ACUS48 KWNS 220848
SWOD48
SPC AC 220846

Day 4-8 Convective Outlook
NWS Storm Prediction Center Norman OK
0346 AM CDT Fri Aug 22 2025

Valid 251200Z - 301200Z

...DISCUSSION...
...Monday/Day 4 to Wednesday/Day 6...
On Monday, a cyclonic-flow mid-level pattern will be in place across
much of the eastern two-thirds of the nation. Southwesterly flow is
expected over the Northeast, where scattered thunderstorms will be
possible on Monday, mainly in New England. Scattered storms are also
expected to develop in parts of the southern and central Plains
within northwesterly flow. Any severe threat in these two areas will
likely remain localized, mainly due to weak instability.

On Tuesday and Wednesday, a large area of high pressure is forecast
to be in place from the central and northern Plains eastward to the
Atlantic Seaboard. Thunderstorms, non severe in nature, would be
possible each afternoon across parts of the Gulf Coast states and in
the southern and central High Plains, along the southern and western
periphery of the post-frontal airmass.

...Thursday/Day 7 and Friday/Day 8...
From Thursday into Friday, a mid-level low is forecast to form over
the lower Great Lakes, as a large area of surface high pressure
moves slowly eastward across the eastern U.S. Scattered
thunderstorms could form in parts of the southern Plains and High
Plains, but weak instability should limit any severe potential.

..Broyles.. 08/22/2025

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ACUS48 KWNS 230838
SWOD48
SPC AC 230836

Day 4-8 Convective Outlook
NWS Storm Prediction Center Norman OK
0336 AM CDT Sat Aug 23 2025

Valid 261200Z - 311200Z

...DISCUSSION...
...Tuesday/Day 4 to Thursday/Day 6...
A large-scale trough will remain in place across the eastern U.S. on
Tuesday, as an area of surface high pressure remains dominant across
much of the eastern half of the nation. Non-severe thunderstorms may
develop on the western periphery of post-frontal airmass, over parts
of the southern and central High Plains on Tuesday and Wednesday.

On Thursday, low-level moisture return is forecast to take place
across the southern and central Plains. A pocket of moderate
instability will be possible across parts of Oklahoma, where
scattered thunderstorms may develop during the afternoon. In spite
of this, deep-layer shear is forecast to remain relatively weak,
suggesting any severe threat will be marginal.

...Friday/Day 7 and Saturday/Day 8...
From Friday into Saturday, northwesterly mid-level flow will remain
in place over parts of much of the central and eastern part of the
nation. At the surface, a moist airmass will likely be located over
parts of the Gulf Coast states, where scattered thunderstorms will
be possible each day. Deep-layer shear is forecast be relatively
weak across most of the region from Friday into Saturday, suggesting
that any severe threat will remain localized.

..Broyles.. 08/23/2025

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ACUS48 KWNS 240840
SWOD48
SPC AC 240838

Day 4-8 Convective Outlook
NWS Storm Prediction Center Norman OK
0338 AM CDT Sun Aug 24 2025

Valid 271200Z - 011200Z

...DISCUSSION...
...Wednesday/Day 4 to Friday/Day 6...
On Wednesday, a large-scale cyclonic flow pattern is forecast to
remain over the north-central and northeastern U.S., as a mid-level
ridge remains over the southern and central Rockies. Low-level
moisture return is forecast over the southern and central Plains,
where an axis of instability should set up from west Texas into
eastern Colorado by afternoon. Scattered thunderstorms may develop
from near the instability axis eastward across Kansas from late
afternoon into the evening. Weak instability should keep any severe
potential localized.

On Thursday, an axis of moderate instability is forecast to develop
by afternoon across east Texas and eastern Oklahoma. As a mid-level
shortwave trough moves southeastward across the region, isolated
scattered thunderstorms will be possible over much eastern Oklahoma
extending eastward into the Ozarks. Instability and deep-layer shear
should be enough for a marginal severe threat in these areas. This
potential is forecast to shift southward into southeast Texas on
Friday, as a cold front advances toward the Gulf Coast.

...Saturday/Day 7 and Sunday/Day 8...
On Saturday and Sunday, a mid-level ridge is forecast over the
western U.S., as northwesterly flow remains over much of the central
and eastern U.S. An axis of instability may develop over parts of
the southern and central High Plains each afternoon, where isolated thunderstorms will be possible. Any severe threat associated with
the storms is expected to be localized.

