Area Forecast Discussion
Issued by NWS Blacksburg, VA

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000 FXUS61 KRNK 231810 AFDRNK Area Forecast Discussion National Weather Service Blacksburg VA 110 PM EST Thu Feb 23 2017 .SYNOPSIS... Weak high pressure off the Mid Atlantic coast will cover Virginia and North Carolina today and tonight. A front across the Great Lakes into the southern Plains shifts slowly southeast to the Ohio Valley by Friday. The main cold front approaching from the Midwest will pass through our area Saturday. && .NEAR TERM /THROUGH TONIGHT/... As of 1018 AM EST Thursday...Update to expire the Dense Fog Advisory, adjust sky cover and raise highs up a couple degrees in eastern locations. Prevalence of dense fog has become much less. The fog banks themselves are still clearly delineated on webcams and on morning visible imagery, though they are patchy. Since there are still areas of patchy fog this morning with visibilities between one-half and two statute miles, I`ve issued a Special Weather Statement which runs through noon to address lingering patchy fog, though if I had to guess, fog may burn off quicker than that. The other aspect that the visible satellite imagery picks up on is a bit more optimistic sky conditions, particularly in the eastern/Piedmont areas today. While skies probably remain at least partly cloudy at best (predominantly partly/mostly cloudy) across most of southeast West Virginia into the Mountain Empire of Virginia, expect more sunshine today in central/eastern sections. Raised highs into the lower 70s out in the Piedmont, Virginia Southside and the North Carolina Piedmont, with highs reaching the mid/upper 60s from the Blue Ridge west. Previous near-term discussion issued at 430 am follows... No changes planned to Dense Fog Advisory. Numerous locations reported visibility of one half mile or less. The few exceptions were on the western slopes from Bluefield to the Mountain Empire area and along the peaks of the Blue Ridge which were higher than the depth of the fog. Models showed a modest improvement in visibility after 10AM. A few breaks in the clouds are possible from Charlotte County Virginia to Yadkin County North Carolina late this afternoon. With little to no heating today...temperatures rise will be limited. Have trimmed maximum temperatures today and may still need them lower depending on cloud cover. Some isentropic lift forecast today from Kentucky into western Pennsylvania. Otherwise little forcing so have lowered probability of precipitation. Bufkit forecast soundings and visibility guidance showed reformation of fog again late tonight. Have added larger coverage of fog after midnight. && .SHORT TERM /FRIDAY THROUGH SATURDAY NIGHT/... As of 300 AM EST Thursday... Weak shortwave ridging will build over our area Friday, as a mid- level trough/low is forecast to move into the Great lakes and Ohio Valley. It will remain unseasonably mild and generally rain free. The only exception is a few locations near the crest of the Blue Ridge thanks to local upslope flow. trimmed back pops a little friday and shaped towards the NAM. High temperatures Friday afternoon will range from the lower 60s in the mountains to the mid 70s in the Piedmont. A cold front will approach the region from the west Friday night and reach the mountains Saturday morning. Showers and a few thunderstorms will develop along and ahead of the cold front. The Day two convective outlook brings general thunderstorms into western portions of the forecast area. The marginal threat clips a few far western counties. It still looks like the best instability will remain north of the Ohio River. Low temperatures Friday night into saturday morning will vary from the mid 40s in the northwest mountains to the the 50s in the Piedmont. A cold front will move east across our area Saturday with scattered showers and thunderstorms. The mention of thunderstorms remains support by the sfc best lifted index and computed cape values. The latest Day 3 Convective Outlook places portions of cwa in a 5 percent chance of severe weather, Marginal threat. The main threat is for convective lines with damaging winds. High temperatures on Saturday will warm to the mid 50s in the mountains to the lower 70s in the Piedmont. By Saturday night, the front will be to our east, and northwest winds will be on the increase. The northwest winds will yield some gusts approaching 40 to 45 mph at the highest elevations. At this time, it appears that winds will remain below wind advisory levels. With colder air pushing into our region, any lingering upslope rain showers across parts of southeast West Virginia, south into the northern mountains of North Carolina are expected to transition to snow showers by Sunday