Area Forecast Discussion
Issued by NWS Wilmington, NC

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000 FXUS62 KILM 222104 AFDILM Area Forecast Discussion National Weather Service Wilmington NC 504 PM EDT Fri Sep 22 2017 .SYNOPSIS... Building high pressure aloft from the north will bring dry but warm air across the Carolinas this weekend. Strong rip currents and large surf along the beaches, as well as hazardous marine conditions offshore will continue as Hurricane Maria moves northward through the Atlantic waters. The latest forecast puts Maria just over 400 miles east of the tip of Cape Fear by mid week next week. && .NEAR TERM /THROUGH SATURDAY/... As of 300 PM Friday...Since convection is struggling through the window of maximum insolation, diurnal cooling with our lowering ball of fire will put the curtail on convection into the late afternoon to early evening, leaving a clear sky tonight as the cumulus dissolves into the evening sky. Under clear skies and decelerating winds, patches of fog can be expected between 4am and 8am. Minimums will settle to 65-68 across most locals and low 70s near the beaches and ICW. The surfzone and area beaches will begin to possess a hazard as long period SE swell from distant Marie intensifies rip currents, while creating large and powerful breakers near shore. This will pose a threat to surf- waders, and even small children or elderly not in the water but standing by the oceans roar, where wave run-up can be speedy and strong, as wave periods will be on the order of 15 seconds, representing a high translational velocity into the surfzone. It is beyond this period however, namely Sunday, that the surf becomes large. For Saturday 4-7 ft breakers, and a `high- risk` of rip currents along all beaches. && .SHORT TERM /SATURDAY NIGHT THROUGH SUNDAY NIGHT/... As of 300 PM Friday...Although the weather will remain quiet, the seas and surf will not. The main impact this weekend will come from high surf and strong rip currents at the beaches. Otherwise, Jose will continue to churn in the northern Atlantic and Maria will continue its trek northward, while high pressure moves slowly east across the Great Lakes. The Carolinas will basically be under the influence of high pressure in the northeasterly flow between these systems. A weaker gradient flow initially will allow the sea breeze to dominate closer to the coast helping to produce a greater on shore flow Sat eve. The pcp water values will be near 1.3 inches closer to the coast and down near an inch in a drier NE flow Sat eve, but a boundary from Jose will shift south overnight Sat into early Sun. This will produce some clouds and perhaps a spotty shower over the waters. Otherwise expect mainly clear to partly cloudy skies and overnight lows in the mid 60s most places. The winds will pick up on Sun as gradient tightens with northerly movement of Maria which should reach about 500 to 600 miles to the southeast, but coastal Carolinas will remain in dry air and subsidence as ridge builds down over the area aloft and we remain on back side of extreme outer periphery of Maria. H5 heights will be up near 588 dm with 850 temps up near 16 to 17c. This will help to keep a dry forecast with warm temps up in the mid 80s for Sunday. Models show a some drier air advecting in overnight Sunday with slightly lower dewpoints which may shave a couple of degrees off overnight low, but still expected in the mid 60s. && .LONG TERM /MONDAY THROUGH FRIDAY/... As of 300 PM Friday...Hurricane Maria will be slowly making its way north well off the coast of the Carolinas through the first half of the week. Expected impacts will be dangerous surf and an elevated rip current risk from long period (15 sec) swells. This swell energy will translate into breaking waves as high as 10 to 15 feet along the beaches of New Hanover and Pender counties, and 6 to 10 feet along the beaches of Brunswick, Horry and Georgetown counties into Wednesday. The swell energy should begin to ease late Wednesday, but dangerous surf and an elevated rip current risk will likely continue into Friday. Northeast to north winds will be breezy along the coast, and gust occasionally into the 20-30 mph range by Tuesday-Wednesday. It will be a tough call at this point to determine how much peripheral moisture from Maria will affect the area, however it is reasonable to expect