MESOSCALE DISCUSSION 1007
   NWS STORM PREDICTION CENTER NORMAN OK
   0240 PM CDT TUE JUN 09 2009
   
   AREAS AFFECTED...PORTIONS OF CENTRAL-ERN NY AND ERN PA
   
   CONCERNING...SEVERE THUNDERSTORM WATCH 355...
   
   VALID 091940Z - 092045Z
   
   THE SEVERE WEATHER THREAT FOR SEVERE THUNDERSTORM WATCH 355
   CONTINUES.
   
   SUBJECTIVE SURFACE ANALYSIS INDICATES A COLD FRONT EXTENDING S FROM
   ROUGHLY N-CENTRAL NY INTO S-CENTRAL NY AND THEN SW INTO THE OH
   VALLEY. A WARM FRONT...WHICH IS LIKELY PARTIALLY REINFORCED BY
   CONVECTIVE OUTFLOW FROM MORNING STORM ACTIVITY...WAS LOCATED OVER
   ERN NY S INTO FAR ERN PA AND THEN TOWARD THE DELMARVA REGION.
   BETWEEN THESE TWO FRONTAL BOUNDARIES...A WEDGE OF HIGHER THETA-E AIR
   IS OBSERVED...CHARACTERIZED BY TEMPERATURES IN THE LOW TO MID
   80S...AND DEWPOINTS IN THE UPPER 60S OVER PA TO MAINLY THE LOW-MID
   60S OVER NY. THIS LOW LEVEL AIRMASS CONTINUES TO CONTRIBUTE TOWARD A
   MODERATELY UNSTABLE ATMOSPHERE...FAVORING STRONG TO SEVERE
   THUNDERSTORM DEVELOPMENT AHEAD OF THE COLD FRONT. 
   
   RECENT STORM TRENDS REVEAL SEVERAL CELLS WITHIN WW 355 DISPLAYING
   SUPERCELL CHARACTERISTICS...WHICH IS SUPPORTED BY EFFECTIVE BULK
   SHEAR VALUES OF 40-50 KT. THESE STORMS WILL POSE A RISK OF LARGE
   HAIL AND DAMAGING WINDS WITHIN THE NARROW WARM SECTOR...BEFORE
   POSSIBLY WEAKENING AS THEY APPROACH FAR ERN NY AND NJ...WHERE COOLER
   MORE STABLE BOUNDARY LAYER AIRMASS RESIDES. IN ADDITION...BACKED LOW
   LEVEL FLOW INVOF THE WARM FRONT IS CONTRIBUTING TOWARD ENHANCED LOW
   LEVEL VERTICAL WIND SHEAR...FAVORING INTENSIFICATION OF LOW LEVEL
   MESOCYCLONES AND POSSIBLE TORNADO RISK AS STORMS INTERACT WITH THE
   BOUNDARY.
   
   ..GARNER.. 06/09/2009
   
   
   ATTN...WFO...ALY...PHI...BGM...CTP...LWX...
   
   LAT...LON   39697861 42967611 42977373 39707639 39697861