms across portions of northern PA through southern and
central NY through this evening.

Radar imagery already shows a couple of linearly oriented bands
showing some organization and exhibiting some cell-training
characteristics across portions of southern NY. There is some
modest effective bulk shear in place that should tend to favor at
least some broken multicell bands of convection through
mid-evening until the cold front can advance more progressively
through the area.

Rainfall rates with the current activity are locally on the order
of 1 to 2 inches/hour, and the 18Z HREF along with recent HRRR
solutions suggest sufficient levels of cell-training to foster
some 2 to 4 inch rainfall totals through mid-evening.

These rains will foster concerns for some isolated areas of flash
flooding as a result.

Orrison

...Please see https://urldefense.com/v3/__http://www.wpc.ncep.noaa.gov__;!!= DZ3fjg!_W973_JMzr2W0xBo715b_hikk-hyKh6CcxGc2m1_OC5nL1xIT36LS76A2Q2lnV0tdW4B= rHoSgkGnels1PH3gjGQ9C4A$ for graphic product...

ATTN...WFO...ALY...BGM...BTV...BUF...CTP...

ATTN...RFC...RHA...TAR...NWC...

LAT...LON 43927422 43557384 42897442 42077568 41567649=20
41307740 41597771 42607664 43777503=20

=3D =3D =3D
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AWUS01 KWNH 242351
FFGMPD
TXZ000-OKZ000-KSZ000-COZ000-NMZ000-250550-

Mesoscale Precipitation Discussion 0995
NWS Weather Prediction Center College Park MD
750 PM EDT Sun Aug 24 2025

Areas affected...Central to Southeast CO...Far Northeast
NM...Southwest KS...OK/TX Panhandles

Concerning...Heavy rainfall...Flash flooding possible

Valid 242350Z - 250550Z

SUMMARY...Clusters of heavy showers and thunderstorms will likely
grow upscale with time this evening across portions of the central
High Plains. Cell-merger activity and locally high rainfall rates
will pose a threat for isolated to scattered areas of flash
flooding.

DISCUSSION...The late-day GOES-E IR satellite imagery shows
clusters of cold-topped convection continuing to evolve over
central to southeast CO and down through far northeast NM as
moist/convergent and unstable low-level flow focuses along a
quasi-stationary front draped from the OK/TX Panhandles
northwestward into the eastern slopes of the central Rockies.

MLCAPE values along the front are as high as 1500 to 2500 J/kg
with locally 50+ kts of effective bulk shear in place helping to
favor concentrations of multicell and supercell convection. The
airmass is anomalously moist with at least some of the mid and
high-level monsoonal moisture over the Southwest advancing east
around the north side of the Four Corners subtropical ridge axis.
This is helping to favor PW anomalies of 2+ standard deviations
above normal.

Weak embedded shortwave energy within the mid-level west-northwest
flow over the central Rockies will eject east-southeast across
eastern CO and eventually portions of southwest KS and the OK/TX
Panhandles going into the overnight hours. This energy interacting
with the favorable thermodynamic environment and the front should
support an upscale grow of convection with time across the central
High Plains.

The experimental WoFS guidance along with the 18Z HREF suggest
areas of southeast CO and eventually portions of the OK/TX
Panhandles will tend to be the primary focus for more organized
convection and heavier rainfall totals at least through the
midnight time frame. This is also in close proximity to where
stronger frontal convergence and greater instability will be.

Rainfall rates of up to 2 inches/hour are expected with the
stronger supercell mode convective cells and with any cell-mergers
that occur over the next several hours. Going through midnight,
the high rainfall rates and localized cell-mergers may foster some
rainfall amounts of 3 to 4+ inches. This will drive a threat for
isolated to scattered areas of flash flooding.

Orrison

...Please see https://urldefense.com/v3/__http://www.wpc.ncep.noaa.gov__;!!= DZ3fjg!7OTY4HD50DL9C6HFPDpsl9dpddL-qCaVcc7ujN4BmCefqLcx4rQGMoFQJltemQhek4ti= vqeT2EsyxZpbqkmzCTFAfFk$ for graphic product...

ATTN...WFO...ABQ...AMA...BOU...DDC...GLD...OUN...PUB...

ATTN...RFC...FWR...KRF...TUA...NWC...

LAT...LON 39690506 39580366 38720198 37800069 36409907=20
35389969 35480177 36530430 37810555 39140571=20 =20=20=20=20=20=20=20=20=20=20=20=20

=3D =3D =3D
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AWUS01 KWNH 250032
FFGMPD
NVZ000-CAZ000-ORZ000-250600-

Mesoscale Precipitation Discussion 0996
NWS Weather Prediction Center College Park MD
831 PM EDT Sun Aug 24 2025

Areas affected...Sierra Nevada...Western and Central NV

Concerning...Heavy rainfall...Flash flooding likely

Valid 250030Z - 250600Z

SUMMARY...Monsoonal showers and thunderstorms will continue
through the evening hours across the Sierra Nevada and portions of
the Great Basin. Additional areas of flash flooding will still be
likely with localized burn scar impacts still a concern over the
next few hours.

DISCUSSION...The late-day visible satellite imagery shows an
expansive area of monsoonal showers and thunderstorms impacting
the Sierra Nevada and interior portions of the Great Basin
including central and western NV.

A fair amount of surface-based instability remains in place across
central NV in particular, with an axis of instability extending
westward back into the northern Sierra Nevada. SBCAPE values are
on the order of 1000 to 2000+ J/kg, and there are some 3-hour
SBCAPE differentials across central NV of +800 to +1000 J/kg which
suggests that there are corridors of untapped instability that
will help sustain the ongoing convective threat for at least a few
more hours.

Deep monsoonal moisture remains in place as evidenced by the
latest CIRA-ALPW data which shows significant concentrations of
moisture in the mid to upper levels of the vertical column. The
00Z RAOB sounding from KREV depicted a PW of 0.96 which is again
near a daily record.

This moisture and instability coupled with upslope flow into the
terrain along with localized outflow boundary collisions over the
plateau areas of central and western NV favor clusters of
monsoonal convection persisting through the evening hours.

Given the high moisture environment, rainfall rates up to 1.5
inches/hour will still be possible, with some additional isolated
rainfall amounts of 2 to 3 inches possible which is supported by
recent runs of the experimental WoFS guidance. Generally these
additional rains are likely to foster some additional scattered
areas of flash flooding over the next few hours, and there will
continue to be concerns for localized burn scar impacts.

Orrison

...Please see https://urldefense.com/v3/__http://www.wpc.ncep.noaa.gov__;!!= DZ3fjg!6nixlvhIh_I9jdS5427KRxaRq7kuX1VCkuKYunDEDak_uiH_xxLUbjJCLFgMieSFnEYN= fADW2bw8vIMgwXfOvgvT0Sk$ for graphic product...

ATTN...WFO...EKA...HNX...LKN...MFR...REV...STO...VEF...

ATTN...RFC...RSA...STR...NWC...

LAT...LON 42022197 41862065 40971920 40761788 40971643=20
40831473 40151416 39351460 38141624 37101747=20
36721851 37021921 37641975 38442030 39622075=20
39862096 40302126 40892193 41132253 41122298=20
41502321 41922278=20

=3D =3D =3D
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AWUS01 KWNH 250101
FFGMPD
AZZ000-UTZ000-NVZ000-250600-

Mesoscale Precipitation Discussion 0997
NWS Weather Prediction Center College Park MD
900 PM EDT Sun Aug 24 2025

Areas affected...Southern UT...Central and Northern AZ

Concerning...Heavy rainfall...Flash flooding possible

Valid 250100Z - 250600Z

SUMMARY...Additional scattered areas of flash flooding will remain
possible going through the evening hours from clusters of
monsoonal showers and thunderstorms.

DISCUSSION...The late-day GOES-W IR satellite imagery in
conjunction with radar continues to show broken clusters of
monsoonal showers and thunderstorms impacting portions of central
and northern AZ and southern UT. The activity continues to be
embedded within a moist and unstable airmass being facilitated by
the synoptic scale monsoon pattern across the Southwest.

There are still some pockets of untapped instability locally over
northwest AZ and southern UT with some MLCAPE values of 1000+ J/kg
noted. However, the region is gradually being convectively
overturned, and this should support a gradual downward trend in
the coverage and intensity of convection by later this evening.
This is also being advertised by recent runs of the experimental
WoFS and the broader hires model consensus.

Regardless, the ongoing clusters of convection will still be
capable of producing heavy rainfall rates of up to 1.5 inches/hour
over the next few hours, with some additional spotty amounts of up
to 2 inches going through late this evening.

Some additional scattered areas of flash flooding will be
possible, and this will include localized impacts potentially to
the slot canyon areas of southern UT and some of the sensitive
burn scar areas over central and especially northern AZ. Some of
the normally dry washes may also be affected by suddenly rising
flood waters.

Orrison

...Please see https://urldefense.com/v3/__http://www.wpc.ncep.noaa.gov__;!!= DZ3fjg!9BwtiKiUnflZXZN7PlKn3_pBaT2_EzRGHlrgjSEDeoAwPsH80DYOET-_Z8I1TDLToz0I= _HrCA4MMvs-JcRd1ZFhLkf4$ for graphic product...

ATTN...WFO...FGZ...GJT...PSR...SLC...VEF...

ATTN...RFC...STR...NWC...

LAT...LON 38371264 38371099 37450984 36150943 34330968=20
33321093 33291241 33791347 34691396 35861411=20
36771404 37991351=20

=3D =3D =3D
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AWUS01 KWNH 250636
FFGMPD
TXZ000-OKZ000-KSZ000-NEZ000-COZ000-251200-

Mesoscale Precipitation Discussion 0998
NWS Weather Prediction Center College Park MD
235 AM EDT Mon Aug 25 2025

Areas affected...much of west-central KS into adjacent portions of
CO/NE/OK

Concerning...Heavy rainfall...Flash flooding possible

Valid 250635Z - 251200Z

Summary...Training showers and thunderstorms likely to result in
localized 3"+ rainfall totals, isolated to scattered instances of
flash flooding.

Discussion...Convection has proliferated over the past couple of
hours across portions of the western Central Plains, tapping into
elevated instability with cloud bases in the vicinity of 850-700
mb. While MUCAPE generally ranges from 250-750 J/kg (per SPC
mesoanalysis), there is likely compensation from slantwise
instability as isentropic upglide along the 305K surface has
increased significantly with the veering low-level jet over the
past several hours (with southwesterly flow of 15-20 kts becoming
oriented perpendicular to isobars). The mesoscale environment is
otherwise characterized highly anomalous tropospheric moisture
content (PWs of 1.3-1.8 inches, between the 90th percentile and
max moving average, per LBF and DDC sounding climatology) and deep
layer (0-6 km) shear of 20-40 kts (on the periphery of the
right-entrance region of a ~120 kt jet streak over the Mid-MS
Valley within northwest flow and embedded shortwave/vorticity
maxima in the mid-levels).

While soils are relatively dry across the region (per NASA
SPoRT-LIS soil moisture in the 0-1m layer generally at or below
the 10th percentile), too much rainfall too quickly could lead to
instances of flash flooding through the overnight. Localized
training and repeating of cells are possible across all of the
highlighted region, as northwest flow directs backbuilding
convection from northwest to southeast over many of the same
localities. Hi-res models (00z HREF suite) indicate the greatest
odds for localized 3"+ totals (40-km neighborhood probs for 3"
exceedance of 40-60%) in the vicinity of Dodge City, KS and points
east and southeast, where instability is maximized (MUCAPE 500+
J/kg) and the greatest coverage of convective cells are already
occurring. As 6-hr FFGs (Flash Flood Guidance) are locally as low
as 2.0" in this area (with the bulk of the region near or below
3.0"), isolated to scattered instances of flash flooding are
considered likely.

Churchill

...Please see https://urldefense.com/v3/__http://www.wpc.ncep.noaa.gov__;!!= DZ3fjg!6WaEPkqWcssgTag046hZMqGzfOjbjyU1C1Ax20MiPM3m1rQNZ-pHqKdQG1Rn3OtPODel= kjcoDmvtb5ZAtcotb9dM9JM$ for graphic product...

ATTN...WFO...AMA...BOU...DDC...GID...GLD...ICT...LBF...OUN...

ATTN...RFC...KRF...TUA...NWC...

LAT...LON 40640209 40520109 40000016 39239901 38059828=20
37039741 36169756 35949847 36169951 36580016=20
37260083 38480145 39160248 39660322 40110344=20
40500323=20

=3D =3D =3D
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AWUS01 KWNH 251725
FFGMPD
AZZ000-CAZ000-252330-

Mesoscale Precipitation Discussion 0999
NWS Weather Prediction Center College Park MD
124 PM EDT Mon Aug 25 2025

Areas affected...Southern Arizona...

Concerning...Heavy rainfall...Flash flooding possible

Valid 251730Z - 252330Z

SUMMARY...Monsoon convection with rates up to 2"/hr. Localized
1.5-2.5" pose possible widely-scattered localized flash flooding.

DISCUSSION...A compact but atypically strong retrograding
shortwave can be seen well in composite RADAR mosaic near Blythe
starting to turn more northerly across the Lower Colorado Valley.
The associated debris clouds will hamper insolation to build
instability, however, the upwind areas over the Sonoran Desert has
received solid insolation with anomalous moisture remaining across
southern AZ. Surface Tds in the low to mid-60s combined with core
of CIRA LPW up to 700mb, extends through much of southern AZ as
well, with only mid-level drying at 700-500mb layer directly south
of the boarder; providing enhanced buoyancy with CAPEs already
building over 2000 J/kg, on their way to 2500-3000 J/kg with
limited capping. Total PWats of 1.75" are above normal, about
1.5-2 standard anomalies and being loaded mainly near cloud base
(and below) should allow for solid efficiency.

GOES Visible imagery shows, low level convergence along the upwind
edge of outer band of the MCV is producing thunderstorms, that had
been weaker, but with influx of increasingly unstable air from the
desert, are starting to deepen and broaden. Low level flow is
still responding to the exiting MCV and broader upglide into the
strong divergence aloft from the expanding right entrance to the
50+kt 3H jet streak across S NV/SE CA, as such, back-building
(upwind propagation) may maintain for a few more hours allowing
for effective slow cell motions increasing totals up to 2".

Through the late morning/early afternoon, as the MCV exits, winds
are expected to further strengthen with westerly upslope
components across southeast AZ terrain across Cochise, SE Pima and
S Graham counties. Vigor of low level upslope is likely to
significantly increase toward/after 21z, with 15-20kts of westerly
flow at 850mb. Peak heating/updraft strength and flux into the
terrain, rates should increase to 1.5"/hr with some 2"/hr rates
peaking toward 22-00z. Probabilities/Hi-Res CAM suite suggest
best overall cells are likely to be along and just north of the
US/Mexico border with a spot or two of 1.5-2.5" totals. With a
bulk of the rain occurring in sub-hourly bursts and hard ground
conditions, increased run-off suggest widely-scattered incidents
of flash flooding are possible into the early evening.

Gallina

...Please see https://urldefense.com/v3/__http://www.wpc.ncep.noaa.gov__;!!= DZ3fjg!8HObKstHlnYfdGf5gVZMB6GcnHye6stn_-6pmLbaY-nN5YWhtre8o-uGlFf4ohSB6T2g= -royNrvDuHby_XxCYQO3TgU$ for graphic product...

ATTN...WFO...PSR...TWC...

ATTN...RFC...STR...NWC...

LAT...LON 33981380 33801324 33001185 33221030 32611001=20
31641000 31251023 31231108 31591220 31871308=20
32511428 32941465 33401478 33821434=20

=3D =3D =3D
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AWUS01 KWNH 251941
FFGMPD
COZ000-NMZ000-WYZ000-AZZ000-UTZ000-260140-

Mesoscale Precipitation Discussion 1000
NWS Weather Prediction Center College Park MD
340 PM EDT Mon Aug 25 2025

Areas affected...Central and Southern CO...Northern and Central
NM...Far Northeast AZ...Far Southeast UT

Concerning...Heavy rainfall...Flash flooding likely

Valid 251940Z - 260140Z

SUMMARY...Showers and thunderstorms will develop and expand in
coverage going through the afternoon hours over portions of the
central Rockies and adjacent areas of the CO/NM High Plains.
Scattered areas of flash flooding are likely.

DISCUSSION...The midday GOES-E visible satellite imagery shows
convective initiation well underway across portions of central and
southern CO down through areas of northern and central NM. Strong
diurnal heating continues to foster the build-up of surface-based
instability which is resulting in the development of differential
heating boundaries and terrain-focused circulations.

MLCAPE values have already risen to 500 to 1000+ J/kg with a
rather moist environment characterized by PWs of 1.5+ standard
deviations above normal. This coupled with the aforementioned
orographics and arrival of weak mid-level vort energy embedded
within the deeper layer west-northwest flow aloft should favor a
notable expansion of convection over the next several hours across
the higher terrain and also into adjacent areas of the High Plains.

Moist and increasingly unstable low-level upslope flow along with
focused convergence along a stationary front near the Front Range
on down to the eastern slopes of the Sangre De Cristo Range will
be a key facilitator for convection across these areas to become
locally focused by later this afternoon. In fact, surface dew
points across eastern CO and northeast NM range from the mid 50s
to the low 60s, and this moisture along with the deep layer
environment should foster convection with efficiently high
rainfall rates that may reach 2+ inches/hour. Localized upslope
flow over the terrain will also support these high rainfall rates.

Going through late this afternoon, expect sufficient convective
organization for some rainfall totals to reach as high as 2 to 4
inches. These rains will drive an elevated threat for at least
scattered areas of flash flooding which will include concerns for
localized burn scar impacts. Some areas of southern CO and
northern NM have been rather wet recently, and these antecedent
conditions may favor locally enhanced runoff concerns.

Orrison

...Please see https://urldefense.com/v3/__http://www.wpc.ncep.noaa.gov__;!!= DZ3fjg!4imk3B1q2LkgxPhHbP_G6Lq9LdWhlXOgeAxE71DECaxWVS4BJp7kP9srfpHaRvQwoYo-= DK27J_cuucVLbj-t9mbSbb8$ for graphic product...

ATTN...WFO...ABQ...BOU...CYS...FGZ...GJT...PUB...

ATTN...RFC...FWR...KRF...STR...TUA...NWC...

LAT...LON 41120512 40740404 39590339 37750353 35990400=20
34980485 34550592 34440713 34700835 35410926=20
36590984 37800959 38210835 38200663 39160585=20
40750593=20

=3D =3D =3D
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AWUS01 KWNH 252009
FFGMPD
NVZ000-CAZ000-260208-

Mesoscale Precipitation Discussion 1001
NWS Weather Prediction Center College Park MD
408 PM EDT Mon Aug 25 2025

Areas affected...Sierra Nevada...Southern CA

Concerning...Heavy rainfall...Flash flooding likely

Valid 252008Z - 260208Z

SUMMARY...Scattered thunderstorms with heavy rainfall rates are
likely through this afternoon across portions of the Peninsular
Range of southern CA, and also into the central and southern
Sierra Nevada. Scattered areas of flash flooding are likely, and
this may include a threat for burn scar flash flooding and debris
flow activity.

DISCUSSION...The early afternoon GOES-W Day Cloud Phase RGB
satellite imagery shows convective initiation underway across the
higher terrain of the Peninsular Range of southern CA and also up
across the central and southern Sierra Nevada. Daytime heating and
the build of surface-based instability along and adjacent the
terrain is fostering favorable differential heating boundary and terrain-enhanced circulations/ascent for convection which should
generally expand in coverage over the next several hours.

Monsoonal moisture remains quite prevalent and especially in the
850/500 mb layer based on the latest CIRA-ALPW data. This is
helping to drive PW anomalies again that are 1.5 to 2.5 standard
deviations above normal. This moisture along with the increasing
instability and orographic footprint of the convection should
yield rainfall rates this afternoon reaching as high as 1.5 to 2
inches/hour, with some of the heaviest rates probably focused over
the Peninsular Range of southern CA where moisture here is a tad
deeper (noting the 500/300 mb layer) relative to areas farther
north. Also, there is some very moist low-level southeast flow off
of the northern Gulf of California playing a role here in driving
greater nearby instability.

The convection today should again follow the diurnal heating
cycle, and by late today, some spotty rainfall amounts of 2 to 4
inches will be possible. This is supported locally by the latest
experimental WoFS guidance, and especially over the Peninsular
Range. Given the sensitivities with localized burn scar areas and
the rugged terrain in general, scattered areas of flash flooding
are likely. Some debris flow activity will be possible where any
burn scar flash flooding occurs.

Orrison

...Please see https://urldefense.com/v3/__http://www.wpc.ncep.noaa.gov__;!!= DZ3fjg!4ndsX6KA9fEXjpy0wdelhQQz5tqrzimNfEaoVjf97bEyQm3PQrit_tXPEeD8qz5kZXqZ= mrIcsIrA4pRFv1MUuipHEN0$ for graphic product...

ATTN...WFO...HNX...LOX...PSR...REV...SGX...STO...VEF...

ATTN...RFC...RSA...NWC...

LAT...LON 39441960 38271829 36641772 35181763 34091633=20
32511581 32361649 33041699 33451730 34271799=20
34491839 34811881 34981884 35391887 36041883=20
36871906 37631967 38742031 39392040=20

=3D =3D =3D
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AWUS01 KWNH 252037
FFGMPD
AZZ000-UTZ000-NVZ000-260235-

Mesoscale Precipitation Discussion 1002
NWS Weather Prediction Center College Park MD
436 PM EDT Mon Aug 25 2025

Areas affected...Southern NV...Southern UT...Central and Northern
AZ

Concerning...Heavy rainfall...Flash flooding possible

Valid 252035Z - 260235Z

SUMMARY...Monsoonal showers and thunderstorms will continue to
develop and locally expand in coverage over the next several
hours. Mainly isolated areas of flash flooding will be possible.

DISCUSSION...The early afternoon GOES-W visible satellite imagery
shows monsoonal shower and thunderstorm activity initiating and
expanding in coverage across northern AZ into southern NV and
southern UT. MLCAPE values have increased to as much as 1000+ J/kg
and the PW environment remains quite moist with values running 1
to 2 standard deviations above normal.

An additional uptick in instability is expected over the next few
hours which should work in tandem with orographics to drive an
increase in the coverage of showers and thunderstorms. The
convection will be capable of producing high rainfall rates of up
to 1.5 inches/hour.

The latest RAP guidance shows an increasing amount of mid-level
southeast flow over central to northwest AZ and by later today
around the western flank of the mid-level subtropical ridge/high
centered along the AZ/NM border. Some effective bulk shear values
may reach as high as 30 to 40+ kts which may support some
organized convective structures in time that will further support
high rainfall rates with enhanced updrafts, but also localized
areas of convective sustenance/persistence near areas of higher
terrain and including the Mogollon Rim.

