819 
fxus61 krnk 220132 
afdrnk 


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


Synopsis... 
high pressure over the Ohio Valley will move northeast into New 
England by late Sunday. Low pressure off the Gulf Coast will track 
toward the southeast coast by Sunday night. 


&& 


Near term /through Sunday/... 
surface high pressure over the Ohio Valley will move northeast 
into New England tonight and Sunday. Low pressure along the 
Louisiana coast will move northeast toward the Carolina coast by 
late Sunday. 


Light and variable surface winds tonight will gradually become 
east by Sunday afternoon and continue to veer to the southeast by 
late in the day. Models are showing increasing middle and high level 
moisture with a dry layer between 600 and 900 mb. None of the 
guidance...including the HPC and Storm Prediction Center sref...the local WRF or 
BUFKIT show any precipitation in the forecast area until after 
18z...and that is just for the northwest North Carolina mountains. 
By 00z Monday the chance of rain will reach the rest of northern 
North Carolina and extreme southern Virginia. Have adjusted the 
timing and slowed down the onset of rainfall to account for this 
guidance. 


Played lows tonight close to MOS...dropped a couple degrees from 
previous forecast due to slower arrival of clouds. High 
temperatures on Sunday will be influenced by the delayed onset of 
precipitation and thickening loud cover. Went with adjmavbc. 


&& 


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 /02z 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...ams/wp 
near term...air mass 
short term...ds 
long term...reb 
aviation...ams/kk