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Mesoscale Discussion 919
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   Mesoscale Discussion 0919
   NWS Storm Prediction Center Norman OK
   1103 AM CDT Tue May 30 2017

   Areas affected...Parts of western and central PA...southwest into
   central NY...and southward to the eastern WV Panhandle

   Concerning...Severe potential...Watch possible 

   Valid 301603Z - 301830Z

   Probability of Watch Issuance...60 percent

   SUMMARY...New thunderstorm development is expected across western PA
   into southwest NY and southward some into WV by early afternoon
   (around 17Z), with one or more lines of storms and perhaps clusters
   spreading east today.  Damaging winds and hail will be the primary
   severe-weather threats.

   DISCUSSION...Trends in satellite imagery indicated ongoing cumulus
   formation this morning from the Upper Ohio Valley into WV, toward
   central PA and west/southwest NY, as surface heating and low-level
   moistening has weakened inhibition.  Late morning radar imagery
   showed some thunderstorm development within convection along and
   parallel to the higher terrain from the eastern WV Panhandle through
   central PA to south-central NY.  This activity was located within an
   area of low-level confluence, and the eastern extent of stronger
   instability analyzed over the western PA/Upper Ohio Valley region.

   Strengthening west-southwesterly 500-mb winds with the approach of a
   MI/IN/OH shortwave trough will support increasing effective bulk
   shear for organized storms.  In addition, an increase in forcing for
   ascent with this trough across the discussion area this afternoon
   into the evening will augment ascent along an eastward-moving front
   and aforementioned confluence zone to support more robust
   convection/thunderstorm development.  The degree of instability and
   bulk shear suggest damaging winds and hail will be the primary
   severe threats.  Long, straight hodographs suggest splitting storms
   will be possible, while low-level curvature could prove sufficient
   for a tornado threat too.

   ..Peters/Hart.. 05/30/2017

   ...Please see for graphic product...


   LAT...LON   39657968 40637969 41077969 42227860 42797757 42977676
               42737632 42217640 41567701 40527775 39677818 39337855
               39147918 39217942 39657968 

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