Some localized 2 to 3+ inch rainfall amounts will be possible, and
this will favor a threat for at least isolated areas of flash
flooding going through the afternoon and early evening hours. Slot
canyon and burn scar flash flooding impacts will be associated
with this threat.

Orrison

...Please see https://urldefense.com/v3/__http://www.wpc.ncep.noaa.gov__;!!= DZ3fjg!_6UrYYzzMV4wXzh-OCvNO05LJPNUBUksnlOX0bw1zxCRsg4AfJSKHNEnulSQNpjlDCM5= EiiYIjgxBLjGSM_dBiDMrOw$ for graphic product...

ATTN...WFO...FGZ...LKN...SLC...VEF...

ATTN...RFC...RSA...STR...NWC...

LAT...LON 39131105 38541061 36681097 35611074 34901014=20
34351027 34131095 34411197 35601347 36101538=20
36681620 38001616 38711532 38911365 38781251=20 =20=20=20=20=20=20=20=20=20=20=20=20

=3D =3D =3D
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AWUS01 KWNH 252146
FFGMPD
AZZ000-CAZ000-260145-

Mesoscale Precipitation Discussion 1003
NWS Weather Prediction Center College Park MD
545 PM EDT Mon Aug 25 2025

Areas affected...Southern CA...Southwest to South-Central AZ

Concerning...Heavy rainfall...Flash flooding likely

Valid 252145Z - 260145Z

SUMMARY...Locally very heavy monsoon-driven showers and
thunderstorms are expected going through the remainder of the
afternoon across southern CA into southwest and south-central AZ.
Scattered areas of flash flooding are likely, some of which may be
locally significant.

DISCUSSION...The mid-afternoon GOES-W VIS/IR satellite imagery
shows deepening and cooling convective tops across southeast CA
and into adjacent areas of southern AZ where radar is confirming
multiple concentrated bands of very heavy shower and thunderstorm
activity.

Mesoscale boundary forcings/interactions along with terrain
influence and proximity of a very moist and unstable airmass is
expected to drive corridors of additional convection with high
rainfall rates going into the evening hours. MLCAPE values of 1500
to 2500 J/kg are noted with recent CIN erosion helping to yield
the recent uptick and organization of convection across southern
CA and southern AZ. This includes the Peninsular Range and the
adjacent deserts off to the east and south.

Given the level of focused instability over the region with PWs
reaching nearly 2.5 standard deviations above normal (with support
from the very warm nearby Gulf of California), some rainfall rates
may reach 2 to 2.5 inches/hour, with some spotty storm totals over
the next few hours of 3 to 4+ inches. Recent WoFS guidance output
suggests this potential, which will be aided by some localized
cell-merger activity.

Additional areas of flash flooding will be likely, some of which
may be locally significant near areas of higher terrain and also
for the dry wash/arroyo locations near and away from active areas
of heavy shower and thunderstorm activity.

Orrison

...Please see https://urldefense.com/v3/__http://www.wpc.ncep.noaa.gov__;!!= DZ3fjg!7vkAaj75rcrt-PIafMfdv1fVW3ZEAJXG763nWXhF9O2-b5Z22oJsCgvTPWRZV_AGO3EW= JGgmSXtpxO1OjwL-sJcN_vA$ for graphic product...

ATTN...WFO...PSR...SGX...TWC...VEF...

ATTN...RFC...RSA...STR...NWC...

LAT...LON 34681677 34481604 33611488 33431359 33201277=20
33111094 32761015 31791014 31241072 31481240=20
32001378 32321480 32411608 32861673 33841716=20
34521716=20

=3D =3D =3D
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AWUS01 KWNH 260111
FFGMPD
AZZ000-NVZ000-CAZ000-260600-

Mesoscale Precipitation Discussion 1004
NWS Weather Prediction Center College Park MD
910 PM EDT Mon Aug 25 2025

Areas affected...Southern and Eastern CA...Western and Southern AZ

Concerning...Heavy rainfall...Flash flooding likely

Valid 260110Z - 260600Z

SUMMARY...Additional areas of flash flooding will be likely going
through the evening hours across portions of southern and eastern
CA through western and central AZ.

DISCUSSION...The late-day GOES-W IR satellite imagery shows an
extensive convective cloud canopy over areas of southern and
eastern CA into western and central AZ. Very heavy showers and
thunderstorms continue to locally percolate across the region in
response to localized outflow boundary collisions and some
orographically focused ascent.

Diurnally driven instability continues to be gradually consumed
via the process of convective overturning, but MLCAPE values
remain locally over 1000 J/kg across some of the open desert areas
of eastern CA and also through central AZ with much of this area
so far escaping much of the convective activity.

Recent runs of the experimental WoFS suggest some additional focus
for mesoscale-driven shower and thunderstorm activity across
central AZ in particular which may be aided by close proximity of
some mid-level vort energy lifting northwestward out of the far
northern Gulf of California.

There is also a belt of relatively stronger effective bulk shear
lifting up across southern and central AZ around the western side
of the subtropical ridge off to the east. This shear and the
lingering instability with generally moist deep layer southeast
monsoonal flow will likely support convection lingering well into
the evening.

Rainfall rates will continue to be capable of reaching up to 1.5
inches/hour with the stronger convective cores, with some
additional spotty totals of 2 to 3 inches possible. The 90th
percentile 6-hour QPF from 00Z WoFS supports this over parts of
central and southwest AZ.

This will continue to promote isolated to scattered areas of flash
flooding through this evening before the convection gradually
weakens. Any burn scar locations and the normally dry washes will
continue to be most susceptible to impacts.

Orrison

...Please see https://urldefense.com/v3/__http://www.wpc.ncep.noaa.gov__;!!= DZ3fjg!9--6CKs_-_lYZCLU7KMZAHifHRWpc2GOFL6JGPBpgoiQTrScsha74K5421HW9LeKLvGB= wTnDG-GyDAvrDDq_Ybxelho$ for graphic product...

ATTN...WFO...FGZ...HNX...LOX...PSR...SGX...TWC...VEF...

ATTN...RFC...RSA...STR...NWC...

LAT...LON 36671703 35421529 35601313 35541191 35241105=20
34731033 33951015 33091063 32361180 32151283=20
32281408 32571515 33061606 33641703 34921774=20
36511781=20

=3D =3D =3D
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AWUS01 KWNH 260159
FFGMPD
TXZ000-OKZ000-COZ000-NMZ000-260757-

Mesoscale Precipitation Discussion 1005
NWS Weather Prediction Center College Park MD
957 PM EDT Mon Aug 25 2025

Areas affected...Central and Southern CO...Central and Northern
NM...TX Panhandle

Concerning...Heavy rainfall...Flash flooding likely

Valid 260157Z - 260757Z

SUMMARY...Showers and thunderstorms will continue to develop and
concentrate across portions of central and southern CO into
northern and central NM. This will especially include the higher
terrain of the Sangre De Cristo Range and adjacent areas of the
High Plains. Scattered to numerous areas of flash flooding are
expected tonight.

DISCUSSION...The early evening GOES-E IR satellite imagery shows
an expansive area of very cold-topped convection impacting areas
of southern CO and especially central to northeast NM as heavy
showers and thunderstorms interact with the higher terrain of the
Sangre De Cristo Range along with favorable upslope flow.

A corridor of MLCAPE values reaching 500 to 1000+ J/kg continue to
be focused over north-central and northeast NM, with a separate
axis of instability also still seen over parts of southeast CO.
The environment remains very moist with PWs near 2 standard
deviations above normal. This coupled with highly favorable
orographic forcing/ascent and subtle mid-level vort energy
dropping southeast across the central Rockies should favor
additional concentrated areas of heavy showers and thunderstorms
over the next several hours.

The recent satellite and radar trends along with the last several
runs of the experimental WoFS guidance would suggest northeast NM
will be the primary focus for the heaviest rainfall amounts. This
is where more favorable easterly low-level upslope flow into the
terrain along with interaction with a stationary front will be
noted. Greater instability in this area too should tend favor this
area seeing the heaviest rainfall rates which is further supported
by some of the very cold convective cloud tops currently over the
region.

Rainfall rates with the stronger storms may be capable of reaching
2 inches/hour, and with the persistent upslope flow and frontal
convergence, some additional rainfall totals of 3 to 5 inches will
be possible. By later in the night, some of these heavier rains
over northeast NM should begin to edge out into the TX Panhandle
area which is strongly supported by the latest WoFS guidance.

Scattered to numerous areas of flash flooding are generally
expected, and especially over northeast NM where the heaviest
totals should focus. Some locally significant impacts cannot be
ruled out which may locally include sensitive burn scar locations.

Orrison

...Please see https://urldefense.com/v3/__http://www.wpc.ncep.noaa.gov__;!!= DZ3fjg!57uYAAIHBw_igN2z_cY9bvwL-kp0N83T1IorXzGeoUX7BSi49Mlolm9b_jQcNijREk9W= nSyuLqmd9TPFr_wfGMwHztk$ for graphic product...

ATTN...WFO...ABQ...AMA...BOU...GJT...LUB...PUB...

ATTN...RFC...FWR...KRF...STR...TUA...NWC...

LAT...LON 39300478 38880387 38250352 36830313 36120235=20
35730073 35120039 34490124 34360351 34060485=20
34120636 34430722 35260750 36450676 37490671=20
38540640 39150583=20

=3D =3D =3D
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AWUS01 KWNH 261455
FFGMPD
CAZ000-261850-

Mesoscale Precipitation Discussion 1006
NWS Weather Prediction Center College Park MD
1054 AM EDT Tue Aug 26 2025

Areas affected...San Joaquin Valley into Sierra Nevada foothills

Concerning...Heavy rainfall...Flash flooding likely

Valid 261450Z - 261850Z

SUMMARY...Slow moving thunderstorms will pose a threat for
isolated flash flooding across portions of the San Joaquin Valley
into the Sierra Nevada foothills over the next 2-4 hours. Rainfall
rates of 1-2 in/hr will be possible.

DISCUSSION...GOES West infrared satellite imagery and GLM data
showed scattered thunderstorms expanding in coverage over the San
Joaquin Valley and Sierra Nevada foothills as of 1430Z, within
about 50 miles of Madera. Cells were located along a weak
mid-level shear axis inferred on water vapor imagery, emanating
from a vorticity maximum over west-central NV. The storms were
likely elevated in nature, rooted just above 700 mb given RAP
analysis point soundings, within a small region of weak
instability ranging from 250 to just over 500 J/kg (via 14Z
RAP/SPC mesoanalysis). Precipitable water values were very
anomalous across central CA with standardized anomalies of 2 to 3+
according to 12Z area soundings and short term GFS forecasts.

With RAP-derived LFC-EL layer winds averaging near 5 kt, cell
motions have been slow and MRMS-derived rainfall rates have been
1-2 in/hr over portions of Fresno and Madera counties. Scattered
thunderstorms are expected to continue over the next few hours but
due to a lack of stronger winds aloft, storm organization should
remain poor and new cell development will be aided by thunderstorm
outflows. Localized flash flooding will remain possible over the
next 2-4 hours. Trends will be monitored for updates as needed
with the onset of better surface heating and turbulent mixing
within the boundary layer potentially disrupting ongoing activity.

Otto

...Please see https://urldefense.com/v3/__http://www.wpc.ncep.noaa.gov__;!!= DZ3fjg!8sfJDnoD6T2oMTfFWM8mVKZEd0QpDHKC1kOgY7cujgR-4eFyevQO7XgMIUZFqEULC3Vx= CasgZXSdzkQ61BPG6-5h_Po$ for graphic product...

ATTN...WFO...HNX...STO...

ATTN...RFC...RSA...NWC...

LAT...LON 38222076 37642001 37131943 36481908 36121922=20
35971958 36071985 36692046 37222088 37862113=20 =20=20=20=20=20=20=20=20=20=20=20=20

=3D =3D =3D
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AWUS01 KWNH 261818
FFGMPD
NVZ000-CAZ000-270000-

Mesoscale Precipitation Discussion 1007
NWS Weather Prediction Center College Park MD
218 PM EDT Tue Aug 26 2025

Areas affected...eastern CA/western NV

Concerning...Heavy rainfall...Flash flooding possible

Valid 261816Z - 270000Z

SUMMARY...Scattered thunderstorms are expected to develop along
the Sierra Nevada through 21Z, some of which may produce flash
flooding due to slow movement. Stronger cells will be capable of
generating 1-2 in/hr rainfall rates.

DISCUSSION...GOES West visible satellite imagery showed the
development of cumulus and early stages of convective initiation
along portions of the central and southern Sierra Nevada at 18Z.
Despite some remnant cloud cover, the beginning of peak heating
atop the elevated heat source was coinciding with anomalous
tropospheric moisture (90th to 95th percentile for late August).
The region of eastern CA/western NV was situated between a low to
mid-level low offshore of the CA coast and low/trough extending
from eastern OR into central NV. Between these two features was a
section of relatively weak 0-6 km AGL layer winds of 5 to 10 kt
which should contribute to slow storm motions.

Continued heating should lead to the development of 500-1000 J/kg
of instability across the region by mid-afternoon. Thunderstorm
coverage will likely continue to expand over the next few hours
with peak coverage in the 21-00Z time frame. Limited shear should
keep storms disorganized in nature but slow movement and
mesoscale/terrain interactions may allow for a few cells to
exhibit little movement over the course of an hour or two before
subsequent outflow initiates development downstream. Convection
may move into valley locations later in the period. Due to the
moist environment, rainfall rates of 1-2 in/hr (or less than an
hour) will be possible. In addition to overlapping with locations
that have received heavy rainfall over the past 3 days, these high
rates will pose an increased flash flood threat along burn scars,
urban locations or other areas of poor drainage, including the
potential for debris flows in and around sensitive terrain.

Otto

...Please see https://urldefense.com/v3/__http://www.wpc.ncep.noaa.gov__;!!= DZ3fjg!884UoJRx-SHbHd-iWAl7AZXOJzMYgmU3TEb-Ntl8fVjl7oR4HHAN4ovVHaZ-_dUkrmpl= eda8Wca-Of8dPpkj1yCR13o$ for graphic product...

ATTN...WFO...HNX...REV...STO...VEF...

ATTN...RFC...RSA...NWC...

LAT...LON 39501976 39211916 38491843 37661772 36951705=20
36151659 35671668 35441727 35421808 35571862=20
36231878 36731900 37481984 38442031 39302048=20 =20=20=20=20=20=20=20=20=20=20=20=20

=3D =3D =3D
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AWUS01 KWNH 261839
FFGMPD
WYZ000-UTZ000-IDZ000-NVZ000-270030-

Mesoscale Precipitation Discussion 1008
NWS Weather Prediction Center College Park MD
238 PM EDT Tue Aug 26 2025

Areas affected...Southern ID...Northeast NV...Northern
UT...Western WY...-

Concerning...Heavy rainfall...Flash flooding possible

Valid 261840Z - 270030Z

SUMMARY...Highly anomalous moisture and strong dynamic forcing
should allow for scattered to numerous thunderstorms capable of 1"
rates & 1-2" localized totals. Favorable environment for
redevelopment may allow for some repeating cells/tracks which will
further enhance scattered incidents of flash flooding through
evening.

DISCUSSION...GOES WV mosaic suite depicts a very broad upper-level
trough with some subtle WNW to SE negative tilting lifting
northward across central NV with the core near central Nye county
with broad downstream highly diffluent environment expanding
across N NV, S ID into W WY/N UT providing areas of enhanced mid
to upper-level cloudiness. This is greater near the core of the
DPVA; allowing for better filtrated insolation further downstream
across the ID/NV border, increasing heating. The bigger concern
is seasonally near record moisture and flux streaming through the
Great Basin, providing higher low level theta-E air with Tds in
the mid to upper 50s in higher plateaus of NV and UT and even some
low 60s near the southern portions of the Snake River Plain.=20
While the filtered sunlight has some limitations for surface
temperatures, the areas that have best clearing are already seeing
convective development given limiting capping environments and
strong DPVA and divergence aloft with large scale broad ascent
pattern. MUCAPEs of 750-1250 J/kg have been increasing as the
deep layer moisture reaches 1-1.25" total moisture (with a few 12z
RAOBs breaking, or nearing daily record values). Surface to
boundary layer moisture convergence is further enhanced near the
clear skies of NE NV into SE ID and so convection is stronger
there and downstream into S-central ID. Cores are likely to be
narrow but increase in overall coverage allowing for some
localized 1-1.5" totals in 30-90 minutes, as deep layer flow is
generally weak support 5-10 kt cell motions and increased duration
of moderate to heavy rainfall locally. As such scattered
incidents of flash flooding are possible, particularly near burn
scars.

Through this evening, upper-level divergence further increases
across NE NV into S ID, but along the eastern side of the
circulation has increased convergence through depth with a smaller
scale shortwave/vorticity center lifting northward along the
central UT mountains. This shortwaves and interaction with
outflow boundaries from initial cells will allow for secondary and
perhaps tertiary development that may repeat. As such, the risk
for heavy rainfall is likely to persist through much of the
evening.


Gallina

...Please see https://urldefense.com/v3/__http://www.wpc.ncep.noaa.gov__;!!= DZ3fjg!6NQydPb5XCTg83a4hfFgTuifh8rS1gvX42k7NT31o62I-SzZa5Me5zB78hdcQ5ZU-_B0= F1k--t3Mbad3rxec-6Kwcpo$ for graphic product...

ATTN...WFO...BOI...LKN...PIH...RIW...SLC...

ATTN...RFC...PTR...RSA...STR...NWC...

LAT...LON 43931096 43581037 42781010 42071002 41241009=20
40351032 38891133 38931209 39531217 40041231=20
40811274 40961393 39961518 39871592 40361643=20
42041699 43041689 43151684 43581620 43721511=20
43591390 43541281 43701192=20

=3D =3D =3D
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AWUS01 KWNH 261918
FFGMPD
NMZ000-AZZ000-UTZ000-NVZ000-270100-

Mesoscale Precipitation Discussion 1009
NWS Weather Prediction Center College Park MD
318 PM EDT Tue Aug 26 2025

Areas affected...Northern Arizona...Southern Utah...Extreme
West-northwestern New Mexico...

Concerning...Heavy rainfall...Flash flooding possible

Valid 261920Z - 270100Z

SUMMARY...Deep layer moist, confluent flow, and moderately
unstable environment to support some repeating/training convective
elements across dry/hard soils with localized 1-2" totals and
possible flash flooding conditions through the evening hours.

DISCUSSION...GOES WV mosaic depicts a well defined broad diffluent
area across much of the northern Great Basin into the Rockies of
WY/ID with core of weakly negatively tilted mid-level vorticity
center in central NV angling into NW AZ. A convectively enhanced
smaller scale shortwave is exiting southwest UT into central UT,
lifting northward. The combination of the stronger height-falls
has left the upstream areas within the southeast quadrant with
above normal moisture flux out of the Sonoran Desert and across
the San Francisco Plateau and across UT. Total PWat values of
1-1.25" have expanded up through the valleys of Eastern and
western UT and across N AZ mainly driven in the lowest layers with
Tds as high as the low 60s at KPGA and CNY, similar to those more
common along the Colorado River into SW UT (near KSGU) with all
locations in the area of concern well above normal into the mid to
upper 50s. In the wake of the height-falls and best divergence
aloft, fairly clear skies have provided solid insolation to allow
for increased surface heating and unstable environments support
MUCAPEs of 1000 to 1500 J/kg (greater along the AZ/NM boarder)
within the increasingly confluent streamwise flow. Convergence
along the Mogollon Rim and Mountain/Valley circulations have seen
numerous convective development areas across NW AZ, along the
Mogollon Rim and into the enhanced unstable area along the AZ/NM
border along and downstream of the San Francisco and Gallo Ranges.

Given the flux convergence rates of 1-1.5"/hr are possible, though
deep layer flow is stronger further south in the wake of the
exiting waves, limiting duration. However, north-south confluence
axes are likely to develop and will grant the best potential of
1-2" totals due to short-term (1-2 hour) training or repeating
through 3-5 hour periods. Hard/limited soil conditions with these
rates suggest localized incidents of flash flooding are possible
through the evening.=20=20

Gallina

...Please see https://urldefense.com/v3/__http://www.wpc.ncep.noaa.gov__;!!= DZ3fjg!9hvKjIqfQ5nKLHMM2GpDRcLe5fNZJXYKSTRn-7OlVa4uX6aZ8D_bjfzdnRXR_C6F9poF= eAcnYrJLblRrXfkLhVKi3aY$ for graphic product...

ATTN...WFO...ABQ...FGZ...GJT...SLC...VEF...

ATTN...RFC...FWR...STR...NWC...

LAT...LON 39080961 38600910 37050919 36420886 35990853=20
35650797 34400788 33900843 33821029 34121183=20
34271291 34901362 35671395 36881404 37931390=20
38321304 38791089=20

=3D =3D =3D
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AWUS01 KWNH 262017
FFGMPD
MTZ000-IDZ000-ORZ000-270200-

Mesoscale Precipitation Discussion 1010
NWS Weather Prediction Center College Park MD
416 PM EDT Tue Aug 26 2025

Areas affected...Central Idaho (Salmon River Range)

Concerning...Heavy rainfall...Flash flooding possible

Valid 262015Z - 270200Z

SUMMARY...Increasing slow moving thunderstorms capable of 1"+/hr
rates will eventually expand into a favorable collision/merger
environment and support 1-2"+ totals resulting in scattered
localized incidents of possible flash flooding.

DISCUSSION...GOES WV suite depicts solid SE to NW short-wave
ridging axis across central ID with very favorable divergence
aloft as the northwestern edge of the jet streak expands westward
across MT, further tightening the ridge axis as the core of the
trough slides northeast into NE NV, south-central ID later
tonight. While in the lowest levels, southerly moisture influx
continues to filter through the Snake River Plain up into the
terrain. RAP analysis suggests 850-700mb convergence axis is
approaching, all the while, filtered sunlight has been increasing
surface temperatures and with the increased moisture, greater
instability. Currently MLCAPEs have reached 500 J/kg with limited
capping; and a few of the highest peaks have seen convective
development. As greater moisture and peak heating (1000 J/kg)
increase toward 21-22z, expect convective vigor and coverage to
expand throughout the range.

