Area Forecast Discussion
Issued by NWS Blacksburg, VA

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000 FXUS61 KRNK 160503 AFDRNK Area Forecast Discussion National Weather Service Blacksburg VA 1203 AM EST Tue Jan 16 2018 .SYNOPSIS... High pressure will cover the Mid Atlantic region tonight. A low pressure system will track across Wisconsin into Ontario through Tuesday, which will bring a cold front into western Virginia and North Carolina on Tuesday. Low pressure developing along the front will move offshore as high pressure builds into the region on Wednesday. && .NEAR TERM /THROUGH TODAY/... As of 730 PM EST Monday... A Winter Weather Advisory is in effect for a large Geographic region, mainly west of the Appalachian Divide during the near term part of the forecast...with WV and far western VA subject to some modest accumulation of snow during the day Tuesday. Current advisories are aligned with with a cold front which is making its way across the OH/TN Valleys. The evening weather map showed an occluded area of low pressure over the great lakes with a trailing front bisecting the OH valley, and trailing southwest into western TN and Mid-MS River Valley. Moisture has been limited to a corridor just behind the front (Anafront) with some light-modest snow accumulations...1-4 inches seems to be the common theme. As the front approaches the western slopes of the Appalachians overnight look for increasing clouds. The movement of the front has been relatively slow, so do not look for any accumulating snow within our part of the world until daybreak, and then mainly confined to WV and far western VA during the morning. The front is forecast to cross the mountains during the day, light snow trying to spill over the mountains as we transition through the day. Attm, the airmass east of the Blue Ridge is dry with dewpoints in the single digits and teens, so look for it to take most of the day before snow is able to make it east of the Blue Ridge...start times near the Blue Ridge not occurring until mid-late afternoon, and taking until evening (after sunset) for Southside VA and Piedmont of NC. Low temperatures tonight will be dependent on how quick the clouds roll-in, ranging from the mid teens to the lower 20s. Clouds will also impact the temperatures Tuesday, with readings struggling to climb above freezing west of the Blue Ridge, and potentially warming to 40 degrees across Southside VA and the Piedmont of NC where some sun expected first half of the day. With precip mainly confined to areas behind the front, and front not expected to cross the Blue Ridge until Tuesday evening, any accumulating snow prior too sunset Tuesday should be mainly confined to areas west of the Blue Ridge, with the greatest amounts focused on the western slopes of the Appalachians from western Greenbrier into Bluefield and Tazewell...amounts generally 1-4 inches...ranging from 1 inch in the eastern New River Valley to as much as 3-4 in the western NRV closer to Bland and Tazewell and up into parts of WV. The NW NC mountains will also pick up and inch or two. && .SHORT TERM /TONIGHT THROUGH THURSDAY NIGHT/... As of 800 PM EST Monday... The cold front will move east and into the piedmont of VA/NC by midnight Tuesday night...a wave of low pressure developing along the front and moving northeast and into New England Wednesday. The progression of the front will be slowed by the formation of this area of low pressure and this is where the forecast challenge resides with respect to how much QPF/snow will be generated as the low forms and then moves northeast. Of greatest certainty will be the impact it will have on New England once the low gets wound-up on Wednesday...yeilding moderate-heavy snow for coastal New England. Our geographic area on the otherhand hinges on how fast the front moves east of the area vs. how fast the area of low pressure develops along the front before it exits the area...model solutions ranging from little or no snow to as much as 1-4 inches for parts of central and eastern VA/NC. Southside VA (LYH-DAN) and into the northern Piedmont of NC (Eden-Yanceyville) will be on the western edge of where the better dynamic lift and snow production will occur with the developing wave of low pressure. At some point, Winter Weather Advisories may be needed for parts of central/eastern VA/NC, but the event is still 24-36 hours from fruition...any substantial snow accumulation for areas east of LYH-DAN occurring mainly after midnight Tuesday night. With the passage of the front, arctic air will pour back into the forecast area on northwest winds. Some additional upslope snowfall in the form of snow showers and flurries will occur in the WV/VA/NC mountains...tacking on another inch or two for places like Northwest Greenbrier, bringing storm total closer to 5 inches for places like Rupert and Quinwood, WV). Temperatures Wednesday morning will drop down into the 10F-15F range across the mountains with wind chills in the single digits. East of the Blue Ridge will have lows in the 20s and wind chills in the teens. Temperatures will not warm much Wednesday, but the winds will increase with pressure rises behind the front. Cold temperatures and breezy/gusty conditions remain Wednesday night to send wind chill values to near zero across the mountains, single digits out east. If the forecast holds, wind chill advisories will be issued once the advisory for snow ends on Wednesday. Less wind expected Thursday as high pressure builds over the region. Afternoon high temperatures rebound into the 30s. Under good radiational cooling, temperatures will fall into the teens Thursday night to lower 20s east. If snow pack remains on the ground, temperatures will be colder, but with little wind, wind chill values will stay above zero. && .LONG TERM /FRIDAY THROUGH MONDAY/... As of 225 PM EST Monday... Despite a lee surface trough taking residence over the piedmont Friday and Saturday, high pressure will keep the region dry into Sunday night. Temperature will warm to normal levels on Friday then above normal for the weekend. With the above normal temperatures, the front Sunday night into Monday will be all rain with a brief period of upslope snow showers on the back side Monday night. && .AVIATION /05Z TUESDAY THROUGH SATURDAY/...
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As of 1205 AM EST Tuesday... VFR conditions anticipated for the remainder of the night. Winds light. Cold Front approaching from the northwest will bring increasing mid/upper level cloudiness to the central Appalachians during the overnight any precipitation remaining west of the Appalachian divide. During the day Tuesday, cloud bases will lower, MVFR cigs/vsbys developing across the mountains. IFR vsbys due to light snow are likely from KBLF-KLWB northward along the spine of the Appalachians. As the front crosses the mountains Tuesday evening, a wave of low pressure is forecast to develop and ripple northeast along the front Tuesday night and early Wednesday. This will bring a period of light snow to areas east of the Blue Ridge and into the eastern Mid-Atlantic Tuesday night and early Wednesday with snow accumulations of 1-3 inches. Greater accumulations are expected for coastal New England. This will likely impact air traffic Wednesday. Medium confidence in Ceilings,visibilities and winds during the taf period. Extended Discussion... After frontal passage, a reinforcing blast of arctic air will move into the region. Dry air will restore sky conditions to VFR, however wind will become a factor for some aviation interests Wednesday night into Thursday morning. VFR conditions should persist into the weekend with warming temperatures. Moisture will return to west Sunday night into Monday.
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&& .RNK WATCHES/WARNINGS/ADVISORIES...
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VA...Winter Weather Advisory from 10 AM this morning to 10 AM EST Wednesday for VAZ007-009-010. NC...None. WV...Winter Weather Advisory from 10 AM this morning to 10 AM EST Wednesday for WVZ042>044-507-508.
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&& $$ SYNOPSIS...AMS/KK NEAR TERM...PM SHORT TERM...PM/RCS LONG TERM...RCS AVIATION...PM

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