Area Forecast Discussion
Issued by NWS Raleigh/Durham, NC

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000 FXUS62 KRAH 201100 AFDRAH Area Forecast Discussion National Weather Service Raleigh NC 700 AM EDT Sun May 20 2018 .SYNOPSIS... A moist and slightly unstable air mass will remain entrenched across central NC through the middle of the week. && .NEAR TERM /TODAY AND TONIGHT/... As of 650 AM Sunday... Southerly flow will continue to advect warm, moist air into Central NC today. Expect some convective activity across the area, however the coverage should be isolated to widely scattered and focused along surface boundaries. MUCAPE values will be higher than previous days, generally in the 1500-2000 J/Kg range across the area this afternoon and evening. With good low-level moisture and instability, the question is if/where there will be a forcing mechanism to generate convection. The sea breeze will be a likely focus area, but otherwise there aren`t any obvious signals or boundaries showing up in the models at this time. PWAT values will likely be a tad lower than previous days, though they will still hover around 1.5", give or take a few tenths. As a result, still expect showers that develop to be efficient rainfall producers. Cloud cover shouldn`t be quite as extensive today, and with a decrease in cloud cover and rainfall activity, temperatures should warm into the low to mid 80s this afternoon. Lows overnight will again be in the mid to upper 60s. && .SHORT TERM /MONDAY AND MONDAY NIGHT/... As of 310 AM Sunday... The Bermuda high will maintain its dominance into early next week, effectively stalling the southerly progress of a backdoor front on Monday and lifting a tropically tinged moisture plume northward into the stalled frontal zone. The returning moisture plume features PW`s of ~1.75" and will result in an increased chance of convection, with thunderstorms becoming more numerous as we approach max heating - especially across the northern tier of central NC, where instability will be higher north of the frontal zone due to steeper mid level lapse rates. Highs will be in the mid 80s, perhaps suppressed to the lower 80s if early precip coverage is more widespread. Convective activity will shift to the north overnight, with a lull in activity, especially over the southern tier, after midnight. Min temps will be persistence, 65-70 degrees, in the tropical airmass. && .LONG TERM /TUESDAY THROUGH SATURDAY/... As of 310 AM Sunday... The moist tropical airmass in place will be reinforced on Tuesday as a short wave lifting out of the Gulf states is absorbed into broad troffing with nearly zonal flow across the eastern CONUS. This short wave and associated surface reflection will be moving east across the area, to maintain scattered convection featuring increased activity with the diurnal cycle Tuesday through later Wednesday. The persistent frontal zone and upper trof are nudged east and south early Thursday as ridging builds into the Plains. How far south and east are in question, with the GFS wanting to build cooler and drier high pressure across the Mid Atlantic and southward down the Atlantic coast quickly, which would keep us dry Thursday into the weekend. Conversely, the ECMWF would prefer to maintain the Bermuda high`s influence and maintain the tropical airmass through the late week, resulting in at least scattered, mainly diurnal convection. Will maintain slight chance PoPs through the late extended period with a very small downward nudge in the temperature forecast pending model consensus. && .AVIATION /12Z SUNDAY THROUGH FRIDAY/... As of 700 AM Sunday... 24-Hour TAF period: Expect cigs in the 800-1500 ft range to improve to MVFR and VFR over the next few hours at most locations. Isolated to widely scattered showers and thunderstorms are possible today across Central NC, but coverage makes it difficult to pinpoint specifics at any terminal. Should showers develop/move over a terminal, expect a brief period of sub-vfr conditions and possible thunder to accompany them. -KC Looking ahead: The weather pattern will change little through Thursday across central NC as the warm moist air mass remains in place. This will lead to a good chance of late night/early morning MVFR/IFR ceilings, followed by scattered afternoon and early evening convection. -RAH && .RAH WATCHES/WARNINGS/ADVISORIES... .None. && $$ SYNOPSIS...WSS NEAR TERM...KC SHORT TERM...mlm LONG TERM...mlm AVIATION...KC/RAH

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