..Broyles.. 08/24/2025

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ACUS48 KWNS 250854
SWOD48
SPC AC 250853

Day 4-8 Convective Outlook
NWS Storm Prediction Center Norman OK
0353 AM CDT Mon Aug 25 2025

Valid 281200Z - 021200Z

...DISCUSSION...
...Thursday/Day 4 to Saturday/Day 6...
On Thursday, a large-scale mid-level trough is forecast to be in
place over the eastern U.S., as a ridge remains over the central
Rockies. A pocket of moderate instability could develop in the
Ark-La-Tex Thursday afternoon, near an east-to-west front in the Red
River Valley. Enough deep-layer is forecast for an isolated severe
threat, but some uncertainty exists concerning the magnitude of any
threat.

The front is forecast to move southward into the Gulf Coast states
on Friday. Thunderstorm development will be possible near the front
from east Texas into Louisiana, where an isolated severe threat
could again develop during the afternoon. However, deep-layer shear
is forecast to remain relatively weak, would should keep any severe
threat marginal.

Further northwest on Friday, an axis of instability is forecast
across the southern and central High Plains. Isolated to scattered thunderstorms could develop along and near this axis from late
afternoon into the evening. This same potential will be possible on
Saturday as the instability axis remains in place across the
southern and central High Plains. The combination of instability and
deep-layer shear is forecast to be sufficient for a marginal severe
threat both on Friday and Saturday.

...Sunday/Day 7 and Monday/Day 8...
From Sunday into Monday, a mid-level ridge is forecast to move
eastward across the southern and central Plains. In the wake of this
feature, scattered thunderstorms could develop across the High
Plains near a north-to-south axis of instability. A marginal severe
threat will be possible each afternoon and evening, but deep-layer
shear is forecast remain relatively weak. This should be a limiting
factor concerning any severe potential.

..Broyles.. 08/25/2025

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ACUS48 KWNS 260749
SWOD48
SPC AC 260747

Day 4-8 Convective Outlook
NWS Storm Prediction Center Norman OK
0247 AM CDT Tue Aug 26 2025

Valid 291200Z - 031200Z

...DISCUSSION...
An upper trough will eject into the Atlantic this weekend as weak
upper ridging builds into the central U.S. and an upper-low meanders
over the Pacific Northwest. An upper trough will then develop and
gradually amplify over the Upper MS Valley through early next week.
A surface cold front will sag southward through the day on Day
4/Friday across portions of the southern Plains into the Lower MS
Valley, where rich moisture and appreciable instability will be in
place to support a threat for at least scattered strong
thunderstorms. By the weekend into early next week, surface lee
troughing across the Plains will encourage the northwestward
advection of low-level moisture beneath modest lapse rates,
resulting in marginal to moderate instability across the High Plains
Days 5-8/Saturday-Tuesday. Southeasterly 850 mb winds, overspread by northwesterly flow at 500 mb, may encourage enough wind shear to
support isolated severe storms along the central High Plains
Saturday-Tuesday.

..Squitieri.. 08/26/2025

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ACUS48 KWNS 270752
SWOD48
SPC AC 270751

Day 4-8 Convective Outlook
NWS Storm Prediction Center Norman OK
0251 AM CDT Wed Aug 27 2025

Valid 301200Z - 041200Z

...DISCUSSION...
The upper-low over New England will gradually drift away from the
U.S. as an upper ridge builds west of the Rockies this weekend into
early next week. Surface troughing will persist across the Plains
states, with adequate low-level moisture remaining in place to
support scattered thunderstorms. At the moment, it appears that any
severe risk will be sparse at best. As the upper ridge persists, a
positively tilted upper trough will rapidly translate from Canada
into the MS Valley during the middle of next week, accompanied by a
progressive surface cold front. This cold front will bring a cool,
stable airmass to much of the northern and central Plains into the
MS Valley, reducing thunderstorm potential. Strong storms could
occur immediately ahead of the surface cold front around Day
8/Wednesday, though questions surrounding the placement and timing
of this front preclude the introduction of severe probabilities at
this time.

