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Mesoscale Discussion 1304
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MD 1304 graphic

   Mesoscale Discussion 1304
   NWS Storm Prediction Center Norman OK
   0133 PM CDT Thu Jul 13 2017

   Areas affected...Central Pennsylvania eastward to central New Jersey

   Concerning...Severe potential...Watch likely 

   Valid 131833Z - 131930Z

   Probability of Watch Issuance...80 percent

   SUMMARY...Convection has increased recently beneath a mid-level
   vorticity maximum across central Pennsylvania.  These storms should
   spread southeastward over the course of the afternoon.  A WW will
   likely be needed for this activity.

   DISCUSSION...Recent radar mosaic/satellite imagery indicates that
   convection has increased near/just southeast of CTP, with one
   supercellular structure noted about 20 mi east-southeast of CTP at
   this time.  Forcing for ascent supporting this convection is not
   particularly clear, but appears to be tied to a remnant vorticity
   maximum from earlier convection centered over western New York. 
   Mid/upper cloud cover has been extensive across western portions of
   the discussion area, although breaks in this cloud deck have
   fostered increasing (mid/upper 80s F) surface temperatures along
   with an attendant increase in surface based instability especially
   with southeastward extent into New Jersey.  

   With time, storms should maintain (or perhaps increase) in intensity
   as they migrate toward greater instability in southeastern
   Pennsylvania and New Jersey.  Damaging wind gusts are the primary
   threat with this activity, although isolated instances of hail may
   occur especially with storms that can acquire updraft rotation.  A
   WW issuance will likely be issued for this activity by 19Z/3p

   ..Cook/Darrow.. 07/13/2017

   ...Please see for graphic product...


   LAT...LON   40917768 41147708 41347637 41487542 41287492 40777464
               40467424 40127408 39667422 39537481 39717563 40047674
               40257747 40447769 40567777 40917768 

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