SPC AC 232000

   Day 1 Convective Outlook  
   NWS Storm Prediction Center Norman OK
   0300 PM CDT Wed Jun 23 2021

   Valid 232000Z - 241200Z

   ...THERE IS AN ENHANCED RISK OF SEVERE THUNDERSTORMS THIS EVENING
   ACROSS CENTRAL NEBRASKA...

   ...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS FROM NORTHERN
   MN/WI INTO THE WESTERN U.P. OF MI...

   ...SUMMARY...
   Strong to severe storms are expected late this afternoon into
   tonight across parts of the central Plains and Upper Midwest.
   Damaging winds and large hail should be the main threats, with the
   greatest damaging wind threat expected across central Nebraska
   tonight.

   ...Nebraska and vicinity...
   The primary change for the 20Z outlook is to add a 10% significant
   wind area across portions of central NE. Development of a bowing
   complex still looks possible this evening, which would pose a threat
   of at least isolated significant (greater than 65 kt) wind gusts
   within a corridor of potentially damaging wind. The Marginal Risk
   has also been expanded somewhat to the north and east across
   southeast SD and western IA, in deference to some CAM guidance which
   suggests vigorous development is possible later tonight in these
   areas. 

   ..Northern MN/WI...
   No changes have been made to this area. Widely scattered strong
   thunderstorms still appear possible by late afternoon along a cold
   front, and later tonight within a warm advection regime, posing a
   threat of large hail and damaging wind as convection spreads
   southeastward.

   ..Dean.. 06/23/2021

   .PREV DISCUSSION... /ISSUED 1256 PM CDT Wed Jun 23 2021/

   ...NE and vicinity...
   Morning water vapor loop shows an upper ridge over the central High
   Plains region.  Model guidance indicates that midlevel heights will
   continue to rise across this area through mid-afternoon, until a
   weak shortwave trough over WY/CO tops the ridge and begins to move
   into western NE.  This will be coincident with peak heating and
   scattered thunderstorm development.  These storms will likely become
   severe by early evening and track across much of NE through the
   night.  Convection is expected to grow upscale during this period,
   with a fast-moving bowing complex capable of damaging winds. 
   Therefore, have added a small ENH for this threat.

   ...Northern MN/WI...
   A strong shortwave trough is digging southeastward across
   Saskatchewan toward the northern Plains.  The associated surface
   cold front will sweep into ND/MN this evening, where scattered
   thunderstorm development is expected.  These storms will track
   southeastward across northern MN through the evening, and into
   northern WI overnight.  Low-level moisture will be slowly recovering
   in this region, with the greatest moisture/CAPE values remaining
   south of the SLGT risk area.  Nevertheless, a few intense cells will
   be possible, capable of large hail and damaging winds.

   ...Southern MT into northeast WY...
   Strong heating is occurring today across southern MT into northeast
   WY, where dewpoints are in the 40s and afternoon MLCAPE values are
   forecast to approach 1000 J/kg.  Forecast soundings indicate a
   deeply mixed boundary layer, along with relatively strong westerly
   flow aloft.  This may result in a few thunderstorms capable of
   gusty/damaging winds this afternoon and early evening across the
   region.

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