Area Forecast Discussion
Issued by NWS Raleigh/Durham, NC

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000 FXUS62 KRAH 240818 AFDRAH Area Forecast Discussion National Weather Service Raleigh NC 418 AM EDT Wed May 24 2017 .SYNOPSIS... A warm and moist air mass will hold over the area tonight. A warm front will lift north through North Carolina Wednesday, then a cold front will cross the area late Wednesday night through Thursday morning, followed by passage of a strong upper level trough Thursday afternoon. Quiet and dry weather will return Friday. && .NEAR TERM /THROUGH TONIGHT/...
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As of 842 PM Tuesday... ...Flood watch has been extended through Wednesday night ... Even though the Flood Watch is in effect through Wednesday night, there should be a lull in the significant rainfall for a period this evening into the overnight hours over the southern and eastern zones (Sandhills and Coastal Plain) - just behind a departing meso-low that brought the round of heavy rain and even the isolated tornado down south near Autreyville late afternoon. This weak low was currently over NE Johnston/Wilson County, moving NE along the nearly stationary boundary extending up into NE NC near Elizabeth City. The main area of heavy rain/isolated thunderstorms was pushing east and will be out of the Wilson, Tarboro, and Goldsboro areas by 9-11 pm or so. Radar confirmed the expected lull just in the wake of this departing system, with only scattered lighter showers expected through 200-400 am in the east and south. The nearly stationary boundary extended SW of the departing wave of low pressure through the Sandhills to near Charlotte into north Georgia. Additional widespread convection associated with the next wave upstream over GA extending into western NC is expected gradually weaken with time through the overnight hours. However, with the front lingering in place and dew points in the 70 degree range, with inflow from the south, the convection may be able to sustain itself longer than is forecast by the current hi-res models. For now, we will continue to carry chance POP overnight - except likely in the NW where more widespread showers are expected along and north of the boundary aided by the ENE flow combined with more upper support with the disturbance aloft tracking east across the central Appalachians. A general low overcast with areas of fog is expected overnight. Lows should hold in the upper 50s N but range into the upper 60s to near 70 south (where the juicy air resides just south of the front). Widespread convection is expected again, mainly Wednesday afternoon and night associated with the next strong vorticity maximum crosses the TN Valley and rolls out of the Mountains late in the day.
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&& .SHORT TERM /THURSDAY/...
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As of 410 AM Wednesday... A potent mid-upper low and associated pocket of cold temperatures aloft (~ minus 21C at 500 mb) will amplify across the Mid and Deep South through tonight, to the wrn Carolinas/wrn GA by 12Z Thu, before pivoting in negatively-tilted fashion off the coast of the Carolinas and srn Middle Atlantic coast by 00Z Fri. At the surface, the lead occluded/cold frontal zone and wrn bound of rich low level moisture, characterized by mid 60s to 70 degree sfc dewpoints, will have likely moved just east of the RAH Coastal Plain by 12Z Thu, while a trailing cold front now draped from the OH Valley SSwd across the lower MS Valley will lag and sweep east across central NC between 18Z Thu-00Z Fri. Between the two boundaries, the airmass over central NC will be characterized by surface dewpoints generally in the 50s, to perhaps low 60s in the Coastal Plain. Despite this only modest boundary moisture, strong and focused quasi-geostrophic forcing for ascent, and cold temperatures/steep lapse rates aloft accompanying the aforementioned upper trough/low, will prove supportive of variably to mostly cloudy conditions and the development of scattered to numerous showers and storms, mainly after 15-16Z, after probable brief drying and clearing after the lead frontal convection late tonight. While the aforementioned cold temperatures/steep lapse rates aloft, and associated low freezing levels generally between 8-10 thousand ft, will favor small hail in even marginally deep/reflective cores, a 60-70 kt SSwly speed max on ern fringe of the upper trough will support organized storm modes, including low-topped (splitting) supercells, given long and relatively straight forecast hodographs particularly between 3-6 km, which would be capable of producing severe hail and damaging straight line winds. This risk will be greatest mainly east of U.S. Hwy 1 between 16-22Z, before mid level flow weakens and veers with the closer approach and ultimate passage of the upper trough axis. High temperatures mostly in the 70s.
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&& .LONG TERM /THURSDAY NIGHT THROUGH TUESDAY/...
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As of 350 AM Wednesday... Dry conditions will return by Thu night, as the upper trough lifts away and weak high pressure expands across the sern states through early Sat. A warm front will develop newd across the central Appalachians later Sat and across the Middle Atlantic states by Sun; with a return to warmer and more humid conditions, and a chance of convection focused along and north of the front this weekend. Some storms may be severe, given relatively strong wind fields, and steep lapse rates related to a large plume of EML that will likely have overspread much of the sern U.S. and srn Middle Atlantic states, around the top of a progressive sub-tropical ridge along the Gulf coast. The next trough aloft will amplify and progress across the central U.S. early next week; and the associated surface low will lift across, and occlude over, the Great Lakes. The related cold front will likely settle east of the Appalachians and serve as a focus for primarily diurnal convection Mon-Tue. Continued warm, in the 80s.
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&& .AVIATION /06Z Wednesday through Sunday/... As of 125 AM Wednesday... IFR to LIFR conditions will dominate across central NC through mid morning, as a warm moist air mass combined with light surface winds supports low stratus. FAY, however, will see a few periods of MVFR to VFR clouds through this morning. Cigs are expected to rise to MVFR, with mostly VFR vsbys, by late morning (around 15z), perhaps reaching low-end VFR by early to mid afternoon (around 18z) as a warm front surges northward through the area with increasing mixing. Patchy light showers are expected through early afternoon, followed by more widespread showers/storms moving in from west to east during the mid to late afternoon. A period of IFR conditions in heavy showers and storms with gusty erratic winds are possible at all sites after 18z at INT/GSO and after 19z RDU/FAY/RWI, then MVFR to IFR conditions will likely last from 02z until the end of the TAF valid period with lingering rain. Some storms this afternoon into early evening may be strong to severe, with large hail and intense wind gusts. Looking beyond 06z early Thu morning, MVFR conditions are likely to dominate late tonight with decreasing rain chances from west to east overnight. Cigs should rise to VFR after 13z Thu, but there will be a good chance for showers with small graupel/hail during the day Thu as the axis of a powerful mid level trough swings through the area. Skies will clear out late Thu night, then VFR conditions should dominate Fri through Sun, although there will be a chance for a few storms late Sat into Sun as a cold front approaches. -GIH && .RAH WATCHES/WARNINGS/ADVISORIES... Flood Watch through late Wednesday night for NCZ007>011-021>028- 038>043-073>078-083>086-088-089. && $$ SYNOPSIS...Hartfield NEAR TERM...Badgett SHORT TERM...MWS LONG TERM...MWS AVIATION...Hartfield

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