Area Forecast Discussion
Issued by NWS Raleigh/Durham, NC

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000 FXUS62 KRAH 170720 AFDRAH Area Forecast Discussion National Weather Service Raleigh NC 320 AM EDT Thu Aug 17 2017 .SYNOPSIS... A surface low pressure trough will extend from western North Carolina through South Carolina today through tonight. This trough will shift northeastward late tonight, and then hold over the Piedmont Friday through Saturday. && .NEAR TERM /OVERNIGHT/... As of 1000 PM Wednesday... Little adjustment required to the near term forecast. An isolated heavy rain shower dumped over 2 inches in an hour over north central Guilford, per observation from CoCoRAHS report. This particular cell seemed to be feeding along a tight low level moisture gradient while the lack of overall movement due to relatively weak flow below 500mb. This cell also aided by a weak perturbation aloft drifting sewd across the piedmont. This heavy shower has greatly diminished in intensity since 0120Z. Other isolated heavy showers over the southern Piedmont exhibiting the same characteristics, demonstrating a weakening trend since 0120Z. Through 05Z, cannot rule out an isolated shower as the small perturbation aloft continues to drift sewd, exiting our region after midnight. Overnight, areas of low clouds and fog appear highly probable over central NC thanks to the tropical-like air mass in place. Min temps in the low-mid 70s. && .SHORT TERM /THURSDAY THROUGH THURSDAY NIGHT/... As of 300 PM Wednesday... A short wave ridge axis over the Carolinas on Thursday morning will give way to decreasing heights and an increasing southwesterly flow on Thursday night. An increasing southerly flow will develop allowing a recovery of moisture with precipitable water values climbing back to between 2.0 to 2.25 inches by Thursday evening. While the forcing for ascent is modest, the return of warm advection and increasing moisture should result in an uptick in showers and thunderstorms over today. After a period of morning stratus in the Coastal Plain and northeast Piedmont, expect variably cloudy skies. Low-level thickness values increase a few meters supporting highs between 89 to 94 with lows in the lower to mid 70s. -Blaes && .LONG TERM /FRIDAY THROUGH TUESDAY/... As of 335 AM Thursday... A strong low pressure system moving north of the Great Lakes will move eastward and drag a cold front across the Carolinas on Friday and Friday night before stalling out near the Carolina Coast. This will keep precip chances in the forecast for Friday and but should confine things to the extreme southeastern portions of the area by Friday night. With the leftovers hanging around for much of the weekend expect eastern areas to maintain higher precip chances through much of the weekend. As the weekend comes to a close, continental high pressure will move in from the northwest which could help to lower precip chances by Sunday afternoon/evening. Interesting forecast for the eclipse on Monday with models starting to come into agreement with zonal flow aloft and surface high pressure sitting right off of the Carolina Coast. The positioning of the high pressure will most likely yield moist return flow around the back side of the high which unfortunately would most likely lead to at least partial cloud cover for Monday afternoon. That being said, the GFS solution is interesting that it lags the continental high back to the west a little bit and if that happens it could potentially suppress cloud cover to the south. Still way too early tell but at least a partly cloudy forecast looks likely. For midweek return flow around the high will continue, bringing daily precip chances with another surface low well to the north that may bring another front through the area by later on Wednesday. && .AVIATION /06Z THURSDAY THROUGH MONDAY/... As of 125 AM Thursday... An area of IFR conditions is expected early this morning over northeast portions of central NC, including RWI, where vsbys have already dropped to MVFR in fog. Confidence is high that RWI will see mainly IFR conditions developing, peaking 08z-12z this morning. RDU and FAY will see a lower threat of IFR conditions, although MVFR fog is still possible at these two sites. INT/GSO will see only a slight chance of sub-VFR conditions this morning. After 13z, cigs/vsbys at RWI are expected to improve to VFR by 15z. VFR conditions will then dominate through the day, although scattered showers and storms generating a period of sub-VFR conditions and erratic winds will be possible at each site, mainly 18z-00z. VFR conditions should prevail this evening into tonight, although MVFR fog may develop starting around 05z. Winds will be light and variable this morning, becoming mostly from the south by midday, at 6-10 kts this afternoon diminishing to 3-6 kts starting this evening. Looking beyond 06z Fri, good chance of MVFR fog at all sites 06z- 12z, followed by VFR conditions after 13z. Scattered showers and storms are possible mainly mid afternoon through mid evening Fri, although additional isolated storms remain possible through Fri night, with a chance for sub-VFR fog/stratus. Best shower/storm chances shift to our SE for Sat into Mon, with VFR conditions prevailing, although FAY may continue to see a storm threat. -GIH && .RAH WATCHES/WARNINGS/ADVISORIES... None. && $$ SYNOPSIS...Hartfield NEAR TERM...WSS SHORT TERM...BLAES LONG TERM...Ellis AVIATION...Hartfield

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