Area Forecast Discussion
Issued by NWS Blacksburg, VA

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000 FXUS61 KRNK 190517 AFDRNK Area Forecast Discussion National Weather Service Blacksburg VA 117 AM EDT Sat Aug 19 2017 .SYNOPSIS... A weak cold front will cross the mountains from the west this evening before sliding southeast of the region overnight. The front will remain over the Carolinas Saturday into Sunday before dissipating. High pressure works in from the Ohio Valley during the weekend, then overhead Monday resulting in drier weather across the region. && .NEAR TERM /THROUGH TODAY/... As of 810 PM EDT Friday... Deep convection ahead of the cold front is exiting off to the east as the actual surface boundary is entering from the west with just a few isolated showers. Expect precipitation to be winding down shortly with dry conditions for the overnight. The airmass behind the front is not a remarkable change and expect the boundary layer to remain moist. Combined with decreasing cloud cover allowing for some radiational cooling, patchy valley fog looks like a good bet west of the Blue Ridge. Lows tonight will be in mid 60s to around 70 degrees east of the Ridge, with low/mid 60s west with some cooler readings in the valleys. Previous discussion... Weak cool advection along with slightly lower dewpoint air will follow the front in from the northwest by morning allowing lows to dip well into the 60s mountains, while lingering closer to 70 southeast. Fog likely limited to the deeper valleys and eastern sections that possibly see more showers through early evening. Front sags into the Carolinas before stalling Saturday in advance of the next shortwave trough that will approach the region during the afternoon. This should basically put the area in between deeper moisture to the southeast, and lift beneath the cold pool with the shortwave crossing the Ohio Valley. Latest guidance supports an overall dry scenario with dry air aloft off forecast soundings, and low level northwest flow beneath rather meager instability Saturday afternoon. Cant totally rule out a sprinkle or shower reaching the far northwest counties late in the day but not enough to include a pop mention for now. Otherwise partly to mostly sunny and a bit less humid with highs still 80s to near 90 east, as weak downslope offsets slight cooling aloft. && .SHORT TERM /TONIGHT THROUGH MONDAY NIGHT/... As of 240 PM EDT Friday... An upper level trough will pivot over the region Saturday night. Not much cool air is behind this trough, therefore temperatures Sunday will warm back above normal with mid 80s west to near 90F east. The only notable change will be slightly drier air (dew points in the low 60s west to upper 60s east) with a westerly breeze. Dry high pressure with increasing heights aloft will continue to keep most of the region dry through Monday night. Some low level moisture may creep into the area from the south Monday. This moisture and upslope flow may generate a few storms across the North Carolina High Country late in the afternoon, fading in the evening. Under mostly sunny skies, temperatures will warm a little above normal Monday with 80s west to lower 90s east. && .LONG TERM /TUESDAY THROUGH FRIDAY/... As of 255 PM EDT Friday... A western Atlantic upper level ridge will track westward over the Gulf states through early next week. This ridge will push temperatures 5F to 10F warmer than normal. With an increase in heat and humidity, scattered showers and thunderstorms are expected Tuesday afternoon across the mountains and then moving and fading across the foothills in the evening. On Wednesday, models are wanting to bring a cold front south into the Gulf states, pushing the upper level ridge into the Gulf. Considering climatology for the time of year, models look to be over zealous with moving this front into a hot and humid air mass. I would not be surprised to see a slowing trend with the frontal passage being more towards Thursday. For now, kept timing close to guidance while keeping PoPs low. Until the front clears the area, temperatures will stay 5F to 10F warmer normal. Following the front, temperatures will be 5F or cooler than normal. && .AVIATION /05Z SATURDAY THROUGH WEDNESDAY/...
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As of 113 AM EDT Saturday... VFR conditions for the overnight east of the Blue Ridge. However, the airmass behind the front is not a remarkable change and expect the boundary layer to remain moist. Combined with decreasing cloud cover allowing for some radiational cooling, patchy valley fog looks like a good bet west of the Blue Ridge with LIFR for KLWB, and a tempo to IFR at KBCB. Fog also setting in at BLF per southwest flow, and some LIFR tempo expected there until 09z. Fog/stratus will dissipate early Saturday morning, allowing high pressure to bring VFR conditions to all TAF sites through the end of the valid period. Winds will generally be light. Extended Aviation Discussion... Mainly VFR conditions for the second half of weekend under weak high pressure. Scattered thunderstorms and periods of MVFR conditions return next week, with late night/early morning fog possible almost any day. Better potential for sub-VFR will come Wednesday when more widespread showers and storms arrive with the next cold front.
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&& .EQUIPMENT... As of 400 AM EDT Friday Aug 18th... KFCX doppler radar expected to be down for the rest of the month due to a failing bull gear. Technicians are working on the radar, through next week and the radar will most likely stay down completely as the repairs are being made. && .RNK WATCHES/WARNINGS/ADVISORIES... VA...None. NC...None. WV...None. && $$ SYNOPSIS...JH NEAR TERM...JH/MBS SHORT TERM...RCS LONG TERM...RCS AVIATION...JH/MBS/WP EQUIPMENT...RAB/WERT/WP is the U.S. government's official web portal to all federal, state and local government web resources and services.