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Mesoscale Discussion 1101
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   Mesoscale Discussion 1101
   NWS Storm Prediction Center Norman OK
   0205 PM CDT Tue Jun 20 2017

   Areas affected...Portions of far eastern IA...northern/central
   IL...and northwestern IN

   Concerning...Severe potential...Watch unlikely 

   Valid 201905Z - 202130Z

   Probability of Watch Issuance...20 percent

   SUMMARY...An isolated large hail and damaging wind threat may
   develop this afternoon. Watch issuance is unlikely.

   DISCUSSION...A shortwave trough over WI is embedded within
   large-scale troughing over much of the eastern CONUS. Ascent
   associated with this shortwave trough is encouraging convective
   development along a surface front located across central/eastern IA
   into northern IL as of 19Z. Although low-level moisture remains
   limited across northern/central IL and vicinity, it should prove
   sufficient in combination with strong diurnal heating to maintain
   convection as it moves quickly southeastward through the remainder
   of the afternoon and into this evening. Southwesterly low-level
   winds both strengthen and veer to northwesterly with height, and
   resultant effective bulk shear values of 40-50 kt will support
   organized updrafts.

   Instability should remain limited to around 500-1000 J/kg through
   peak heating, mainly owing to warm mid-level temperatures centered
   around 500 mb per 12Z soundings from DVN and ILX. But, steep low and
   mid-level lapse rates below 500 mb should enhance convective
   downdrafts, with an isolated strong to locally damaging wind threat
   possible with expected scattered thunderstorms. A few instances of
   marginally severe hail may also occur. The previously mentioned warm
   mid-level temperatures may limit more robust updraft intensities,
   and the corresponding severe threat will probably remain too
   isolated/marginal to warrant a watch.

   ..Gleason/Hart.. 06/20/2017

   ...Please see for graphic product...


   LAT...LON   40749145 42139074 42088902 41678758 41048626 39738775
               38919003 39869130 40749145 

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