MESO: Mesoscale Discussion 2201

ACUS11 KWNS 241534
SWOMCD
SPC MCD 241534
MDZ000-WVZ000-VAZ000-PAZ000-OHZ000-241800-

MESOSCALE DISCUSSION 2201
NWS STORM PREDICTION CENTER NORMAN OK
0934 AM CST MON DEC 24 2012

AREAS AFFECTED...E-CNTRL/SERN OH...NRN WV...WRN PART OF THE MD
PANHANDLE...SWRN PA...FAR WRN VA

CONCERNING...WINTER MIXED PRECIPITATION

VALID 241534Z - 241800Z

SUMMARY...AREAS OF FREEZING RAIN WITH RATES APPROACHING 0.05 INCH
PER 3 HOURS...AS WELL AS SLEET AND POSSIBLY LIGHT SNOW...WILL SHIFT
NEWD THROUGH 17Z-18Z.

DISCUSSION...UPPER AIR ANALYSIS SUGGESTS AN ONGOING WARM ADVECTION
REGIME FROM THE UPPER OH VALLEY EWD ACROSS THE CNTRL APPALACHIANS IN
ASSOCIATION WITH A LOWER TROPOSPHERIC WAVE PROGRESSING ENEWD/NEWD
ACROSS THE AREA. WHILE RADAR DATA DEPICT LIGHT PRECIPITATION ECHOES
ALOFT...SFC TEMPERATURE-DEWPOINT SPREADS OF 3-5F SUGGEST THAT
SUB-CLOUD EVAPORATION/SUBLIMATION PROCESSES ARE PREVENTING THIS
PRECIPITATION FROM REACHING THE GROUND IN MANY LOCATIONS.
HOWEVER...DOWNWARD COLUMNAR MOISTENING WILL CONTINUE THROUGH LATE
MORNING IN ASSOCIATION WITH CONTINUED PRECIPITATION ALOFT AS WARM
ADVECTION PERSISTS. THIS WILL INCREASE THE POTENTIAL FOR
PRECIPITATION TO REACH THE SFC THROUGH LATE MORNING.
PARTIAL/COMPLETE MELTING WILL OCCUR AS HYDROMETEORS FALL THROUGH AN
ELEVATED WARM LAYER FEATURING TEMPERATURES OF AROUND 1-4C -- NOTED
BETWEEN 920 MB AND 850 MB PER PITTSBURGH PA/WILMINGTON OH 12Z RAOBS.
FOR AREAS WHERE SFC TEMPERATURES REMAIN BELOW FREEZING...ESPECIALLY
OVER SHELTERED VALLEYS...FREEZING RAIN AND SLEET...AND PERHAPS LIGHT
SNOW...WILL BE POSSIBLE. FREEZING RAIN RATES APPROACHING 0.05 INCH
PER 3 HOURS MAY ENSUE THROUGH 17Z-18Z. THEREAFTER...SFC-LAYER WARM
ADVECTION COMBINED WITH DIURNAL HEATING SHOULD SUPPORT PREDOMINANTLY
RAIN.

..COHEN.. 12/24/2012

...PLEASE SEE WWW.SPC.NOAA.GOV FOR GRAPHIC PRODUCT...

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

LAT...LON 40057969 39707877 39237866 38727903 37777989 37758042
38448016 38728040 38908139 39148198 40018173 40198085
40057969

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