Area Forecast Discussion
Issued by NWS Blacksburg, VA

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000 FXUS61 KRNK 240523 AFDRNK Area Forecast Discussion National Weather Service Blacksburg VA 1223 AM EST Fri Nov 24 2017 .SYNOPSIS... High pressure will continue to control our weather pattern through Friday. A cold front will cross the area this weekend, with only isolated showers expected. High pressure rebuilds over the area by early next week and remains through the middle of the week. && .NEAR TERM /THROUGH TONIGHT/...
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As of 1215 AM EST Friday... Adjusted temperatures down somewhat in most areas, on average 2-3 degrees F. Do not expect it to be as cold as last night as 850mb temps have warmed slightly, but radiational cooling is excellent in the dry air. All other grids are in good shape at this time. As of 650 PM EST Thursday... No significant changes needed the the grids at this time. Will need a bit more time to see how the min temperature is tracking for tonight. Suspicious that the dewpoint at KBLF is too low, but otherwise grids are in good shape. Made only minor adjustments to T, Td, and Sky grids. As of 200 PM EST Thursday... A ridge of high pressure was oriented from eastern Texas, northeast to Pennsylvania. Aloft, a shortwave trough was heading eastward through the Great Lakes region, and low pressure was centered near Jacksonville, FL. Tonight into Friday, the Florida low pressure is expected to progress northeast around 100 miles off the coast of the Carolinas. Any associated precipitation is progged to remain well southeast of the forecast area. The shortwave trough moving the Great Lakes region will progress into and east of New England, with its associated precipitation staying well north of the area. At best, the area may see an increase in some thin high level cloud cove by this time tomorrow. At the surface, high pressure will remain over the area, with its axis shifting east of the region by Friday afternoon. This will result in light and variable or calm winds tonight through Friday morning. By Friday afternoon, a prevailing weak south wind is expected. Low temperatures tonight will be on the cold side. Will continue to favor values below the coldest guidance. Anticipate low to mid 20s across the mountains with primarily mid 20s across the Piedmont. On Friday, as geopotential heights rise and likewise with 850mb temperatures, high temperatures are expected to be some 5 to 10 degrees warmer than those realized today. Expect low to mid 50s across the mountains with mid to upper 50s across the Piedmont.
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&& .SHORT TERM /SATURDAY THROUGH SUNDAY NIGHT/... As of 110 PM EDT Thursday... Cold front by Saturday morning will extend from Ontario to northern Texas. Models similar with the timing of the front. Deeper moisture along and just behind the front clears east out of the piedmont by late Saturday evening. Upslope winds will prolong cloud cover on the western slopes of the Appalachains until Sunday morning. May increase wind speeds at higher elevations behind the front Saturday and Saturday night to account for low level jet, cold air advection and modest pressure rises. Warm air advection and increasing cloud cover Friday night will limit drop in temperatures. By Sunday morning 850mb temperatures back below zero over the mountains. Will lean toward cooler guidance with high overhead on Monday morning. && .LONG TERM /MONDAY THROUGH THURSDAY/... As of 110 PM EDT Thursday... Split flow pattern remains through Day 7, Thursday. Upper long wave trough will dig into the western United States Monday and Tuesday with a strong short wave separating from the southern end of the trough over the southeast United States on Wednesday. As typical, GFS is faster with this feature. Prefer the timing of the ECMWF which brings the short wave across the Mid Atlantic region on Thursday. Expecting dry weather and seasonal temperatures MOnday through Wednesday, then a chance of precipitation and cooler temperatures Thursday. At the surface a northern stream cold front will cross the area on Wednesday, then low pressure associated with the southern stream short wave tracks into the Tennessee Valley on Thursday. Will be slowing down better probability of precipitation until Thursday. && .AVIATION /06Z FRIDAY THROUGH TUESDAY/...
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As of 1215 AM EST Friday... A progressive semi-zonal flow will remain in place across the U.S. with a series of dry northwest flow short waves. The northern stream will continue to dominate the Mid-Atlantic region with a dry west-northwest to northwest flow aloft. A series of mainly dry upper troughs and associated cold front will continue to pass through the area every few days with little or no moisture return in advance of these systems. Thus, a dry/VFR forecast will remain in place through this TAF valid period and beyond. Still feel that the air mass overnight will be too dry for any radiational fog development, although it cannot be 100% ruled out in favorable locations. Weak high pressure will provide mostly calm winds overnight, trending toward the SSE-SSW Friday afternoon as the high slides to the east of the area. Speeds will remain mostly 5kts or less through the TAF valid period. High confidence in ceilings and visibilities through the TAF valid period. Medium confidence in wind direction, high confidence in wind speed through the TAF valid period. Extended Discussion... 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...DS NEAR TERM...DS/RAB SHORT TERM...AMS LONG TERM...AMS AVIATION...DS/RAB

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