Area Forecast Discussion
Issued by NWS Blacksburg, VA

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000 FXUS61 KRNK 231116 AFDRNK Area Forecast Discussion National Weather Service Blacksburg VA 716 AM EDT Fri Sep 23 2016 .SYNOPSIS... Low pressure along the coast of the Carolinas will weaken and head east tonight. A back door cold front enters the area by Saturday night. As it moves south of us Sunday the flow turns east which brings in more clouds and a threat of showers into early next week. && .NEAR TERM /THROUGH TONIGHT/...
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As of 705 AM EDT Friday... Showers and lower clouds have begun to diminish over southside Virginia, so expect this trend to persist through the morning. Forecast updated to follow this trend. Previous morning discussion... Upper trough situated across the mid-Atlantic and Southeast will continue to weaken and get kicked eastward ahead of a digging northern stream shortwave over the northeast through late tonight. Model do cut off a piece of the upper energy and drift it southwest to southern Georgia. For our area the upper heights will begin to build as strong ridge pushes into the Mid Mississippi Valley. The few showers over southside Virginia into northwest NC will fade and/or shift southeast of the forecast area by mid morning. Should see increasing sunshine. There will be a difference in dewpoints from the mountains to the piedmont, ranging from the mid 50s west to mid 60s southeast. With drier air and sunshine temperatures are expected to warm into the 80s, except some upper 70s higher elevations. Tonight, the high pressure at the surface will keep light winds in place with mainly clear skies. Backdoor front expected to slide into northern Virginia by 12z Saturday and may push a few clouds toward the Shenandoah Valley but overall generally clear. Patchy fog in the river valleys possible in the west. Lows will vary from the mid 50s deeper valleys in the west to lower to mid 60s elsewhere.
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&& .SHORT TERM /SATURDAY THROUGH MONDAY NIGHT/... As of 345 AM EDT Friday... A high amplitude upper level ridge will be building over the eastern part of the country through the weekend. This will allow surface high pressure over central Canada to build southward and wedge down the east side of the Appalachians. After one last very warm day on Saturday, the wedge will surge into the region behind a backdoor front moving in from the northeast. Temperatures will be much cooler behind the front and guidance indicates a good deal of low level moisture and isentropic lift over the wedge. This looks to bring abundant cloud cover and some light precipitation to the region for Sunday and into the first part of next week. By Monday the axis of the upper ridge will move to our east and allow a large closed low over the Great Lakes region to push a cold front toward the region from the west. Southwest flow ahead of the front will continue to generate lift over the wedge, while the western and southern portions of the region on the fringes of the wedge may get into enough unstable air to support a slight chance of thunder. Thus, Monday looks to be another cloudy and cooler day with a chance for precipitation. Will continue the trend of lowering max temperatures for Sunday and Monday as the wedge looks to be solid and wet bulb temperatures are in the 60s so any precipitation into the wedge will be effective in holding temperatures down. So after temperatures on Saturday reach well into the 80s, locations east of the Blue Ridge will be looking at readings in the lower 70s by Monday with some warmer temps along the western and southern fringes. && .LONG TERM /TUESDAY THROUGH THURSDAY/... As of 345 AM EDT Friday... An upper level low over the Great Lakes will slowly push a cold front into the region Wednesday, then the front stalls just east of the Blue Ridge. With a blocking pattern in place and the upper low becomes cutoff from the steering flow per the 12Z GFS, the second half of the week could be very wet for the region. The Euro also stalls the next front over the area Wednesday but is booted to the east by Thursday. Needless to say, there is very little confidence in next week`s forecast. && .AVIATION /11Z FRIDAY THROUGH TUESDAY/...
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As of 713 AM EDT Friday... Fog at LWB/BCB will be gone by 13z with VFR expected the rest of the day. Should see the MVFR cigs at DAN clear out by 15Z. High pressure enters the area today and tonight with VFR expected along with light winds. A potential for fog in the valleys exists again late tonight at BCB/LWB. Question is how low to go. Will follow the trend of what happened this morning so going LIFR at LWB and IFR at BCB by 10z/24. Extended aviation discussion... VFR conditions will prevail through Saturday with high pressure in place. A back door front passes across late in the weekend into early next week which may bring sub VFR ceilings as an easterly flow sets up. These MVFR or lower ceilings may stay in place through Monday. Rainfall chances will stay low however, though some upslope component from the southeast could bring showers/rain to along the Blue Ridge south of Roanoke/Blacksburg Monday. A strong, but slow moving, cold front will be approaching the area from the west on Tuesday. Models have significant differences on the timing and location of this front.
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&& .RNK WATCHES/WARNINGS/ADVISORIES... VA...None. NC...None. WV...None. && $$ SYNOPSIS...WP NEAR TERM...WP SHORT TERM...MBS LONG TERM...RCS AVIATION...AMS/WP is the U.S. government's official web portal to all federal, state and local government web resources and services.