Area Forecast Discussion
Issued by NWS Blacksburg, VA

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000 FXUS61 KRNK 211935 AFDRNK Area Forecast Discussion National Weather Service Blacksburg VA 235 PM EST Wed Feb 21 2018 .SYNOPSIS...
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High pressure will remain off the Southeast coast, which will keep well above normal temperatures through the remainder of this week. Chances of rain should increase as a cold front approaches from the west. This front should cross overhead later in the weekend.
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&& .NEAR TERM /THROUGH THURSDAY/...
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As of 230 PM EST Wednesday... An anomalous upper level ridge remains off the Southeast coast, which is providing quite a warm day for February with near record high temperatures expected. See the climate section for more details. Cloud cover has been thinning over most of the area during the day, but a copious amount remains over the southern Blue Ridge. It will likely not break up until late afternoon. The latest mesoscale models are not impressive with the development of a few showers or thunderstorms along and west of the Blue Ridge, but only a slight trim to coverage and POPs was made as enough warming is taking place to provide some weak instability. For this evening and beyond in this period due to what happens tomorrow, this forecast steered away from the GFS solution and in more agreement with the NAM and higher- resolution models. It will remain unseasonably mild overnight, but a cold front will approach from the west to possibly bring a few showers. Coverage appears highest over the southern Blue Ridge and parts of the Alleghany Highlands of Virginia. Meanwhile, high pressure will head east of the Great Lakes and begin to wedge southward along the eastern slopes of the Appalachian Mountains. As a result, a backdoor cold front should slide southward east of the Blue Ridge toward Thursday morning. Several adjustments were made for Thursday such as shaping temperatures to fall throughout the day in the Piedmont along with adding areas of fog and drizzle. POPs were also increased near Lynchburg to accommodate the likelihood of rain developing along the backdoor cold front. Temperatures were also shoved well below guidance, and the timing of the wedge was also sped up a few hours based on the latest high-resolution model solutions.
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&& .SHORT TERM /THURSDAY NIGHT THROUGH SATURDAY NIGHT/...
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As of 200 PM EST Wednesday... Surface front will continue to bow south through much of the region Thursday night per the favored colder Nam before slowly lifting back north Friday ahead of another stronger wave lifting by well to northwest. This would support higher pops over the north closer to the baroclinic zone aloft and perhaps spotty light rain/drizzle behind the boundary into early Friday. Models suggest only weak support for added measurable rainfall Friday afternoon as the main lift passes well west and the wedge lingers for much of the day. Will keep some low pops going mainly north/west with perhaps lingering drizzle elsewhere Friday. Temps into Friday very tricky pending exactly where the backdoor front ends up as latest Mos showing a 10-15 degree difference in values from the colder Nam to the warmer GFS. For now will lean more toward the Nam but stay above its coldest values at this point. Front should lift back to the north Friday night into Saturday ahead of stronger shortwave energy heading northeast out of the central states. This will gradually push the area back into the warm sector Saturday into Saturday night. However lift and deeper moisture will remain north and west of the area until the moisture ahead of the front arrives west late Saturday night. Appears could be some scattering of showers mainly north and west, but overall chance to slight pops which may be overdone until very late Saturday night. Lows Friday night remain iffy with lows mostly 40s to mid 50s with values steadying/rising late. Highs Saturday look to be mostly late day within the residual eastern wedge while perhaps jumping to around 70 west espcly if more sunshine occurs. Thus stayed below guidance given the likely slower trend of Cad erosion at this point.
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&& .LONG TERM /SUNDAY THROUGH WEDNESDAY/...
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As of 145 PM EST Wednesday... Strong upper ridge off the southeast coast looks to weaken during the period allowing more in the way of zonal flow to take shape next week. This will initially occur as stronger shortwave energy passes well north late in the weekend with a trailing cold front crossing the area from the west on Sunday per model consensus. Swath of weakening showers along the boundary should affect the region during the day although some solutions remain slower and have much of the rain behind the front which would suggest best pops west at this this point. Showers may also linger far southern sections Sunday evening as the boundary folds over otherwise drier later Sunday night across the region. Should be the last day of much above normal highs with another round of 60s to lower 70s. Drier/cooler air follows the front for early next week as high pressure builds in Monday and wedges in from the north on Tuesday. This likely to return some clouds to the region by later Tuesday with the wedge holding into Wednesday. May see another weak shortwave pass along the boundary just to our south Monday night per 00z Euro which could bring more rain back to southern sections but iffy. Otherwise next impulse dropping out of the Rockies may tag with the front to bring another area of organized rainfall into the region by later Wednesday. Temps cooler into next week, but still above normal with highs 50s to lower 60s.
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&& .AVIATION /18Z WEDNESDAY THROUGH MONDAY/...
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As of 230 PM EST Wednesday... VFR conditions should hold for most locations through the afternoon, but some MVFR clouds and showers will be possible along the southern Blue Ridge and parts of southeast West Virginia. Increasing moisture during the evening and tonight in the boundary layer should allow for ceilings to deteriorate overnight. Confidence is high that IFR should arrive at all TAF sites between 06Z and 12Z on Thursday. The most problematic aspect of this forecast is the timing of a backdoor cold front sagging southward over the Piedmont courtesy of high pressure wedging against the eastern slopes of the Blue Ridge. Flying conditions should worsen during the morning as ceilings and visibilities fall toward IFR. The frontal passage will bring cooler east winds along with areas of fog and drizzle. LYH has the highest confidence of IFR throughout the day, but confidence is lower for ROA/DAN/BCB due to how far south the backdoor cold front advances. Cloud cover alone will likely keep it MVFR/IFR throughout the area into the evening. Extended Aviation Discussion... High pressure will continue to wedge southward against the eastern slopes of the Blue Ridge, which will keep areas of fog and drizzle through tonight into Friday. Conditions will likely plummet to IFR by Friday morning. Eventually, the backdoor cold front will stall along the Virginia and North Carolina line and retreat northward as a warm front toward Friday evening. VFR conditions should return for most locations during Friday night and Saturday aside from any typical low clouds along the Blue Ridge on Saturday morning. By Saturday afternoon, shower coverage should increase as a cold front arrives from the west that could bring MVFR/IFR conditions toward Sunday. Better flying weather should return later on Monday.
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&& .CLIMATE... As of 330 AM EST Wednesday... Today will again feature well above normal temperatures that may approach or eclipse daily record highs and daily record high minimum temperatures. It is also possible that all-time warmest February minimum temperatures could be approached or broken in this period. Following are daily records, as well as the all-time warmest minimum temperatures recorded in the month of February, for our five climate sites with long-established periods of record: Wednesday 2/21/2018 Site MaxT Year HiMin Year BLF 65 1996 54 1997 DAN 75 2011 55 1953 LYH 75 1930 50 1981 ROA 73 1930 48 1997 RNK 71 1986 49 1953 Warmest HiMin - February: Site HiMin Date BLF 57 Feb 5 2008 DAN 60 Feb 18 2008 LYH 59 Feb 20 1939 ROA 57 Feb 12 1932 RNK 52 Feb 16 1990 && .RNK WATCHES/WARNINGS/ADVISORIES... VA...None. NC...None. WV...None. && $$ SYNOPSIS...PW NEAR TERM...PW SHORT TERM...JH LONG TERM...JH AVIATION...PW CLIMATE...AL

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