Area Forecast Discussion
Issued by NWS Charleston, SC

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000 FXUS62 KCHS 220149 AFDCHS Area Forecast Discussion National Weather Service Charleston SC 949 PM EDT Thu Sep 21 2017 .SYNOPSIS... High pressure will prevail through this weekend. The high will weaken and shift inland as Hurricane Maria tracks northward off the Southeast U.S. coast through the first half of next week. && .NEAR TERM /UNTIL 6 AM FRIDAY MORNING/...
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Instability is slowly waning with the loss of insolation. Could see an isolated shower/tstm across the far interior through midnight, so kept a 20% pop in this area with dry conditions elsewhere. There will be a risk for shallow ground fog early Friday as debris cloudiness thins, the boundary layer decouples and low-level moisture pools, but do not anticipate any meaningful impacts. Did nudge overnight lows down a few degrees inland where rain activity earlier cooled things off a bit more than expected. Lows will range from the upper 60s inland to the mid 70s at the beaches.
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&& .SHORT TERM /6 AM FRIDAY MORNING THROUGH SUNDAY/... A weak upper trough pattern and lingering low-level moisture on Friday will support isolated showers/tstms mainly in the afternoon associated with the sea breeze. As dry high pressure steadily builds down the east coast, the best rain chances on Saturday will be across southeast GA where better moisture resides. By Sunday all areas should be too dry to support precipitation. Above normal temps expected with highs in the mid to upper 80s. && .LONG TERM /SUNDAY NIGHT THROUGH THURSDAY/... Inland high pressure will persist through early next week while confidence is increasing that Hurricane Maria will remain offshore of the Southeast U.S. coast as it tracks north through the middle of next week. Some showers could skirt coastal areas early next week as Maria passes by but otherwise mainly dry conditions are anticipated. Temperatures look to stay above normal. && .AVIATION /02Z FRIDAY THROUGH TUESDAY/... Primary concern: * Fog Scattered showers/tstms should remain west of the terminals before dissipating. Shallow ground fog likely again early Friday as skies clear, winds go calm and low-level moisture pools. Given the shallow nature of the fog, vsbys could be high variable. Will carry MIFG at both sites roughly 08-09z through daybreak, but keep conditions above MVFR thresholds for now. This will be reevaluated for the 06z TAF cycle. Extended Aviation Outlook: Low probability for brief flight restrictions in early morning fog and/or low clouds Saturday morning and in mainly afternoon showers/thunderstorms Friday at KCHS/KSAV and at KSAV Saturday. && .MARINE...
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Issued a Small Craft Advisory for Hazardous Seas for the Georgia offshore waters beginning 18z Friday. This Evening and Tonight: Fairly tranquil conditions are expected within weak sfc high pressure over the coastal waters. In general south/southeast near 10 kt will become east 5 kt later tonight. Seas will range between 1-2 ft nearshore and 2-3 ft in offshore Georgia waters early, but will slowly build up to 3-4 ft mainly in a long period swell after midnight. Friday through Monday: The main issue will be building swells associated with offshore Hurricane Maria. Some 6 ft seas are expected to push into outer GA waters by late Fri afternoon and the nearshore waters by Sat morning. A prolonged period of Small Craft Advisories are expected. Rip Currents: Swell from offshore Hurricane Maria will slowly build at the beaches. This results in a Moderate Risk of rip currents through Friday and will likely maintain an elevated risk through early to mid next week.
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&& .TIDES/COASTAL FLOODING...
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Powerful surf created by offshore Hurricane Maria will drive significant wave run-up, which could cause further beach erosion this weekend into early next week. Also, the potential for shallow salt water flooding will persist through early next week around the times of high tide, particularly along the South Carolina coast.
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&& .CHS WATCHES/WARNINGS/ADVISORIES...
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GA...None. SC...None. MARINE...Small Craft Advisory for hazardous seas from 2 PM Friday to 6 AM EDT Wednesday for AMZ374.
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&& $$

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