MESOSCALE DISCUSSION 0158
   NWS STORM PREDICTION CENTER NORMAN OK
   0540 PM CST TUE FEB 13 2007
   
   AREAS AFFECTED...MD/NRN AND CNTRL VA/E WV PANHANDLE
   
   CONCERNING...WINTER MIXED PRECIPITATION 
   
   VALID 132340Z - 140445Z
   
   ...WINTRY MIXED PRECIPITATION WILL CHANGE OVER TO MOSTLY FREEZING
   RAIN THIS EVENING WITH SIGNIFICANT ICING POSSIBLE THROUGH THE
   OVERNIGHT HOURS...
   
   LATEST SFC ANALYSIS SHOWS WEDGE OF COLD AIR FIRMLY IN PLACE JUST
   EAST OF THE APPALACHIANS. MAIN SFC LOW IS NOW ACROSS WRN KY WITH
   SECONDARY LOW BEGINNING TO DEVELOP NEAR THE SC/GA BORDER. STRONG SFC
   PRESSURE FALLS ARE OBSERVED FROM NRN GA ALONG THE ATLANTIC
   SEABOARD...AND THIS IS HELPING TO KEEP THE SFC WINDS FROM THE N/NE
   ACROSS MD AND VA WHICH IS REINFORCING THE COLD AIR. 
   
   THUS FAR...PRECIPITATION HAS BEEN CONVECTIVE IN NATURE...FORMING IN
   A BROAD AREA OF ISENTROPIC LIFT AHEAD OF MAIN UPPER TROUGH
   APPROACHING FROM IL/IND. AS SYNOPTIC LIFT INCREASES...MORE STEADY
   PRECIPITATION IS EXPECTED. 18Z SOUNDING FROM RNK SHOWED SIGNIFICANT
   WARM LAYER AROUND 5C AT 850MB...WHILE 18Z SOUNDING FROM IAD WAS A
   LITTLE COOLER. HOWEVER...RECENT SFC OBSERVATIONS FROM THE
   DC/BALTIMORE METRO AREA INDICATE PRECIPITATION HAS BEEN MAINLY
   FZRA/SLEET THIS AFTN WITH MOSTLY FZRA ACROSS NRN AND CNTRL VA. WITH
   WARM ADVECTION CONTINUING THIS EVENING AND OVERNIGHT...FREEZING RAIN
   WILL BECOME THE DOMINANT PRECIPITATION TYPE. SIGNIFICANT ICING COULD
   OCCUR GIVEN A PROLONGED PERIOD OF FREEZING RAIN EXTENDING INTO THE
   OVERNIGHT.
   
   ..TAYLOR.. 02/13/2007
   
   
   ATTN...WFO...PHI...AKQ...CTP...LWX...RNK...
   
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