Area Forecast Discussion
Issued by NWS Blacksburg, VA

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000 FXUS61 KRNK 131504 AFDRNK Area Forecast Discussion National Weather Service Blacksburg VA 1004 AM EST Sat Jan 13 2018 .SYNOPSIS... A strong cold front will exit east of the region this morning resulting in much colder air on strong northwest winds into this afternoon. High pressure will build in from the northwest tonight through Sunday and remain north of the region into Monday. A second surge of Arctic air comes in behind a cold front that passes through the area Monday night and Tuesday. && .NEAR TERM /THROUGH TONIGHT/...
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As of 1004 AM EST Saturday... The winter weather advisory was allow to expire this morning because the threat for widespread travel problems has ended. Isolated icy spots may be possible on roadways especially in shady areas and on bridges and overpasses. Wind chill advisory has been posted for western Greenbrier county until 10 am Sunday where the combination of wind and temperatures will create very cold wind chills. HiresW-arw-east, HRRR and NAM show snow showers and snow flurries taper off by 18z. Any accumulating snow will be less than an inch and will remain confined over the far west with limited upslope in the wake of the passing upper system given a more northerly trajectory by afternoon. High pressure will build east out of the ohio valley this afternoon into tonight. For the morning update, modified temperatures and dew points with latest surface obs, their trends and shaped towards GLAMP. Raise high a few degrees in the south to blend up better with RAH and AKQ. More changes later this morning. As of 245 AM EST Saturday... Strong cold front now heading east of the Blue Ridge should clear the region prior to daybreak. Boundary continues to be followed by a quick surge of cold advection with temperatures rapidly dropping through the 30s and into the 20s west in a short period. This has been fast enough to catch lingering moisture over the west resulting in a transition to snow/snow showers including freezing of whats left of residual moisture in spots. Appears based on current radar trends and short term guidance will continue to see this trend linger into early this morning with some snow showers/flurries spilling out toward the Blue Ridge per strong northwest flow. However appears most accumulating snow of an inch or so will remain confined over the far west with limited upslope in the wake of the passing upper system given a more northerly trajectory by afternoon. Also undercutting of very dry air should cut off flurries a bit faster so leaving the current advisory in place while cutting off pops around midday northwest if not sooner. Also expect to see some lingering showers north/east early this morning and perhaps a few sprinkles east through midday as a more northerly trajectory may tend to trap clouds out east given less/weaker downsloping. Gusty northwest winds also a concern over the west per strong pressure rises and a lowering inversion. However the 85h jet remains rather weak outside of early this morning so will wrap wind mention into the winter wx advisory early on. Otherwise expect a gradual decrease in clouds by later this afternoon as subsidence and very dry air win out. Temps to continue to fall this morning as strong cold advection prevails before finally steadying out mainly in the 20s mountains and 30s to low 40s out east. This combined with the wind will keep wind chills in the single digits and below zero across some of the highest elevations. Upper trough to pivot across from the west overnight with another digging shortwave perhaps keeping some upslope clouds west espcly early on. Otherwise cold high pressure will build in from the northwest overnight allowing for diminishing winds late under mainly clear skies. Air mass not quite as cold as last week but enough for some single digit lows mountains and overall teens to low 20s southeast. Wind chills likely below criteria at high elevations mainly western Greenbrier if winds stay up, but not enough to hoist another headline there at this point.
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&& .SHORT TERM /SUNDAY THROUGH TUESDAY NIGHT/... As of 455 AM EST Saturday... Very cold, much below normal temperatures will return this period as a deep upper low digs south through the Great Lakes into the eastern U.S. once again allowing a surge of -20C air to return to the area, with another reinforcing surge ahead for midweek. Although it does not appear that this mass of Arctic air will be as deep into the southern states, thus likely not lingering as long due to a more transient upper trough/zonal flow, the degree of the cold air is quite similar to the last couple of outbreaks, namely down into the -20C to -22C range once again. This will equate to several chances to see single digits and teens for low temperatures next week once again. Sunday will be mostly sunny and dry with limited to no continuing upslope snow showers. Monday should also be dry with a very slight moderation in temperatures as the flow aloft briefly becomes southwest in advance of the next surge of Arctic air. That will arrive late Monday night into Tuesday morning. Enough moisture may be present combined with strong cold advection and dynamics to squeeze out a period of light snow across mainly the Alleghanys, with the typical 1 inch or so of snow showers possible in areas like western Greenbrier. Although winds will be strong and gusty for a period of time, they will remain below advisory criteria. Maximum temperatures through the period will be mainly in the 20s mountains, 30s west of the Blue Ridge, with low temperatures dropping back into the single digits deeper mountain valleys and the teens most elsewhere to around 20 parts of the Piedmont. Sunday and Monday morning will bring the coldest temperatures for this period. && .LONG TERM /WEDNESDAY THROUGH FRIDAY/... As of 515 AM EST Saturday... As noted above, we will not see the deep northeast U.S. upper trough linger for two weeks like it did during the holidays and into the first part of the year. The trough is projected to lift out fairly quickly during the Thursday/Friday time frame. While there are some indication via the ECMWF that a coastal low pressure area could develop off the VA/NC coast with this system, the ECMWF has gradually been trending away from this and more toward the more progressive/faster/drier GFS, which suggests the only precipitation with the midweek system will be a brief period of showers/light snow along the front, followed by limited upslope snow showers. The air mass behind this cold front will be the coldest of the week, thus we should see morning temperatures bottom out in the 5-10 range Wed and Thu morning, with only a slight moderation into Friday. After highs will remain below freezing in most areas, especially west of the Blue Ridge, during the later half of the week. Temperatures will moderate considerably by the weekend as the upper trough lifts out of the area. Winds chills will likely be one of the greater concerns next week, especially Wed and Thu morning, when areas west of the Blue Ridge and especially across the Alleghanys will have the potential to see wind chills as cold as -5 to -10. This has been highlighted in the HWO for now. Summary of extended periods...Well below normal temperatures, below normal precipitation...Very cold and mostly dry. && .AVIATION /15Z SATURDAY THROUGH WEDNESDAY/... As of 600 AM EST Saturday... Cold front will continue to push east of the region this morning allowing for increasing northwest flow over the region today. Cloud bases will remain mostly VFR east of the Blue Ridge, but remain MVFR to OCNL IFR across the mountains this morning where low level moisture will linger. This will also result in periods of snow showers mainly west of the Blue Ridge with intervals of sub-VFR vsbys, mainly KBLF/KLWB this morning. Snow showers/flurries should taper off this afternoon while high end MVFR to low VFR bases persist over the mountains for much of the afternoon. Northwest winds will remain strong through much of the day with gusts perhaps reaching 30-35 kts espcly along the KBLF-KROA corridor with overall 15-25 kts elsewhere including eastern locations. Any residual clouds should fade tonight as northwest winds slowly diminish ahead of high pressure building in from the northwest. Extended Discussion... VFR across the region Sunday and Monday under high pressure. MVFR snow showers are possible Tuesday and Wednesday from a clipper system. This will lead to another surge of Arctic air. && .RNK WATCHES/WARNINGS/ADVISORIES...
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VA...Winter Weather Advisory until 10 AM EST this morning for VAZ007-009>020. NC...Winter Weather Advisory until 10 AM EST this morning for NCZ001-002-018. WV...Winter Weather Advisory until 10 AM EST this morning for WVZ042>044-507-508. Wind Chill Advisory until 10 AM EST Sunday for WVZ508.
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&& $$ SYNOPSIS...JH NEAR TERM...JH/KK SHORT TERM...RAB LONG TERM...RAB AVIATION...JH/PM

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