Area Forecast Discussion
Issued by NWS Blacksburg, VA

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000 FXUS61 KRNK 152123 AFDRNK Area Forecast Discussion National Weather Service Blacksburg VA 423 PM EST Thu Feb 15 2018 .SYNOPSIS...
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A broad area of high pressure aloft will remain over the Gulf of Mexico for the next several days. Meanwhile, a series of storm systems will track from west to east across the central and northern parts of the U.S., keeping an active weather pattern in place for much of the region well into next week. One such system will affect the area over the weekend, and a couple more slated for next week. Temperatures will be well above normal much of the period with the exception of the weekend when a surge of Canadian air will pass through the area.
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&& .NEAR TERM /THROUGH FRIDAY/...
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As of 220 PM EST Thursday... A stalled warm front sits over the Ohio Valley (CHI-PBZ) and will be the focus for thunderstorms this afternoon. A cold front will wash out the warm front this evening and slowly move to the south, crossing over the mountains Friday morning, then into North Carolina by late afternoon. Showers associated with this front will mainly be along and behind the boundary (anafront). HiRes models are showing a thin line of convective showers that may contain a few thunderstorms. None of these thunderstorms are expected to become severe. The highest 24 hour rainfall amounts ending at 7PM Friday will be along western slopes (half to three quarters of an inch). Winds aloft become westerly quickly behind the front, therefore rainfall amounts will be less along the Blue Ridge into the piedmont (one to two tenths). Majority of the rain along and east of the Blue Ridge will come from the line of convective showers with the front. Ahead of the front, southwest winds will remain breezy into tonight. Quick pressure rises following the frontal passage will bring a brief period (1-3 hrs) of gusty winds from the northwest. The warm, well above normal temperatures will continue until the front moves south of the area tomorrow afternoon. Overnight temperatures in the mid 50s to lower 60s will likely set records (warm lows) at BLF/ROA. Other climatic sites may also tie or set records, but confidence is lower due to the possibilities of weaker winds and clearing skies overnight. Similar temperatures tomorrow as today for areas south of hwy 460. Temperatures to the north will be influenced by the front tracking over the region tomorrow. If the front is held up, similar temperatures are possible, but expected them to be cooler by 5F to 8F than yesterday.
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&& .SHORT TERM /FRIDAY NIGHT THROUGH SUNDAY NIGHT/...
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As of 330 PM EST Thursday... Complex weather set-up for the weekend will bring threat for a wintry mix to parts of the region. The cold front which crosses the area Friday will stall over the southern Appalachians Friday night. In its wake, a cold wedge of high pressure will build into the forecast area with falling temperatures Friday night into Saturday. The center of the high will pass across Pennsylvania with the coldest air remaining to our north, however position of the high suggests classic cold air damming set-up for the Mid-Atlantic with cold wedge emanating down the east side of the Appalachians. Frontal boundary across the southern states will become the focus for a wave of low pressure to develop and move northeast into the Tennessee Valley Saturday. Moisture associated with this feature is forecast to spread rapidly northeast and overspreading our CWA during the day. As the moisture encounters the colder air across our region, a myriad of precipitation types are anticipated, with primarily rain south of the VA/NC border, and mixed precip across the Virginias. Onset looks to be around daybreak for our North Carolina counties and closer to the noon hour for areas north of 460 in VA/WV. Forecast soundings suggest mixed snow and sleet at the onset will transition over to freezing rain or rain, with highest snow/sleet amounts occurring north of Roanoke across the VA Highlands and into the mountains of eastern WVA. A corridor of freezing rain is likely right against the Blue Ridge from Roanoke to the the NC/VA border and including parts of the New River and Greenbrier valleys and into the foothills of Bedford...Franklin...Patrick counties. South and east of Danville temperatures appear they will be warm enough for all rain. Forecast QPF is between a quarter and a half inch, most of which falls in a 12 hour window between Noon Saturday