580 
fxus61 krnk 070712 
afdrnk 


Area forecast discussion 
National Weather Service Blacksburg Virginia 
312 am EDT Tuesday Oct 7 2008 


Synopsis... 
cool high pressure will build across the middle Atlantic region today 
while wedging south along the eastern slopes of the Blue Ridge into 
tonight. The high should begin to weaken and slide offshore 
by midweek ahead of a complex low pressure system that will affect 
the area Wednesday through Friday. 
&& 


Near term /through today/... 
low clouds have expanded across much of the region early this 
morning in response to deepening easterly flow and the 850 mb front 
crossing the Blue Ridge. Expect this trend to prevail through much of 
the morning hours as cool advection becomes more prominent from NE 
to SW behind the true frontal boundary. Then tricky as to how much 
clearing takes place this afternoon given trapped low level relative humidity by 
high heights aloft but also well mixed which could lead to lifting 
out/thinning of moisture by midday. Latest NAM which has been 
best backs the cloud cover down to the SW by afternoon as some 
boundary layer drying occurs from the NE as the surface high 
builds south. However a bit Leary of flow turning more southeast later on 
espcly Blue Ridge where some spots could hang onto clouds for much 
of the day. Thus will linger cloud cover a bit longer over the SW 
and allow more sun north/NE and across southeast wva where downslope 
trajectory will take place. High temperatures very tricky since starting 
out pretty warm...with falls expected early on...then slow rises 
where sunny breaks develop. Think warmer mav MOS likely best parts 
of the far west and east but could see readings closer to the 
chilly met MOS Blue Ridge if clouds hold longer. 
&& 


Short term /tonight through 6 PM Wednesday/... 
strong surface ridge will anchor in east of the mountains overnight 
before sliding offshore Wednesday. Any leftover low clouds will likely 
entrench again overnight per southeast flow with increasing high/middle 
clouds ahead of the middle miss valley upper low. Low temperatures again 
iffy with better radiational cooling possible east and only a 
small diurnal swing west where lingering clouds more prevalent. 
Since trend has been toward the warmer ensemble MOS...stayed 
slightly above the milder mav tonight. 


For Wednesday...upper low to the west will begin to push its axis of 
warm advection/isentropic lift precipitation shield toward the area as the 
short wave ridging heads east. Timing and eastward expanse of the precipitation 
still in question given lingering dry air aloft and best lift to the 
west. Latest GFS/European model (ecmwf) fastest in plowing into the riding while the 
NAM/Canadian hold back and keep most rainfall to the SW of the 
strong wedge. Since sref about in between only made minor adjusts 
with 20ish pop far west Wednesday morning...then slow eastward expansion 
to east of the Blue Ridge in the afternoon. Highs again tricky 
pending timing of rain and whether or not the east sees any early 
sun. Think could be a gradient from only around 60 far west to low 
70s east so adjusted accordingly. 
&& 


Long term /Wednesday night through Monday/... 
confidence in the extended remains rather low in regards to rainfall 
coverage and quantitative precipitation forecast given differing solutions and whether or not some 
cutoff of precipitation to the south/southeast will occur. Latest GFS remains 
about the most consisent in giving one round of decent rain showers while 
the Canadian very wet through the period and the European model (ecmwf) about in 
between per more ridging to the north. Otherwise surface low develops under 
the upper low across Georgia/SC Wednesday night into Thursday with best axis of 
lift moving through the area later Wednesday night into Thursday. Influx of 
moisture arrives in full...although should see heavier precipitation over 
the southeast coast into interior Georgia. Will have likely probability of precipitation over 
the south to 30-40 north into Thursday morning...then decrease 
somewhat to just low chance Thursday afternoon-Thursday night except across 
the far south as the low pushes into the Atlantic. Appears front 
may hang up over the southeast Friday-Saturday...and will keep 
slight chance showers in for the southeast County Warning Area into Saturday 
before dry wedge of hi pressure noeses in from the northeast sun- 
Monday. Another front looks to arrive by the end of day 7. 
&& 


Aviation /07z Tuesday through Saturday/... 
high pressure will build down the East Coast tonight and Tuesday. 
This will bring the low level winds around to the southeast by 
Tuesday morning producing upslope cloudiness. Stratus will result 
in MVFR ceilings over the mountains...including the Blue Ridge...and 
effecting the following terminals...roa blf lwb. Mainly VFR cloud 
bases will be found elsewhere...lyh and Dan. 


Rain will be moving into the area by Thursday...lingering into 
Friday as surface low moves from the Central Plains across the 
southeast United States. 


&& 


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


&& 


$$ 
Synopsis...jh/wp 
near term...jh/PM 
short term...jh/wp 
long term...jh/wp 
aviation...PM