Area Forecast Discussion
Issued by NWS Blacksburg, VA

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000 FXUS61 KRNK 190514 AFDRNK Area Forecast Discussion National Weather Service Blacksburg VA 1214 AM EST Thu Jan 19 2017 .SYNOPSIS... Weak high pressure builds over tonight, then another storm system moves over the southern Appalachians by Friday. Another storm system approaches from the southwest early next week. .NEAR TERM /THROUGH THURSDAY/... As of 1130 PM EST Wednesday... First of several negatively titled upper systems to move into the eastern U.S. spreading high clouds across the area this evening. Needed to increase cloud cover quite a bit overnight to accommodate the current and expected high clouds that will overspread the area tonight into Thursday. T/Td readings generally on track, so only minor changes needed with respect to those. AS OF 630 PM EST Wednesday... High pressure is edging into the region. Clouds along western slopes will erode through the night. Also on the decline are the winds as the pressure gradient weakens across the mountains. As high pressure tracks over the area, good radiational cooling will send temperatures down into the 30s overnight. There could be colder temperatures across the mountain valleys, however saturated ground may limit areas dropping into the upper 20s. AS OF 315 PM EST Wednesday... High pressure over western Kentucky this afternoon will build east overhead tonight. Aloft shortwave along the virginia coast will push further out into the Atlantic ocean. This will allow the upper ridge to build east tonight. Low temperatures tonight will range from around 30 degrees in northwest Greenbrier county to near 40 degrees along the southern Blue Ridge mountains. High pressure over our region Thursday will slide east into Thursday night. The upper level ridge swings trough the region bringing drier weather. Moisture and clouds will slowly increase Thursday afternoon from the southwest. High temperatures Thursday will average 8 to 18 degrees above normal with readings from around 50 degrees in the northwest mountains to around 60 degrees in the piedmont. && .SHORT TERM /TONIGHT THROUGH SATURDAY NIGHT/... As of 315 PM EST Wednesday... We will be under the influence of a progressive and transitory pattern an upper ridge moves to our east and a closed low over the midwest opens up to a progressive open wave, high pressure at the surface will shift to the coast and leave a lingering wedge in place. The upper trof will then drive a weakening surface low into the Great Lakes and push a front with good isentropic lift in to the region from the west. This will spread precipitation across the Appalachians and central mid Atlantic region Thursday night into Friday. By Friday afternoon, the upper trof will give way to some ridging and ending the bulk of precipitation through some lingering sprinkles are possible. By Saturday the ridging will give way to a developing trof to our west and increasing dynamic forcing in a moist environment will bring an increasing chance of precipitation to our region through Saturday night. With no change in airmass, expect temperatures to remain above normal through the period. && .LONG TERM /SUNDAY THROUGH WEDNESDAY/... As of 315 PM EST Wednesday... Guidance remains generally consistent with the big picture details Sunday into the first part of next week with some variation in the finer details. A large vertically stacked closed low will move across the deep south and bring a strong and very moist flow of air to the region. Several spokes of energy rotating around the low will bring several surges of precipitation to the region from Sunday through Monday before the system starts to pull away from the area by Monday night. So while the main baroclinic zone is now expected to be much closer to the coast, the overall scenario still favors widespread precipitation with significant orographic enhancement along the Blue Ridge. Will continue to keep a close eye on how this situation evolves as the indicated QPF amounts generally in the 1 to 3 inch range by Monday night may result in some flooding. Instability to drive thunder will likely reside closer to the baroclinic zone, though with enough forcing under the cold core upper low some thunder is possible but confidence not high enough at this point to include in the forecast. Will keep ptype as all liquid though dynamic cooling under the deep upper low may generate thickness values favorable for some wintry mix, but confidence in this is low. Some wrap around precipitation will liner west of the Blue Ridge through Tuesday before we can get a brief break ahead of the next system approaching later Wednesday night. Temperatures will trend down through Tuesday as the cold core low moves over the region, though readings will still remain above normal through the first part of next week. && .AVIATION /05Z THURSDAY THROUGH MONDAY/...
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As of 1200 AM EST Thursday... The first of several negatively tilted upper systems will approach the forecast area from the south Thursday night. High clouds will overspread the area in advance of this system, and are already doing so. Low clouds linger across eastern WV, but the lack of a significant west wind field has resulted in scattering out of the low clouds at KBLF, while they hold in at KLWB. All indications are that these clouds will gradually dissipate from the south through the night leaving both sites KBLF. Otherwise, expect BKN-OVC high clouds throughout much of the TAF valid period at all sites. Any further sub-VFR ceilings and precipitation will be beyond the end of the TAF valid period. No issues expected with visibility through the TAF valid period. Winds diminishing and becoming light and variable throughout the CWA. The winds will veer to the southeast through the day Thursday, but speeds are expected to remain mostly 5kts or less through the TAF valid period. Medium to high confidence in ceilings throughout the TAF valid period. High confidence in visibilities throughout the TAF valid period. Medium confidence in wind direction, high confidence in wind speed throughout the TAF valid period. Extended Aviation Discussion... Conditions will begin to deteriorate Thursday night from southwest to the northeast as a wave of low pressure track across the Tennessee Valley. Expect periods of rain Thursday night through Friday afternoon, then again Sunday into Monday. During this time expect sub-VFR cigs and at times vsbys.
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&& .RNK WATCHES/WARNINGS/ADVISORIES... VA...None. NC...None. WV...None. && $$ SYNOPSIS...KK/WP NEAR TERM...KK/RAB/RCS SHORT TERM...MBS LONG TERM...MBS AVIATION...RAB/RCS is the U.S. government's official web portal to all federal, state and local government web resources and services.