Area Forecast Discussion
Issued by NWS Raleigh/Durham, NC

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000 FXUS62 KRAH 240851 AFDRAH Area Forecast Discussion National Weather Service Raleigh NC 351 AM EST Sat Feb 24 2018 .SYNOPSIS... A strong sub-tropical ridge aloft situated off the Southeast U.S. coast will weaken while drifting south toward the Bahamas through Saturday. Meanwhile, a quasi-stationary front will remain over central NC through tonight, then retreat northward while dissipating on Saturday. && .NEAR TERM /THROUGH TONIGHT/... As of 330 AM Saturday... Latest surface analysis shows a stationary front draped across central North Carolina separating a rather significant N/S dewpoint and temperature spread. Currently, dewpoints/temps near the VA/NC border reside in the mid to upper 40s while those along the NC/SC border are in the lower 60s. Intermittent fog formation is ongoing across much of the area, with additional fog formation likely, especially between 4am and 10am on Saturday. Little in the way of movement with this boundary has been witnessed thus far tonight, but guidance continues to indicate a slow retreat northward likely during the predawn hours. This should allow temperatures to steady to even slightly increase through dawn, with intermittent mid to upper level clouds overspreading from west to east associated loosely with the cold front draped west of the Appalachian Mountains. && .SHORT TERM /SATURDAY AND SUNDAY/... As of 330 AM Saturday... Sub-tropical ridging will remain centered in the vicinity or just northeast of the Bahamas, with associated surface high pressure extending from just south of Bermuda, westward into the southeaster U.S. This pattern will maintain unseasonably warm and relatively humid conditions across central North Carolina both Saturday and Sunday. Expect afternoon temperatures in the mid 70s to low 80s each day under intermittent cloud cover, with mild overnight low temperatures in the lower 60s expected Saturday night into Sunday. Cloud cover will be thickest across the western Piedmont Counties, where intermittent shower chances will be possible Saturday afternoon and evening, and again Sunday afternoon as the front pushes into the western portion of the state. Southwesterly winds will accelerate Sunday ahead of the approaching cold front, with sustained winds 10 - 15mph with gusts up to 30mph possible. && .LONG TERM /SUNDAY NIGHT THROUGH FRIDAY/...
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As of 345 AM EDT Saturday... Sunday night through Monday night: Models are starting to come into better agreement with the timing of the cold front through the area Sunday night/early Monday, that is forecast to slow down and briefly stall along coastal areas on Monday before finally pushing south and away from the area Monday night. While a decent area of showers is expected to accompany the front Sunday evening/night , the better rain chances and higher QPF amounts will likely occur post-frontal on Monday, in response to the approach of a well- defined/significant shortwave trough that will spur the development of multiple waves tracking NE along the quasi-stationary frontal zone. Current model timing indicates, rain chances will taper off NW to SE during the late afternoon/evening hours. Widespread rainfall amounts of a half inch to three quarters of an inch can be expected. Calendar day highs in most locations will occur before daybreak, prior to fropa, with widespread rain and clouds keeping daytime temperatures in the mid/upper 50s NW to lower 60s. Clearing and CAA on the leading edge of a 1030ish mb high building into the area will result in some of the coolest overnight lows that we`ve seen for some time. Lows in the lower to mid 40s, which is still a good 5 to 7 degrees above normal. Tuesday through Friday: Expect dry, slight above normal temperatures on Tuesday as a progressive surface high builds across the mid Atlantic states briefly on Tuesday, only to quickly shift off the southern Mid-Atlantic Coast Tuesday night. The later half of the work week is setting up to be wet and unsettled, with widespread showers expected Wednesday through Wednesday night, within the warm conveyor feed on the cyclonic side of the shortwave trough ejecting east out of the southern Rockies. At this time, model spread is high wrt to the eastward evolution of the this system, more specifically, when/where this system will phase with northern stream energy as it progresses into the Eastern US. Eventually this system and it`s attendant cold front will bring another round of showers and possibly some thunder to the area Thursday/Friday. Will continue to monitor. Continued mild, with highs in the 60s on Wednesday, warming into the 70s ahead of the front.
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&& .AVIATION /06Z SATURDAY THROUGH THURSDAY/... As of 1250 AM Saturday... 24-Hour TAF Period: A frontal boundary continues to remain stalled across central North Carolina, with KINT, KGSO, KRWI, and KRDU remaining north of the boundary and KFAY sitting just south. Biggest difference at this hour between the north side and southside remains dewpoints, with 60s prevalent across the Sandhills/southwest Piedmont Counties and 50s prevalent further north. Expect this boundary to slowly lift north overnight, allowing dewpoints to rise and aviation conditions to deteriorate in the form of reduced VSBYS. VFR conditions remain in place everywhere except for RWI, where BR formation has begun. Each site will likely dip to LIFR overnight, especially between 4am and 10am Saturday. Confidence of FG formation is higher at the eastern sites vs the western sites who will see a layer of mid to upper level clouds spill across the area. Winds will remain light to variable, becoming predominantly southwesterly around 10mph during the day Saturday as mixing is allowed and conditions return to VFR+ before mid day. - JJM Looking ahead: Increasing winds, particularly aloft, will limit fog potential Saturday night, except for at perhaps FAY and RWI where winds will be relatively lighter, with overnight-early morning low stratus anticipated otherwise and elsewhere. Those strengthening winds aloft may also result in marginal low level wind shear conditions at Piedmont sites Saturday night, given the likely presence of a shallow, ~1000 ft inversion, which will tend to separate a steady and even occasionally gusty ssw wind at the surface from an abrupt increase in flow within and above the inversion. The approach and slow passage of a frontal zone will result in a high probability of showers, and some sub-VFR conditions, late Sun into early next week. -MWS && .CLIMATE... RDU Records: Date | High Year | High Min Year ------------------------------------------ 02/24 81 1982 58 1985 GSO Records: Date | High Year | High Min Year ------------------------------------------ 02/24 79 1982 55 1985 FAY Records: Date | High Year | High Min Year ------------------------------------------- 02/24 83 1930 60 1975 && .RAH WATCHES/WARNINGS/ADVISORIES... Dense Fog Advisory until 10 AM EST this morning for NCZ009>011- 026>028-041>043-073>078-083>086-088-089. && $$ SYNOPSIS...MWS NEAR TERM...JJM SHORT TERM...JJM/MWS LONG TERM...CBL AVIATION...JJM/MWS CLIMATE...RAH

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