Day 4-8 Outlook
Day 4-8 Convective Outlook
NWS Storm Prediction Center Norman OK
0354 AM CDT Wed Jul 20 2022
Valid 231200Z - 281200Z
...DISCUSSION...
Medium-range guidance is in good agreement that an upper low will
persist over eastern Canada this upcoming weekend. Upper ridging
should also remain centered over the southern CONUS in this time
frame. In between these two features, a low-amplitude shortwave
trough is forecast to move eastward from the northern Plains into
the Upper Midwest and Great Lakes on Day 4/Saturday. Rich low-level
moisture should be in place ahead of a front across parts of the
Upper Midwest, with moderate to locally strong instability forecast.
Enhanced mid-level flow attendant to the shortwave trough should act
to organize any thunderstorms that can develop along/ahead of the
front Saturday afternoon and evening. At this point, there is enough
confidence in robust thunderstorms developing to introduce a 15%
severe area for parts of the Upper Midwest on Saturday. Deep-layer
shear appears strong enough for a mix of multicells and supercells,
with some potential for an MCS and greater threat for severe winds
to develop as convection possibly grows upscale along the front.
Some severe threat may exist on Day 5/Sunday across parts of the
Northeast into the OH Valley ahead of a front as an upper trough
continues eastward. But, there is currently too much uncertainty
regarding forecast instability to include a 15% severe delineation.
The predictability of organized severe thunderstorms quickly
decreases from Day 6/Monday onward, as generally low-amplitude
perturbations move across the northern tier of the CONUS on the
northern periphery of a persistent upper ridge.
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