Area Forecast Discussion
Issued by NWS Wilmington, NC
Issued by NWS Wilmington, NC
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119 FXUS62 KILM 262335 AFDILM Area Forecast Discussion National Weather Service Wilmington NC 735 PM EDT Thu Sep 26 2024 .SYNOPSIS... Rain chances will increase through the day today with greater impacts expected tonight into Friday morning as Helene passes west of the forecast area. The primary threat will be dangerous nighttime tornadoes with additional impacts from moderate to heavy rain, gusty winds, and minor coastal flooding expected. Cooler and drier high pressure returns into next week. && .UPDATE... For the early evening update I have increased pops for the next few hours across South Carolina as well as QPF amounts. High resolution guidance as well as the globals are insistent on a lull or dry slot developing shortly but no sign of it at the moment. Strong divergence aloft appears to be driving the persistent activity. Turning to the tornado threat late tonight through early to midday Friday...the situation remains unchanged. A strongly forced very outer band (shown by the guidance for several days) will move across the area from about 0800 UTC through about midday south to north. High resolution guidance while meandering a bit shows several updraft helicity swaths with the most favored area Cape Fear. && .NEAR TERM /THROUGH FRIDAY/... Unsettled weather will continue through Friday due to Helene. Current conditions show stratiform rain over NE SC with embedded heavier showers/storms. Scattered showers/storms are also in SE NC. Some rotation has been seen in these stronger storms, but nothing of concern has materialized in the area yet. The predominant concern will be tornadoes tonight into Friday AM as the main convective band moves through the area. The threat area will be mainly near the coast and will largely follow the rain bands. Some of these embedded stronger storms could also produce 50 kt wind gusts. Should rain bands start to train over the same area we could see the risk for localized flooding, but rainfall totals are still expected near 1-2 inches with locally higher amounts of +3 inches. For now the risk seems highest for our areas that received high rainfall from PTC8 in Brunswick and New Hanover Counties. For these areas, the soils are still mostly saturated, so it will take less time for them to feel the impacts of continued rainfall. && .SHORT TERM /FRIDAY NIGHT THROUGH SATURDAY NIGHT/... Large dry slot wrapping around the 5h low/Helene remnants combo continues to spread over the local area Fri night and Sat. Later Sat into Sat night, as the 5h low starts to drift east-northeast, some of the deep moisture wrapped into the low will work its way over the forecast area. This will lead to an increase in cloud cover Sat night, but does not translate into an increase in rain chances. The presence of deep dry air coupled with a bit of mid-level stability, associated with the dry slot, will limit rain chances. An isolated shower is possible along the immediate coast. Temperatures will run above climo with lows some 10-15 degrees above. && .LONG TERM /SUNDAY THROUGH THURSDAY/... Low pressure aloft, the system that absorbed Helene, will slowly move east across the Mid-Atlantic states Sun through Mon night. The trough axis shifts offshore early Tue, setting up an northwest flow aloft for the middle of the week. The proximity of the 5h low will keep rain chances in the forecast Sun and Mon afternoons, although coverage will be limited with best chances across NC. Tue will be the transition day between the exiting 5h low and somewhat unsettled conditions(Sun/Mon) and the deep northwest flow aloft and dry/fair weather(Wed/Thu). Tue has some potential for limited rain chances in the afternoon, although guidance has been trending drier. There may be some lingering tropical moisture Tue, but with drier air and high pressure moving in a solution with lesser coverage seems appropriate. Temperatures above climo Sun/Mon will trend toward climo for the middle of next week. && .AVIATION /00Z FRIDAY THROUGH TUESDAY/... Similar to other tropical events...convective bands will drive MVFR to even a handful of IFR observations for the next 12 to 18 hours basically at all sites. Used lower end MVFR conditions to address with the caveat that if a more pronounced/persistent band develops will need to amend down to IFR. Extended Outlook... VFR should return through the weekend under high pressure. && .MARINE... Through Friday...Hazardous marine conditions expected through the period due to Helene with worst conditions expected over the SC waters. Infrequent gusts to Gale force may be possible with the convective band over the NC waters as well more towards Friday morning. Later forecast updates could raise a Tropical Storm Warning for the NC waters if it`s deemed necessary. Otherwise, waterspouts will also be a concern as the convective band moves through, mainly tonight into Friday AM. Waveheights will be +10 ft come Friday morning where they`ll linger through the rest of the day. Friday night through Tuesday night...Small craft will be ongoing Fri night and will continue into Sat morning before seas drop below SCA thresholds. Southerly winds will be under 20kt Fri night, decreasing to around 10 kt Sat morning. Southerly flow continues into the start of next week with speeds 10 kt or less. Later Mon into Tue the flow becomes more westerly, but no change in speeds. Seas will steadily fall in response to the decreasing winds with 3-5 ft Sat falling to 3 ft Sun and 2-3 ft Mon and Tue. && .TIDES/COASTAL FLOODING... Minor coastal flooding remains a threat for the next several days, especially in NC. Minor flooding along the Lower Cape Fear River will impact both sides of the river during the afternoon high tides today. Onshore winds due to Helene are expected to produce additional coastal flooding this evening along the beaches as it moves northward from the Gulf of Mexico through the southeastern US. Normal water levels should return this weekend. && .ILM WATCHES/WARNINGS/ADVISORIES... NC...High Surf Advisory from midnight tonight to midnight EDT Friday night for NCZ106-108-110. Coastal Flood Advisory until 9 PM EDT this evening for NCZ107. SC...Tropical Storm Warning for SCZ017-023-024-032-033-039-054>056- 058-059. High Surf Advisory from midnight tonight to midnight EDT Friday night for SCZ054-056. MARINE...Small Craft Advisory until noon EDT Saturday for AMZ250-252. Tropical Storm Warning for AMZ254-256. && $$ SYNOPSIS...ILM UPDATE...SHK NEAR TERM...LEW SHORT TERM...III LONG TERM...III AVIATION...SHK MARINE...III/LEW TIDES/COASTAL FLOODING...