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

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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

   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


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