Area Forecast Discussion
Issued by NWS Wilmington, NC

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000 FXUS62 KILM 201925 AFDILM Area Forecast Discussion National Weather Service Wilmington NC 325 PM EDT Sun Aug 20 2017 .SYNOPSIS...
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A weak front will slowly dissipate across the area through tonight. Moisture from a trough to our south will make its way on shore over the southeast coast through Monday. High pressure will expand across the area from the western Atlantic Monday thru Wednesday, continuing the heat and high humidity. A cold front will move across the Eastern Carolinas from the northwest late Wednesday night into Thursday. Canadian high pressure will build down behind front bringing drier weather for the weekend.
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&& .NEAR TERM /THROUGH MONDAY/...
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As of 230 PM Sunday...Cumulus field has expanded with some enhancement, especially along the sea breeze front. Generally a 20- 30% POP should suffice along the coastal areas with isolated chances farther inland. Lowered POPs this evening with the loss of heating however fog/stratus are expected to develop and increase in coverage overnight. GFS/NAM diverge with moisture profiles during Monday and specifically during the eclipse with the NAM probably too agressive with deeper moisture return during the day. Expect to see the most clouds along SC coastal areas with partly to mostly cloudy skies, and partly cloudy skies elsewhere once the stratus/fog dissipates. Focused highest POPs across the southern areas as well during tomorrow (30-35%) with slight chance to low chance POPs across remaining areas. Lows are expected to range from the lower 70s inland to the mid 70s at the coast. As a result of the disparity in the cloud cover during Monday favor a blend toward the warmer/less cloudy GFS MAV high temperatures. Latest ETSS for downtown Wilmington has predicted levels right at minor coastal flood thresholds with high tide this evening. In the absence of heavy rainfall and a fetch that would push levels above criteria will hold off on a Coastal Flood Advisory at this time. Subsequent high tides with during the next couple evenings should exceed thresholds as a result of the new moon.
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&& .SHORT TERM /MONDAY NIGHT THROUGH TUESDAY NIGHT/...
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As of 300 PM Sunday...Ridging aloft to the west will combine with Atlantic ridge, to produce center of ridge aligning right over the southeast Mon night through Tues. This will allow for increased subsidence and dry air aloft which should limit convection, but shallow tropical moisture will continue to be present in a S-SE low level wind flow. Essentially, a tropical airmass will be present with pcp water values up near 1.75 to 2 inches. Overall expect localized cu and convective development mainly along sea breeze pushing inland through the afternoon and some convection mainly off shore overnight. The NAM and GFS were both trying to show a piece of energy rotating around the ridge from the south possibly producing some clouds or slight chc of shwrs toward daybreak Wed, but overall not expecting much coverage through the period. Temps will be on the warm side with 90 to 95 most places during the day and in 70s at night.
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&& .LONG TERM /WEDNESDAY THROUGH SUNDAY/...
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As of 3 PM Sunday...Primary feature influencing extended forecasts is cold frontal passage late Wednesday and early Thursday. This is supported by GFS/ECMWF upper patterns, both of which also migrate Canadian High pressure into the region Friday through the weekend, imparting a slightly drier and cooler feel than late. GOES-16 shows the circulation near 20N north of Puerto Rico, which may fester off the FL coast near a stalled boundary early next week, potentially deepening. Regardless of intensity, the expectation is this feature will lift to the north slowly, remaining offshore of our coast. A few strong storms are possible late Wednesday as wind shear aloft and low- level convergence increase as the upper trough edges in. Wednesday may very well be the warmest day of the extended period, prior to Canadian high pressure intrusion.
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&& .AVIATION /18Z SUNDAY THROUGH FRIDAY/...
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As of 18Z...Best chances (albeit low) are at the coastal terminals through the afternoon as they are tied to the sea breeze front. Can`t entirely rule out and isolated -SHRA/TSRA at KFLO or KLBT either but for now will focus VCTS as the coastal terminals. Diurnal cumulus field will wane with the loss of heating. MVFR/IFR CIGs and VSBYs are possible overnight into the early morning hours as stratus/fog development occurs. Confidence is highest at the inland terminals with moderate confidence at the coastal terminals. Convective trends will be somewhat similar tomorrow compared to today however the higher convective chances will be at KCRE and KMYR. Extended Outlook...Increasing coverage of showers/tstms by Tue through Wed. Flight restrictions will also be possible each early morning due to stratus/fog Wed.
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&& .MARINE...
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NEAR TERM /THROUGH MONDAY/... As of 230 PM Sunday...Light onshore flow prevails in a weak pressure gradient so far this afternoon. The flow is expected to veer to a southerly direction later in the day and southwest this evening. A weak surge may briefly build down the coast early Monday morning, then quickly veer to the southeast and south during the day as the sea breeze takes hold and the old front washes out. Seas will average 2-3 ft through the period. Widely scattered showers and tstms are possible late tonight, and they could get closer to the Long Bay inshore waters during the morning before the diurnal shift occurs. SHORT TERM /MONDAY NIGHT THROUGH TUESDAY NIGHT/... As of 300 PM Sunday...Atlantic high pressure will produce a southerly flow through the period. As it builds in, it will veer around from SE to S. A trough will move east Tues night into early Wed helping to push winds around to the S-SW and increase slightly. Overall winds will be 10 kts or less through early Tues with an increase up to 10 to 15 kts late Tues into Tues night. Seas around 2 ft Mon through early Tue will increase to 2 to 4 ft late Tue into Tue night. A longer period swell up to 10 seconds will mix in with wind waves Tues through Tues night. LONG TERM /WEDNESDAY THROUGH FRIDAY/... As of 300 PM Sunday...The extended marine period will become a bit bumpy ahead of a cold front Wednesday, as SW winds gust to 20 KT and higher Wednesday afternoon. A wind shift will migrate across the 0- 20 NM waters early Thursday. Strong Canadian high pressure will interact with the front offshore to produce NE winds 15-20 KT Thursday into Friday. As a result, `Caution` and even `Advisory` headlines are possible this period. Seas of 3-5 feet can be expected Wednesday afternoon through much of Friday before subsiding, and up to 6 feet well offshore. A few storms may be strong Wednesday night through Thursday as a cold front crosses the waters and radar updates are encouraged.
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&& .ILM WATCHES/WARNINGS/ADVISORIES... SC...None. NC...None. MARINE...None. && $$ NEAR TERM...SRP SHORT TERM...RGZ LONG TERM...MJC AVIATION...SRP

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