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Mesoscale Discussion 1500
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   MESOSCALE DISCUSSION 1500
   NWS STORM PREDICTION CENTER NORMAN OK
   1153 AM CDT TUE JUL 21 2015

   AREAS AFFECTED...PENNSYLVANIA...NEW YORK...VERMONT

   CONCERNING...SEVERE POTENTIAL...WATCH UNLIKELY 

   VALID 211653Z - 211800Z

   PROBABILITY OF WATCH ISSUANCE...20 PERCENT

   SUMMARY...FURTHER INTENSIFICATION OF FRONTAL/PRE-FRONTAL
   THUNDERSTORM ACTIVITY IS POSSIBLE AS IT ADVANCES SOUTHEASTWARD THIS
   AFTERNOON.  SOME OF THIS MAY BE ACCOMPANIED BY LOCALIZED WIND GUSTS
   THAT MAY REMAIN MOSTLY BELOW SEVERE CRITERIA...BUT COULD
   NEVERTHELESS RESULT IN SPORADIC DAMAGE OF AND RELATING TO
   TREES/NEARBY POWER LINES.  A WATCH IS NOT CURRENTLY
   ANTICIPATED...BUT TRENDS WILL CONTINUE TO BE MONITORED.

   DISCUSSION...SCATTERED THUNDERSTORM DEVELOPMENT IS NOW WELL UNDERWAY
   TO THE LEE OF THE LOWER GREAT LAKES.  LOCALLY ENHANCED LOW-LEVEL
   CONVERGENCE ALONG THE LAKE BREEZES AND THE SOUTHEASTWARD ADVANCING
   COLD FRONT MAY BE CONTRIBUTING TO THIS ACTIVITY...BUT FORCING
   ASSOCIATED WITH A FAIRLY VIGOROUS SHORT WAVE IMPULSE PIVOTING
   INTO/THROUGH THE LOWER GREAT LAKES REGION MAY BE MORE PROMINENT.

   OVERALL...THE ENVIRONMENT DOES NOT APPEAR PARTICULARLY CONDUCIVE TO
   SEVERE STORM DEVELOPMENT GIVEN THERMODYNAMIC PROFILES CHARACTERIZED
   BY RATHER WEAK TO MODEST LOWER/MID TROPOSPHERIC LAPSE RATES AND
   CAPE.  A 40-50 KT SOUTHWESTERLY 500 MB JET STREAK IS CONTRIBUTING TO
   STRONG DEEP LAYER SHEAR...BUT LOW-LEVEL FLOW APPEARS RATHER
   WEAK...AND LOWER/MID TROPOSPHERIC MEAN FLOW IS PROBABLY GENERALLY
   ONLY ON THE ORDER OF 30 KT OR LESS.

   STILL...WITH ADDITIONAL BOUNDARY LAYER HEATING AND MIXING LIKELY IN
   ADVANCE OF THE COLD FRONT AND ASSOCIATED EVOLVING BROKEN CONVECTIVE
   LINE...FURTHER INTENSIFICATION OF STORMS DOES SEEM PROBABLE THROUGH
   18-21Z...AS ACTIVITY SPREADS THROUGH THE CHAMPLAIN INTO HUDSON
   VALLEYS...TOWARD THE CATSKILLS AND POCONOS...AND ACROSS THE
   ALLEGHENY MOUNTAINS/ADJACENT AREAS OF CENTRAL AND SOUTHWESTERN
   PENNSYLVANIA.

   ..KERR/CORFIDI.. 07/21/2015


   ATTN...WFO...BTV...ALY...PHI...BGM...CTP...PBZ...

   LAT...LON   40947840 41757685 42237597 43267440 44237367 44957259
               44687223 42627355 41137534 39957823 40228036 40947840 

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Page last modified: July 21, 2015
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