Area Forecast Discussion
Issued by NWS Blacksburg, VA

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000 FXUS61 KRNK 191350 AFDRNK Area Forecast Discussion National Weather Service Blacksburg VA 950 AM EDT Sun Mar 19 2017 .SYNOPSIS...
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High pressure will gradually build in from the west this afternoon and remain in place overnight into early Monday. The center of the high shifts south Monday afternoon in advance of a weak cold front that will drop southeast through the area on Tuesday before stalling. Low pressure riding along the front may bring another round of precipitation later Tuesday into Tuesday night, ahead of chilly high pressure that will build in from the north during midweek.
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&& .NEAR TERM /THROUGH TONIGHT/...
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As of 945 AM EDT Sunday... Water vapor showing the upper low slowly departing to the east this morning with lingering upslope low clouds and residual bands of snow showers persisting over parts of the mountains. However soundings depict plenty of dry air aloft which in tune with increasing subsidence, as high pressure starts to slide in under building heights, should gradually diminish western low clouds a bit espcly given more northerly flow. Only exception possibly over eastern sections where will start with more sun and then perhaps fill in strato-cu with heating on the backside of the departing cold pool. Thus bumped up clouds east of the Blue Ridge a bit for more partly cloudy flavor, while keeping more canopy in over the far west a while longer per latest Nam cloud/rh forecast. Cross sections/soundings also show moisture depth slowly shrinking across the upslope regions this morning under the drying aloft. Therefore expecting snow showers/flurries to fade by midday if not sooner as seen by most short term solutions. Appears the slot between the two, mainly over parts of northwest NC up along the Va foothills into Southside, will see more sun and the warmer temps overall. Otherwise remaining blustery and cool most sections with highs struggling to break into the 40s far west, and 50 elsewhere mountains pending degree of sunshine. Like mostly 50-55 east with perhaps a few late day readings closer to 60 in the MTV/MWK/DAN vicinity. Previous discussion as of 430 AM EDT Sunday... Closed upper low moves from southern Pennsylvania southeast to just off the Virginia coast by this afternoon. 500MB heights rise tonight as upper ridging builds over the eastern United States. At the surface high pressure over the western Great Lakes will move southeast and will be centered over the southern Appalachians by Monday morning. Will be starting out with a 35 to 40 knot low level jet. Surface and low level winds will turn the north and with daytime mixing will still be gusty through afternoon. Winds will diminish tonight as the high builds in. Stayed closer to warmer guidance for maximum temperatures today. Used more of a blend of MAV/MET guidance for lows tonight. Temperatures will drop quickly in the evening once winds decouple, plus most locations outside of southeast West Virginia will have a mostly clear sky but by late night cooling will be counteracted by the warm advection.
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&& .SHORT TERM /MONDAY THROUGH TUESDAY NIGHT/... As of 310 AM EDT Sunday... With a westerly flow aloft and 850 mb temperatures rising to near +10C, Monday will turn out warmer with highs from around 50 degrees in northwest Greenbrier to the mid 60s in the Southeast. An isolated shower is possible in the northwest Monday afternoon as support by ECMWF and GFS. Deepening moisture and clouds continue to increase Monday night with the potential for scattered showers. The best opportunity for rain will occur across the northwest and western portions with better moisture convergence to lighter pops out east under strong downsloping flow aloft. The combination of mixing and warming aloft should result in a mild Monday night with lows temperatures generally from the upper 30s in the northwest to the upper 40s in the Piedmont. Frontal boundary will drift into the area Tuesday and may linger across southern sections Tuesday night before finally getting shoved to the south via passing stronger shortwave energy to the north on Wednesday. A weak wave may develop along the boundary by Tuesday night which could result in more widespread precip into early Wednesday. The challenge of the forecast is the exact location and movement of low pressure Tuesday afternoon into Wednesday. Some models have the low farther south and others leaving moisture around with colder air bleeding in from the north at the end. The day 3 convective outlook has placed most of the CWA in general thunderstorms with a marginal threat for severe thunderstorms with hail and gusty winds just to our southwest, mostly in Tennessee. Leaned towards Superblend for pops with a period of likelys Tuesday afternoon into Tuesday night mainly southern/eastern half including some light snow far northwest toward daybreak Wednesday as deeper cold advection arrives. High temperatures Tuesday are warmer than Monday with readings from the mid 40s in the northwest to the lower 70s in the Piedmont. Low temperatures Tuesday night into Wednesday morning will range from the mid 20s in the northern mountains to the lower 40s in the Piedmont. && .LONG TERM /WEDNESDAY THROUGH SATURDAY/... As of 310 AM EDT Sunday... The upper trough Wednesday will slide east to just off the Atlantic coast Wednesday night into Thursday morning. High pressure will build southeast from the Great Lakes to the Mid Atlantic region. This high center will wedge south down the Mid-Atlantic coast Thursday into Thursday night. With some uncertainty, it appears to be a dry wedge into Thursday night. The High slides offshore later Thursday night allowing a weak warm front to shift north on Friday, in turn scouring the wedge under rebounding temps to more seasonal levels. Next round of shortwave energy heads out of the Rockies by the end of the week with an associated cold front approaching by next weekend. Timing of this boundary into the eastern ridging remains iffy but appears enough return of deep moisture to warrant a chance of showers mainly Saturday afternoon and overnight. Sunday will be cooler with scattered rain and snow showers. && .AVIATION /13Z SUNDAY THROUGH THURSDAY/... As of 730 AM EDT Sunday... Will see gusty winds across the mountains/foothills once mixing begins this morning, but will high pressure moving toward the area the wind will start to diminish this afternoon. The winds will decouple after sunset, becoming light and variable in the valleys. Scattered snow showers will continue in southeast West Virginia for most of the morning with occasional MVFR visibilities. Bufkit soundings showed the layer of low level moisture over the mountains lifting throughout the morning. Medium confidence that locations along and west of the Blue Ridge, including KBLF and KLWB will improve to VFR by noon with only a few light rain or snow showers left along the western slopes. VFR conditions are expected throughout the region tonight. Extended Aviation Discussion... High pressure building in on Monday should yield VFR all terminals to start the week. However moisture ahead of a cold front and associated weak low pressure may arrive by Monday night, with sub-VFR possible later Monday night in the mountains and in all areas Tuesday into Tuesday night before improving conditions back to VFR Wednesday. By Thursday high pressure will wedge in from the northeast so will stay VFR though increasing clouds are expected by afternoon, but should stay VFR. && .RNK WATCHES/WARNINGS/ADVISORIES... VA...None. NC...None. WV...None. && $$ SYNOPSIS...AL/JH NEAR TERM...AMS/JH SHORT TERM...KK LONG TERM...JH AVIATION...AMS/WP

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