Area Forecast Discussion
Issued by NWS Blacksburg, VA

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000 FXUS61 KRNK 231720 AFDRNK Area Forecast Discussion National Weather Service Blacksburg VA 1220 PM EST Thu Nov 23 2017 .SYNOPSIS... High pressure will be in control across the mid-Atlantic region through Friday before the next cold front moves through on Saturday. This will mainly be a dry frontal passage, but will bring a return of northwest breezes and cooler temperatures before high pressure builds in again for the early part of next week. && .NEAR TERM /THROUGH TONIGHT/...
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As of 1220 PM EST Thursday... Given our cooler than expected start to the day, temperatures during the day have trended a little cooler than planned. Have adjusted the forecast high temperature accordingly with values now forecast an average of two degrees cooler across the region than the prior forecast. As of 955 AM EST Thursday... The forecast update this morning will mainly reflect cosmetic changes that tweak the hourly temperature, dew point, wind, and sky cover grids to reflect the latest observations and expected trends into the early afternoon. We are still expecting plenty of sunshine today, no precipitation, light winds and slightly below normal high temperatures. Cirrus cloud cover in the far southeast is making progress out of the area, and that trend is expected to continue. As of 315 AM EST Thursday... Surface high pressure to dominate over the next 24 hrs with weak and dry upper trough to drift across the central Appalachians later today and tonight. Starting off the morning very chilly with this morning`s lows even colder then previously anticipated and have adjusted grids accordingly. Lower 20s and even some teens in the protected valleys of the mountains, with mid to upper 20s common east of the Blue Ridge as Thanksgiving Day dawns. With very light winds and mainly clear skies, with the exception of some thin cirrus initially over the Piedmont but moving east by midday, afternoon temperatures should rise quickly but will remain on the cool side of average for this time of year. Leaned toward the warmer side of guidance however, which gives upper 40s to near 50s mountains to lower 50s Piedmont. If cirrus hangs tough in the east and remains thick enough it is possible that 50 will be about as high as it can get in some spots in the east. Overall should be a very nice holiday given lots of sun, light winds, and temps only a little cooler than average as mentioned. For tonight, while the NAM hints at some mid to high clouds drifting in from the west tonight on back side of weak upper trough, most other guidance suggests mostly clear. Since clouds look pretty thin right now over Ohio Valley and if anything should trend toward dissipating as trough moves across us, thus am leaning toward the colder guidance for overnight lows tonight given nearly calm winds and mainly clear skies. Lows should still be a few degrees higher than this morning given slightly higher 850mb temps.
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&& .SHORT TERM /FRIDAY THROUGH SUNDAY/... As of 314 AM EST Thursday... Surface high pressure and a weak short wave will exit off the Mid Atlantic coast Friday afternoon. Meanwhile, a cold front over the Great Lakes will continue to track east. In between these weather features is southwesterly flow that will help afternoon temperatures warm into the mid to upper 50s. Mild conditions will continue Friday night with temperatures in the mid to upper 30s, higher elevations in the low to mid 40s. Prefrontal showers are expected to move across the mountains Saturday morning, then maybe east over the piedmont in the afternoon. Most models are not impressed with coverage of showers moving east of the Blue Ridge as low level winds become westerly rather quickly by the afternoon. The GFS is the wettest of all the models, carrying measurable precipitation across the entire area Saturday, however amounts are only a few hundreths. We took a model blend for PoPs Saturday and did not totally rule out the GFS with backing flow early. The best chance for measurable rainfall will be along western slopes of SE WV with isolated showers for the rest of the area. The front moves east of the piedmont in the evening, ending any chances for rain across most of the area. Some light upslope precipitation along western slopes are possible during the evening as the upper level trough pivots over the region. Temperatures Saturday will run warmer than normal with 50s west and low to mid 60s east. Cold air will filter in overnight, however, mixing will keep temperatures in the 30s. Pressure rises behind the front and a pressure gradient over the mountains will bring breezy and gusty conditions to the area Sunday morning. Winds will begin to relax during the afternoon as high pressure builds over the region. Models are warmer for Sunday with highs ranging from the 40s across the mountains to the 50s east into the piedmont. && .LONG TERM /SUNDAY NIGHT THROUGH WEDNESDAY/... As of 300 PM EST Wednesday... Northern stream amplifies briefly yet again later in the weekend as a short-wave tracks well to our north through southeast Canada. This will usher in another cold front through the area early Sunday, knocking back highs 10 degrees or more from Saturday, generally low 40s NW to low 50s SE. Precipitation will be hydrologically insignificant with this front with only a few upslope showers or snow flurries possible. Temps will drop off into the 20s Sunday night. This will be followed by an expansive ridge of surface high pressure for the early part of next week with temps rebounding upward roughly 5 degrees Monday- Tuesday. The only hint of possible precipitation at this point appears to be Wednesday as another front approaches, but this too looks quite moisture-starved. No end in sight for what is turning into a very dry month of November. && .AVIATION /17Z THURSDAY THROUGH MONDAY/...
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As of 1210 PM EST Thursday... High pressure will provide for VFR conditions and light winds during the extent 24 hour valid TAF period concluding at 18Z/1PM Friday. The exception to the rule will be some very patchy MVFR fog across parts of the area for a few hours late tonight into early Friday morning. Extended Discussion... Primarily VFR conditions will prevail through at least Friday night. On Saturday a cold front will cross the area. It will be moisture starved for the most part, with at best some isolated showers across the area and some patchy of MVFR ceilings, with the greatest potential across southeast West Virginia, south into the Northern Mountains of North Carolina. High pressure regains control of our weather pattern Sunday into Monday with a return to VFR for the entire region. Gusty winds are expected Saturday into Saturday night in the wake of the cold front passage. Surface gusts of 15 to 25 mph will be possible at the higher elevations.
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&& .RNK WATCHES/WARNINGS/ADVISORIES... VA...None. NC...None. WV...None. && $$ SYNOPSIS...SK NEAR TERM...DS/SK SHORT TERM...RCS LONG TERM...PC AVIATION...DS

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