Area Forecast Discussion
Issued by NWS Raleigh/Durham, NC

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000 FXUS62 KRAH 181747 AFDRAH Area Forecast Discussion National Weather Service Raleigh NC 147 PM EDT Sun Jun 18 2017 .SYNOPSIS... A warm, moist, and unsettled air mass will remain in place today through Monday. A cold front will move slowly into the area from the northwest Monday night through Tuesday. && .NEAR TERM /Today through tonight/... As of 905 AM Sunday... MVFR ceilings across the area this morning do show some signs of dissipation on GOES-16 visible imagery. At this time scattering out should occur from south to north as South Carolina is mostly clear at this time and the edge of the stratus continues to advance northward. Going to hold steady on temperatures for now in the lower 90s because heating should have plenty of time to recover after clouds burn off. Otherwise, previous discussion applies. -RTE Coverage of convection should be a bit lower today than in previous days, thanks to drying aloft of sufficient magnitude to result in reduced PW across the area. The cold front currently spanning the Midwest, from the Great Lakes down to the southern Plains, will continue to ease slowly to the ESE today. Its approach combined with the presence of the strong Atlantic ridge will lead to a tightening MSLP gradient and a southerly breeze over NC today, a contrast to the stagnant air and light winds of recent days. The vast majority of the area saw ground-moistening rain yesterday, and as a result we`re already seeing low stratus across the area. These clouds should persist through the early to mid morning, followed by lifting and dispersion, allowing for partly to mostly sunny skies today. The GFS shows slightly higher deep layer shear (15-20 kts) than in the last few days, and MUCAPE is projected to rise to 1000-2000 J/kg this afternoon, mainly over the Coastal Plain. But the lower water content today (PW down to 125-135% of normal) and an apparent lack of a focus for convection should limit coverage. Thus, will stick with just scattered showers/storms this afternoon. This is in line with the sparse coverage seen on convection allowing models including the HRRR and NAM Nest. An isolated strong storm or two is still possible, but the continued weak mid level flow and lack of dynamic contribution to lift will greatly curb this risk. Highs today 88-92, with thicknesses above normal and several meters higher than yesterday. Any showers/storms should dissipate soon after nightfall with a loss of heating and subsequent stabilization. Redevelopment of shallow late-night stratus is likely overnight. Lows in the lower 70s. -GIH && .SHORT TERM /Monday through Monday night/... As of 400 AM Sunday... Good coverage of storms will resume on Monday/Monday night as the cold front moves to a position along or just east of the Appalachians. Mid level winds will continue to strengthen from the SW, reaching 30-40 kts as the large polar stream trough driving the surface cold front moves through the Great Lakes region. This trough will induce modest height falls over NC, but upper divergence will be on the upswing in the right entrance region of the jet streak on the east side of the trough, and DPVA will improve as well as the southern stream shear axis to the SSE of the polar trough shifts into the region. Mid level lapse rates will rise slightly to 6.0-6.5 C/km, contributing to MUCAPE peaking at 1200-2000 J/kg, acting on PW values that will have rebounded back up to 1.75-2.0" by late in the day. These factors all support convection coverage rising to 60-80% through the day, with high pops persisting into the night as the front draws closer. We should see a greater threat of strong to severe storms, given the expected CAPE and better deep layer shear, in conjunction with increasing 0-1 km bulk shear to 25-30 kts and 0- 1 km helicity approaching 150 m2/s2. Damaging winds still looks to be the biggest threat, with a lesser threat of large hail. Shower/storms chances will linger through the night as the front pushes slowly into the area. Highs 85 to 91, and lows in the lower to mid 70s. -GIH && .LONG TERM /TUESDAY THROUGH SATURDAY/... As of 342 AM EDT Sunday... A potentially cloudy and unsettled long term period appears to be in store for central NC. First for Tuesday and Wednesday, a longwave trough slowly moving across the Great Lakes and Mid-Atlantic will leave behind a sfc boundary stalled across NC as the trough lift outs on Wednesday. Of these two days, it appears the best chance for rain for our area will be on Tuesday with the trough axis just to our west and the sfc boundary stretched across our CWA. On Wednesday, the better chance for rain should shift east of I-95 as the trough axis moves east. Thereafter, the forecast will largely depend on what happens regarding a sfc low of tropical origins in the GOM. The GFS still lifts it northward toward and across the FL panhandle, while the ECMWF takes it west toward TX. Either way, a plume of tropical moisture on the E/NE side of this low appears to break off and head toward our area during the latter half of the week, leading to another round of increased rain chances. The main questions is its arrival time, as the GFS brings the moisture and increased rain chances across our area on Thursday and Thursday night, while the ECMWF brings it across late Friday into early Saturday. Given this uncertainly, will carry above-climo pops Thursday through Saturday. Fortunately for now, model QPF values with either solution is not particularly high, but will continue to closely monitor trends. Given the cloudiness and rain chances, will lean toward near- or slightly below-normal temps during most of the period. && .AVIATION /18Z Sunday through Friday/...
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As of 145 PM Sunday... 24 Hour TAF period: Some MVFR ceilings remain across the central and northern portions of the forecast area but these are deteriorating and all sites should be VFR shortly. This afternoon wind gusts will become more prevalent out of the south at 15-20 kts. Convection should be more scattered than the last several days but an isolated strong storm or two cannot be ruled out with damaging wind gusts the most likely severe threat. Overnight expect low stratus to once again overspread much of the CWA with IFR/MVFR ceilings possible. Long term: A frontal system will approach central NC on Monday and linger in the area through Wednesday. Uncertainty surrounding a low pressure center coming out of the Gulf of Mexico leaves a low confidence forecast for the end of the week.
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&& .RAH WATCHES/WARNINGS/ADVISORIES... None. && $$ SYNOPSIS...Hartfield NEAR TERM...Ellis/Hartfield SHORT TERM...Hartfield LONG TERM...np AVIATION...Ellis

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