MESO: Mesoscale Discussion 2257

ACUS11 KWNS 181833
SWOMCD
SPC MCD 181832
VAZ000-NCZ000-WVZ000-TNZ000-SCZ000-182230-

MESOSCALE DISCUSSION 2257
NWS STORM PREDICTION CENTER NORMAN OK
1232 PM CST FRI DEC 18 2009

AREAS AFFECTED...SMOKEY MTNS / PARTS OF WRN NC AND PIEDMONT / ERN TN
/ SWRN VA / SERN WV

CONCERNING...HEAVY SNOW

VALID 181832Z - 182230Z

HEAVY SNOWFALL RATES AROUND 1 INCH PER HOUR WILL LIKELY COMMENCE
FIRST ACROSS THE HIGHER ELEVATIONS OF THE SRN APPALACHIANS IN THE
18-21Z PERIOD WITH MIXED PRECIPITATION OCCURRING ACROSS WRN PORTIONS
OF THE NC PIEDMONT. THE HEAVY SNOWFALL RATES WILL EXTEND NEWD INTO
SWRN VA AND SERN WV 21-00Z. LOCALIZED RATES AROUND 2 INCHES PER
HOUR WITH POTENTIALLY HEAVIER BURSTS ARE POSSIBLE OVER E FACING
SLOPES IN WRN NC AND PERHAPS SW VA LATE THIS AFTERNOON INTO THE
EVENING HOURS.

EARLY AFTERNOON SURFACE ANALYSIS PLACED A SURFACE WEDGE FRONT FROM
PARTS OF SRN GA NEWD OVER THE ADJACENT SC/NC COASTAL WATERS.
SURFACE TEMPS NEAR 32 DEG F ARE CONFINED MAINLY TO PORTIONS OF WRN
NC AND SWRN VA. WET BULBING COOLING IN AREAS OF STRONG ASCENT WILL
SUPPORT A TRANSITION TO WET SNOW ACROSS ALL AREAS W OF I-85.

RADAR MOSAIC HAS SHOWN A SLUG OF HEAVIER PRECIPITATION MOVING NWD
ACROSS NRN GA THE PAST FEW HOURS WITH MEASURED RAINFALL RATES
0.20-0.30 INCH PER HOUR IN NRN GA AND WRN PART OF UPSTATE SC. AS A
LEAD SHORTWAVE TROUGH LOCATED OVER AL/GA MOVES NEWD TOWARDS THE SRN
APPALACHIANS...STRENGTHENING H8-H6 FRONTOGENESIS AND STRONG
MID-LEVEL UVV/S SPREADING NEWD ACROSS THE REGION WITHIN THE
DENDRITIC GROWTH LAYER IN THE MID-LATE AFTERNOON HOURS. WITH LITTLE
EVIDENCE TO THE CONTRARY...ACCORDING TO RADAR MOSAIC EXTRAPOLATION
AND MODEL CONSENSUS 6 HOURLY QPF...SNOWFALL RATES AOA 1 INCH PER
HOUR ARE LIKELY. RECENTLY DETECTED LIGHTNING OVER WRN NC INDICATES
UPRIGHT CONVECTION EXISTS OVER A SMALL AREA EARLY THIS AFTERNOON.
TOWARDS THIS EVENING...ETAKF/GFS FORECAST SOUNDINGS INDICATE THE
POSSIBILITY FOR MORE WIDESPREAD UPRIGHT CONVECTION OVER THE E FACING
SLOPES IN PARTS OF NWRN NC INTO SWRN VA. THIS MAY SUPPORT LOCALIZED
SNOW BURSTS APPROACHING 3 INCHES PER HOUR NEAR OR AFTER 00Z THIS
EVENING.

..SMITH.. 12/18/2009

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

...NOTICE...
SPC WINTER WEATHER MESOSCALE DISCUSSIONS WILL BE ISSUED ON A
SCHEDULED BASIS FROM DECEMBER 1 THROUGH FEBRUARY 28...FOUR
TIMES A DAY...AROUND 00 UTC...06 UTC...12 UTC...AND 18 UTC
FOR SIGNIFICANT SHORT RANGE WINTER WEATHER EVENTS.

ATTN...WFO...RAH...RNK...RLX...GSP...MRX...

LAT...LON 36317950 35488114 35128242 35008351 35438369 36078300
36528238 37078183 37588138 37968029 37847951 37077910
36317950

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