Area Forecast Discussion
Issued by NWS Wilmington, NC

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000 FXUS62 KILM 230705 AFDILM Area Forecast Discussion National Weather Service Wilmington NC 305 AM EDT Sat Sep 23 2017 .SYNOPSIS... High pressure over New England will maintain dry weather over the Carolinas through the weekend. Hurricane Maria is expected to move northward a couple of hundred miles east of the Carolina coast Monday through Wednesday. Hazardous boating conditions, strong rip currents, and large surf are all expected to develop. A cold front may reach the area Friday, bringing cooler weather for late next week. && .NEAR TERM /THROUGH TONIGHT/... As of 300 AM Saturday...Weak mid level troughing will gradually give way to 5h ridge over Great Lakes expanding south. Surface high under the 5h ridge will do the same, building south today and tonight. Clear skies today will allow strong diurnal heating but mid level subsidence and dry air, precipitable water is forecast to drop under 1.2 inch this afternoon, will work against the development of deep convection. Cannot rule out some flat cumulus, especially along the sea breeze, but skies will generally remain clear today and tonight. Temperatures will continue to run above climo with highs in the mid to upper 80s and lows in the mid 60s. && .SHORT TERM /SUNDAY THROUGH MONDAY NIGHT/... As of 300 AM Saturday...Closed 500 mb high pressure centered over Pennsylvania on Sunday will bridge across to the Bermuda High on Monday. This "bridging" process is occurring earlier and more strongly than models were thinking several days ago, and this has led to a westward trend in the predicted path of Hurricane Maria as it moves northward. Where over the past several days the storm was expected to follow 70 or 71 degrees longitude as it passed by the Carolina coast, we`re now thinking 73 or perhaps even 74 degrees longitude is more likely. The 500 mb ridge to our north will help sustain a subsidence inversion between 4000-6000 feet AGL Sunday that will lower to 3000-4000 feet on Monday. The stable and dry air aloft will help to keep weather conditions dry across the area both days, although it`s possible a few shallow maritime showers could push onshore into the Cape Fear area by Monday night, particularly if Maria moves as far west as some of the latest models are suggesting. Early morning low stratus is also a good possibility in this pattern. Despite two days of northeast flow 850 mb temps shouldn`t fall appreciably from where we`ve been over the past few days, remaining in the +15C to +17C range. Our forecast highs range from 83-86 near the coast to 86-88 both days. Overnight lows generally 65-70, warmest at the beaches. && .LONG TERM /TUESDAY 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 /06Z SATURDAY THROUGH WEDNESDAY/... As of 06Z...Anticipate tempo MVFR conditions at most sites through 12z. Exception will be at LBT and CRE where IFR BR is more likely. LBT has already been flipping between MVFR and IFR conditions and solid IFR with perhaps LIFR will be possible from 9Z through 12-13Z. Once fog mixes out VFR will dominate the remainder of the period with FEW/SCT cumulus around under patches of cirrus from time to time. Seas breeze will result in development of 5-8 kt onshore wind at coastal terminals this afternoon. 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 08z-12z. && .MARINE... NEAR TERM /THROUGH TONIGHT/... As of 300 AM Saturday...Northeast winds under 10 kt for much of today will start to increase later this afternoon or this evening. Gradient will start to tighten up as Hurricane Maria steadily moves north. Northeast winds will approach 15 kt late this evening and 20 kt by the end of the period. Seas will mainly be composed of swell from Maria, running 4 to 6 ft for much of the period before increasing to 4 to 8 ft by the end of the period. SHORT TERM /SUNDAY THROUGH MONDAY NIGHT/... As of 300 AM Saturday...1021 mb high pressure over the eastern Great Lakes on Sunday will move off the New England coast by Monday. Models have shifted farther west over the 24 hours with Hurricane Maria`s track, now expected to move northward along 73 or 74 degrees west longitude next week. That`s a good 100 miles closer to the North Carolina coast than our thoughts were this time last night, and could bring more of the peripheral winds from Maria`s west side to the area. Gusts as early as Sunday could reach 25 knots, and a Small Craft Advisory has been extended out through Wednesday for increasing northeasterly winds and for very large wave heights, particularly north and east of Cape Fear where combined seas as large as 12 feet could start showing up within 20 miles of the beaches by Sunday evening. LONG TERM /TUESDAY THROUGH WEDNESDAY/... As of 300 PM Friday...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. && .ILM WATCHES/WARNINGS/ADVISORIES... SC...High Rip Current Risk from 7 AM EDT this morning through this evening for SCZ054-056. NC...High Rip Current Risk from 7 AM EDT this morning through this evening for NCZ106-108-110. MARINE...Small Craft Advisory from 6 AM this morning to 6 PM EDT Wednesday for AMZ250-252-254-256. && $$ SYNOPSIS...TRA NEAR TERM...III SHORT TERM...TRA LONG TERM...CRM AVIATION...III is the U.S. government's official web portal to all federal, state and local government web resources and services.