Area Forecast Discussion
Issued by NWS Raleigh/Durham, NC

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000 FXUS62 KRAH 210554 AFDRAH Area Forecast Discussion National Weather Service Raleigh NC 154 AM EDT Sat Oct 21 2017 .SYNOPSIS... High pressure will extend across the eastern United States through the weekend. && .NEAR TERM /THROUGH TONIGHT/... As of 924 PM Friday... High pressure at the surface and aloft will maintain dry and seasonable conditions across central NC tonight. Gradual modification of antecedent dry airmass in place is currently underway, particularly along and west of the Triangle, where sfc dewpoints this evening are running 3 to 6 degrees higher than this same time yesterday, which should translate into warmer overnight lows. Lows ranging from mid 40s in the cooler locations to upper 40s- lower 50s elsewhere. && .SHORT TERM /SATURDAY AND SATURDAY NIGHT/... As of 325 PM Friday... The high pressure system will remain in control of our weather Saturday into Saturday night. Aside from some passing cirrus aloft, expect sunny skies and mild afternoon temperatures. Temps will range from the mid-upper 70s north to near 80-lower 80s south. The sfc ridge associated with the high will drift offshore Saturday night through early Sunday. The resultant sely low level flow will advect enough moisture to yield patchy fog over most of the region by daybreak Sunday. Not expecting dense fog so no travel issues anticipated. It will be a bit milder with min temps in the upper 50s to around 50 nw to the low-mid 50s southeast. && .LONG TERM /SUNDAY THROUGH FRIDAY/... As of 215 PM Friday... Ridging over the Atlantic coast will shift east and offshore Sunday as a trough over the Mississippi Valley deepens and a cutoff low forms over the lower Mississippi valley. Another near perfect "final fair" day is on tap, with mostly sunny skies and highs climbing to the mid and upper 70s. Warm air advection will keep mins up overnight, with Monday morning`s lows mostly in the mid and upper 50s. Clouds will be on the increase Monday as deepening south to southwest return flow pumps moisture into the area ahead of a strong cold front which will be reaching the mountains late in the day. It will be warm ahead of the front in southerly flow with at least some filtered sun early in the day, and highs will reach the mid and upper 70s. Expect scattered showers showers to develop over the Piedmont, especially in the Charlotte and Triad areas, during the afternoon, with showers becoming likely Monday night as the front pushes across the mountains and accelerates eastward. Mins ahead of the front again will remain mild Monday night...from upper 50s west to the lower 60s east. There are model differences in the timing and evolution of the cutoff low, which will determine mid level dynamics available to support strong low level forcing ahead of the surface frontal zone. Even given unfavorable timing=lessened instability, low level jetting of 50+ knots and strong helicity ahead of the front suggest a line of vigorous showers/thunderstorms late Monday night in the west shifting to the Coastal Plain towards mid day Tuesday. Highs Tuesday will be hampered somewhat by cloudiness, with temperatures topping out near 70 in the west to 75 in the southeast. Cold air advection begins to surge into the area Tuesday night, with dry weather returning, though we could see lingering instability showers as residual moisture is squeezed out of the airmass. Mins Wednesday morning will range from 45 to 50, with highs Wednesday mostly in the low and mid 60s. Cool air peaks on Thursday, with morning lows mostly from 40 to 45, with some upper 30s in the northwest. Highs will be mostly in the lower 60s with some upper 50s northwest. Friday will warm a bit to the mid and upper 60s as short lived surface high pressure moves offshore and low level flow quickly backs from northwest to southwest. && .AVIATION /06Z SATURDAY THROUGH WEDNESDAY/...
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As of 150 AM Saturday... High pressure over the middle Atlantic states, and associated strong radiational cooling and risk of radiation fog centered over ern VA/NC this morning, including at RWI (and perhaps FAY), will otherwise result in VFR conditions and light and variable to light nely/ely surface winds, through the TAF period. Outlook: Continued persistence radiation fog will be possible mainly at RWI each morning through the weekend, followed by a higher probability of more-widespread sub-VFR conditions in stratus and fog, in increasingly moist east to southeasterly low level flow, Sun night-Mon morning. An approaching frontal system will then result in a good chance of sub-VFR conditions, showers and storms, and strong/shifting winds with height late Mon-Tue.
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&& .RAH WATCHES/WARNINGS/ADVISORIES... None. && $$ SYNOPSIS...MWS NEAR TERM...CBL SHORT TERM...WSS LONG TERM...mlm AVIATION...MWS

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