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fxus61 krnk 081958 
afdrnk 


Area forecast discussion 
National Weather Service Blacksburg Virginia 
258 PM EST Thursday Jan 8 2009 


Synopsis... 
an upper level disturbance will exit our region this evening. High 
pressure builds in behind this feature overnight before sliding to 
the southeast of the area on Friday. Another cold front will 
arrive from the west on Saturday. 


&& 


Near term /until 6 am Friday morning/... 
canceled Winter Weather Advisory in the south because snow 
showers are tapering off to snow flurries. Heaviest accumulating 
snows have ended for our County Warning Area. 


Upper trough axis will slide east crossing the region this afternoon 
allowing cold advection and gusty winds to persist. Middle level wave 
should exit the region this evening into tonight. Flow turns more northwest 
in the wake of the wave. Will allow for some light upslope -shsn 
and snow flurries to persist early as coldest 850 mb pocket settles 
into southeast wva. 


However...high pressure slowly nudges in from the west tonight with 
upslope -shsn finally ending but likely not until very late southeast 
wva. Given pressure gradient still lingering wont see optimal 
radiational cooling despite clearing...but cold enough aloft for 
mainly 20s all locations and a few middle teens deep valleys. 


&& 


Short term /6 am Friday morning through Sunday/... 
surface high pressure moves across the southeast unites states on 
Friday. A warm front crosses the County Warning Area Friday night. 
The the associated low and cold front move through on Saturday 
night. The GFS is faster bringing the system through and the European model (ecmwf) 
is slower by about 12 hours. Consensus is that faster GFS is an 
outlier so will be slowing down the arrival of the precipitation 
until around 12z Saturday. 


Will still include some winter precipitation based on the NAM 
soundings and partial thicknesses. Will continue to highlight threat 
of freezing rain and sleet in the hazardous weather outlook. Will 
also extend upslope snow showers in southeast West Virginia behind 
the system through Sunday. 


&& 


Long term /Sunday night through Thursday/... 
high pressure will exit the region Sunday night while another high 
resides along the Gulf through Tuesday. A relatively dry front will 
pass across the region Monday morning. With the high blocking the 
Gulf...very little precipitation is expected ahead of the front. A narrow 
line of showers may accompany the actual front with scattered 
mountain showers behind it. Thicknesses and forecast soundings 
support snow showers...but with some warm air advecting in aloft...a 
brief period of sleet may occur with the frontal passage. A weak 
high pressure builds over the area Monday afternoon and evening with 
snow showers dissipating. 


Between 06z-18z Tuesday...a clipper is expected to track from the 
Ohio Valley and off the middle Atlantic coast. High pressure should 
still be blocking the Gulf...but enough moistures will transport in 
with warm advection to produce another round of snow showers. The 
track and timing of the clipper generally brings 1-4 inches of snow 
to the mountains with possibly higher amounts across Greenbrier and 
the Alleghany Highlands. Snow is not out of the question south of 
the Virginia border...but amounts will be limited. This clipper exits 
during the afternoon. 


Another disturbance slides into the Ohio Valley Tuesday night. This 
system is tracking father to the north and will have the Gulf open. 
More moisture will be available for this system to work with and it 
will also have more warm air with it. Depending on the timing...a 
wintry mix may accompany the cold front on Wednesday. Once the front 
passes to the east...more cold air will filter into the region. With 
a prolonged northwesterly wind...upslope snow showers may persist 
into Thursday morning. 


The extended period continues to Show Low confidence with 
inconsistency between models and runs. Until some continuity is 
displayed...will keep forecast close to hpcguide and probability of precipitation at a 
chance or less. 


&& 


Aviation /20z Thursday through Tuesday/... 
check airmets and sigmets for turbulence...icing and mountain 
obscurations today. Shortwave will move east across the region 
this afternoon. Scattered MVFR/IFR snow showers and snow flurries will 
continue this afternoon across the southern mountains...as shortwave 
trough moves through the region. Drier air slides in from the 
northwest tonight. At kroa...Crosswinds of 14 to 25 knots are possible 
this afternoon rwy 15/33. 


Winds will remain gusty this afternoon especially in the vicinity of 
snow showers. Speeds will gradually decrease this evening into the 
overnight. 


Another cold front comes through Saturday which could bring brief 
MVFR conditions in light mixed winter precipitation on Sat. High 
pressure builds in on Sunday resulting in VFR conditions for the end 
of the weekend into early next week. 


&& 


Hydrology... 
Flood Warning continues for the Dan River at South Boston for minor 
flooding. 


&& 


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


&& 


$$ 
Synopsis...ams/jh/kk 
near term...kk 
short term...air mass 
long term...rcs 
aviation...jh/kk 
hydrology...jj