Area Forecast Discussion
Issued by NWS Blacksburg, VA

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000 FXUS61 KRNK 200815 AFDRNK Area Forecast Discussion National Weather Service Blacksburg VA 315 AM EST Mon Feb 20 2017 .SYNOPSIS...
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High pressure will build over the region today and remain in place through at least Tuesday. A weak cold front will approach the area from the west Tuesday night before weakening across the mountains on Wednesday. A warm front will move north through the region Thursday into Friday.
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&& .NEAR TERM /THROUGH TONIGHT/...
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As of 218 AM EST Monday... Another very mild day for late February in store today as strong upper level ridging builds overhead while surface high pressure bridges south just east of the mountains later this afternoon. This coupled with high heights and warm 850 mb temps under strong insolation despite some high clouds, should allow highs to reach the 60s west to lower 70s east. Low level flow turning more southeast later in the day likely to keep values a bit more uniform as well with slight cooling noted aloft out east later today and downslope warming into southeast West Va. Therefore appears best shot at record highs mainly over the south and west per the CLIMATE section below. Otherwise few changes other than to include a bit more western fog/low clouds to start that should quickly erode this morning with heating under dry air aloft. Ridging aloft remains in place overnight with surface high pressure becoming more wedge oriented as it slips southeast to along the Mid- Atlantic coast late. Influx of sheared high/mid cloudiness coming through the mid level ridging from showers well to the west likely to become more widespread after midnight as suggested by most guidance. Also low level southeast flow turning westerly with height could produce a ribbon of low clouds along the Blue Ridge by daybreak but iffy given such weak flow/subsidence. Thus keeping things more of a partly cloudy flavor for now given mid level dryness seen on progged cross sections, and model tendency to be overdone with high clouds through strong ridging that will be overhead late. Warmest air will again be over the far west with the cooler wedge out east per onshore flow overnight. However think weak enough for some decoupling espcly outlying areas, while the ridges likely to keep some mixing. This supports a range of lows from near 50 higher western ridges to 30s/low 40s valleys/east, while keeping mostly 40s elsewhere in between.
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&& .SHORT TERM /TUESDAY THROUGH THURSDAY/...
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As of 240 AM EST Monday... The upper level ridge will move offshore Tuesday afternoon with zonal flow to follow Tuesday night. Within this zonal flow, a weak cold front will move across the Ohio Valley and over the central Appalachian Tuesday night. This front will help bring rain showers to the area after midnight then exits Wednesday afternoon. This front is initially lacking moisture, but will get hydrated with the help of an open Gulf and an ejected short wave tracking over the Tennessee Valley. This short wave will track out of the Gulf ahead of a closed low and gets caught in zonal flow, moving into North Carolina Wednesday. Models are in agreement with taking the short wave and measurable rainfall south of the area Wednesday night. However, an insitu wedge will follow with gray drizzly conditions possible Wednesday night and Thursday. The chances for rain returning Thursday increases as insentropic lift associated with a warm front aloft tracks to the north and over the wedge. Temperatures during the period will remain warmer than normal. Tuesday looks to be the coolest day with rain and easterly flow in the area. Temperatures Tuesday will be in the low to mid 60s across most of the area with upper 50s along ridgetops. Once we break out of the rain Wednesday afternoon, temperatures will jump into the upper 60s to mid 70s. Thursday will be a tricky forecast with temperatures. They could be similar to Tuesday or to Wednesday. Even though the models are showing an insitu wedge over the region, they also have southerly flow and temperatures warming into the upper 60s to mid 70s. If the insitu wedge does linger through the day Thursday, thick low clouds, easterly flow, and light rain/drizzle could keep temperatures down into the lower to mid 60s areawide. Until confidence increases on the scenario for Thursday, we will stick close to model guidance.
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&& .LONG TERM /THURSDAY NIGHT THROUGH SUNDAY/... As of 235 PM EST Saturday... Per WPC, not much weight put on the GFS, especially Friday through Sunday, as it is faster with most of the synoptic scale features than much of the other guidance. Timing of the cold frontal passage still similar with the front coming through Saturday morning. 00Z ECMWF had colder air behind the front just brushing through the Mid Atlantic region, which was not nearly as cold and as far a push south as previous runs. High temperatures will still drop about 10 degrees but coldest air will start moderating after Sunday morning. A low level jet and cold air advection will result in strong gusty winds behind the front into Sunday morning. && .AVIATION /08Z MONDAY THROUGH FRIDAY/... As of 1124 PM EST Sunday... Looking at potential fog and/or low cigs at BLF and at times LWB. As of 0420z, lower cigs were eroding to the northwest of LWB. However, models trying to infringe into BLF/LWB again by 09z some sct/bkn mvfr to ifr cigs. At the same time IFR vsbys had developed over BKW. Profile soundings suggest that fog will be possible at BLF/LWB but with lack of wet ground and greenup, confidence is not that high, but with models insisting on lower vsbys especially in BLF will keep a tempo there for the 10-12z time frame. Further east will be VFR. The low clouds/fog is expected to go away by 12-14z, with VFR expected through the end of this taf period. Low confidence in cigs/vsbys at LWB/BLF and high elsewhere, through 14z Monday, but high thereafter at all sites. Extended Aviation Discussion... VFR into Tuesday morning. Moderate to high confidence of patchy MVFR conditions across the mountains Tuesday afternoon into Wednesday with the passage of a cold front. East of the Blue Ridge, mainly VFR conditions will prevail. Thursday into Thursday night, moderate confidence of patchy light rain returning to the area, with ceiling and visibilities remaining mainly VFR. Some patchy MVFR is possible. Friday, moderate to high confidence of precipitation trending more showery, as low level jet increases in advance of a strong cold front. Expect a mix of MVFR and low end VFR ceilings and mainly VFR visibilities with isolated, brief sub-VFR visibilities under heavier showers. Surface wind gusts of 20 to 30 kts possible across the higher terrain. Showers may linger in the western mountains Saturday morning. Drier weather will prevail for much of the weekend. && .CLIMATE... As of 315 PM EST Sunday... Record High Temperatures and Year of Occurrence Feb 20 Blacksburg, VA..68 in 1984 Bluefield, WV...67 in 1986 Danville, VA....74 in 1971 Lynchburg, VA...76 in 1930 Roanoke, VA.....75 in 1939 && .RNK WATCHES/WARNINGS/ADVISORIES... VA...None. NC...None. WV...None. && $$ SYNOPSIS...JH NEAR TERM...JH SHORT TERM...RCS LONG TERM...AMS AVIATION...DS/KK/WP CLIMATE...DS

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