MESOSCALE DISCUSSION 0107
   NWS STORM PREDICTION CENTER NORMAN OK
   0914 PM CST WED FEB 11 2009
   
   AREAS AFFECTED...SERN PA...SRN NJ...DE...MD...NE VA
   
   CONCERNING...SEVERE THUNDERSTORM WATCH 21...
   
   VALID 120314Z - 120415Z
   
   THE SEVERE WEATHER THREAT FOR SEVERE THUNDERSTORM WATCH 21
   CONTINUES.
   
   THE WIND DAMAGE THREAT WITH A FINE CONVECTIVE LINE OVER CNTRL
   PA...WRN MD AND NRN VA IS EXPECTED TO BECOME INCREASINGLY MARGINAL
   OVER THE NEXT FEW HOURS. WW ISSUANCE EAST OF WW 21 IS NOT EXPECTED.
   
   WATER VAPOR IMAGERY CONTINUES TO SHOW A WELL-DEVELOPED DRY SLOT
   EXTENDING NEWD INTO THE MID-ATLANTIC WITH THE RUC ANALYZING A VERY
   STRONG BAND OF LARGE-SCALE ASCENT ALONG THE LEADING EDGE. IN SPITE
   OF ALMOST NO INSTABILITY...THE STRONG FORCING AND VERTICAL SHEAR IS
   SUPPORTING THE WIND DAMAGE THREAT WITH A CONVECTIVE LINE CURRENTLY
   MOVING THROUGH THE WRN PART OF WW 21. THE FORWARD SPEED OF THE LINE
   IS ABOUT 50 KT AND SHOULD REACH THE ERN PART OF THE WW BY 0500 TO
   0530Z. ALTHOUGH A WIND DAMAGE THREAT MAY CONTINUE...THE THREAT
   SHOULD BECOME INCREASINGLY MARGINAL AS THE LINE MOVES FURTHER AWAY
   FROM THE GREAT LAKES UPPER-LEVEL TROUGH. IN ADDITION...DROPPING SFC
   TEMPS WILL ALSO CONTRIBUTE TO A LESS FAVORABLE ENVIRONMENT.
   
   ..BROYLES.. 02/12/2009
   
   
   ATTN...WFO...PHI...AKQ...CTP...LWX...
   
   LAT...LON   37987650 37957726 38057777 38507802 39177768 40017747
               40197743 40427720 40607687 40587615 40517535 40397477
               40187446 39637429 38697514 38227579 37987650