Area Forecast Discussion
Issued by NWS Raleigh/Durham, NC

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000 FXUS62 KRAH 251902 AFDRAH Area Forecast Discussion National Weather Service Raleigh NC 300 PM EDT Tue Apr 25 2017 .SYNOPSIS... Low pressure will move slowly northeastward over eastern North Carolina this afternoon, and then push off the Mid Atlantic coast tonight. High pressure will extend from the Atlantic westward into the Southeast states Wednesday through Thursday. && .NEAR TERM /through tonight/... As of 215 PM Tuesday... Lingering high water on many area roads and in creeks necessitated an areal flood warning through this evening for a large chunk of central NC. However, the heavy rain threat is done, and water should continue to recede on roads and in creeks. Flooding will persist, though, on many mainstem rivers (see hydro section below). The mid level low, stacked nearly atop the surface low, will move to the NE over coastal areas of NC through early evening, before passing off the Delmarva coast tonight. Confluent cyclonic low level flow acting on residual moisture favors a lingering threat of scattered showers on the W/SW side of the low into the evening as it pulls away slowly. A storm or two also remains possible over the far NE CWA, where observed mid level lapse rates are around 6-6.5 C/km, low level lapse rates are nearing 7 C/km, and MUCAPE is 500-1000 J/kg, thanks to some sunshine. Vorticity lobes pivoting around the low may also contribute to ascent. Will hold onto areas of chance pops into early evening. Drier air eventually building in from the WSW in the wake of the low overnight will lead to a clearing trend from SW to NE, with NE sections the last to see the benefits of downslope flow and falling dewpoints. Expect lows tonight in the lower 50s west ranging to around 60 in the far E. -GIH && .SHORT TERM /WEDNESDAY AND WEDNESDAY NIGHT/... As of 400 AM Tuesday... In the wake of the low pressure lifting up the Mid-Atlantic coast, low-level southerly winds and short wave ridging aloft will mark the return of sunshine and warming temperatures. Highs ranging from upper 70s NE to lower 80s south. Lows Wednesday night in the upper 50s to lower 60s. && .LONG TERM /THURSDAY THROUGH MONDAY/... As of 400 AM EDT Tuesday... Lead short wave trough will lift from the Mid MS/TN Valley NE into the Great Lakes on Thulate rsday with trailing sfc cold front expected to stall out west/northwest of the mtns. Associated convection is expected to be ongoing Thursday morning across Tn, Al, and Ga Thursday morning. However with the better trough dynamics/forcing lifting off well to the north Thursday afternoon and evening, the showers and storms should exhibit a steady decline/weakening trend as they cross the mtns Thursday afternoon/evening. Will leave isolated chances across the far western zones Thursday afternoon, otherwise it should remain dry with temperatures steadily rising in the SWLY WAA regime. Highs in the lower to mid 80s west to upper 80s central and eastern areas. The synoptic pattern will favor near record heat by Saturday, owing to a 590+dm H5 ridge, Bermuda highs and H7 anticyclone over SC. Thickness are progged at 1410m Saturday, 50m above normal and indicative of upper 80s to lower 90s. The main question is how quickly another shortwave ejecting out of the Central/Southern Plains, this one potentially stronger, will cause the ridge to retreat offshore a bit. Heights are forecast to lower slightly on Sunday, more so across western NC. Highs in the mid 80s west to near 90 central and eastern area. A cold front will bring the next chance for rain/storms to the area on Monday with cooler temps following on Tuesday. && .AVIATION /18Z Tuesday through Sunday/... As of 135 PM Tuesday... MVFR cigs and patchy showers (yielding brief MVFR vsbys) will dominate central NC terminals this afternoon, followed by gradual SW-to-NE improvement to VFR areawide late tonight. A strong and slow moving upper level low will track toward the NE over eastern NC for the rest of today, before shifting to our NE and off the Delmarva coast tonight. Low level moisture continues to rotate around this low this afternoon, with MVFR cigs over all but RWI, where dry air wrapping around the low has progressed inland from the coast, leading to VFR cigs there, although a period of MVFR cigs remains possible as the moisture over the Piedmont shifts to the NE behind the departing low. Cigs should lift to VFR by 00z at INT/GSO as surface winds become light from the NW, although the moisture circulating around the exiting low will keep a threat of MVFR to IFR cigs at RDU/FAY/RWI into the overnight hours, with RWI potentially not reaching VFR until 10-12z Wed morning. VFR conditions will prevail after 12z Wed areawide as a weak high pressure ridge noses in from the Atlantic. Surface winds will be mostly light and becoming W or NW through tonight. Looking beyond 18z Wed, shallow fog is possible early Thu morning within a light moist flow from the SW, followed by a better chance of MVFR/IFR fog/stratus each late-night through morning, Fri through Sun. A few storms with sub-VFR conditions are possible Sat and Sun afternoon. -GIH && .HYDROLOGY...
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As of 300 PM Tuesday... Rainfall across central NC over the past 48 hours ranged from 4 to as much as 8 inches across the Tar, Neuse, and Cape Fear river basins, with the heaviest amounts tending to fall across the upper and middle Neuse basin. Significant widespread flooding has largely receeded on smaller creeks and streams, and most roads have been re- opened. However, ongoing high water on some roads and on numerous creeks has prompted the extension of an areal flood warning for much of central NC through early tonight. This rain resulted in major river flooding on the Neuse river at Clayton, while downstream, Smithfield is expected to reach major flood stage this evening. Flooding at forecast points in the Tar river basin will reach moderate flood stage, while only minor flooding is expected at forecast points along the larger Cape Fear basin. See water.weather.gov/ahps2/index.php?wfo=rah for the latest forecasts and for additional information.
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&& .RAH WATCHES/WARNINGS/ADVISORIES... None. $$ SYNOPSIS...Hartfield NEAR TERM...Hartfield SHORT TERM...CBL LONG TERM...CBL AVIATION...Hartfield HYDROLOGY...mlm

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