Area Forecast Discussion
Issued by NWS Blacksburg, VA

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000 FXUS61 KRNK 152014 AFDRNK Area Forecast Discussion National Weather Service Blacksburg VA 314 PM EST Wed Feb 15 2017 .SYNOPSIS...
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A cold front will continue to progress from the Blue Ridge eastward into eastern Virginia and North Carolina early tonight, with high pressure building in behind the front. Gusty northwest winds are expected for areas from the Blue Ridge westward tonight into Thursday, with the strongest winds expected along the southern end of the Blue Ridge into the North Carolina mountains. A period of brief upslope snow showers are also possible in the favored upslope areas in southeastern West Virginia. The shot of cooler air is brief and temperatures again begin to rebound on Friday ahead of the next storm system for the latter part of the weekend.
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&& .NEAR TERM /THROUGH THURSDAY/...
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As of 313 PM EST Tuesday...Cold front extending along the Blue Ridge continues to advance eastward this afternoon. Its main notable affect is a sharp drying in surface dewpoints and a wind shift to northwest. 500 mb cyclonic gyre associate with phased northern and southern streams remains in place across most of the Northeast, mid-Atlantic into the central Appalachians. For Tonight: As high pressure ridge is building into the region, an increase in northwesterly wind gusts already evident mainly for areas along/west of the Blue Ridge. These wind gusts should only continue to increase as the evening progresses. Compared to prior post frontal wind events, 6-hourly pressure rises are not particularly strong (around 4-5 mb), low-level inversion heights are fairly high and 850 mb winds are only in the 45 kt neighborhood off the 12z GFS. After collaboration with surrounding offices and with winds already having started to increase, opted to issue a Special Weather Statement for sub- Advisory winds for locales along and west of the Blue Ridge through 15z. General expectation is for wind gusts to 45 mph - and may at times approach Advisory criteria - for the southern Blue Ridge tier of counties (Watauga/Ashe/Alleghany NC up through Roanoke VA), with peak gusts to 40 mph for the rest of the area. The peak winds should occur roughly at two points: one later tonight accompanying the strongest pressure rise, and again into the mid-morning due to mixing. Increasing low-level moisture plunging southward from the Great Lakes as seen on visible imagery should allow for variable cloud cover and chances for snow showers primarily for western Greenbrier County. However the best moisture still is further to the north, and so I`ve shown forecast snow amounts to be an inch or less. While conditions for the Virginia/North Carolina foothills and Piedmont areas are locally milder in the upper 20s, it stands to be rather chilly tonight along/west of the Blue Ridge where lows are projected to drop into the upper teens to mid 20s. Given that winds will be higher in these western areas, wind chills in the upper single digits to low teens are anticipated by early morning. For Thursday: High pressure remains in control with 1000-500 mb thermal trough overhead. Pertaining to winds, since low-level wind fields trend lower as we progress into the afternoon, wind gust magnitudes should begin to lower in turn during late morning into the afternoon hours. However it still will be rather blustery due to mixing. Guidance suggests that we`ll still have some leftover upslope cloudiness but that snow showers do begin to taper off by mid-morning. Temperatures west of the Blue Ridge/NC mtns are expected to be very slow to rise (highs only mid/upper 30s to near 40), with downsloping aiding to push highs into the mid/upper 40s along and east of the Blue Ridge into the Piedmont.
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&& .SHORT TERM /THURSDAY NIGHT THROUGH SATURDAY NIGHT/...
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As of 313 PM EST Wednesday... In a progressive split flow regime, we will transition from being under the influence of a northern stream trof to a southern stream ridge as we head into the weekend. This will bring warmer temperatures and generally quiet weather through Saturday. Surface high pressure will slide off to our east Thursday night and push a warm front through the region as a nice pulse of short wave energy swings through aloft. While there is a good amount of associated moisture and isentropic lift, it looks like any flurries Thursday night into Friday morning will remain off to our north. Ridging aloft will support a weak high pressure at the surface with dry weather through most of Saturday. However, the ridge axis will move east of the region later on Saturday and allow an approaching upper trof with a weak surface low reflection off the coast to bring a chance of showers back to the forecast for late Saturday into Saturday night. Temperatures will trend from above normal to much above normal as highs on Saturday reach the mid to upper 60s east of the Blue Ridge, with mid 50s to around 60 degrees more common to the west.
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&& .LONG TERM /SUNDAY THROUGH WEDNESDAY/...
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As of 313 PM EST Wednesday... We will continue to reside in the southern stream of a progressive split flow regime through the first part of next week with temperatures well above normal. Lingering effects from a departing upper trof will keep a chance of rain showers west of the Blue Ridge through Sunday. Ridging aloft and high pressure at the surface will then bring dry weather into Tuesday. However, the ridge will start to flatten and may allow a low moving through the Great Lakes region to push a front into the region with a few showers possible mainly across the Alleghany Highlands into southeast West Virginia. Guidance solutions then start to diverge for midweek in handling development of a southern stream closed low along the Gulf coast and potential for wedge pushing down with a backdoor front on Wednesday. Believe a blended approach is the best course of action and will indicate a slight chance/chance for showers to cover the situation Wednesday.
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&& .AVIATION /20Z WEDNESDAY THROUGH MONDAY/... As of 1241 PM EST Wednesday... Generally SCT-OVC VFR stratocu through 00z as a dry cold front advances southeastward, with a wind shift to northwest 10-12 kts gusts to 25 kts accompanying the frontal passage. While skies clear early this evening for most of the TAFs, expect a lowering to MVFR around/after 02z as moisture from the Great Lakes is forced upslope, predominantly affecting BLF and LWB. These ceiling trends generally continue until around mid-day Thursday. Gusty northwest winds will continue through the remainder of the TAF period, gusting the strongest at BLF and ROA (30-32 kts). Given the strong wind field, some potential for turbulence in/around the ridgetops due to mountain waves Thursday. Extended Aviation Discussion... Ceilings begin to improve to VFR all terminals late Thursday afternoon. While winds will continue to be rather gusty, anticipate a diminishing trend to northwesterly sustained wind and gusts during the overnight hours on Thursday. Generally VFR overnight into early Friday, perhaps briefly falling to an MVFR ceiling at BLF and LWB as a shortwave trough rotates southeastward. Next potential for sub-VFR conditions is not until later Saturday as a disturbance moves in from the Deep South producing showers. Lower ceilings may linger into Sunday across BLF and LWB, but becomes VFR Sunday night through Monday. && .RNK WATCHES/WARNINGS/ADVISORIES... VA...None. NC...None. WV...None. && $$ SYNOPSIS...AL NEAR TERM...AL SHORT TERM...MBS LONG TERM...MBS AVIATION...AL/PM

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