ACUS48 KWNS 140746
SWOD48
SPC AC 140744
Day 4-8 Convective Outlook
NWS Storm Prediction Center Norman OK
0244 AM CDT Sun Jun 14 2026
Valid 171200Z - 221200Z
...DISCUSSION...
...Day 4/Wednesday -- Mid-MS and Ohio Valley vicinity...
An upper shortwave trough is forecast to deepen as it moves across
the Upper Midwest and Great Lakes on Wednesday. As this occurs, an
intense jet streak (especially by June standards) is forecast to
overspread portions of the Midwest. The ECMWF and GFS suite of
forecast guidance still is indicating a 500 mb jet streak greater
than 80 kt overspreading the region by evening. Furthermore, low and
midlevel flow will also be quite strong, with a daytime 850 mb
low-level jet around 40-50 kt by mid/late afternoon.
At the surface, low pressure will deepen and move across the Upper
MS Valley and Lower MI through the period. A warm front is forecast
to move rapidly northward across IL and portions of the OH Valley
through 00z. Meanwhile, a trailing cold front will develop eastward
across the region through the period. The warm sector will be
characterized by dewpoints in the mid 60s to low 70s, and areas of
strong destabilization are expected. While details concerning
convective evolution remain uncertain, the overall environment will
support supercells with upscale development into a bowing MCS
possible by evening as the low-level jet continues to increase and
spread east/northeast across the region. All severe hazards appear
likely, with the greatest risk likely emerging across portions of
the Lower MO/Mid-MS Valley where significant severe storms are
expected. Some severe risk will likely persist into the nighttime
hours across parts of the Ohio Valley given intense deep-layer flow
and sufficient instability.
Some details will likely change in subsequent outlooks as the track
of the surface low and orientation of the mid/upper level jet streak
atop the develop surface warm sector become better resolved closer
to the event. The risk areas may shift some as these details become
clearer.
...Day 5/Thursday -- Ohio Valley to Mid-Atlantic...
An upper shortwave trough will pivot across the Lower Great
Lakes/Northeast on Thursday, with a strong southwesterly jet streak
forecast to overspread parts of the Ohio Valley into New England.
The jet streak may tend to become increasing displaced from better
low-level moisture/thermodynamic with time and eastward extent
through the period. Nevertheless, a moist and unstable airmass is
expected ahead of an eastward-advancing cold front and a severe risk
should unfold across parts of the Ohio Valley to the Mid-Atlantic.
Northward extent of the severe risk is uncertain as early period
convection and widespread rainfall may hinder destabilization. The
best overlap of favorable vertical shear and instability is
delineated by the 15 percent probabilities from OH/KY into the
Mid-Atlantic, where damaging wind potential is likely to be the main
concern.
...Days 6-8/Friday-Sunday...
Large spread among medium range guidance during the end of the
forecast period leads to low predictability. The surface front from
Day 4/5 will likely stall across the southern U.S. and periods of
heavy rain will be possible across the Southeast. Late in the
period, some signal for moisture return and a deepening lee low over
the Plains could bring some increasing severe risk, but details
remain uncertain.
..Leitman.. 06/14/2026
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