At the apex of the ridge, mean steering flow will remain weak and persistent/increasing southerly upslope flow may allow for
increased duration/redevelopment through the peaks before moving
off. HRRR and WoFS rapid refresh suggest increasing coverage and
slow motions with 15 and 5 minute rates suggestive of .5" and .2"
rates, respectively, resulting in 1" exceedance probabilities to
near 70-90% toward 23-00z. This is likely, as initial
thunderstorms develop outflows, this will broaden moisture
convergence for increased convective coverage and border updrafts
with each up/down cycle. Mean cell motions of 5-10kts toward the
north and northeast, countered by propagation toward the south due
to inflow, suggests likelihood of cell mergers and localized
instances of effectively stationary motions will allow for
localized totals of 1-2". Naturally low FFG (.75-1"/hr &
1-1.5"/3hrs) may be exceeded; while soils are dry per NASA SPoRT
LIS generally below 25% compared to average, the harder top layers
may be a bit more hydrophobic initially and if rates are intense
enough should limit inflation and further increase run-off and
potential for localized flash flooding.

Gallina

...Please see https://urldefense.com/v3/__http://www.wpc.ncep.noaa.gov__;!!= DZ3fjg!74pzFHqSJ8_XIdH-Y1UL7U9_mRLu7r4pLrEUZ-SpWKC10pCONMWsddZTtjyctxdMo63a= UGrO5MZgF2ZubsoZG5zGCSU$ for graphic product...

ATTN...WFO...BOI...MSO...PIH...

ATTN...RFC...PTR...NWC...

LAT...LON 45661480 45531416 44711333 44051275 43521308=20
43381397 43461543 43811675 44731706 45431601=20 =20=20=20=20=20=20=20=20=20=20=20=20

=3D =3D =3D
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AWUS01 KWNH 262100
FFGMPD
COZ000-NMZ000-WYZ000-270230-

Mesoscale Precipitation Discussion 1011
NWS Weather Prediction Center College Park MD
500 PM EDT Tue Aug 26 2025

Areas affected...South-central WY...Central
Colorado...North-central New Mexico...

Concerning...Heavy rainfall...Flash flooding possible

Valid 262100Z - 270230Z

SUMMARY...Initially slow moving thunderstorms along the Front
Ranges of the Central Rockies will become increasingly efficient
with rates of 1.5"/hr and localized 2-3" totals possible. In
proximity to steeper terrain/urban settings localized flash
flooding is possible.

DISCUSSION...GOES-E Visible and Regional RADAR mosaic depict a
compact shortwave/MCV feature moving through northwest CO nearing
the apex of the larger scale ridge axis. The DPVA along the
leading edge of the wave and across the southeast quadrant has
been forcing scattered convection with intense rainfall production
through the western Colorado Rockies. As the wave is approaching
the Continental Divide, deeper layer moisture from the High Plains
is starting to respond and increase upslope flow along the Front
Ranges of CO and NM at this time. Sufficient morning/afternoon
heating has resulted in the spine of the Rockies to become
conditionally unstable with broad 1000-1500 J/kg of MLCAPE through
the upslope region, given upper 50s Tds and modest mid-level lapse
rates. The 850-700mb confluent flow is providing solid moisture
flux even from the Four Corners region, but obviously greater
depth up to 1.5" has been analyzed through the Front Range and
with 10-15kts should support solid low level flux for efficient
rainfall production as convection further organizes over the next
few hours.

Given core of height-falls remains far enough west, cell motions
will be very slow/stationary given back-building influences; this
is greater further south where mid to upper level flow is weaker
in the anticyclonic rotor of the flow. So as the MCV and
height-falls cross the higher terrain, cells further north will
start propagating eastward a bit sooner than those across the
Sangre de Cristo Ranges. As such, localized totals of 1-2.5" are
probable across the central Rockies of S WY and northern CO; while
spots of 2-3" are more likely (though still scattered in coverage)
further south into Northern New Mexico. This generally aligns
with the naturally low FFG within the upper-slopes of the Front
Range that are .75-1.5"/hr and 1-2"/3hr; local exceedance is
probable and scattered incidents of flash flooding are possible.=20
The risk of flash flooding, of course, is slightly greater if the
cells intersect with the larger urban centers along the Front
Range.

Gallina

...Please see https://urldefense.com/v3/__http://www.wpc.ncep.noaa.gov__;!!= DZ3fjg!52xIQeOGHAzeEx7na_zT5Gve9InU0ZY3Pew0jWjFrEfn4qe8Vl9MmW7SVPuou2Tpp9k-= KsLRNteiAlvqnwdI1YBzz1k$ for graphic product...

ATTN...WFO...ABQ...BOU...CYS...GJT...PUB...

ATTN...RFC...FWR...KRF...STR...TUA...NWC...

LAT...LON 41450661 41340566 41160490 40770438 40200410=20
39600399 38660391 37240397 35890438 35350469=20
35040539 35330637 35810689 36420671 36800620=20
37550569 38190567 38910597 39550713 39960782=20
40590811 41190762=20

=3D =3D =3D
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AWUS01 KWNH 262201
FFGMPD
NVZ000-CAZ000-ORZ000-270300-

Mesoscale Precipitation Discussion 1012
NWS Weather Prediction Center College Park MD
600 PM EDT Tue Aug 26 2025

Areas affected...Northern Sierra Nevada Range & Far Northern
California...

Concerning...Heavy rainfall...Flash flooding possible

Valid 262200Z - 270300Z

SUMMARY...Strong convective thunderstorms capable of 1.5"/hr with
potential for training across complex terrain of the Northern
Sierra Nevada Range may result in localized flash flooding
concerns through the late evening.

DISCUSSION...GOES-W Visible and 10.3um trends show strong, cooling thunderstorms continue to expand and merge into a larger somewhat
linear feature. RADAR and lightning animation, denote cells are strengthening/expanding but also propagating outward both west and
east off the main ridge lines across northeast CA into far western
NV. Total PWat analysis shows northern Central Valley and Great
Basin are well above normal (at 1.2" ranges) with nearly localized
maximum values over the last 30 years; while elevated, the
northern Sierra Nevada range has similar, if slightly lower
percentiles due to the lack of overall vertical depth to reach
values near .7-.9" required. Still, the available moisture is
highly anomalous to support highly efficient rainfall production
given local surface Tds in the low 50s and with temperatures into
the mid-70s, suggest CAPE values are slightly higher than analyzed
at 1000-1500 J/kg. This supports rates of 1.5"/hr given weak but
moist upslope convergent flow.

Along the northwest periphery of the larger scale wave in the
Great Basin has resulted in deeper layer steering/confluence
across the northern Sierra to support a southwestward cell
motions, this may allow for short-term training/repeating over the
next few hours as the remaining inability is exhausted and cells
further expand outward/downslope in each perpendicular to the mean
flow. As such a spot or two of 2" totals remains possible in 30
to 90 minutes, given complex terrain and low FFG values (1-1.5" in
1 to 3hrs), localized flash flooding may be possible through the
next few hours before instability/heating is fully exhausted.

Gallina

...Please see https://urldefense.com/v3/__http://www.wpc.ncep.noaa.gov__;!!= DZ3fjg!-nr_auTAfUNqfK8xidrMCzmQkP4k__XItyVXXqq2AuFJ93DicLLDeIMBRiqJC2Mi5viQ= hia5OeDFB7a81VILZlhpcs0$ for graphic product...

ATTN...WFO...MFR...REV...STO...

ATTN...RFC...RSA...NWC...

LAT...LON 42032213 41802136 41352043 40932002 40501969=20
40111941 39261907 38801945 38781994 39332050=20
39972096 41032182 41432229 41682250 41962248=20 =20=20=20=20=20=20=20=20=20=20=20=20

=3D =3D =3D
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AWUS01 KWNH 270017
FFGMPD
NVZ000-CAZ000-270600-

Mesoscale Precipitation Discussion 1013
NWS Weather Prediction Center College Park MD
817 PM EDT Tue Aug 26 2025

Areas affected...Southern Nevada...Far Southeast California
Deserts...

Concerning...Heavy rainfall...Flash flooding possible

Valid 270015Z - 270600Z

SUMMARY...Converging clusters in vicinity of remaining unstable,
moist air mass to continue widely scattered incidents of localized
flash flooding through early overnight period.

DISCUSSION...GOES-W WV suite continues to show main larger scale
cyclone exiting the northern Great Basin toward the Snake River
Plain with active clusters of activity along the far western
peripheries across the terrain of the Sierra Nevada and in
proximity to the San Bernandino Ranges. These clusters are
expected to continue through northwesterly flow and generally
merge across the southern Great Basin. Currently, there remain
stronger thunderstorms across central San Bernandino county
lifting northward feeding on the remaining limited unstable air at
the northwestern edge of deeper lingering moisture (1-1.25" total
PWats) through the higher deserts of southeast CA. Cells appear
to have generated a cold pool resulting in northeasterly
proapgation and are exepected to diminsh in the next few hours.=20
Still, cells remain capable of a quick .5" of rain in less than
30-60 minutes and given desert, hard rock conditions; flash
flooding would remain possible though increasingly more scattered
in nature with time.

However, this cluster's outflow will remain important as it slides
northeast into SW NV as it will intersect with outflow/convergent
band at nose of northwesterly flow/downward mixing eminating from
the central Sierra Nevada Range. Combine that with return
moisture flow from south to southeasterly flow out of the Colorado
River Valley, much of southern and central Nevada remain
conditionally unstable with 1000-1500 J/kg of MLCAPE analyzed by
the RAP. Total moisture also remains above normal with 1.25"+
Total PWats. As the boundaries intersect toward sunset, an uptick
in convective coverage and intensity is expected. Cell motions
are likely to limit overall totals, but 1-1.5"/hr rates and
localized totals of 1" over desert/rocky ground conditions (where
FFG values are generally less than .75") suggests a few widely
scattered, locally focused instances of flash flooding will remian
possible through 06z.=20=20

Of note, GOES-W Visible imagery shows a bit of mixed aerosols
(mainly smoke over the central Great Basin (NW Nye county and
northwest), cells that have been ingesting the aerosols have shown
a slight increase in rainfall efficiency given increased
nucliation resulting in small but more numerous rain droplets
effectively acting like more tropical/warm cloud processes.

Gallina

...Please see https://urldefense.com/v3/__http://www.wpc.ncep.noaa.gov__;!!= DZ3fjg!74V1dPr2V1I7qJf3U3tYiCzCXFm_qRKibEVubKecco-jKljHyi40E6AStWz4aXw7Ht9p= V_ww2Bc9suShVQLNSbhwmIY$ for graphic product...

ATTN...WFO...LKN...REV...VEF...

ATTN...RFC...RSA...STR...NWC...

LAT...LON 40251764 40111691 39701583 39361516 38951453=20
38251419 37241426 36291485 35281569 34911637=20
34931728 35371759 35911762 36431763 37861786=20
38501830 39141857 39681846 40111816=20

=3D =3D =3D
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AWUS01 KWNH 270047
FFGMPD
UTZ000-IDZ000-ORZ000-270630-

Mesoscale Precipitation Discussion 1014
NWS Weather Prediction Center College Park MD
847 PM EDT Tue Aug 26 2025

Areas affected...Southern Idaho...Far Northern Utah...Far Eastern
Oregon...

Concerning...Heavy rainfall...Flash flooding likely

Valid 270045Z - 270630Z

SUMMARY...Scattered incidents of localized flash flooding likely
to continue through the early overnight period along the northern
and eastern sides of larger scale mid-level cyclone. Additional
totals of 2"+ possible, especially north and west.

DISCUSSION...GOES-W WV suite shows core of large scale mid-level
cyclone continues to lift northward and is currently centered in
far NE NV with very impressive 150 degree highly diffluent
upper-level jet pattern expanding across eastern OR into western
MT before entering the core of the 80-90kt 250mb jet over the
Northern High Plains. The sharpness of the ridging continues to
provide very strong divergence pattern aloft across the Snake
River Plain into the Salmon River Range and low level winds have
responded, backed and accelerated through the Snake River Valley
increasing convergence across southwest ID into the remaining core
of greatest unstable air (1000-1250 J/kg of MLCAPE). Strong
convective arc of overshooting tops can be seen across
Boise/Elmore county extending north. Deep layer moisture to near
1.3-1.4" and 850-700mb winds to 15-20kt per VWP suggest flux will
support 1.5-1.75"/hr rates locally. Slow cell motions in the core
of the ridge aloft should allow for some duration where localized
1-3" totals are possible, which fits well toward the 90th
percentile in recent WoFS run where qualitative assessment
suggests maximum totals generally are just below that 90th
percentile value and in some fairly close proximity. Given
terrain and naturally low FFG values, this provides confidence
that localized incidents of flash flooding are likely over the
next few hours. Generally, convergence axis is expected to
further lift northwest through the Snake Plain into eastern
Oregon, though overall rates/totals should reduce out of the core
of deepest overall moisture, but still remain a flash flooding
risk.

Further upstream, the warm conveyor belt and deep southerly
moisture surge continues east of the deeper overall mid-level
center through western UT into southeast ID, ongoing thunderstorms
continue to burst through the cirrus canopy, through overall well
of unstable air continues to reduce across UT into E ID/far W WY.=20
Overall trends should be diminishing over the next few hours with
that instability/heating loss, but overall moisture and strength
of flux convergence will allow for ongoing activity to be
efficient (though likely a bit less than the stronger deeper cores
further west) spots of additional 1-2" are probable and may induce
similar localized incidents of flash flooding through the early
overnight period. New thunderstorm activity is possible near/just
east of the mid to upper level center as DPVA may locally back
winds and tap smaller areas of remaining unmixed unstable air, but
should be very isolated across northern UT and just over the
border.

Gallina

...Please see https://urldefense.com/v3/__http://www.wpc.ncep.noaa.gov__;!!= DZ3fjg!_MHlBDhPOkyBWvFdzWaUzeAGghjP6LzZPq54HPJXp5jeifzOQjDTKfVP5h4QadF5xnnc= mCMoB37fK6q0fEY9eu6hgjs$ for graphic product...

ATTN...WFO...BOI...MSO...PIH...SLC...

ATTN...RFC...PTR...STR...NWC...

LAT...LON 45081489 44181284 43351173 42671123 41941113=20
41401174 41431359 42101407 42091623 42561769=20
44071815 44801778 45041678=20

=3D =3D =3D
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AWUS01 KWNH 271933
FFGMPD
WYZ000-UTZ000-IDZ000-280030-

Mesoscale Precipitation Discussion 1015
NWS Weather Prediction Center College Park MD
333 PM EDT Wed Aug 27 2025

Areas affected...Southern Idaho...Northern Utah...Western
Wyoming...

Concerning...Heavy rainfall...Flash flooding possible

Valid 271930Z - 280030Z

SUMMARY...Above normal moisture and slow cell motions, with a few
corridors of repeating cells may result in sub-hourly totals of
.5-1" and isolated locations of up to 2". Complex, steep terrain,
old burn scars are at greatest potential for localized flash
flooding through evening.=20

DISCUSSION...GOES-E WV suite and RAP analysis denotes a string of
mid-level vorticity centers within a vortex roll-up pattern
stretching from the strongest wave near the mouth of the Columbia
River in WA/OR crossing the Bitter Roots, Centential and
eventually across the Big Horns toward western Nebraska. Along
and north of the line, scattered dense with very small breaks in
the mid-level cloud canopy has resulted in limited infiltration of
solar heating and therefore unstable environment. However, in
their wake a broad area of fairly clear skies and lingering
remaining moisture which is still well above normal ranging from 1
to 1.3" for Total Pwat values, though most of the surface to
boundary layer moisture remains at or above 60F for Tds across
Snake River Plain, surrounding terrain/valleys into northern UT
and far western WY. As such, near full insolation has brought
SBCAPEs up across much of the area over 1000 J/kg with pockets of
1500 J/kg typically in lower valleys (where vertical depth just
adds to the overall totals).=20

WV and other conventional satellite imagery also denotes a
shortwave feature south of the main shear axis crossing SW ID at
this time, the strength of the wave is maintained/enhanced aloft
by sharp 250mb ridging along the main mid-level shear axis
providing solid right entrance but also diffluent flow for solid
outflow increasing broader vertical ascent/evacuation. As such,
the westerly DPVA is helping to develop arched banding
convergence downstream across SW ID and across the Range and Basin
terrain south of the Snake River Plain across S-central to SE ID
for increasing convective development. While initially narrow in up/downdrafts, vertical strength and low level moisture loading
will increase rainfall rates toward .75-1"/hr. Cells will be
fairly slow moving at 10-15kts and given the orientation of
development across SE ID, some repeating is possible. As such, a
spot or two of up to 2" is possible, though spots of .5-1" in
sub-hourly totals may still result in localized enhanced run-off
and possible flash flooding conditions.

More north-south linear convective lines are developing southward
across N UT, and should not train, but may repeat over areas
affected earlier and may reaggravate any flooding
conditions/higher run-off areas.=20

Nearer the SW ID shortwave, cells should be stronger more
progressive in nature given stronger deeper layer flow, but on the
northern rotor, downshear of the vort center across the Southern Sawtooth/Salmon River Ranges, cells could hang up/slow allowing
for isolated enhanced totals, so have included this area into the
area of concern for overall lower end, isolated to
widely-scattered potential for flash flooding conditions.=20

At this time, have left much of central ID and along SW MT/ID
border excluded given the lack of instability, though strength of
dynamic forcing may continue to be main driver...but is a bit more
uncertain for intense rates, even though Hi-Res CAMs and global
guidance are more consistent with overall rainfall totals. So,
will continue to watch observational trends if an MPD will be
necessary across that area.

Gallina

...Please see https://urldefense.com/v3/__http://www.wpc.ncep.noaa.gov__;!!= DZ3fjg!5IHZJqo_2o5Tpx5Na-mhAKJb3cmy6MgRIjUgJUNHKmOHUUeCU-YdzldClFYsDoVi57aO= LoU8Z8O0GmwxvWAUtA0dpN4$ for graphic product...

ATTN...WFO...BOI...MSO...PIH...RIW...SLC...

ATTN...RFC...KRF...PTR...STR...NWC...

LAT...LON 44441173 44321079 43950984 43240903 42530921=20
42131000 41501033 40631060 40071123 39911190=20
40121247 41011295 41731355 42131416 42451492=20
42841560 43541586 44101564 44311520 44371466=20
44271390 44211303=20

=3D =3D =3D
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AWUS01 KWNH 280026
FFGMPD
KSZ000-COZ000-280530-

Mesoscale Precipitation Discussion 1016
NWS Weather Prediction Center College Park MD
825 PM EDT Wed Aug 27 2025

Areas affected...Eastern Colorado...Western Kansas...

Concerning...Heavy rainfall...Flash flooding possible

Valid 280030Z - 280530Z

SUMMARY...Increasing convection at near strengthening surface low
may result in slow moving clusters with eventual upstream mergers
before main WAA/isentropic ascent/training event occurs
downstream. Localized 2-4" totals through 04-05z may result in
possible localized flash flooding incidents.=20

DISCUSSION...Larger, synoptic scale trough over ID/MT Rockies
continues to elongate into a string of vorticity centers along the
northern edge of the synoptic ridging centered over the New Mexico
and Colorado High Plains. The eastward edge of the vorticity
strip has fostered strong convective cells, expanding into a
forward propagating line of cells across W NEB into NE CO which
will continue to march southward intersecting return low level
moisture and upslope flow over E CO/NW KS over the next few hours.
The DPVA along with strong right entrance of exiting
northwesterly upper-level jet over central and eastern KS; as well
as nose of approaching speed max out of the Four Corners is
supporting solid divergent pattern over eastern CO to support the
thunderstorm activity, but more importantly continue to deepen the
surface cyclone south of Burlington, CO. A well defined surface
front is bending under the deepening low's influence as well as
increasing deep layer moisture convergence along/ahead of the
advancing convective line with newer downstream cells starting to
break out over W KS. These clusters will continue to
strength/expand and with increasing deep layer moisture inflow
will increase in rainfall efficiency over the next few hours over
far E CO. Sub-hourly/instantaneous rates will be strong but
forward propagation may only support localized 1.5-2" totals.

However, pre-convective line cells developing in proximity to the
surface low and southward trending pressure trof/convergence axis
seen very well in late-day visible imagery have been developing
slow moving thunderstorms with solid 20kt surface to boundary
layer inflow of mid 60s Tds and are supporting 1.5-2"/hr rates.=20
Slow motions, waiting for the upstream DPVA/height-falls have been
allowing some localized totals nearing 2-3" and may continue to
support other local totals up to 4" before the main line arrives.=20
While much of SW KS has the locally higher FFG values, a few spots
may be exceeded and result in a localized/focused incident or two
of flash flooding.

Eventually, as the boundary layer decouples after sunset and the
LLJ starts to strengthen and broaden, isentropic ascent along the
frontal zone ahead of the approaching convective line will develop
and orient generally parallel to the mean steering flow allowing
for training and eventual more likely flash flooding concerns
later overnight into central KS (and downstream), but a subsequent
MPD will be written close to that time frame, but until that
time...scattered flash flooding remains locally possible.

Gallina

...Please see https://urldefense.com/v3/__http://www.wpc.ncep.noaa.gov__;!!= DZ3fjg!9bE754lxoKw5PZsgItqw74IudG_FzFFHd9AjW4SzoVEeD2nJei7ET2paaCwiQHxiPcxx= SlgCy-euS1E0W2i9zW8vd1k$ for graphic product...

ATTN...WFO...BOU...DDC...GLD...PUB...

ATTN...RFC...KRF...TUA...NWC...

LAT...LON 40140258 39810163 39209996 38769930 38379909=20
37699933 37370015 37180122 37380175 37910231=20
38210263 38560311 39030358 40090333=20

=3D =3D =3D
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AWUS01 KWNH 280501
FFGMPD
OKZ000-KSZ000-281000-

Mesoscale Precipitation Discussion 1017
NWS Weather Prediction Center College Park MD
100 AM EDT Thu Aug 28 2025

Areas affected...Western and Southern KS...Northern OK

Concerning...Heavy rainfall...Flash flooding possible

Valid 280500Z - 281000Z

SUMMARY...Gradually organizing clusters of heavy showers and
thunderstorms will eventually pose a threat for scattered areas of
flash flooding going through the remainder of the overnight hours.

DISCUSSION...The latest GOES-E IR satellite imagery shows cooling
convective cloud tops across western KS as modest shortwave energy
ejecting east-southeast across the region interacts with a
stationary frontal zone and gradually strengthening warm air
advection associated with an increasing south-southwest low-level
jet.

So far, area VWP show the low-level jet reaching only 20 to 30+
kts across northern OK and southern KS, and the instability
profiles are rather modest too with MUCAPE values along and
northeast of the front of 500 to 1000 J/kg. This has been
tempering the convective organization and coverage over the last
couple of hours, but as the low-level jet strengthens further
(especially after 0600Z), there should be a more substantial
increase in elevated convection across western and southern KS,
and perhaps across northern OK as well where the best instability
gradient is currently situated.

