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Mesoscale Discussion 32
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   MESOSCALE DISCUSSION 0032
   NWS STORM PREDICTION CENTER NORMAN OK
   0750 PM CST SUN JAN 11 2015

   AREAS AFFECTED...PORTIONS OF WV...CNTRL/NRN VA...WRN MD...AND FAR
   SRN PA

   CONCERNING...FREEZING RAIN 

   VALID 120150Z - 120745Z

   SUMMARY...LIGHT RAIN WILL TRANSITION TO FREEZING RAIN ACROSS THE
   DISCUSSION AREA THROUGH 03Z...AND SHOULD CONTINUE THROUGH EARLY
   MONDAY MORNING. PRECIPITATION RATES MAY APPROACH .02 IN/HR.

   DISCUSSION...CURRENT SFC OBS AS OF 01Z SHOW VERY DRY AIR REMAINS IN
   PLACE ACROSS MUCH OF WV...CNTRL/NRN VA...WRN MD...AND FAR SRN PA.
   00Z SOUNDINGS FROM RNK AND IAD ALSO DEPICT A DRY LAYER OF AIR
   BETWEEN THE SFC AND 850 MB ASSOCIATED WITH A REMNANT SFC HIGH
   PRESSURE/WEDGE NOW RETREATING EWD OFF THE ATLANTIC COAST. A LARGE
   AREA OF LIGHT RAIN OCCURRING ACROSS WV AND CNTRL/NRN VA IS
   ASSOCIATED WITH LARGE-SCALE LIFTING ATTENDANT TO A LOW-AMPLITUDE
   SHORTWAVE TROUGH APPROACHING FROM THE W. THIS PRECIPITATION WILL
   CONTINUE TO MOISTEN THE DRY NEAR-SURFACE LAYER. WITH TEMPERATURES
   GENERALLY IN THE LOW TO MID 30S...AND DEW POINTS IN THE TEENS TO
   LOWER 20S...SFC WET BULB TEMPERATURES ARE...AND SHOULD REMAIN BELOW
   32 DEGREES THROUGH EARLY MONDAY MORNING.

   RECENT REPORTS ACROSS THE DISCUSSION AREA SUGGEST THAT EVEN WITH AIR
   TEMPERATURES STILL ABOVE FREEZING AS OF 01Z...PRECIPITATION IS
   BEGINNING TO FREEZE...WHICH IS LIKELY DUE TO COLD GROUND
   TEMPERATURES. WITH THE LOSS OF DIURNAL HEATING AND AS THE LIGHT RAIN
   CONTINUES OVER THE NEXT FEW HOURS...THE AIR TEMPERATURE SHOULD
   CONTINUE TO COOL TO THE WET BULB TEMPERATURE...WHICH IS BELOW
   FREEZING. FREEZING RAIN ACCUMULATIONS MAY INITIALLY BE LIGHT/SHOWERY
   AS THE RESIDUAL DRY LOW-LEVEL AIR REMAINS IN PLACE. HOWEVER...AS
   ADDITIONAL LOW-LEVEL MOISTURE SPREADS IN FROM THE S/SW AND THE
   COLUMN SATURATES...FREEZING RAIN RATES SHOULD EVENTUALLY
   INCREASE...AND MAY APPROACH .02 IN/HR FOR A FEW HOURS OVERNIGHT.

   ..GLEASON/PETERS.. 01/12/2015


   ATTN...WFO...CTP...LWX...RNK...PBZ...RLX...

   LAT...LON   37787859 37427944 37448080 37538179 38348099 39598065
               39837970 39707699 37787859 

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Page last modified: January 12, 2015
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