Area Forecast Discussion
Issued by NWS Blacksburg, VA

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000 FXUS61 KRNK 250528 AFDRNK Area Forecast Discussion National Weather Service Blacksburg VA 1228 AM EST Sat Nov 25 2017 .SYNOPSIS... High pressure across our region overnight will briefly yield to a cold front that will arrive on Saturday. High pressure quickly regains control over our weather pattern for much of next week. The potential exists for a cold front to cross the area on Friday. && .NEAR TERM /THROUGH TODAY/... As of 1113 PM EST Friday... Radiational cooling across Piedmont and mountain valleys with relative lack of cloud cover is effective so far this evening and in many locations temps are already dropping below forecast lows, while ridges remain warm. Ridges and some locations in the west may remain steady or even rise some while most other locations should continue to cool at least for most of the night. Tried to account for this in a forecast update mainly for temperature tonight. Previous valid discussion as of 930 PM EST Friday... Few changes required to the existing forecast package as conditions remain tranquil and trends are tracking close to the forecast, albeit with the typical wide local variations in temperature under a radiational environment. Previous valid discussion... As of 930 PM EST Friday... A ridge of high pressure was centered along a line from Louisiana to Deleware. Low pressure was positioned east of Florida. A cold front extended southwest from a low in southern Ontario through Minnesota and South Dakota. A developing surface trough was in advance of the cold front, across Nebraska south into Texas. Over the course of the next 24 hours, the surface ridge of our region will be shunted to the east in advance of the approaching High Plains cold front. The front itself will arrive and cross our region during the day Saturday. We are expecting dry weather to continue across the entire region through tonight. On Saturday, isolated showers will be possible in the afternoon and early evening in association with the cold front, but only across portions of southeast West Virginia, south into the northern mountains of North Carolina. The remainder of the region will remain dry. Cloud cover will be on the increase overnight, especially west of the crest of the Blue Ridge, with the remainder of the region experiencing and increase in cloud cover as Saturday progresses. As the associated upper trough draws closer and the center of the ridge axis moves eastward, look for an increase in winds across the area. Stronger winds will first be noted tonight at the higher elevations across the mountains. Within the mountain valleys and across the Piedmont, the influence of the nocturnal inversion will hinder any notable increase in wind. Anticipate the Piedmont and mountain valley regions to experience a fairly normal decreasing trend in temperatures as the night progresses. However, at the higher elevations, the influence of the stronger winds and warm air advection will yield steady or slowly rising temperatures during the night. Lows tonight will range from mid 30s to mid 40s across the mountains depending up elevation. Across the Piedmont, the middle 30s are expected. On Saturday, all parts of the region will be milder than readings realized today, especially across the Piedmont where clouds will arrive later in the day. Highs will range from the low to mid 50s across the mountains with readings around 60 to the mid 60s across the Piedmont. && .SHORT TERM /TONIGHT THROUGH MONDAY NIGHT/... As of 110 PM EDT Friday... Saturday evening deeper moisture associated with the front will be moving east out of the Virginia and North Carolina piedmont. Low level upslope clouds will already be developing on the western slopes of the Appalachians. Expect these clouds to remain over southeast West Virginia through Sunday morning. Enough of a low level jet from the northwest behind the front to support some gusty winds, especially at higher elevations Saturday night and Sunday. Surface high pressure centered over western Virginia and western North Carolina Monday morning. Conditions will be favorable for winds to decouple Sunday evening and to have cooler minimums in the valleys overnight. Warm front crossing the Ohio Valley on Monday night may spread some high clouds into West Virginia and the northern half of Virginia. This should have little impact on minimum temperatures. Staying at or below guidance for lows both Saturday night and Sunday night. && .LONG TERM /TUESDAY THROUGH FRIDAY/... As of 110 PM EDT Friday... Operational ECMWF and GFS and the ensembles were in fairly good agreement with the overall pattern Tuesday and Wednesday. Pattern remains progressive and weak upper ridging moves across the central and eastern United States. Seeing typical bias with the slower ECMWF and faster GFS with a closed low that moves out of the Pacific and into the southwest United States by Tuesday. Bases more on the ECMWF timing this feature will reach the Mid Atlantic region around Thursday. Bigger spread in the guidance for the timing and location of synoptic features on Thursday and Friday. Warm air advection and west surface to low level wind on Tuesday so maximum temperatures will be near or slightly above normal depending on cloud cover. && .AVIATION /05Z SATURDAY THROUGH WEDNESDAY/...
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As of 1230 AM EST Saturday... VFR conditions with just high clouds all sites through this morning. A weak cold front will move through the region late today. A sprinkle is not out of the question at BLF and LWB with upslope just behind the front this afternoon into tonight, with at least a brief period of MVFR ceilings most likely at BLF. All other TAF sites will remain VFR and dry. Primary impact of this front will be to increase west to northwest winds behind it with gusts 15-20 kts and even higher over ridges. These winds will slowly begin to weaken overnight. Extended Discussion... VFR conditions continue into much of next week with high pressure building back in from Sunday through mid week. The next potential chance for sub-VFR conditions is not until late Thursday at the earliest.
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&& .RNK WATCHES/WARNINGS/ADVISORIES... VA...None. NC...None. WV...None. && $$ SYNOPSIS...DS NEAR TERM...DS/PC/SK SHORT TERM...AMS LONG TERM...AMS AVIATION...DS/MBS/SK is the U.S. government's official web portal to all federal, state and local government web resources and services.