Area Forecast Discussion
Issued by NWS Raleigh/Durham, NC

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596 FXUS62 KRAH 240846 AFDRAH Area Forecast Discussion National Weather Service Raleigh NC 330 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 THROUGH FRIDAY/... As of 240 PM Friday... We remain in the warm sector for one final day Sunday with deep southerly flow on the west side of stacked ridging offshore. Highs Sunday will climb well into the 70s, with some very low 80s possible in the southeast. Moisture will be on the increase in this flow regime, and a cold front will be edging slowly east as the ridging offshore is flattened/suppressed south by a strong short wave moving across the Midwest and into the Great Lakes region. The surface front is expected to stall as it reaches the area on Sunday, with a surface wave lifting northeast up the frontal zone on Monday. Showers will thus be increasing from the west throughout the day on Sunday, becoming likely across all of central NC Sunday night through most of the day Monday. Widespread rainfall totals of one half inch are expected, but we could see one inch amounts due to training in some areas. Monday`s highs will be suppressed by rain in addition to cool air advection, but the encroaching airmass will be a bit warmer than seasonal, having originated in the lower Midwest and been allowed to further moderate due to slow eastward progression. High pressure will build into the mid Atlantic briefly Tuesday through early Wednesday, with plenty of sun and drier conditions to accompany seasonable temperatures in the low to mid 60s after morning lows in the 40s. A warm front will lift north, accompanied by increased cloud coverage and chances for showers by Wednesday afternoon through Thursday, when our next cold front is expected to sweep through and restart the cycle again. Highs Thursday will climb back to the 65 to 70 range ahead of the front, with seasonable temperatures near 60 to follow on Friday in the front`s wake. && .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...mlm AVIATION...JJM/MWS CLIMATE...RAH is the U.S. government's official web portal to all federal, state and local government web resources and services.