Area Forecast Discussion
Issued by NWS Blacksburg, VA

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000 FXUS61 KRNK 201124 AFDRNK Area Forecast Discussion National Weather Service Blacksburg VA 624 AM EST Mon Feb 20 2017 .SYNOPSIS... 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. && .NEAR TERM /THROUGH TONIGHT/... 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. && .SHORT TERM /TUESDAY THROUGH THURSDAY/... 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. && .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 /11Z MONDAY THROUGH FRIDAY/...
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As of 610 AM EST Monday... Low clouds and fog will persist in spots across the western locations early this morning with IFR/LIFR cigs/vsbys primarily at KLWB and MVFR possible KBLF/KBCB vicinity. Further east will be VFR. The low clouds/fog should dissipate by mid morning if not sooner with periodic high/mid cloud canopy expected under light/variable to easterly winds the rest of the day. Moisture will continue to increase overnight with VFR high/mid cloud cigs overnight at most locations. Also some strato-cu may develop along the Blue Ridge late as onshore flow increases, but too uncertain to include any lower cigs at this point tonight. Fog/stratus likely quite spotty overnight as well unless less high level cloud cover is realized allowing low level saturation across the valleys such as KLWB/KBCB. Extended Aviation Discussion... Expect overall VFR to prevail through much of Tuesday as a weak cold front to the west remains slow to move east with potential for MVFR cigs to arrive mainly across the mountains later in the day. However will have to watch possible MVFR level low clouds earlier along the Blue Ridge as a weak low level wedge develops. Showers and likely sub-VFR to develop Tuesday night into early Wednesday with an axis of showers preceding the weakening cold front arriving from the west. Expect showers to decrease Wednesday afternoon and night while leaving residual MVFR cigs in place. Later Thursday into Thursday night, low confidence of patchy light rain returning to the area, with cigs and vsbys remaining mainly VFR except for ocnl MVFR across southern and western sections. Friday, moderate confidence in precipitation trending more showery, as the 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. Surface wind gusts of 20 to 30 kts possible across the higher terrain. Band of showers with the front to arrive Friday night into early Saturday followed by drier weather and increasing northwest wind by afternoon behind the front.
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&& .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...JH CLIMATE...DS is the U.S. government's official web portal to all federal, state and local government web resources and services.