Area Forecast Discussion
Issued by NWS Raleigh/Durham, NC

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000 FXUS62 KRAH 230301 AFDRAH Area Forecast Discussion National Weather Service Raleigh NC 1000 PM EST Thu Feb 22 2018 .SYNOPSIS...
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A strong sub-tropical ridge aloft situated off the Southeast U.S. coast will weaken while drifting south toward the Bahamas through Friday night. Meanwhile, a back door cold front will settle into north-central NC late tonight and early Friday. The front will become quasi-stationary over northern NC through Friday night, then retreat north as a warm front on Saturday.
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&& .NEAR TERM /THROUGH TONIGHT/...
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As of 1000 PM Thursday... 00Z upper air analysis depicts an abnormally strong mid/upper level anti-cyclone offshore of the Southeast U.S., ridging west into SC/GA. The return flow associated with this high remains focused well to our west-sw from the lower MS Valley into the MO Valley. At the surface, a cold front was aligned along the NC/VA border at 02Z. This feature being propelled swd by a 1040+ mb high centered over New England. The sfc front will slow to a crawl across the northern coastal plain/northern Piedmont as it encounters a fairly deep west- sw flow, and the parent sfc high over New England scoots eastward early Friday. Main forecast issues overnight center around how far south the front will get before it stalls, and consequently how much cooler air works into our region. And secondly, the extent and severity of the fog overnight across the far south. Some of the near term models may be a touch overzealous bringing the front as far south as RDU by 06Z (01Z RAP) while the 18Z GFS may be a little too slow. Thus, suspect the truth is somewhere in the middle. Using a blend of the NAM and the NBM suggest the sfc front drifting swd with time then stalling near or just south of highway 64. Thus, expect a marked cool down in temps overnight across the far northeast piedmont-northern coastal plain. In addition, weak/marginal isentropic upglide along the front may lead to spotty light rain/drizzle behind the front. Across the south half, mild overnight conditions will continue with areas of low clouds developing and potentially spotty dense fog. Expect the fog threat to be greatest in vicinity of the southern Sandhills and southern coastal plain.
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&& .SHORT TERM /FRIDAY AND FRIDAY NIGHT/... As of 305 PM Thursday... Principle forecast challenge remains how far into n-cntl NC the cold front moves, then to what degree it retreats nwd during the afternoon and evening hours. Forecast confidence is relatively high for the srn half of cntl NC, with persistence lifting and scattering of morning low cloudiness and fog, with with temperatures again in the upr 70s to around 80 degrees. Forecast confidence is similarly high that nrn locations from near Roxboro to Henderson to Lake Gaston and Roanoke Rapids Kerr will remain cool, in the 60s, with some upr 50s possible, amidst CAD and continued post-frontal low cloudiness, and a chance of light rain and drizzle in the morning. The greatest uncertainty and 10-15 degree bust potential will exist roughly along and just north of Highway 64, including the major metro areas along I-40. There will be a sharp gradient in temperatures in this corridor separating the two regimes noted above. The front will remain quasi-stationary and become increasingly diffuse Friday afternoon and evening, with an otherwise persistence forecast of continued mild conditions, with yet another round of late night low cloudiness and areas of fog owing to the persist unseasonably humid conditions in place. && .LONG TERM /SATURDAY THROUGH THURSDAY/... As of 225 PM Thursday... The subtropical ridge hangs tough through the weekend and looks like we will remain in the warm sector, with highs well into the 70s Saturday and Sunday. A cold front will be edging east as the ridge retrogresses slightly southwest, but the front`s progress will be glacial and the front will be basically stalled in the vicinity through Monday. Will have likely PoPs in the West on Sunday, transitioning slowly across the area to the east on Monday, which looks to be our best chance for rain as a surface wave lifts northeast along the boundary. The persistent subtropical ridge will weaken/dampen as a vigorous mid level short wave lifts out of the Midwest, hammering the ridge further south and interrupting our warm spell. Highs Monday will be limited to low and mid 60s by cloud coverage and potential for some cool air advection as the surface front reaches the Coastal Plain late in the day. Drier and seasonable high pressure will build in on Tuesday through Wednesday, with copious sun and highs mostly from 60 to 65 after morning lows from 40 to 45. The ridging hasn`t finished with us yet, as it will be re-amplifying northward up the eastern CONUS on Wednesday, lifting a warm front north into the area with associated rain on Wednesday night into Thursday. Highs Thursday will be mostly low and mid 60s. && .AVIATION /00Z FRIDAY THROUGH WEDNESDAY/... As of 645 PM Thursday... 24-Hour TAF Period: The persistence forecast continues for this 24 hour period. VFR conditions to start the TAF period will once again give way to MVFR cigs and visbys after midnight, generally between 06Z and 09Z Friday, then subsequently dropping to IFR/LIFR between 09Z and 15Z, with the best chances at KFAY, then KRWI and less so at KRDU, KGSO, and KINT. Cigs in the 800-1500 ft range will persist into the morning, gradually scattering out during the afternoon. A period of light rain/drizzle is possible Friday morning as a backdoor cold front drops southward through northern and eastern portions of Central NC. Generally expect clouds to scatter out with bases in the 2-4 kft range toward the end of the TAF period. Winds are expected to be light and variable through the period, the only exception being a brief period of 5-10 kt winds along the aforementioned cold front. -KC Looking ahead: The sub-tropical ridge will weaken and drift south, but maintain influence over the Carolinas. As a result, a persistence forecast of late night-morning stratus and fog, lifting and scattering to high MVFR-low VFR each afternoon, will generally continue through the weekend. Otherwise, the next chance of rain will accompany a frontal zone that will settle into, and possibly stall over the Carolinas, late Sun into early next week. -MWS && .CLIMATE...
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RDU Records: Date | High Year | High Min Year ------------------------------------------ 02/23 79 1980 57 1962 02/24 81 1982 58 1985 GSO Records: Date | High Year | High Min Year ------------------------------------------ 02/23 74 2017 52 1922 02/24 79 1982 55 1985 FAY Records: Date | High Year | High Min Year ------------------------------------------- 02/23 80 1922 55 1922 02/24 83 1930 60 1975
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&& .RAH WATCHES/WARNINGS/ADVISORIES... None. && $$ SYNOPSIS...MWS NEAR TERM...WSS SHORT TERM...MWS LONG TERM...mlm AVIATION...KC/MWS CLIMATE...RAH

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