MESOSCALE DISCUSSION 0249
   NWS STORM PREDICTION CENTER NORMAN OK
   0225 AM CST WED MAR 06 2013
   
   AREAS AFFECTED...PORTIONS OF WV-VA-MD
   
   CONCERNING...HEAVY SNOW 
   
   VALID 060825Z - 061230Z
   
   SUMMARY...SNOWFALL RATES APPROACHING 1 INCH AN HOUR WILL BE COMMON
   ACROSS PORTIONS OF MD SWWD INTO NRN VA AND ERN WV.  LOCALIZED HIGHER
   RATES /1 TO 1.5 INCH PER HOUR/ WILL PREFERENTIALLY FAVOR AND
   INTERMITTENTLY OCCUR ALONG THE E-FACING SLOPES OF THE HIGHEST
   TERRAIN IN ADJACENT PORTIONS OF WV-MD-VA.
   
   DISCUSSION...THE LAST FEW HOURS OF WATER VAPOR IMAGERY HAVE SHOWN
   THE NEWD PROGRESSION OF A MID-LEVEL DRYSLOT IMPINGING ON SRN-CNTRL
   VA AS A MID LEVEL LOW MIGRATES EWD FROM ERN KY/TN AND STRADDLES THE
   VA/NC BORDER BY 12Z.  CONSIDERABLE MODEL VARIABILITY EXISTS BETWEEN
   THE 00Z AND 06Z NAM...00Z GFS...AND 00Z ECMWF REGARDING THE MID
   LEVEL DRYSLOT EVOLUTION FOR THE I-95 CORRIDOR NEAR THE D.C. -
   BALTIMORE VICINITY.  THE NAM APPEARS MOST AGGRESSIVE AND SEEMINGLY
   PROBABLE IN MID LEVEL DRYING OVER THIS REGION WHEN COMPARED TO LOOPS
   OF RADAR MOSAIC REFLECTIVITY.  00Z NAM FORECAST SOUNDINGS SHOW THE
   DRIER MID-LEVEL AIR OVERSPREADING PORTIONS OF THE D.C. AND BALTIMORE
   I-95 CORRIDOR BY 09-10Z AND 10-11Z...RESPECTIVELY.  THIS SHOULD
   COINCIDE WITH AN ABATEMENT IN THE HEAVIEST SNOWFALL RATES AS THE
   DEEP SATURATED COLUMN JUXTAPOSED WITH DEEP LAYER FORCING FOR ASCENT
   BECOMES RELEGATED FARTHER W OVER NRN VA...NERN WV...AND WRN MD. 
   THIS WILL OCCUR IN TANDEM WITH AN INTENSIFYING SURFACE LOW
   /CURRENTLY ANALYZED OVER NERN NC/ DEVELOPING NEWD TO THE TIDEWATER
   VICINITY BY 12-15Z.  UPSLOPE COMPONENT TO THE FLOW OWING TO
   INCREASING ELY FLOW IN THE H9-H85 LAYER AROUND 40 KTS WILL ACT TO
   AUGMENT SNOWFALL RATES OVER THE ERN FACING SLOPES OF THE HIGHER
   TERRAIN OVER PARTS OF WV-MD-VA /RATES 1 TO 1.5 INCH PER HOUR/.
   
   ..SMITH.. 03/06/2013
   
   
   ATTN...WFO...CTP...LWX...RNK...PBZ...RLX...
   
   LAT...LON   38377999 39197931 39597905 39777752 39467654 38997656
               38507742 38057896 37937979 38377999