Area Forecast Discussion
Issued by NWS Blacksburg, VA

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833 FXUS61 KRNK 182015 AFDRNK Area Forecast Discussion National Weather Service Blacksburg VA 315 PM EST Wed Jan 18 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 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 /THURSDAY NIGHT 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 /20Z WEDNESDAY THROUGH MONDAY/... As of 1230 PM EST Wednesday... MVFR SCT to BKN clouds will continue this afternoon into tonight in the western taf sites of KBLF and KLWB. Gusty Northwest winds will continue in the mountains, including Roanoke this afternoon, then winds will trail off this evening into overnight with high pressure building in. Some gusts could exceed 30 to 35 mph early this afternoon. As high builds in tonight the lower cigs at KBLF and KLWB should erode as well becoming scattered by 02z. VFR conditions will prevail after 02z and continue into Thursday. High confidence in ceilings,visibilities and winds during the taf period. Extended Aviation Discussion... VFR conditions will continue into Thursday afternoon. However, this is expected to be short-lived as moisture returns from the southwest. Expect periods of rain Thursday night-Friday night, then again Sunday into Monday. During this time expect sub-VFR cigs and at times vsbys. && .RNK WATCHES/WARNINGS/ADVISORIES... VA...None. NC...None. WV...None. && $$ SYNOPSIS...KK/WP NEAR TERM...KK SHORT TERM...MBS LONG TERM...MBS AVIATION...KK/WP is the U.S. government's official web portal to all federal, state and local government web resources and services.