MESOSCALE DISCUSSION 0358
   NWS STORM PREDICTION CENTER NORMAN OK
   0113 AM CDT TUE APR 05 2011
   
   AREAS AFFECTED...PORTIONS VA...MD...DC...DE...NWRN NC.
   
   CONCERNING...SEVERE THUNDERSTORM WATCH 99...
   
   VALID 050613Z - 050645Z
   
   THE SEVERE WEATHER THREAT FOR SEVERE THUNDERSTORM WATCH 99
   CONTINUES.
   
   WW IS BEING REPLACED TO COVER INCREASING QLCS-TORNADO AND EMBEDDED
   SUPERCELL THREAT...ESPECIALLY INVOF BOUNDARY DESCRIBED BELOW...AND
   ALSO DAMAGING WIND THREAT EXTENDING AS FAR AS ATLANTIC COAST OF
   DELMARVA REGION AND VA TIDEWATER BY ABOUT 13Z.  PERSISTENT/SVR BAND
   OF TSTMS OVER WRN PORTIONS NC/VA WILL CONTINUE MOVING EWD THROUGH WW
   AREA...AND SHOULD CLEAR WW BY ABOUT 830Z.  NEW WW MAY BE CLEARED
   BEHIND THIS LINE.
   
   SFC MESOANALYSIS SHOWS OUTFLOW BOUNDARY FROM EARLIER CONVECTION FROM
   NEAR DCA ARCHING SWWD ACROSS FVX...THEN WSWWD ACROSS SRN TIER OF VA
   COUNTIES...INTERSECTING QLCS INVOF NC/VA BORDER W MTV.  STG SFC
   PRESSURE FALLS WERE ANALYZED NEAR THAT INTERSECTION...INDICATING
   POSSIBLE MESOLOW DEVELOPMENT IN ADDITION TO FALLS ASSOCIATED WITH
   WAA/AIR MASS RECOVERY FROM EARLIER COLD POOL IMMEDIATELY TO ITS E. 
   LOW-LEVEL VORTICITY WILL BE MAXIMIZED ALONG AND JUST N OF OUTFLOW
   BOUNDARY...AS WILL HODOGRAPH SIZE AND SRH...INDICATING ENHANCED
   POTENTIAL FOR LOW-MIDDLE LEVEL/STORM-SCALE ROTATION AND RELATIVELY
   MAXIMIZED TORNADO PROBABILITIES.  EMBEDDED/SMALL-SCALE VORTICES ALSO
   MAY DEVELOP IN OTHER SEGMENTS OF THIS LINE.  INFLOW-LAYER
   INSTABILITY WILL REMAIN MRGL BUT SUFFICIENT...AND WILL INCREASE
   ACROSS PORTIONS CENTRAL/ERN VA INTO DELMARVA REGION.  LOW-LEVEL
   THETAE ADVECTION WILL INCREASE MLCAPE TO 100-500 J/KG RANGE AS DEW
   POINTS RISE THROUGH 50S...WITH LOW-MID 60S OVER PORTIONS SRN VA. 
   THIS PROCESS ALSO SHOULD ACT TO REDUCE CINH...ESPECIALLY FOR
   STRONGLY FORCED PARCELS ALONG LEADING EDGE OF LINE.
   
   ..EDWARDS.. 04/05/2011
   
   
   ATTN...WFO...PHI...AKQ...LWX...RAH...RNK...
   
   LAT...LON   36588090 37767965 39357720 39487568 38347506 37117587
               36537587 36507934 36127998 36098094 36588090