Area Forecast Discussion
Issued by NWS Blacksburg, VA

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000 FXUS61 KRNK 240753 AFDRNK Area Forecast Discussion National Weather Service Blacksburg VA 353 AM EDT Sat Sep 24 2016 .SYNOPSIS... Cold front arrives from the north today, moving south into the Carolinas Sunday, before stalling. Another cold front will shift in from the west Tuesday. && .NEAR TERM /THROUGH TONIGHT/...
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As of 342 AM EDT Saturday... Clear skies across our area this morning with weak high pressure centered over the Alleghany Highlands. Some fog will be around in the river valleys around dawn then clear out by 9am. Looking at a cold front stretched from northern Ohio into Pennsylvania this morning to move south into the Shenandoah Valley by midday then to the NC border by dark. Mainly dry weather with this front given limited low level moisture. A few showers still possible from the mid deck accompanying the front mainly from the Alleghany Highlands to the piedmont late today. Looking at sunshine this morning giving way to cloudier skies this afternoon over the north. Still overall a warmer than normal day, with warmest temperatures in the NC piedmont and foothills, where some may approach 90. Elsewhere mainly 80s. Tonight behind the front models agree on increasing the low level moisture from the Greenbrier Valley east across the Virginia piedmont. Threat of light rain and drizzle exists along and east of the Blue Ridge north of the NC border overnight, with some light rain as far west as the Alleghanys. Fog will also be around in the higher terrain of the Blue Ridge and late in the Mountain Empire of SW Virginia into NW NC where skies should stay clear to partly cloudy, while the rest of the region stays cloudy. Lows will be affected by the cloud cover and be held up in the lower to mid 60s, with mid to upper 50s across portions of the mountains.
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&& .SHORT TERM /SUNDAY THROUGH TUESDAY NIGHT/...
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As of 330 AM EDT Saturday... A high amplitude upper ridge will allow a cool and moist high pressure wedge to remain in place along the east slopes of the Appalachians for Sunday and into Monday. Isentropic lift coupled with low level moisture will be sufficient to generate some precipitation, mainly of the drizzle/sprinkle variety, with the best chances along the Blue Ridge. As the upper ridge axis pushes to our east Monday, a vigorous closed low will drive an area of low pressure across southern Canada and swing the trailing cold front to our western doorstep by evening. Expect the wedge to hold tough through Monday with some erosion along the western and southern flanks, until the cold front passes through and scours it out Monday night. This scenario will yield increasing precipitation chances with the focus shifting westward with time. Some late day thunder is also possible well west of the Blue Ridge as unstable air encroaches on the eroding flanks of the wedge. The best chance of showers will be Monday night with the frontal passage, with some precipitation lingering into Tuesday in the east as the low level flow is slow to come around to the northwest to usher the front along. Temperatures in the wedge on Sunday and Monday will be running a few degrees below normal generally in the 70 to 75 degree range, with some warmer readings on the fringes of the wedge far west and south. Out of the wedge and behind the front on Tuesday, temperatures will be in the mid/upper 70s east to upper 60s/lower 70s west.
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&& .LONG TERM /WEDNESDAY THROUGH FRIDAY/...
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As of 330 AM EDT Saturday... Conditions will be improving by Wednesday as the upper trof axis swings through the region and the surface front continue to push away from the area. Used a Superblend/ensemble solution for timing of features. High pressure will then bring us fair and seasonable weather as it builds over the eastern part of the country for the end of the week.
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&& .AVIATION /08Z SATURDAY THROUGH WEDNESDAY/...
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As of 145 AM EDT Saturday... Could see fog at all but BLF/ROA/LYH this morning. At Danville, there is fog forming southeast of this terminal as of 530z. With higher dewpoint air remaining, there is a good chance of low end MVFR/high end IFR vsby here around 08-12z. Across the mountains, confidence is not that high, but enough to keep tempo of LIFR at LWB, but bumped vsbys up at BCB to 3sm, as airmass stays dry. However, with light northwest wind fog along the New River could advect into BCB toward 11-12z. Otherwise will see VFR conditions this period. Cold front backdooring from the north looks to bring some mid deck into the LWB-ROA-LYH corridor by early afternoon reaching BCB/DAN late in the day. Models favoring along and west of BCB-BLF with scattered clouds. Lowering of ceilings to low end VFR expected at ROA/LYH and possibly BCB by end of the taf period. Extended aviation discussion... As the weekend progresses and the backdoor front stalls just to our south allowing easterly flow to become established across the region, low-level moisture increases and a wedge evolves. Expect cigs to lower into the MVFR category or worse Sunday morning and likely remain in place through Monday with areas of fog and drizzle or light rain developing with time as well, especially along the east facing slopes of the Blue Ridge. A strong, but slow moving, cold front will be approaching the area from the west on early Tuesday. Models have significant differences on the timing and location of this front, but rain chances during the first half of next week will be on the increase. Until the front pushes across, Tuesday, we should stay in a period of sub-VFR at times, especially northeast of a line from LWB-BCB-DAN.
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&& .RNK WATCHES/WARNINGS/ADVISORIES... VA...None. NC...None. WV...None. && $$ SYNOPSIS...WP NEAR TERM...WP SHORT TERM...MBS LONG TERM...KK/MBS AVIATION...RAB/RCS/WP

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