[MCD] SWOMCD

Sun Jan 21 16:45:50 UTC 2007

ACUS11 KWNS 211650
SWOMCD
SPC MCD 211650 
VAZ000-WVZ000-NCZ000-212115-

MESOSCALE DISCUSSION 0093
NWS STORM PREDICTION CENTER NORMAN OK
1050 AM CST SUN JAN 21 2007

AREAS AFFECTED...EASTERN WV/WESTERN VA AND NORTHERN PART OF WESTERN
NC

CONCERNING...WINTER MIXED PRECIPITATION 

VALID 211650Z - 212115Z

A MIX OF FREEZING RAIN AND SOME SLEET IS EXPECTED TO BECOME
PREDOMINANT THROUGH THE AFTERNOON ACROSS EASTERN WV/NORTHWEST NC
INTO MUCH OF WESTERN VA...INCLUDING THE I-81 CORRIDOR AND THE
BLACKSBURG/ROANOKE/LYNCHBURG AREAS...AS WELL AS I-64 FROM SOUTHEAST
WV THROUGH THE STAUNTON/WAYNESBORO VA AREAS. ICE ACCUMULATIONS ARE
LIKELY VIA LIQUID EQUIVALENTS OF 0.05-0.10 IN/HR.

WHILE THE 12Z OBSERVED RAOB FROM ROANOKE VA EXHIBITED AN ENTIRELY
SUB-FREEZING RELATIVE WARM LAYER ALOFT /700-850 MB 1-2 DEG C BELOW
ZERO/...A PRONOUNCED WARM ADVECTION REGIME IS QUICKLY MODIFYING THE
ELEVATED THERMODYNAMIC PROFILE. OVER THE PAST COUPLE OF
HOURS...OBSERVATIONS OF FREEZING RAIN HAVE BECOME MORE COMMON FROM
SOUTHERN WV TO THE ROANOKE VA VICINITY...WITH LIGHT FREEZING RAIN
JUST REPORTED /16Z/ AS FAR EAST AS THE LYNCHBURG VA AREA.

WITH A SUB-FREEZING BOUNDARY LAYER LOCKED IN PLACE IN THE LOWEST 1
KM ALONG/EAST OF THE APPALACHIANS /REFERENCE 12Z ROANOKE RAOB/...AND
PARTIAL/FULL MELTING ALOFT BECOMING MORE LIKELY...FREEZING
RAIN/SLEET SHOULD BECOME PREDOMINANT FROM EASTERN WV/NORTHWEST NC
INTO MUCH OF WESTERN VA THROUGH THE AFTERNOON. THIS IS ALSO
SUPPORTED BY 09Z SREF PROBABILISTIC PRECIP-TYPE GUIDANCE. REGARDING
THE ELEVATED WARM LAYER...COMPARISONS BETWEEN REGIONAL OBSERVED 12Z
RAOBS AND 12Z NAM/12Z GFS GUIDANCE SUGGESTS THE SHORT TERM MODEL
DEPICTIONS MAY BE SLIGHTLY TOO COOL...PERHAPS SUGGESTIVE OF A
RELATIVELY QUICKER CHANGE-OVER TO FREEZING RAIN THROUGH EARLY/MID
AFTERNOON VIA THE WARMER TEMPERATURES ALOFT.

..GUYER.. 01/21/2007

...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...RNK...RLX...

38677952 38427856 37777820 37307828 36747898 36288009
36378131 37668135 38488027 