The latest hires CAMs show a fair amount of spread with the exact
placement of the heaviest rainfall threat overnight along with the
totals. Overall, the 00Z HREF suite appears to potentially be a
bit overdone (especially considering the very aggressive 00Z
NAM-Conest), and the consensus may be a bit too far off to the
northeast into the more stable airmass that is currently locked in
place across eastern KS.

Radar and satellite trends along with some of the recent WoFS
guidance suggests areas of western and southern KS will see the
main concentration of heavier shower and thunderstorm activity
over the next few hours. By later tonight, areas of northern OK
should begin to also see more focus for convection as the nose of
a gradually veering low-level jet impinges on this region.

Rainfall rates of 1 to 2 inches/hour are expected with the
stronger storms, and eventually sufficient organization is
expected to foster some cell-training concerns. This will
potentially support rainfall totals of 2 to 4 inches with isolated
5+ inch amounts possible. These rains will eventually pose a
threat for some scattered areas of flash flooding.

Orrison

...Please see https://urldefense.com/v3/__http://www.wpc.ncep.noaa.gov__;!!= DZ3fjg!7k7bvNpDibNHpED4EjVF4mROf3qzlRcrXTOoyx5ugE0gUUo5iPs-DU0da-Vh8o6w0kgq= Y70vc59CQmQ-ZvM1x08FAZU$ for graphic product...

ATTN...WFO...AMA...DDC...GID...GLD...ICT...OUN...TSA...

ATTN...RFC...KRF...TUA...NWC...

LAT...LON 39410098 39179896 37919665 36589641 36089814=20
36740033 37760163 38680190=20

=3D =3D =3D
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AWUS01 KWNH 280906
FFGMPD
MOZ000-ARZ000-OKZ000-KSZ000-281505-

Mesoscale Precipitation Discussion 1018
NWS Weather Prediction Center College Park MD
505 AM EDT Thu Aug 28 2025

Areas affected...Southern KS...North-Central to Northeast OK...Far
Southwest MO...Northwest to Central AR

Concerning...Heavy rainfall...Flash flooding likely

Valid 280905Z - 281505Z

SUMMARY...Organized clusters and bands of showers and
thunderstorms will continue through the morning hours. A
combination of localized cell-training and heavy rainfall rates
will likely result in areas of flash flooding. Locally significant
urban flooding impacts will be possible.

DISCUSSION...The latest GOES-E IR satellite imagery along with
dual-pol radar shows organized clusters of elevated convection
evolving across portions of central and southern KS on down into
northern OK. Additional elevated bands of convection are also
noted well off to the southeast down across northwest to central
AR. The activity early this morning is being strongly supported by
the east-southeast advance of weak mid-level shortwave energy
interacting with a stationary frontal zone and the nose of 40+ kt
southwest low-level jet overrunning it.

A corridor of stronger speed convergence and with proximity of an
elevated instability gradient over southern KS in particular has
allowed for convection across these areas to gain substantial
organization over the last couple of hours with heavy rainfall
rates that are reaching upwards of 2 inches/hour with the stronger
cells.

Enhanced warm air advection/isentropic ascent across this region
to the northeast of the aforementioned front should maintain
convection over the next several hours, but with a gradual
tendency for the convection to lose some latitude while also
advancing off to the east. MUCAPE values are rather modest with
values of 500 to 1000 K/kg, but the increase in low-level moisture
transport and related speed convergence is expected to help
compensate and continue to support locally high rainfall rates
along with a generally organized axis of convection.

The 00Z HREF/REFS suites of guidance are still likely too far to
the north and east with their axis of heavier QPF this morning,
and perhaps a tad too heavy. Recent runs of the HRRR, RRFS and
WoFS all suggest more of a northwest to southeast axis of heavy
rains that impacts southern KS into north-central and northeast OK
going through the morning hours. Heavy rains will also be likely
well off to the southeast across northwest to central AR and
perhaps brushing somewhat into far southwest MO. Additional
localized rainfall totals of as much as 3 to 5+ inches of rain
will be possible, and especially with a favorable environment for cell-training.

Given the elevated rainfall rates and storm totals that are
expected this morning, areas of flash flooding are likely. This
may include a locally significant urban flooding impact.

Orrison

...Please see https://urldefense.com/v3/__http://www.wpc.ncep.noaa.gov__;!!= DZ3fjg!5m-I8xQQKVF8eKEDcLR_pMHmC76VOkazCCu9bo-T4wNOQpYhs4WIn2ZoV6VN2L4K3g1A= DB8QuI83r0GXOKsvZ9Lq2Sc$ for graphic product...

ATTN...WFO...AMA...DDC...ICT...LZK...OUN...SGF...TSA...

ATTN...RFC...KRF...ORN...TUA...NWC...

LAT...LON 38069692 37859541 37269390 36169258 34639123=20
33849142 33809223 34279317 34849419 35489588=20
35739722 36019904 36329971 36750004 37429999=20
37789949 38019828=20

=3D =3D =3D
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AWUS01 KWNH 281455
FFGMPD
ARZ000-OKZ000-281900-

Mesoscale Precipitation Discussion 1019
NWS Weather Prediction Center College Park MD
1055 AM EDT Thu Aug 28 2025

Areas affected...central/eastern OK into western/central/southern
AR

Concerning...Heavy rainfall...Flash flooding likely

Valid 281454Z - 281900Z

SUMMARY...Areas of training with rain rates ranging between 1 to 3
in/hr are expected to produce areas of flash flooding from
portions of eastern OK into western AR through 19Z. Additional
rainfall over the next 4 hours should range between 2 to 4 inches,
but localized higher totals cannot be ruled out.

DISCUSSION...Radar imagery from 1420Z showed an elongated axis of
elevated thunderstorms stretching from central OK into western AR,
along with a secondary axis of NW to SE training from central AR
into central MS. Since 12Z, embedded areas of training within this
broad axis have shown hourly rainfall between 1-2 inches, but
locally in excess of 2 inches as well. A convectively enhanced
vorticity max was observed in water vapor imagery just southeast
of Wichita, KS with movement toward the southeast. MUCAPE values
to the northeast of a frontal boundary (extending from central OK
into eastern TX) were a modest 500 to 1000+ via 14Z SPC
mesoanalysis data but were likely "tall/skinny" with PWAT values
compensating with estimated values near 2 inches within the
ongoing convective axis. VAD wind data showed 925-850 mb winds
overrunning the surface front with 25-35 kt of flow from the
southwest.

A recent southward push to thunderstorms over central OK were
minimizing the flash flood threat across that portion of the state
but new development downstream was showing signs of training with
the coldest cloud tops on IR imagery from eastern OK into western
AR. While forecasts from the RAP indicate a steady weakening of
the 825-850 mb flow into the 15-20 kt range by 19Z, areas of flash
flooding will be likely to sustain in the short term. Over the
next 3-4 hours, forcing for ascent will continue to come from a
combination of isentropic ascent atop the front, DPVA ahead of the
advancing vorticity max positioned over southern KS and diffluent
flow aloft within the anomalously moist environment. Hourly
rainfall of 1-2 inches will be common within areas of training but
isolated hourly totals of 2 to 3 inches may also occur. The
greatest concern will be from eastern OK into western AR where an
additional 2 to 4 inches of rain (locally higher) is expected
through 19Z.

Otto

...Please see https://urldefense.com/v3/__http://www.wpc.ncep.noaa.gov__;!!= DZ3fjg!8avPSJ6cwdAZzHG7igoooXKdXQjxus8-hAHKmHcWhIzu7bO69r6n8DxVE5oSIzUXiQXz= uU-Pe5uQnoAr-uU58pKgA1U$ for graphic product...

ATTN...WFO...JAN...LZK...OUN...SHV...TSA...

ATTN...RFC...ORN...TUA...NWC...

LAT...LON 36399520 35839394 35399297 34959201 34279136=20
33579137 33339229 33709400 33999518 34399642=20
34859707 35199730 35859696 36389581=20

=3D =3D =3D
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AWUS01 KWNH 281542
FFGMPD
ALZ000-MSZ000-LAZ000-ARZ000-282045-

Mesoscale Precipitation Discussion 1020
NWS Weather Prediction Center College Park MD
1142 AM EDT Thu Aug 28 2025

Areas affected...ArkLaMiss into central MS and far western AL

Concerning...Heavy rainfall...Flash flooding possible

Valid 281540Z - 282045Z

SUMMARY...Heavy rainfall may result in localized areas of flash
flooding across central MS in a northwest to southeast fashion,
possibly impacting small portions of AR/LA and AL. Training of
thunderstorms will be capable of 1-2 in/hr rainfall rates. Mostly
dry antecedent conditions should limit the greatest flash flood
risk to urban areas or other locations with poor drainage.

DISCUSSION...Area radar imagery at 1530Z showed a NW to SE
oriented axis of showers and embedded thunderstorms from central
AR into central MS, with KDGX radar reflectivity/velocity data
indicating an MCV to the northeast of Jackson over Leake County.
Areas of heavy rainfall aligned with an elevated 925-850 mb
convergence axis which was oriented northwestward from the MCV
feature over central MS. Deeper layer steering flow oriented
quasi-parallel to the convergence axis has supported periods of
training over the past few hours with MRMS-derived hourly totals
peaking in the 1-2 inch range over the past couple of hours
(mostly in the vicinity of I-20).

Short term RAP forecasts show the MCV tracking ESE toward western
AL over the next 3-5 hours with the trailing convergence axis
remaining from southeastern AR into central MS with a slow
southward drift. While moisture is high (12Z JAN sounding with 2.0
inches), elevated instability is a bit lacking within the ongoing
precipitation axis at ~500 J/kg or less via 15Z SPC mesoanalysis
data, but instability is higher to the south and increasing with
daytime heating. Despite the weak instability, the potential will
exist for localized flash flooding over the next 3-5 hours from
training and 1-2 in/hr rain rates. Storm total rainfall of 2-3
inches will be possible over a relatively short period of time.

Otto

...Please see https://urldefense.com/v3/__http://www.wpc.ncep.noaa.gov__;!!= DZ3fjg!9aNxwB2WRnJaftZCzmSC2XZzVpKIB7lnochofu74QBV-ALY80Igv6A7hLvqYSfvjpGBs= MXySrjwxZ5WvB_VNL529Nz4$ for graphic product...

ATTN...WFO...BMX...JAN...LZK...MEG...MOB...

ATTN...RFC...ALR...ORN...NWC...

LAT...LON 34379117 34049017 33608941 33298862 32918793=20
32268786 31558812 31348924 31759065 33319185=20 =20=20=20=20=20=20=20=20=20=20=20=20

=3D =3D =3D
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AWUS01 KWNH 281903
FFGMPD
LAZ000-ARZ000-TXZ000-OKZ000-290000-

Mesoscale Precipitation Discussion 1021
NWS Weather Prediction Center College Park MD
303 PM EDT Thu Aug 28 2025

Areas affected...in and around ArkLaTex

Concerning...Heavy rainfall...Flash flooding possible

Valid 281900Z - 290000Z

SUMMARY...A few areas of isolated flash flooding will be possible
from southeastern OK/northeastern TX into southern AR and northern
LA through 00Z. Localized instances of training should support
hourly rainfall of 1 to 2 inches with spotty hourly totals of 2 to
3 inches.

DISCUSSION...Radar imagery from 1830Z showed broken coverage of
thunderstorms extending from east-central OK into central AR, with
a reduction in rainfall intensity and training axes over the past
couple of hours, partially tied to a weakened low level jet. There
were embedded mesoscale circulations noted within the broader
precipitation shield, located out ahead of a low to mid-level
shortwave located near the MO/KS/AR/OK 4-state junction,
translating downstream. This region of convection was located to
the north of a well-defined stationary front, enhanced by
differential heating, which extended WNW to ESE from the Red River
Valley into southern MS. Low level flow of 10-20 kt was in place
over northern TX into northwestern LA via VAD wind plots,
supporting overrunning of the front with cells moving
quasi-parallel to the boundary toward the ESE, allowing for
localized training and repeating. Aloft, flow was diffluent,
aiding in vertical ascent across the ArkLaTx region.

Robust surface heating to the south of the front was aiding in a
sharp instability gradient with 1500+ J/kg MLCAPE from far
southeastern OK into eastern TX and central LA and PWATs were
close to 2 inches in and around the ArkLaTex via 18Z SPC
mesoanalysis data. Additional thunderstorms are expected to form
near the frontal boundary over the next 2-4 hours with a general
movement of cells off toward the ESE. While coverage of these
additional cells remains uncertain, ongoing upstream convection
over OK and AR should continue while advancing toward the
SE/ESE...out ahead of the upstream shortwave. Alignment of
boundaries and the mean steering flow will likely support a few
areas of at least brief training and 1 to 2 inches of rain within
an hour. However, higher hourly rainfall totals cannot be ruled
out and may contribute to localized areas of flash flooding where
training is able to persist for 1-2 hours.

A negative to flash flood potential is that most of the outlooked
area has received below average rainfall over the past 1-2 weeks
leading to high flash flood guidance values of 3 to 5+ inches in 3
hours. Therefore, the greatest flash flood risk will likely reside
within urban areas or other locations with poor drainage.

Otto

...Please see https://urldefense.com/v3/__http://www.wpc.ncep.noaa.gov__;!!= DZ3fjg!5Oh1ytZJBqaRDC8CA5opGMb2tIZJ7XMq7SI7rROJplJToWFD761KOmyqxxCw5zhWk5Ms= aC4pMHHA0A7ha51JWCo09fI$ for graphic product...

ATTN...WFO...FWD...JAN...LCH...LZK...OUN...SHV...TSA...

ATTN...RFC...FWR...ORN...TUA...NWC...

LAT...LON 35159452 34899348 34149235 32749166 31129242=20
31559426 32859630 34169663 34969591=20

=3D =3D =3D
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AWUS01 KWNH 290701
FFGMPD
ALZ000-MSZ000-LAZ000-ARZ000-TXZ000-OKZ000-291300-

Mesoscale Precipitation Discussion 1022
NWS Weather Prediction Center College Park MD
300 AM EDT Fri Aug 29 2025

Areas affected...Northeast TX...Far Southern AR...Northern and
Central LA...Central and Southern MS

Concerning...Heavy rainfall...Flash flooding possible

Valid 290700Z - 291300Z

SUMMARY...Expanding bands of heavy showers and thunderstorms with
cell-training concerns are expected going through mid-morning.
This will gradually pose a concern for areas of flash flooding.

DISCUSSION...The latest GOES-E IR satellite imagery is gradually
showing an uptick in cooling convective tops near the Arklatex
region, and with additional broken bands of elevated convection
extending off to the southeast across northern LA and through
central MS.

A gradual increase in warm air advection/isentropic ascent is
noted on the poleward side of a quasi-stationary front and within
a very moist and moderately unstable airmass. MUCAPE values are as
high as 1000 to 2000 J/kg along the front involving eastern TX
through central LA, however, much of the elevated convection is
rooted within the instability gradient farther north along the
AR/LA border along with adjacent areas to the west and east. This
is also where there is some modest frontogenesis and related
forcing seen in the 925/850 mb layer. Meanwhile, the PWs are on
the order of 2.0 to 2.25 inches and suggestive of a very tropical
environment.

The flow aloft is becoming increasingly divergent as an
upper-level jet streak rounds into the base of the deeper layer
trough over the Mid-South/OH Valley region, and this should drive
a low-level response this morning with an additional increase and
gradual veering of the low-level flow across eastern TX and
central LA. This will interact with the aforementioned frontal
zone and promote stronger isentropic ascent and frontogenetical
forcing.

This along with the pool of instability that is available will
favor additional development and expansion of heavy showers and
thunderstorms with at least some loose organization given
proximity of 30 to 40 kts of effective bulk shear. Propagation
vectors are relatively weak which suggests there may be some
attempt at some backbuilding cells, and given the linear nature of
some of these elevated bands of convection, there will be concerns
for cell-training.

Rainfall rates will be very high and capable of reaching 2.5
inches/hour given the level of moisture and instability, and with
the backbuilding/cell-training concerns, some rainfall totals
going through mid-morning may reach 3 to 5+ inches.

A gradual southward advance of the overall convective footprint is
expected over the next several hours, but with these rains, there
may be areas of flash flooding that materialize and especially for
the more sensitive urban environments.

Orrison

...Please see https://urldefense.com/v3/__http://www.wpc.ncep.noaa.gov__;!!= DZ3fjg!6JUvKl93dizNJOe4QATzDqiKcq_s5hv4AQ3X_iBV53O14dIFT2WG99iZSWvUZpUBM1kE= mLyb_aBCGGy6tH4E8qXVepA$ for graphic product...

ATTN...WFO...FWD...JAN...LCH...LIX...LZK...MOB...OUN...SHV...
TSA...

ATTN...RFC...ALR...FWR...ORN...TUA...NWC...

LAT...LON 33989551 33699411 33259262 32829060 32558959=20
32318886 31518832 30338870 30189014 30679292=20
31249453 32199614 33229668 33879630=20

=3D =3D =3D
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AWUS01 KWNH 291301
FFGMPD
MSZ000-LAZ000-TXZ000-291730-

Mesoscale Precipitation Discussion 1023
NWS Weather Prediction Center College Park MD
900 AM EDT Fri Aug 29 2025

Areas affected...eastern TX into LA and southern MS

Concerning...Heavy rainfall...Flash flooding likely

Valid 291259Z - 291730Z

SUMMARY...Localized to widely scattered areas of flash flooding
will remain likely early this morning, possibly extending into the
early afternoon from portions of eastern TX into LA and southern
MS. While coverage of flash flooding may be limited, the potential
for very high rates in excess of 3 in/hr will exist.

DISCUSSION...1240Z radar imagery showed elevated thunderstorms
from northeastern TX into central LA and southern MS with embedded
areas of training and MRMS-derived hourly rainfall of 2 to 3+
inches...mainly over the north-central TX/LA border and just north
of Alexandria, LA. The environment was characterized by very high
moisture (PWATs 2.2 to 2.5 inches) and 500-1000 J/kg MUCAPE via
12Z SPC mesoanalysis data. Rainfall has been efficient given this
environment with local 88D imagery showing cells containing low
echo centroid signatures and 15 minute rates over 1 inch per MRMS
and gauge data. An elevated convergence axis stretched
southeastward from northeastern TX and was being overrun by
925-850 mb winds of ~15 to 20 kt from the SW, favorably ascending
the boundary with deeper layer mean winds translating cells toward
the southeast.

An MCV-like feature appeared to be located between JAN and PIB,
with movement toward the east. The low level convergence axis has
been advancing slowly but steadily toward the south over
southwestern MS into central LA, limiting the coverage and
magnitude of rainfall rates. The boundary was also advancing over
TX, toward the southwest, but its orientation aligning more
favorably with the mean wind was supporting a locally enhanced
flash flood threat over northeastern TX as of 1240Z. This area
will continue to be a locally higher concern in the short term
with hourly rainfall of 2 to 3+ inches. Short term RAP forecasts
show weakening and further veering of the low level flow through
17Z which should tend to lessen the overrunning component from
central LA into MS, but some isolated areas of training will
remain along the elevated convergence axis.

The flash flood threat should linger a bit longer over eastern TX
into western LA where despite weakening low level winds into the
rest of the morning, high moisture and areas of training should
focus at least a localized flash flood concern over the next few
hours. Additional development of thunderstorms with the onset of
daytime heating across southwestern LA may also pose a flash flood
threat after 15Z with an added component related to the advancing
low level axis of convergence from the north.

Otto

...Please see https://urldefense.com/v3/__http://www.wpc.ncep.noaa.gov__;!!= DZ3fjg!9OirOFvdV-G9fEyWtv2r_Md_tzwHfgOGaGgx0Wv4dHtORV6jnS9XrcFvAEULfpGO-JS2= uFo0W2zCeDUCdl6ng-EkvOU$ for graphic product...

ATTN...WFO...FWD...HGX...JAN...LCH...LIX...MOB...SHV...

ATTN...RFC...FWR...ORN...NWC...

LAT...LON 33179511 33179444 32529362 31919224 31789059=20
31958945 31708869 31128847 30458876 29768996=20
29429118 29439301 29719395 30539469 31489541=20
32179566 32759557=20

=3D =3D =3D
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AWUS01 KWNH 291814
FFGMPD
LAZ000-292111-

Mesoscale Precipitation Discussion 1024
NWS Weather Prediction Center College Park MD
213 PM EDT Fri Aug 29 2025

Areas affected...southern Louisiana

Concerning...Heavy rainfall...Flash flooding possible

Valid 291811Z - 292111Z

Summary...Brief/isolated flash flooding is possible across
southern Louisiana through 4p CDT/21Z.

Discussion...Over the last hour or so, a mesoscale convective
complex near Baton Rouge has increased in intensity while
migrating slowly southward. Additional cells were developing from
this complex southwestward toward Lake Charles, Lafayette, and
along I-10. These cells were migrating toward an abundantly
moist/unstable pre-convective airmass (2.3+ inch PW values, 3500
J/kg SBCAPE), supporting strong updrafts and efficient rainfall
rates within the most persistent activity. Despite southward
motions, areas of 1-2 inch/hr rain rates have been estimated per
MRMS near the Baton Rouge area. These rates may be enough to
support an isolated flash flood risk especially near urban/flash
flood prone areas across southern Louisiana.

Models/observations are all suggestive of a continued, yet slow
southward progression of the ongoing activity toward the Gulf
Coast through 4p CDT/21Z. Some of the heavier rain rates may
impact western portions of New Orleans Metro during that
timeframe. Flash flooding could occur with ongoing activity, but
should be isolated and focused on urban/sensitive areas. Areas of
1-2 inch/hr rain rates should continue, with higher rates/rainfall
totals possible near any localized areas of training/cell mergers.

Cook

...Please see https://urldefense.com/v3/__http://www.wpc.ncep.noaa.gov__;!!= DZ3fjg!_Zvkj-bUelgq3vwpm450SXtdlVxH7rveg9xI80KKeO097j4G-jNR2S31u7uSgiC3_RUe= ksU96Cba7uhXLuKarbBdUbE$ for graphic product...

ATTN...WFO...LCH...LIX...

ATTN...RFC...ORN...NWC...

LAT...LON 30489171 30419035 29918921 29318911 29059006=20
29149166 29609308 30209320=20

=3D =3D =3D
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AWUS01 KWNH 291829
FFGMPD
TXZ000-NMZ000-AZZ000-300028-

Mesoscale Precipitation Discussion 1025
NWS Weather Prediction Center College Park MD
228 PM EDT Fri Aug 29 2025

Areas affected...New Mexico

Concerning...Heavy rainfall...Flash flooding likely

Valid 291828Z - 300028Z

Summary...Isolated flash flood potential should expand/increase
though 00Z/6p MDT this afternoon.

