Area Forecast Discussion
Issued by NWS Blacksburg, VA

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000 FXUS61 KRNK 151141 AFDRNK Area Forecast Discussion National Weather Service Blacksburg VA 641 AM EST Mon Jan 15 2018 .SYNOPSIS... High pressure will cover the Mid Atlantic region today and tonight. A low pressure system will track across Wisconsin into Ontario today 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 TONIGHT/... As of 305 AM EST Monday... Warm front with mid and high level clouds crosses the Ohio Valley this morning. Clouds will reach West Virginia and Virginia around 12Z/7AM. Models show a brief break in the clouds this afternoon before deeper moisture ahead of the approaching cold front arrives this evening. Will be slowing down arrival of snow late tonight closer to 11Z/6AM. No significant adjustments to temperature forecast today or tonight. && .SHORT TERM /TUESDAY THROUGH THURSDAY NIGHT/... As of 430 AM EST Monday... The main focus during this period will be on a fast moving clipper-type system tracking from the western Great Lakes southeast into the Mid-Atlantic. Although surface moisture is greatly limited with the Gulf blocked by remnant Arctic high pressure, strong dynamics as the upper trough sweeps southeast through the region Tuesday night into Wednesday and takes on a negative tilt will bring enough lift and subsequent strong low- level cold advection to bring a period of snow to the region. There are essentially two parts to this system. The first round of snow, mainly in the 1-2 inch range will be upslope enhanced across the Alleghanys and into far southwest VA and northwest NC to a lesser extent. As the system crosses east of the Alleghany front, it will lose some of its moisture with downsloping. However, surface low pressure will track northeast from Georgia along the Arctic front, slowing the fronts forward progress and also inducing a coastal low off the Mid-Atlantic coast. This will begin to enhance snowfall again across areas east of the Blue Ridge as we get into Wednesday. The system will race quickly off to the northeast, so the better coastal associated snowfall will be to our northeast across the LWX and AKQ CWAs. Given expected QPF of mostly 0.10 inch or less, but high snow/liquid ratios on the order of 20/1 or greater given the very cold, dry air that will be in place, 1-2 inches of snow are possible across much of the CWA. The heaviest amounts with the storm system proper will be across the far northeastern parts of the CWA, with near 3 inches possible across Appomattox, Buckingham, and Amherst counties, with 2-3 inches possible in the Lynchburg area. Western counties will also have the opportunity for 1-2 inches of snow as the storm system first enters the CWA. The ROA/BCB/LWB areas may see the least snow with this system as it transitions from a positive tilted upper low with few low-level features to a negatively tilted upper low and coastal low. At this point, projected snow amounts in the east are just under advisory criteria, but given morning/weekday timing and potential 3 inch amounts some eastern areas, including LYH, feel that we will most certainly be putting out a Winter Weather Advisory with later forecast packages for areas east of HSP- ROA-MTV. Western areas snow amounts appear to stay under advisory criteria, but will be close in a few spots. The good news is that with the entire atmospheric column remains below 0C/32F, we won`t have to worry about freezing rain and sleet with this event. Temperatures will remain unseasonably cold through this period and for areas west of the Blue Ridge well below freezing much of the period. A core of -24C air that originates from south central Canada moves toward Kansas City Tue evening and then toward the Mid-Atlantic by Wed evening. This will yield single digits in the west to teens in the east both Wed and Thu mornings. Wind chills will be an issue both mornings west of the Blue Ridge with the potential for -15F western Greenbrier and 0 to -10 elsewhere west of the Blue Ridge. Will continue to highlight both the snow potential and the wind chill issues in the HWO with no headlines being issued at this point. && .LONG TERM /FRIDAY THROUGH SUNDAY/... As of 445 AM EST Monday... A much welcomed transition to warmer temperatures can be expected late in the week and over the weekend as the upper atmospheric pattern transitions from the one of roughly the past three weeks of an eastern U.S. trough/western U.S. ridge to a western U.S. trough and broad eastern U.S. ridge anchored primarily across the southeast states. On Friday, a fast moving compact short wave is projected to track across the Ohio Valley toward New England. At this point, it appears this feature will have little to no effect on our weather other than a minor setback in the warmup. Upper heights will rise significantly over the weekend and 850mb temperatures will warm substantially from readings of -16C Thursday to +12C as quickly as Saturday! The Friday feature will be shortlived with the area resuming a transition to greater ridging across the eastern third of the country. Look for dry weather and temperatures continuing to moderate heading into the weekend. By Sunday, a deepening upper low is progged to be positioned over, or just west of, the Upper Mississippi Valley, with its associated cold front approaching our region. The WV/VA/NC area will remain within a strong southwest warm air advection flow ahead of the cold front. Some light patchy rain will be possible during the day within a region of insentropic lift. Temperatures will continue to trend milder, alleviating any threat of winter precipitation. Through this period of the forecast, gradual warming is forecast. On Thursday, look for temperatures to average five to ten degrees below normal. However, but Sunday, temperatures are expected to average ten degrees above average. && .AVIATION /12Z MONDAY THROUGH FRIDAY/...
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As of 625 AM EST Monday... High confidence of VFR conditions through the TAF period as the cold, dry, high pressure covers the Mid Atlantic region. Low pressure crossing from Wisconsin to Ontario will bring a warm front through the Ohio Valley with mid and high clouds spreading across West Virginia and Virginia this morning. Extended Discussion... The low over the Great Lakes will push a cold front through the region on Tuesday. This should lead to sub- VFR ceilings and vis with some light snow Tuesday in the mountains and Tuesday afternoon through Wednesday morning east of the Blue Ridge. Light snow accumulations are likely at KDAN and KLYH. 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.
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&& .RNK WATCHES/WARNINGS/ADVISORIES... VA...None. NC...None. WV...None. && $$ SYNOPSIS...AMS NEAR TERM...AMS SHORT TERM...RAB LONG TERM...RAB AVIATION...AMS/PM

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