MESOSCALE DISCUSSION 1193
   NWS STORM PREDICTION CENTER NORMAN OK
   1103 AM CDT SUN JUN 12 2011
   
   AREAS AFFECTED...PARTS OF THE ERN W VA PNHDL...S CNTRL PA...CNTRL MD
   AND NRN VA
   
   CONCERNING...SEVERE POTENTIAL...WATCH POSSIBLE 
   
   VALID 121603Z - 121730Z
   
   STORMS ARE EXPECTED TO INCREASE IN COVERAGE DURING THE NEXT FEW
   HOURS...AND MAY IMPACT AREAS NEAR/EAST OF CHARLOTTESVILLE...
   NORTHWARD THROUGH WASHINGTON D.C./BALTIMORE...AND HARRISBURG/
   LANCASTER...DURING THE 18-21Z TIME FRAME.  THE SEVERE THREAT MAY BE
   A BIT MARGINAL...BUT TRENDS WILL CONTINUE TO BE MONITORED.
   
   THUNDERSTORMS ARE BEGINNING TO INITIATE NEAR THE ALLEGHENY
   MOUNTAINS...NEAR OR JUST AHEAD OF A SLOWLY SOUTHEASTWARD ADVANCING
   COLD FRONT.  WEAKLY DIFLUENT AND DIVERGENT UPPER FLOW ON THE
   SOUTHERN PERIPHERY OF A MID/UPPER CLOSED LOW MIGRATING EAST OF THE
   LOWER GREAT LAKES REGION MAY BE CONTRIBUTING TO DEVELOPMENT... WHICH
   APPEARS LIKELY TO PERSIST AND INCREASE FURTHER INTO THE AFTERNOON
   HOURS.  ALTHOUGH COOL SURFACE RIDGING EXTENDING SOUTHWARD INTO
   NORTHERN MID ATLANTIC COASTAL AREAS MAY BE SLOW MODIFY...SURFACE
   HEATING AND WEAK MOIST UPSLOPE FLOW ALONG THE EASTERN SLOPES OF THE
   ALLEGHENIES SOUTHWARD INTO THE VICINITY OF THE BLUE RIDGE MOUNTAINS
   ARE CONTRIBUTING TO STEEPENING LAPSE RATES AND BOUNDARY LAYER
   DESTABILIZATION.  AS A RESULT...STRONGEST CONVECTION APPEARS LIKELY
   TO DEVELOP SOUTHEASTWARD ALONG AND SOUTH OF AN EFFECTIVE WARM
   FRONTAL ZONE TOWARD THE CHESAPEAKE BAY REGION.
   
   GUIDANCE IS SUGGESTIVE THAT RELATIVELY WARM MID-LEVEL TEMPERATURES
   WILL LIMIT CAPE TO RELATIVELY MODEST VALUES OF 1500 TO 2000
   J/KG...GREATEST NEAR SURFACE TROUGHING EAST OF THE BLUE
   RIDGE...PERHAPS AS FAR NORTH AS THE WASHINGTON D.C./BALTIMORE
   METROPOLITAN AREAS.  SO STORM INTENSIFICATION MAY NOT BE
   PARTICULARLY RAPID...BUT STRENGTHENING OF 500 MB FLOW TO AROUND 30
   KT ON THE SOUTHERN FRINGE OF THE STRONGER WESTERLIES MAY INCREASE
   VERTICAL SHEAR SUFFICIENTLY TO SUPPORT AN UPSCALE CONVECTIVE GROWTH
   INTO AN ORGANIZING STORM CLUSTER.  THIS COULD EVENTUALLY YIELD A
   STRONG ENOUGH COLD POOL TO SUPPORT A RISK FOR POTENTIALLY DAMAGING
   WIND GUSTS.  OTHERWISE...FREQUENT CLOUD TO GROUND LIGHTNING IN THE
   STRONGER CELLS MAY BE THE PRIMARY HAZARD.
   
   ..KERR.. 06/12/2011
   
   
   ATTN...WFO...PHI...AKQ...CTP...LWX...PBZ...RLX...
   
   LAT...LON   40637770 40417698 39677613 39087601 38397676 37967754
               37867849 38157906 38657942 39037933 39607911 40007884
               40637770