Discussion...Satellite and radar depict isolated thunderstorm
development primarily along favored ridgelines/high terrain from southern/southwestern through north-central New Mexico. The
storms have formed due to abundant surface heating beneath a
pronounced mid-level moisture plume across western and central
parts of the state. Flow aloft (strongest over the western parts
of the state) were supporting slow northeastward storm motions
with developing activity, although localized backbuilding was
already noted across south-central and southwestern New Mexico.=20
Where the backbuilding has been most pronounced (east of
Alamogordo), rain rates approaching 2 inches/hr have been
estimated per MRMS.

Given appreciable moisture values, weak mid-level disturbances,
and continued surface heating, conditions favor an expansion of
convective coverage through the afternoon and early evening hours
across the discussion area. Any downpours near existing burn
scars could promote a quickly evolving and locally significant
flash flood threat. Areas of 1-2 inch/hr rain rates are likely to
expand in tandem with increasing convective coverage, and the
highest rain rates are likely across the southeastern 1/2 of the
state where steering flow aloft is the weakest and tropospheric
moisture content highest.

Wind profiles across northeastern/east-central New Mexico favor
eventual growth into slow-moving clusters of storms that may
prompt a slightly higher concentration of flash flood instances
over time.

Cook

...Please see https://urldefense.com/v3/__http://www.wpc.ncep.noaa.gov__;!!= DZ3fjg!_uJyp8RiiukATBXTgTjKeysUvouAANFSkFCZeONY0yCsSzC-eqw4XmMWyhlzKHLM50d_= Ur0SXdxLzu-Fl0M9yM_9x70$ for graphic product...

ATTN...WFO...ABQ...EPZ...MAF...TWC...

ATTN...RFC...FWR...STR...TUA...NWC...

LAT...LON 36700397 34410338 32000454 31840694 31790910=20
33840879 36660668=20

=3D =3D =3D
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AWUS01 KWNH 292004
FFGMPD
FLZ000-300203-

Mesoscale Precipitation Discussion 1026
NWS Weather Prediction Center College Park MD
403 PM EDT Fri Aug 29 2025

Areas affected...portions of southeastern Florida

Concerning...Heavy rainfall...Flash flooding possible

Valid 292003Z - 300203Z

Summary...Isolated/urban flash flooding is possible through the
afternoon and early evening.

Discussion...Recent satellite/lightning imagery depicts rapid
development of deep convection along a sea breeze boundary just
west of Miami (near Kendall), with additional, scattered activity
located over the Everglades. The cells were forming in an
environment characterized by strong instability (2000+ J/kg
MLCAPE) and plenteous moisture content (1.8+ inch PW values).=20
These environmental parameters - combined with weak/negligible
tropospheric flow for steering) was promoting ongoing development.
The cell near Kendall was already producing estimated 1-2 inch/hr
rain rates, which isn't a surprise given its slow movement amid
abundant moisture/instability.

Models/CAMs suggest that ongoing development will continue to
expand in coverage an intensity given continued
heating/destabilization along the sea breeze, which was located
just inland along populated areas of southeastern Florida.=20
Additional areas of 1+ inch/hr rain rates are expected, which
could result in flash flooding in urban and low-lying areas. Much
of the flash flood risk should be diurnally driven, with weakening
expected from both 1) loss of surface heating and 2) stabilization
from scattered to widespread convective overturning across the
discussion area.

Cook

...Please see https://urldefense.com/v3/__http://www.wpc.ncep.noaa.gov__;!!= DZ3fjg!4P9wSE9JUPm8UY_UWf3nZX8jBI-M5PpiYTrkvqv0xeYUGZUKYiGm0MsV_E2dHifisuAy= pOEoph6st-iCS1W817vzuOA$ for graphic product...

ATTN...WFO...KEY...MFL...MLB...

ATTN...RFC...ALR...NWC...

LAT...LON 27628039 27268000 27177995 26617995 25958006=20
25228030 24968060 25218080 25858069 27208048=20 =20=20=20=20=20=20=20=20=20=20=20=20

=3D =3D =3D
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AWUS01 KWNH 292248
FFGMPD
KSZ000-COZ000-300246-

Mesoscale Precipitation Discussion 1027
NWS Weather Prediction Center College Park MD
647 PM EDT Fri Aug 29 2025

Areas affected...central/eastern Colorado, far western Kansas

Concerning...Heavy rainfall...Flash flooding possible

Valid 292246Z - 300246Z

Summary...Scattered thunderstorm activity was backbuilding along
the I-25 corridor between Colorado Springs and Pueblo. A couple
instances of flash flooding are possible through 02Z/8p MDT.

Discussion...Recent radar mosaic imagery has depicted backbuilding
convection along a relatively focused axis extending from I-25
between Colorado Springs and Pueblo eastward to near State Highway
71. The storms are forming in a weak low-level-shear environment,
with 15-25F surface dewpoint depressions supporting mostly
outflow-dominant storms. Despite the tendency for outflow
dominance, upstream mid-level flow was aiding in maintaining

7C/km mid-level lapse rates, and an upstream mid-level

disturbance (evident via water vapor) was providing ascent aloft
while moving toward the discussion area. PW values near 1 inch
and the backbuilding character of convection was supporting
occasional rain rates exceeding 1 inch/hr in spots that were
beginning to exceed FFG thresholds on an isolated basis.

The ongoing scenario should support a localized flash flood threat
(tied to backbuilding convection) for a few hours this afternoon.=20 Models/CAMs suggest that ongoing activity will eventually pick up
more of an eastward component of motion while moving toward
eastern Colorado, supporting isolated flash flood potential
downstream of ongoing storms especially where mergers/training can
occur. The downstream airmass is slightly more favorable for
heavy rainfall given higher PW values (1.5 inch near the KS/CO
border). Isolated instances of flash flooding are possible in
this regime.

Cook

...Please see https://urldefense.com/v3/__http://www.wpc.ncep.noaa.gov__;!!= DZ3fjg!-8aATgiuNWW-kCAHA4QdqTfVqAfCTbSPQpq_79RUQQx0luKXMfDDZrjx0rdfd58BSlqy= lAwOt8me5lHRWAz4PstURbM$ for graphic product...

ATTN...WFO...BOU...DDC...GLD...PUB...

ATTN...RFC...KRF...TUA...NWC...

LAT...LON 39740392 38690193 37090185 37740370 38140532=20
39520558=20

=3D =3D =3D
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AWUS01 KWNH 300029
FFGMPD
TXZ000-NMZ000-AZZ000-300328-

Mesoscale Precipitation Discussion 1028
NWS Weather Prediction Center College Park MD
829 PM EDT Fri Aug 29 2025

Areas affected...southern New Mexico, far southeastern Arizona

Concerning...Heavy rainfall...Flash flooding possible

Valid 300028Z - 300328Z

Summary...Low-end/isolated flash flood potential continues for a
few more hours.

Discussion...Deep convection has materialized over the course of
the afternoon and produced isolated spots of 1-1.5 inch/hr rain
rates at times. Short-term trends indicate widespread convective
overturning that has stabilized the low-level airmass in most
areas. Despite stabilization, several areas of thunderstorms
continue across south-central New Mexico (near the Sacramento
Mountains) and along far northern Mexico (potentially drifting
northward toward the AZ/NM international border area over the next
1-2 hours). The pre-convective airmass supporting convection
continues to be moist and unstable, with 1-1.4 inch PW values and
500-1000 J/kg MLCAPE to support deep convection and isolated flash
flood potential.

With time, low-levels are expected to further stabilize with loss
of surface heating. The flash flood threat (already isolated)
should also progressively lower with time as well. Most of the
threat should wane after 03Z or so.

Cook

...Please see https://urldefense.com/v3/__http://www.wpc.ncep.noaa.gov__;!!= DZ3fjg!8PncgyjeCZUkzyhRcMLqq7-naG5LnudJFl3sCWD6hhkJ_PVIguIUh5DdivP0NTdAwjaH= P58-HRYaMY-l4Xjzg_AVFlg$ for graphic product...

ATTN...WFO...ABQ...EPZ...MAF...TWC...

ATTN...RFC...FWR...STR...NWC...

LAT...LON 34880638 34060439 32730448 31990655 31780811=20
31400826 31281094 32101067 32940896 34200780=20 =20=20=20=20=20=20=20=20=20=20=20=20

=3D =3D =3D
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AWUS01 KWNH 300033
FFGMPD
TXZ000-NMZ000-AZZ000-300328-

Mesoscale Precipitation Discussion 1028
NWS Weather Prediction Center College Park MD
832 PM EDT Fri Aug 29 2025

Areas affected...southern New Mexico, far southeastern Arizona

Concerning...Heavy rainfall...Flash flooding possible

Valid 300028Z - 300328Z

Summary...Low-end/isolated flash flood potential continues for a
few more hours.

Discussion...Deep convection has materialized over the course of
the afternoon and produced isolated spots of 1-1.5 inch/hr rain
rates at times. Short-term trends indicate widespread convective
overturning that has stabilized the low-level airmass in most
areas. Despite stabilization, several areas of thunderstorms
continue across south-central New Mexico (near the Sacramento
Mountains) and along far northern Mexico (potentially drifting
northward toward the AZ/NM international border area over the next
1-2 hours). The pre-convective airmass supporting convection
continues to be moist and unstable, with 1-1.4 inch PW values and
500-1000 J/kg MLCAPE to support deep convection and isolated flash
flood potential. This potential may maximize in/near burn scar
areas, where just a quick 0.5 inch of rainfall could cause
excessive runoff.

With time, low-levels are expected to further stabilize with loss
of surface heating. The flash flood threat (already isolated)
should also progressively lower with time as well. Most of the
threat should wane after 03Z or so.

Cook

...Please see https://urldefense.com/v3/__http://www.wpc.ncep.noaa.gov__;!!= DZ3fjg!4_J6q96rSBzK4NCv0FiHpYdhTqeBOL71bsn0rWdiHe79Gmk8bi0IHU_DXLYFoudg5Y14= ZT86U9EPtmodkfozYDTzfGQ$ for graphic product...

ATTN...WFO...ABQ...EPZ...MAF...TWC...

ATTN...RFC...FWR...STR...NWC...

LAT...LON 34880638 34060439 32730448 31990655 31780811=20
31400826 31281094 32101067 32940896 34200780=20 =20=20=20=20=20=20=20=20=20=20=20=20

=3D =3D =3D
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AWUS01 KWNH 300047
FFGMPD
TXZ000-OKZ000-KSZ000-NMZ000-300545-

Mesoscale Precipitation Discussion 1029
NWS Weather Prediction Center College Park MD
846 PM EDT Fri Aug 29 2025

Areas affected...eastern New Mexico, west Texas, Texas South
Plains/Panhandle, Oklahoma Panhandle

Concerning...Heavy rainfall...Flash flooding possible

Valid 300045Z - 300545Z

Summary...Isolated instances of flash flooding are possible as
convection emanates eastward from the southern High Plains this
evening.

Discussion...Maturing convection over New Mexico has gradually
organized into clusters and linear segments while approaching the
NM/TX border region and portions of the Oklahoma Panhandle. The
storms were moving eastward toward a progressively more moist
airmass (1.6 inch PW values) and sufficient instability (1500 J/kg
SBCAPE) to sustain convection for at least 2-4 more hours.=20
Kinematic fields feature relatively weak steering flow aloft,
allowing for weak easterly/southeasterly cell movement driven
partially by local convective organization/evolution. Areas of 1
inch/hr rain rates are already estimated per MRMS, and the overall
radar presentation seems to suggest that mergers will gradually
become more frequent, increasing rain rates locally.

As cells move eastward deeper into the Texas/Oklahoma Panhandles
and Texas South Plains, they will migrate over regions of the
country that have FFG thresholds in the 2-3 inch/hr range (locally
lower). Furthermore, soil moisture profiles are a bit on the dry
side, suggestive of soils that can handle some of the impending
rainfall. The overall scenario suggests potential for isolated
flash flooding to occur especially in any sensitive/low-lying
spots. The risk may be locally maximized where mergers can
prolong heavy rainfall and boost local rain rates.

Cook

...Please see https://urldefense.com/v3/__http://www.wpc.ncep.noaa.gov__;!!= DZ3fjg!4bJNTo6H477kWvtLG3ItNZHX_EQn63wiYDKLhK3x4p9w_WBNlKwn6RQ9qZmOj_AWswrF= YRZj9jwT2HlIQrqYwtEk2DY$ for graphic product...

ATTN...WFO...ABQ...AMA...DDC...LUB...MAF...SJT...

ATTN...RFC...FWR...TUA...NWC...

LAT...LON 37050121 36400081 34510129 31910124 31690224=20
32120330 32890368 33940389 34670445 35820470=20
36400386 36890223=20

=3D =3D =3D
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AWUS01 KWNH 300502
FFGMPD
TXZ000-NMZ000-300930-

Mesoscale Precipitation Discussion 1030
NWS Weather Prediction Center College Park MD
100 AM EDT Sat Aug 30 2025

Areas affected...Southeast NM...Western TX

Concerning...Heavy rainfall...Flash flooding possible

Valid 300500Z - 300930Z

SUMMARY...Heavy showers and thunderstorms will continue to pose a
threat for some additional areas of flash flooding overnight.

DISCUSSION...The latest GOES-W IR satellite imagery shows
cold-topped convection continuing to evolve across portions of
southeast NM and western TX. In fact, the trends have shown an
uptick in convective organization with cooling cloud tops over
especially southeast NM where radar confirms a couple of
semi-linear bands of very heavy showers and thunderstorms.

MLCAPE values of 500 to 1000 J/kg remain in place which coupled
with subtle mid-level vort energy ejecting east out into the
southern High Plains is helping to maintain the ongoing convective
activity. However, cooling boundary layer temperatures and
convective overturning continue to put pressure on the instability
environment, and there should be a gradual weakening of the
overall convective footprint by later in the night.

PWs of 1.5 to 1.6+ inches are in place which is helping to yield
heavy rainfall rates of 1 to 2 inches/hour with the stronger
storms. These heavier rainfall rates coupled with locally slow
cell-motions and pockets of cell-training may foster some
additional isolated rainfall totals of 2 to 4+ inches. This is
supported by the 00Z HREF guidance.

These additional rains will support a threat for additional areas
of flash flooding going through the overnight hours. However, by
later tonight the convection should weaken sufficiently to allow
for the flash flooding threat to diminish.

Orrison

...Please see https://urldefense.com/v3/__http://www.wpc.ncep.noaa.gov__;!!= DZ3fjg!9KpuwMqdwZr74y4RUcRsZJXFAyv7EcZCQwACObI4GNhuQ_dKZaUgAh8lt2iam00TmyI9= GKCInVBnmdrLysOEpbb4zUs$ for graphic product...

ATTN...WFO...ABQ...EPZ...LUB...MAF...

ATTN...RFC...FWR...TUA...NWC...

LAT...LON 34740141 34320066 33310052 32230157 31260328=20
30810485 31110595 31830638 32590601 33330477=20
33990379 34640259=20

=3D =3D =3D
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AWUS01 KWNH 301305
FFGMPD
LAZ000-TXZ000-301715-

Mesoscale Precipitation Discussion 1031
NWS Weather Prediction Center College Park MD
904 AM EDT Sat Aug 30 2025

Areas affected...eastern TX into southwestern LA

Concerning...Heavy rainfall...Flash flooding likely

Valid 301303Z - 301715Z

SUMMARY...Heavy to extreme rain rates over 3 in/hr are expected to
occur within localized pockets over portions of eastern TX and
southwestern LA over the next few hours. Areas of flash flooding
are likely to continue through 17Z.

DISCUSSION...1245Z radar imagery over the lower Sabine River
Valley showed a small cluster of thunderstorms west and northwest
of LCH with 3 Wunderground observation stations reporting 3+
inches of rain in an hour two stations showing 5 inches in an hour
through 12Z. Thunderstorm coverage was expanding NNW from
southwestern LA into portions of eastern TX along an elevated
(925-850 mb) convergence axis with low level flow intersecting the
boundary from the west. Some of the "strongest" low level flow was
located just south of the DFW Metroplex and over southwestern LA
with about 10-15 kt oriented nearly perpendicular to the elevated
convergence axis with mean layer winds directing cells slowly
toward the southeast. SPC mesoanalysis data from 12Z showed MUCAPE
values of 500-1500 J/kg coincident with PWATs of 2.1 to 2.3+
inches.

Short term forecasts from the RAP show the low level flow
maintaining over the next few hours but with gradual weakening
through 17Z which may act to disrupt organization late this
morning. However, the environment will remain supportive of highly
efficient rainfall production until then with pockets of extreme
rain rates possible (3+ in/hr) and localized storm totals in
excess of 5 inches through 17Z. Areas of flash flooding will be
likely and trends will be monitored for additional MPDs as needed
later this morning.

Otto

...Please see https://urldefense.com/v3/__http://www.wpc.ncep.noaa.gov__;!!= DZ3fjg!9LLqDy_VP4nvEvj6Oq1-i2fSu0y3E9K-Ehzuz9U53l86YISsyt50n__zjcrr8EX39JmT= SJbnJiW7TMNTNv_Y1ajrm7o$ for graphic product...

ATTN...WFO...FWD...HGX...LCH...SHV...

ATTN...RFC...FWR...ORN...TUA...NWC...

LAT...LON 33749671 33139547 31009322 30339289 29939296=20
29649337 29589393 29769442 30549520 31689627=20
32679726 33539748=20

=3D =3D =3D
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AWUS01 KWNH 301644
FFGMPD
KSZ000-NEZ000-SDZ000-302215-

Mesoscale Precipitation Discussion 1032
NWS Weather Prediction Center College Park MD
1243 PM EDT Sat Aug 30 2025

Areas affected...central SD into east-central NE

Concerning...Heavy rainfall...Flash flooding possible

Valid 301640Z - 302215Z

SUMMARY...Slow moving cores of heavy rainfall are expected from
central SD into east-central NE over the next 3-6 hours. Hourly
rainfall of 1 to 2 inches can be expected at times, which may
produce a couple of areas of flash flooding.

DISCUSSION...Water vapor imagery from GOES East showed a complex
pattern across the central U.S. with a number of mid-level
vorticity maxima extending from the Dakotas into NE. Upstream, a
longwave trough axis was noted across WY to the UT/CO border,
advancing east with small scale vorticity maxima embedded within
the southwest flow out ahead across the High Plains. Low to
mid-level analyses showed a nearly stationary low over
west-central SD, associated with a slow moving cyclonic swirl of
heavy rain centered over Haakon County with MRMS-derived rainfall
rates of 1 to 2+ in/hr ending 14 and 15Z, though recent rates have
lowered to about 1 in/hr. A trough axis extended SSE from the low
into central NE with widely scattered showers and thunderstorms
over the NE Sandhills into portions of east-central NE.
Satellite-derived precipitable water imagery indicated that a
tongue of higher moisture extended northward through the central
Plains into central SD, ahead of the quasi-stationary low. OSPO
LPW imagery showed low level components of this moisture plume
from the southern Plains and mid to upper level components from
the Southwest, including remnant moisture from former T.S.
Juliette in the eastern Pacific. The remnant tropical moisture
could be a factor in enhancing rainfall efficiency this afternoon.

As the longwave trough axis passes across the central Rockies this
afternoon, downstream diffluence will increase over NE and
southern SD, helping to increase ascent. While the low over SD is
not expected to move through 22Z, the southern extension of the
trough into NE should swing east and possibly develop with a
secondary low center. Mesoscale circulations within this pattern
are expected to support slow moving cores of heavy rain.

One negating factor is the presence of weak instability with 16Z
SPC mesoanalysis data showing only 500-1000 J/kg MLCAPE over parts
of SD and western NE and less than 500 J/kg over eastern SD/NE.
Widespread cloud cover may limit the development of higher
instability over central to eastern SD/NE later this afternoon,
capping rainfall intensity. However, the favorable moisture axis
and slow movement of rainfall may still allow for localized
pockets of 1-2 in/hr rates and possible flash flooding over the
next 3-5 hours.

Otto

...Please see https://urldefense.com/v3/__http://www.wpc.ncep.noaa.gov__;!!= DZ3fjg!9jwKvyGamGIGqHxeg9PdUqiMnAtKNUANn2FMc-ZvOXli28xbL41LCzb9IHB5l7eNkX6G= WVu_d_1Hp8nMZ03GtAqMSts$ for graphic product...

ATTN...WFO...ABR...FSD...GID...LBF...OAX...UNR...

ATTN...RFC...KRF...NWC...

LAT...LON 45730200 45630108 44879969 43389808 41789709=20
41009706 40149768 39939835 40019874 40279901=20
40509918 40679930 41209947 41509951 41679949=20
41799940 41799920 41739899 41679883 41579861=20
41709841 41729829 41849810 42229811 42369826=20
42559871 42699978 42950061 43430136 43590166=20
44300289 45170313 45490274=20

=3D =3D =3D
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AWUS01 KWNH 301728
FFGMPD
TXZ000-302100-

Mesoscale Precipitation Discussion 1033
NWS Weather Prediction Center College Park MD
128 PM EDT Sat Aug 30 2025

Areas affected...eastern TX into fa

Concerning...Heavy rainfall...Flash flooding likely

Valid 301726Z - 302100Z

SUMMARY...Locally high rain rates will likely continue for at
least another 1-2 hours, possibly extending through 21Z (4 PM CDT)
for portions of eastern TX. Hourly rainfall of 1 to 2 inches will
be most likely, though the potential for higher hourly totals in
excess of 2 to 3 inches will remain a concern.

DISCUSSION...Localized heavy rain continued over eastern TX as of
17Z with one cluster over the Piney Woods region and a second a
little east of Dallas. Convergence along an elevated boundary,
located in the 925-850 mb layer, was focusing slow moving
thunderstorms with MRMS-derived hourly rainfall of 2-3 inches
(Piney Woods) and 1-2 inches (east of Dallas).

Near Dallas, a 925-850 mb low has formed with slow forecast
movement toward the east, along with localized low level
convergence and thunderstorms likely to continue ahead of the low
track. Meanwhile, RAP forecasts have been consistent with
near-dissipation of the low level convergence axis that extended
southeastward from near Dallas into far southwestern LA within the
next 2-3 hours which should allow for a disruption to the ongoing
areas of heavy rain over the Piney Woods region..

However, visible satellite imagery showed growing cumulus along
the upper TX coast into Montgomery and Liberty counties. Here,
MLCAPE was estimated to be 1000-2000 J/kg along with 2.1 to 2.4
inches of precipitable water. A few slow moving thunderstorms are
likely to develop over the next couple of hours with slow movement
given weak deeper layer mean flow over central TX to the upper TX
coast.

