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Mesoscale Discussion 73
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   Mesoscale Discussion 0073
   NWS Storm Prediction Center Norman OK
   0243 AM CST Tue Feb 20 2018

   Areas affected...portions of Iowa into southeast Minnesota and
   portions of western Wisconsin

   Concerning...Freezing rain 

   Valid 200843Z - 201145Z

   SUMMARY...Freezing rain/mixed wintry precipitation will continue
   spreading northeast across portions of Iowa and adjacent southeast
   Minnesota, and spreading into western/southwestern Wisconsin over
   the next 1-2 hours.

   DISCUSSION...Latest radar loop shows a band of heavier precipitation
   -- including occasional/embedded lightning -- continuing to shift
   northeast across central and eastern Iowa and adjacent southeast
   Minnesota at this time.  The precipitation is occurring within a
   zone of warm advection, with QG ascent bolstered by a compact vort
   max whose center of circulation is indicated in water vapor imagery
   to be shifting into southwest Iowa at this time.  While the rather
   fast motion of the precipitation field is limiting duration of
   heavier amounts at any one locale, briefly moderate to heavy rain --
   where surface temperatures are largely in the upper 20s to low 30s
   -- will continue to allow icing to occur.  

   Latest model runs -- in particular several hi-res CAMs -- suggest
   steady or even diminishing precipitation intensity over the next few
   hours.  In addition, an axis of above-freezing surface temperatures
   are apparent along the Mississippi Valley northward into southwest
   Wisconsin/northeast Iowa.  Still, moderate to briefly heavy freezing
   rain will occur across portions of the area -- as highlighted by the
   MCD graphic -- over the next few hours.

   ..Goss.. 02/20/2018

   ...Please see for graphic product...


   LAT...LON   44809034 44259005 43779037 43249161 42639213 41489252
               40849303 40969353 43099313 44089261 44859147 44809034 

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