MESOSCALE DISCUSSION 1209
   NWS STORM PREDICTION CENTER NORMAN OK
   0231 PM CDT THU JUN 18 2009
   
   AREAS AFFECTED...CENTRAL VA INTO THE DELMARVA REGION
   
   CONCERNING...SEVERE THUNDERSTORM WATCH 464...
   
   VALID 181931Z - 182030Z
   
   THE SEVERE WEATHER THREAT FOR SEVERE THUNDERSTORM WATCH 464
   CONTINUES.
   
   THE THREAT FOR LARGE HAIL/DAMAGING WINDS AND EVEN AN ISOLATED
   TORNADO CONTINUE FOR WW 464 FROM CENTRAL PORTIONS OF VA INTO THE
   DELMARVA REGION.
   
   HI RES RADAR IMAGERY AT 19Z SHOWED SEVERAL INTENSE THUNDERSTORMS
   ALONG A LINE FROM NEAR UPPER MARLBORO MD SSW TOWARD LA PLATA MD AND
   THEN INTO BOWLING GREEN VA. SEVERAL OF THESE STORMS ARE
   SUPERCELLS...POSSESSING LARGE REFLECTIVITY CORES WHICH RESIDE WITHIN
   THE HAIL GROWTH ZONE. SUBJECTIVE SURFACE ANALYSIS INDICATES A WEAK
   AREA OF LOW PRESSURE CENTERED OVER S CENTRAL-SERN PA...WITH A COLD
   FRONT EXTENDING SSW INTO SW VA...AND A WARM FRONT EXTENDING SSE FROM
   THE LOW TOWARDS THE COASTAL WATERS OF MD/VA. A BAND OF 40-50 KT WNW
   MID LEVEL FLOW IS DEPICTED IN RUC GUIDANCE AND AREA VWP DATA...WHICH
   IS CONTRIBUTING TOWARD FAVORABLE /40+ KT/ EFFECTIVE BULK SHEAR FOR
   SUPERCELL DEVELOPMENT. IN ADDITION...LOW LEVEL SHEAR IS MAXIMIZED
   ALONG AND TO THE COOL SIDE OF THE SURFACE WARM FRONT /0-1 KM SRH AOA
   200 M2 PER S2/...WHICH MAY RESULT IN THE DEVELOPMENT OF STRONG LOW
   LEVEL UPDRAFT ROTATION IF STORMS MANAGE TO INTERACT WITH THE
   BOUNDARY...SUGGESTING THAT SOME POTENTIAL FOR AN ISOLATED TORNADO
   EXISTS. OTHERWISE...A CONTINUED THREAT FOR LARGE HAIL AND DAMAGING
   WINDS APPEARS LIKELY DURING THE NEXT SEVERAL HOURS WITH THE STRONGER
   UPDRAFT CORES.
   
   ..GARNER.. 06/18/2009
   
   
   ATTN...WFO...PHI...AKQ...LWX...RAH...
   
   LAT...LON   38087824 39397539 37377541 36077824 38087824