While flash flooding is considered likely in the short term for
locations farther north, the flash flood threat related to
expected thunderstorms over the TX Coastal Plain is less certain
and may remain highly isolated. For these southern areas, the
greatest flash flood threat will likely setup where overlap occurs
with nearby urban areas, possibly including the Houston metro.

Otto

...Please see https://urldefense.com/v3/__http://www.wpc.ncep.noaa.gov__;!!= DZ3fjg!-H840MKsCSJsq8tXAMNnMy9Y2m50mafY4M9FLn4ANn9GM2yTsayuFXuNG-K0JBZY1XL9= ConEDibHgOKbm47-XpgRldg$ for graphic product...

ATTN...WFO...FWD...HGX...LCH...OUN...SHV...

ATTN...RFC...FWR...ORN...TUA...NWC...

LAT...LON 33689635 33419524 32579447 31529388 30529376=20
30109384 29459420 29129487 28789578 29109599=20
29719611 30839614 31679632 32259668 32699715=20
33439715=20

=3D =3D =3D
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AWUS01 KWNH 301806
FFGMPD
TXZ000-NMZ000-310005-

Mesoscale Precipitation Discussion 1034
NWS Weather Prediction Center College Park MD
205 PM EDT Sat Aug 30 2025

Areas affected...southeastern MM into far western TX

Concerning...Heavy rainfall...Flash flooding possible

Valid 301805Z - 310005Z

SUMMARY...Scattered thunderstorms are expected to develop over
southeastern MM into far western TX over the next few hours. Slow
movement and brief backbuilding/training will pose a flash flood
threat from 1-2 in/hr rain rates through 00Z (7 PM CDT).

DISCUSSION...Visible satellite imagery at 1745Z showed building
cumulus over the Sacramento Mountains with mostly clear skies
surrounding much of NM into western TX. Moisture profiles are a
bit higher for southeastern NM into western TX compared to
yesterday and the 12Z soundings from ELP and MAF showed PW values
near the 95th percentile for the end of August. The region resided
on the northern/northwestern edge of a mid to upper-level ridge
centered over northern Mexico into TX, with 0-6 km AGL layer winds
only about 5 kt (slightly weaker into the Big Bend region of TX),
which will result in slow storm motions.

Continued heating is expected to allow MLCAPE values to rise into
the 500-1500 J/kg range by 21Z across southeastern NM and
southward into western TX. Scattered thunderstorms are expected to
develop within the areas of higher terrain first, and then advance
eastward into southern portions of the southern High Plains where
surface dewpoints ranged from the lower to upper 60s. At the
surface, winds had an easterly component on the cool side of a
stationary front which draped westward and then northward through
far western TX which should add an upslope component to the setup.
A few areas of flash flooding from 1-2 inches of rain in an hour
or less will be possible from portions of southeastern NM into the
Trans Pecos and Big Bend regions of TX through 00Z.

Otto

...Please see https://urldefense.com/v3/__http://www.wpc.ncep.noaa.gov__;!!= DZ3fjg!-yoEGOpjSGKau48O81mHtQRWZ16Pl82ytWBn1UT0fBvWVMhyQgvh1dGejdULdaxz59LF= UQG_Mldsm5Ni4YXuf1h05hg$ for graphic product...

ATTN...WFO...ABQ...EPZ...LUB...MAF...

ATTN...RFC...FWR...NWC...

LAT...LON 34850481 34210342 33390287 31750284 30050267=20
29100287 29010374 29480473 30520547 31210655=20
32070690 34390642=20

=3D =3D =3D
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AWUS01 KWNH 310049
FFGMPD
TXZ000-OKZ000-NMZ000-310643-

Mesoscale Precipitation Discussion 1035
NWS Weather Prediction Center College Park MD
848 PM EDT Sat Aug 30 2025

Areas affected...a large part of west Texas, portions of eastern
New Mexico, and the Oklahoma Panhandle

Concerning...Heavy rainfall...Flash flooding possible

Valid 310043Z - 310643Z

Summary...Isolated flash flood potential exists, although the
extent of this threat will depend on convective coverage and
evolution through 06Z/1a CDT.

Discussion...Isolated to scattered convection continues across the
discussion area this evening. The greatest concentration of
storms exists over southwest Texas (near/southwest of Fort
Stockton), where slow-moving storms have evolved into a linear
structure/small complex. Additional storms were located near
Roswell, north of Lubbock, and in the northeastern Texas Panhandle
near Canadian and Perryton. The cells were in a favorable
environment for flash flooding, with 1000+ J/kg MLCAPE persisting
despite a loss of daytime heating. PW values of 1.5 inch (highest
across eastern portions of the discussion) were also favoring
heavy rain, while weak steering flow aloft (generally less than 10
knots) was fostering slow storm motions and local rain rates
exceeding 1 inch/hr at times. A few of these cells were
persisting in sensitive terrain (across southwest Texas), while
others were falling over areas of the Texas South Plains that
received 2-5 inch rainfall totals last night and have current FFG
thresholds in the 1-1.5 inch/hr range). Ground conditions are
somewhat more susceptible to runoff compared to yesterday.

The overall flash flood threat this evening will depend on the
coverage of convection over the next 6 hours. Some uptick of
coverage has been noted over the past hour areawide, although
sources of forcing for ascent are not obvious per mesoanalyses and
satellite imagery. Nevertheless, CAMs remain persistent on at
least isolated coverage of storms, and an isolated flash flood
risk seems apparent.

Cook

...Please see https://urldefense.com/v3/__http://www.wpc.ncep.noaa.gov__;!!= DZ3fjg!9sGj2Jymt3GSqw6dfBiYSgSss8COU6QxHw0xD4XYUToQInKa7_WrjnGGPFyzium1mZZ8= 1iDSHj2vbFGtoyGyi7lRvHg$ for graphic product...

ATTN...WFO...ABQ...AMA...EPZ...EWX...LUB...MAF...OUN...SJT...

ATTN...RFC...FWR...TUA...NWC...

LAT...LON 36600140 36519997 34830014 31890104 30660056=20
30010209 29140332 29590428 30090449 31090422=20
31970503 32630568 35250531 36480441=20

=3D =3D =3D
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AWUS01 KWNH 310803
FFGMPD
TXZ000-NMZ000-311230-

Mesoscale Precipitation Discussion 1036
NWS Weather Prediction Center College Park MD
401 AM EDT Sun Aug 31 2025

Areas affected...Eastern NM...Far Western TX

Concerning...Heavy rainfall...Flash flooding possible

Valid 310800Z - 311230Z

SUMMARY...Additional broken clusters of heavy showers and
thunderstorms going through the early morning hours may continue
to pose an isolated threat for flash flooding.

DISCUSSION...The latest GOES-W IR satellite imagery along with
radar shows a few broken clusters of heavy showers and
thunderstorms continuing to settle gradually down to the south
across mainly the open plains of eastern NM and a small part of
western TX.

The convection is still be driven by a couple of smaller scale
corridors of favorable moisture convergence along with some
lingering instability. The latest MUCAPE values across eastern NM
are still as high as 1000 J/kg in spots. This coupled with some
modest right-entrance region upper-level jet support may tend to
sustain these convective clusters at least going into the early
morning hours.

Rainfall rates may reach as high as 1.5 inches/hour with the
stronger storms, and with relatively slow cell-motions, there may
be a few localized rainfall amounts reaching upwards of 2 to 3
inches. This may support an isolated threat for some additional
flash flooding. However, this threat should diminish early this
morning as the remaining instability continues to wane.

Orrison

...Please see https://urldefense.com/v3/__http://www.wpc.ncep.noaa.gov__;!!= DZ3fjg!84GGkr52-rZCCmaNbsroIxBdsH8yuGaSJHrzhwiF5I31zs1L1hUWUxbModLsTgLlukcW= fey-dFtudbowEU-qxIOG7UA$ for graphic product...

ATTN...WFO...ABQ...EPZ...LUB...MAF...

ATTN...RFC...FWR...TUA...NWC...

LAT...LON 35060355 34710303 34010270 33000265 32230307=20
31980407 32250505 32880536 33990527 34630479=20
34950428=20

=3D =3D =3D
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AWUS01 KWNH 310942
FFGMPD
TXZ000-311540-

Mesoscale Precipitation Discussion 1037
NWS Weather Prediction Center College Park MD
540 AM EDT Sun Aug 31 2025

Areas affected...Portions of Central and Eastern TX

Concerning...Heavy rainfall...Flash flooding possible

Valid 310940Z - 311540Z

SUMMARY...A gradual increase in shower and some thunderstorm
activity is expected over the next few hours. High rainfall rates
and concerns for areas of cell-training will pose a threat for
isolated to scattered areas of flash flooding this morning.

DISCUSSION...Radar and satellite imagery early this morning is
showing a gradual increase in shower and thunderstorm activity
across portions of central and eastern TX. The convection which is
notably elevated in nature to the north of a stationary front is
being facilitated by a gradual increase in warm air advection
along with an uptick in low-level moisture convergence. MUCAPE
values are on the order of about 500 to 1000 J/kg.

Some additional expansion of convection is expected going through
the morning hours as some weakly divergent flow aloft along with
modestly convergent low-level flow in the 925/850 mb layer
interacts with the available pool of instability. The environment
is very moist with PWs of 2.0 to 2.2 inches and this should
support convection with high rainfall rates capable of reaching
1.5 to 2.5 inches/hour.

Rather slow cell-motions given the weak mean layer steering flow
coupled with the linear nature of some of the elevated convection
will potentially result in some rather heavy rainfall totals at
least locally this morning. Areas where any cell-training occurs
may see as much as 3 to 5 inches of rain given the deep moist
environment, and these rains will be enough to result in concerns
for isolated to scattered areas of flash flooding.

Orrison

...Please see https://urldefense.com/v3/__http://www.wpc.ncep.noaa.gov__;!!= DZ3fjg!8zTpTjFBN7L4mjThMsnoIdB_NIlWt1QuvRRgKUq6tlJYEOON3rhigTQvGyA1ke4t8Ef5= e4CRMaYrrbKkvYnb3YUHZeU$ for graphic product...

ATTN...WFO...EWX...FWD...HGX...LCH...SHV...SJT...

ATTN...RFC...FWR...NWC...

LAT...LON 32279631 32229530 31949430 31559393 31059404=20
30759486 30679595 30709679 30779781 31099921=20
31599929 31969851 32249729=20

=3D =3D =3D
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AWUS01 KWNH 311647
FFGMPD
TXZ000-312100-

Mesoscale Precipitation Discussion 1038
NWS Weather Prediction Center College Park MD
1246 PM EDT Sun Aug 31 2025

Areas affected...southeastern TX

Concerning...Heavy rainfall...Flash flooding possible

Valid 311645Z - 312100Z

SUMMARY...Isolated, mostly urban, flash flooding will be possible
across portions of southeastern TX over the next 3-4 hours with
hourly rainfall of 1 to 3 inches.

DISCUSSION...Widely scattered showers and thunderstorms were
beginning to form over the southeastern TX Coastal Plain as of
1620Z, in advance of a small, forward propagating MCS located in
the College Station/Huntsville vicinity of southeastern/eastern
TX. An MCV was apparent near I-45, tracking toward the ESE into an
instability minimum estimated over east TX. Therefore, there is no
significant concern of flash flooding for locations near the
Sabine River which has received heavy rain yesterday. However, the
strongest convection was located along the southern flank of the
MCS in the form of a forward propagating linear segment, advancing
toward the south at roughly 20 kt, into a region containing
1000-2000 J/kg MLCAPE and 2.3 to 2.5 inch PWATs via 16Z SPC
mesoanalysis data.

The unstable environment and mesoscale boundary interactions
should contribute to at least isolated additional convective
development between the Gulf Coast and southward advancing line of thunderstorms from the MCS over the next few hours. Deeper layer
mean winds were quite weak from roughly I-10 and southward, at ~5
kt, which will contribute to slow cell motions in advance of the
propagating MCS. There will be an isolated flash flood concern
where slow moving cells are overtaken by the gradually weakening,
but still notable, propagating line of thunderstorms where 1 to 3
inches of rain in an hour will be possible. Overlap of these
higher rates with urban locations, including the Houston metro,
may lead to isolated flash flooding through 21Z.

Otto

...Please see https://urldefense.com/v3/__http://www.wpc.ncep.noaa.gov__;!!= DZ3fjg!7PDV2hPP86BUOtrG4Iw8GzA-qLFND4vfN_37s-6oCiNocSyHEHA2oxoIJBTa09UX6zXw= _LGiOTRniZimIUzDsUDydUg$ for graphic product...

ATTN...WFO...EWX...HGX...LCH...

ATTN...RFC...FWR...NWC...

LAT...LON 30739468 29749411 29069466 28649568 28799648=20
29519697 30129681 30649580=20

=3D =3D =3D
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AWUS01 KWNH 311813
FFGMPD
TXZ000-010012-

Mesoscale Precipitation Discussion 1039
NWS Weather Prediction Center College Park MD
212 PM EDT Sun Aug 31 2025

Areas affected...portions of central and south Texas

Concerning...Heavy rainfall...Flash flooding likely

Valid 311812Z - 010012Z

Summary...Areas of heavy downpours should become more numerous
while developing southward toward the I-10 corridor and Rio Grande
Valley through the afternoon. 1-3 inch/hr rain rates may cause a
few instances of flash flooding through 00Z/7pm CDT.

Discussion...Per 18Z radar mosaic imagery, scattered showers and
thunderstorms were ongoing and focused along a couple of axes - 1)
along a weak stationary surface front extending from near Fort
Stockton eastward to near Llano that intersects with 2) an outflow
boundary from Llano southeastward to near Houston. The cells
along these boundaries were forming due to abundant surface
heating and convergence. The cells were also in an abundantly
moist (1.8+ PW) and unstable (1000+ J/kg) environment, supporting
robust updrafts and efficient rainfall rates. Recent MRMS imagery
estimated spots of 1-3 inch/hr rain rates near Brady and San Saba
(east of San Angelo), and a couple spots of FFG exceedence have
already been noted in that area. These trends aren't a particular
surprise given the moisture profiles and weak steering flow aloft,
favoring slow storm motions.

Both models and observations depict a gradual increase in coverage
of storms through the afternoon and early evening. The increase
in convective coverage should promote eventual clusters of storms
that slowly propagate southward - especially across central Texas
and vicinity. Rain rates exceeding 1 inch/hr should become
common, and localized spots of 2-3 inch/hr rain rates should
materialize while locally exceeding areal FFG thresholds.

Given the aforementioned scenario, a few instances of flash
flooding are expected - especially as storms migrate through the
Hill Country and urbanized areas near Austin and San Antonio.

Cook

...Please see https://urldefense.com/v3/__http://www.wpc.ncep.noaa.gov__;!!= DZ3fjg!_uSGoX9_KCWvAtbQO0ebifGTpb-DfUyJGf9YKQ53XGuoCDXKVahQfFMWT1R8tCgrnOek= gR9xUCgsjFp_FRuCRZKwpDk$ for graphic product...

ATTN...WFO...EWX...FWD...HGX...MAF...SJT...

ATTN...RFC...FWR...NWC...

LAT...LON 32319910 31699771 30499665 29409672 28869822=20
28930060 29820170 29750330 30040379 30830342=20
31510192=20

=3D =3D =3D
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AWUS01 KWNH 311817
FFGMPD
TXZ000-NMZ000-AZZ000-010015-

Mesoscale Precipitation Discussion 1040
NWS Weather Prediction Center College Park MD
216 PM EDT Sun Aug 31 2025

Areas affected...far western TX into central to southwestern NM
and southeastern AZ

Concerning...Heavy rainfall...Flash flooding likely

Valid 311815Z - 010015Z

SUMMARY...Thunderstorms will pose an isolated to scattered flash
flood threat across portions of far western TX into central to
southwestern NM and southeastern AZ through 00Z. Storms should be
disorganized in nature, but some slow movement and brief training
will carry a threat for 1-2 in/hr rain rates.

DISCUSSION...Visible satellite and radar imagery at 18Z showed a
gradual uptick in the coverage of thunderstorms, tied to the
diurnal cycle, over the southwestern quadrant of NM. Mostly clear
skies and anomalous moisture (12Z EPZ sounding with a PW of 1.3
inches, just above the 90th percentile for the end of August) was
contributing to a bubble of higher instability from near El Paso
into southwestern NM with 500 to 1500+ J/kg MLCAPE shown on the
18Z SPC mesoanalysis page. Moisture values were closer to average
for northern NM and into western AZ.

A 700-500 mb ridge was centered over the AZ/NM border with
easterly low level flow located from far western TX into southern
NM and this pattern will maintain through the late evening. A
small region of weak deeper layer mean winds was located over
south-central TX with (<10 kt 0-6 km) with 10-15 kt located
elsewhere. Continued heating and moisture advection into
southeastern AZ should allow for an expansion of instability with
500-1500 J/kg becoming widespread across southwestern NM into
southeastern AZ by 21-00Z. Low level easterly winds should cause
an increase in low level moisture and instability into
southeastern AZ by late this afternoon with thunderstorms either
moving into or developing over southeastern AZ. Some thunderstorms
will carry the potential for brief training along with slow
movement, supportive of 1-2 in/hr rain rates. At least an isolated
threat of flash flooding may continue beyond 00Z within lingering
instability but the flash flood threat is expected to begin to
wane after sunset.

Otto

...Please see https://urldefense.com/v3/__http://www.wpc.ncep.noaa.gov__;!!= DZ3fjg!4FB4A-G_uJXn_4vF618PbD-HzSbqiloOX0B5-1YanIYCJp0Vu6swWV2DPzPbuT7xm07v= EDpG6RBn0U2e2ROgtoOmr3g$ for graphic product...

ATTN...WFO...ABQ...EPZ...FGZ...TWC...

ATTN...RFC...FWR...STR...NWC...

LAT...LON 34840748 34660549 33920502 32410525 31410603=20
31320750 31030917 31341101 33500982 34340905=20
34670834=20

=3D =3D =3D
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AWUS01 KWNH 010007
FFGMPD
TXZ000-NMZ000-010430-

Mesoscale Precipitation Discussion 1041
NWS Weather Prediction Center College Park MD
806 PM EDT Sun Aug 31 2025

Areas affected...portions of south and west Texas

Concerning...Heavy rainfall...Flash flooding possible

Valid 010006Z - 010430Z

Summary...Flash flood potential should linger for a few more hours
- especially where instability continues to support new,
slow-moving convection.

Discussion...Earlier convection across central Texas and the Hill
Country has evolved into a slow-moving complex currently near the
San Antonio Metro area. Enough downstream instability exists for
cells to continue to produce areas of 1-2 inch/hr rain rates.=20
These cells will continue to move southward over the next couple
hours while producing locally heavy rainfall over urbanized areas.
Excessive runoff/flash flood potential remains a distinct
possibility with this activity through 02Z/9p CDT.

Upstream, a large area of relatively stable air as developed
across the Hill Country due to prior convection. A few areas
farther west (from near Midland southward to the Big Bend area)
have still yet to stabilize, however, and deep, slow-moving
convection continues to exhibit an uptick per radar mosaic and
satellite imagery. Areas of 1-2 inch/hr rain rates remain likely
beneath the stronger and more persistent convection, and these
rates should threaten local FFG thresholds that are as low as
1-1.5 inch/hr. Isolated flash flood potential continues -
especially in low-lying/sensitive areas.

Eventually, storms should exhibit a slow weakening trend with loss
of surface heating, although weak/subtle mid-level waves should
provide enough ascent for locally heavy rainfall to persist
perhaps through 05Z/midnight CDT. where convective overturning has
not led to low-level stabilization.

Flash flooding remains possible across the area through 04-05Z.

Cook

...Please see https://urldefense.com/v3/__http://www.wpc.ncep.noaa.gov__;!!= DZ3fjg!_GLJXiunUX-ITyF353IcS69a7KavcWCvu-jriG0IDE6rllJBXybg_DSjV0ixnLnC9wRI= xSZOHmUvgdOQVuJaUm7HRFc$ for graphic product...

ATTN...WFO...CRP...EWX...MAF...SJT...

ATTN...RFC...FWR...NWC...

LAT...LON 32080276 31760178 30830060 30029904 29749730=20
28869750 28439976 28820068 29670205 29590288=20
29880397 30980453 31840402=20

=3D =3D =3D
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AWUS01 KWNH 010228
FFGMPD
TXZ000-OKZ000-010630-

Mesoscale Precipitation Discussion 1042
NWS Weather Prediction Center College Park MD
1027 PM EDT Sun Aug 31 2025

Areas affected...Far Southern OK...North-Central TX

Concerning...Heavy rainfall...Flash flooding possible

Valid 010227Z - 010630Z

SUMMARY...Additional slow-moving and locally training areas of
heavy showers and thunderstorms are expected to continue through
midnight across portions of southern OK and north-central TX,
including portions of the Dallas-Fort Worth metropolitan area.
Urban flash flooding in particular will continue to be a concern
in the near-term.

DISCUSSION...The latest radar imagery shows slow-moving clusters
of heavy showers and thunderstorms across portions of far southern
OK and north-central TX, including the Dallas-Fort Worth
metropolitan area where more recently there has been some
cell-training noted along with reports of flash flooding.

The convection is largely being driven by proximity of a weak area
of low pressure and a surface trough which is helping to focus
small scale areas of favorable low-level moisture convergence
within a moderately unstable airmass characterized by MLCAPE
values of 1000 to 1500 J/kg. PWs are generally on the order of
1.75 to 2 inches, which coupled with the instability is helping to
drive rainfall rates of up to 2 to 3 inches/hour with the stronger
storms.

Some of the 18Z HREF and recent HRRR guidance suggests some
localized persistence of the convective threat going through
midnight, with locally an additional 3 to 4 inches of rain
possible in close proximity to this weak area of low pressure
which is nearly stationary.

As a result, additional areas of flash flooding will be possible
over the next few hours, and especially for the urban corridors
around the Dallas-Fort Worth metropolitan area.

Orrison

...Please see https://urldefense.com/v3/__http://www.wpc.ncep.noaa.gov__;!!= DZ3fjg!6ERzaNTAHLFG5BlVXLZDSF835s0mhsyLYw_r0JLHuGzhacm85Jt-ayEMJqOmPp8fXKqR= xpfumN8ed_QfgVnEXw2HyXc$ for graphic product...

ATTN...WFO...FWD...OUN...SHV...TSA...

ATTN...RFC...FWR...ORN...TUA...NWC...

LAT...LON 34479577 34029533 33039544 32279617 32219710=20
32629778 33609801 34259755 34339663=20

=3D =3D =3D
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AWUS01 KWNH 010654
FFGMPD
IAZ000-NEZ000-011245-

Mesoscale Precipitation Discussion 1043
NWS Weather Prediction Center College Park MD
252 AM EDT Mon Sep 01 2025

Areas affected...Eastern NE

Concerning...Heavy rainfall...Flash flooding possible

Valid 010652Z - 011245Z

SUMMARY...A couple of slow-moving and locally training bands of
heavy showers are expected over eastern NE going through dawn.
Some areas of flash flooding will be possible.

