Area Forecast Discussion
Issued by NWS Blacksburg, VA

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000 FXUS61 KRNK 230012 AFDRNK Area Forecast Discussion National Weather Service Blacksburg VA 712 PM EST Wed Feb 22 2017 .SYNOPSIS... Weak high pressure off the mid-Atlantic coast will stay situated here through Thursday morning. A frontal boundary across the Great Lakes into the southern Plains shifts slowly southeast to the Ohio Valley by Friday. The main cold front across the midwest will pass through our area Saturday. && .NEAR TERM /THROUGH THURSDAY/... As of 228 PM EST Wednesday... Been seeing decreasing trend and southward trend in rainfall. Models hang onto some isentropic lift over the southern CWA through early evening then moisture and lift become shallow/weak. Main issue overnight could be fog. Forecast soundings showing very shallow moisture near/at the surface and hints of dense fog are there as well. With weak wind flow added more fog in the east overnight and along the Blue Ridge. Still with cloud cover, coverage of dense fog is iffy so no advisories planned with this forecast. Lows tonight will be about 5-10 degrees cooler than 2pm temperatures this afternoon, ranging from the mid to upper 40s most locales. Thursday, frontal boundary situated from the Eastern Great Lakes, southwest to the Southern Plains, in the morning, will slowly advance south to a PIT-IND-TOP line by late in the day. Models break the in-situ wedge as sfc flow turns more southwest. Will see more sunshine in the piedmont in the afternoon, with sunshine at times in the west followed by more clouds ahead of a shortwave that passes across KY into Ohio in the afternoon. This shortwave combined with some low level convergence across the mountains may lead to some showers and even thunderstorms in the afternoon, mainly from the Alleghanys southwest to southern WV, with limited coverage southeast to the foothills. As wedge erodes, expect temperatures to soar to the lower to mid 70s east of the mountains, with mid to upper 60s across the west. Some record high temps may be approached and/or broken. See climate section below. Even record warm low temperatures will be possible for Thursday 2/23. && .SHORT TERM /THURSDAY NIGHT THROUGH SATURDAY NIGHT/... As of 250 PM EST Wednesday... Thursday night through Friday night, the area will be under a region of deep south to southwest flow, with its origins from the eastern Gulf of Mexico. A warm front will lift north of the area Thursday night. While some patchy light rain will be possible early in the evening for the area of the region west of the Blue Ridge, coverage will decrease through the night as the front continues heading north of the area. Lingering upslope light rain will remain possible near the crest of the Blue Ridge, especially in areas southwest of Floyd, VA into the Northern Mountains of North Carolina. On Friday, most of the area will be precipitation-free, save a few locations near the crest of the Blue Ridge thanks to local upslope conditions. Friday night into early Saturday, a cold front will approach the region from the west, and cross the area during the day Saturday. Look for increasing chance of rain showers with the approach and passage of this feature. There will also be a slight chance of thunderstorms with the passage. By Saturday night, the front will be to our east, and northwest winds will be on the increase. The northwest winds will yield some gusts approaching 40 to 45 mph at the highest elevations. Also, colder air will start working its way into the area. Lingering upslope rain showers across parts of southeast West Virginia, south into the Northern Mountains of North Carolina are expected to transition to snow showers by Sunday morning. Temperatures Thursday night through Saturday are expected to average about twenty degrees above normal. Saturday night, behind the cold front, temperatures will fall to readings near normal. && .LONG TERM /SUNDAY THROUGH WEDNESDAY/... As of 300 PM EST Wednesday... Gusty winds will continue into early Sunday behind Saturday`s cold frontal passage. These winds will weaken quickly during the day and back southwest as the next upper level trough deepens across the Central Plains. This same upper trough will move east and be over the Ohio Valley by mid-day Monday. A warm front in advance of this system will head north through our region, bringing a return of patchy light precipitation to the area during the day Monday. There may be an issue of a brief period of a wintry mix across the northwest section of the area early Monday as a potential warm nose develops over a sub-freezing boundary layer and surface. For now, will keep things simple by reflecting a rain versus snow forecast based solely on whether the forecast surface temperatures is above or below freezing. Monday night the system`s associated cold front is expected to cross the area. Look for the precipitation to become more showery Monday night into early Tuesday. Model guidance for the remainder of Tuesday into Tuesday evening is not clear. The GFS is progressive with the cold front making significant headway east of the region. The ECMWF is not progressive, stalling the feature over the area, all while suggesting another wave will move northeast along this boundary, keeping a generous coverage of rain across the area Tuesday afternoon into Tuesday night. Our forecast will reflect a blend of these solutions. While rain will be forecast Tuesday afternoon and evening, it will not be to the degree offered by the ECMWF. For late Tuesday night into Wednesday, model agreement improves with solutions bringing yet another upper low/trough from the Central Plains states into the Ohio Valley. Warm frontal rain is expected late Tuesday night into early Wednesday, with a generous coverage of showers and some isolated thunderstorms across the area Wednesday afternoon coincident to the cold frontal passage. Temperatures Sunday and Monday will be normal for this time of year. Reading moderate through mid-week with temperatures some ten to fifteen degrees above normal expected. && .AVIATION /00Z THURSDAY THROUGH MONDAY/... As of 710 PM EST Wednesday... Lingering precipitation associated with a trof passing by to our south sending short wave energy riding over a wedge of high pressure at the surface will dissipate to a few sprinkles early this evening. However, earlier widespread precipitation has left the boundary layer quite moist. Believe as mid/high clouds pull away with the departing trof, cooling will allow the boundary layer and fog/stratus will set in at all TAF sites late tonight and persist through daybreak. The expected progression of dissipating precipitation, departing upper clouds, cooling, and formation of fog/stratus will likely yield a good degree of variability in vsbys/cigs until IFR conditions become firmly established. thus, will choose to keep TAFs on the pessimistic side and be reluctant to amend upward. The fog/stratus looks to burn off Thursday morning with a return to VFR conditions by the afternoon. However, a weak frontal boundary will brush the region as an area of low pressure moves through the Great Lakes region tomorrow. This may bring a shower to locations west of the Blue Ridge so will include VCSH after 18Z all sites except KDAN and KLYH. Winds will be light through the period. Extended Aviation Discussion... Thursday night-Friday, we will be well into the warm sector with VFR conditions and much above normal temperatures. Surface wind gusts of 20 to 30 kts possible across the higher terrain. Band of showers and isolated thunderstorms with MVFR conditions arrive late Friday night into early Saturday along and ahead of a strong cold front. Drier weather and increasing northwest winds follow behind the front on Saturday afternoon through Sunday. Approach of another front Monday will provide increasing clouds and possibly showers and MVFR cigs to BLF/LWB late in the day. && .CLIMATE... As of 245 PM EST Wednesday... Warm temperatures set to occur again Thursday with increase in westerly flow in the low levels. Question will be cloud cover. At the moment with some sunshine look for highs and lows to approach or break records for Feb 23rd. Thursday 02/23/2017 Site Record High/Year Record Warm Low/Year Bluefield 74 1975 51 1975 Danville 73 1980 50 1981 Lynchburg 74 1943 52 1925 Roanoke 76 1943 54 1925 Blacksburg 69 1980 46 1990 && .RNK WATCHES/WARNINGS/ADVISORIES... VA...None. NC...None. WV...None. && $$ SYNOPSIS...AMS/WP NEAR TERM...WP SHORT TERM...DS LONG TERM...DS AVIATION...MBS/WP CLIMATE...WP is the U.S. government's official web portal to all federal, state and local government web resources and services.