Severe Storm Outlook Narrative (AC)
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000
ACUS03 KWNS 190718
SWODY3
SPC AC 190717

Day 3 Convective Outlook
NWS Storm Prediction Center Norman OK
0217 AM CDT Tue Sep 19 2017

Valid 211200Z - 221200Z

...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS ACROSS EASTERN
NORTH DAKOTA AND NORTHERN/CENTRAL PORTIONS OF MINNESOTA...

...SUMMARY...
A few hail-producing storms are possible in portions of Minnesota
and eastern North Dakota Thursday night.

...Synopsis...
An amplifying longwave trough across the West will become nearly
stationary with time, while a mid/upper ridge becomes established
across the Great Lakes and Ohio Valley.  At the surface,
cyclogenesis will begin in earnest across the northern Plains as a
ridge becomes dominant across the Northeast and Appalachians.
Southerly low-level flow across much of the center of the country
will result in a moist low-level airmass retreating northward, with
60s F dewpoints reaching the Minnesota/Ontario border overnight.

...Eastern North Dakota and northern/central Minnesota...
The amplification of the long-wave trough in the West will result in
backing mid/upper flow and subtle height rises during the day, which
should keep daytime convective potential at a minimum.  In the
evening, however, strengthening low-level flow will occur in
conjunction with a 50-55kt 850mb jet across the central Plains, and
convergence on the nose of this synoptic-scale feature will foster
scattered thunderstorm development primarily after 00Z.  Steep
mid-level lapse rates and kinematic profiles will result in
primarily a hail threat with elevated convection occurring across
the region.  Marginal (5%) severe probabilities have been added to
address this threat, and later outlooks may needed higher
probabilities if more focused corridors of hail potential become
apparent.

..Cook.. 09/19/2017

$$



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