DISCUSSION...The latest GOES-E WV suite shows a somewhat elongated
mid-level trough axis over the central Plains, with a couple of
embedded compact vort centers. One such vort center is nearly
stationary over eastern NE and has been fostering an uptick in
heavy shower activity over the last 1 to 2 hours.

The cloud tops with this convection are relatively warm/shallow
and suggestive of a warm rain environment that will be conducive
for more efficient rainfall processes for elevated rainfall rates.

On a small scale, there is a favorable corridor moisture
convergence wrapping up around the eastern flank of the vort
center, with an environment that is only modestly unstable. In
fact, the MUCAPE values are only about 500 J/kg.

Regardless, there is sufficient mid-level forcing/ascent working
in tandem with the low-level south to southeast flow and
instability for the convection to initiate and locally expand in
coverage. Some additional nocturnal contraction/tightening of the
low to mid-level circulation is expected over the next few hours
and this may help to further concentrate these smaller scale bands
of shallow-topped convection.

The rainfall rates will be capable of reaching 1 to 2 inches/hour
given the efficient environment, and with slow cell-motions and
cell-training concerns, some rainfall totals going through dawn
may reach as high as 3 to 4+ inches. The HRRR guidance is trending
gradually wetter across eastern NE, and the radar and satellite
trends would tend to favor these locally heavier totals
materializing.

Some areas of flash flooding will be possible across eastern NE
given these rains. However, the antecedent conditions are quite
dry, so the overall flash flooding threat should tend to be
isolated and confined to where any cell-training occurs.

Orrison

...Please see https://urldefense.com/v3/__http://www.wpc.ncep.noaa.gov__;!!= DZ3fjg!4V3pimRcGExDSSqfIuNmbuBbB6uIO1yFUN-onu0tuzdUWBJIv9PJHIO0YC7mOsGalnIt= HAY6XlJObvvBCBvKEixxMwE$ for graphic product...

ATTN...WFO...FSD...GID...OAX...

ATTN...RFC...KRF...NWC...

LAT...LON 42519678 42329640 41989608 41059604 40219662=20
40029759 40379782 40979744 41449734 41859727=20
42349727=20

=3D =3D =3D
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AWUS01 KWNH 032026
FFGMPD
AZZ000-UTZ000-NVZ000-040200-

Mesoscale Precipitation Discussion 1044
NWS Weather Prediction Center College Park MD
426 PM EDT Wed Sep 03 2025

Areas affected...much of northern AZ into southern NV and
southwest UT

Concerning...Heavy rainfall...Flash flooding possible

Valid 032025Z - 040200Z

Summary...Sub-hourly (15-30 min) rainfall of 1"+ with short-term
totals of 1.5-2.5" may result in localized/isolated instances of
flash flooding.

Discussion...Complex upper-level pattern (slow moving
trough/closed low to the west with poleward advancement of
Hurricane Lorena to the south resulting in enhanced upper-level
diffluence in left-exit region of sub-tropical jet streak)
combined with anomalous tropospheric moisture content (at or near
90th percetile) is resulting in a favorable environment for heavy
rainfall across the greater AZ/NV/NM border region. Convection is
initiating and proliferating in the vicinity of the higher terrain
of the Mogollon Rim and Grand Canyon region (where the best low-
to mid-level moisture is overlapping with upper-level moisture,
per CIRA ALPW imagery). MRMS is indicating high instantaneous
rainfall rates (2"+/hr) with initial downdrafts, resulting in
sub-hourly (15-30 min) localized accumulations of 1"+.

As convection continues to proliferate and move relatively slowly
(~10 kts) towards the north-northwest with mean 850-300 mb flow,
cells may locally train to result in localized short-term totals
of 1.5-2.5" (supported by HREF and experimental RRFS neighborhood
probabilities for 1" and 2" exceedance). While these higher
localized totals are most likely in the vicinity of the higher
terrain, the influence of upper-level dynamics may be enough to
support updrafts beyond the typical pulse convection life cycle as
they drift northward. Isolated/localized instances of flash
flooding will be possible.

Churchill

...Please see https://urldefense.com/v3/__http://www.wpc.ncep.noaa.gov__;!!= DZ3fjg!-CgLUwbUCk-Q701BInwzrz1V5k5eT7UICoZ_2V0MvKB4lSy7FZT4Ukf_zt27CarWQ71U= f5ipgi1gohLdkgNfoqtpJAE$ for graphic product...

ATTN...WFO...FGZ...GJT...LKN...SLC...VEF...

ATTN...RFC...RSA...STR...NWC...

LAT...LON 39121195 38381138 37911132 37491128 37211104=20
37191067 37121031 36860999 36590964 36230947=20
35730956 35590991 35591017 35411027 35161042=20
34641028 34351048 34251099 34261152 34221195=20
34251243 34481290 34871342 34901402 35371455=20
35941515 36191566 36611588 37131599 37461630=20
37221699 37851717 38411671 38341529 38781497=20
38891414 38791283=20

=3D =3D =3D
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AWUS01 KWNH 040839
FFGMPD
TNZ000-KYZ000-041338-

Mesoscale Precipitation Discussion 1045
NWS Weather Prediction Center College Park MD
439 AM EDT Thu Sep 04 2025

Areas affected...portions of Kentucky

Concerning...Heavy rainfall...Flash flooding possible

Valid 040838Z - 041338Z

Summary...A few spots of 1-2 inch/hr rain rates have materialized
near/east of Owensboro over the past hour. Isolated flash flood
potential could materialize as the convection reaches
central/eastern portions of the state.

Discussion...Latest radar mosaic imagery depicts areas of training
convection across northern Kentucky near/east of Owensboro.=20
Localized training has led to rain rates exceeding 2 inches/per
(estimated per MRMS). The training storms have materialized amid
strong forcing aloft, with vigorous mid-level waves rotating
through the base of a larger-scale trough over Indiana and
Illinois. Furthermore, strong 850mb flow has maintained enough
low-level flux of moisture/instability into the region to maintain
around 500 J/kg MLCAPE amid low 60s F dewpoints. The orientation
of convergence and cell development (with storms repeatedly
deepening along a surface front near Owensboro and moving quickly
eastward) is favoring areas of training.

The axis of heaviest rainfall is occurring over relatively dry
ground conditions from a lack of rain over the past couple weeks.
Eventually, training convection will reach areas of eastern
Kentucky that have been wetter and are more susceptible to flash
flooding. Instability profiles are expected to gradually
destabilize downstream (per RAP/SPC mesoanalyses), which should
maintain convection downstream while providing opportunity for
continued training and spots of 1-2 inch/hr rain rates. These
rates may exceed FFG thresholds on a localized basis, providing a
brief window for isolated flash flooding through 13Z/9a EDT.

Cook

...Please see https://urldefense.com/v3/__http://www.wpc.ncep.noaa.gov__;!!= DZ3fjg!4PfDzxgmbur0cI0aCVnOyKznsahmvM4kLSvgTRWwOAIyLcsaBg9jmazPZykY-l8cgBqo= 770ZI9eZbWvJmUmdWhnV7BA$ for graphic product...

ATTN...WFO...JKL...LMK...MRX...

ATTN...RFC...TIR...NWC...

LAT...LON 38168424 37908306 37228262 36588439 37008639=20
38138586=20

=3D =3D =3D
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AWUS01 KWNH 042131
FFGMPD
AZZ000-NVZ000-CAZ000-050330-

Mesoscale Precipitation Discussion 1046
NWS Weather Prediction Center College Park MD
529 PM EDT Thu Sep 04 2025

Areas affected...much of AZ into adjacent portions southern CA/NV

Concerning...Heavy rainfall...Flash flooding likely

Valid 042130Z - 050330Z

Summary...Isolated to scattered instances of flash flooding likely
through the evening with the highest localized totals (2-4"
amounts over 3-6 hour period) most likely from far southeastern CA
into southwest and south-central AZ.

Discussion...Monsoonally-driven diurnal convection is once again
proliferating across much of the Southwest this afternoon, fueled
by anomalously high tropospheric moisture content (PWs ranging
from 0.8" in higher terrain to 1.9" in the low deserts, generally
between the 90th percentile and max moving average per FGZ, TUS,
VEF, PHX, and YUM sounding climatology) and ample instability
(SBCAPE of 500-3500 J/kg with SBCIN nearly completely eroded).
While convective initiation has largely focused on the higher
elevations, widely scattered cells are also beginning to fire
across the lower deserts of CA/AZ as well. Upper-level support for
convective organization beyond pulse cells is mixed overall, as a
weak upper-level trough axis (base near the AZ/NV border) is
moderately supportive (via weak DPVA enhancing lift) while a
modestly strengthening sub-tropical jet streak (to ~90 kts at 200
mb by 00z) is unideally positioned with the left-entrance over AZ
(supressing broad lift overall).

Regardless of larger convective organization, locally heavy
downpours (MRMS indicating instantaneous rainfall rates of 2"+
with 15-min rainfall approaching 1" in association with pulse
convection) will drive an isolated to widely scattered flash flood
threat in the near term (and increasing shear could help
prolong/intensify pulse cells). Increasing coverage of pulse
convection will likely drive continued development of new cells
via boundary collisions and mergers, potentially resulting in more
substantial convective organization (i.e. training/repeating
cells) across far southeastern CA into southwest and south-central
AZ over the next 3-6 hours (where 12z hi-res CAMs suggest the
potential for 2-4" localized totals). Isolated to scattered
instances of flash flooding are likely.

Churchill

...Please see https://urldefense.com/v3/__http://www.wpc.ncep.noaa.gov__;!!= DZ3fjg!4NRRKvkAeQSuldYTOgFwr9dC-kpUI1VoTeloEbDrBp9LIkJUF5bcBRA5EwwMywVoo_F4= fn7gJJAeHBWVnyH7-yqlg0Q$ for graphic product...

ATTN...WFO...FGZ...PSR...SGX...TWC...VEF...

ATTN...RFC...RSA...STR...NWC...

LAT...LON 36891177 36821141 36521134 36201132 35821112=20
35351093 35121057 34740999 34660949 34400926=20
33780924 33300936 33000953 32800973 32331024=20
31971044 31511076 31311113 31471192 32001353=20
32541510 32501644 32871668 33401686 33971699=20
34311681 34411586 34941577 35601584 36151596=20
36531582 36671505 36281458 36101426 36031375=20
36001336 36131296 36371253 36481233 36751201=20 =20=20=20=20=20=20=20=20=20=20=20=20

=3D =3D =3D
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AWUS01 KWNH 050831
FFGMPD
AZZ000-UTZ000-NVZ000-CAZ000-051229-

Mesoscale Precipitation Discussion 1047
NWS Weather Prediction Center College Park MD
430 AM EDT Fri Sep 05 2025

Areas affected...southern Nevada, western Arizona

Concerning...Heavy rainfall...Flash flooding possible

Valid 050829Z - 051229Z

Summary...A convective complex should move southward along the
Lower Colorado River Valley for the next few hours. Spots of 1
inch/hr rain rates were prompting flash flood concerns, and these
trends may continue through 12Z/6a MDT/5a PDT.

Discussion...A convective complex has gained organization across
southeastern Nevada this morning. It is currently propagating
southward along a moist/unstable axis (1.25+ PW, 500+ J/kg MLCAPE)
that exists along the immediate Lower Colorado River Valley, which
was likely supporting continued and robust updraft development
along the leading edge of the complex. Ascent from stout
mid-level waves over Utah was also supporting convection, and SPC
mesoanalyses were also suggesting modest enhancement of
low-level/850mb flow/flux into the complex, also supporting its
organization. Spots of 1-1.25 inch/hr rain rates were being
estimated per MRMS, which was readily exceeding FFG thresholds
across the area. At least isolated flash flood concerns are
likely between Las Vegas, Mesquite, and along the NV/AZ border in
the near term.

Each of the aforementioned atmospheric factors supporting
organization will also likely support its persistent for a few
hours this morning. Localized flash flooding is expected with the
complex as it migrates southward from I-15 through Bullhead City
and Kingman, AZ. Southward persistence beyond that area is
possible, and portions of the CA/AZ border region near Lake Havasu
City may also experience a flash flood threat later this morning
(around 10-11Z). Lastly, westward backbuilding into the Las Vegas
metro area (supporting urban flash flood potential) cannot be
completely ruled out.

Cook

...Please see https://urldefense.com/v3/__http://www.wpc.ncep.noaa.gov__;!!= DZ3fjg!9M0eCtUf_hSQGiWe83-1wxMlDWeeHf8xqJbc-4i4gPwcj-av8cQt7S4SlyBHFkagpNiT= HoRq-TVWoxLzKgAxXrEVKnY$ for graphic product...

ATTN...WFO...FGZ...PSR...SLC...VEF...

ATTN...RFC...RSA...STR...NWC...

LAT...LON 37221598 37091383 36621272 34581256 33721353=20
33721499 34721569 36301625=20

=3D =3D =3D
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AWUS01 KWNH 050834
FFGMPD
AZZ000-UTZ000-NVZ000-CAZ000-051229-

Mesoscale Precipitation Discussion 1047
NWS Weather Prediction Center College Park MD
434 AM EDT Fri Sep 05 2025

Areas affected...southern Nevada, western Arizona

Concerning...Heavy rainfall...Flash flooding possible

Valid 050829Z - 051229Z

Summary...A convective complex should move southward along the
Lower Colorado River Valley for the next few hours. Spots of 1
inch/hr rain rates were prompting flash flood concerns, and these
trends may continue through 12Z/6a MDT/5a PDT.

Discussion...A convective complex has gained organization across
southeastern Nevada this morning. It is currently propagating
southward along a moist/unstable axis (1.25+ PW, 500+ J/kg MLCAPE)
that exists along the immediate Lower Colorado River Valley, which
was likely supporting continued and robust updraft development
along the leading edge of the complex. Ascent from stout
mid-level waves over Utah was also supporting convection, and SPC
mesoanalyses were also suggesting modest enhancement of
low-level/850mb flow/flux into the complex, also supporting its
organization. Spots of 1-1.25 inch/hr rain rates were being
estimated per MRMS, which was readily exceeding FFG thresholds
across the area. At least isolated flash flood concerns are
likely between Las Vegas, Mesquite, and along the NV/AZ border in
the near term.

Each of the aforementioned atmospheric factors supporting
organization will also likely support its persistence for a few
hours this morning. Localized flash flooding is expected with the
complex as it migrates southward from I-15 through Bullhead City
and Kingman, AZ. Southward persistence beyond that area is
possible, and portions of the CA/AZ border region near Lake Havasu
City may also experience a flash flood threat later this morning
(around 10-11Z). Lastly, westward backbuilding into the Las Vegas
metro area (supporting urban flash flood potential) cannot be
completely ruled out.

Cook

...Please see https://urldefense.com/v3/__http://www.wpc.ncep.noaa.gov__;!!= DZ3fjg!-_tgIwc_uHeHqcr05UVfy1D_JonvcStOwvKTKr9Xd2OLfw-Jm4Rc6asiP7DnF--xDtmP= u1NgpcNzRuLqPyMBHcFFUxg$ for graphic product...

ATTN...WFO...FGZ...PSR...SLC...VEF...

ATTN...RFC...RSA...STR...NWC...

LAT...LON 37221598 37091383 36621272 34581256 33721353=20
33721499 34721569 36301625=20

=3D =3D =3D
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AWUS01 KWNH 051231
FFGMPD
AZZ000-NVZ000-CAZ000-051630-

Mesoscale Precipitation Discussion 1048
NWS Weather Prediction Center College Park MD
830 AM EDT Fri Sep 05 2025

Areas affected...Lower Colorado River Valley (Western Arizona, Adj California)...

Concerning...Heavy rainfall...Flash flooding possible

Valid 051230Z - 051630Z

SUMMARY...Localized flash flooding threat continues downstream of
slowly weakening MCS/convective clusters within the Lower Colorado
River Valley.=20

DISCUSSION...KESX and GOES-W 10.3um EIR show shrinking convective
complex has had a resent uptick in convective vigor across central
Mohave county. There was a typical weakening trend toward diurnal
minimum, but the leading outflow boundary (combined with
reinforcement from the northeastern dying convection) increased
surface to boundary layer convergence as the cluster was reaching
the nose of the Lower Colorado Valley where lingering unmixed,
conditionally unstable air has been sitting through the overnight
period. MUCIN has been below 25 J/kg and with some southerly weak
flow intersecting the 30-45kt outflow has been sufficient to
reactivate and break through the cap tapping some of the steeper
profiles and 1500-2000 J/kg of ML/MUCAPE. Combine that with
deeper available moisture in lowering elevation and inflow will
continue to support intense sub-hourly rates and localized 1-1.25"
totals.

Most of the Hi-Res CAMs have been traditionally slow to the
forward propagation of the cluster, reducing the moisture
convergence but also delaying arrival to the reservoir of unstable
air further south and have shown the erosion faster. However,
recent RRFS solutions; though still too slow to reality of timing,
do suggest continued southward propagation and longevity through
the next few hours. Still, like any conditionally unstable air,
the updraft strength will require the outflow's convergence to
maintain, but current trends suggest this cluster may continue for
a few more hours and the strength of rates will continue to pose
sub-hourly FFG exceedance and localized flash flooding conditions
along dry washes across the Lower Colorado Valley, mainly east of
the River in Arizona.

Of interest, but perhaps not reaching intensity required for
inducing flash flooding; the rear-inflow jet continues to respond
from NW to SE across south-central NV. Convergence along the
western upstream edge has been similarly sufficient to tap the
steeper mid-level lapse rates for scattered cells. These cells
have favorable orientation for some weak training/repeating; but
also are fairly elevated that evaporative loss may still keep
overall rates/totals just below levels to produce flash flooding,
except if they maintain/track through areas that received heavy
rainfall overnight.

Gallina

...Please see https://urldefense.com/v3/__http://www.wpc.ncep.noaa.gov__;!!= DZ3fjg!8aPH7a1SVnnQEXE9GCnjMwylxvLwnt0T0egP5wxPxB5Ft58ySvQIttC0BDGuTShqMw0b= v46Xr-E3SHgdw7QxcB1nyFY$ for graphic product...

ATTN...WFO...FGZ...PSR...VEF...

ATTN...RFC...RSA...STR...NWC...

LAT...LON 35521375 35161322 34481290 33541266 33011326=20
33041421 33401453 34221475 34751481 35271456=20
35501422=20

=3D =3D =3D
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AWUS01 KWNH 051851
FFGMPD
COZ000-NMZ000-060045-

Mesoscale Precipitation Discussion 1049
NWS Weather Prediction Center College Park MD
250 PM EDT Fri Sep 05 2025

Areas affected...Northern NM & Southern CO

Concerning...Heavy rainfall...Flash flooding possible

Valid 051850Z - 060045Z

SUMMARY...Scattered thunderstorms containing locally Excessive
Rainfall rates may result in flash flooding, especially along
sensitive and rugged terrain.

DISCUSSION...A broad and weak positively-tilted 200-500mb trough
axis is located over the Four Corners region and providing some
minor upper-level ascent aloft. Meanwhile, a cold front is
tracking south and east through the southern High Plains and into
the Front Range of the Rockies. There is some modest ENE low-level
flow in wake of the front that is advecting additional moisture
into the region, evident in RTMA 6-hr dew point changes that are
anywhere from 2-8F higher over eastern NM. In the mid-upper
levels, guidance shows a moist 700-400mb column over southern CO
and into northern NM that is helping to raise low-level RH values
above 80%. This has led to PWATs that are ranging between
0.75-1.0" which are encroaching upon the 90th climatological
percentile. Visible satellite imagery also shows most areas west
of the Continental Divide have witnessed modest surface-based
heating that is supporting 500-1,000 J/kg of SBCAPE per RAP
mesoanalysis. These ingredients are fostering a favorable
environment for rounds of thunderstorms to develop within a moist
and unstable environment that could result in flash flooding this
afternoon.

In terms of antecedent soil moisture conditions, NASA SPoRT-LIS
shows 0-40cm soil moisture guidance has spotty areas of >90th soil
moisture percentiles along the Sangre De Cristo Mountains on south
to the Sacramento Mountains. Some areas are drier and the
thunderstorms will generally provide beneficial rainfall, but
between sensitive soils that are saturated in the higher terrain
and nearby burn scars, there is a chance these thunderstorms that
could generate >1"/hr rainfall rates may result in localized flash
flooding through the early evening hours.

Mullinax

...Please see https://urldefense.com/v3/__http://www.wpc.ncep.noaa.gov__;!!= DZ3fjg!4C4Fe8D4q_beQF3kVNdF4_drAWRz6q3Y7D0rdDM9HAufUndX_S5UC7BxKRZIg2EhOVCX= X_oQM2OesLxu4Hxs3GuCONM$ for graphic product...

ATTN...WFO...ABQ...GJT...PUB...

ATTN...RFC...FWR...STR...TUA...NWC...

LAT...LON 37790671 37710581 37130505 35890461 34720475=20
33550522 33500588 33880628 34670638 35470629=20
35570681 34990747 34920791 35170855 35820866=20
37230873 37720843=20

=3D =3D =3D
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AWUS01 KWNH 052152
FFGMPD
UTZ000-NVZ000-CAZ000-060345-

Mesoscale Precipitation Discussion 1050
NWS Weather Prediction Center College Park MD
551 PM EDT Fri Sep 05 2025

Areas affected...Great Basin & Southwest UT

Concerning...Heavy rainfall...Flash flooding possible

Valid 052150Z - 060345Z

SUMMARY...Numerous thunderstorms capable of producing rainfall
rates around 1"/hr in some cases may lead to additional areas of
flash flooding.

DISCUSSION...A negatively titled 250mb trough over central
California is providing modest upper-level ascent over the
southern Sierra Nevada and Great Basin this afternoon. GOES-19
satellite imagery shows cooling cloud tops aloft as storms tap
into as much as 500 J/kg of MLCAPE per RAP mesoanalysis. In
addition, PWATs are unusually high across the region, topping
0.75" for most areas and thus placing these PWAT values above the
90th climatological percentile. PWATs are closer to 1" in southern
NV and southwest UT. Given the initially strong surface based
heating and synoptic-scale support from the approaching 250mb
trough axis, look for storms to continue into this evening as
emanating outflow boundaries kick-start new storms within the
highlighted region. The available PWATs and MLCAPE should support
maximum hourly rainfall rates around 1"/hr in the most intense
storms. NASA SPoRT-LIS does show some parts of western Nevada and
the eastern slopes of the Sierra Nevada featuring >90th percentile
soil moisture values, so some soils may be rather sensitive to
these heavier rainfall rates. Additional flash flooding is
possible, especially in dry washes and areas with poor drainage.

