Area Forecast Discussion
Issued by NWS Blacksburg, VA

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000 FXUS61 KRNK 131826 AFDRNK Area Forecast Discussion National Weather Service Blacksburg VA 126 PM EST Mon Nov 13 2017 .SYNOPSIS... A cold front will progress eastward through the first part of Monday. A ridge of high pressure then builds in from the northwest later tonight into early on Wednesday. Though mostly cloudy skies are expected for tonight, clear skies and dry conditions should prevail for Tuesday. Late in the week turns more active with a couple of frontal passages later Wednesday and an even stronger one on Saturday. && .NEAR TERM /THROUGH TUESDAY/... As of 1000 AM EST Monday... With onset of insolation visibility has steadily been improving as shallow stratus layer erodes. Any lingering visibility restrictions are no longer expected to create hazardous conditions so the dense fog advisory has been allowed to expire. Previous discussion... Region is stuck in a damp, light- flow regime, with trapped moisture underneath dry mid-level air seen on water vapor imagery. The forecast challenge is timing when we can shake free of the low clouds and its effect on temperatures. BUFKIT forecast soundings reveal that trapped moisture may linger in the Piedmont until around noon, while locales in southeast WV, the mountains of NC and much of southwestern VA likely remains blanketed in overcast even into tonight. These trends will keep temperatures on a very slow climb until the afternoon in the Piedmont, while climbing maybe a couple degrees all day along and west of the Blue Ridge up into southeastern WV. Modest cold advection takes place with FROPA, further tempering much warming. Should see a wind shift to west around 10-15 mph with the frontal passage, along with spotty rain showers in our far western counties in WV/VA this morning. Winds gradually abate into the evening. Overall a better second half of the day in the Piedmont and foothills, while more pessimistic in the western mountains of VA, WV and NC. Trended temperatures closer to colder MET guidance, which leads to highs in the mid/upper 40s and into the lower to middle 50s in the VA/NC Piedmont, southside and foothills. Into tonight, surface high becomes positioned over central Ohio with ridging across the region. It`s likely that stratus will still continue in the western mountains early, with at least brief clearing from the Blue Ridge east. There may be enough moisture left to wring out some sprinkles or even flurries in the Greenbrier mountains at elevations above 3500` where profiles turn sub- freezing, but nil accumulations. As flow turns to a northerly/northeasterly after midnight, look for the onset of wedge conditions leading to increased cloudiness immediately along the Blue Ridge into the foothills in NC/VA. Despite 850 mb temperatures of 0 to -2C, surface temps cool more slowly with effects of cloudiness. Indicated lows mainly in the 30s, lowest in the west and toward the upper 30s in the Piedmont, Southside and foothills. && .SHORT TERM /TUESDAY NIGHT THROUGH THURSDAY NIGHT/...
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As of 126 PM EST Monday... An upper level trough axis center over our area Tuesday afternoon will move east into the Atlantic ocean Tuesday night. Low temperatures Tuesday night into Wednesday morning will range from the upper 20s in the mountains to the mid 30s along the southern Blue Ridge Mountains. A cold front in the Ohio Valley will approach our area Wednesday and push into the western mountains by Wednesday evening. The timing of the front and its associated precipitation is a little slower on 12z model run. High temperatures Wednesday will vary from the mid 40s in the west to the mid 50s in the east. As the upper trough moves by to our north Wednesday night in Thursday morning, the front will stall to our south near the North Carolina and South Carolina border. Low temperatures will generally be from the upper 30s in the northwest mountains of Greenbrier county to the lower 40s in the piedmont. On Thursday, the forecast area will be sandwiched between the midweek upper trough with stalled weak front expected to our south and weak high pressure evident across the East. Under partly to mostly sunny conditions, temperatures will be seasonable with high readings from the lower 40s in the mountains to the mid 60s in the piedmont. Thursday night will be colder than Wednesday night with values from the upper 20s in the coldest northwest valleys to the mid 30s in the piedmont.
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As of 126 PM EST Monday... As a shortwave exits towards Nova Scotia early Friday,a powerful cyclone will develop and emerge out of the Mississippi Valley by Friday afternoon. Rapid intensification of this system is expected while moving into the Great Lakes region this weekend with a secondary area of low pressure developing off the New England coast by late Saturday. A warm front will lift north across our area Friday evening into Friday night, than a strong cold front will sweep east across our region Friday night into Saturday. The timing of the front remains faster on the GFS compared to ECMWF. Utilized an ensemble blend for timing of the boundary. The cold front could arrive in the form of a narrow strongly forced line of showers or thunderstorms. The actual evolution will determine how much instability we will have to work with. The GFS/Canadian/ECMWF are depicting a deep upper trough across the east/northeast U.S. into the first half of next week. This will lead to below to well below normal temperatures in the extended periods with lows in the 20s and highs in the 30s and 40s west to around 50 in the Piedmont. Precipitation will be below normal with a predominate drier northwest flow aloft. Gusty northwest winds are expected behind the front with strong CAA/significant pressure rises, and deep low pressure developing across the Northeast. For areas along and west of the Blue Ridge, appears solidly in the Wind Advisory category, with the potential for a High Wind Warning at the higher elevations in northwest NC into southwest VA. Will highlight the wind potential in the HWO. There remains plenty of time to work out the details with this strong cold front.
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&& .AVIATION /18Z MONDAY THROUGH SATURDAY/... As of 557 AM EST Monday... MVFR to LIFR flight categories persist this morning contributing to poor flight conditions. Much of these degraded conditions are from low stratus and areas of fog. Fog has been locally dense at times in the NC Piedmont and along the southern Blue Ridge in NC, with MVFR to IFR visibilities in fog at specific TAF sites. Degraded conditions are expected to continue through the mid- late morning hours in the Piedmont, as a cold front enhances westerly winds to mix the fog out. Ceilings should also improve in turn in this general area as well. By afternoon, western terminals likely to remain degraded with lingering post-frontal stratus, with the best chance at VFR conditions at Danville, Roanoke and Lynchburg. Calm winds initially become west- northwest 6-9 kts today. For tonight, post-frontal stratus will continue to linger with MVFR to IFR ceilings possible at Bluefield, Lewisburg and Blacksburg. While VFR conditions should initially prevail, a high pressure area to the north should induce a return of northeasterly stratus into Lynchburg and Danville. Confidence isn`t as high at Roanoke for degraded ceilings but indicated possibility with SCT030 group. Look for west-northwest winds veering to northerly and relaxing to 3-6 kts for tonight. Extended Discussion... Initial sub-VFR ceilings Tuesday morning should begin to thin to all VFR as trapped moisture thins out by mid-morning Tuesday. VFR conditions then continue until Wednesday evening, with a cold frontal passage. A period of sub-VFR conditions, brief showers and a west-northwest wind shift appear possible for the overnight period. Possible post-frontal sub-VFR ceilings into Thursday in the western Appalachians, otherwise VFR conditions. VFR then anticipated through Thursday afternoon and evening. && .RNK WATCHES/WARNINGS/ADVISORIES... VA...None. NC...None. WV...None. && $$ SYNOPSIS...AL NEAR TERM...AL/MBS SHORT TERM...KK LONG TERM...KK AVIATION...AL is the U.S. government's official web portal to all federal, state and local government web resources and services.