Area Forecast Discussion
Issued by NWS Wilmington, NC

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000 FXUS62 KILM 231318 AFDILM Area Forecast Discussion National Weather Service Wilmington NC 918 AM EDT Mon Apr 23 2018 .SYNOPSIS... An approaching storm system will bring wet weather the next day or two, along with windy coastal conditions, dangerous surf, and high beach tides. Easing winds and a warming trend will follow into mid-week in wake of this system. Several lows emerging from the Gulf states, will bring rain chances late Thursday into Friday, and again Saturday. Drying and seasonable temperatures are expected Sunday into early next week. && .NEAR TERM /THROUGH TONIGHT/... As of 334 AM Monday...Complex storm system moving into the TN Valley today will generate periods of widespread heavy rain over the forecast area today and tonight. First round of heavy rain is likely to spread over southwestern areas during the late morning hours, with period of light to moderate rain ahead of it. Although the surface warm front will be well south of the area strong low level moisture advection through the day, low level jet strengthens from 25 kt to 55 kt, is married to low level convergence, strong divergence aloft, and 850/700 mb frontogenesis. GFS/ECMWF also show 850 Theta E ridge just upstream from the forecast area, something which usually helps produce periods of heavy rainfall. Low level convergence really starts to increase late in the day and during the evening as the warm front moves closer to the region. Not sure the warm front will ever reach the area, the occluded surface low may end up moving into the area as the period ends. Forecast soundings show an extended period of near saturation through the column as well as increasing elevated instability late today and overnight. Surface layer remains stable through the forecast period, suggesting affects of deeper/stronger convection that is likely to develop during the second half of the period may remain disconnected from the surface. Cannot rule out strong wind gusts, especially with a tightening gradient pushing wind speeds over 30 kt late in the day and overnight. However, the chance for any strong/severe storms seems remote. Extended period of heavy rain seems highly likely, with potential for 2 to 4 inches of rain in some areas. Warm cloud layer is on the order of 3.5 km, right in the sweet spot for high rainfall efficiency. The good news is that the area has been relatively dry and heavy rain will be occurring over the span of a day or more. So while there is some potential for flooding, think overall the chances are low. Given the abundance of cloud cover and heavy rain/moisture it is not surprising that low temperatures will run well above climo and diurnal ranges will be limited. Less than 10 degrees for many areas. Highs will end up close to 10 degrees below climo. Will continue the coastal zones wind advisory with guidance continuing to shows sustained winds in excess of 20 kt along the coast (worth noting MOS typically is too low on sustained wind forecast). Couple the gusty winds with an abundance of rainfall and it becomes likely that broad leaf/shallow rooted trees will be susceptible to uprooting. && .SHORT TERM /TUESDAY THROUGH WEDNESDAY NIGHT/... As of 334 AM Monday...`Wet and Mild` begins the period, rain ongoing, but by now, the axis of greatest rainfall has shifted offshore, and a decreasing rainfall coverage and intensity trends takes root, as mid-level drying digs deeper, down to 850 mb by day`s end Tuesday. The `snap-back` of upper heights in wake of the upper cool pool, and S-SW low-level wind flow, will bring a warm-up into upper 70s or near 80 Tuesday and Wednesday. Hazards: Very rough surf early Tuesday. Urban and small stream flooding from 2-3 inch rainfall run-off, much from overnight, and locally higher and lesser in spots. Strong and gusty S-SE coastal winds Tuesday morning. Any of these could bring about additional or extended advisories, through Tuesday morning. && .LONG TERM /THURSDAY THROUGH SUNDAY/... As of 3 PM Sunday...May see a weak boundary or front drop down into the Carolinas early Thurs. The second low will track down from the Upper Midwest, becoming an open wave as it digs down into the lower Mississippi Valley by Thurs. The GFS and ECMWF both show this low moving northeast through the Coastal Carolinas Thurs night into Fri, but the GFS is deeper and showing greater QPF and winds overnight Thurs. By Friday, this system will lift off to the northeast with a decent day in store. The GFS and ECMWF differ quite a bit heading into the weekend with the GFS showing a much drier forecast. Either way, a trough will move across the east coast producing below normal temps through much of the late week period. && .AVIATION /13Z MONDAY THROUGH FRIDAY/... As of 12Z...Conditions will slowly deteriorate through the afternoon hours as low pressure and associated front move northeast. Light rain will overspread the CWA by mid to late morning as isentropic lift increases. Ceilings will hang on to VFR until this afternoon, except FLO as they are expected to lower to MVFR in a few hours. Tonight, heavy rain expected with ceilings and visibilities eventually becoming IFR . Easterly winds will be quite strong, with gusts to 30 kts possible. Extended outlook...Tue morning MVFR/IFR in heavy rain. late Tue- Fri VFR, except for possible MVFR Thu night. && .MARINE... NEAR TERM /THROUGH TONIGHT/... As of 334 AM Monday...Conditions will continue to deteriorate across the waters this morning with Small Craft Advisory conditions giving way to Gales later this morning. Sustained may struggle to reach 34kt given the below normal near shore water temps but gusts will frequently exceed 34 kt. Guidance is showing a low level jet over 50 kt developing later in the afternoon which continues into the evening. Strong onshore flow will persist into the evening before winds start to veer to southerly. The extended period of increasing onshore flow will build seas through the day and into the early evening. Double digit seas are likely across SC zones by mid afternoon and by the end of the day across NC zones. Conditions will remain treacherous through the end of the period. SHORT TERM /TUESDAY THROUGH WEDNESDAY NIGHT/... As of 334 AM Monday...An ugly and dangerous marine period to usher in Tuesday, but gradual improvement late Tuesday onward, as a low pressure system pulls away from the waters. Seas of 6-11 feet early Tuesday, will drop below 6 feet by daybreak of Wednesday, thus after the Gale, and Advisory will be needed to close out most of Tuesday. Rain may limit visibility to less than 1 NM Tuesday morning. Inlets will be turbulent in exposure to direct, onshore and strong winds, much of Tuesday. LONG TERM /THURSDAY THROUGH FRIDAY/... As of 300 PM Sunday...A cold front may drop in early Thurs with winds shifting around to a more N-NE direction on Thurs. Fairly low confidence forecast Thurs into Fri as another area of low pressure may affect the waters. Seas should drop down to 2 to 4 ft by Thurs morning. Winds and seas will be dependent on strength and track of low pressure late Thurs into Fri, but for now have left them in the 3 to 5 ft range, although the WNA shows potential for SCA conditions early Fri. && .ILM WATCHES/WARNINGS/ADVISORIES...
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SC...Wind Advisory until 5 AM EDT Tuesday for SCZ054>056-058-059. High Rip Current Risk until 8 PM EDT this evening for SCZ054- 056. NC...Wind Advisory until 5 AM EDT Tuesday for NCZ105>110. High Rip Current Risk until 8 PM EDT this evening for NCZ106- 108-110. Beach Hazards Statement until 8 PM EDT this evening for NCZ110. MARINE...Gale Warning until noon EDT Tuesday for AMZ250-252-254-256.
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&& $$ SYNOPSIS... NEAR TERM...III/JDW SHORT TERM...MJC LONG TERM...RGZ AVIATION...DL MARINE...

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