Area Forecast Discussion
Issued by NWS Blacksburg, VA

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000 FXUS61 KRNK 221026 AFDRNK Area Forecast Discussion National Weather Service Blacksburg VA 526 AM EST Wed Feb 22 2017 .SYNOPSIS... Low pressure over the northern plains this morning will east across the Great Lakes into New England through Thursday while a low over the Gulf of Mexico will move across Florida. A strong low forming in the central plains tonight and Thursday will move northeast through the end of the week, pushing a warm front into the Ohio Valley by Friday and an intense cold front across the eastern United States on Saturday. High pressure will follow the cold front for Sunday and Monday. && .NEAR TERM /THROUGH TONIGHT/... As of 450 AM EST Wednesday... Area radars showed a band of rain from northern Virginia into south central Kentucky early this morning. This band will move slowly southeast today with the southern edge reaching the Virginia/North Carolina border by 21Z/4PM. some isentropic lift and a weak short wave will also generate light rain from the southern Appalachians into the foothills of Virginia. Have increased the probability of precipitation across the region today. Also expecting fog along the Blue Ridge and into the eastern foothills tonight and cloud bases lower. At the surface a low over the northern Gulf of Mexico will track across the Gulf then southern Florida today and tonight. This will keep the best inflow of moisture off the Atlantic from North Carolina to Georgia. Models still showed light southeast wind from the surface through roughly 900MB but as a weak high forms over the Mid Atlantic region tonight wind speeds stay light. But enough easterly component to the surface and low level winds plus light precipitation to develop a shallow in-situ wedge today. Have trimmed maximum temperatures up to 5 degrees today, staying below guidance at some locations, since little to no sunshine expected. Coverage of precipitation will diminish tonight but clouds and fog will remain. Stayed close to cooler guidance for overnight lows. && .SHORT TERM /THURSDAY THROUGH FRIDAY NIGHT/... As of 350 AM EST Wednesday... High pressure off the North Carolina coast will continue to move east into the Atlantic ocean through Friday night. The general prevailing flow across much of the region will be south to southwest on the west side of this high. An upper level disturbance will move northeast out of the Ohio valley and reach New England by Thursday night. Low level moisture will advect into our area and result in plenty of clouds and patchy light rain in areas primarily along the crest of the Blue Ridge. A warm front will lift north across the region Thursday into Thursday night. This will create scattered showers Thursday afternoon into Thursday night. There is enough surface based instability as seen in forecasted Lifted index to support some isolated thunderstorms across parts of southeast West Virginia, south into the Northern Mountains of North Carolina. High temperatures on Thursday will range from the upper 50s n the mountains to the lower 70s in the Piedmont. Expect some patchy precipitation associated with the front Thursday evening into Thursday night. Then, by early Friday morning, we expect only some limited light rain near the crest of the Blue Ridge as southerly flow yield some light upslope precipitation in this area. Low temperature Thursday night will vary from the mid 40s in the mountains to the lower 50s in the Piedmont. Despite considerable clouds on Friday, it will be mild with readings from the mid 60s in the mountains to the mid 70s in the Piedmont. Elected to keep isolated showers along the Blue Ridge mountains Friday. For Friday night, a strong cold front will approach the area from the west. Timing of front looked a little slower on this morning 00z run vs the 12z run. Very strong southerly winds are progged to increase in advance of this cold front. The potential for showers will be on the increase through the night, especially across western sections of the region. There appears to be enough instability for isolated to scattered thunderstorms in the west. The Day 3 convective outlook has highlighted a thunderstorm potential into western portions of forecast area. Low temperatures Friday night will range from the mid 40s in the mountains to the mid 50s in the piedmont. && .LONG TERM /SATURDAY THROUGH TUESDAY/... As of 350 AM EST Wednesday... A strong cold front will cross the area on Saturday. Anticipate a distinct line or area of showers to cross the region during the course of the day, with coverage greatest across the northern third of the region. Surface based instability may be great enough in the afternoon for some isolated thunderstorms generally along and east of a line from Danbury, NC to Bedford, VA. Colder air will move into the area Saturday night. Gusty northwest flow behind the cold front will help maintain isolated showers across parts of southeast West Virginia that will transition to isolated snow showers by late Saturday night. For Sunday, our pattern transition to zonal flow aloft with surface high pressure providing dry weather to the region. The GFS is more robust with upslope for Saturday night into Sunday, while ECMWF is drier with high pressure building in. Will hold on to continuity with snow showers Saturday night, followed by high pressure on Sunday. Sunday night into Monday, a weak disturbance within this flow is expected to bring isolated to scattered showers to the far western parts of the area. Monday night into Tuesday, southwest flow increases across the area in advance of a developing upper level trough. Look for a warm front to develop over the region and move northward. Anticipate cloud cover and patchy light rain to develop across the region, and be concentrated the greatest across the northern sections of the area, nearest the warm front. Wednesday looked unsettled with scattered showers continuing into Wednesday night. Temperatures will still be some ten to twenty degrees above normal on Saturday, but trend to near normal by Sunday behind the cold front. Temperatures will slowly moderate Monday into Wednesday to reading about ten degrees above normal. && .AVIATION /10Z WEDNESDAY THROUGH SUNDAY/... As of 100AM EST Wednesday... High confidence in TAFs trending to IFR through the first part of the valid period and remaining IFR through the remainder of the period. A wedge of high pressure will linger over the region through Wednesday with weak isentropic lift and some short wave energy running over the top of the wedge. This will lead to lowering of clouds with showers gradually spreading across TAF sites from southwest to northeast after 08Z/2AM. Lowest IFR cigs will set in by daybreak but may trend upward by the end of the period. Best chances for precipitation will be through mid morning but low visibilities in drizzle and fog will linger into the afternoon. Winds will be light through the period. Extended Aviation Discussion... Significant improvement does not appear likely until the evening. As a warm front returns northward on Thursday, an eventual redevelopment of light showers is possible with likely MVFR conditions Thursday evening through Friday. Area will slide in between weak low pressure off the southeast coast Friday and the next stronger upstream cold front that looks to arrive by midday Saturday. This should allow for some improvement in cigs/vsbys within the warm sector Friday as the low level jet increases. Expect a mix of MVFR and low end VFR ceilings and mainly VFR visibilities during the day with surface wind gusts of 20 to 30 kts possible across the higher terrain. Band of showers including a period of sub-VFR to arrive late Friday night into early Saturday with the front, followed by drier weather and increasing northwest winds by afternoon behind the boundary. && .RNK WATCHES/WARNINGS/ADVISORIES... VA...None. NC...None. WV...None. && $$ SYNOPSIS...AMS NEAR TERM...AMS SHORT TERM...KK LONG TERM...DS/KK AVIATION...AMS is the U.S. government's official web portal to all federal, state and local government web resources and services.