SWOMCD
SPC MCD 190022
MDZ000-VAZ000-DCZ000-WVZ000-NCZ000-TNZ000-KYZ000-190515-
MESOSCALE DISCUSSION 2258
NWS STORM PREDICTION CENTER NORMAN OK
0622 PM CST FRI DEC 18 2009
AREAS AFFECTED...PORTIONS OF THE CNTRL/SRN APPALACHIANS AND LOWER
MID-ATLANTIC
CONCERNING...HEAVY SNOW
VALID 190022Z - 190515Z
HEAVY SNOW WITH RATES OF 1 TO 2 IN/HR WILL GRADUALLY TRANSLATE
E/NEWD THROUGH 06Z...TOWARDS THE I-95 CORRIDOR FROM THE WASHINGTON
D.C. TO RICHMOND METRO AREAS. LOCALIZED CONVECTIVE BURSTS MAY YIELD
RATES UP TO 3 IN/HR. A NARROW TRANSITIONAL CORRIDOR OF SLEET TO
FREEZING RAIN MAY DEVELOP ACROSS PORTIONS OF THE PIEDMONT IN WRN NC
TO S-CNTRL VA.
AS OF 0015Z...A BROAD SWATH OF MODERATE TO HEAVY SNOW PERSISTED FROM
PORTIONS OF THE CNTRL/SRN APPALACHIANS INTO THE PIEDMONT OF WRN NC
AND CNTRL/SRN VA. MULTIPLE HOURS OF SNOWFALL RATES FROM 1 TO 2 IN/HR
HAVE BEEN REPORTED SINCE 21Z ACROSS FAR ERN TN/KY...WRN NC AND SWRN
VA. LATEST MODEL FORECASTS ARE CONSISTENT WITH WEAKENING THE LEAD
SHORT WAVE TROUGH...WHICH EXTENDED FROM ERN TN/KY SWD INTO GA PER
WATER VAPOR IMAGERY. NEVERTHELESS...UPSTREAM SHORT WAVE TROUGH OVER
THE MID-MS VALLEY AND ASSOCIATED MID-LEVEL JET ARE EXPECTED TO
AMPLIFY AS THEY EJECT EWD ACROSS THE TN VALLEY. THIS WILL MAINTAIN
GRADUAL DEEPENING OF SURFACE CYCLONE ALONG COASTAL SC THROUGH 06Z.
STRONG LOW-LEVEL WAA...INFERRED BY LARGE VEERED HODOGRAPHS IN
REGIONAL VWP DATA...SHOULD CONTINUE AS 18Z NAM/21Z RUC FORECASTS
DEPICT INTENSE LOW/MID-LEVEL ISENTROPIC/FRONTOGENETICAL ASCENT
GRADUALLY PIVOTING EWD TO THE N/NW OF THE SURFACE LOW TRACK. THIS
WILL SUPPORT SNOWFALL RATES OF 1 TO 2 IN/HR PERSISTING...WHILE THE
STRENGTH OF THE WAA MAY RESULT IN A NARROW CORRIDOR OF SLEET TO
FREEZING RAIN ACROSS PORTIONS OF WRN NC INTO S-CNTRL VA.
..GRAMS.. 12/19/2009
...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...AKQ...LWX...RAH...RNK...PBZ...RLX...GSP...MRX...
JKL...
LAT...LON 38538173 38038263 37288338 36518351 36268282 36228199
35808150 35768061 35917987 36147945 36877738 37467624
38297615 39027688 39257777 39107915 38858058 38538173
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