..Squitieri.. 08/27/2025

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ACUS48 KWNS 280751
SWOD48
SPC AC 280750

Day 4-8 Convective Outlook
NWS Storm Prediction Center Norman OK
0250 AM CDT Thu Aug 28 2025

Valid 311200Z - 051200Z

...DISCUSSION...
Upper troughs will impinge on the West and East Coasts while upper
ridging dominates the Interior West early next week, before a
mid-level trough develops and rapidly amplifies across the eastern
half of the CONUS through the middle of next week. Through the early
part of the week, surface lee troughing, amid weaker deep-layer flow
fields, will support meandering moisture across the central U.S.,
accompanied by thunderstorm chances. As the aforementioned mid-level
trough amplifies, a strong surface cold front will sweep across the
Plains and MS Valley region during the middle of the week, promoting
cool and stable conditions. Given the strength of the cold front, it
is plausible that thunderstorm development should occur given strong
low-level convergence. However, medium-range guidance does not
depict a strong signal of overlapping buoyancy and vertical wind
shear ahead of the cold front, suggesting that if severe potential
exists, the predictability of this potential is too low to warrant probabilities at this time.

..Squitieri.. 08/28/2025

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ACUS48 KWNS 290834
SWOD48
SPC AC 290833

Day 4-8 Convective Outlook
NWS Storm Prediction Center Norman OK
0333 AM CDT Fri Aug 29 2025

Valid 011200Z - 061200Z

...DISCUSSION...
A broad northwesterly upper flow regime will be in place across the
CONUS early this week, before a pronounced mid-level trough
amplifies greatly while tracking across the eastern CONUS through
the remainder of the week. As this occurs, surface low development
is likely around the Great Lakes, with a strong cold front poised to
sweep across the northern Plains to the East Coast during the Days
5-8 (Tuesday-Friday) time frame. Cool and stable conditions will
usher in behind the cold front. However, Gulf moisture may advect north-northeast ahead of the front along the East Coast toward the
end of the week. Assuming forcing for ascent is not purely
anafrontal, it is plausible that at least isolated severe storms
could develop along the East Coast around Days 7-8
(Thursday-Friday). However, confidence in the specific timing and
magnitude of any severe threat this far in advance is too low for
the introduction of severe probabilities at this time.

..Squitieri.. 08/29/2025

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ACUS48 KWNS 300846
SWOD48
SPC AC 300844

Day 4-8 Convective Outlook
NWS Storm Prediction Center Norman OK
0344 AM CDT Sat Aug 30 2025

Valid 021200Z - 071200Z

...DISCUSSION...
A mid-level trough is poised to rapidly amplify while traversing the
eastern U.S. from around mid-week into next weekend, encouraging a
surface cold front to sweep across the northern Plains to the East
Coast Days 4-7 (Tuesday-Friday). Around Day 6 (Thursday), the
surface cold front should encounter richer low-level moisture while
impinging on the Appalachians. Surface dewpoints well into the 60s F
may support MUCAPE around 1000 J/kg. However, much of the stronger
vertical wind shear and associated upper support may potentially lag
the surface cold front. As such, uncertainties remain regarding
severe potential, with no probabilities introduced this outlook.
Nonetheless, it is plausible that a broken band or line of storms
with at least scattered gusty conditions (perhaps damaging winds)
may organize to the immediate lee of the Appalachians on Thursday.
By the weekend, medium-range guidance hints at the possibility of
moisture return to the southern Plains, along with instability,
which may foster isolated severe potential.

..Squitieri.. 08/30/2025

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ACUS48 KWNS 310851
SWOD48
SPC AC 310849

Day 4-8 Convective Outlook
NWS Storm Prediction Center Norman OK
0349 AM CDT Sun Aug 31 2025

Valid 031200Z - 081200Z

...DISCUSSION...
A surface cold front will surge east-southeastward across the Plains
states and the MS Valley Day 4 (Wednesday) before impinging on the
East Coast by Days 5-6 (Thursday-Friday) as a mid-level trough
amplifies over the Great Lakes. Adequate low-level moisture will
precede the cold front, supporting potentially strong thunderstorms
over the southern Plains on Wednesday given favorable overlapping shear/instability. Thereafter, potentially strong thunderstorms may
develop ahead of the cold front over the central/northern
Appalachians into the Hudson River Valley Thursday and Friday as the
cold front encounters progressively richer moisture. The main
limiting factor for a clearer severe threat is the potential for
deep-layer ascent/shear potentially lagging behind the cold front.
Nonetheless, convergence along the surface cold front may still
support enough of a severe threat to warrant probabilities by the
Days 1-3 time frame. Medium-range guidance depicts some moisture
return across the southern Plains by the end of the week into next
weekend, as a second mid-level impulse pivots around the broader
cyclonic flow enveloping the eastern U.S. Should this occur, enough
favorable overlapping buoyancy and shear may support an isolated
severe risk.

