Area Forecast Discussion
Issued by NWS Blacksburg, VA

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016 FXUS61 KRNK 221737 AFDRNK Area Forecast Discussion National Weather Service Blacksburg VA 1237 PM 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 1005 AM EST Wednesday... Band of rain lined up from the Tennessee Valley into Virginia this morning sets up well with the latest RAP13 and HRRR. As such adjusted pops a little higher in the southwest Virginia area, northeastward toward Lynchburg, VA. As we head into the afternoon, models showing less convergence in the piedmont so expect less coverage of rain, while the mountains, especially south of I-81 into the NC mountains stay more in the rain, eventually becoming less numerous after 3pm. Temperatures running about 2-5 degrees cooler than previous forecast. Not expecting any sunshine today, and think temps will be cooler, so adjusted down the highs about 1-3 degrees. Still for late February will be running about 5 to 10 degrees above normal. Previous discussion from early morning... 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 /18Z WEDNESDAY THROUGH MONDAY/...
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As of 1225 PM EST Wednesday... Been dealing with variably changing aviation categories, with in-situ wedge in place along with patchy rain/drizzle and fog. At this forecast, the confidence stays below medium on the ever changing cigs. Am confident enough over the eastern taf sites including BCB/ROA to bring cigs to MVFR to low end VFR at times through this evening, with vsbys staying mainly 3sm or higher with rain. Further west will see MVFR for most of the afternoon, though some breaks in the low clouds occurs enough to have VFR at times. As we head through the overnight, model forecast soundings suggest fog and/or low cigs. Will hit the fog harder in the east with IFR occurring after 06z, with MVFR cigs. Across the mountains will go more IFR cigs and vsbys. Even LIFR fog/stratus may occur late in the BCB-BLF-LWB area. The shallow stable layer erodes as we head past 12-14z, such that cigs/vsbys should improve, especially east of the mountains. Some slower improvement at LWB so keeping them MVFR between 15-18z Thu. Extended Aviation Discussion... Thursday afternoon should see mainly VFR except possible MVFR at BLF/LWB as showers approach. Thursday night-Friday, we will be well into the warm sector with VFR conditions and much above normal temperatures. Surface wind gusts of 20 to 30 kts possible across the higher terrain. Band of showers and isolated thunderstorms with MVFR conditions arrive late Friday night into early Saturday along and ahead of a strong cold front. Drier weather and increasing northwest winds follow behind the front on Saturday afternoon through Sunday. Approach of another front Monday will provide increasing clouds and possibly showers and MVFR cigs to BLF/LWB late in the day.
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&& .RNK WATCHES/WARNINGS/ADVISORIES... VA...None. NC...None. WV...None. && $$ SYNOPSIS...AMS NEAR TERM...AMS/WP SHORT TERM...KK LONG TERM...DS/KK AVIATION...AMS/WP

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