Mullinax

...Please see https://urldefense.com/v3/__http://www.wpc.ncep.noaa.gov__;!!= DZ3fjg!5c7JB5z5XzZgrfBr-3Resna_Nd1fz-OY-bnCUpGC6iQjuQUM_OkWmeOqi3-KL2mXQ7ZO= FZneN8XdNPBQSSwIn3hpZos$ for graphic product...

ATTN...WFO...LKN...REV...SLC...VEF...

ATTN...RFC...RSA...STR...NWC...

LAT...LON 41241863 40851733 40321599 39231446 38931324=20
38691228 38231182 37351191 37231318 37261432=20
36851583 37051700 37151812 37891890 38531925=20
39721955 40901951=20

=3D =3D =3D
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AWUS01 KWNH 060338
FFGMPD
AZZ000-UTZ000-NVZ000-060936-

Mesoscale Precipitation Discussion 1051
NWS Weather Prediction Center College Park MD
1137 PM EDT Fri Sep 05 2025

Areas affected...southern/southeastern Nevada, far northwestern
Arizona

Concerning...Heavy rainfall...Flash flooding possible

Valid 060336Z - 060936Z

Summary...Flash flooding remains possible along a stalling
boundary in the discussion area through 09Z/3a MDT.

Discussion...Scattered thunderstorms were forming along a stalled
low-level boundary extending from just north of Beatty to just
north of Las Vegas to near Mesquite. The downstream,
pre-convective airmass supporting storms is relatively moist and
unstable, with 1+ inch PW values and 1500 J/kg MLCAPE noted amid
8+ C/km mid-level lapse rates. 850mb flow fields (per SPC
mesoanalysis) continue to depict a slight enhancement to southerly
low-level flow (approaching 20 knots) perpendicular to the
low-level boundary, sustaining updrafts and heavy rainfall. A few
spots of 1 inch/hr rain rates are occurring. These rates exceed
local FFG across the region and are potentially contributing to
excessive runoff.

The overall pattern will evolve slowly through the night, with
sustained convergence expected to continue firing convection
through 09Z. The slow movement and wetting nature of the storms
should continue to promote flash flood potential on at least an
isolated basis during that time. Mesoscale/convective evolution
should result in small displacements in the boundary, and a drift
toward the Las Vegas metro and adjacent areas of far northwestern
Arizona cannot be ruled out. Flash flooding is possible in each
of these areas, with local rainfall amounts of 2 inches expected.

Cook

...Please see https://urldefense.com/v3/__http://www.wpc.ncep.noaa.gov__;!!= DZ3fjg!4EoZjh7ViPJAN2skEFb2luhDp8pzSJ-rWKmvuxyaVK_V-dhvyDa-s7rTpiOzg3sn_c3e= yTOdMsgohMNgUMMjQ_YXmo8$ for graphic product...

ATTN...WFO...FGZ...LKN...SLC...VEF...

ATTN...RFC...RSA...STR...NWC...

LAT...LON 38561744 37751445 36271328 35091363 36261607=20
37531759=20

=3D =3D =3D
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AWUS01 KWNH 060358
FFGMPD
ARZ000-TXZ000-OKZ000-060657-

Mesoscale Precipitation Discussion 1052
NWS Weather Prediction Center College Park MD
1158 PM EDT Fri Sep 05 2025

Areas affected...southern/central Arkansas

Concerning...Heavy rainfall...Flash flooding possible

Valid 060357Z - 060657Z

Summary...Isolated flash flooding is possible with thunderstorm
activity moving eastward across the discussion area.

Discussion...Recent radar mosaic imagery depicts a cluster of
rapidly deepening convection over southwestern Arkansas near
DeQueen forming just ahead of an eastward-propagating complex over
McCurtain County, OK. The cluster of cells in southwestern
Arkansas was moving slowly, with rain rates beginning to eclipse 1
inch/hr in spots. Additionally, incoming rainfall from
southeastern Oklahoma should result in another quick 0.5-1 inch of
rainfall, resulting in local amounts of 2-3 inches in a short
amount of time.

These rain rates are falling on areas that have been relatively
dry, with FFG thresholds hovering around 2-3 inches/hr. Flash
flooding could occur on an isolated basis given the scenario, with low-lying/susceptible areas posing the greatest concern.

The downstream airmass is supportive of continued convection, with
steep lapse rates aloft (7C/km) supporting areas of 3000+ J/kg
MLCAPE along and south of a surface boundary in southern Arkansas.
PW values are also around 1.6+ inch. This airmass and
convergence along/just north of the boundary should continue to
support heavy rainfall as storms move/propagate eastward.

Given the aforementioned scenario, isolated instances of flash
flood potential are possible as spots of 1-2 inch/hr rain rates
spread through central Arkansas. Local amounts of 3 inch totals
are also possible through 08Z/3a CDT

Cook

...Please see https://urldefense.com/v3/__http://www.wpc.ncep.noaa.gov__;!!= DZ3fjg!5brhvbclcIznn8ArH4epTp7q-VBoYUQqu52wAc_Ru7vMIshrLPksY1nfz_ULeuEboSDo= MHx5_3gil5ZEJ15g540eDEk$ for graphic product...

ATTN...WFO...LZK...SHV...

ATTN...RFC...ORN...TUA...NWC...

LAT...LON 34869154 33599149 33399355 33719452 34689430=20
34739325=20

=3D =3D =3D
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AWUS01 KWNH 060932
FFGMPD
AZZ000-NVZ000-CAZ000-061330-

Mesoscale Precipitation Discussion 1053
NWS Weather Prediction Center College Park MD
531 AM EDT Sat Sep 06 2025

Areas affected...southeastern Nevada, western Arizona, far
southeastern California

Concerning...Heavy rainfall...Flash flooding possible

Valid 060930Z - 061330Z

Summary...A long-lived thunderstorm complex should persist for a
few more hours and possibly prompt instances of flash flooding.

Discussion...A long-lived MCS currently extends from near Las
Vegas east to near the Grand Canyon. The complex remains
organized and well positioned within a moist/unstable axis along
the Colorado River Valley (1+ inch PW, 1000 J/kg SBCAPE). Weak
southerly low-level flow was enhancing convergence along the
leading edge of the complex, while mid-level vort maxima were
likely aiding in ascent to help maintain the intensity of the
complex. Areas of 1-2 inch/hr rain rates continue to be estimated
per MRMS beneath the strongest, most persistent activity, which
has likely led to excessive runoff in a few locales (based on MRMS
Flash responses).

Current trends suggest that the complex will continue to drift
southward along the Colorado River into western Arizona along the aforementioned moist/unstable axis. Boundary layer cooling has
been slow to take hold in this area, and point forecast soundings
suggest continued potential for sustained updrafts. Weak
southerly flow at 850mb should also help maintain the MCS for a
few more hours. Gradually weaker mid-level lapse rates exist with
southern extent though, suggesting that the complex may weaken
eventually. The specific timing of the onset of this weakening
trend is uncertain.

Cook

...Please see https://urldefense.com/v3/__http://www.wpc.ncep.noaa.gov__;!!= DZ3fjg!6Vxrhu5q0nQa3eQBDPUhUuJEMCj6hdoA8MKvEEVZtWX_9D_CP_NdVO5kcXjks7DjaZlX= wJWou7iVP2uuMVjlFUegws8$ for graphic product...

ATTN...WFO...FGZ...PSR...VEF...

ATTN...RFC...RSA...STR...NWC...

LAT...LON 36901451 36401339 35161254 33761289 33711463=20
35891527=20

=3D =3D =3D
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AWUS01 KWNH 061713
FFGMPD
MAZ000-NHZ000-VTZ000-CTZ000-NYZ000-NJZ000-PAZ000-DEZ000-MDZ000-062300-

Mesoscale Precipitation Discussion 1054
NWS Weather Prediction Center College Park MD
113 PM EDT Sat Sep 06 2025

Areas affected...northern Mid-Atlantic into southern New England

Concerning...Heavy rainfall...Flash flooding possible

Valid 061712Z - 062300Z

Summary...A couple areas of flash flooding will be possible from
the northern Mid-Atlantic region into southern New England through
23Z. Areas of short term training will be capable of hourly
rainfall from 1 to 2+ inches and spotty 3 inch totals. Given dry
antecedent conditions, the flash flood threat appears to be mostly
urban in nature.

Discussion...17Z observations placed a cold front stretching from
NH/VT into southern NY, eastern PA and central MD. Surface
moisture ahead of this boundary has increased since 12Z with
dewpoints in the low to mid-70s from southeastern PA into parts of
NJ as layered PW imagery showed a swath of deep layered moisture
advecting northeastward from the lower MS Valley. 17Z SPC
mesoanalysis data showed estimated PWs of 1.5 to 1.7 inches and
filtered sunshine has helped to increase MLCAPE into the 1000-2000
J/kg range. Recent visible satellite and radar imagery showed the
beginning stages of convective development along the front from
northeastern MD into northwestern NJ.

There is sufficient vertical shear for organized storms with both
organized and ordinary cells likely containing forward speeds
between 20-35 kt toward the northeast/east-northeast. Largely
unidirectional flow from just above the surface to the tropopause
was oriented parallel to the front which would normally be
supportive of training. However, a steady 10-15 kt progression of
the cold front is forecast which should limit training to
mesoscale waves along the front and/or thunderstorm related
outflow that cause convection to align with the mean wind. This
situation could support 1 to 2+ inches of rain in an hour or less.
Given much of the region has been dry over the past 1-2 weeks, the
flash flood threat should remain mostly tied to overlap of heavy
rain with the urban I-95 corridor and/or some of the surrounding
more flash flood prone areas.

Otto

...Please see https://urldefense.com/v3/__http://www.wpc.ncep.noaa.gov__;!!= DZ3fjg!8Qkd-zBGYYOiMWeSPgxat76eAuBOHHfvjx4z8EbgPUM1lrzCg9G-l9NdmffKtzi7DqYK= u1C2X4utZIE1WrYEr-Y0x4Y$ for graphic product...

ATTN...WFO...ALY...BGM...BOX...CTP...GYX...LWX...OKX...PHI...

ATTN...RFC...RHA...TAR...NWC...

LAT...LON 43037179 42157189 40887301 39907419 39517521=20
39337605 39437645 39877631 40777521 41777425=20
42947297=20

=3D =3D =3D
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AWUS01 KWNH 061827
FFGMPD
TXZ000-NMZ000-AZZ000-070030-

Mesoscale Precipitation Discussion 1055
NWS Weather Prediction Center College Park MD
227 PM EDT Sat Sep 06 2025

Areas affected...Southeast Arizona, Southwest New Mexico

Concerning...Heavy rainfall...Flash flooding possible

Valid 061830Z - 070030Z

Summary...Showers and thunderstorms will expand across portions of
New Mexico and Arizona this afternoon and evening. As convection
intensifies, brief rainfall rates t0 3"/hr are possible resulting
on 0.5-0.75 inches of rain in 15 minutes. This may cause flash
flooding.

Discussion...The GOES-E day-cloud phase micro-physics RGB this
afternoon shows a slow expansion of ice-clouds associated with
strengthening updrafts driving deepening Cb. At this time these
are mostly positioned across southwest NM and focused in higher
terrain, but should expand and move into lower elevations during
the next few hours. Despite some drier air encroaching from the
west noted in the LPW fields, PWs remain 1.25 to 1.5 inches as
measured by GPS, above the 90th percentile for the date, which is
overlapping SBCAPE that is climbing to 1500 J/kg within regions of
clearing. These thermodynamics are supporting the increasing
updrafts, with additional lift being provided by a weak surface
trough analyzed by WPC and a shortwave that will slowly dig
southeast into the evening.

Despite the relatively fresh convection, these storms have already
produced 15-min rainfall as measured by MRMS of 0.3 to 0.4 inches
in the deeper cells. As the afternoon progresses to peak heating,
surface instability may exceed 2000 J/kg, likely causing these
rain rates to become even more intense. Additionally, the
shortwave dropping southeast may help focus some organization
later this afternoon, especially as storms begin to drop off the
terrain and dive E/SE on 0-6km mean winds of around 10 kts. A lack
of significant bulk shear will keep storms generally of the pulse
variety, but in the presence of the increasing ascent and
favorable thermodynamics, residual outflow boundaries will likely
lead to additional development. This could reuslt in storm
mergers/collisions causing rain rates to perk up to as much as
0.75"/15 min as reflected by the HRRR-forced UA WRF precipitation
rate and HRRR 15-min rainfall product.

Although total rainfall in most areas will likely remain below 1
inch, a few repeating rounds are possible which could cause
locally more than 2 inches. While this will enhance the flash
flood risk, it is possible that any of these intense rain rates,
even if short lived, could cause rapid runoff as 3-hr FFG is
generally only around 1 inch in many areas. The HREF exceedance
probabilities for this 3-hr FFG peak as high as 50% in southern
AZ, but any of this heavy rain falling atop vulnerable regions
such as urban areas or burn scars, could experience impacts from
flash flooding into this evening.


Weiss

...Please see https://urldefense.com/v3/__http://www.wpc.ncep.noaa.gov__;!!= DZ3fjg!99dzq7IUQKyvn3avb1hIDqbUdram2GDffIWqvWKCNKp6j-HbkSXA4qySCTl48fUZSWL-= -dyElsTl25kwMa3UEBNEa5Y$ for graphic product...

ATTN...WFO...ABQ...EPZ...FGZ...PSR...TWC...

ATTN...RFC...FWR...STR...NWC...

LAT...LON 34830806 34680675 34470615 34080556 33270529=20
32530539 32000602 31770667 31580729 31390809=20
31270897 31281048 31271092 31441158 31791165=20
32221127 32731077 34350905=20

=3D =3D =3D
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AWUS01 KWNH 070043
FFGMPD
NMZ000-AZZ000-070630-

Mesoscale Precipitation Discussion 1056
NWS Weather Prediction Center College Park MD
843 PM EDT Sat Sep 06 2025

Areas affected...Southern Arizona

Concerning...Heavy rainfall...Flash flooding possible

Valid 070042Z - 070630Z

Summary...Slow moving showers and thunderstorms will continue
across southern Arizona for a few more hours. Heavy rainfall
capable of producing 0.5-0.75 inches in 15 minutes may create
instances of flash flooding.

Discussion...The regional radar mosaic this evening shows
continued development of showers and thunderstorms across much of
Arizona and New Mexico. This convection is forming within
favorable thermodynamics characterized by PWs measured on the TUS
00Z U/A sounding of 1.39 inches (near the 90th percentile for the
date) and 1500 J/kg of SBCAPE. A weak mid-level impulse embedded
in generally westerly flow is helping to drive broad ascent across
the region, while a weak surface convergence axis near the
Mexico/Arizona border, as well as remnant outflow boundaries and
collisions, are aiding to produce the activity this evening.
Although storms moving off the terrain are generally moving
progressively to the E/SE, clusters forming across southern AZ are
slower moving and exhibiting some back building behavior.

As the evening progresses, a local increase in coverage of
convection is progged by many of the available high-res CAMs
across southern Arizona, especially in the vicinity of Pima and
Santa Cruz counties. This will be in response to subtle moisture
convergence on weak 850mb flow along the gradient of some higher
PWs, but also in response to subtle SW drift of convection as
propagation vectors gradually veer into the higher moisture. With
mean 0-6km winds expected to remain light, and propagation vectors
additionally weak, these slow moving storms will linger across
some areas despite being of the pulse variety. The 15-min HRRR and
HRRR forced UA WRF both suggest intense rainfall could reach
0.75"/15 mins, which is additionally supported by 5-10%
neighborhood probabilities for 2"/hr from the HREF. Where these
storms linger, or where multiple rounds can occur, locally as much
as 2-3" of rainfall is possible.

0-10cm soil moisture across southern Arizona is generally below
normal according to NASA SPoRT, although there are some pockets of
wetter soils across the area. Regardless, if these intense rain
rates move atop the natural vulnerability of this region,
especially across any burn scars, urban areas, or sensitive
terrain, instances of flash flooding could result until convective
overturning occurs around 06Z.


Weiss

...Please see https://urldefense.com/v3/__http://www.wpc.ncep.noaa.gov__;!!= DZ3fjg!6XFuW3leIxN2zZrFWyQ7KZ3xRTLQsRnU5yiHnunDMFd-g48O60lLYYZLHGgAKmpRhJMO= TP2EIoC0i8_I9l1P8n1MiS8$ for graphic product...

ATTN...WFO...EPZ...PSR...TWC...

ATTN...RFC...STR...NWC...

LAT...LON 32831100 32830976 32590916 32310900 31800895=20
31390918 31080985 30971061 31141135 31381192=20
31621251 31921300 32251350 32701352 32781264=20 =20=20=20=20=20=20=20=20=20=20=20=20

=3D =3D =3D
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AWUS01 KWNH 070615
FFGMPD
WAZ000-071000-

Mesoscale Precipitation Discussion 1057
NWS Weather Prediction Center College Park MD
214 AM EDT Sun Sep 07 2025

Areas affected...western/central Washington State

Concerning...Heavy rainfall...Flash flooding possible

Valid 070614Z - 071000Z

Summary...An instance or two of flash flooding is possible across
the Pacific Northwest as scattered thunderstorms move
slowly/erratically over the next 2-4 hours. Areas of 1 inch/hr
rain rates are expected.

Discussion...Recent radar mosaic imagery depicts a gradual
expansion in convective coverage across western and central
Washington State currently. The storms are generally moving
northwestward, though weak low-level shear was promoting areas of outflow-driven activity with erratic storm motions. Spots of 1
inch/hr rain rates were being estimated per MRMS with the more
dominant activity, suggesting that flash flooding might occur
especially if that rainfall occurs atop sensitive ground
conditions and/or burn scars. The storms are being supporting by
1) ascent lifting northward around the base of a larger-scale
mid/upper trough over the northeastern Pacific, 2) steep mid-level
lapse rates (generally above 7C/km away from storms), and 3) a
moisture plume across the area, with PW values generally in the
1-1.3 inch range. Each of these factors suggest that an instance
or two of flash flooding might occur as storms move through the
region in the near term.

Models/observations suggest the period of peak flash flood risk
might only extend through 09Z/2a PDT or so. The mid-level
vorticity max helping to force ongoing convection should lift
northward into southwestern Canada, resulting in a minimum in
forcing aloft amid stabilizing low-levels from widespread
rainfall. A limited threat for thunderstorms may exist beyond the
09Z/2a PDT timeframe, and flash flood potential will be reassessed
around that time.

Of note - some of the thunderstorms may also produce dry lightning
and fire starts. Additional information on these threats can be
found at your respective local forecast office (weather.gov) and
SPC fire weather information (spc.noaa.gov).

Cook

...Please see https://urldefense.com/v3/__http://www.wpc.ncep.noaa.gov__;!!= DZ3fjg!6-2GaFK6ln1qD0eK1_sxoe7WzmHRV_M3Au8Pv9bCEzSu2e0My9vEYfPd9g1SNhEkeD76= k6qOHzI6tSmoI5XNYTh_tiI$ for graphic product...

ATTN...WFO...OTX...PDT...PQR...SEW...

ATTN...RFC...PTR...NWC...

LAT...LON 48712153 48411990 47381918 46222023 46612342=20
47952347 48372269=20

=3D =3D =3D
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AWUS01 KWNH 071232
FFGMPD
TXZ000-071800-

Mesoscale Precipitation Discussion 1058
NWS Weather Prediction Center College Park MD
832 AM EDT Sun Sep 07 2025

Areas affected...Western Hill Country & Lower Pecos River Valley
of Texas...

Concerning...Heavy rainfall...Flash flooding likely

Valid 071230Z - 071800Z

SUMMARY...Ongoing flash flooding likely to continue for the
remainder of the morning with very slow moving and surprisingly
efficient rainfall production producing highly focused 2"/hr rates
over sensitive/low FFG terrain. Additional 3-5" totals resulting
in likely focused flash flooding. A spot or two of considerable
and/or significant flash flooding is possible.=20=20

DISCUSSION...Regional RADAR mosaic over the last few hours has
seen a slight uptick in convective activity in both strength and
coverage with the scattered observations indicating surprisingly
efficient rainfall production with 2"/hr rates and some localized
2-5"/3hrs reported resulting in localized flash flooding. The
overall environment is expected to change very little over the
next few hours as cells continue to remain fairly stationary with
small movement.

The overall dynamics has been supportive of the scattered
convective environment, as GOES-E WV shows a very concentric but
broad upper-level ridge across northern Mexico, placing SW TX/Hill
Country into a favorable upper-level divergent pattern at the
entry of a speed max of a jet just east of the 30N100W benchmark.=20
Small northeast quadrant diffluence, but also slightly digging
northern stream influence across the Big Country in combination
with approaching northern stream short-wave feature is combining
to allow for solid evacuation of these thunderstorms. In
addition, the shortwave to providing ascent, has strengthened
surface easteries, though a shallow boundary layer/inversion is
drawing moisture up through the Rio Grande Valley to the Lower
Pecos (per Sfc-850mb LPW animation) and lifting in northward on
850mb flow per VWP in the region. Total deep layer moisture is
lower than expected for such an observed efficient cells; the flux
is most likely loading the lower warm cloud portion with the low
to mid-70s Tds for 2"+/hr rates for the highly focused updrafts
that have developed.=20=20

The vertical shear profile (along with the upstream height-falls)
supports a westerly back-building environment counteracting the
steering flow aloft to result in a fairly stationary nature in the
short-term. As the height-falls/shortwave arrives, a slow
southward motions are likely into the Rio Grande Valley toward
Mexico. Flux up the Rio Grande is expected to continue to keep
slow but efficient rainfall production likely over the next 4-6
hours. As such, spotty 3-5" totals are probable and will result
in focused (scattered in coverage) but potentially considerable
flash flooding conditions (as FFG values are naturally low
1-1.5"/hr & 1.5-2.5"/3hrs) in fairly rugged terrain.

Gallina

...Please see https://urldefense.com/v3/__http://www.wpc.ncep.noaa.gov__;!!= DZ3fjg!5ptKWcbjGgExB-8-QlbZCGkLXWgtuctLuGSmv2P_Qt21At6GM-JSOlf9z_KHR_FAq35s= YCqdFSmK26QpkhzxI_K7JOE$ for graphic product...

ATTN...WFO...EWX...MAF...SJT...

ATTN...RFC...FWR...NWC...

LAT...LON 31120201 31120100 30649929 29949871 29149935=20
28850041 29180092 29640153 29870197 30260236=20
30810241=20

=3D =3D =3D
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