..Squitieri.. 08/31/2025

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ACUS48 KWNS 010817
SWOD48
SPC AC 010816

Day 4-8 Convective Outlook
NWS Storm Prediction Center Norman OK
0316 AM CDT Mon Sep 01 2025

Valid 041200Z - 091200Z

...DISCUSSION...
A pronounced mid-level trough will gradually advance eastward across
the eastern U.S. through the remainder of the week into this
weekend, with multiple embedded mid-level perturbations expected to
pivot around the upper trough. The upper trough and associated
impulses will reinforce surface high pressure and cooler air across
much of the U.S. between the Mississippi River and Appalachians
through the extended forecast period. The surface cold front will
encounter seasonably rich low-level moisture while encroaching on
the Eastern Seaboard, prompting the development of at least
scattered thunderstorms. At the moment, the best chance for strong
storms, perhaps accompanied by an isolated severe threat, will be
along the central and northern Appalachians into the Mid Atlantic
within the Days 4-6 (Thursday-Saturday) time frame.

Meanwhile, as surface high pressure builds over the OH/TN Valley
regions, and the Interior West, seasonal moisture return is expected
across parts of the southern Plains due to surface lee troughing.
The aforementioned impulses pivoting around the broader scale upper
trough may graze the southern Plains, perhaps promoting enough
vertical wind shear atop a moist low-level airmass to support
isolated severe thunderstorms Days 4-6 (Thursday-Saturday).

..Squitieri.. 09/01/2025

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ACUS48 KWNS 020835
SWOD48
SPC AC 020834

Day 4-8 Convective Outlook
NWS Storm Prediction Center Norman OK
0334 AM CDT Tue Sep 02 2025

Valid 051200Z - 101200Z

...DISCUSSION...
A pronounced mid-level trough will progress across the Northeast
late this week, ejecting into the Atlantic by the end of the
weekend. Thereafter, a more progressive pattern will ensue, with
multiple mid-level shortwave troughs poised to traverse the CONUS
early into the middle of next week. Despite differences among
medium-range guidance members, there is general agreement that a
surface cold front will encounter seasonal low-level moisture across
the eastern U.S. Days 4-5 (Friday-Saturday), promoting thunderstorm
potential (some of which may be strong). However, any severe threat accompanying these storms is expected to be localized and isolated.
Surface high pressure will then become established from the MS River
Valley eastward, allowing for moisture return across the Plains
states by next week. Nonetheless, overall forcing for ascent, along
with buoyancy, are expected to be weak over the Plains next week,
with severe potential currently appearing low.

..Squitieri.. 09/02/2025

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ACUS48 KWNS 030818
SWOD48
SPC AC 030817

Day 4-8 Convective Outlook
NWS Storm Prediction Center Norman OK
0317 AM CDT Wed Sep 03 2025

Valid 061200Z - 111200Z

...DISCUSSION...
The western North American midlevel ridge of the previous days will
slowly move east into the central continent by the end of the
forecast period and in its place an amplified longwave trough will
take hold across the western US.

... Saturday/Day-4 ...
Before this transition happens, a seasonably strong cold front will
push east into the Atlantic and south into the northern Gulf states
as an expansive surface high will move into the central US on
Saturday/Day-4. Guidance disagrees to the degree instability will
materialize along and ahead of the front from the Mid-Atlantic
region into New England. However, pattern recognition would support
scattered strong thunderstorms along the front across this region.
Midlevel flow will be sufficiently strong to support at least some
damaging wind potential should thunderstorms develop.

... Sunday/Day-5 through Wednesday/Day-8 ...

