SPC AC 030724

   Day 3 Convective Outlook  
   NWS Storm Prediction Center Norman OK
   0224 AM CDT Thu Sep 03 2020

   Valid 051200Z - 061200Z

   ...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS FROM EASTERN
   SOUTH DAKOTA AND SOUTHERN MINNESOTA INTO IOWA AND NORTHWEST
   ILLINOIS...

   ...SUMMARY...
   Isolated severe thunderstorms are possible over parts of the Corn
   Belt Saturday night.

   ...Synopsis...
   A pronounced mid-level anticyclone will remain centered over UT/AZ
   while a belt of strong northwesterly mid-level flow is maintained
   across the Upper Midwest into the Great Lakes as a large-scale
   trough resides over eastern Canada and the Northeast.  A mid-level
   disturbance is forecast to rapidly move from MT east-southeastward
   into the mid MS Valley during the period.  As this occurs, a surface
   low will develop over the Dakotas and a warm front over the central
   Great Plains will advance north/northeast.  Southerly low-level flow
   will advect mid 60s to lower 70s F dewpoints north into parts of the
   lower MO Valley by early evening.  Strengthening warm air advection
   aided by a developing southwesterly LLJ after dark will likely lead
   to scattered elevated thunderstorms developing during the late
   evening perhaps as far west as southeast SD and increasing in
   coverage during the overnight as this activity spreads
   east/southeast.  The eastern periphery of a plume of steep 700-500
   mb lapse rates (8-9 deg C/km) and strong effective shear may favor
   large hail with the stronger elevated cores.  An isolated damaging
   gust may also occur given the presence of steep lapse rates and the
   possibility for an organized thunderstorm cluster to develop. 
   Uncertainty primarily related to convective evolution precludes
   higher severe probabilities this outlook update.

   ..Smith.. 09/03/2020

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   NOTE: THE NEXT DAY 3 OUTLOOK IS SCHEDULED BY 0730Z