Area Forecast Discussion
Issued by NWS Blacksburg, VA

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000 FXUS61 KRNK 121517 AFDRNK Area Forecast Discussion National Weather Service Blacksburg VA 1017 AM EST Tue Dec 12 2017 .SYNOPSIS...
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A strong cold front moves east of the area this afternoon, with snow showers and windy conditions following it mainly for the mountains. Strong northwest winds persist into early Wednesday before weak high pressure builds in. Another clipper moves in Wednesday night, followed by high pressure to finish out the week.
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&& .NEAR TERM /THROUGH TONIGHT/...
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As of 1015 AM EST Tuesday... Cold front now pushing toward the Blue Ridge should cross the rest of the region by early afternoon. Already seeing winds gusting to advisory levels over parts of the western mountains and expect this initial surge in winds to continue east with a period of stronger winds out to the lee of the Blue Ridge. However will keep going wind headlines in place and not expand or upgrade attm but something to monitor. Otherwise upstream snow showers behind the front remain slower to arrive given dry air per morning soundings and the lagging strong shortwave with the coldest air aloft. Latest upstream radar trends show increasing snow coverage approaching so bumped up pops northwest and extended east a bit given potential for spillover as instability and deeper upslope coincide as the boundary layer quickly cools. Bumped up temps some per current obs to start followed by falling readings across the region this afternoon. Otherwise no changes to current winter weather including wind chill headlines for now. Previous discussion as of 255 AM EST Tuesday... Keeping close to previous forecast but upping the ante a bit as models agree on more snow showers in the western slopes of WV than NC. Meanwhile, wind chills late tonight will dip to advisory levels over the mountains west of the Blue Ridge, so a wind chill advisory will be added to the mix. Remember, the wind chill advisory criteria for places like Roanoke and Lexington were raised to zero degrees compared to minus 5 degrees for the mountains, hence the advisory for these areas. Now on to the weather setup. Early this morning, the front extended from a 1002 MB lower near Pittsburgh, south into the southern Appalachians. Radar has been quiet with very light returns over far SW VA with no ground truth, with main precip staying along/north of the sfc low in wrn PA/NE Ohio into New York. High-res models are not favoring any precip along the front, and waiting on the main vort axis behind the front to arrive after 12z so will start to see some light snow showers moving into the mountains in the 7am-10am time frame, with better low level moisture also taking shape. At the moment will see best setup for snow showers from late morning into midday but then wave passes and should see stronger winds push in along with cold air advection as 8h temps fall from +2 east to -5C west at 7am, to -4C east to -11C west by early afternoon. Current wind headlines are good, though will see several periods of strong winds, and potential wind advisory level criteria being met in the higher ridges outside the current advisory, though it looks isolated, plus airmass will be well mixed with higher inversion heights. The more potent vort digging across the Great Lakes this morning tracks a little further north than previous solutions indicate going from the Ohio/WV/KY border at 18z today, to the VA foothills/piedmont by evening. This track will favor snow showers/flurries extending eastward this evening into the foothills, though winds and drier air will limit accumulation. Still a dusting here and there appears likely at least to the Blue Ridge, with the main accumulating snows over WV. Not as much further southwest into NC but will leave the winter wx advisory as is, with some isolated 3" amounts not out of the question near the TN/NC border and atop Mt Rogers. This wave pivots out by midnight with snow showers fading after midnight, so again best accumulating snows will be late this afternoon/evening. Compounding the winds on top and blowing snow is likely, especially the WV mountains, so reduced visibilities will be common at times. Given snowfall of 2-3 inches further south along the slopes of Summers/Mercer WV have expanded the winter wx advisory for them as well. Temperatures this morning will start in the upper 20s to upper 30s, then temperatures tank in the mountains in the afternoon to the 20s, with the piedmont steady or falling late into the 30s after maxing out in the 40s/maybe near 50s far southeast. Tonight, strong cold air advection persists with wind staying up. With temperatures falling into the teens, wind chills will be as low as zero to 10 below along/west of the Blue Ridge. Wind chill advisories will be in effect for these areas from midnight until around 9am Wednesday. Looking at skies clearing this afternoon in the piedmont then from east to west overnight with snow ending by dawn.
