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Mesoscale Discussion 142
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   Mesoscale Discussion 0142
   NWS Storm Prediction Center Norman OK
   1120 PM CST Mon Feb 06 2017

   Areas affected...Portions of IL...IN...northwest KY

   Concerning...Severe potential...Watch unlikely 

   Valid 070520Z - 070715Z

   Probability of Watch Issuance...5 percent

   SUMMARY...Thunderstorms developing from parts of the middle MS
   Valley to the lower/middle OH Valley through the late evening/early
   overnight hours may produce small hail. A few instances of
   marginally severe hail cannot be ruled out. Watch issuance is not

   DISCUSSION...VAD wind profiles across the region are suggesting a
   broad strengthening of low-level southwesterly flow from the middle
   MS Valley to the lower OH Valley, downstream of weakly phased
   midlevel perturbations over the Central States. Related mass
   convergence within the exit region of a consolidating low-level jet,
   coupled with isentropic ascent along the jet, should promote an
   increase in the coverage/intensity of elevated convection through
   the overnight hours. Isolated thunderstorm activity has already been
   increasing across portions of the region, and further increase is
   expected during the next few hours.

   While inflow layers are forecast to remain rooted above a
   modifying/moistening cool dome at the surface, 00Z soundings across
   the Central U.S. indicate that an elevated mixed layer will continue
   to be advected into the region, before increasingly widespread
   convection overturns related elevated buoyancy. Generally small hail
   may accompany the more robust updrafts, given modest effective shear
   (generally 25-35 kt). The presence of 700-500-mb lapse rates around
   6.5-7.5 C/km may support a few instances of marginally several hail
   with the more discrete cells. The lack of stronger effective shear,
   and lack of stronger elevated buoyancy, will tend to limit the
   severe risk. Also, as interacting convective elements tend to grow
   upscale into small clusters, the severe-hail risk may tend to

   ..Cohen/Hart.. 02/07/2017


   LAT...LON   37788681 39138954 39899097 40599144 40939052 40888839
               40628673 40138589 39328514 38278477 37748531 37788681 

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