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Mesoscale Discussion 757
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   Mesoscale Discussion 0757
   NWS Storm Prediction Center Norman OK
   0104 PM CDT Thu May 18 2017

   Areas affected...Portions of northern PA...much of upstate/western
   NY...and VT

   Concerning...Severe potential...Watch possible 

   Valid 181804Z - 182000Z

   Probability of Watch Issuance...60 percent

   SUMMARY...A threat for isolated damaging winds and large hail should
   increase over the next several hours as thunderstorms develop across
   western NY and vicinity. Watch issuance is possible.

   DISCUSSION...The glancing influence of ascent associated with an
   upper trough over the upper Great Lakes and low-level convergence
   along a lake-breeze boundary has proven sufficient to initiate
   isolated convection across far western NY as of 1745Z. MLCAPE has
   increased into the 1000-1500 J/kg range across northwestern PA into
   much of upstate/western NY as diurnal heating has boosted surface
   temperatures into the low to mid 80s. Generally southwesterly
   low-level flow increases at mid-levels to 40-50 kt, and resultant
   effective bulk shear of 30-45 kt will support organized updrafts
   with both a damaging wind and large hail threat. Initially discrete
   convection should grow upscale into short line segments/bows through
   the late afternoon and early evening, with strong to damaging winds
   possibly becoming the primary threat. If isolated convection
   increases in coverage as expected over the next several hours, then
   watch issuance may be needed.

   ..Gleason/Goss.. 05/18/2017

   ...Please see for graphic product...


   LAT...LON   41158002 42028048 42757891 43567641 44147635 44687563
               45047493 45097369 45087226 44077231 42867314 42327445
               41767689 41158002 

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