SPC AC 201626

   Day 1 Convective Outlook  
   NWS Storm Prediction Center Norman OK
   1126 AM CDT Wed Oct 20 2021

   Valid 201630Z - 211200Z

   ...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS OVER PORTIONS OF
   THE UPPER MIDWEST...

   ...SUMMARY...
   Thunderstorms with isolated severe hail are possible today across
   northern Iowa and southern Minnesota, primarily through
   mid-afternoon.

   ...Midwest including northern Iowa/southern Minnesota...
   Upper-level low near the NE/SD border will lift east/northeast
   towards the Great Lakes region through tonight. An associated
   surface low and cold front will move east towards lower MI/OH Valley
   as a warm front extends from southern MN/central WI/northern lower
   MI. In advance of the cold front, lower-mid 50s dew points remain
   prevalent and will contribute to modest buoyancy in the presence of
   35-45 kts effective shear. A stronger storm or two within the
   Marginal Risk area will have some potential for hail that could
   approach severe thresholds through early/mid afternoon.

   ...Lower Michigan and far northern Indiana/northwest Ohio...
   Thunderstorms are expected to develop this evening into the
   overnight, primarily across Lower Michigan, aided by ascent within
   the left exit region of an approaching 250-mb jet maximum. This
   convection will be rooted atop a stable boundary layer, with modest
   elevated instability (MUCAPE generally 500-750 J/kg) supportive of
   thunderstorms. This may include some potential for hail, but current
   thinking remains that the risk for severe-caliber hailstones should
   remain low given the modest buoyancy.

   ...Middle Gulf Coast...
   Relatively rich low-level moisture will stream northward into
   portions of Louisiana and southern Mississippi/southwest Alabama
   during the day today, supporting moderate buoyancy this afternoon. 
   Modestly veering wind profiles may favor some organization with
   a few stronger storms developing within an environment with
   negligible CINH, however poor mid-level lapse rates and generally
   modest low/mid-level flow should tend to limit the severe risk in
   this area. Still, a few instances of small hail and gusty winds
   cannot be ruled out.

   ..Bunting/Lyons.. 10/20/2021

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