for the ILM CWA, that SE NC will have the best chance for precipitation based on the current forecast track of Maria. The highest PoPs, which will still remain less than 30% at this time, will be Tuesday into Wednesday, before the cyclone gets picked up by the westerlies on Thursday as indicated by both the GFS and ECMWF. Upper level ridging and subsidence west of the hurricane will likely result in a sharp sky cover gradient and temperatures remaining a few degrees above normal through the week. && .AVIATION /21Z FRIDAY THROUGH WEDNESDAY/... As of 18Z...Afternoon cumulus of SCT-BKN050 will prevail along the coastal interior with VCSH by mid afternoon. Any convection should dissipate after 00z this evening. A light onshore wind will guide the sea breeze front inland, and along this boundary is where a shower or storm will be favored. High pressure over the Great Lakes will push drier air southwestward today and Saturday. VFR conditions this evening may decrease to MVFR/IFR again late tonight in patchy ground fog, manly aft 9z. Extended Outlook...Mainly VFR conditions through the period with the exception of possible MVFR/IFR conditions due to low clouds and fog each morning, mainly between 9z-12z. && .MARINE... NEAR TERM /THROUGH SATURDAY/... As of 300 PM Friday...Although N through ENE winds this period will not be strong, increasing SE swell from Maria has prompted a `hazardous seas` advisory, effective from 6 AM Saturday through at least early next week, likely into mid-week, since Maria will slow down once offshore of the Carolinas. 4-7 foot SE waves every 15 seconds will produce turbulence and standing waves in area inlets during the outgoing tides, while increasing the width of the surfzone of tumultuous breakers. No TSTMS are expected through Saturday over the 0-20 NM waters. Onshore winds can be expected Saturday with high pressure to the north and Maria east of the Bahamas. SHORT TERM /SATURDAY NIGHT THROUGH SUNDAY NIGHT/... As of 300 PM Friday...High pressure will extend down from the Great Lakes this weekend as Jose continues to spin in the North Atlantic and Maria treks north from north of the Bahamas. A general northeasterly flow will increase heading into Sunday up to 15 to 20 kts in the outer waters, but otherwise winds will be in the 5 to 10 kt range. A very long period swell up to 11 to 15 seconds will continue through the weekend. An increasing northeast shorter period wind swell will combine with this longer period swell to produce an increase in seas from near 6 to 7 ft in outer waters Sat eve up to 10 to 12 ft Sun night into Monday. Expect shoaling and large breaking waves along the length of Frying Pan Shoals. A small craft advisory for hazardous seas mainly due to long period swells will continue through the period. LONG TERM /MONDAY THROUGH WEDNESDAY/... As of 300 PM Friday...Long period southeasterly swells will be ongoing Monday, ranging from as high as 8 to 10 feet every 15 seconds in the outer waters (15-20 nm). South of Cape Fear, these are likely to decay to 4 to 6 feet as they approach the coast, but north of Cape Fear, 6 to 8 footers will push in closer. Based on the latest forecast track for Maria, northerly winds will peak Tuesday night into Wednesday, with 20 to 25 knots north of Cape Fear. South of Cape Fear, a 15 to 20 knot range can be expected. Expect Small Craft Advisory conditions through the entire period. && .TIDES/COASTAL FLOODING... As of 300 PM Friday...A coastal flood advisory may be needed for downtown Wilmington and the lower Cape Fear but confidence is low because of the marginality. Therefor will allow a few more observations to arrive through afternoon, take into account departures before an issuance if any. If a coastal flood advisory is issued, the flooding itself will remain very minor. && .ILM WATCHES/WARNINGS/ADVISORIES... SC...High Rip Current Risk from Saturday morning through Saturday evening for SCZ054-056. NC...High Rip Current Risk from Saturday morning through Saturday evening for NCZ106-108-110. MARINE...Small Craft Advisory for hazardous seas from 6 AM Saturday to 6 AM EDT Tuesday for AMZ250-252-254-256. && $$ SYNOPSIS... NEAR TERM...MJC SHORT TERM...RGZ LONG TERM...CRM AVIATION...MJC MARINE... TIDES/COASTAL FLOODING... is the U.S. government's official web portal to all federal, state and local government web resources and services.