Area Forecast Discussion
Issued by NWS Blacksburg, VA

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000 FXUS61 KRNK 131406 AFDRNK Area Forecast Discussion National Weather Service Blacksburg VA 906 AM EST Wed Dec 13 2017 .SYNOPSIS... Arctic air encompasses the region this morning. Strong northwest winds will persist early this morning before diminishing. Another clipper will cross the Great Lakes and Ohio Valley tonight and early Thursday with another round of elevated wind speeds, although temperatures will not be as cold. && .NEAR TERM /THROUGH TONIGHT/...
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As of 905 AM EST Wednesday...Update to cancel the Wind Chill Advisory and issue a updated forecast refresh. Changes however were negligible. It is still quite cold out with northwesterly winds still resulting in lowest wind chills between -3 and 0 at Bluefield and Hillsville respectively. Sunshine will help boost temperatures and raise wind chill values further. Should also see some improvement in road conditions by late morning as patches of snow and ice melt as the sun heats the pavement. Aside from accounting from current observations and blending in with expected near-term trends, forecast looks good. Previous discussion issued at 330 AM... Arctic airmass over the region is resulting in temperatures in the teens. Winds are gradually beginning to diminish, but still resulting in single and sub-single digit wind chills. Snow showers across the mountains yesterday and last night have left a dusting to as much as 2 inches of new accumulation. The wind has drifted quite a bit of this onto the roads, and with temperatures in the teens its making for some icy travel per road treatments not being very effective at these temperatures. If we can grin and bear it through lunch-time, then we should see a market improvement for the afternoon. Coldest of the airmass is already in place with 850 MB Temps of m15 deg C. That means its all uphill from here, with models indicating warming throughout the day and 850 mb readings near 0 deg C by the end of the day. Temperatures at the surface will still struggle to get much above freezing for high temperatures, but with full sunshine it will hopefully allow road treatments in the mountains to be a lot more effective at clearing some of the ice and snow from the highways. East of the Blue ridge where little or no snow occurred yesterday, the sun should allow temperatures to make a run for 40 degrees by mid afternoon. Another fast moving upper level disturbance (clipper front) can be seen on the water vapor imagery entering the upper Midwest this morning. This clipper is forecast to move across the Great Lakes and Ohio Valley, farther north than the last system. Greatest pressure rises with this feature are expected to pass north of our region, never the less, we will get a surge of wind tonight and early Thursday. Forecast 850mb winds of 50kts may require need for a wind advisory for parts of our region tonight, but will allow existing advisories to play out before issuing any new headlines. As for potential snow with tonight`s clipper, it looks to be a lot less compared to Tuesday`s event. Depth of the moisture profile on Tuesday was all the way up to 8000 ft. Tonight`s forecast depth is only to 4500 ft which suggests any accumulation will be confined to the highlands of WV with trace amounts as far south as the high country of NC. For now will go with 1-2 inches of new accumulation for NW Greenbrier and mainly flurries elsewhere. With the passage of the clipper, the 850 MB temperatures slip back to about m5 deg C. This suggests a relatively milder night with lows in the 20s to around 30 (compared to the teens from last night).
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&& .SHORT TERM /THURSDAY THROUGH SATURDAY NIGHT/... As of 335 AM EST Wednesday... Thursday, the pressure gradient behind the departing shortwave trough will slacken, allowing for decreasing winds throughout the day. However, conditions early Thursday morning will still be on the very gusty side. Thursday into early Friday, the area will transition into a brief zonal pattern, with building high pressure across the region. This will yield dry and cooler conditions across the area. Late Friday afternoon into Friday night, the next Great Lakes upper level shortwave trough will progress west to east, north of the region. The tail end of the trough axis will cross the region with shallow moisture. Increasing northwest flow will once again increase across the region with isolated upslope snow showers across portions of southeast West Virginia continuing into and through Friday night. By Saturday, an upper level shortwave ridge will move into the region, helping to decrease the winds once again, and bring slightly milder conditions to the area. && .LONG TERM /SUNDAY THROUGH TUESDAY/... As of 258 PM EST Tuesday... High amplitude pattern seen during the past week will finally begin to flatten this weekend and gradually work into weak upper ridging across the southeast states early next week. This should basically act to cut off any added cold air intrusions with more of a Pacific nature airmass from Sunday through Tuesday. However a leftover wave across the Gulf states may push far enough north within increasing warm advection aloft to bring some light precipitation Sunday into Sunday night before drying returns Monday. However timing of this system remains iffy with some solutions much slower with rain lingering into Monday. This would support mainly a rain event with perhaps some mix at the onset if earlier arrival occurs Sunday morning. Otherwise running with mainly chance pops Sunday into Monday morning, then dry Monday afternoon/Tuesday under slightly higher heights and south of most northern stream energy at this point. Good moderation in temperatures to occur through the period as the cold pool aloft lifts out Saturday followed by decent west/southwest flow through Tuesday. This supports highs rebounding to near normal to start and then above normal into Day 7 including some 50s ahead of the next weak front && .AVIATION /14Z WEDNESDAY THROUGH SUNDAY/... As of 700 AM EST Wednesday... Aviation conditions will improve today as winds subside. Aside for some sct-bkn strato-cu across the VA/WV highlands this morning the overall trend is for clear skies for the bulk to the daylight hours. Weak high pressure will build across the central Appalachians today. Another clipper front will cross the area tonight, winds increasing as strong pressure rises occur across the Great Lakes and Ohio Valley. Some low level cloud cover will develop after 03Z/10PM with the potential for mountain snow showers and flurries. Medium to high confidence in ceilings, visibilities and winds during the TAF period. Extended Discussion... Upper level disturbance (clipper) will move east and away from the area Thursday. Conditions then trend VFR for the weekend, with the next chance for sub-VFR being Sunday night into Monday with a system emanating out of the mid- Mississippi Valley. && .RNK WATCHES/WARNINGS/ADVISORIES...
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VA...None. NC...None. WV...None.
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&& $$ SYNOPSIS...PM NEAR TERM...AL/PM SHORT TERM...DS LONG TERM...JH AVIATION...PM

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