109 
fxus61 krnk 212344 
afdrnk 


Area forecast discussion 
National Weather Service Blacksburg Virginia 
644 PM EST Sat Nov 21 2009 


Synopsis... 
high pressure will remain across the area tonight. Low pressure 
developing across the Gulf Coast states will impact our weather 
Sunday while high pressure wedges down from the northeast. 


&& 


Near term /through Sunday/... 
surface high pressure over our region this afternoon will shift east 
tonight into Sunday. A low pressure center will move east along the 
Gulf Coast...then north along the Carolina coast Sunday through 
Monday. Models continued the trend of slowing the onset of precipitation 
associated with developing wedge and cyclogenesis over the northern 
Gulf. Leaned probability of precipitation towards a GFS/sref blend. 


Used Gem/GFS for cloud cover tonight and Sunday. Satellite loop 
showed high clouds thinning this afternoon across our area. 
However...cloud cover will increase tonight especially across the 
south late. Light flow will become east to southeast tonight. 
Played lows tonight close to MOS...dropped a couple degrees from 
previous forecast due to slower arrival of clouds. High temperatures 
are tricky for Sunday with delayed onset of precipitation and thicker cloud 
cover in comparison to Saturday. Went with adjmavbc for high 
temperatures on Sunday. 


&& 


Short term /Sunday night through Tuesday night/... 
the trend of the guidance to slow the precipitation associated with 
the coastal low will continue into Sunday night. Have made 
adjustments to the probability of precipitation that reflect a slower timing of the higher 
probability of precipitation into the area...however have maintained roughly the same 
orientation of those probability of precipitation with the highest percentage across the 
southeast part of the forecast area. Have continued the trend of a 
slower exiting system Monday into early Tuesday. As such...have 
increased probability of precipitation on Monday into Monday night as compared to earlier 
numbers. 


A strong...cool...rain fed wedge will develop by Monday...and last 
through at least Tuesday. As such...have gone with forecast high 
temperatures both Monday and Tuesday lower than guidance. By late 
Tuesday...but more especially Tuesday night...we will see a 
transition to isolated to scattered convective precipitation in 
advance of an approaching cold front. Will have isolated showers in 
the west Tuesday afternoon...but increasing coverage of showers from 
west to east on Tuesday night...but nothing higher than chance probability of precipitation 
at this time. 


&& 


Long term /Wednesday through Saturday/... 
European model (ecmwf) has a surface and upper level low over the Midwest 
approaching the region Wednesday night into Thursday morning. The 
low pushes northeast over the Great Lakes with most of the energy 
following and sliding north of the forecast area. Have chance probability of precipitation 
in the northern and central portions of the County Warning Area 
and tapering off from the southeast to northwest through Friday. 
Again with temperatures and 1000-850mb...850-700mb thicknesses 
lowering to near freezing...some light snow can be mixed in with 
the rain especially in the higher elevations west of the Blue 
Ridge Thursday night. 


Maximum temperatures will start cooling down into the low to middle 40s 
in the west to low 50s in the Piedmont areas of VA/NC. 


&& 


Aviation /00z Sunday through Thursday/... 
high pressure will remain over the region through Sunday with 
increasing middle and high clouds. Expect VFR conditions through the 
period with the exception of River Valley fog in West Virginia. So have 
maintained MVFR fog in lwb during the early morning. 


Low pressure will slide northeast from the Gulf Coast states to 
the southeast coast by Monday night. Ceilings will continue to 
lower Sunday through Monday. Rainfall is expected at the taf sites 
late Sunday. Models were still slowing down the arrival time 
of the rain...so with that in mind we may not see sub VFR 
conditions until after 00z Monday. 


Tuesday will feature improving conditions as the afc low tracks 
northeast up the eastern Seaboard...with high pressure building 
over the middle Atlantic for the middle of the week. 


&& 


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


&& 


$$ 
Synopsis...wp 
near term...kk 
short term...ds 
long term...reb 
aviation...ams/kk