A seasonably cool, dry continental airmass will be in place across
much of the eastern two-thirds of the contiguous US, resulting in
low potential of organized severe thunderstorms on Sunday/Day-5.
That said, as the western trough takes hold, lee troughing will
develop across the High Plains. This will result in return flow
drawing low-level northward by early next week. Weak shortwave troughs/vorticity maxima embedded in the increasingly southwesterly
flow may yield thunderstorms across the High Plains during the late
afternoon into the overnight hours. Depending on the quality of the
resulting low-level moisture return and the strength of any of these
shortwave troughs, the potential for organized severe thunderstorms
may develop, especially later in the forecast period. However,
predictability of these features at this time scale is too low to
warrant unconditional probabilities at this time.

..Marsh.. 09/03/2025

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ACUS48 KWNS 040848
SWOD48
SPC AC 040846

Day 4-8 Convective Outlook
NWS Storm Prediction Center Norman OK
0346 AM CDT Thu Sep 04 2025

Valid 071200Z - 121200Z

...DISCUSSION...
A seasonally cool and dry continental airmass will be in place
across much of the eastern US at the start of the forecast period,
resulting in low severe potential. By Monday/Day-5, the surface high
pressure responsible for this airmass will have begun to move east
allowing return flow to become established across the Plains. At the
same time, lee troughing in response to a western US longwave trough
will reinforce the return flow regime.

As the moisture is drawn northward into the Plains, steep lapse
rates will advect out into the Plains from the higher elevations to
the west. This combination of moistening low-levels and steep
midlevel lapse rates will support increasing buoyancy profiles
through the week.

Any subtle shortwave trough that ejects out of the western trough
and emerges into the central and northern Plains will have an
opportunity to tap into this moist, buoyant atmosphere. The result
would be at least some potential for thunderstorms, some of which
could be severe. However predictability of these kinds of subtle
features is too poor at these lead times to attempt to highlight
favored days or corridors, thus predictability remains too low for unconditional probabilities.

..Marsh.. 09/04/2025

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ACUS48 KWNS 050855
SWOD48
SPC AC 050854

Day 4-8 Convective Outlook
NWS Storm Prediction Center Norman OK
0354 AM CDT Fri Sep 05 2025

Valid 081200Z - 131200Z

...DISCUSSION...
Upper-level ridging within the West will slowly shift into the
Plains this weekend and into perhaps the middle of next week. Modest
to moderate mid-level flow will generally continue across the Midwest/Northeast. In the West, current guidance shows a trough
slowly making progress east next week. Model guidance has shown a
high degree of variability with regard to how this western trough
will evolve through time. Expansive surface high pressure will be
present in parts of the Plains and points eastward. With time, this
high will move east and promote southerly return flow across the
Plains. This process will accelerate as the western trough
approaches. While some strong to severe storms will be possible as
moisture returns northward, the timing and location of this
potential largely depends on where surface boundaries set up and
where smaller scale perturbations will eject into the Plains. The predictability of these features remains low at this time.

..Wendt.. 09/05/2025

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ACUS48 KWNS 060900
SWOD48
SPC AC 060859

Day 4-8 Convective Outlook
NWS Storm Prediction Center Norman OK
0359 AM CDT Sat Sep 06 2025

Valid 091200Z - 141200Z

...DISCUSSION...
Medium range guidance shows good agreement on the upper-level
pattern from next Tuesday into late next week. A western trough will
remain within the Great Basin and Northwest while a ridge across the
Plains will make very slow eastward progress. The overall pattern
will favor at least a narrow zone of moisture return northward into
parts of the Plains. Where models differ is when stronger mid-level
winds will spread into the Plains. The GFS suggests this could
happen late this coming week while the ECMWF shows the trough
ejecting more towards next weekend. Even with these differences,
some severe risk could develop within the High Plains/Plains near
surface boundaries or where small scale perturbations provide
additional ascent. Give the low predictability of these key
features, severe probabilities will continue to be withheld.

..Wendt.. 09/06/2025

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ACUS48 KWNS 070900
SWOD48
SPC AC 070858

Day 4-8 Convective Outlook
NWS Storm Prediction Center Norman OK
0358 AM CDT Sun Sep 07 2025

Valid 101200Z - 151200Z

...DISCUSSION...
The mid-level flow pattern across the US is forecast to become more
stagnant into the extended-range forecast period as the western US
upper low deepens and shortwave ridging over the Plains moves slowly
eastward. Broad troughing over the East should gradually
consolidate, slowing eastward progress of the upper ridge. As the
western trough slowly approaches the Rockies, a lee trough should
sharpen each afternoon with a narrow zone of moisture return along
and east into parts of the High Plains. Sufficient destabilization
is expected to support isolated thunderstorms, and perhaps some
severe risk, near the lee trough as smaller embedded perturbations
eject eastward periodically. However, with only slow movement of the
upper ridge expected, forcing for ascent should remain modest until
early next weekend. Somewhat greater severe potential may develop
D6/Friday or D7/Saturday as the primary upper trough begins to
emerge over the Plains. However, given the uncertainties associated
with the smaller scale features, and the timing of the main trough,
limited confidence exists regarding severe potential in the extended
forecast.

