Area Forecast Discussion
Issued by NWS Blacksburg, VA

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000 FXUS61 KRNK 211708 AFDRNK Area Forecast Discussion National Weather Service Blacksburg VA 108 PM EDT Wed Sep 21 2016 .SYNOPSIS... An upper low will meander about eastern North Carolina and South Carolina through late week before finally shifting out into the Atlantic ocean. High pressure will gradually build in from the west during the latter half of the week. A backdoor cold front drops south through the area later Saturday followed by cooler high pressure Sunday into Monday. && .NEAR TERM /THROUGH TONIGHT/... As of 100 PM EDT Wednesday... Adjusted pops further west this afternoon with latest WSR-88D trends. As of 905 AM EDT Wednesday... Made some minor adjustments in temperatures shaping towards sfc obs and lamp guidance for this morning, then allowing for a rise in the east this afternoon. (Clouds cover and scattered showers will hold temperatures down this morning in Southside.) Also, modified pops for this morning with latest WSR- 88d trends and push isolated chances a little further west for this afternoon. The Hiresw-arw-east, WRF-arw-rnk and HRRR support the mention of isolated to scattered showers across the southeast portions of forecast area. Expecting a nice day under sunshine in the west and northwest portions of forecast area. More changes later this morning. As of 315 AM EDT Wednesday... Looking at lingering low pressure from Julia combined with upper low over Eastern NC to keep the eastern half of the forecast area in clouds for most of the day today. Models in general agreement in showing a sharp gradient to showers, mainly keeping them southeast of a line from Farmville to Yadkinville. The 00z ECM is a little more broad in coverage as far west as the Blue Ridge. The 00z NAM actually seems to have a good handle of ongoing showers east of our forecast area, but is showing some higher qpf later today across the northwest piedmont of NC east of Reidsville into Halifax county Virginia. For the forecast today, am leaning toward a drier scenario from the foothills west into the mountains with high chance pops in the extreme southeast cwa to slight chance/20 pops toward Lynchburg/Martinsville and Yadkinville. High level clouds will obscure the sunshine at times as far west as the I-81 corridor with more sunshine in Southeast WV and generally cloudy in the east. Highs will still be warm with mid 70s to around 80 expected, but possibly warmer toward Abingdon and Richlands in the lower 80s. The gradient today will also tighten to allow a breeze of 10 mph with gusts to 20 mph especially along and east of the Blue Ridge. Tonight, the upper low remains fixed across the coastal Carolinas. At the surface the low jogs somewhat southwest. Orientation for best shower coverage will wrap tighter toward the coast, so will dry things out overnight with lingering low chance pops in the evening in the far southeast from South Boston VA to Reidsville, NC. Otherwise will be clearing in west but remains mostly cloudy in the piedmont south of Lynchburg, as well as across the NC mountains and foothills. Lows should stay mild in the east with mid 60s, with upper 50s to lower 60s west, which is still about 5 to 10 degrees above normal. && .SHORT TERM /THURSDAY THROUGH SATURDAY NIGHT/... As of 230 AM EDT Wednesday... During this portion of the forecast, a upper low over South Carolina will make slow progress to the southeast, all while an upper ridge builds over the Ohio and Mississippi Valleys. Concurrently, a broad upper trough will reside over southeast Canada, and southerly flow on its west side will propel a backdoor cold front into our region Saturday into Saturday night. The result of this transition will be even less coverage of isolated showers across the south and southeastern portion of the region. Only the Canadian solution at this point has more of a glancing blow of precipitation for this portion of the forecast area. The forecast will reflect the last isolated showers departing the far southeastern sections Thursday evening. High pressure will provide for limited cloud cover on Friday into Friday night with no precipitation forecast. The backdoor cold front at this point is progged to have little if any precipitation associated with in Saturday into Saturday night, but an increase in cloud cover is anticipated. Lower dew point air will start moving into northern sections of the area by late Saturday night. Temperatures will continue to average about ten degrees above normal through Saturday night. && .LONG TERM /SUNDAY THROUGH TUESDAY/... As of 130 PM EDT TUESDAY... Strong upper ridging centered along the Mississippi River to start the weekend will gradually get pinched back to the southwest as a rather high amplitude troughing regime develops over the northeast U.S. by early next week. This will allow increasing northwest flow aloft to take shape across the region between the departing 500 mb ridging and eventual upper level low pressure over New England. Cooler high pressure expected Sunday into Monday. This before yet another cold front arrives from the northwest on Tuesday with the next stronger mid level shortwave. However deeper moisture looks quite limited with both frontal passages given a dry west/northwest flow aloft so only including slight shower pops later Saturday west and again Tuesday. Low level flow turning more east/northeast behind the initial boundary, per the developing wedge could allow for a slight uptick in shower coverage southern sections Saturday night, although iffy for much more than clouds/sprinkles at this point per lower amplitude/drier ensembles. Subsequent rounds of decent cool advection look to arrive with each frontal passage into late Tuesday with potential for Sunday into Monday to remain quite cool if clouds are more widespread. This timing continues to vary between solutions as each may be too strong, although thinking highs mostly 70s Sunday-Tuesday, with 50s for lows and possible 40s valleys Monday morning with high pressure overhead. && .AVIATION /18Z WEDNESDAY THROUGH SUNDAY/... As of 108 PM EDT Wednesday... Scattered to broken MVFR clouds with patches of showers mainly east of the blue ridge this afternoon into tonight. Northeast winds may be breezy this afternoon into this evening with gusts to 20kts along and east of the Blue Ridge Mountains. Winds will become light easterly tonight into Thursday morning. Tonight the skies will clear from northwest to southeast to a point, but remain broken at the high cloud level overnight in the DAN area. Model forecast soundings with easterly flow suggest potential for low cloud development or advecting in from the east along with patchy fog. Will keep it optimistic and go no lower than MVFR at LYH/DAN/BLF/BCB on vsbys with IFR/LIFR at LWB late tonight. Morning fog and low clouds will lift by mid morning, return all taf sites to VFR conditions by Thursday afternoon. Winds Thursday afternoon will be light and variable. Medium to high confidence in ceilings,visibilities and winds during the taf period. Extended aviation discussion... The slight chance of MVFR showers will remain just east of KLYH and KDAN through Thursday night. VFR conditions will prevail Thursday night outside of late night/early morning fog/low clouds. GFS/ECMWF have been consistent in filling and lifting out the low to the northeast on Friday. VFR conditions will prevail on Friday. A back-door cold front will come through the Mid-Atlantic region on Saturday. High pressure will build in for Sunday. The chance of precipitation or any sub VFR conditions will increase through the day Sunday and into Sunday night. Next cold front arrive by Midweek with potential for MVFR/IFR conditions. && .RNK WATCHES/WARNINGS/ADVISORIES... VA...None. NC...None. WV...None. && $$ SYNOPSIS...RAB/WP NEAR TERM...KK/WP SHORT TERM...DS LONG TERM...JH AVIATION...KK/WP is the U.S. government's official web portal to all federal, state and local government web resources and services.