Area Forecast Discussion
Issued by NWS Blacksburg, VA

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000 FXUS61 KRNK 221920 AFDRNK Area Forecast Discussion National Weather Service Blacksburg VA 320 PM EDT Thu Sep 22 2016 .SYNOPSIS...
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Low pressure along the coast of South Carolina slides slowly north along a front through Friday with high pressure shifting over the Southern Appalachians. A backdoor cold front will approach from the north Friday into Saturday, then slide south across the region Saturday night. Canadian high pressure will move across southeast Canada and wedge down the east side of the appalachians starting Sunday.
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&& .NEAR TERM /THROUGH FRIDAY/...
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As of 320 PM EDT Thursday... Low pressure along the coastal boundary will slide north tonight into Friday. Meanwhile, the upper low weakens and opens up into Friday. At the same time, a cold front will approach us from the north. Northeast flow transporting moisture this afternoon into tonight resulting in clouds with isolated to scattered showers this afternoon into tonight mainly east of the Blue Ridge mountains. For tonight expecting showers to taper off or diminish with clear skies in the northwest to cloudy skies in the southeast. With less mixing and clear skies, patchy fog will form in the river valleys. Low temperatures tonight will range from the mid 50s in the northwest mountains to the mid 60s in the Piedmont. The upper low continues filling along the Carolina coast on Friday. With decreasing upper level support and shallower moisture, final expect the column to dry out for Friday. High temperatures on Friday will vary from the mid 70s in the mountains to the mid 80s in the Piedmont.
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&& .SHORT TERM /FRIDAY NIGHT THROUGH SUNDAY NIGHT/...
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As of 320 PM EDT Friday... The upper level low that has hovered over the southeastern US for the last several days will get pushed out to sea Friday night and Saturday. This will allow a back door cold front to slide south across the region Saturday night. Surface high pressure will then move across southeastern Canada and wedge down the east side of the Appalachians through Sunday. Even though the surface wedge boundary moves over the Carolinas, the associated theta-e boundary will stall across northern Virginia. With ample low level moisture and isentropic lift, gray and damp conditions are likely with light rain/drizzle, low clouds and fog Sunday and Sunday night. Temperatures will be a nightmare to forecast especially if the backdoor front is slow to move south Saturday night. Also, if the theta-e boundary is able to move farther south Sunday, less rain and clouds can be expected which could lead to warmer than forecasted temperatures Sunday. For this package, we will undercut guidance by 3F-6F based on Cold Air Damming (CAD) climatology for areas along and east of the Blue Ridge and close to normal in the Bluefield- Richlands area who will be on the fringe of the wedge.
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&& .LONG TERM /MONDAY THROUGH THURSDAY/...
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As of 300 PM EDT Friday... Upper level ridging across the east will make for slow progress with regards to any significant weather changes through the period. The wedge that will be in place on Sunday will erode some over the mountains, but hangs on east of the Blue Ridge into Monday night. 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.
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&& .AVIATION /19Z THURSDAY THROUGH TUESDAY/... As of 130 PM EDT Thursday... Isolated to scattered MVFR showers will move west across the region this afternoon into tonight. Otherwise, VFR conditions will prevail this afternoon into tonight. The best chance of MVFR conditions will occur in southeast portion of the forecast area. Pockets of MVFR/IFR fog will develop tonight with light winds and low level moisture. The DAN airport has the best chance of getting fog tonight into Friday morning. While in the west confidence is lower in LWB and BCB see any dense fog. winds will become light and variable tonight into Friday morning. Any morning fog and low clouds will lift by mid morning, returning all taf sites to VFR conditions Friday afternoon. Light winds will continue Friday with readings generally less than 10 knots. Medium confidence in ceilings,visibilities and winds during the TAF period. 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. Rainfall chances will stay low however. && .RNK WATCHES/WARNINGS/ADVISORIES... VA...None. NC...None. WV...None. && $$ SYNOPSIS...WP/KK NEAR TERM...KK SHORT TERM...RCS LONG TERM...RCS AVIATION...KK/WP

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