[MCD] SWOMCD

Sun Jan 22 18:36:39 UTC 2006

ACUS11 KWNS 221835
SWOMCD
SPC MCD 221834 
VAZ000-WVZ000-230030-

MESOSCALE DISCUSSION 0077
NWS STORM PREDICTION CENTER NORMAN OK
1234 PM CST SUN JAN 22 2006

AREAS AFFECTED...PORTIONS OF SWRN/WRN VA AND ERN WV

CONCERNING...FREEZING RAIN 

VALID 221834Z - 230030Z

FREEZING RAIN WITH HOURLY RATES OVER 0.05 IN. COULD DEVELOP OVER
PORTIONS OF SWRN VA AND SERN WV...MAINLY THE FOOTHILLS OF THE
CENTRAL APPALACHIANS AND IMMEDIATE VALLEYS...BEGINNING AS EARLY AS
21Z. INCREASING EXPECTATION OF FREEZING RAIN WILL OCCUR BETWEEN
21-00Z AS WET BULB EFFECTS PERSIST AND DIURNAL COOLING EFFECTS
OCCUR. IN ADDITION...THE POTENTIAL FOR AT LEAST LIGHT FREEZING RAIN
MAY SPREAD NWD INTO PORTIONS OF NWRN VA AND THE WV PANHANDLE BY 00Z.
FREEZING RAIN RATES WELL OVER 0.10 IN/HR WILL BE POSSIBLE BY
00Z...GIVEN THE CONVECTIVE NATURE OF PRECIPITATION.

LATEST RADAR DATA SHOWS A BROAD AREA OF MODERATE TO HVY
PRECIPITATION OVER NERN TN AND ERN KY....AIDED BY STRONG LOW-MID
LEVEL WAA /PER MORRISTOWN VWP DATA/. A SLIVER OF ELEVATED CAPE AND
STEEP LAPSE RATES /CENTERED AROUND 500 MB/ WAS SUPPORTING THIS
EMBEDDED THUNDERSTORM ACTIVITY. DOWNSTREAM OF THIS...SFC DATA SHOWS
COLD/DRY AIR WAS DAMMED UP AGAINST THE CENTRAL APPALACHIANS MTNS OF
SERN WV/SWRN VA. RECENT SFC TRENDS SHOW THAT DRY AIR CONTINUES TO
SLOWLY FILTER INTO WRN VA...WITH DEWPTS IN THE TEENS OVER MUCH OF
THE AREA. DESPITE THE VERY DRY AIR IN THE LOW LEVELS..SUFFICIENTLY
STRONG WET-BULB COOLING AFFECTS WITH MODERATE RAIN MOVING INTO THE
AREA SHOULD ALLOW FOR SATURATION TO OCCUR RELATIVELY QUICKLY /1-2
HRS/ WITH THE ONSET OF PRECIPITATION. WITH TEMPERATURES ONLY IN THE
MID 30S TO LOWER 40S...WET-BULB EFFECTS SHOULD ALLOW FOR
TEMPERATURES TO REACH THE SUB-FREEZING MARK OVER MUCH OF THE SRN
SHENANDOAH VALLEY AND FOOTHILLS OF THE CENTRAL APPALACHIANS OF SWRN
VA AND SERN WV BEGINNING AROUND 21Z. THE PRESENCE OF AN ELEVATED
WARM LAYER STARTING JUST UNDER 1 KM...SUGGESTS THAT THE HIGHEST
ELEVATIONS OF THE CENTRAL APPALACHIANS /ABOVE 3000 FT/ SHOULD SEE
ONLY RAINFALL THROUGH THE EVENT.

..CROSBIE.. 01/22/2006

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

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

37618090 38997943 39287911 39387856 39047808 38457810
37667898 37037966 36967999 36928010 37008060 37338090 