698
ACUS48 KWNS 040750
SWOD48
SPC AC 040747

Day 4-8 Convective Outlook
NWS Storm Prediction Center Norman OK
0247 AM CDT Fri Sep 04 2026

Valid 071200Z - 121200Z

...DISCUSSION...
...Days 4-6/Mon-Wed -- Northern Plains to Great Lakes...

An upper shortwave trough is forecast to move across the Canadian
Prairies and Upper Midwest through Tuesday, before continuing east
toward the Lower Great Lakes on Wednesday. This will shift the
amplified upper ridge over the Plains at the beginning of the period
eastward over the Midwest, before flattening the ridge over the
Great Lakes through mid-week. As this occurs, enhanced
west/southwesterly flow will overspread portions of the northern
Plains/Upper Midwest and eventually the Great Lakes. A surface low
will track east/northeast across central Canada, and a trailing cold
front will move across the region on Tuesday/Wednesday. Some severe
potential could develop across the Dakotas into the Upper Midwest
Monday and Tuesday given enhance southwesterly flow aloft and
sufficient moisture ahead of the surface boundary. However, warm
midlevels may result in capping while large-scale ascent will be
focused mostly north of the international border. As a result,
severe potential and storm coverage are uncertain, precluding 15
percent probabilities at this time.

The cold front will weaken on Wednesday as the upper low lifts into
northern Ontario, and deep-layer flow will veer, becoming mostly
westerly. While some severe potential could develop into parts of
the Midwest and eastern Great Lakes vicinity, confidence is low
regarding where the greatest risk could emerge.

...Days 7-8/Thu-Fri...

The upper ridge is forecast to once again amplify over the Rockies
and into the Plains late in the week and severe potential appears
limited.

..Leitman.. 09/04/2026