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Mesoscale Discussion 1778
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   MESOSCALE DISCUSSION 1778
   NWS STORM PREDICTION CENTER NORMAN OK
   0219 PM CDT TUE SEP 30 2014

   AREAS AFFECTED...WEST-CENTRAL PA AND ADJACENT MD/WV

   CONCERNING...SEVERE POTENTIAL...WATCH UNLIKELY 

   VALID 301919Z - 302045Z

   PROBABILITY OF WATCH ISSUANCE...5 PERCENT

   SUMMARY...ISOLATED INSTANCES OF HAIL...MAINLY SUB-SEVERE...WILL BE
   POSSIBLE THROUGH LATE AFTERNOON/EARLY EARLY EVENING ACROSS
   WEST-CENTRAL PA AND IMMEDIATELY ADJACENT PARTS OF MD/WV.

   DISCUSSION...ISOLATED/WIDELY SCATTERED LOW-TOPPED THUNDERSTORMS HAVE
   INCREASED SINCE EARLY AFTERNOON PRIMARILY ACROSS WEST-CENTRAL
   PORTIONS OF PA. THESE STORMS ARE OCCURRING COINCIDENT WITH A WEAK
   SURFACE LOW/TROUGH...IMMEDIATELY AHEAD OF AN EASTWARD-MOVING COLD
   FRONT. SCENARIO IS BEING INFLUENCED BY AN AMPLIFYING SHORTWAVE
   TROUGH/MID-LEVEL SPEED MAXIMA AND ATTENDANT COLD POCKET /-15C TO
   -17C AT 500 MB/ OVER THE LAKE ERIE VICINITY/UPPER OH RIVER VALLEY.
   WHILE THE BOUNDARY LAYER IS NOT PARTICULARLY MOIST/UNSTABLE AHEAD OF
   THE COLD FRONT...INITIALLY CLOUD-FREE SKIES HAVE CONTRIBUTED TO
   TEMPERATURES REACHING THE 70S F...WITH MLCAPE ESTIMATED TO BE AS
   HIGH AS 500 J/KG. WHILE THE STRONGEST DEEP-LAYER SHEAR APPEARS TO
   RESIDE ACROSS SOUTHERN PA SOUTHWARD...RELATIVELY STEEP LOW/MID-LEVEL
   LAPSE RATES AND MODEST BUOYANCY MAY ALLOW FOR ISOLATED INSTANCES OF
   HAIL ACROSS THE REGION...WITH MOST OF IT LIKELY TO BE SUB-SEVERE.

   ..GUYER/MEAD.. 09/30/2014


   ATTN...WFO...CTP...LWX...

   LAT...LON   40517858 41627776 41467683 39787731 39547822 40007871
               40517858 

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Page last modified: September 30, 2014
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