Day 3 Convective Outlook  
NWS Storm Prediction Center Norman OK
0216 AM CDT Mon Aug 31 2026

Valid 021200Z - 031200Z

...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS FOR PORTIONS OF
THE EASTERN GREAT LAKES TO THE MID-ATLANTIC COASTLINE...

...SUMMARY...
Severe storms are expected across portions of the eastern Great
Lakes to the Mid-Atlantic on Wednesday. Severe wind and hail are the
main threats, though a tornado or two may also occur.

...Synopsis...
Upper ridging will persist across the central and eastern CONUS as
an upper trough progresses across the Intermountain West on
Wednesday. A pronounced mid-level impulse will traverse the Great
Lakes and overspread the northern Mid-Atlantic by Wednesday
afternoon. Seasonably cold temperatures aloft and strong
northwesterly flow will accompany this impulse while it passes over
a moist and unstable boundary layer, promoting the potential for
severe storms. 

...Northwest PA to the Mid-Atlantic Coastline...
Scattered thunderstorms (perhaps strong) will be ongoing across PA
and points southeast at the start of the period (12Z Wednesday).
Through the early afternoon hours, showers and thunderstorms will
give way to at least modest insolation, resulting in boundary layer
destabilization. Surface heating of a moist boundary layer (e.g. low
70s F surface dewpoints) will result in 2000-3000 J/kg MLCAPE given
mid-level lapse rates approaching 7 C/km. The aforementioned
mid-level impulse overspreading eastern Lower Michigan to the
Delmarva will result in strong northwesterly flow aloft and 35-45
kts of effective bulk shear. Furthermore, forecast soundings also
depict appreciably large and curved hodographs, with over 200 m2/s2
0-3 km SRH. Supercells and bowing segments will be the most likely
storm mode, with severe wind and hail the main threats, though a
couple of tornadoes are also possible.

...Portions of the eastern Great Lakes...
A secondary mid-level impulse will traverse the eastern Great Lakes
by Wednesday afternoon, which may support an additional round of
storms. These storms will be preceded by 7.5-8 C/km mid-level lapse
rates, which will overspread 70 F surface dewpoints and yield 2000+
J/kg MLCAPE amid 35+ kts of effective bulk shear. Multicells and
supercells may occur, accompanied by a severe wind/hail threat.

..Squitieri.. 08/31/2026

Day 4-8 Convective Outlook  
NWS Storm Prediction Center Norman OK
0346 AM CDT Mon Aug 31 2026

Valid 031200Z - 081200Z

...DISCUSSION...
An upper ridge will persist across the TN Valley this week before
retrograding to the Plains states and further amplifying into early
next week. As this occurs, upper troughing will also amplify along
the East Coast and Interior West. The best chances for severe storms
will be closer to the East Coast Days 4-5 (Thursday-Friday) as a
series of mid-level impulses will crest the Ridge and traverse the
Mid Atlantic, where instability will be present.

...Days 4-6 (Thursday-Saturday) - Mid-Atlantic Region...
The amplification of the broader upper trough along the East Coast
will result in a farther southward shift of accompanying mid-level
impulses, which will promote deep-layer ascent over the Mid-Atlantic
region. The severe threat may also be modulated farther south given
established baroclinic zones from prior rounds of storms. On
Thursday, storms should develop along a differential heating zone
somewhere around Delmarva or points immediately west. Surface
dewpoints in the upper 60s to near 70 F beneath seasonably cool
temperatures aloft will yield 1500-3000 J/kg MLCAPE. Given over 30
kts of effective bulk shear expected, multicells, supercells, and
short bowing segments will likely develop, accompanied by a severe
wind/hail threat.

For Day 5 (Friday), the upper trough will amplify further, allowing
for a surface differential heating zone to become established across
the southern Mid-Atlantic, where adequate moisture and instability
will likely coincide with modest vertical wind shear, supporting
another day of severe potential. Damaging gusts will likely be the
main threat.

Some lingering severe potential may exist across the Carolinas on
Day 6/Saturday before the upper trough departs the region, as
indicated by some ML/AI guidance. However, predictability on the
timing of details (i.e. baroclinic boundaries and overlapping
corridors of vertical wind shear) is too low for the introduction of
probabilities this outlook.

...Day 4 (Thursday) - Upper Midwest...
Some guidance depicts the potential for severe thunderstorms along
an effective warm front across portions of the Upper Midwest, where
rich low-level moisture will reside ahead of a surface trough. Given
stronger mid-level flow and cooler temperatures overspreading the
warm front, enough shear and instability may manifest to support a
severe threat. While calibrated guidance has been ramping up severe
probabilities over this area, synoptic features (such as a
pronounced mid-level impulse) do not appear strongly evident in
deterministic guidance, precluding the addition of severe
probabilities to this outlook.