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&& .SHORT TERM /WEDNESDAY THROUGH FRIDAY NIGHT/... As of 200 AM EST Tuesday... Strong winds/gusts will continue into early Wednesday morning prior to the pressure gradient slackening rapidly during the afternoon hours. Upslope snow showers across portions of southeast West Virginia will decrease in coverage during the morning, ending by the early afternoon. By late Wednesday afternoon into Wednesday evening, look for low level winds to back southwest or west in advance of the next approaching upper level shortwave trough. Guidance is offering a solution that brings an associated temporary increase in the low level jet again across the region, with values similar to, or slightly higher than, those anticipated tonight. Could be another time period to watch for potential wind headlines. The the bulk of the energy associated with the disturbance will remain north of the area. However, enough shallow low level moisture with a strong upslope component will be additional light measurable snowfall for parts of southeast West Virginia, with isolated snow showers as far east as the crest of the Blue Ridge from Virginia into North Carolina. By Thursday afternoon into Thursday night, high pressure will be building into the area all the while winds decrease once again. The axis of this high will shift east of the region during the day Friday. The result will be a dry forecast Thursday into Thursday night. On Friday, we will be watching yet another Great Lakes shortwave trough progress west to east, north of the region. Anticipate another period of upslope snow showers across mainly southeast West Virginia, south into the Northern Mountains of North Carolina, with limited coverage east to the crest of the Blue Ridge. Upslope snow showers in the west will continue Friday night as a decent northwest low level trajectory continues. During this period of the forecast temperatures are expected to trend milder through Thursday, with decreasing values on Friday. Eastern sections of the region will experience little if any precipitation, and limited cloud cover. && .LONG TERM /SATURDAY THROUGH MONDAY/... As of 319 PM EST Monday... Upper flow will flatten over the weekend into early next week. Heights build allowing for some temperature moderation on Saturday under warmer westerly flow which should push most into the 40s. This in advance of yet another system swinging northeast out of the southern plains that will link with the next upstream cold front and bring rain showers into the area late Sunday into Monday before colder drier air follows later on Day 7. Appears most precip will be liquid given warming aloft ahead of the system Sunday night with only perhaps some snow showers at the end far west Monday morning. && .AVIATION /15Z TUESDAY THROUGH SATURDAY/... As of 621 AM EST Tuesday... Expect cigs/vsbys to fall to MVFR to at times IFR later this morning in BLF/LWB as snow showers associated with a clipper moves in. Further east should stay VFR but cannot rule out a stray band of snow showers over BCB/ROA this afternoon/evening. Will see snow showers fade at BLF/LWB this evening with VFR returning. Winds will stay pretty gusty from the west-northwest through most of the period. Medium to high confidence all parameters. Extended Discussion... Weak high pressure builds in Wednesday followed by another weaker clipper Thursday that passes by mostly to our north. Another more significant clipper system will arrive by Friday into Saturday, with gusty winds and mountain showers, thus the potential for periods of sub-VFR conditions. && .RNK WATCHES/WARNINGS/ADVISORIES... VA...Wind Chill Advisory from midnight tonight to 9 AM EST Wednesday for VAZ007-009>020-022>024. Wind Advisory until 7 AM EST Wednesday for VAZ015>017-022. NC...Wind Chill Advisory from midnight tonight to 9 AM EST Wednesday for NCZ001-002-018. Wind Advisory until 7 AM EST Wednesday for NCZ001-002-018. Winter Weather Advisory until 7 AM EST Wednesday for NCZ001- 018. WV...Wind Chill Advisory from midnight tonight to 9 AM EST Wednesday for WVZ042>044-507-508. Winter Weather Advisory until 7 AM EST Wednesday for WVZ042- 043-508. && $$ SYNOPSIS...JH/WP NEAR TERM...JH/WP SHORT TERM...DS LONG TERM...JH AVIATION...RAB/WP

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