..Lyons.. 09/07/2025

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ACUS48 KWNS 080902
SWOD48
SPC AC 080900

Day 4-8 Convective Outlook
NWS Storm Prediction Center Norman OK
0400 AM CDT Mon Sep 08 2025

Valid 111200Z - 161200Z

...DISCUSSION...
The primary focus for isolated severe potential for the next several
days will be the upper low over the western US. The upper low is
forecast to slowly deepen late this week as it drifts eastward.
Shortwave ridging over the Plains is also forecast to move eastward,
gradually breaking down into this weekend. Surface high pressure
over the eastern US will allow modest return flow into the western
Plains along a lee trough and weak surface low over the Dakotas.
Sufficient destabilization is expected to support isolated
thunderstorms, and perhaps some severe risk, near the surface trough
as several shortwave perturbations within the southwesterly flow
ahead of the primary upper low move over the Plains. Somewhat
greater severe potential may develop this weekend as the upper low
ejects over the Plains and more robust moisture. However,the upper
trough may begin to weaken with the stronger flow aloft being
displaced north of the best moisture and buoyancy. While isolated
severe potential may exist each afternoon over the central and
northern Plains into early next week, confidence in widespread
severe potential remains too low for probabilities at this time.

..Lyons.. 09/08/2025

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ACUS48 KWNS 090901
SWOD48
SPC AC 090859

Day 4-8 Convective Outlook
NWS Storm Prediction Center Norman OK
0359 AM CDT Tue Sep 09 2025

Valid 121200Z - 171200Z

...DISCUSSION...
As shortwave ridging begins to breakdown into this weekend, the
upper trough and enhanced southwesterly flow over the Rockies will
finally begin to overspread the Plains D4/Friday and D5/Saturday.
Continued east/southeasterly low-level flow is likely over the
northern Plains and Upper Midwest, allowing for the return of richer
surface moisture. A stalled front extending eastward from the lee
low over the Dakotas into the western Great Lakes may serve as a
focus for storm development across the Dakotas and MN. However,
models vary on the degree of moisture and resulting buoyancy near
the low/front, which casts significant uncertainty on severe
potential. Enhanced southwesterly flow aloft could support some
organized severe threat, but confidence in specifics remains too low
for 15% probabilities.

Farther south, sufficient destabilization is expected to support
isolated thunderstorms each afternoon into the central and southern
Plains. While the main upper trough should begin to weaken later
into the weekend, lingering mid-level flow could support some severe
risk within a hot and unstable air mass along a surface trough. By
early next week, mid-level ridging is expected to rebuild over the
central CONUS keeping stronger flow aloft and severe potential
limited for the remainder of the extended forecast period.

..Lyons.. 09/09/2025

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ACUS48 KWNS 100857
SWOD48
SPC AC 100856

Day 4-8 Convective Outlook
NWS Storm Prediction Center Norman OK
0356 AM CDT Wed Sep 10 2025

Valid 131200Z - 181200Z

...DISCUSSION...
Severe potential in the extended forecast period will be tied to a
shortwave trough and stronger southwesterly flow aloft emanating
from the Rockies over the central US. Flow aloft will increase
D4/Saturday as the upper trough begins to overspread the central US.
Ascent from the trough will maintain a weak surface low and
stationary front over the northern Plains and Upper Midwest. At the
same time, a weak cold front will move eastward over the High Plains
serving as a focus for thunderstorm development from the Dakotas and
MN to the southern Plains each afternoon. Some isolated severe
potential is apparent near the surface low/stalled front over the
northern Plains and along the cold front farther south through the
remainder of the weekend. However, model guidance varies widely on
available moisture/buoyancy and the overlap with more robust
vertical shear. This continues to cast significant uncertainty on
severe probabilities through the first half of the extended forecast
period.

