Severe Storm Outlook Narrative (AC)
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ACUS01 KWNS 220106
SWODY1
SPC AC 220105

Day 1 Convective Outlook
NWS Storm Prediction Center Norman OK
0805 PM CDT Thu Sep 21 2017

Valid 220100Z - 221200Z

...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS FROM PORTIONS OF
SOUTHEAST ND/NORTHEAST SD EASTWARD INTO THE WESTERN UPPER GREAT
LAKES AREA...

...SUMMARY...
A marginal risk for a few large hail events exists over a part of
the Upper Midwest tonight into Friday morning.

...MN/northern WI/western Upper MI and vicinity...
A weak short-wave trough moving northeast across the central U.S.
this evening will combine with the beginnings of an observed
increase in the southerly low-level jet to yield some enhancement of
quasi-geostropic ascent across north-central portions of the country
tonight.  This increase in ascent -- given favorable elevated
instability indicated by evening RAOBs -- may prove sufficient for
development of isolated/elevated storms.  Certainty regarding degree
of convective coverage remains elusive, as sampling of a large
number of CAM runs reveals solutions ranging from very little if any
convection to scattered coverage of intense updrafts.

With cloud-layer shear sufficient for updraft organization and CAPE
favorable for intense cells, will maintain 5% risk for hail across
this region, but conditionality of the risk precludes SLGT risk
upgrade.

..Goss.. 09/22/2017

$$



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