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Mesoscale Discussion 1508
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   Mesoscale Discussion 1508
   NWS Storm Prediction Center Norman OK
   0235 PM CDT Wed Aug 16 2017

   Areas affected...Eastern Iowa...Western Illinois...Eastern Missouri

   Concerning...Severe potential...Watch unlikely 

   Valid 161935Z - 162200Z

   Probability of Watch Issuance...20 percent

   SUMMARY...A potential for wind damage and hail will be possible late
   this afternoon from eastern Iowa southward across western Illinois
   into far eastern Missouri. The severe threat should remain isolated
   and weather watch issuance appears unlikely.

   DISCUSSION...The latest surface analysis shows a 1006 mb low over
   western Iowa with a very moist airmass located eastward and
   southward from the low across much of Iowa into northeast Missouri
   into northwest Illinois. Surface dewpoints are generally in the
   lower to mid 70s F and temperatures have risen into the lower 80s F
   across much of the area. This is contributing to between 1000 and
   1500 J/kg of MLCAPE according to the RAP. In addition, water vapor
   imagery shows a pronounced dry slot moving into southwestern Iowa
   and northwestern Missouri. Ahead of this feature, strong large-scale
   ascent and moderate deep-layer shear could be enough for an isolated
   severe threat with wind damage and hail possible.

   Further to the south across eastern Missouri, the RAP is showing
   stronger instability with MLCAPE values in the 1500 to 2000 J/kg
   range. In addition, the St. Louis, MO WSR-88D VWP shows 0-6 km shear
   at around 30 kt with some directional shear in the low-levels. This
   will be enough for an isolated severe threat. Wind damage will be
   possible with the faster moving line segments. An isolated rotating
   storm with large hail will also be possible.

   ..Broyles/Weiss.. 08/16/2017

   ...Please see for graphic product...


   LAT...LON   41308943 42949102 42959223 42499277 42069260 41019197
               40109175 38639177 38009152 37709061 38318929 39848900

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