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Mesoscale Discussion 1009
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   Mesoscale Discussion 1009
   NWS Storm Prediction Center Norman OK
   1118 AM CDT Tue Jun 13 2017

   Areas affected...Portions of OH/IN/KY/WV/VA/MD/PA

   Concerning...Severe potential...Watch unlikely 

   Valid 131618Z - 131845Z

   Probability of Watch Issuance...5 percent

   SUMMARY...An isolated damaging wind risk could accompany the
   strongest storms across portions of the lower Great Lakes and
   middle/upper Ohio Valley region through the afternoon. Watch
   issuance will not be needed.

   DISCUSSION...Subtle low-level confluence per surface observations
   and plan-view depictions of 1-km-above-ground flow per VAD wind
   profiles, amid a very weakly capped and moist boundary layer, are
   already supporting isolated to scattered thunderstorm development.
   The Wilmington and Pittsburgh 12Z soundings sampled around 13.0-14.5
   g/kg mean mixing ratios, highlighting the ample moisture
   contributing to appreciable buoyancy, with diurnal heating
   supporting MLCAPE upwards of 2000 J/kg. Where convective overturning
   has not already been abundant, insolation continues to contribute to
   steepening low-level lapse rates, allowing MLCAPE, as well as DCAPE,
   to increase. As such, convection should experience an overall
   increase in coverage/intensity into the afternoon, with the
   potential for isolated damaging wind gusts.

   Given around 1000 J/kg of DCAPE indicated by the aforementioned
   soundings suggesting the potential for strong convective outflow
   (with further diurnal gains in DCAPE ongoing), and given moderate
   midlevel lapse rates implying some enhancement to convective-scale
   upward accelerations, isolated strong to damaging wind gusts will be
   possible through the afternoon -- especially with cell mergers and
   local outflow amalgamation and as cells collapse. However, deep
   shear is very weak -- with midlevel wind speeds generally 15 kt or
   less. As such, convective organization will be greatly lacking,
   which should limit severe coverage.

   ..Cohen/Hart.. 06/13/2017

   ...Please see for graphic product...


   LAT...LON   37408365 38078552 38988710 40668725 41378573 41178203
               40247969 37917909 36798027 36948228 37408365 

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