Area Forecast Discussion
Issued by NWS Blacksburg, VA

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000 FXUS61 KRNK 181148 AFDRNK Area Forecast Discussion National Weather Service Blacksburg VA 748 AM EDT Sat Mar 18 2017 .SYNOPSIS... Low pressure was over Michigan this morning with a warm front that was moving north over West Virginia and Virginia and a cold front that trailed into the Mid Mississippi Valley. The cold front will cross east through the Mid Atlantic region today. High pressure will follow the front for Sunday and Monday then another low pressure system and series of fronts will move through the region on Monday night and Tuesday. && .NEAR TERM /THROUGH TONIGHT/... As of 450 AM EDT Saturday... Short wave tracking into northern Kentucky was triggering showers and a few thunderstorms across Tennessee and North Carolina. Radar trends since 2AM have been for decreasing coverage of precipitation over West Virginia and Virginia. Expect showers to diminish even across North Carolina by around 12Z/8AM. Then there will be a break before the next chance of precipitation. A cold front extended from a low in Michigan to northern Arkansas. This front will move east today and will be pushing off the Virginia coast this evening. HRRR indicated showers and isolated to scattered thunderstorms will develop ahead of the front from northeast Tennessee to southwest Virginia, while the RAP and other guidance had the precipitation developing just east of Lynchburg and Danville. With this spread in possible locations, have added a chance of precipitation across much of the area this afternoon. Upper low moving out of the great lakes will provide cooler air aloft today and therefore larger lapse rates, especially with any heating. Models showed CAPES around 400 J/Kg this afternoon with Lifted Index values as low as -4. Guidance also showed a large difference in solutions for maximum temperatures today. Since area will be in the warm sector for part of the day and some sun will break through later this morning have leaned toward warmer guidance which was well represented by the Hi-Resnmm and Hi-Resarw. Best advection of colder air will be late tonight. Pressure rises and cold air advection support gusty wind. Also tonight low level moisture remains banked up along the western slopes of the Appalachians. Temperatures will be cold enough for snow but lack of depth of moisture makes dendritic crystal growth more questionable. Liquid equivalent precipitation amounts remain less than one quarter inch. Snow accumulations of any consequence will be confined to Western Greenbrier County. && .SHORT TERM /SUNDAY THROUGH MONDAY NIGHT/... As of 330 AM EDT Saturday... An upper level low will track off the Virginia coast Sunday morning. Until this low departs, short waves tracking around it will bring upslope snow showers to western slopes of SE WV/SW VA through most of the morning. Once this low moves out to sea in the afternoon, a chilly surface high will build over the region and end northwest upslope snow showers. High temperatures Sunday will vary from the mid to upper 40s across the mountains to mid to upper 50s east into the piedmont. This high will be centered over the area Sunday night. Under mostly clear skies and light winds, temperatures will radiate down into the upper 20s to lower 30s. This area of high pressure will sink south to the Gulf Coast during the day Monday. Meanwhile, a warm front will track across the Ohio and Tennessee Valleys Monday and Monday night. By late in the day, this warm front and a lee trough will help bring in a few scattered showers across the mountains. Mountain showers may persist into the night as a cold front approaches the area from the north. The best chance for widespread showers will come Tuesday as the cold front moves over the region. Rainfall amounts should remain light Monday afternoon and night as high pressure blocks moisture from returning from the Gulf. Temperatures Monday will warm into the 60s and overnight remain mild in the 40s. && .LONG TERM /TUESDAY THROUGH FRIDAY/... As of 400 PM EDT Friday... The cold front should move from northwest to southeast over the CWA on Tuesday. Meanwhile, another upper level trough will dig southward from eastern Canada to bring colder air behind the frontal passage. If the cold air arrives quickly enough, it could change the rain to snow in the higher elevations of southeast West Virginia and the northwest North Carolina mountains by Tuesday night. Cold air advection will continue through Wednesday as a strong high pressure area builds southeastward from the Great Lakes. Once overhead by Wednesday night, expect another cold night with temperatures well below freezing. This high should slide eastward toward the coast on Thursday, and the numerical models hint that some wedging may occur east of the Blue Ridge. A warm front will also approach from the west due to a potent low pressure system over the northern Plains on Friday, so the CWA should break free of the wedge with good southwesterly flow and a building upper level ridge. && .AVIATION /12Z SATURDAY THROUGH WEDNESDAY/...
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As of 740 AM EDT Saturday... Precipitation over northern North Carolina will continue to move away from the central Appalachians this morning. Area of LIFR stratus and fog was west of a line from KBCB to KHLX. There will be slow improvement in this area this morning with conditions back to MVFR by noon. The cold air aloft associated with the approaching upper low will create good lapse rates and potentially enough instability for isolated to scattered showers and thunderstorms in the afternoon along and ahead of a cold front. Medium confidence on the timing of showers and thunderstorms this afternoon. HRRR showed it farther west and RAP showed development east of KLYH and KDAN. Think the best chance will be from 18Z/2PM through 23Z/7PM. Upslope snow showers will develop after 21Z/5PM and will continue for much of the night with MVFR ceilings and visibilities, including at KBLF and KLWB. Ceilings at TAF sites east of the Blue Ridge will be VFR today away from the precipitation. Winds will be gusty behind the front with gusts up to 30 knots along and west of the Blue Ridge. Extended Aviation Discussion... Gusty post frontal northwest winds continue into Sunday morning. High pressure building in on Monday should yield VFR all terminals to start the week. However moisture ahead of another cold front and associated weak low pressure may arrive by Monday night, with sub-VFR possible later Monday night into early Tuesday before improving conditions take shape into midweek.
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&& .RNK WATCHES/WARNINGS/ADVISORIES... VA...None. NC...None. WV...None. && $$ SYNOPSIS...AMS NEAR TERM...AMS SHORT TERM...RCS LONG TERM...PW AVIATION...AMS/JH/WP

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