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fxus61 krnk 201907 
afdrnk 


Area forecast discussion 
National Weather Service Blacksburg Virginia 
307 PM EDT Wednesday Aug 20 2008 


Synopsis... 
last nights cold front has moved south to the North Carolina and 
South Carolina state line. High pressure will control our weather 
pattern through the weekend. A cold front will move into and then 
stall across the region early next week. 


&& 


Near term /through Thursday/... 
winds have come around to the east and northeast across the forecast 
area. High pressure at the surface will continue to build in tonight 
and Thursday. The easterly component of low level winds around the 
high will bank moistures along the east slopes of the Blue Ridge 
tonight resulting in a layer a stratus or stratocumulus developing 
by 06z. The Canadian...which usually does a decent job with clod 
cover and other models show the clouds dissipating in the morning. 
Clouds may take even longer to break up Thursday with all the 
subsidence due to the surface high and rising 500 mb heights and 
with the airmass become more stable throughout the day. 


Enough clouds and mixing tonight to keep fog from spreading across 
the Greenbrier and New River valleys. Wind and clouds will also hold 
temperatures in the lower to middle 60s...especially in the foothills 
of North Carolina. Went on the cool side of guidance in the 
southwest with more clouds expected in the morning...and close to 
mav guidance for the rest of the County Warning Area. 


&& 


Short term /Thursday night through Saturday/... 
east to southeast surface-850 mb flow will continue tomorrow night into 
at least Friday night before becoming more southerly on Saturday. 
All guidance points towards a good amount of moisture at that level 
having Atlantic origins. Above this level...the atmosphere will be 
notably drier...so while the forecast will suggest periods of better 
upslope cloud cover for the northern mountains and foothills of North 
Carolina...and neighboring locations in Virginia...no measurable 
precipitation is expected at this time. While a sprinkle can not be 
ruled out...will not place any mention of precipitation in the 
forecast at this time. If there would be any mention...currently 
Friday night looks like the best chance as the higher relatively 
humidities will briefly extend to 700 mb during this time. 


By Saturday...the orientation of the wind should be south enough 
that any upslope component should be very limited. 


&& 


Long term /Saturday night through Wednesday/... 
much of the forecast during this time period will depend upon just 
where the remnants of Fay travel...and at what speed. To maintain 
consistence with the National centers...this portion of the forecast 
will mirror the guidance provided by HPC. Two events will be 
happening. A cold front will be approaching from the northwest. The 
remnants of Fay are currently prognosticated to head slowly west over the 
Gulf Coast states. Just how much moisture from the remnants of Fay 
get drawn into the dynamics of the front is the big question. The 
forecast will first reflect isolated to scattered precipitation 
associated with the approaching to first take place across the 
western part of the area during the day on Sunday and into the night 
on Sunday. Perhaps starting Monday...but with a greater potential 
Tuesday into Wednesday is the time period to watch for a better 
chance of precipitation with the influence of ray moisture reaching 
our area. 


&& 


Aviation /19z Wednesday through Monday/... 
the backdoor cold front will dissipate over North Carolina 
tonight. High pressure will wedge down the east side of the 
Appalachians bringing more stable air into the region by Thursday. 


The easterly component of low level winds around the high will 
bank moistures along the east slopes of the Blue Ridge tonight 
resulting in a layer a stratus or stratocumulus developing by 06z. 
All models show the clouds dissipating in the morning. Have kept 
MVFR clouds out of the tafs for now. Most likely location that may 
have low ceilings if the coverage of the stratus is 
extensive is roa...probably between 09-15z. There will be fog 
overnight at klwb...which could lower to IFR by morning if 
winds/clouds are less...but at this time expect winds to stay up 
enough to keep the visibility in the MVFR range. 


Dry high pressure and easterly flow will keep a persistent 
weather pattern over the region Thursday into Friday. Rain showers may develop 
just south of the taf sites Friday afternoon in deepening southeast 
flow...otherwise expect subsidence to limit moisture for the most part. 


Continued overall persistence VFR conditions through the weekend 
with Fay moisture to the south...the next cold front to the northwest...and 
high pressure ridged in overtop the area from the NE. 


&& 


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


&& 


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