Area Forecast Discussion
Issued by NWS Blacksburg, VA

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000 FXUS61 KRNK 130522 AFDRNK Area Forecast Discussion National Weather Service Blacksburg VA 122 AM EDT Fri Oct 13 2017 .SYNOPSIS...
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High pressure will continue to wedge south along the lee of the Appalachians overnight through Friday night. A cold front will approach the area this weekend, and finally cross the region Sunday night into Monday. High pressure will build over the area for the early to middle part of next week.
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&& .NEAR TERM /THROUGH TODAY/... As of 711 PM EDT Thursday...Wedge continues to remain entrenched over much of the forecast area, with related low overcast skies and east-northeasterly flow plaguing many areas. Forecast appears on track with little changes made. I did include a greater extent of patchy fog, though it is meant to convey more misty conditions with damp conditions and surface-5000 ft AGL RH remaining fully saturated. Blended in current observations and lower hourly temperatures by about 2-4 degrees through late evening, though mostly a cosmetic change. Gradual, slow cooling trend in temps looks on track for the overnight as cold thermal advection begins. Pretty gloomy, gray conditions for tonight expected. Previous near-term discussion issued at 200 Lee side wedge, cold air damming, scenario is setting up nicely across the area. Plenty of cloud cover continues to lower in altitude and drizzle/light rain is slowly expanding in coverage. This trend is expected to continue through the overnight hours, along with fog development, with the area along and near the crest of the Blue Ridge to focus for the best chance of measurable rainfall. The area along and west of a line from Bluefield, WV to Marion, VA will be on the edge, or just west of, the western extent of the wedge, and as such, will have the best chance tonight into Friday for the least amount of cloud cover, and thus, warmest temperatures across the area on Friday. On Friday, expect limited change in the weather pattern with few locations east of the crest of the Blue ridge experiencing more than a 10 degree climb in temperatures as compared to the morning low temperatures. Diurnal temperature ranges will be a little be only slightly higher across the mountains. As mentioned above, the far western sections will have the greatest temperature increases thanks to less cloud cover and limited, or no, influence of the wedge. && .SHORT TERM /TONIGHT THROUGH SUNDAY NIGHT/... As of 240 PM EDT Thursday... Wedge of high pressure will be situated over the forecast area Friday night and will continue to see isolated showers and patchy drizzle in the wedge along with fog. Low temperatures will be in the mid to upper 50s. Saturday the high moves further offshore with a weakening of the shallow cool air. Will notice increasing sunshine as winds slowly turn more toward the southeast to south, though clouds may linger longer in the piedmont north of Danville/South Boston. Highs will be in the mid to upper 70s, except lower 70s in the higher ridges. Saturday night into Sunday will be warm ahead of a cold front which models have trended a little faster. Should be a little milder Sat night with lows in the mid 50s to around 60. Front will be situated from the Ohio Valley southwest into the mid MS Valley. Mid level flow will be more wsw which will lead to less threat of showers Sunday afternoon, with isolated threat in the mountains, making it to the foothills/piedmont by dusk. Sunday looks like the warmest day for the next 7 days with highs in the mid 70s to near 80 west, to lower 80s east. Front slides to the east by late Sunday night and it looks like a situation where showers affect the mountains, jump the Blue Ridge and impact the piedmont where a lower threat occurs in the New River/Roanoke Valley. && .LONG TERM /MONDAY THROUGH THURSDAY/... As of 240 PM EDT Thursday... With trends to faster solution will dry things out a quicker, but will hang onto low chance pops over the NC foothills/southside VA corridor Monday. Cooler high pressure builds in Monday night and sets up residence into Thursday though temps will start to modify a little by midweek, but still at or just above seasonal norms. && .AVIATION /05Z FRIDAY THROUGH TUESDAY/...
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As of 110 AM EDT Friday... Poor flying conditions under MVFR to IFR cigs and ocnl MVFR vsbys will persist overnight through much of Friday. 700-1500 foot bases should be common with periods of lower cigs within areas of light rain/drizzle including mountain obscuration. May also see periods of 1-4SM in rain/drizzle and/or fog during the overnight as well. Any light rain/drizzle/fog should thin out by mid- morning Friday, though MVFR to IFR ceilings to remain with no meaningful change except perhaps seeing cigs approach VFR at times along the KBLF- KLWB corridor Friday afternoon as the western periphery of the wedge weakens a bit. Northeast winds 5-15 kts through the TAF period. Wedge to linger Friday night with any improvement in cigs during Friday likely to give way to more low end sub-VFR with loss of heating as the cool air wedge enhances again overnight. Extended Aviation Discussion... Saturday, the lee side wedge will give way to increasing southwest flow ahead of our next synoptic scale upper trough and associated cold front. This will allow for more areas to experience VFR conditions, a trend that will continue into Sunday. Sunday night into Monday, a substantial cold front is expected to cross the area with scattered showers and some storms. Sub- VFR conditions are expected to accompany the stronger showers/storms. Also, in the wake of the cold front, lingering moisture in the west will likely manifest as some upslope sub- VFR ceilings Sunday night into Monday morning. High pressure will continue to build into the area on Tuesday. Other than some early morning patchy mountain and river valley fog, VFR conditions are expected.
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&& .RNK WATCHES/WARNINGS/ADVISORIES... VA...None. NC...None. WV...None. && $$ SYNOPSIS...JH/DS NEAR TERM...AL/DS SHORT TERM...WP LONG TERM...WP AVIATION...AL/DS/JH

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