MESOSCALE DISCUSSION 1004

        MESOSCALE DISCUSSION 1004     NWS STORM PREDICTION CENTER NORMAN OK     1203 PM CDT FRI JUN 01 2012          AREAS AFFECTED...NC...VA...WV...MD...DC...PA          CONCERNING...SEVERE POTENTIAL...TORNADO WATCH LIKELY           VALID 011703Z - 011830Z          PROBABILITY OF WATCH ISSUANCE...80 PERCENT          SUMMARY...THUNDERSTORMS WILL INCREASE THROUGH THE AFTERNOON IN A     VERY MOIST AND INCREASINGLY UNSTABLE AIRMASS FROM NC NWD ACROSS     VA...SRN PA...WV PNHDL...AND MD/DC AREA. RECENT TRENDS SUGGEST THAT     ISOLATED STORMS WILL FIRST POSE A THREAT FOR ISOLATED SEVERE WEATHER     IN THE FORM OF HAIL/WIND OVER PARTS OF NERN NC AND SERN VA WHERE     INSTABILITY IS GREATEST BUT SHEAR AND FORCING WILL REMAIN LIMITED     FOR A TIME. ADDITIONAL SEVERE STORMS ARE LIKELY AS A FORCED SQUALL     LINE DEVELOPS EAST OF THE APPALACHIANS LATER THIS AFTERNOON. DEEP     SHEAR AND TORNADO POTENTIAL MAY INCREASE ACROSS THE ENTIRE REGION     FROM LATE AFTERNOON INTO EVENING AND ONE OR MORE TORNADO WATCHES     WILL LIKELY BE ISSUED OVER THE NEXT 1-2 HOURS.          DISCUSSION...STRONG FORCED ASCENT WITH A LARGE SCALE TROUGH WAS     LIKELY RESULTING IN AN INCREASE IN LOW-TOPPED CONVECTION ALONG A     COLD FRONT NOW SITUATED FROM ERN OH SWD ACROSS WV...EXTREME SWRN VA     AND ERN TN. EXPECT THAT THIS CONVECTION WILL CROSS THE SPINE OF THE     APPALACHIANS OVER THE NEXT 2 HOURS. AS THIS FORCING BEGINS TO     INTERACT WITH GREATER INSTABILITY EAST OF THE MOUNTAINS...MORE     VIGOROUS STORM DEVELOPMENT IN THE FORM OF BOWING/LEWPING SEGMENTS     CAN BE EXPECTED. A WEAK FRONTAL WAVE MAY ALSO TAKE FORM WITH TIME     COINCIDENT WITH AN INCREASE IN STORMS ALONG A WARM FRONT EXTENDING     ACROSS SRN PA AND INTO THE DELMARVA REGION. IN ADDITION TO WIND     DAMAGE THREAT WITH STORMS ALONG THE ADVANCING FRONT...AN ENHANCED     BUT FOCUSED TORNADO THREAT MAY EVOLVE NEAR THE FRONTAL WAVE AND WARM     FRONT. ONE TORNADO WATCH WILL LIKELY BE NEEDED FROM SRN PA ACROSS     WRN VA WITHIN THE NEXT HOUR OR SO.          ANOTHER WATCH WILL LIKELY BE NEEDED FROM THE ONGOING STORMS OVER NRN     NC NWD ACROSS THE VA TIDEWATER AREA. STORMS IN THIS AREA ARE     DEVELOPING WITH HEATING OF THE DAY AND PERHAPS THE LARGER SCALE     ASCENT DEVELOPING EAST WITH THE TROUGH. WHILE INSTABILITY IS GREATER     IN THIS CORRIDOR...DEEP SHEAR AND FORCING ARE LIKELY MORE MARGINAL     TO SUPPORT A MORE WIDESPREAD IMMEDIATE THREAT OF SEVERE TSTMS     WIND/TORNADOES. NONETHELESS...SHEAR WILL LIKELY INCREASE     SUFFICIENTLY WITH TIME ACROSS THIS AREA TO WARRANT A TORNADO WATCH     AND THIS WATCH WILL LIKELY BE COORDINATED SHORTLY.          ..CARBIN.. 06/01/2012               ATTN...WFO...PHI...AKQ...MHX...CTP...LWX...RAH...RNK...PBZ...     RLX...