Area Forecast Discussion
Issued by NWS Raleigh/Durham, NC

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000 FXUS62 KRAH 231906 AFDRAH Area Forecast Discussion National Weather Service Raleigh NC 305 PM EDT Fri Jun 23 2017 .SYNOPSIS... The remnants of Tropical Cyclone Cindy will track northeast through the Tennessee valley this afternoon and eastward into the Mid- Atlantic tonight. A cold front will approach the region from the northwest on Saturday and progress slowly southeast through the Carolinas Saturday night as the remnants of Tropical Cyclone Cindy track offshore the Mid-Atlantic coast. && .NEAR TERM /THROUGH TONIGHT/... As of 135 PM EDT Friday... Today: A large moisture/instability gradient was present over central NC at 16Z, with MLCAPE ranging from ~500 J/kg in the Triad to 1500 J/kg along/east of I-95. H85 dewpoints ranged from 11-12C in the W/SW Piedmont to 14-15C in the Coastal Plain. Though further destabilization may occur in the Coastal Plain through early afternoon, instability should decrease by mid/late afternoon as a much drier H85 airmass (dewpoints 6-10C in GA/SC) advects into central NC from the southwest. With a ridge centered just offshore the SE coast, small amplitude waves and/or MCVs embedded in SW flow aloft in advance of Cindy`s remnants should remain well NW of the area this afternoon. As a result, forcing in central NC will be confined to mesoscale features such as the seabreeze and diff heating boundaries. With the above in mind, a slight chance of convection cannot be ruled out in assoc/w the seabreeze in the far SE Coastal Plain this afternoon where instability will be relatively greatest. Expect highs ranging from the mid/upper 80s NW to lower 90s SE. Southwest winds will increase to ~15 mph sustained with gusts to 25 mph by late afternoon. Tonight: Scattered convection will be possible overnight as Cindy`s remnants track northeast from the TN valley into the Virginias and low-level moisture/upper forcing increase across W/NW portions of the state. Expect the relative best potential for convection along/west of Hwy 1 between midnight and sunrise. Low-level flow will strengthen considerably overnight as the height gradient tightens between Cindy`s remnants to the N/NW and high pressure offshore the SE coast. Forecast soundings suggest a southwest wind sustained at 15-20 mph with gusts up to 30-35 mph, primarily after midnight. Wind gusts exceeding 35 mph cannot be ruled out in assoc/w convection in the NW Piedmont, however, damaging winds appear unlikely given poor diurnal timing /weak low-level lapse rates/, as reflected in the Day 1 outlook which confines severe wind probs along/west of the Blue Ridge. -Vincent && .SHORT TERM /SATURDAY THROUGH SUNDAY/... As of 135 PM EDT Friday... A cold front will approach the central Appalachians from the NW late tonight. With the remnants of Tropical Cyclone Cindy progged to track a bit further N/NW of central NC than previously anticipated, the cold front is not expected to progress into central NC until Sat evening/night. With central NC on the eastern periphery of the pre- frontal trough, rich low-level moisture is likely to persist through the afternoon. Strong insolation and rich low-level moisture are expected to yield moderate instability by mid/late afternoon, ranging from ~1000 J/kg in the NW Piedmont to ~2000 J/kg in the SE Coastal Plain, in the presence of 30-40 knots of deep-layer shear. Convection allowing models suggest scattered convection will develop within the pre-frontal trough in vicinity of the I-77 corridor by mid/late afternoon (19-20Z), then quickly grow upscale into a SW-NE oriented line that progresses E/SE through central NC between 21-00Z (roughly). Though diurnal timing will be optimal, rich boundary layer moisture /relatively low T/Td spreads/ will yield marginal DCAPE (500-750 J/kg) and line-parallel (southwesterly) deep-layer shear will not favor new updraft development at the leading edge of the consolidated cold pool. As a result, the potential for damaging winds appears relatively marginal /isolated/. Expect highs ranging from the mid/upper 80s (NW) to lower 90s (SE). -Vincent Saturday night and Sunday, a sfc boundary trailing behind a low pressure system crossing the northern Mid-Atlantic, will cross central NC Saturday night and Sunday. This front interacting with a moisture rich air mass will support the development of scattered- numerous showers and thunderstorms Saturday evening. Bulk of convective will dissipate overnight Saturday night though isolated- scattered showers still probable due to the presence of the front and available moisture. By Sunday, the main focus for convective development should be primarily east and south of Raleigh as the front should lie in this vicinity. Nwly flow behind the front will advect a drier more stable air mass into the Piedmont Sunday, leading to drier conditions. -WSS && .LONG TERM /SUNDAY night THROUGH FRIDAY/...
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As of 305 PM EDT Friday... The drier air mass will overspread the remainder of central NC late Sunday and Sunday night. Monday shaping up to be warm and dry with wly flow aloft and a sfc high positioned over the TN Valley. A s/w in the northern stream projected to drop sewd across the lower OH Valley Monday night, and cross central NC Tuesday. 12Z ECMWF more adamant about the potential for lift and isolated/scattered showers compared to the drier GFS. Based on the favorable timing, potential will exists for isolated-scattered showers, primarily late morning through the afternoon. A modifying Canadian high pressure system will initiate a stretch of dry and relatively pleasant conditions (ie. less humid) across central NC Wednesday into Thursday. By Friday, return flow on the back side of the retreating high will signal a return to warm and humid conditions by the end of the week. No signals noted for extreme heat across our part of the country through the next 5-7 days. In fact, high temperatures Tuesday and Wednesday will likely average 3 to 8 degrees below normal. The modifying air mass Thursday and Friday will permit temperatures to return to seasonal norms.
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&& .AVIATION /18Z FRIDAY THROUGH WEDNESDAY/... As of 135 PM EDT Friday... 24-HR TAF Period: VFR conditions are expected to prevail this afternoon/evening. Sub-VFR conditions associate with showers/storms will be possible between 04-10Z, primarily at the INT/GSO/RDU terminals. MVFR/IFR ceilings will be possible at all terminals during the pre-dawn hours, though confidence is lower than average, particularly at eastern terminals. Expect southwest winds at 10-15 knots with gusts to 20-23 knots this afternoon. Gusts may cease for a few hours after sunset, however, winds are expected to increase to 15-20 knots sustained with gusts to 30 knots AOA midnight as the height/mslp gradient tightens between Cindy`s remnants to the N/NW and high pressure offshore the Southeast coast. Winds will decrease to 10-15 knots by sunrise Sat. VFR conditions are expected to prevail at the end of the 18Z TAF period. Looking Ahead: Thunderstorms will be possible at all terminals late Saturday afternoon/evening, ~21Z at the INT/GSO terminals, ~23Z at the RDU terminal, and ~00Z at the FAY/RWI terminals. Isolated wind gusts to 35-50 knots will be possible in association with the strongest storms. Sub-VFR ceilings cannot be ruled out Saturday night and Sunday at eastern terminals. VFR conditions will prevail Sun-Wed as dry high pressure builds into the Carolinas from the northwest. -Vincent && .RAH WATCHES/WARNINGS/ADVISORIES... None. && $$ SYNOPSIS...Vincent NEAR TERM...Vincent SHORT TERM...Vincent/WSS LONG TERM...WSS AVIATION...Vincent

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