Area Forecast Discussion
Issued by NWS Blacksburg, VA

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000 FXUS61 KRNK 172030 AFDRNK Area Forecast Discussion National Weather Service Blacksburg VA 330 PM EST Tue Jan 17 2017 .SYNOPSIS...
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A cold front will track into the mountains this evening, then move southeast to the coast by Wednesday morning. Weak high pressure builds over by late Wednesday, then another storm system moves over the southern Appalachians by Friday.
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&& .NEAR TERM /THROUGH WEDNESDAY/...
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AS of 327 pM EST Tuesday... A cold front to our west across central Kentucky and Tennessee this afternoon will east this afternoon and moves southeast through the forecast area tonight into Wednesday. An isolated thunderstorm may be possible over the Mountain Empire and northwest mountains of North Carolina with some instabilities this afternoon into tonight. However, not expecting to much thunder because of cloud cover and rain. The HiResw-arw-east, HRRR, RAP and NAM support placing the highest pops in the west this evening into Tonight. The GFS and ECMWF seem to develop an area of deeper convection east or southeast of our forecast area. The shortwave rotating through Southeast West Virginia supports likely pops in the west, with chance pops to the east. It will remain mild tonight with readings from the upper 30s in the northwest mountains to the mid 50s in the Piedmont. Increased winds speed late tonight into Wednesday morning. From Grayson county Virginia south through portions of the Northwest mountains of North Carolina, winds will approach wind adv levels for a small window around 12z. Because of limited areal coverage and time coverage with lagging CAA will hold off on any wind adv headlines. The northern-stream trough exits Wednesday morning,then a ridge builds in from the west Wednesday afternoon. High pressure will build southeast out of the Ohio Valley. High temperatures Wednesday will vary from around 40 degrees in northwest Greenbrier county to the lower 60s in the Piedmont.
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&& .SHORT TERM /WEDNESDAY NIGHT THROUGH FRIDAY NIGHT/...
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As of 330 PM EST Tuesday.... As a large cutoff traverses the southern plains, the ridge over the eastern US will amplify and bring quiet weather to the region through Thursday as high pressure settles over the Appalachians and central mid Atlantic. In fact, Thursday looks to offer the first good glimpse of the sun for most of the region in a few days. However, this reprieve will be short lived. By Thursday night the ridge axis will move to our east, leaving behind a lingering wedge of high pressure, and the closed low to our west becomes a progressive open wave. This will allow a surge in isentropic lift and vigorous dynamic support to accompany a frontal passage late Thursday night/early Friday with a good chance of rain. By late Friday the front any dynamic support will be pulling out of the area and bring an end to widespread precipitation. There will be no appreciable change of airmass so temperatures will remain above normal through the end of the week.
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&& .LONG TERM /SATURDAY THROUGH TUESDAY/...
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As of 330 PM EST Tuesday.... The main concern for the extended period is the potential for significant precipitation, and to a lesser extent wind, in the Sunday/Monday time frame. Guidance has been consistent with developing a full latitude trof with a deep closed low over the deep south by Sunday night. Persistent southerly flow will allow for efficient moisture transport into the region and by Monday morning, precipitable water values will be approaching 1.2 inches which is near record territory for January. At the surface, occluded low pressure will be moving up the Mississippi valley with a frontal boundary pushing in from the west. With a very moist atmosphere, strong low level flow parallel to thew baroclinic zone, and orographic effects from the Blue Ridge, guidance begins to generate substantial rainfall on Sunday with a continuation through Monday as the front moves through. These parameters are consistent with heavy precipitation events, though we are still out in the day 6/7 time frame and much of this, especially in regards to timing and placement of heavy precipitation, is subject to change with later model runs so the situation will be monitored closely. Some embedded convection is also possible especially as the front moves through Sunday night/Monday morning so this is another aspect to watch in the days ahead. Lingering wrap around precipitation will continue as the large system unwinds and pulls off to the north early next week.
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&& .AVIATION /21Z TUESDAY THROUGH SUNDAY/... As of 1245 PM EST Tuesday... Poor flying conditions this afternoon into Wednesday with rapidly changing conditions and widespread reduction with low clouds,rain and fog. MVFR ceilings with scattered IFR and LIFR in rain and fog. A cold front expected to get into the mountains this evening, and main focus for showers will be from the ROA/BCB areas west to BLF/LWB and at times LYH with DAN with lower threat. Some instability may sneak into the mountains of Southwest VA southwest of BLF this afternoon into this evening bring an isolated thunderstorm. Showers should start to taper off later this afternoon/evening in the ROA/LYH/BCB area and south, while keeping it showery into tonight at BLF/LWB per upper level support with front. Lower confidence in ceilings and visibilities overnight. At the moment expect enough wind to keep most places no worse than MVFR, except the BLF airport which is more elevated and cigs will be around 1kft. Clearing will take place behind the front on Wednesday. Conditions will become VFR Wednesday afternoon into early Thursday. Southwest winds will increase in speed this afternoon into tonight. A cold front will then cross the region tonight into early Wednesday with a turn to northwest winds. Winds will gust up to around 25 knots by Wednesday afternoon. Medium confidence in ceilings,visibilities and winds during the taf period. Extended Aviation Discussion... VFR conditions will prevail Wednesday afternoon into Thursday. However, this is expected to be short-lived per return of unsettled weather by weeks end as moisture returns from the southwest. No precipitation type issues are expected through the end of this week...just plain ole rain. However, IFR conditions may be possible in rain Thursday night into Sunday. && .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

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