Mesoscale Discussion 1340
   NWS Storm Prediction Center Norman OK
   0121 PM CDT Sat Jul 24 2021

   Areas affected...Much of central and southern lower Michigan into
   adjacent portions of northwestern Ohio and northern Indiana

   Concerning...Severe potential...Watch possible 

   Valid 241821Z - 242015Z

   Probability of Watch Issuance...60 percent

   SUMMARY...At least scattered thunderstorm development still appears
   probable, now mostly likely around 4-6 PM EDT, with the potential to
   organize into clusters capable of producing damaging wind gusts. 
   Trends continue to be monitored for the possibility of a severe
   weather watch.

   DISCUSSION...Initial attempts at intensifying thunderstorm
   development across/east of the Houghton Lake vicinity appear to be
   waning, perhaps due to weakening of the trailing mid-level cyclonic
   vorticity center.  However, the boundary layer across much of
   central and southern lower Michigan remains moist, modestly unstable
   and weakly inhibited, to the south of the effective warm frontal
   zone, and ahead of conglomerate convective outflow trailing across
   northern Lake Michigan through southern Wisconsin.  

   Although the mid-level trough axis is in the process of shifting
   across and northeast of the Lake Huron/Georgian Bay vicinity,
   moderately strong (40+ kt around 500 mb) west-northwesterly
   mid-level flow will maintain strong deep-layer shear across the
   region into this evening.  Beneath this regime, it still appears
   that continuing daytime heating will support the initiation of at
   least scattered thunderstorm activity, perhaps focused on the lake
   breeze advancing inland off Lake Michigan.  Aided by the shear, this
   activity may tend to grow upscale, with organizing clusters posing a
   risk for potentially damaging wind gusts.

   ..Kerr/Hart.. 07/24/2021

   ...Please see www.spc.noaa.gov for graphic product...

   ATTN...WFO...DTX...APX...IWX...GRR...LOT...

   LAT...LON   41798656 42398606 43928602 44548520 43718306 42148299
               41198652 41448715 41798656