790 
fxus61 krnk 051845 
afdrnk 


Area forecast discussion 
National Weather Service Blacksburg Virginia 
245 PM EDT Sat Jul 5 2008 


Synopsis... 
a stationary front across West Virginia into eastern Tennessee 
will provide the focus for showers and storms through early next 
week. Another cold front will approach the area from the northwest 
on Wednesday then stall out in our area...keeping the chance of 
showers and storms through next week. 
&& 


Near term /through tonight/... 
good lift and a lot of moisture available tonight. Between ongoing 
scattered showers and thunderstorms around 00z and then upper 
diffluence with jet streak overnight will have very high chance of 
rain. Will also keep mention of heavy rain in the forecast since 
surface reflection of upper trough will be backing the low level winds 
to the southeast or east for at least a short time tonight leading 
to good upslope conditions. With surface dew points in the lower 60s 
to lower 70s...will keep minimum temperatures very mild...at or 
above mav guidance. 


&& 


Short term /Sunday through Tuesday night/... 
small shortwave moving northeast across southwest Virginia will exit the 
NE corner of the forecast area early tomorrow...but with upper low 
still to our west...scattered showers and storms are again 
expected Sunday...with the greatest coverage along weak low level 
convergence boundary east of the Blue Ridge...where highest probability of precipitation 
were placed. Isolated severe weather is possible as BUFKIT soundings 
show more middle level dry air than seen today. 


Ohio Valley upper low opens and slowly drifts northeast...but we will 
again be on the east side of this feature Monday. Weak shortwaves 
moving north ahead of this feature across the far eastern portion 
of our forecast area will once again bring scattered showers and 
storms. Convective available potential energy in excess of 1000 j/kg are forecast in the 
east...bringing another threat for severe weather. 


Upper wave finally forecast to pass east of the forecast area 
Tuesday...but Theta-E ridge advancing ahead of next system moves 
into the mountains. This combined with afternoon heating should 
spark scattered tsra/ra...mainly in the mountains. 


Temperatures should gradually warm each day...as cloud cover and 
precipitation coverage lessen...with warmest day of the short term 
period on Tuesday...as southwest flow behind departing shortwave 
brings warmer 850 mb temperatures. 
&& 


Long term /Wednesday through Saturday/... 
main forecast feature early in the long term period is low amplitude 
trough that moves across southeast Canada/northern Great Lakes 
Wednesday and into northern New England on Thursday. As this trough 
moves east...a cold front will push into the area Wednesday night. 
Timing of this frontal passage is slower in most recent model runs 
as it encounters strong Southeast Ridge. As a result...will place 
higher probability of precipitation in the mountains ahead of this feature for Wednesday. 


GFS keeps upper trough more amplified through Friday...and thus keeps 
surface boundary a little further south than European model (ecmwf). Preferred European model (ecmwf) 
solution which keeps frontal boundary located in the forecast area 
Thursday and Friday. With uncertainty on location of this 
boundary...will keep probability of precipitation in the chance category through the long 
term period. 


Temperatures will be above normal on Wednesday...but clouds and 
southeast low level Friday and Saturday will bring temperatures down 
slightly to near or slightly below normal. 


&& 


Aviation /18z Saturday through Thursday/... 
scattered showers and thunderstorms with MVFR to IFR ceilings and 
visibilities will continue across the forecast area this afternoon 
and evening aided by daytime heating and short wave moving through 
southwest Virginia. 


There may be a lull in the precipitation after sunset when 
conditions briefly improve to VFR but a large area of rain is 
expected to cross the area...mainly between 03-09z in association 
with another jet streak and short wave. Low level winds will be 
east to southeast overnight so the rain...fog and 
clouds...especially on the east slopes on the Blue Ridge will 
create IFR to LIFR ceilings and visibilities. 


Once the rain moves out Sunday morning and surface winds come 
around to the south and southwest the fog and stratus will 
dissipate with VFR ceilings and visibilities for the rest of the 
morning. 


The upper trough is not forecast to move east of the County Warning 
Area until Tuesday morning so expect several periods of MVFR to 
IFR conditions with showers and thunderstorms Sunday night through 
Monday night. Dry weather is expected on Tuesday. 


&& 


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


&& 


$$ 
Synopsis...ph 
near term...air mass 
short term...ph 
long term...ph 
aviation...air mass