755 
fxus61 krnk 231217 
afdrnk 


Area forecast discussion 
National Weather Service Blacksburg Virginia 
717 am EST Monday Nov 23 2009 


Synopsis... 
low pressure along the southeast coast will track northeast to off 
the Virginia coast this afternoon and then further east into 
Tuesday. Meanwhile...high pressure will build back into the area 
Tuesday followed by a storm system arriving around Thanksgiving. 


&& 


Near term /through tonight/... 
updating the forecast to lower probability of precipitation in the far west as looks like 
band of rain with shortwave will move quicker to the northeast. 
Will leave in chance of rain and drizzle through the day as clouds 
will hang tough. Low pressure aloft over eastern Kentucky this morning will 
shift northeastward today taking first band of rain with it...as deep 
moisture diminishes aloft...per dry pocket on WV loop coming 
through the Tennessee Valley. However...still looking at likely to 
categorical probability of precipitation through the morning...and early afternoon...with 
rain diminishing from SW to NE by late this aftn/evening. With the 
depth of the moisture diminishing from the top down...precipitation will 
transition to more of a drizzle scenario. The drizzle will persist 
into the overnight...especially over the Blue Ridge and points 
east. The next shortwave entering the middle Mississippi Valley may 
enhance some lift over southeast WV this evening so there could be some 
rain lingering there. 


As for temperatures...today will see not much rise in temperatures. Mainly kept 
highs about 4-8 degrees warmer than current temperatures...with little rise 
along/just east of the Blue Ridge of Virginia. 


Tonight...clouds linger...so lows will be similar and even a couple 
degrees warmer than this mornings. 


&& 


Short term /Tuesday through Thursday night/... 
as a coastal low moves into New England...high pressure will wedge 
back south into the middle Atlantic. With no mechanism to mix out 
low level moisture...clouds will hang tough with drizzle and light rain 
Tuesday night. Based upon wind direction...northwest NC and extreme SW Virginia 
are the favored locations for more widespread drizzle or 
measurable light rain...however low level moisture remains sufficient 
for the slight chance of light rain across the entire County Warning Area. More 
southerly component develops Wednesday...but again clouds 
remaining in place should keep temperatures similar Tuesday/Wednesday in the 50s. 
With low pressure moving into the Great Lakes...a cold front will 
cross Wednesday and Wednesday night...allowing showers to break 
out. Both European model (ecmwf)/GFS are bullish on a closed 500 mb low moving into the 
Ohio Valley...allowing 850 mb -5c temperatures to enter the region by Friday 
morning. Downsloping wind does develop behind the front...so 
limited the highest probability of precipitation to the upslope region of southeast West Virginia 
Thursday/Thursday night. Snow/rain showers may not be able to penetrate 
into the New River valley until the upper low moves to the 
Mason/Dixon line on Friday...if it arrives as deep and cold as 
models suggest. 


&& 


Long term /Friday through Sunday/... 
measurable snow will be possible in the preferred upslope snow 
regions of southeast West Virginia into Friday...coverage of 
precipitation will be about the same...but with warming 
temperatures the precipitation should transition back to scattered 
showers...with a trend towards decreasing coverage late. 


On Friday night...even colder temperatures are expected with 
similar...or even slightly stronger wind gusts...but precipitation 
coverage will be less. Isolated snow showers will be 
possible...primarily over southeast West Virginia...neighboring 
parts of southwest Virginia...and in the mountains of northwest 
North Carolina. 


On Saturday into Saturday night...the pressure gradient will begin 
to weaken so look for slower wind speeds and gusts as compared to 
Thursday night through Friday night. Also...even less moisture will 
result in only isolated rain/snow showers in the mountains. 


By Saturday night...we are expecting a dry forecast with the coldest 
night of the weekend. Middle to upper 20s will be common in the 
mountains...with most areas east of the Blue Ridge around 30 or in 
the lower 30s. 


On Sunday...winds take on a bit more of a southwest component ahead 
of our next approaching cold front. There is a slight chance of some 
showers in the southeast West Virginia mountains in association with 
this approaching front on Sunday. 


&& 


Aviation /12z Monday through Friday/... 
rain will continue through the day...especially from 
Roanoke...east to Dan/lyh. The rain should lighten by midday which 
will bring ceilings down below 1kft. Ceilings will start in the IFR to 
LIFR range at blf/lwb at the start or soon. The light rain/drizzle 
will linger into tonight but end over southeast WV overnight. Looking at 
IFR or less conditions to last through this taf period at all 
sites. Dense fog is expected at lwb after midnight. 


Little change is expected perhaps into Tuesday night before next 
approaching short wave from the west allows surface winds to veer 
around into the southwest...gradually eroding the low level 
moisture and low clouds. Many of the mountain ridges may have 
prolonged LIFR conditions. 


The west slopes of the Appalachians may be the only area to 
experience any MVFR condition the next couple of days. 


Should see overall improvement of flight conditions back into VFR 
by Wednesday...but arrival of strong cold front Thursday into 
Friday will likely bring a return to MVFR conditions in upslope 
areas west of the Blue Ridge...along with an increasing threat of 
some mountain rain or snow showers. Downsloping conditions east of 
the Blue Ridge should help to keep those areas mainly in VFR range 
during the late week period. 


&& 


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


&& 


$$ 
Synopsis...wert/wp 
near term...wp 
short term...km 
long term...ds 
aviation...ams/wp