Mesoscale Discussion 1485
   NWS Storm Prediction Center Norman OK
   0320 PM CDT Wed Aug 11 2021

   Areas affected...Portions of northern Lower MI

   Concerning...Severe potential...Watch likely 

   Valid 112020Z - 112215Z

   Probability of Watch Issuance...80 percent

   SUMMARY...The threat for scattered damaging wind gusts and perhaps
   isolated tornadoes should increase this afternoon. Watch issuance is
   likely.

   DISCUSSION...Supercells that formed earlier this afternoon over
   north-central WI have recently begun to grow upscale into a cluster
   as they move over northern Lake Michigan. A separate cluster ongoing
   over the eastern U.P. of MI should continue moving eastward, mainly
   across Lake Huron and southern Ontario. The airmass across much of
   northern Lower MI was unaffected by a convective cluster that
   occurred further south today, with surface temperatures recently
   warming into the at least low to mid 80s across northern Lower MI.
   The presence of rich low-level moisture and modestly steepened
   mid-level lapse rates are contributing to around 2000-2500 J/kg of
   MLCAPE. 35-45 kt of deep-layer shear associated with an upper trough
   and related west-southwesterly mid-level jet will likely continue to
   support storm organization as the northeastern WI cluster moves
   eastward over the next couple of hours. Given the mainly linear mode
   expected, scattered damaging wind gusts should be the main threat.
   Around 100 m2/s2 of 0-1 km SRH may also support an isolated/brief
   tornado threat as well. With expectations for an increasing severe
   threat through the remainder of the afternoon, watch issuance is
   likely in the next hour or so.

   ..Gleason/Thompson.. 08/11/2021

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

   ATTN...WFO...APX...

   LAT...LON   44218639 44788631 45498543 45848477 45828364 45358257
               44218231 44218639