MESOSCALE DISCUSSION 0543
   NWS STORM PREDICTION CENTER NORMAN OK
   0115 PM CDT TUE APR 21 2009
   
   AREAS AFFECTED...EASTERN WV AND WESTERN/CENTRAL PORTIONS OF NC/VA
   INTO WESTERN MD/SOUTHERN PA
   
   CONCERNING...SEVERE POTENTIAL...WATCH UNLIKELY 
   
   VALID 211815Z - 212015Z
   
   CORRECTED FOR GEOGRAPHIC HEADER
   
   MAINLY ISOLATED SEVERE POTENTIAL WITH A RISK OF HAIL/GUSTY WINDS
   SHOULD DEVELOP/INCREASE THIS AFTERNOON FROM THE UPSTATE PORTIONS OF
   SC INTO FAR EASTERN WV AND WESTERN/CENTRAL VA INTO WESTERN
   MD/PERHAPS SOUTHERN PA. A WATCH IS NOT EXPECTED.
   
   ON THE PERIPHERY OF GREAT LAKES UPPER TROUGH...SATELLITE IMAGERY
   IMPLIES BAND OF ASCENT NEARING THE APPALACHIANS COINCIDENT WITH A
   WEAK COLD FRONT/WIND SHIFT AT THE SURFACE. DOWNSTREAM AIRMASS ACROSS
   NC/VA/MD CONTINUES TO AGGRESSIVELY MIX...WITH SURFACE TEMPERATURES
   WARMING THROUGH THE 60S/70S F. EASTWARD SHIFTING LARGE SCALE
   ASCENT/STEADY HEIGHT FALLS AND A WARM/WEAKLY CAPPED BOUNDARY LAYER
   ACROSS SC/VA/MD INTO SOUTHERN PA SHOULD LEAD TO INCREASING TSTM
   COVERAGE THE REMAINDER OF THE AFTERNOON...WITH STRONG/LARGELY
   UNDIRECTIONAL DEEP LAYER TROPOSPHERIC FLOW FAVORING A
   LINEAR/MULTICELLULAR ORGANIZATION. WHILE MOISTURE/TOTAL BUOYANCY ARE
   MODEST...A WELL-MIXED BOUNDARY LAYER AND COOL TEMPERATURES
   ALOFT/STEEP LAPSE RATES WILL SUPPORT SEVERE HAIL/GUSTY WIND
   POTENTIAL WITH THE STRONGER LOW-TOPPED TSTMS THIS AFTERNOON. THE
   SEVERE THREAT SHOULD QUICKLY WANE WITH SUNSET. NO WATCH IS
   ANTICIPATED GIVEN THE EXPECTED MARGINAL/ISOLATED NATURE OF THE RISK.
   
   ..GUYER.. 04/21/2009
   
   
   ATTN...WFO...AKQ...CTP...LWX...RAH...RNK...PBZ...RLX...GSP...
   
   LAT...LON   35517946 35378146 36548064 38837973 40117775 38687724
               36867772 35517946