Area Forecast Discussion
Issued by NWS Wilmington, NC

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000 FXUS62 KILM 180707 AFDILM Area Forecast Discussion National Weather Service Wilmington NC 307 AM EDT Fri Aug 18 2017 .SYNOPSIS... High heat and humidity will continue across the area today. Showers and thunderstorms will increase in coverage Saturday ahead of a cold front. This front will stall in close proximity during the weekend before dissipating Monday. High pressure will build across the area Tuesday and Wednesday. Another cold front will approach from the northwest Thursday. && .NEAR TERM /THROUGH TONIGHT/... As of 300 AM Friday...The mid level pattern has shifted to more of a southwest flow or will be doing so in short order but the shift appears to have little impact on the forecast. Surface features are essentially the same as the past several days. A very tropical airmass still resides over the area with precipitable waters over two inches. The coverage of convection today should be a little less than Thursday as there are no additional triggers other than the standards (sea breeze and residual boundaries) like the upper level difluence we observed yesterday. The bigger story or a tired story by now is the heat. With heat indices over and in some cases well over 105 will hoist an advisory area wide. && .SHORT TERM /SATURDAY THROUGH SUNDAY NIGHT/... As of 300 AM Friday...A longwave trough across the eastern quarter of the nation Sat will lift out across the Northeast states Sat night and Sun. This deep trough will bring a cold front into portions of our area Sat before stalling as the brunt of the mid-level shortwave energy swings by to our N. The front should remain in close proximity and slowly dissipate late in the weekend and on Mon. As the trough lifts out Sat night and Sun, Western Atlantic High Pressure will expand westward across the Carolinas with heights building Sun and Sun night. The highest and deepest moisture content will be along the coast Sat, along and ahead of the front. Will carry high POPs as convection may be numerous to widespread here as the front interacts with the seabreeze. Models are attempting to bring drier air into inland portions of the Forecast Area on Sat. If this were to happen, then the risk for showers and storms would be less as you move inland from the coast. I did show a downward trend in POPs as you move inland Sat, but not as low as several of the models would indicate at this time. Increasing instability should allow for at least scattered thunderstorms, even well inland. Rainfall on Sat could be heavy at times. Did cut off POPs altogether Sat night, except along the coast where moisture convergence is still evident, strongest offshore. On Sun, a weakening front will be overhead or close by at the surface while ridging increases aloft. This suggests lower POPs are warranted, and have slight chance to chance with the highest probabilities for showers and thunderstorms along portions of the Grand Strand and South Santee River area. Considerable clouds and convection on Sat should keep highs around 90. Highs on Sun should be a degree or two warmer in some locations. The heat index should be below Heat Advisory criteria both days as dewpoints will be a degree or two less than in recent days. Still, it will feel as if it were near 100 and as uncomfortable as 104 degrees. Lows will be in the 70s. && .LONG TERM /MONDAY THROUGH THURSDAY/... As of 300 PM Thursday... Front appears to wash out completely by Monday leaving behind some weak troughiness. This doesn`t elucidate much regarding eclipse view especially along the coast since in such a setup cumulus development should be fairly widespread and vertically vigorous. Tuesday should represent the lowest rainfall chances during the period with a pinned seabreeze, zonal flow aloft, and a piedmont trough to our west. Energetic northwest flow and the next cold front arrive on Wednesday. This front may have a better chance than the early week boundary in clearing the area at least in part on Thursday as there is a stronger upper trough and higher surface pressures driving its progress. && .AVIATION /06Z FRIDAY THROUGH TUESDAY/... As of 06Z...Expect mostly VFR conditions through the period. The synoptic situation remains intact with slightly lower chances for convection later today via less forcing. The fog potential for this morning appears less as well with just a little more wind in the boundary layer. Extended Outlook...Potential for MVFR/IFR into the weekend with unsettled weather in association with an impending cold front. Additional possibility of patchy stratus/fog towards daybreak each day. && .MARINE...
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NEAR TERM /THROUGH TONIGHT/... As of 300 AM Friday...A little more wind across the waters this morning with buoys reporting south to southwest winds around ten knots or so. The flow will increase later this afternoon and especially overnight tonight with speeds increasing to an eventual range of 15-20 knots. The increase in winds will lead to an increase in seas from the current 1-2 feet to 2-4 feet by Saturday morning. I wouldn`t be surprised to see some five footers in subsequent guidance which may warrant a SCEC headline for tonight. SHORT TERM /SATURDAY THROUGH SUNDAY NIGHT/... As of 300 AM Friday...A front will stall upstream of the waters Sat and then slowly begin to dissipate late in the weekend. The strongest winds will occur Sat, up to around 15 kt. Wind speeds will decrease to 10 to 15 kt Sat night, and then near 10 kt Sun, trailing off to less than 10 kt Sun night. The direction will remain from the SW although scattered to numerous thunderstorms will likely corrupt the prevailing flow. Seas will be 3 to 4 ft Sat, subsiding to 3 ft Sun and to 2 ft by early Mon morning. Higher winds and seas will be possible in and near thunderstorms. LONG TERM /MONDAY THROUGH TUESDAY/... As of 300 PM Thursday...Very light southwesterly Monday with a cold front decaying into a weak surface trough. Seas will be running their fairly `normal` 2-3 and occasionally 4 ft. The trough may wash out for a time Monday night for some light and variable winds but it reforms Tuesday for a return of south to southwesterly flow, likely capped at 10kt.
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&& .ILM WATCHES/WARNINGS/ADVISORIES... SC...Heat Advisory from noon today to 5 PM EDT this afternoon for SCZ017-023-024-032-033-039-053>056. NC...Heat Advisory from noon today to 5 PM EDT this afternoon for NCZ087-096-099-105>110. MARINE...None. && $$ NEAR TERM...SHK SHORT TERM...RJD LONG TERM...MBB AVIATION...SHK

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