MESOSCALE DISCUSSION 0248
   NWS STORM PREDICTION CENTER NORMAN OK
   0952 PM CST TUE MAR 05 2013
   
   AREAS AFFECTED...ERN WV...PORTIONS OF NRN/WRN VA...A LARGE PART OF
   MD...WASHINGTON DC...PORTIONS OF FAR SRN PA
   
   CONCERNING...HEAVY SNOW 
   
   VALID 060352Z - 060945Z
   
   SUMMARY...SNOW WITH RATES OF 1-1.5 IN/HR WILL SPREAD NEWD ACROSS
   PARTS OF THE MID ATLANTIC AND CNTRL APPALACHIANS OVERNIGHT.
   
   DISCUSSION...AS THE LEADING EDGE OF A STRONG MID-LEVEL PV MAX
   CONTINUES OVERTAKING A LOW-LEVEL BAROCLINIC ZONE OVER THE
   CAROLINAS...A SFC LOW IS DEVELOPING ALONG THE ATTENDANT FRONT IN
   CNTRL NC WHERE PRESSURE FALLS OF 3-4 MB PER 2 HOURS HAVE BEEN NOTED.
   AS THE SFC LOW TRACKS NEWD/NWD DURING THE NEXT SEVERAL HOURS...A
   STRENGTHENING 850-700-MB FRONTOGENETIC CIRCULATION WILL SUPPORT
   INCREASING MESOSCALE ASCENT. IN TURN...PRECIPITATION WILL CONTINUE
   TO OVERSPREAD THE AREA TONIGHT AMID AN ELEVATED WARM CONVEYOR BELT.
   
   WHILE LOW-LEVEL THERMAL PROFILES ARE INITIALLY MARGINAL FOR SNOW
   FROM THE DC AREA INTO NRN VA...THE COMBINED EFFECTS OF COOLING OWING
   TO FORCED ASCENT AND WET-BULB/NOCTURNAL EFFECTS SHOULD AID IN
   LOWERING WET-BULB ZERO HEIGHTS TOWARD THE SFC DURING THE NEXT FEW
   HOURS. FURTHERMORE...ISALLOBARIC FORCING SHOULD ALLOW LOW-LEVEL FLOW
   BACK AND BECOME MORE NLY...RESULTING IN COOLER AIR BEING DRAWN INTO
   THE REGION. AS SUCH...SNOW WILL BECOME THE PREDOMINANT PRECIPITATION
   TYPE ACROSS THE AREA BY 06Z...WITH SNOW RATES INCREASING TO 1-1.5
   IN/HR THEREAFTER. LOCALLY HIGHER RATES MAY OCCUR IN UPSLOPE-FAVORED
   AREAS AND RIDGETOPS OVER THE CNTRL APPALACHIANS. THESE RATES WILL
   LIKELY SPREAD NEWD WITH TIME...ROUGHLY IN TANDEM WITH THE TRACK OF
   THE LOW...REACHING THE DC AREA MORE LIKELY AFTER 08Z. THESE RATES
   WILL LIKELY CONTINUE THROUGH DAWN.
   
   ..COHEN.. 03/06/2013
   
   
   ATTN...WFO...AKQ...CTP...LWX...RNK...PBZ...RLX...
   
   LAT...LON   38907692 38177802 37528005 37918080 38848042 39757915
               39767774 39437690 38907692