morning. Little or no accumulations expected with any snow showers. Low temperatures Saturday night will be near normal with readings from the lower 20s in the mountains to the mid 30s in the Piedmont. && .LONG TERM /SUNDAY THROUGH WEDNESDAY/... As of 300 AM EST Wednesday... Gusty winds will continue into early Sunday behind Saturday`s cold frontal passage. These winds will weaken quickly during the day and back southwest as the next upper level trough deepens across the Central Plains. This same upper trough will move east and be over the Ohio Valley by mid-day Monday. A warm front in advance of this system will head north through our region, bringing a return of patchy light precipitation to the area during the day Monday. There may be an issue of a brief period of a wintry mix across the northwest section of the area early Monday as a potential warm nose develops over a sub-freezing boundary layer and surface. For now, will keep things simple by reflecting a rain versus snow forecast based solely on whether the forecast surface temperatures is above or below freezing. Monday night the system`s associated cold front is expected to cross the area. Look for the precipitation to become more showery Monday night into early Tuesday. Model guidance for the remainder of Tuesday into Tuesday evening is not clear. The GFS is progressive with the cold front making significant headway east of the region. The ECMWF is not progressive, stalling the feature over the area, all while suggesting another wave will move northeast along this boundary, keeping a generous coverage of rain across the area Tuesday afternoon into Tuesday night. Our forecast will reflect a blend of these solutions. While rain will be forecast Tuesday afternoon and evening, it will not be to the degree offered by the ECMWF. For late Tuesday night into Wednesday, model agreement improves with solutions bringing yet another upper low/trough from the Central Plains states into the Ohio Valley. Warm frontal rain is expected late Tuesday night into early Wednesday, with a generous coverage of showers and some isolated thunderstorms across the area Wednesday afternoon coincident to the cold frontal passage. Behind the cold front in the northwest flow, a few rain and snow showers may linger in the western mountains Thursday. Temperatures Sunday and Monday will be normal for this time of year. Reading moderate through mid-week with temperatures some ten to fifteen degrees above normal expected. && .AVIATION /18Z THURSDAY THROUGH TUESDAY/... As of 110 PM EST Thursday... Earlier LIFR fog has since burned off to VFR conditions at the TAFs. VFR will continue through the afternoon into the mid- evening hours. Favorable conditions for radiational fog with associated IFR to VLIFR conditions after 04z through 13z. I`ve included BR/FG and a stratus deck for all TAF sites except for BLF where wind fields are a bit higher. Winds are light southerly to calm. Fog to burn off to VFR conditions mid-morning Friday with VFR ceilings (Cu around the Blue Ridge). Winds still light southerly though will increase late in the TAF period to around 7 kts at BLF. Note: AMD NOT SKED appended to the LYH TAF for the ongoing ASOS outage. TAF amendments will resume once LYH observations are restored. Extended Aviation Discussion... Friday we will be well into the warm sector with VFR conditions and much above normal temperatures. Surface wind gusts of 20 to 30 kts possible across the higher terrain on Friday. Band of showers and isolated thunderstorms with MVFR conditions arrive late Friday night into early Saturday along and ahead of a strong cold front. Drier weather and increasing northwest winds follow behind the front on Saturday afternoon through Sunday. Approach of another front Monday will provide increasing clouds and possibly showers and MVFR cigs to BLF/LWB late in the day. && .CLIMATE... As of 245 PM EST Wednesday... Warm temperatures set to occur again Thursday with increase in westerly flow in the low levels. Question will be cloud cover. At the moment with some sunshine look for highs and lows to approach or break records for Feb 23rd. Thursday 02/23/2017 Site Record High/Year Record Warm Low/Year Bluefield 74 1975 51 1975 Danville 73 1980 50 1981 Lynchburg 74 1943 52 1925 Roanoke 76 1943 54 1925 Blacksburg 69 1980 46 1990 && .EQUIPMENT... As of 440 AM EST Thursday... The automated observation system at Lynchburg(LYH)had multiple sensor failures. Electronics technicians will be performing repairs on the system this morning. && .RNK WATCHES/WARNINGS/ADVISORIES... VA...None. NC...None. WV...None. && $$ SYNOPSIS...AMS NEAR TERM...AL/AMS SHORT TERM...KK LONG TERM...DS/KK AVIATION...AL/AMS CLIMATE...WP EQUIPMENT...AMS

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