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Mesoscale Discussion 1367
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   Mesoscale Discussion 1367
   NWS Storm Prediction Center Norman OK
   0333 PM CDT Thu Jul 20 2017

   Areas affected...Portions of central and eastern PA...northern
   NJ...southeastern NY...far western CT

   Concerning...Severe potential...Watch possible 

   Valid 202033Z - 202200Z

   Probability of Watch Issuance...40 percent

   SUMMARY...A cluster of thunderstorms currently pushing south and
   east into northern PA is expected to continue into northeastern PA
   through the afternoon and early evening. Additional thunderstorms
   are currently developing over southeastern NY, western MA, and
   northwestern CT, and will continue to develop in this area over the
   next hour. Severe wind gusts and hail are the main threat.  A Watch
   may be needed in the next hour or two over portions of the area.

   DISCUSSION...A cluster of thunderstorms, some that continue to
   exhibit supercell structures and transient rotation, will continue
   to move into northeastern PA in the next few hours. Substantial
   destabilization has occurred south of these storms in central PA,
   which should help maintain the current intensity of the storms
   despite some anvil shading and somewhat lower instability noted
   currently in northeast PA.

   Farther northeast, thunderstorms are developing rapidly ahead of a
   sagging front/pre-frontal trough over southeastern NY, western MA,
   and northwestern CT in a region not affected by the cirrus shield
   over nearby areas.

   Both of the more concentrated areas of convection noted above will
   continue to evolve within substantial bulk vertical wind shear of
   45-55 kt, which has supported rotation within the stronger storms
   through much of the afternoon.  The largest threat for severe wind
   gusts and hail will be associated with these areas of rotation, but
   low-level lapse rates AOA 8 C/KM over most of the area could support
   severe wind gusts outside of the areas of rotation, within the
   strongest downdrafts.  A Severe Thunderstorm Watch may be needed
   within the next hour or two over portions of the area to address the
   above concerns.

   ..Coniglio/Cohen/Hart.. 07/20/2017

   ...Please see www.spc.noaa.gov for graphic product...

   ATTN...WFO...BOX...OKX...ALY...PHI...BGM...CTP...

   LAT...LON   42477506 42697208 42237190 41557186 40447409 40187562
               40217660 40357722 40837751 41327755 41937651 42477506 

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Page last modified: July 20, 2017
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