Area Forecast Discussion
Issued by NWS Blacksburg, VA

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000 FXUS61 KRNK 201937 AFDRNK Area Forecast Discussion National Weather Service Blacksburg VA 237 PM 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 1001 AM EST Monday...Visible satellite still reveals ongoing stratus/fog across most of southeastern West Virginia (excluding Mercer County). Low visibilities were still noted in recent LWB METARs in the fog. While it has been slower to burn off than initially anticipated due to some high clouds, high cloudiness has begun to erode and should allow for sun to mix it out through the rest of this morning. Otherwise, I`ve tried to raise dewpoints through this morning which are currently well into the 30s to mid 40s. However, expect these to lower by late morning into the afternoon as mixing of dry air aloft begins. It should be a great holiday for those outdoors today with temperatures well into the 60s to lower 70s, plentiful sun and light winds. Previous near-term discussion issued at 218 AM follows... 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 /17Z MONDAY THROUGH FRIDAY/...
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As of 1230 PM EST Monday... VFR through the TAF period. SKC conditions with light and variable winds through the afternoon, give way to increasing field of mid to high-level cloud cover from southwest to northeast tonight. Low confidence on prospects for river valley fog development tonight given that crossover temperatures may not easily be met, very dry soils from this afternoon and there appears to be just enough of a southerly boundary layer flow to mitigate much development. A continued areal coverage/thickening of mid to high level clouds anticipated through 18z Tuesday as cold front remains slow to advance east. If there is an area where low clouds may develop Tuesday, it would be for the eastern TAFs given onshore flow/CAD signature. But confidence on that happening is low based on little indication from model RH profiles. Winds initially southerly western TAFs with light easterly winds for LYH/DAN, but become southerly around 4-7 kts all TAFs ahead of aforementioned front. Extended Aviation Discussion... A continued lowering/thickening of cloud cover expected through the rest of the Tuesday afternoon and early evening hours. 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...AL/JH SHORT TERM...RCS LONG TERM...AMS AVIATION...AL/JH CLIMATE...DS is the U.S. government's official web portal to all federal, state and local government web resources and services.