MESOSCALE DISCUSSION 0763
   NWS STORM PREDICTION CENTER NORMAN OK
   0328 PM CDT THU MAY 12 2011
   
   AREAS AFFECTED...SRN WV...WRN VA...FAR NERN TN...WRN/CNTRL NC...MUCH
   OF SC...FAR NERN GA
   
   CONCERNING...SEVERE POTENTIAL...WATCH UNLIKELY 
   
   VALID 122028Z - 122230Z
   
   ISOLATED SVR TSTMS WITH LARGE HAIL AND DMGG WINDS WILL BE POSSIBLE
   THROUGH LATE AFTERNOON ACROSS SRN PORTIONS OF THE APPALACHIANS AND
   ADJACENT AREAS OF THE MIDDLE ATLANTIC AND SOUTHEAST.
   
   MID-AFTERNOON SFC ANALYSIS REVEALS A STATIONARY FRONT EXTENDING FROM
   NWRN WV SSEWD INTO ERN SC. AN EXPANSIVE STRATUS DECK TO THE EAST OF
   THIS BOUNDARY IS YIELDING AMPLE CINH FOR SFC-BASED PARCELS...WHILE
   AT LEAST POCKETS OF INSOLATION WEST OF THE BOUNDARY AMIDST SFC
   DEWPOINTS IN THE 60S HAVE YIELDED A MODERATELY UNSTABLE AIR MASS
   WITH MLCAPE VALUES OF 1000-2000 J/KG. UPSLOPE FLOW INVOF THE BLUE
   RIDGE HAS RESULTED IN THE RECENT INITIATION OF DEEP CONVECTION OVER
   WRN PORTIONS OF NC. MEANWHILE...ASCENT ASSOCIATED WITH A WEAK
   MID-LEVEL IMPULSE CRESTING THE ERN CONUS RIDGE HAS SUPPORTED THE
   DEVELOPMENT OF CONVECTION FARTHER NORTH INTO SRN WV AND WRN VA. ALL
   OF THIS ACTIVITY WILL CONTINUE TO BE STEERED SSEWD THROUGH THE
   AFTERNOON...WITH ADDITIONAL DEVELOPMENT EXPECTED OVER HIGHER TERRAIN
   AND INVOF THE FRONT.
   
   TWO SEPARATE SPATIAL REGIMES FOR ISOLATED SVR CONVECTION WILL EXIST:
   
   1. TO THE WEST OF THE FRONT...A PRIMARILY MULTICELLULAR CONVECTIVE
   MODE WILL BE FAVORED WITH SURFACE-BASED CONVECTION...GIVEN THAT THE
   STRONGEST MID-LEVEL FLOW IS DISPLACED FARTHER TO THE EAST. THIS WILL
   LIKELY MITIGATE THE OVERALL THREAT FOR STORM PERSISTENCE/SUSTENANCE.
   ISOLATED INCIDENTS OF LARGE HAIL WILL BE POSSIBLE GIVEN THE DEGREE
   OF UPWARD BUOYANCY...WITH AN ESTIMATE OF PENNY SIZE HAIL ALREADY
   REPORTED IN HENDERSON COUNTY NC. SFC TEMPERATURE-DEWPOINT SPREADS IN
   EXCESS OF 15-20F IN MANY AREAS COULD ALSO YIELD A THREAT FOR DMGG
   WINDS. 
   
   2. TO THE EAST OF THE FRONT...CONVECTION WILL BE ROOTED ATOP A
   STABLE LAYER...WITH AN ISOLATED THREAT FOR LARGE HAIL. THE ABSENCE
   OF ANY APPRECIABLE SFC-BASED INSTABILITY AND THE WEAK NATURE OF THE
   MID-LEVEL IMPULSE WILL MITIGATE THE SVR THREAT. 
   
   GIVEN THE LIMITED SPATIAL EXTENT OF ANY SVR THREAT...THE ISSUANCE OF
   A WW IS UNLIKELY.
   
   ..COHEN.. 05/12/2011
   
   
   ATTN...WFO...RAH...ILM...RNK...RLX...CAE...GSP...MRX...
   
   LAT...LON   37668168 37808043 37527985 37157941 36767922 36057914
               35167939 34447960 33648012 33188079 33408185 34858338
               36418311 37668168