Area Forecast Discussion
Issued by NWS Wilmington, NC

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000 FXUS62 KILM 211904 AFDILM Area Forecast Discussion National Weather Service Wilmington NC 304 PM EDT Thu Sep 21 2017 .SYNOPSIS...
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Isolated showers and storms can be expected through Friday as an upper trough lingers over the region. Seasonably warm and dry weather will prevail this weekend into next week, as an upper ridge expands over the area. Tropical storm Jose spinning off the New England coast will remain nearly stationary, but is expected to weaken through the period. Hurricane Maria will curve to the north, remaining east of the Bahamas Friday and Saturday, passing offshore of the Carolinas Monday through Wednesday of next week.
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&& .NEAR TERM /THROUGH FRIDAY/...
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As of 3 PM Thursday...Showers and storms dotting the radar as anticipated with a fairly high degree of randomness...only a slight concentration along the NC seabreeze (though little activity in coastal SC where cu fields first blossomed). Being fueled by the pairing of cold temperatures aloft and our very warm afternoon this activity will wane towards sunset, though perhaps slower than normal due to the very steep lapse rates these temperatures have yielded. The upper trough and cold pool linger into tomorrow albeit in a weakening state. Isolated showers and storms once again with fairly random coverage expected.
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&& .SHORT TERM /FRIDAY NIGHT THROUGH SATURDAY NIGHT/...
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As of 3 PM Thursday...Weak mid level troughing aloft remains in place through the period while surface high over the eastern Great Lakes builds south. This pattern tends to support weak diurnal convection, however mid level dry air and subsidence will keep the region dry for much of the period. The only exception will be possibility of diurnal convection lingering into Fri evening. There is not really any shortwave energy driving the convection on Fri and this should lead to activity weakening with the loss of heating. Temperatures will run well above climo with the exception being along the coast where highs will only end up a few degrees above climo due to the sea breeze/northeast low level flow.
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&& .LONG TERM /SUNDAY THROUGH THURSDAY/...
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As of 3 PM Thursday...A pleasant, seasonably warm and dry extended forecast in the cards, provided no surprises arise in the projected forecast track of Hurricane Maria, who is slated to pass slowly north but well offshore of the Carolinas Monday through Wednesday of next week. Aside from this, a pronounced upper ridge will dominate the synoptic pattern, providing the warm and mainly dry weather. Cross-sectional analysis through time shows exceptionally dry mid-level air through the long range period, keeping pop values very low, in the isolated to none category. The exception will be very late or just beyond the period next Friday, when a highly amplified upper trough begins to drop SE toward the East coast. This will begin to increase rain chances, while associated shear aloft begins to guide Maria off to the NE away from the Mid-Atlantic coast.
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&& .AVIATION /18Z THURSDAY THROUGH TUESDAY/...
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As of 18Z...Showers developing at this hour and they are expected to generate lightning within an hour or two. They will be very spotty in nature and never last long over a given location and so have relegated to VC all terminals. Activity will drop off or cease altogether around sunset. Most places will probably have bouts of MVFR visibility late tonight. Lower vis and perhaps even ceilings will be possible should any area see more substantial rainfall. Extended Outlook...Mainly VFR conditions through the period are expected with the exception of a few hours of early morning low clouds or fog most mornings through the period. The highest risk of IFR conditions will be in the 0900-1200Z timeframe each morning.
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&& .MARINE...
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NEAR TERM /THROUGH FRIDAY/... As of 300 PM Thursday...Pretty minimal conditions over the marine environment. There is no well defined piedmont trough and the normal west Atlantic high is disrupted and displaced by the circulations of Jose and Maria. Spectral wave plots still show a predominant swell but dominant wave heights will continue to be the diminutive wind wave through the period. SHORT TERM /FRIDAY NIGHT THROUGH SATURDAY NIGHT/... As of 300 PM Thursday...Winds will remain northeast through the period as surface high over the eastern Great Lakes builds south. Gradient will start to tighten a little later in the period as Hurricane Maria moves closer to the region. Speeds should be under 10 kt through Sat before increasing to 10 to 15 kt Sat night. Swells from Maria will begin reaching the waters late Fri or Fri night with seas building through much of the period. Small craft headlines may be needed as early as Fri night and seem likely for Sat and Sat night with seas peaking near 10 ft as the period ends. LONG TERM /SUNDAY THROUGH MONDAY/... As of 3 PM Thursday...Unfortunately for the marine community, this period will pose treacherous wave conditions with hazardous seas nearly a certainty as Maria approaches and passes slowly north, but off the SC/NC coast. The slow movement north will bring prolonged and dangerous marine conditions, as 5-8 foot seas Sunday build to 6-11 feet early next week, remaining elevated before a more notable subsiding trend late next week. In addition to the large waves, N winds will likely gusts to 25 KT Sunday through early next week as Maria passing slowly north well offshore. This will only throw another layer of hazard on top of an existing one. The energetic, fast moving long period energy will instigate turbulence in area inlets during the outgoing tides, and will produce larger than normal breakers near sand-bars while expanding the width of the surf zone. This will require multiple days of advisories, likely initiated by the weekend.
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&& .TIDES/COASTAL FLOODING...
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As of 3 PM Thursday...High tide on the Cape Fear River downtown will occur at 1127 PM tonight. There appears to be about a two hour window of Advisory-worthy coastal flooding. Advisory being issued with the afternoon package 03-05Z.
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&& .ILM WATCHES/WARNINGS/ADVISORIES...
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SC...None. NC...Coastal Flood Advisory from 11 PM EDT until 1 AM EDT tonight for NCZ107. MARINE...None.
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&& $$ SYNOPSIS...MJC NEAR TERM...MBB SHORT TERM...III LONG TERM...MJC AVIATION...MBB TIDES/COASTAL FLOODING...MBB

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