MESOSCALE DISCUSSION 0541
   NWS STORM PREDICTION CENTER NORMAN OK
   0615 PM CDT MON APR 20 2009
   
   AREAS AFFECTED...NERN NC THROUGH ERN VA
   
   CONCERNING...TORNADO WATCH 178...
   
   VALID 202315Z - 210045Z
   
   THE SEVERE WEATHER THREAT FOR TORNADO WATCH 178 CONTINUES.
   
   THE THREAT FOR ISOLATED LARGE HAIL...DAMAGING WIND AND ISOLATED
   TORNADOES WILL PERSIST NEXT COUPLE HOURS ACROSS ERN TWO THIRDS OF WW
   178 INCLUDING ERN VA AND A SMALL PART OF NERN NC.
   
   EARLY THIS EVENING A PRE-FRONTAL CONVERGENCE BOUNDARY EXTENDS FROM
   CNTRL VA WHERE IT INTERSECTS AN E-W ORIENTED WARM FRONT THEN SWD
   THROUGH E CNTRL NC AND ERN SC. THIS BOUNDARY WILL CONTINUE MOVING
   EAST. PRIMARY SEVERE THREAT WILL REMAIN ALONG AND EAST OF THE
   PRE-FRONTAL TROUGH WHERE 500-1000 J/KG MLCAPE EXISTS IN THE MOIST
   WARM SECTOR...AND WHERE THE SLY LOW LEVEL JET IS MAINTAINING
   SUFFICIENT 0-1 KM HODOGRAPHS FOR A THREAT OF SUPERCELLS WITH LOW
   LEVEL MESOCYCLONES. ANY TORNADO THREAT COULD BE LOCALLY ENHANCED
   ACROSS E-CNTRL VA AS STORMS CROSS THE WARM FRONT. STORMS HAVE SHOWN
   AN OVERALL WEAKENING TREND DURING THE LAST HOUR AS THE BOUNDARY
   LAYER BEGINS TO COOL. SEVERE THREAT WILL CONTINUE UNTIL AROUND
   02Z...AFTER WHICH THE LOW LEVEL JET WILL BEGIN TO MOVE OFFSHORE AS
   THE SHORTWAVE TROUGH ADVANCES FARTHER EAST. 
   
   FARTHER WEST OVER WRN VA...ANY SEVERE THREAT ASSOCIATED WITH
   CONVECTION DEVELOPING ALONG COLD FRONT SHOULD REMAIN LIMITED WHERE
   THE LOW LEVEL FLOW HAS VEERED RESULTING IN A DRYING OUT OF THE
   BOUNDARY LAYER IN IMMEDIATE PRE-FRONTAL ZONE.
   
   ..DIAL.. 04/20/2009
   
   
   ATTN...WFO...AKQ...LWX...RAH...
   
   LAT...LON   36487628 36167727 36057804 36387834 37147821 37967801
               38497714 38197605 36487628