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fxus61 krnk 030130 
afdrnk 


Area forecast discussion 
National Weather Service Blacksburg Virginia 
830 PM EST Tuesday Dec 2 2008 


Synopsis... 
high pressure will build south of the area overnight before 
passing off the coast on Wednesday. A strong cold front will then 
move through the area on Thursday. 
&& 


Near term /through Wednesday/... 
skies finally clearing this evening as ridge axis builds in from 
the west and upper trough departs. This should allow for good 
radiational cooling espcly across the snow covered valleys where 
dewpoints low enough to support lows in the teens. However without 
the high directly overhead appears the ridges may stay mixed a bit 
and could see readings steady or rise some late given 850 mb 
warming overnight. Thus tweaked temperatures up a little at 
elevation...otherwise clear/cold overnight with most lows in the 20s 
across the County Warning Area. 


Wednesday will be a sunny day as surface high exits off the coast by afternoon. 
Winds will be calm in the morning but as the high moves away and 
the cold front approaches from the west...gradient winds from the 
southwest could become gusty during the afternoon in the west. 


&& 


Short term /Wednesday night through Friday night/... 
Wednesday night...a cold front will be entering the Ohio Valley with 
strong jet dynamics remaining in the Ohio-tenn valley. Warm air 
advection will be crossing the area overnight ahead of the front. 
There is still some influence of high pressure over the area even 
though the parent high is off the southeast coast. Valleys and areas east 
will likely see winds decouple while warm air is working in aloft. 
This will promote valley temperatures to be about 10f cooler than 
the ridge. 


Early Thursday morning...prefrontal rain showers will enter 
southeast West Virginia and remain over the mountains through 
Thursday middle morning. Prefrontal showers likely to stall over the 
mountains in the morning as flow is parallel to the Appalachians. 
850 mb temperatures are warm enough to keep initial precipitation as 
all rain. As the front sweeps across the region...rain showers will 
dissipate moving east as flow becomes westerly by middle morning. There 
is still deep enough southwesterly flow and jet dynamics in the east 
to at least keep chance probability of precipitation in the forecast Thursday morning. The 
cold air will surge into the area Thursday morning and we may see 
mountain showers converting over to snow showers by the 
afternoon...however the moisture will be limited. 24 hour maximum 
mountain temperatures to occur during the pre-dawn hours with 
temperatures remaining steady or falling during the day. Eastern 
temperatures may see their maximums prior to noon with temperatures 
remaining steady in the afternoon. I will try to reflect this trend 
in the grids and hourly weather web graphs. 


Their is some brief northwesterly flow during Thursday 
afternoon/evening to keep snow showers on western slopes. 
However...flow becomes westerly and trajectories off the lakes do 
not favor a prolong upslope event. By midnight Friday...high 
pressure edging into the region and any left over snow showers will 
be gone by sunrise. 12z GFS hinting at a middle level wave streaking 
into the area on Friday. This system does not have much moisture to 
work with. If any snow showers develop...it will be across the 
Greenbrier valley and Alleghany Highlands. 


Temperatures are expected to be the warmest prior to the front on 
Thursday...then fall below normal through the remainder of the week. 


&& 


Long term /Saturday through Tuesday/... 
fast moving clipper system slips through the area during the 
weekend with limited precipitation...mainly over the west. This will be 
followed by another cool shot as high pressure drops south into 
the Midwest. This high will move east overhead Monday with 
moderating temperatures under a zonal flow aloft. Next system poised to 
bring a chance of wintry precipitation to the area Tuesday. 


&& 


Aviation /01z Wednesday through Sunday/... 
look for clouds to scour out of the area through 03z...with VFR 
conditions at all taf sites. Winds will come around to the south 
Wednesday afternoon once the surface high slides east. Look for a few 
gusts being possible along the ridges and even the Piedmont around 
15-20 knots. Left out of taf for now...in case high slows down. 


Strong cold front will move through the region Thursday morning 
into early afternoon. This will likely bring poor flight 
conditions to blf and lwb late Wednesday night and Thursday. 
Further east...there is a lower chance of poor flight conditions. 
Much colder air coming in behind this front will result in upslope 
-shsn for southeast West Virginia Thursday night. VFR should 
return Friday into Saturday as high pressure builds in from the 
west and most moisture lifts back to the north. 


&& 


Rnk watches/warnings/advisories... 
Virginia...none. 
NC...none. 
WV...none. 


&& 


$$ 
Synopsis...jh/jj 
near term...jh/js 
short term...rcs 
long term...wp 
aviation...js/wp