Day 1 Convective Outlook
NWS Storm Prediction Center Norman OK
1253 AM CDT Thu Sep 03 2026
Valid 031200Z - 041200Z
...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS TODAY THROUGH
TONIGHT ACROSS PARTS OF THE SOUTHERN GREAT LAKES INTO MID ATLANTIC
AND PARTS OF THE NORTHERN GREAT PLAINS...
...SUMMARY...
Scattered strong thunderstorm development is likely today through
tonight, perhaps including a few organizing clusters, posing a risk
for severe wind and hail across parts of the southern Great Lakes
into Mid Atlantic and portions of the northern Great Plains into
Upper Midwest.
...Discussion...
Large-scale mid-level troughing has overspread much of the Pacific
coast through the Rockies. However, models indicate that further
eastward progress will slow, as at least one significant embedded
short wave trough digs offshore and contributes to amplification of
the larger-scale trough near and offshore of the Pacific coast. As
this occurs, downstream ridging is forecast to build across the
northern Great Plains/middle Missouri Valley vicinity by late
tonight, in the wake of a short wave trough now emerging from the
Great Basin and forecast to progress north-northeast of the northern
Rockies through the eastern Canadian Prairies and northwestern
Ontario. Farther east, it appears that mid-level troughing and an
embedded remnant low will slowly dig southeast of western
Quebec/southern Ontario through the northern Atlantic Seaboard.
A surface cold front accompanying the eastern Canadian perturbation
is preceded by considerable ongoing thunderstorm activity
overspreading the northern Mid Atlantic through Lake Erie vicinity.
It appears that an outflow boundary associated with this convection
may become quasi-stationary across parts of southeastern
Pennsylvania/New Jersey, before the initially stalled upstream
front, across southern portions of the Great Lakes vicinity into
Upper Midwest, advances southeast of the lower Great Lakes through
much of the northern Mid Atlantic and upper Ohio Valley by late
tonight.
...Southern Great Lakes into northern Mid Atlantic...
The initially stalled composite outflow boundary and surface front
appear likely to provide the focus for renewed thunderstorm
development later today through tonight. Across the southeastern
Wisconsin through southern Lower Michigan/northern Indiana and Ohio
vicinity, it appears that the corridor of stronger destabilization
along this boundary will remain in relatively close proximity to the
southern fringe of the westerlies. East-southeastward into the
northern Mid Atlantic this remains more unclear.
Regardless, where the seasonably moist boundary layer becomes
strongly heated, thermodynamic profiles a bit further aloft into
mid-levels, aided by elevated mixed-layer air, will remain
characterized by steep lapse rates of temperature and potential
wet-bulb temperature. This will promote the risk for strong
downbursts and evolving cold pools capable of producing strong to
severe wind gusts in developing thunderstorm activity.
There appears potential for one or two organizing clusters across
and east-southeast of the southern Great Lakes region this afternoon
into tonight. It is possible that severe wind probabilities could
still be increased further, once forcing for convection and the
potential negative impacts of early day convection become clearer.
...Northern Great Plains into Upper Midwest...
Forcing for ascent, near and downstream of the short wave emerging
from the Great Basin, appears likely to overspread northern/eastern
North Dakota into northwestern Minnesota during peak boundary-layer
instability this afternoon and evening. Latest convection-allowing
guidance suggests that this will provide support for intensifying
thunderstorm development, which may include a few supercells in the
leading warm advection regime, ahead of a possible upscale growing
cluster near the crest of the building larger-scale mid-level
ridging. Aided by pronounced veering of lower through mid-level
wind fields, deep-layer shear appears conducive to the risk for
large hail, in the presence of thermodynamic profiles with steep
mid-level lapse rates and large CAPE in mid/upper levels. A few
strong downbursts also appear possible.
..Kerr/Wendt.. 09/03/2026
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