Area Forecast Discussion
Issued by NWS Raleigh/Durham, NC

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000 FXUS62 KRAH 291652 AFDRAH Area Forecast Discussion National Weather Service Raleigh NC 1250 PM EDT Wed Mar 29 2017 .SYNOPSIS... Weak high pressure will move over central NC today and remain in control through Thursday before low pressure brings unsettled weather to the area for Friday and Friday night. && .NEAR TERM /THROUGH TONIGHT/... As of 1250 pm Wednesday... Central NC will be under the influence of a very remote surface high centered over northern Ontario with building heights aloft as shortwave ridging shifts overhead. Widespread stratus with ceilings between 2 to 4kft, has overspread the area, as depicted by the HRRR and NAM, within the stable low-level NELY flow. Expect these low ceilings to lift and eventually scatter out into a stratocu layer. High temperatures ranging from mid to upper 60s NE , to mid/upper 70s southwest. It should remain mostly clear tonight, but an area of expanding stratus, developing within the 925-850mb SELY upslope flow along the higher terrain, is expected to spread into the western piedmont between 08 to 12z. Lows ranging from the mid 40s NE to mid 50s SW. && .SHORT TERM /THURSDAY AND THURSDAY NIGHT/... As of 405 AM Wednesday... Thursday will be quiet during the day as a meso-high develops over the Delmarva Peninsula which will throw temperatures into question a bit for Thursday afternoon. if flow remains southeasterly over the area, we should see temps near 60 degrees across the north with highs closer to 70s in the south. If flow remains more northeasterly temps could come in quite a bit cooler, especially across the north. By Thursday night, the first waves of precipitation associated with an approaching low pressure system will begin to overspread at least the western portions of the CWA, and perhaps everywhere by 12z Friday. Diurnal timing should keep most of this activity limited to convective showers as instability is non-existent. That being said, model soundings show every strong veering with height and wind profiles suggest bulk shear of 50 knots or so with a large heaping pile of helicity in the lowest levels of the atmosphere. Will certainly keep an eye on these details as they evolve. Lows Thursday night mainly in the 50s. && .LONG TERM /Friday through Tuesday/... As of 220 AM Wednesday... Fri/Fri night: Stormy weather for central NC, as a mid level low will move over the Ohio Valley and central Appalachians to off the Mid Atlantic coast, a path which models agree fairly closely on, although the ECMWF is much weaker with this low than the GFS/NAM. A band of vorticity trailing this low down through the Mid South and Gulf early Fri will swing ENE with a negative tilt through the central Carolinas Fri morning, accompanying enhanced upper divergence and high PW nearing 1.5". Models including the SREF, NAM, GFS/GEFS, Canadian, and MPAS are unanimous with widespread showers/storms Fri morning into the afternoon, so will have categorical precip chances, trending down a bit from the SW late in the day and into Fri evening as the trough axis and DPVA pivot to our ENE, bringing partial drying in the mid/upper levels. While the mid and low level lapse rates are generally under 7 C/km and the strongest forcing for ascent is on track to move through the area prior to peak heating, the GFS spreads surface CAPE of 800-1200 J/kg through cntrl/E NC Fri afternoon, buoyed by a surge of high surface dewpoints of 55-60F, and kinematics are quite strong with 40-50 kts of deep layer shear and 150+ m2/s2 of 0-1 km helicity, so we may still see a few strong to severe storms Fri, generating both large hail and damaging winds, as well as a tornado risk, especially near the northward-retreating surface frontal zone possessing strongly curved low level hodographs. Precip chances should be ending over the NE CWA late Fri night as the mid level low/trough starts heading off the Delmarva coast, with a trailing front working eastward through the NW Piedmont of NC. Expect highs in the upper 60s/lower 70s followed by lows in the low-mid 50s. Sat through Sun night: Fairly quiet weather this weekend. The surface front is likely to settle near the NC/SC border, with no strong push in either direction, as initial weak NW mid level flow behind the exiting trough is slowly supplanted by a mid level ridge axis shifting eastward over the Southeast by late Sun. There`s no polar air behind this front, as a somewhat mild high crosses the Great Lakes region and Northeast. But models do suggest that the northeasterly low level flow into NC will draw in enough low level moisture within the low level stable layer to generate nighttime and morning stratus Sat night/Sun morning and again Sun night, with partial mixing-out during the daytime Sun for partly to mostly sunny skies. Model thicknesses are generally slightly above normal Sat and near normal Sun, suggesting highs in the low-mid 70s Sat, lows 47-52 Sat night, and highs Sun 67-73. Lows Sun night in the upper 40s to lower 50s, with fair skies NE and increasing clouds SW as the surface high moves off the Mid Atlantic coast, yielding gradually strengthening overrunning flow from the SE. Mon through Tue: More stormy weather as yet another potent wave tracks from the S Plains E then NE through the lower Miss Valley, dampening slightly as it traverses the Mid South and Central Appalachians. Model timing differences of as much as 12 hours make it impossible to pin down the details at this range, but it appears likely that we`ll see good coverage of showers and storms from Mon afternoon well into Tue, with the potential for some of these to be strong, provided there isn`t too much weakening as the shortwave trough approaches. The active southern-stream-dominant pattern favors temps continuing a category or two above normal. -GIH && .AVIATION /12Z WEDNESDAY THROUGH SUNDAY/... As of 727 AM Wednesday... 24 Hour TAF Period: Mainly VFR conditions through the TAF period however there is some concern for MVFR ceilings as northeasterly flow comes into play this morning. In general, stratus has been sparse and not formed as quickly as anticipated this morning. GOES- 16 imagery shows a large area of stratus offshore of northeast NC spilling into extreme coastal areas. This may not make it into the CWA today yielding VFR conditions through much of the TAF period until the early Thursday morning hours when MVFR ceilings will be possible at the Triad sites. Some wind gusts to 15 knots are possible this afternoon. Long term: A low pressure system will cross the area on Friday through Friday night with the potential for showers and thunderstorms. High pressure with VFR conditions should return for the weekend. && .RAH WATCHES/WARNINGS/ADVISORIES... None. && $$ SYNOPSIS...Ellis NEAR TERM...CBL SHORT TERM...Ellis LONG TERM...Hartfield AVIATION...Ellis

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