Area Forecast Discussion
Issued by NWS Raleigh/Durham, NC

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124 FXUS62 KRAH 192245 AFDRAH Area Forecast Discussion National Weather Service Raleigh NC 645 PM EDT Sat May 19 2018 .SYNOPSIS... A moist and slightly unstable air mass will remain entrenched across central NC through the middle of the week. && .NEAR TERM /THROUGH TONIGHT/... As of 645 PM Saturday... ...Will cancel the Flash Flood Watch... With the 2.0" PWAT axis and best H8 moisture transport having shift east of the area, the heavy rain and flash flood threat has largely ended across the area. While a glancing shot from the shortwave trough dynamics lifting off to the N-NE will result in a slight uptick in convection across the NW Piedmont this evening, this area, including the Triad urban areas, has seen very little precip over the past 24 hours and thus should readily tolerate an additional 0.50-1.0" rainfall from the scattered convection expected to move through the area. Otherwise, a few showers probable on the periphery of our eastern and se sections due to proximity of the moisture plume and weak perturbations embedded in the plume. Lows tonight in the 66 to 71. && .SHORT TERM /SUNDAY/... As of 330 PM Saturday... Sunday, in the wake of the mid level trough to our north, the mean flow will be westerly. This will lead to a modest drying out of the atmosphere, with precipitable water values across the Piedmont near or slightly below 1.4 inches. Meanwhile the atmosphere will remain very moist across the se third of our forecast area, thanks to the continued presence of the moisture plume. A weak 850-700mb trough is projected to cross central NC Sunday afternoon. This feature will aid to focus low level convergence, leading to the development of scattered thunderstorms, primarily between 3 PM and 9 PM. Wind field aloft not supportive of organized/strong convection at this time, though torrential downpours will cause a renewed threat for localized flooding. It should be warmer Sunday afternoon with most places reaching the low-mod 80s. && .LONG TERM /SUNDAY NIGHT THROUGH SATURDAY/... As of 220 PM Saturday... Maritime Tropical airmass will remain over central North Carolina through Wednesday with dewpoints in the upper 60s to lower 70s. Diurnal heating and embedded disturbances in deep southerly flow will contribute to scattered convection each afternoon and evening with a lull in activity overnight and early morning. Any convection will have potential to produce very high rainfall rates given the near record level PWs. High pressure building across the Northeast Thursday may push a backdoor cold front into the area Thursday and Friday bringing a drier airmass and lower chances for convection. On Saturday, southerly flow returns bringing tropical airmass northward into central North Carolina and greater chance for convection. && .AVIATION /18Z SATURDAY THROUGH THURSDAY/... As of 145 PM Saturday... Numerous showers and a few thunderstorms will continue to traverse northward across central NC through early this evening. The showers will be most concentrated over the Coastal Plain, generally along and east of I-95. Widespread MVFR conditions due to ceilings and visibilities in showers will be common in this region. Across the Piedmont, variable ceilings ranging from MVFR in vicinity of KRDU to low end VFR in the Triad will occur. Convection will be isolated to scattered, primarily in proximity to RDU. Showers with heavy rain may threaten the Triad terminals by early evening. Aviation parameters may briefly improve late this afternoon-early evening with ceilings generally low end VFR. Ceilings are expected to lower back to the low end MVFR/IFR range after 06Z, and remain low through late morning Sunday. IFR/MVFR ceilings will occur until early Sunday afternoon. Afterwhich, ceilings will lift to the low end VFR. As the moist and unstable atmosphere heats up, scattered convection will occur. Expect MVFR parameters in proximity of the convection. 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 WATCHES/WARNINGS/ADVISORIES... .None. && $$ SYNOPSIS...WSS NEAR TERM...CBL SHORT TERM...WSS LONG TERM...Franklin AVIATION...WSS is the U.S. government's official web portal to all federal, state and local government web resources and services.