Area Forecast Discussion
Issued by NWS Blacksburg, VA

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000 FXUS61 KRNK 150548 AFDRNK Area Forecast Discussion National Weather Service Blacksburg VA 148 AM EDT Sun Oct 15 2017 .SYNOPSIS... High pressure will remain over the region tonight through Sunday morning. Low pressure developing in the central Rockies tonight will track northeast and push a strong cold front through the area Sunday night. High pressure follows the front for the rest of the week. && .NEAR TERM /THROUGH TODAY/... As of 700 PM EDT Saturday... Limited changes will be made to the forecast heading through the early tonight period of the forecast. Other than some scattered cloud cover along and near the crest of the Blue Ridge from roughly Roanoke, VA southwest into the Northern Mountains of North Carolina, most locations were experiencing clear skies. This is still expected to change as we progress through the night, especially after midnight, with the development of some stratus cloud cover mainly in areas near and east of the crest of the Blue Ridge. As of 300 PM EDT Saturday... Low clouds eroded across most of the forecast area this afternoon as high pressure built across the region. The light northwest 850 MB winds should clear out the remain low clouds along the southern Blue Ridge. The combination of light winds and low level moisture will result in the development of low clouds and fog. NAMNest and ensemble guidance suggest a layer of status will likely develop in the foothills and piedmont late tonight into Sunday morning. Valley fog will form once again especially in the west. Low temperatures will vary from the lower 50s in the mountains to around 60 degrees in the Piedmont. Upper trough over the central Rockies will travel northeast across the Great Lakes region and southeast Canada Sunday. A cold front trailing south from the low will push into the area late Sunday, and move across the region Sunday night. Slowed downed the timing of the convection along the Frontal boundary Sunday morning. High temperatures Sunday afternoon will range from around 70 degrees in the northwest mountains to the lower 80s in the piedmont. && .SHORT TERM /TONIGHT THROUGH TUESDAY NIGHT/... As of 330 PM EDT Saturday... Cold front and upper trough will move through the forecast area overnight into early Monday. As expected, with downsloping and diminishing upper support, precipitation will decrease as it crosses the Alleghanys. Some brief redevelopment of precipitation may occur may occur across the Piedmont during the evening/overnight areas, but likely pops do not appear warranted much beyond the Alleghany Front, so will just go with chance pops. QPF will range from 1/4 inch west to less than 1/10 inch east of the Blue Ridge. So, in essence, while everyone should get a little rain, amounts are expected to be negligible and mostly confined to the western areas, where 1/4 inch is possible. Will not include any thunder as all instability is expended well west of our area during the evening. Once the front moves east of the area, high pressure, both at the surface and aloft, will build over the area for the remainder of the week ensuring a dry forecast. The cool down will be the big story during this period, especially considering the belated summer weather in recent weeks. 850mb temperatures will bottom out near 0C in the northern areas Monday to around +5C in the south, then begin to slowly moderate back toward +10C mid week. Monday morning clouds and precipitation will still be in the area, so the main cold advection will arrive Monday night/early Tuesday. Have included frost in the colder valleys, but some concern about how much wind there may be yet at that point. However, the surface high center will be near CRW, so feel that frost in the decoupled valleys along with moist ground from recent rainfall, should support frost. Later shifts may need to consider adding a Frost Advisory as we get closer to that time frame. Frost will also be possible in the sheltered, protected valleys again Tuesday night/Wednesday morning, but overall coverage will be less than what is expected Tuesday morning. Some gusty winds will be noted behind the front, but at this point it appears to fall well below wind advisory criteria. Temperatures will average 5-10 degrees below normal at the beginning of the period to near normal by the end, but certainly the coolest so far of the fall season. && .LONG TERM /WEDNESDAY THROUGH SATURDAY/... As of 350 PM EDT Friday... High pressure at the surface and aloft will remain in place and amplify over the Mid-Atlantic region through the extended period. A very dry airmass will reside over the area through the entire period providing clear/sunny skies. 850mb temperatures will slowly moderate as a 590dm ridge builds over the area aloft. Temperatures will moderate well back into the 70s by then end of the extended period, even approaching 80 degrees in the Piedmont. No rain is expected at all during this period, so have left all pops for all areas at zero! && .AVIATION /06Z SUNDAY THROUGH THURSDAY/...
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As of 140 AM EDT Sunday... IFR to LIFR stratus was expanding across the foothills and piedmont of Virginia and North Carolina early this morning. High confidence that the clouds will reach KLYH and KDAN before 09Z/5AM. Patchy fog was developing in locations with a clear sky. Medium confidence that the visibility will drop to LIFR at KLWB and KBCB before 09Z/5AM. At KDAN the visibility was less than one mile but this could improve once the more extensive cloud cover arrives. Layer of moisture is near the surface and less than 1500 feet thick according to BUFKIT forecast soundings. Clouds and fog will dissipate quickly after sunrise. VFR conditions are expected for the rest of the day. A cold front will approach the area Sunday evening. Have held off on any precipitation in the TAFs expect for KBLF with showers reaching airport after 02Z/10PM. Extended Aviation Discussion... The front will move southeast through the Mid Atlantic region before Monday morning with showers and MVFR/IFR ceilings. The cold front should head offshore on Monday night, which will allow conditions to improve to VFR by Tuesday. High pressure will return to provide good flying weather through Friday.
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&& .RNK WATCHES/WARNINGS/ADVISORIES... VA...None. NC...None. WV...None. && $$ SYNOPSIS...AMS/KK NEAR TERM...DS/KK SHORT TERM...RAB LONG TERM...RAB AVIATION...AMS/DS

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