Area Forecast Discussion
Issued by NWS Raleigh/Durham, NC

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000 FXUS62 KRAH 190750 AFDRAH Area Forecast Discussion National Weather Service Raleigh NC 350 AM EDT Fri May 19 2017 .SYNOPSIS... High pressure anchored offshore will slowly weaken its grip on central NC Friday. This will allow a cold front to drop southward into our region late Saturday and Saturday night, then stall and dissipate near the South Carolina border Sunday. && .NEAR TERM /OVERNIGHT/... As of 1005 PM Thursday... Just a minor adjustment required to the near term forecast, mainly to introduce a minimal chance for a shower immediately north of the Triad and near/west of Roxboro. This is to account for the potential for a stray shower along a outflow boundary drifting southward from northwest NC/SW VA. Latest meso analysis depicts modest moisture advection at 850mb in this region which may be enough fuel to trigger a shower late this evening into the early half of the overnight. Otherwise variably cloudy skies expected overnight with temperatures gradually dropping into the mid-upper 60s. && .SHORT TERM /FRIDAY AND FRIDAY NIGHT/... As of 255 PM Thursday... Upper level ridging along the East Coast will begin to dampen as shortwave energy crosses from the Great Lakes into the Northeast. Increasing moisture and the pre-frontal trough will support the development of showers and thunderstorms Friday afternoon near the VA border. Sufficient instability (MLCAPE 2000-2500 J/kg) and bulk shear of 20-30 kts could support some multicell organization. While an isolated strong storm is possible, severe weather remains unlikely given marginal support. Shower and thunderstorm activity may linger overnight as the cold front sags southward toward the area. Highs in the upper 80s to 90. Lows in the upper 60s. && .LONG TERM /SUNDAY THROUGH THURSDAY/...
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As of 350 AM EDT Friday... Midlevel ridge axis positioned over the SE states Sunday morning will gradually shift east during the day. Meanwhile at the sfc, an old boundary along the nc/sc coast will gradually dissipate as flow veers to a more southerly direction with the aforementioned ridge shifting east. Models are suggesting that a few showers will be possible, particularly across our southern zones and later in the day, invof of the old boundary. Highs will range from the upper 70s north in the cooler airmass north of the boundary, to mid 80s south near the sc border along and south of the boundary. On Monday, a cold front assoc with a developing longwave trough over the Great Lakes, Ohio Valley, and Midwest regions will approach from the west and move across central NC during the afternoon. A band of showers and thunderstorms assoc with this front will move across the area during the daytime, thus likely POPs in the forecast for daytime Monday. The risk for rain will gradually end front west to east Monday night as the front exits. The period Tuesday through Wednesday looks potentially unsettled as the aforementioned longwave trough further deepens to our west and slowly moves east across the eastern third of the country, but the GFS and ECMWF differ in the finer details. For example, the GFS features dry/fair weather for Tuesday in the wake of Monday`s front, then rain on Wednesday as the next front moves across. Meanwhile, the ECMWF transports copious moisture northeastward across our area late Tuesday ahead of Wednesday`s front, resulting in good chance POPs both days. For now, will keep pops near climo on Tuesday, with increasing pops Tuesday night and Wednesday. Under the influence of ample cloudiness, daytime temps will be held to near normal values with above normal temps at night.
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&& .AVIATION /05Z FRIDAY THROUGH MONDAY/... As of 115 AM Friday... With the exception of some isolated pockets of fog/stratus, expect generally VFR conditions overnight. Shortwave disturbances traversing the region along with pre-frontal surface trough over western NC will support scattered convection this afternoon/early evening, subsequently affecting the northern terminals. Will include prob30 for convection at KINT and KGSO with the 06z taf package, with future updates possibly needing to add KRDU and KRWI. Surface winds will remain light from the SSW to SW through the period. Outlook: A cold front will settle into and at least partially through central NC Sat and early Sat night, then retreat back NEwd through central NC as a warm front on Sun. This feature will be accompanied by both scattered convection along it, and post-frontal IFR-MVFR ceilings on the cool side of it. Another cold front, numerous showers and storms, and sub-VFR conditions, will move east across central NC Mon through early Mon night. && .RAH WATCHES/WARNINGS/ADVISORIES... None. && $$ SYNOPSIS...WSS NEAR TERM...WSS SHORT TERM...30 LONG TERM...np AVIATION...CBL/MWS

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