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Mesoscale Discussion 1489
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   MESOSCALE DISCUSSION 1489
   NWS STORM PREDICTION CENTER NORMAN OK
   0509 PM CDT SUN JUL 27 2014

   AREAS AFFECTED...PARTS OF SRN NEW YORK...CNTRL/ERN PA...PARTS OF
   ADJACENT MARYLAND AND NEW JERSEY

   CONCERNING...SEVERE POTENTIAL...WATCH LIKELY 

   VALID 272209Z - 272315Z

   PROBABILITY OF WATCH ISSUANCE...80 PERCENT

   SUMMARY...CONVECTION IS LIKELY TO INCREASE IN COVERAGE WHILE
   SPREADING EAST NORTHEASTWARD ACROSS THE REGION INTO THE 00-03Z TIME
   FRAME.  THIS COULD BE ACCOMPANIED BY AN INCREASING SEVERE WEATHER
   RISK...MAINLY IN THE FORM OF STRONG WIND GUSTS...BUT IT REMAINS
   UNCERTAIN HOW ORGANIZED THIS THREAT WILL BECOME.

   DISCUSSION...MODIFICATION OF THE LOWER/MID TROPOSPHERIC ENVIRONMENT
   IN THE WAKE OF EARLY DAY DRYING...NORTHEAST OF THE UPPER OHIO VALLEY
   INTO AREAS EAST OF THE LOWER GREAT LAKES...IS SLOWLY UNDERWAY.  THE
   LEADING EDGE OF THE BETTER MOISTURE RETURN...AS EVIDENT IN THE
   PRECIPITABLE WATER FIELDS...GENERALLY COINCIDES WITH AN AREA OF
   INCREASING THUNDERSTORM ACTIVITY EXTENDING ALONG AN AXIS EAST
   NORTHEAST OF CLEVELAND OH INTO AREAS WEST OF LANCASTER PA. 
   LOW-LEVEL FOCUS FOR CONVECTIVE DEVELOPMENT APPEARS
   WEAK/UNCERTAIN...BUT ACTIVITY TO THE LEE OF LAKE ERIE IS LIKELY
   BEING AIDED BY STRENGTHENING DIVERGENCE IN THE LEFT EXIT REGION OF A
   SEASONABLY STRONG HIGH LEVEL JET NOSING THROUGH THE OHIO VALLEY. 
   MODELS SUGGEST THIS UPPER FORCING WILL CONTINUE TO INCREASE ALONG AN
   AXIS ROUGHLY EAST SOUTHEASTWARD ALONG THE NEW YORK/PENNSYLVANIA
   BORDER THROUGH LATE EVENING.  THIS IS GENERALLY NORTH OF THE
   STRONGER MID-LEVEL FLOW AND THE BETTER SHEAR PROFILES FOR ORGANIZED
   SEVERE STORM DEVELOPMENT.  BUT AS MODERATELY LARGE CAPE DEVELOPS
   EAST NORTHEASTWARD...IT DOES NOT APPEAR OUT OF THE QUESTION THAT
   INCREASING STORM DEVELOPMENT COULD BE ACCOMPANIED BY AT LEAST SOME
   INCREASE IN RISK FOR POTENTIALLY DAMAGING WIND GUSTS.

   ..KERR/EDWARDS.. 07/27/2014


   ATTN...WFO...PHI...BGM...BUF...CTP...LWX...PBZ...

   LAT...LON   42297931 42527693 42287531 41407474 40157543 39547680
               39687868 41147921 42297931 

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Page last modified: July 27, 2014
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