MESOSCALE DISCUSSION 0208
   NWS STORM PREDICTION CENTER NORMAN OK
   0609 AM CST SUN FEB 25 2007
   
   AREAS AFFECTED...NRN VA...WV PNHDL...NRN MD...SRN PA
   
   CONCERNING...HEAVY SNOW 
   
   VALID 251209Z - 251615Z
   
   MDT TO LOCALLY HVY SNOW COULD DEVELOP EWD FROM THE WV PNHDL ACROSS
   PARTS OF THE NRN VA/MD...AND SRN PA OVER THE NEXT FEW HOURS. SNOW
   MAY OCCASIONALLY MIX WITH RAIN/ICE PELLETS WHICH WOULD PROBABLY KEEP
   ACCUMULATION RATES BELOW 1 INCH PER HOUR IN MOST AREAS.
   
   STRONG MOISTURE FLUX AND ISENTROPIC LIFT WITHIN ERN QUADRANT OF
   LARGE SCALE DEEP-LAYER CYCLONE CENTERED OVER THE UPPER MIDWEST WILL
   CONTRIBUTE TO A BAND OF SNOW DEVELOPING ACROSS THE REGION THIS
   MORNING. LATEST SHORT-TERM GUIDANCE...IN ADDITION TO RECENT ACARS
   SOUNDING OUT OF DCA...SUGGEST THAT THERMODYNAMIC PROFILES ACROSS THE
   AREA WILL SUPPORT THE DEVELOPMENT OF A RELATIVELY DEEP NEAR 0C
   ISOTHERMAL LAYER AS AIR MASS BECOMES SATURATED THROUGH LIFT AND
   FURTHER MOISTENING. HIGHLY AMPLIFIED FLOW BETWEEN THE MIDWEST
   CYCLONE AND SHARP RIDGE ACROSS THE ERN GREAT LAKES AND MID ATLANTIC
   WAS ALSO RESULTING IN A ZONE OF ENHANCED ASCENT DUE TO MID LEVEL
   FRONTOGENESIS AND LARGE SCALE JET COUPLING. 
   
   SREF...NAM-WRF...WRF-NMM...AND RECENT RUC...ALL DEPICT AN AREA OF
   INCREASING UPWARD MOTION AND QPF TRANSITIONING ACROSS ERN WV...NRN
   VA/MD AND SRN PA THOUGH THE MORNING. WHILE SOME PRECIPITATION-TYPE
   GUIDANCE SUGGESTS SNOW MAY MIX WITH ICE PELLETS AND/OR RAIN/FREEZING
   RAIN...STRONGER MESOSCALE FORCING FOR ASCENT AND DIABATIC
   PROCESSES...MAY OFFSET WARM ADVECTION SUFFICIENTLY TO SUPPORT
   LOCALLY HEAVY SNOW FOR AT LEAST 1-2 HOURS AT ANY ONE LOCATION.
   
   ..CARBIN.. 02/25/2007
   
   
   ATTN...WFO...CTP...LWX...PBZ...
   
   39657681 39287684 39097737 39117787 39387859 39557887
   39837922 40337913 40307821 39917715