Area Forecast Discussion
Issued by NWS Raleigh/Durham, NC

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000 FXUS62 KRAH 180206 AFDRAH Area Forecast Discussion National Weather Service Raleigh NC 1005 PM EDT Thu Aug 17 2017 .SYNOPSIS... A trough of low pressure at the surface will extend across the Piedmont of Virginia south into the Carolinas through Friday. A cold front will move across the area from the west late Friday into Saturday and then stall along the Carolina coast on Sunday. && .NEAR TERM /UNTIL 6 AM FRIDAY MORNING/...
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As of 1005 PM Thursday... 00Z upper air analysis depicts a weak zone of speed convergence exists between 850mb-500mb immediately west of central NC. This region of lift interacting with available moisture may trigger isolated convection overnight across central NC. This threat appears a bit higher over our western counties versus east. With precipitable water values around 2 inches in the west, any showers/storms will be efficient rain producers, dumping locally heavy/excessive rainfall. In addition, steering flow rather weak at 10kts. Otherwise, expect a mixture of clouds/stars until 08Z when areas of low clouds or fog will begin to develop, especially in the coastal plain. Muggy, with overnight temps in the mid-upper 70s.
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&& .SHORT TERM /6 AM FRIDAY MORNING THROUGH FRIDAY NIGHT/... As of 345 PM Thursday... Short wave ridging across the Carolinas will give way to falling heights as a short wave trough dives from the upper Midwest into the Ohio Valley by late friday night. The associated cold front will approach the southern Appalachians friday morning and then move across central NC Friday night reaching the coastal region of the Carolinas on Saturday morning. Another convectively active day is expected on Friday with widely scattered showers and storms expected to develop around midday, especially across the eastern Piedmont and Coastal Plain. Some of the higher resolution convection allowing models suggest that the majority of the convection will be attendant to the surface front and will move into the RAH CWA from the west late in the afternoon and then move southeast across the area during the evening. It will remain humid on Friday with dew points in the lower to mid 70s which combined with highs of 89 to 95 will result in heat index values of 100-105. Dew points today over performed and were in the upper 70s across the Coastal Plain and if that occurs again, a heat advisory would be needed. Will hold off for now and defer to the mid shift to issue any headlines. -Blaes && .LONG TERM /SATURDAY THROUGH THURSDAY/... As of 341 PM Thursday... A short wave trough axis will cross the area during the day and evening Saturday, thus a few scattered showers may reform along the stalled front near the coast...so best chance for rain on Saturday and Saturday evening will be east of I-95. Any showers over our area should end shortly after sunset with dry conditions Saturday night. Sunday looks mostly dry as ridging aloft to our south begins to build northward over our area. Then for Monday, the forecast has been trending better the past few model runs, regarding cloud coverage and rain chances, although we`re keeping an eye on the weak short wave in the westerly flow aloft, which both the GFS and ECMWF suggest will pass by mostly to our north, but heights over us do trend down during the day. For now will hold cloud coverage around 50% with PoPs slightly below climo...20-30% during the afternoon Monday. The pattern for the rest of the long term period will feature a deepening through over the East, so look for mostly diurnal chance PoPs each day Tue-Thu. Temps Sat-Mon will run a couple degrees above normal with a building ridge, then falling back to or below normal mid-late next week with the deepening trough. && .AVIATION /00Z FRIDAY THROUGH TUESDAY/... As of 840 PM Thursday... 24 Hour TAF Period: VFR conditions are generally expected to continue this evening, with a small chance of a shower and/or storm at KGSO/KINT. Another rounds of sub-VFR fog and/or stratus (low end MVFR to IFR/LIFR) is again expected across eastern portions of the area early Friday morning, possibly lingering until mid morning. A cold front will approach the area from the west Friday, with an associated band of showers and storms expected to move into the region late in the day. Thus, have included mention of storms at KGSO/KINT late in the day (from 20Z onward in a prob30 group). Further east we may see showers and storms initially develop along a surface trough located across eastern portions of central NC during the early to mid afternoon, before another round of storms potentially affects eastern portions of the area on Friday evening/early Saturday morning. Outlook: The aforementioned cold front will shift southeast on Saturday and Sunday with any isolated to scattered diurnal convection expected to generally be south and east of the area (with a small chance at KFAY each day). && .RAH WATCHES/WARNINGS/ADVISORIES... None. && $$ SYNOPSIS...BLAES NEAR TERM...WSS SHORT TERM...BLAES LONG TERM...NP AVIATION...BSD/BLAES

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