Severe Storm Outlook Narrative (AC)
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ACUS48 KWNS 120849
SWOD48
SPC AC 120848

Day 4-8 Convective Outlook
NWS Storm Prediction Center Norman OK
0348 AM CDT Wed Aug 12 2020

Valid 151200Z - 201200Z

...DISCUSSION...
...Saturday/Day 4 and Sunday/Day 5...
The medium range models move an upper-level trough and an associated
cold front into the western Great Lakes on Saturday and into the
lower Great Lakes on Sunday. Thunderstorms will be possible along
and ahead of the front on both days from the Great Lakes into the
mid Mississippi Valley. Model forecasts also show moderate
deep-layer shear along much of the front each day suggesting a
severe threat could develop. Model consensus places a severe threat
across parts of Wisconsin and Illinois on Saturday, and from Ohio to
Kentucky on Sunday. But the extent of a severe threat will depend
upon the magnitude of instability which is uncertain at this time.

...Monday/Day 6 to Wednesday/Day 8...
On Monday, an upper-level trough is forecast to move across the
lower Great Lakes region and Ohio to Tennessee Valleys. At the
surface, a cold front is forecast to move into the Southeast.
Thunderstorms associated with an isolated severe threat will be
possible along parts of the front Monday afternoon.

From Tuesday into Wednesday, the models show moisture advection
across the Great Plains and maintain northwest mid-level flow across
much of north-central states. Although model solutions vary
considerably, some solutions develop a pocket of moderate
instability in the central and northern Plains on Tuesday and
Wednesday. If this scenario pans out, then thunderstorms that
develop in proximity to this pocket of instability, may have a
potential to become severe. But model spread and the resultant
uncertainty is considerable at this range.

..Broyles.. 08/12/2020


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