US Mesoscale Discussions

Storm Prediction Center Mesoscale Discussion 1381

   Mesoscale Discussion 1381
   NWS Storm Prediction Center Norman OK
   1043 PM CDT Sat Jun 22 2024

   Areas of west central through northern
   Illinois...southwestern lower Michigan...northwestern Indiana

   Concerning...Severe Thunderstorm Watch 447...

   Valid 230343Z - 230545Z

   The severe weather threat for Severe Thunderstorm Watch 447

   SUMMARY...An evolving line of storms may pose some further increase
   in potential for strong to severe surface gusts for another hour or
   two.  But this appears likely to diminish after around 1 or 2 AM
   CDT, as storms weaken while continuing east-southeastward through
   the southern Great Lakes/Ohio Valley vicinity.  A new severe weather
   watch is not anticipated, but trends will continue to be monitored.

   DISCUSSION...Convection has been gradually consolidating into a line
   generally coincident with strengthening low-level frontogenetic
   forcing.  This trails a developing surface cyclone now migrating
   across Lake Michigan into lower Michigan, and will continue to
   slowly advance east-southeastward across the southern Lake Michigan
   and northern Illinois vicinity into the overnight hours. 

   Although subtle low-level moisture return is still possible
   immediately ahead the evolving line, beneath a 30-40 kt
   west-southwesterly jet around 850 mb, the downstream boundary-layer,
   in general, is somewhat drier and characterized by increasingly weak
   potential instability beneath relatively warm mid-level air.   So,
   it appears that ongoing convection could maintain intensity, or
   perhaps intensify a bit further, with sub-cloud evaporative cooling
   contributing to downward mixing of momentum and a few strong to
   severe surface gusts during the next couple of hours.  However,
   beyond 06-07Z, this seems likely to diminish as convection begins to

   ..Kerr.. 06/23/2024

   ...Please see for graphic product...


   LAT...LON   41419007 41668932 41848824 42018665 42558619 42358539
               41258707 40818876 40019060 40789076 41129045 41419007 

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