Area Forecast Discussion
Issued by NWS Raleigh/Durham, NC

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000 FXUS62 KRAH 241944 AFDRAH Area Forecast Discussion National Weather Service Raleigh NC 340 PM EDT Mon Apr 24 2017 .SYNOPSIS... A strong and deep low pressure system will slowly cross the region through Tuesday, producing wet and unsettled weather. Behind this low, a ridge of high pressure will extend into the region for mid to late week. && .NEAR TERM /through tonight/... As of 320 PM Monday... With a few exceptions, rainfall so far has been steady and moderate, with numerous but minor flooding confined mostly to streets and high water in creeks. This should change over the next 9-12 hours as we increasingly tap into a greater depth of Atlantic-source moisture penetrating further inland, north of a surface low that will move northward over southeastern NC tonight (although models disagree on the exact track of this low). Low level easterly flow is expected to strengthen this evening into tonight north of the approaching surface low, with the strongest flow of 30-40 kts over northern sections of central NC, mainly along and north of the Highway 64 corridor. This will continue to draw anomalously high PW values into the area through tonight, as well as allowing the modified wedge boundary to shift further inland. The resulting enhancement of deep isentropic upglide will be vertically juxtaposed with focused upper divergence to the ENE of the mid level low, fostering efficient rain production with a warm layer nearing 3.5 km. And the additional lift generate via elevated convective elements, most likely over our SE and far S sections through this evening, may result in locally heavier rain rates and higher totals. Will leave the flood watch in place, as an additional 1.5-3.0" of rain is possible through tonight, with higher amounts focused along bands with embedded convection and particularly near the pivot point of any such bands as they become more W-E oriented with time tonight as the mid level low shifts eastward into SC. Temps should waver only a category or so through tonight at most, with many spots seeing steady temps through the night or a minor rise as warmer air shifts inland. -GIH && .SHORT TERM /Tuesday and Tuesday night/...
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As of 340 PM Monday... The mid level low is expected to track from NE SC across E NC Tue, before moving NNE just off the Delmarva/NJ coast Tue night. This low will be nearly vertically aligned with the surface low (or series of lows rotating about one another) over E NC. The strong low level jetting north of the surface low will shift northward into VA Tue morning, along with the upper divergence maximum, as the mid level dry slot punches in from the south, and this drying aloft will lead to diminishing chances for heavy rainfall. But the surface winds will remain from the N and be fairly light with the low to our NE, which should help lock in the cool/damp low level stable pool a bit longer, especially in the western Piedmont. PW values will have dropped but remain above normal, with both low and mid level lapse rates near or over 6 C/km, mainly over the eastern two-thirds of the forecast area. Have retained a chance of showers and isolated storms, higher east than west, through Tue, decreasing Tue evening as the mid level low exits and the column stabilizes and begins to dry further. Temps are tricky with a wide spread in model statistical guidance, not surprising considering that any amount of insolation will cause temps to jump up. Have held onto a scenario that reflects a longer-lived stable pool, suggesting highs from the mid 60s NW to the mid 70s in the far east-central CWA. Will trend pops down and out slowly Tue night, with skies trending toward partly cloudy everywhere except the NE, where a lingering low chance of showers will be retained overnight. Lows 53-58. -GIH
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&& .LONG TERM /WEDNESDAY THROUGH SUNDAY/... As of 330 AM EDT Monday... In the wake of the low lifting up the Mid-Atlantic coast, low-level swly flow and short wave ridging aloft will mark the return of sunshine and warming temperatures. Highs in the upper 70s to lower 80s Wednesday, warming into the lower and mid 80s by Thursday. On the southern periphery of dampening short wave energy lifting through the MS and Ohio Valleys NE into the Great Lakes, we could see isolated/slight chance of showers and storms Thursday night and Friday. Otherwise, it will remain mostly dry with the main weather headlines being the hot temperatures associated with the dominate subtropical ridge building across the SE US. Highs Saturday and Sunday in the upper 80s to lower 90s. && .AVIATION /18Z Monday through Saturday/... As of 155 PM Monday... High confidence in poor aviation conditions through at least 06z tonight. Thick IFR and occasionally LIFR based clouds will persist over central NC as a deep and strong low pressure system slowly crosses the area through Tue, exiting to our northeast Tue night. Periods of rain through 06z will affect all sites with occasional MVFR to IFR vsbys, along with the mainly IFR cigs. Cigs will slowly lift Tue morning to MVFR with decreasing vertical extent as drier air just off the ground arrives from the S. The rain will decrease in coverage and intensity later tonight, although scattered showers will persist after sunrise Tue as the core of the upper low passes overhead. Surface winds will be mainly from the NE at 7-12 kts through tonight, occasionally gusting to 15-20 kts during the evening and overnight hours, especially at GSO/RDU/RWI as an easterly low level jet at 1000-2000 ft AGL extends into the area. This low level jet may lead to a risk of low level wind shear at INT/GSO/RDU/RWI from late evening into the overnight hours. Surface winds will then decrease late tonight (after 09z) and become more from the N or NW Tue. Looking beyond 18z Tue, cigs should remain MVFR through Tue night, with infrequent MVFR vsbys in scattered showers, although cigs may drop back to IFR through Tue night especially at INT/GSO as a cool stable air mass persists there. After the low shift to our NE Tue night, high pressure ridging will take over, and we`ll see cigs rise to MVFR then VFR through Wed morning. VFR conditions will then dominate through Sat. -GIH && .HYDROLOGY... As of 330 AM Monday... ...Flood Watch remains in effect through 12Z Tuesday... Widespread heavy rain is expected to develop over central NC today into tonight. Storm total rainfall amounts of 3-5" are expected, with locally heavier amounts possible where the primary band of elevated convection pivots /persists the longest/. Flooding of local creeks and streams can be expected. Main stem rivers will experience significant rises in water levels this afternoon into tonight, particularly the Yadkin, Haw, Neuse, Tar, Roanoke, and Cape Fear. && .RAH WATCHES/WARNINGS/ADVISORIES... Flood Watch through Tuesday morning for NCZ007>011-021>028-038>043- 073>078-083>086-088-089. && $$ SYNOPSIS...Hartfield NEAR TERM...Hartfield SHORT TERM...Hartfield LONG TERM...CBL AVIATION...Hartfield HYDROLOGY...Vincent/RAH

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