164
ACUS48 KWNS 120837
SWOD48
SPC AC 120835

Day 4-8 Convective Outlook
NWS Storm Prediction Center Norman OK
0335 AM CDT Wed Aug 12 2026

Valid 151200Z - 201200Z

...DISCUSSION...
...D4/Saturday...
Most guidance depicts one or more midlevel vorticity maxima cresting
the upper ridge and moving across the Upper Midwest/Great Lakes
region on Saturday. However, there is considerable spread regarding
the timing of these features and the northward extent of substantial
destabilization. The general pattern suggests some potential for MCS
development across parts of the Midwest/Great Lakes region, but
uncertainty regarding the favored corridor precludes addition of 15%
probabilities at this time.

...D5/Sunday...
Extended-range guidance is in general agreement depicting a cold
front that will move across parts of the Midwest, Great Lakes, Ohio
Valley, and Northeast on Sunday. This front will impinge upon a
reservoir of rich moisture and moderate to locally strong buoyancy,
which could result in a severe-thunderstorm threat along/ahead of
the front. Substantial timing differences remain regarding the
front, but severe probabilities may eventually be needed for this
scenario.

...D6/Monday - D7/Tuesday...
A similar upper-level pattern is expected to persist into early next
week, with west-northwesterly midlevel flow extending from the
northern Plains into the Midwest/Great Lakes and
Northeast/Mid-Atlantic. This pattern will continue to favor at least
an isolated severe threat, with low-predictability MCS potential.

..Dean.. 08/12/2026