Area Forecast Discussion
Issued by NWS Blacksburg, VA

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000 FXUS61 KRNK 150636 AFDRNK Area Forecast Discussion National Weather Service Blacksburg VA 236 AM EDT Fri Sep 15 2017 .SYNOPSIS... High pressure will build over the Mid Atlantic region tonight and cover much of the eastern United States through Sunday. A cold front will approach the region from the northwest on Monday and Tuesday. A gradually warming trend to slightly above normal temperatures is expected through the middle of next week. && .NEAR TERM /THROUGH TODAY/... As of 1113 PM EDT Thursday... Due to less cloud cover over southwest Virginia into the NC foothills, appears fog will become a little more favorable in forming. Anticipate that skies will clear enough to allow patchy fog at most locations overnight, but not enough for a dense fog advisory at the moment, but will have to monitor. No other major changes to the forecast were made with this update, as showers over southside VA/NW NC piedmont, weaken and lift northeast by 3am. Previous discussion from early evening... Still a considerable amount of cloudiness around across the region. Noting some increased shower development from south of Lynchburg into Southside VA and the north- central NC Piedmont, forced by weak convergence along with dewpoints in the mid 60s and some breaks in stubborn overcast. Good agreement from the 12z WRF NMM, 21z HRRR and 18z 3-km NAM in progressing these showers northeastward and dissipating fairly early tonight (~ 02z). Surface ridge should begin to build in later tonight. While it`s unlikely skies fully clear out especially in the western Appalachians in WV, shallow but rather stout inversion depicted in BUFKIT soundings should allow for patchy mist or light ground fog to develop in cloud breaks after midnight. Lows mid 50s to lower 60s appear on track with no alterations needed there. Previous near-term discussion issued at 310 PM Thursday follows... Surface high pressure builds over the region tonight and Friday. No organized lift or forcing this time and winds are to weak to contribute with any upslope component. This will limit the best probability of precipitation to the afternoon and evening. Even with daytime heating, there will not be much instability on Friday. Bufkit forecast soundings for Friday morning showing shallow, but strong surface based inversion favoring fog. Still question the extent and timing of fog formation with at the cloud cover but will hold it in the overnight forecast for now. Models move deeper moisture to the northeast tonight then hold moisture in below 850MB with sporadic breaks. Will stay close to guidance for temperatures. && .SHORT TERM /TONIGHT THROUGH SUNDAY/... As of 310 PM EDT Thursday... High pressure remain over much of the eastern United States through Sunday. Saturday night and Sunday surface and low level wind turn to the northeast with slightly increasing winds speeds between the high and Tropical Storm Jose. Expecting broad upper ridging over the eastern United States Friday night through Sunday with 850MB temperatures gradually warming from around +12 to +16. Similar weather pattern continues through Sunday with little to trigger any precipitation. Guidance reasonable for temperatures through the period. && .LONG TERM /SUNDAY NIGHT THROUGH THURSDAY/... As of 200 PM EDT Thursday... This portion of the forecast will be characterized by limited chances of precipitation and little deviation of temperatures from day to day, with these readings averaging five to eight degrees above normal. The best, perhaps only, chance of precipitation during this timeframe will be on Monday. We will be watching a cold front approach the area from the west. While guidance is fairly uniform with this feature reaching the area, it is also fairly uniform with our area within a subsidence zone, on the northwest side of Hurricane Jose, as it potentially tracks north, east of the east coast of the U.S. So what precipitation the front brings with it will be squelched by first limited moisture, and increasing local subsidence. The forecast will reflect isolated showers through the day, with isolated showers and storms in the afternoon, with the focus across the mountains. Sunday night through early Thursday, both surface high pressure, and a building ridge aloft will minimize precipitation chances, and provide for more sun than clouds. Thursday, we will be watching another cold front approach from the west. Guidance among the models is not as uniform with this feature as it is with the Monday feature. Will allow for isolated coverage across the mountains for showers, but confidence is lower than that of Monday. During the period, low temperatures will range from the mid to upper 50s across the mountains and around 60 to the lower 60s across the Piedmont. High temperatures will range from the mid to upper 70s across the mountains with readings around 80 to the lower 80s across the Piedmont. && .AVIATION /06Z FRIDAY THROUGH TUESDAY/...
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As of 230 AM EDT Friday... Expect IFR conditions to develop at TAF sites west of the Blue Ridge as radiational fog/stratus become established through daybreak. Conditions will become VFR for all sites by mid morning, but short wave energy undercutting a weak upper level ridge will combine with orographic affects to bring just a slight chance for a shower to the southern Blue Ridge into the mountains of NC and also for the Alleghany Highlands. With sparse coverage expected will keep all TAFs VFR/dry through the end of the valid period. Winds will be light through the period. Extended Aviation Discussion... Some MVFR showers are possible on Saturday with another short wave. The chance of precipitation remains low for Sunday and Monday. Expect diurnal isolated showers and thunderstorms across the terrain. Aside from valley fog in the early morning, conditions overall should be VFR. Tuesday may feature some isolated MVFR showers in the mountains.
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&& .RNK WATCHES/WARNINGS/ADVISORIES... VA...None. NC...None. WV...None. && $$ SYNOPSIS...AMS NEAR TERM...AL/AMS/WP SHORT TERM...AMS LONG TERM...DS AVIATION...MBS/AL

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