Area Forecast Discussion
Issued by NWS Raleigh/Durham, NC

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000 FXUS62 KRAH 220807 AFDRAH Area Forecast Discussion National Weather Service Raleigh NC 407 AM EDT Mon May 22 2017 .SYNOPSIS... Low pressure will track northeastward through central NC early this morning. A weak front will hold over the area today into tonight. Another low pressure area will track along this front, crossing the area from southwest to northeast late tonight through Tuesday. This low will move northeast and offshore by Tuesday evening, with weak high pressure following Tuesday night. && .NEAR TERM /today through tonight/... As of 340 AM Monday... First challenge of the day is timing the band of moderate showers through central NC over the next 6-9 hours. These showers are associated with a surface low just N of the Charlotte metro area, along with an 850 mb trough and mid level perturbation. This surface low is expected to continue a NNW track through the Piedmont through the morning hours, with the showers (and perhaps a isolated storm or two over southern sections) pushing slowly eastward. Will maintain a period of likely to categorical pops translating eastward through the morning. In the wake of the mid level wave and 850 mb trough, subsidence and partial drying aloft with a westerly component to the light low level flow should yield diminishing rain chances by the afternoon. But the presence of a lingering surface trough through central NC along with continued high moisture in the low levels may lead to scattered convection developing this afternoon over the Coastal Plain, east of the trough, where the GFS indicates moderate CAPE and slightly elevated mid level lapse rates (although at just around 6 C/km, it`s far from impressive), with PW over 1.5". Deep layer bulk shear will be marginal this afternoon, at 15-25 kts, so don`t expect activity to be that numerous or organized. Will have slight chance pops NW with better chance late-day pops across the east and south, although there should still be a period of dry weather between this morning`s showers and the afternoon convection. Later tonight, however, the chance for showers and storms will increase once again from the SW, as a more potent mid level wave (now over E TX) approaches, accompanied by a strengthening surface low with a 35-45 kt low level jet on its SE edge. PW will rise further to over 1.75", and an impressive broad upper divergence maximum will also move overhead from the SW, in the right entrance region of a jet streaking from TN/KY into S Quebec. The deep moisture combined with what is likely to be strong stacked forcing for ascent will support a large area of rain and embedded storms, beginning in the predawn hours in the SW CWA, where pops will be trended up to categorical after midnight. With a warm and muggy air mass holding in place, expect highs today from the upper 70s NW to the low-mid 80s SE, with a period of partial sunshine likely. Lows tonight from the lower 60s NW to the upper 60s SE, as the frontal zone bisects the forecast area. -GIH && .SHORT TERM /Tuesday and Tuesday night/... As of 315 PM Sunday... To be updated shortly. && .LONG TERM /WEDNESDAY THROUGH SUNDAY/...
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As of 400 AM Monday... An initially (slightly) positively-tilted longwave trough from ern Canada to the srn Plains, including an embedded mid-upper low over the mid MS Valley at 12Z Wed, will migrate ewd and assume an increasingly negative-tilt as it pivots across the Carolinas and middle Atlantic states by Thu and Thu night. Perturbed and moist SSWly to Sly flow aloft will precede the trough, while height rises and ridging aloft will follow and expand ewd across most of the ern U.S. through the weekend. A complex pattern will result at the surface through the middle of the week, and one that will likely be somewhat similar to the one over the Carolinas during the past 24 hours. That is, a frontal zone will likely be draped SWwd from a series of waves passing across and offshore the Middle Atlantic coast, marking the srn periphery of weak ridging/CAD/low ovc extending across interior VA/NC, then extending NWwd as a warm front to a low over the wrn OH Valley. That front, edge of the CAD regime, and focus for convection, will then likely retreat Nwd with a narrow wedge of warm sector through the srn and wrn NC Piedmont during the day Wed, then through the remainder of central NC early Wed night, all immediately ahead of, and associated with, a triple point low that will develop and migrate across the wrn Carolinas (also similar to this morning). The trailing cold front and preceding warm conveyor belt, and associated axis of continued likely showers and chance of storms, will sweep ewd and across the Carolinas later Wed night, with brief drying and clearing probable through early Thu. Clouds will redevelop with heating, with an additional round of "instability-type" convection -- in cyclonic and CAA-bearing flow aloft-- and result in a chance showers and/or storms Thu afternoon, despite surface dewpoints that will likely have fallen into the 50s behind the aforementioned cold front/warm conveyor belt. 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 invof the front late Sat afternoon through Sun.
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&& .AVIATION /06Z Monday through Friday/... As of 230 AM Monday... Poor aviation conditions are expected during the first 6-9 hrs of the forecast period, as a band of showers and isolated storms crosses the area. IFR/LIFR conditions will persist at INT/GSO, with mainly MVFR conditions elsewhere through this morning, with a period of MVFR to IFR vsbys in showers lasting for a few hours at each site. Once this band of showers and storms passes east of the area by noon, cigs will gradually lift to VFR with only isolated showers expected after 18z today, and possibly a few storms near FAY/RWI this afternoon into early evening. Rain coverage will begin to increase again from the SW toward the end of the TAF valid period, although much of the showers and storms will hold off until after 06z late tonight. Looking beyond 06z late tonight (early Tue morning), cigs and vsbys will steady lower to MVFR/IFR at all TAF sites from SW to NE as a low pressure system approaches from the SW, bringing widespread showers and storms. These poor aviation conditions will dominate late tonight through much of Tue. A trend to VFR is expected Tue night as the low pushes to our NE and offshore, however sub-VFR conditions will return Wed into Wed night as a cold front approaches from the west. -GIH && .RAH WATCHES/WARNINGS/ADVISORIES... None. && $$ SYNOPSIS...Hartfield NEAR TERM...Hartfield SHORT TERM...WSS LONG TERM..MWS AVIATION...Hartfield

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