Area Forecast Discussion
Issued by NWS Blacksburg, VA

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000 FXUS61 KRNK 222354 AFDRNK Area Forecast Discussion National Weather Service Blacksburg VA 654 PM EST Thu Feb 22 2018 .SYNOPSIS... High pressure will remain off the Southeast coast into Friday, promoting above normal temperatures. A weak backdoor cold front will drop south tonight, then return north as a warm front late Friday. A stronger front will move through the region from the Ohio Valley this weekend. && .NEAR TERM /THROUGH FRIDAY/... As of 620 PM EST Thursday... The backdoor front is starting to move into the area this evening. Temperatures at 6pm at Roanoke was 75F, Lynchburg was 54F and Charlottesville was 49F. This cool air will work south overnight. Light rain may accompany the front passage. Behind the front, low level moisture and easterly flow will keep low clouds, light rain, and drizzle in the area through Friday morning. As of 328 PM EST Thursday... A strong subtropical ridge of high pressure will remain anchored off the Southeast Coast tonight into Friday. Record warm temperatures this afternoon will remind everyone of Summer. A weak disturbance tracking around the northwest side of the upper ridge and an approaching back door front from the northeast may generate some showers across the northwest portion of forecast area mainly the Greenbrier Valley. Backdoor cold front will drop south this evening into tonight. This will introduce a cool wedge to areas east of the Appalachians. Have concerns this afternoon that the southern edge of low clouds have been eroding and lifting as it moves slowly south. The frontal boundary is expected to drop south and push down the Blue Ridge mountains. Then, the front will retreat northward Friday. For weather, initially started with convective showers then transition weather type to rain, drizzle and fog. Utilized a blend of the Conshort and NAM to capture the drop of temperatures with the frontal boundary. Low temperatures will range from the mid 40s deeper into the cool air to the mid 50s along the southern Blue ridge. Friday begins with areas of rain, drizzle and fog in the morning, then becomes scattered showers in the afternoon. Temperatures remain a challenge for Friday with a sharp gradient. How far south the front travels will be a key. High temperatures Friday will vary greatly from the lower to mid 70s outside the wedge especially in the western mountains and southwest mountains to the lower to mid 50s in the northeast deep in the relatively cooler air. && .SHORT TERM /FRIDAY NIGHT THROUGH SUNDAY NIGHT/... As of 245 PM EST Thursday... Wedge of cool air should slowly weaken Friday night as a surface warm front lifts back northeast through the region before sliding well to the north on Saturday. May still see some spotty drizzle/fog linger in the northeast where the CAD typically holds longer espcly at night, otherwise mainly cloudy with steadying or rising temps in the 40s/50s overnight. Some small shower chance also far northwest as moisture spills over from the front west of the mountains but iffy at this point. Area slides back into the warm sector Saturday behind the exiting warm front and ahead of the main cold front that will approach from the west by Saturday night. This should set the stage for another breezy and very mild day with highs upper 60s to mid 70s under some sunny breaks. Again models attempt to generate scattered showers but likely overdone given slight height rises and focus of better lift well west of the mountains. Therefore lowered pops back to mainly chance far west/southwest and isolated elsewhere which may be generous. Cold front arrives from the west late Saturday night before slowly crossing the region in weakening fashion on Sunday. Appears a pre- frontal lobe of showers may reach the western sections late Saturday night but moreso Sunday morning with this swath of rainfall sliding east across the rest of the area Sunday. However models remain slower with potential for some splitting of the showers over the west with a jump to the piedmont later in the day where some instability will reside. Cant rule out isolated thunder far southeast so will leave in mention with high pops elsewhere for now, but with QPF of only a quarter to one half inch possible. Should be the last of the really warm days espcly if the boundary is slower so bumped up highs well into the 70s east, and 65-70 west similar to most extended guidance Mos. Front likely slow to exit the southeast Sunday night but degree of leftover deep moisture in question given a more progressive scenario off the GFS and brief drying seen on the latest ECMWF. However latest ensembles suggest that a few shower bands may hang on into the overnight espcly south and east until the actual 850 mb boundary crosses which wont happen until very late. This supports keeping in a 20/30 type pop across the region as the cool advection regime steadily increases overnight pushing lows back into the 40s most spots. && .LONG TERM /MONDAY THROUGH THURSDAY/... As of 300 PM EST Thursday... Upper flow will transition to a more zonal trajectory by early next week with weak shortwave ridging giving rise to a brief drier period early on before moisture returns by the end of the period. Could see some lingering showers espcly eastern/southern sections Monday in the wake of the exiting front from the weekend, as some solutions including the 12z ECMWF/CMC bring another weak wave up the front across the Carolinas. Therefore despite a lot of uncertainty will keep low pops mainly Monday morning along/southeast of the Blue Ridge before tapering from west to east in the afternoon. Otherwise models show high pressure building in by late Monday while remaining overhead Monday night before sliding to the coast on Tuesday. This should bring somewhat cooler and drier weather into Tuesday night with highs in the 50s/low 60s, which remains a good 10 degrees or so above normal. Fast west/southwest flow aloft looks to bring pieces of upper energy out of the southwest states by Wednesday with a couple waves ahead of a parent mid level system that will eject out into the upper Midwest by Thursday. This should result in an axis of deeper moisture lifting back north through the TN valley by early Wednesday and into our region Wednesday afternoon/night as a warm front edges north. Moisture remains in place well ahead of the trailing cold front that will approach Thursday with at least added showers around. Thus running with decent chance to low likely pops for mid week at this point. Highs again mostly 50s/60s with cooler values mountains Wednesday, and warmer readings possible Thursday east well ahead of the cold front. && .AVIATION /00Z FRIDAY THROUGH TUESDAY/... As of 640 PM EST Thursday... VFR ceilings will lower to MVFR this evening, then to IFR overnight. A backdoor cold front in central Virginia will slowly drop south this evening into tonight. In its wake, a northeasterly wind will develop with CIGS/VSBYs expected to drop into the IFR Category tonight with areas of light rain, drizzle and fog. Conditions will likely be IFR to start the day Friday and likely remain IFR to MVFR throughout the day. Winds in advance of the backdoor cool front will be S-SW 5-10 mph, then become northeast behind the front at 5 to 10 mph tonight. Medium confidence in ceilings, visibilities and winds through the TAF valid period. Extended Aviation Discussion... The backdoor cold front will stall along the Virginia and North Carolina line and retreat northward as a warm front toward Friday evening. VFR conditions should return for most locations during Friday night and Saturday aside from any typical low clouds along the Blue Ridge on Saturday morning. By Saturday afternoon, shower coverage should increase as a cold front arrives from the west that could bring MVFR/IFR conditions toward Sunday. Better flying weather should return later on Monday and Tuesday. && .RNK WATCHES/WARNINGS/ADVISORIES... VA...None. NC...None. WV...None. && $$ SYNOPSIS...KK/PM NEAR TERM...KK/RCS SHORT TERM...JH LONG TERM...JH AVIATION...KK/RCS CLIMATE...PM is the U.S. government's official web portal to all federal, state and local government web resources and services.