and midnight Saturday night. Attm will focus greatest snowfall amounts from Greenbrier WV to Bath and Rockbridge counties in VA where 1 to 3 inches seems like a reasonable forecast since some transition to sleet and freezing rain is likely to rob this area from seeing all snow accumulation. Elsewhere snow/sleet amounts favor an inch or less, but there will be considerable more rain and freezing rain with glaze accumulation where temperatures maintain values of 32 or less. Mesoscale models suggest temperatures will fall through the day Saturday with corridor of 28-32 deg F developing right along the Blue Ridge all the way to the NC/VA border. Assuming at least a quarter inch of QPF would yield 2 tenths of ice accretion within this corridor. As for impacts, current ground temperatures are warm. Temperatures Thursday reached the 60s/70s, which has boosted the subsurface temperatures into the 40s. Even with air temperatures expected to dip back to near freezing, it will be hard to get rain to refreeze on the ground. That said, think impacts from freezing rain will be to mainly to elevated surfaces...trees, wires etc...which we will have to monitor closely since accumulations of greater than a quarter inch would down tree limbs and result in potential for power outages. Will highlight this threat in the Hazardous Weather Outlook, and if models continue along this trend, will likely need winter weather advisories for parts of our region for Saturday afternoon and evening. As already mentioned, temperatures will likely fall during the day Saturday, then level off Saturday night or even rise slightly in the western counties as warmer air tries to work its way in from the TN Valley. On Sunday we will see a transition back to warming temperatures as clouds depart with brief drying supporting increasing sunshine.
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&& .LONG TERM /MONDAY THROUGH THURSDAY/...
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As of 400 PM EST Thursday... Yet another disturbance is expected to cross the forecast area Monday with another round of precipitation. Temperatures may be near critical for a few hours early Monday morning, but think increasing cloudiness Sunday night ahead of Mondays rain event will keep temperatures from radiating, thus supporting temperatures above freezing areawide. For now will entertain mainly rain. Any sort of wedge Monday is expected to break and give way to much warmer temperatures for the middle of the week. Warm front will move north of the area placing our region under warm, but moist southerly flow. Models suggest temperatures will climb back well into the 60s and testing 70 again for southside VA and into the piedmont of NC. Rain chances will increase again by Thursday as yet another disturbance approaches from the southwest.
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&& .AVIATION /20Z THURSDAY THROUGH TUESDAY/... As of 1230 PM EST Thursday... MVFR ceilings across the mountains will slowly improve to VFR this afternoon. Sites east of the Blue Ridge are already at VFR. VFR conditions will continue into tonight. Ceilings will lower to MVFR as the front approaches from the northwest. Sub-MVFR ceilings and visibilities are possible as the front treks across the region Friday. Breezy and gusty southwest-west winds will continue until the front passes during the day Friday. Winds will remain breezy and gusty following the frontal passage, but out of the northwest. Extended Aviation Discussion... Behind the front going into late Friday and Saturday, strong northwest winds will develop as colder air rushes back in. Conditions look to briefly improve Friday night as high pressure builds in behind the front before another disturbance arrives from the southwest Saturday afternoon/evening. This feature looks to bring another round of sub-VFR cigs/vsbys in rain or mixed precipitation before VFR returns again on Sunday under weak high pressure. The cold/wintry weather will be brief as a warm front lifts back north into the area on Monday with another round of sub- VFR, especially western areas and mountains. && .CLIMATE...
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As of 220 PM EST Thursday... Thursday 02/15/2018 Record Highs... Site MaxT Year HiMin Year KBLF 72 1990 54 1990 KDAN 76 1990 57 1949 KLYH 77 1989 55 1949 KROA 79 1989 55 2001 KRNK 66 1990 46 1990 Thursday Record High Minimums... Site HiMin Year KROA 55 2001 KLYH 55 1949 KDAN 57 1949 KBLF 54 1990 KRNK 46 1990
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&& .RNK WATCHES/WARNINGS/ADVISORIES... VA...None. NC...None. WV...None. && $$ SYNOPSIS...RCS NEAR TERM...RCS SHORT TERM...PM LONG TERM...PM AVIATION...RAB/RCS CLIMATE...KK

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