ACUS02 KWNS 020554
SWODY2
SPC AC 020552

Day 2 Convective Outlook  
NWS Storm Prediction Center Norman OK
1252 AM CDT Wed Sep 02 2026

Valid 031200Z - 041200Z

...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS FOR PORTIONS OF
THE UPPER MIDWEST AND PARTS OF THE EASTERN OHIO VALLEY TO THE
MID-ATLANTIC...

...SUMMARY...
Severe storms, accompanied by severe wind and hail (including a
couple 2 inch diameter stones and 75+ mph gusts), are possible
across portions of the Upper Midwest. At least scattered
severe-wind-producing storms are also possible from the eastern Ohio
Valley to the Mid-Atlantic coastline.

...Synopsis...
An upper ridge will remain centered over the MS Valley as upper
troughs persist across the Northeast and Interior West tomorrow
(Thursday). Multiple impulses, accompanied by cooler temperatures
and stronger flow aloft, will pivot around the eastern periphery of
the upper ridge and overspread a moist boundary layer over the Upper
Midwest and OH Valley/Mid-Atlantic regions. Ample buoyancy and
vertical wind shear over both areas will support at least scattered
thunderstorms, several of which may be severe.

...Portions of the Upper MS Valley...
Guidance consensus depicts a subtle impulse cresting the upper ridge
over the northern Plains and impinging on the Upper MS Valley by
afternoon peak heating, serving as the most likely impetus for
convective initiation. Storms will most likely develop somewhere
along the SD/MN border to central MN, preceded by a surface warm
front draped from southern MN, to southern WI and eastern IA.
Surface dewpoints will exceed 70 F along this front, with 8+ C/km
mid-level lapse rates overspreading this moisture, yielding
3000-4000 J/kg MLCAPE. Coincident with this strong buoyancy will be
50 kts of effective bulk shear, with forecast soundings showing
elongated hodographs. 

The current thinking is that initial storms will be supercellular,
accompanied by mainly a severe wind and hail threat (a few stones of
which may exceed 2 inches in diameter). However, if storms merge, a
cold-pool-driven MCS may develop, perhaps even taking on bowing
tendencies should it traverse the surface boundary. In this
scenario, a focused severe wind swath could occur, and a couple of
gusts may exceed 75 mph. Given such subtle forcing for ascent
expected, and the dependency on finer mesoscale details for a
higher-end severe threat, only Category 2/Slight Risk probabilities
were introduced for now. If consistency in guidance consensus
continues to show bow echo evolution, higher severe probabilities
may be needed in future outlooks.  

...Parts of the OH Valley to the Mid-Atlantic Coastline...
Another in a series of mid-level impulses will traverse the
Mid-Atlantic region during the day. A diffuse differential heating
zone should be in place somewhere near the PA/MD border, which will
likely be the location of convective initiation by late morning or
early afternoon. There is also the possibility that upstream
convective complexes, remnant from Day 1 storms along the
larger-scale warm front, may approach from the OH Valley and track
toward the Eastern Seaboard though the day. Regardless of the
convective scenario, storms should overspread 70+ F surface
dewpoints (which will support over 2000 J/kg MLCAPE). Given modest
northwesterly flow aloft, any storms that become sustained will be
accompanied by a severe gust threat, though an instance of hail
cannot be ruled out. Higher severe probabilities are not entirely
out of the question once mesoscale details on convective placement,
timing, and evolution become clearer.

..Squitieri.. 09/02/2026

$$
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