Severe Storm Outlook Narrative (AC)
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000
ACUS48 KWNS 220801
SWOD48
SPC AC 220759

Day 4-8 Convective Outlook
NWS Storm Prediction Center Norman OK
0259 AM CDT Fri Sep 22 2017

Valid 251200Z - 301200Z

...DISCUSSION...
The slow-moving longwave trough over the West will finally begin to
weaken and eject northeastward toward the western Great Lakes region
around D5/Tuesday.  Ahead of this trough, surface cyclogenesis
should occur in Wisconsin that, when combined with weak
surface-based destabilization, may result in a risk for isolated
severe storms during the afternoon and evening.

Beyond this period, models diverge substantially with regard to a
remnant cut-off low over the Southwest and a downstream trough near
the Great Lakes.  Despite differences in the mid/upper synoptic
pattern, models generally suggest varying degrees of surface ridging
across the northern Rockies and central Plains that should result in
a cooler, drier airmass spreading into these areas.  With modified
maritime air shunted south of more active westerlies (nearer the
Great Lakes and vicinity), it appears that any organized severe risk
should be on the decrease.

..Cook.. 09/22/2017


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