By early next week, mid-level ridging is expected to strengthen,
forcing stronger flow aloft northward as the primary western trough
begins to weaken. A second trough will stall over the West as the
ridge continues to build. This should favor drier surface conditions
while also limiting the overlap of buoyancy with stronger flow
aloft. Severe potential appears limited beyond this weekend and into
the first half of next week.

..Lyons.. 09/10/2025

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ACUS48 KWNS 110855
SWOD48
SPC AC 110854

Day 4-8 Convective Outlook
NWS Storm Prediction Center Norman OK
0354 AM CDT Thu Sep 11 2025

Valid 141200Z - 191200Z

...DISCUSSION...
Model guidance is in fairly good agreement that the upper trough
over the central US will continue to lift northeastward into the
northern Plains and Upper Midwest through early next week. This will
drag a surface low and cold front slowly eastward with seasonably
high moisture in place. The low will begin to fill as it also lifts
into southern Canada. Scattered to numerous thunderstorms appear
likely over the Northern Plains and Upper Midwest, and along the
trailing front over the southern/central Plains each afternoon, as
increasingly meridional flow will parallel the slow moving cold
front. This will favor continued storm development/training along
the boundary with limited air mass destabilization/recovery.
Mid-level lapse rates should also weaken as the upper trough begins
to fill. While some marginal severe risk is evident over the
northern Plains near the low and front, mainly D4/Sunday,
significant uncertainty exists regarding boundary-layer
destabilization and its impacts on severe potential through
D5/Monday.

By D6/Tuesday, mid-level ridging behind the trough is forecast to
temporarily strengthen, weakening upper-level flow across the CONUS.
A second upper trough over the northern Rockies will begin to
approach behind the central US ridge, while a cutoff low develops
over the Southeast. This should limit broader overlap of instability
and stronger mid-level flow across much of the CONUS. Widespread
severe weather appears unlikely through next week.

..Lyons.. 09/11/2025

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ACUS48 KWNS 120759
SWOD48
SPC AC 120758

Day 4-8 Convective Outlook
NWS Storm Prediction Center Norman OK
0258 AM CDT Fri Sep 12 2025

Valid 151200Z - 201200Z

...DISCUSSION...
On Monday, a shortwave trough in the northern Plains will continue
to pivot northeast. The timing of this feature remains uncertain.
The ECMWF is the lone model that has a solution slow enough to have
some destabilization occur ahead of the trough. It is not clear how
much, if any, severe threat will exist in parts of central/northern
Minnesota.

On Tuesday, models indicate shortwave ridging will develop behind
the departing trough in the Upper Midwest. A secondary, broader
trough will be situated in the northern Rockies. Mid-level flow will
not be particularly strong, but embedded perturbations may provide
some enhancement. Depending on the quality of remaining moisture in
the Plains, some severe risk could develop along the surface trough
in the central High Plains. Uncertainty is high, however.

Through the remainder of the week, the upper-level pattern becomes
much more disorganized. Stronger flow may not return until the
weekend with a trough approaches the Northwest. Organized severe
potential appears to be low during this period.

..Wendt.. 09/12/2025

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ACUS48 KWNS 130756
SWOD48
SPC AC 130754

Day 4-8 Convective Outlook
NWS Storm Prediction Center Norman OK
0254 AM CDT Sat Sep 13 2025

Valid 161200Z - 211200Z

...DISCUSSION...
Weak mid/upper-level troughing should continue to move slowly
eastward from the northern Rockies/High Plains into the central
Plains and Upper Midwest from Day 4/Tuesday into Day 5/Wednesday.
Thunderstorms should develop across these regions both days as a
surface cold front likewise develops east-southeastward. While
moderate to locally strong instability may develop across the warm
sector each afternoon, mid-level flow and related deep-layer shear
are expected to remain rather modest. This should tend to limit
updraft organization and intensity to some extent, although
isolated/marginal severe potential may necessitate low severe
probabilities in later outlooks.

By late next week into the following weekend (Day 6/Thursday to Day 8/Saturday), medium-range guidance begins to diverge in its
depiction of the evolution of upper troughing across the Midwest/OH
Valley into the eastern CONUS. This lowers confidence in the
predictability of organized severe thunderstorms, but some potential
for strong thunderstorms may exist across portions of these regions
along/ahead of an advancing cold front.

..Gleason.. 09/13/2025

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