Area Forecast Discussion
Issued by NWS Blacksburg, VA

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000 FXUS61 KRNK 231144 AFDRNK Area Forecast Discussion National Weather Service Blacksburg VA 644 AM 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/... 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. && .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 /12Z THURSDAY THROUGH MONDAY/...
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As of 644 AM EST Thursday... High pressure across the eastern part of the country will dominate through the valid TAF period and into the day Friday. This will bring light westerly winds and fair weather with VFR conditions all TAF sites through Friday. Cirrus associated with southern stream energy will shift east and out of the southeast part of the forecast area by midday today. Satellite imagery early this morning shows very isolated river valley fog in parts of southeast WV but is not expected to impact any TAF sites this morning including LWB. Fog development is not anticipated tonight either. Winds at TAF sites today are expected to remain at or below 4 kts and will be variable, but with a tendency to be more out of the west or southwest in the mountains and more out of the south in the Piedmont. High confidence in ceilings and visibilities through the TAF valid period. Medium to high confidence in wind direction, high confidence in wind speed through the TAF valid period. Extended Discussion... The next cold front with a potential for sub-VFR conditions, mainly in the west, will cross the area on Saturday. There is very little moisture with this front and while a few light showers or sprinkles are possible in the mountains on Saturday there will be more impact from gusty winds just behind the front later Saturday and into Sunday. Anticipate gusty winds Saturday into Sunday in the 15 to 25 mph range for most areas, higher gusts at higher elevations. Some MVFR ceilings are also possible on the west side of the Appalachians Saturday into Sunday, but at this point IFR conditions look unlikely. We should have more confidence in potential MVFR or IFR ceilings behind this front by Friday. High pressure returns on Monday with weaker winds, and no precipitation forecast.
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&& .RNK WATCHES/WARNINGS/ADVISORIES... VA...None. NC...None. WV...None. && $$ SYNOPSIS...SK NEAR TERM...SK SHORT TERM...RCS LONG TERM...PC AVIATION...RAB/SK

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