SPC AC 251730

   Day 2 Convective Outlook  
   NWS Storm Prediction Center Norman OK
   1230 PM CDT Sat Aug 25 2018

   Valid 261200Z - 271200Z

   ...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS FROM THE NORTHERN
   PLAINS INTO THE UPPER MISSISSIPPI VALLEY/UPPER MIDWEST/WESTERN UPPER
   GREAT LAKES REGION...

   ...SUMMARY...
   Severe thunderstorms are possible Sunday through Sunday night across
   parts of the northern Plains and into the Upper Mississippi
   Valley/Upper Midwest/western Upper Great Lakes region.

   ...Synopsis...
   Weak ridging aloft is progged to persist across roughly the southern
   half of the U.S. Sunday, with faster/more amplified flow farther
   north.  Within this faster flow, a trough is forecast to move slowly
   east across the Intermountain region with time, while a couple of
   smaller-scale lead features cross the central and northern Plains
   during the period.

   At the surface, the main feature is expected to be a low and
   associated cool front which should move east-northeast across the
   northern Plains, with a front extending southwestward across the
   northern and central Plains by the end of the period.

   ...Northern Plains across the Upper Mississippi Valley/western Upper
   Great Lakes...
   Thunderstorms are forecast to be ongoing across portions of the
   central Plains/mid Missouri Valley area, and possibly into the upper
   Mississippi Valley region early in the period.  Storms may
   linger/spread east-northeast through the day, and should locally
   strengthen during the afternoon across the upper Mississippi
   Valley/upper Midwest region as the boundary layer destabilizes. 
   With moderate southwesterly flow aloft, potential for hail and/or
   locally damaging winds may evolve with stronger storms.  Some hints
   exist that storms may grow upscale into a band/line during the
   evening across Wisconsin and possibly northern Illinois, which could
   allow wind risk to extend well into the evening.

   Meanwhile farther to the northwest, destabilization is forecast
   through the day across the northern Plains area, ahead of the
   short-wave trough crossing the northern Intermountain Region. 
   Eventually, storm development is expected near/north of a
   weak/developing northern Plains surface low, and an inverted trough
   extending north into the Canadian Prairie.  With low-level
   southerly/southeasterly flow beneath seasonably strong mid-level
   southwesterlies, shear supportive of organized/rotating storms
   suggests potential for large hail and damaging winds with stronger
   storms -- and perhaps even a tornado or two near/north of the
   surface low where backed low-level southeasterlies should exist.  

   With time, there are hints that upscale/linear growth may occur as
   storms spread across North Dakota and possibly/eventually into
   northern Minnesota.  This would permit severe risk to persist
   through the evening and into the overnight hours.

   ...MAXIMUM RISK BY HAZARD...
   Tornado:   5%     - Slight
   Wind:     15%     - Slight
   Hail:     15%     - Slight

   ..Goss.. 08/25/2018

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