Area Forecast Discussion
Issued by NWS Blacksburg, VA

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000 FXUS61 KRNK 250548 AFDRNK Area Forecast Discussion National Weather Service Blacksburg VA 148 AM EDT Thu Aug 25 2016 .SYNOPSIS... High pressure over the mid Atlantic shifts slowly east into Thursday. The upper ridge will remain overhead through the end of the workweek. && .NEAR TERM /THROUGH TODAY/... As of 845 PM EDT Wednesday... Soundings show a decent increase in pwats this evening although showers have been limited by weak capping aloft under high pressure including lack of forcing/instability. Models continue to show a piece of mid level energy associated with ongoing convection to the northwest approaching late as the flow turns more westerly. This weak convergence setup may be able to aid a few showers over the far west by daybreak, so leaving in some low pops toward morning mainly northwest mountains. Otherwise expect quite a bit of sheared high/mid clouds from Ohio Valley convection to spill into western sections overnight, with some lower clouds possible western ridges given weak upslope, and out east early on per residual cumulus/strato-cu. This cloudiness may tend to limit fog while keeping low temps up more in the mid 60s and perhaps staying around 70 in spots. Thus making small adjusts to limit fog some while staying on the warmer side of latest mos outside the valleys. Previous discussion as of 303 PM EDT Wednesday... Building heights aloft to keep most showers and storms limited. However, will be watching an area of convection in northern Indiana this afternoon as models trend the flow more wnw to ese over time, but in general keep threat further north late tonight. Still looks as if some cloudiness will be around again late tonight as the wave moves across the mid-Atlantic states. Thursday the center of the upper high slides across the Southern Appalachians and Tennessee Valley. Another weak upper impulse may scoot by early threatening the mountains with a few showers in the morning then some break after midday before possible isolated convection in the afternoon. Difficult forecast in terms of cloud cover and sunshine. Expecting more clouds than sun especially in the mountains and foothills. Still with warming aloft, temps will be reach the 80s across the entire CWA, and should close in on 90 toward Buckingham, VA to Yanceyville, NC. && .SHORT TERM /TONIGHT THROUGH SATURDAY NIGHT/... As of 400 AM EDT Wednesday... An upper level ridge of high pressure is forecast to hold strong over the Mid-Atlantic states into this upcoming weekend with 5H heights hovering between 594-597 dm. As such, anticipate strong subsidence, above normal temperatures, and little or no precipitation threats. Certainly can`t rule out an isolated shower or thunderstorm during the period, but warming aloft will limit instability, and lack of dynamic forcing should keep the rain threat to a minimum. Summer heat and humidity will be the forecast highlight, 850mb temps of +18C to +22C supporting daytime highs ranging from the 80s mountains to the lower to mid 90s across the piedmont. Overnight lows will be warm and muggy too, dewpoints in the 60s to lower 70s not allowing for much radiational cooling. && .LONG TERM /SUNDAY THROUGH WEDNESDAY/... As of 410 PM EDT Wednesday... The main focus across the eastern half of the nation into early next week will be the persistent upper level ridge, and a developing tropical system which has the potential to impact parts of Florida. Regardless of the tropics, our weather will be most influenced early in the week by the persistent upper level ridge of high pressure. This feature will ensure that heat and humidity will be persist with daytime temperatures running at least 4 to 7 degrees above normal, and overnight lows a full 10 degrees above normal. There will be a threat of diurnally driven showers and thunderstorms, but this activity is expected to be mainly confined to the mountains and lack any significant organization due to poor dynamic support. && .AVIATION /06Z THURSDAY THROUGH MONDAY/...
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As of 148 AM EDT Thursday... VFR conditions will prevail through most of the TAF valid period as high pressure both surface and aloft moves slowly east across the region. Mid and high level clouds will move northeast across the region this morning with some lower strato- cumulus possible in the mountains as the low level flow turns more westerly. This could bring a period of MVFR cigs to locations from KBCB and points west early this morning. With light winds and low level moisture, patches of fog are possible this morning, especially at KLWB, but could also occur at KBCB/KLYH with thinning of high clouds. Any fog will be gone by mid morning today. Deeper moisture will return from the west across the area today as the surface high shift east. A weak upper disturbance evolving from upstream convection could cross the mountains this morning and eastern sections this afternoon while weakening. This feature could bring some showers to the northwest mountains through midday with isolated redevelopment possible mainly Blue Ridge west this afternoon with heating. Coverage still appears too low to include in any of the taf sites espcly given uncertainty early in the day and spotty coverage in the afternoon. Therefore keeping VFR under mainly scattered-broken cumulus fields and without any shra/tsra mention for this afternoon. Outside of convection, winds will be light and variable. Expect any showers to quickly fade this evening with mainly VFR returning outside of patchy late night fog/stratus in the valleys. morning low clouds and fog will lift quickly Friday morning, returning to VFR conditions. Medium confidence in ceilings,visibilities and winds during the taf period. Extended aviation discussion... Storms will again be isolated and mainly confined to the mountains on Friday as upper ridging strengthens, while a weak surface front stalls to the north. Brief MVFR conditions could occur where any convection does develop but appears mainly VFR given spotty nature to any showers. The front lingers in the area during the weekend keeping enough moisture for diurnal mountain showers and storms when periods of MVFR could occur. Monday high pressure bubbles in but still a very humid airmass to keep isolated mountain storms around in the afternoon, but mainly VFR.
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&& .RNK WATCHES/WARNINGS/ADVISORIES... VA...None. NC...None. WV...None. && $$ SYNOPSIS...KK/WP NEAR TERM...JH/WP SHORT TERM...PM LONG TERM...PM AVIATION...JH/KK is the U.S. government's official web portal to all federal, state and local government web resources and services.