Updated Mesoscale Discussion on Severe Thunderstorm Watch covering northern Illinois/southeast corner of Wisconsin

Mesoscale Discussion 1471
   NWS Storm Prediction Center Norman OK
   0531 PM CDT Thu Aug 10 2017

   Areas affected...Portions of the upper Great Lakes region

   Concerning...Severe Thunderstorm Watch 445...

   Valid 102231Z - 110000Z

   The severe weather threat for Severe Thunderstorm Watch 445
   continues.

   SUMMARY...A threat of damaging winds and large hail will likely
   continue for at least a few more hours this evening, primarily
   across/near southern portions of WW 445.

   DISCUSSION...Strong to severe thunderstorms have evolved primarily
   towards eastern and southern parts of WW 445 early this evening,
   aided by broad ascent from a compact shortwave trough currently over
   Wisconsin and upper Michigan. The strongest ascent will spread east,
   in turn taking convection over Wisconsin and Lake Michigan towards a
   less favorable thermodynamic environment. As such, these storms will
   likely decrease in intensity as they spread towards lower Michigan.
   Farther south, higher boundary-layer moisture is promoting around
   1000-1500 J/kg of MLCAPE, supportive of more intense convection.
   Along the southern periphery of the mid/upper wave, surface flow is
   more veered; in turn, storm evolution this evening may be
   characterized by transient supercells and multicellular modes, with
   damaging winds the primary threat. However, favorable deep-layer
   shear, owing to vigorous westerlies aloft (upwards of 50 kt at 500
   mb), will encourage occasional updraft organization/rotation in
   stronger, semi-discrete cores. Therefore, a few instances of large
   hail will remain possible across/near southern parts of WW 445 this
   evening.