468 FXUS62 KCHS 061127 AFDCHSArea Forecast Discussion National Weather Service Charleston SC 727 AM EDT Mon Oct 6 2025
.SYNOPSIS... High pressure ridges in from the north through Wednesday. A strong backdoor cold front will cross the area later Wednesday into Thursday, with inland ridging persisting into the weekend as low pressure potentially passes off the Southeast coast.
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.NEAR TERM /THROUGH TONIGHT/... Today: Aloft, mid-upper lvl ridging will persist across the Mid-Atlantic states while h5 vort energy shifts north across the Deep South and potentially into the Southeast along its southwestern edge. At the sfc, an inverted trough should persist off the SC/GA coast for much of the day along the southern periphery of high pressure extending from the western Atlantic into the Mid-Atlantic states, and appearing to hold just inland of the local area. Much like the previous morning, coastal showers will be driven onshore within an easterly wind, producing light to moderate rains across the South Carolina and Georgia coastal corridor, before becoming more focused across Southeast Georgia late morning into early afternoon as h5 vort energy traverses aloft. Weak isentropic lift and PWATS in the 1.7 to 1.9 inch range should support few to scattered showers, even well inland as sfc temps warm into the low- mid 80s early afternoon. Although the progression of precip activity is somewhat quick and less supportive for flooding/flash flooding, sufficient instability remains along the beaches to support a thunderstorm capable of a brief downpour late morning/early afternoon (south of Beaufort, SC into Southeast Georgia). Rainfall accumulations around 1/2 inch are possible in some spots, although could be upwards to an inch if a thunderstorm is able to develop and shift onshore across coastal Southeast Georgia. Breezy easterly should also develop along the coastal corridor early afternoon, generally gusting to around 20 mph.
Tonight: The bulk of guidance indicates deepest moisture shifting inland and h5 vort energy departing to the north by nightfall, suggesting any lingering showers to wane/dissipate rather quickly by sunset. We could see additional showers develop across coastal waters overnight as an inverted trough lingers, and some of this activity has the potential of shifting onshore late night/early morning to a lessor extent than previous nights with signs of the inverted trough attempting to weaken and/or shift onshore late. East- northeast winds should become rather light after midnight. Low temps should range in the mid 60s inland to low 70s closer to the coast.
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.SHORT TERM /TUESDAY THROUGH THURSDAY/... Broad upper ridging extending across the South persists Tuesday into Wednesday. Then, later Wednesday, H5 heights begin to fall as a southern stream shortwave digs toward the Southeast. At the surface, Tuesday and Wednesday remain mostly dry as the surface ridge axis moves overhead. By Wednesday night, a backdoor cold front associated with strong high pressure building over the Northeast approaches the area, with enough moisture in place to justify chance POPs overspreading the area from north to south Wednesday night into Thursday. QPF will be limited, and periods of light rainfall may end up being mixed with drizzle as the shallow ridging undercuts the ample low level moisture already in place.
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.LONG TERM /THURSDAY NIGHT THROUGH SUNDAY/... The forecast for Friday into the weekend is beginning to come into better focus as strong inland ridging persists, with troughing and/or a closed low developing off the Southeast coast. NE winds are likely to persist through at least Saturday, with wind strength being largely predicated on the characteristics of the offshore low. A strong low passing nearby off the coast could bring strong winds, and there is ~10% chance or less that advisory level winds occur along the beaches. Additionally, there will likely be extensive precipitation over the Atlantic, but the amount of that precip that makes it back to land is uncertain given the very dry air inland, and a mainly dry weekend forecast is in place for most of the area at this time.
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.AVIATION /12Z MONDAY THROUGH FRIDAY/... TEMPO MVFR conditions are possible between 12-14Z at CHS/JZI and TEMPO MVFR/IFR conditions are possible between 12-14Z at SAV for showers shifting onshore early morning. VCSH remain at all terminals into late morning and possibly into early afternoon at SAV, which could result in additional brief periods of flight restrictions, but confidence is too low to include in the 12Z TAF issuance. Another breezy day is anticipated with easterly winds gusting upwards to 15-20 kt at all terminals. VFR conditions are then expected to prevail this afternoon, then persist through 12Z Tuesday.
Extended Aviation Forecast: VFR conditions expected to prevail. Be alert to the potential for Gusty NE to develop behind a backdoor cold front Thursday.
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.MARINE... High pressure will remain centered north of the region while an inverted trough remains offshore, leading to an easterly flow across local waters along with gusty showers (potentially thunderstorms). A somewhat enhanced pressure gradient between these features should start to weaken during the day, but still supports wind gusts upwards to the 15-20 kt range. Seas will be the main concern, generally ranging between 4-6 ft nearshore and 6-8 ft across outer Georgia waters. Small Craft Advisories will therefore remain in place for all local waters outside the Charleston Harbor today and tonight, but conditions will be improving overnight and it is anticipated that a portion of nearshore waters will see conditions drop below Small Craft Advisory levels after midnight.
Seas will finally fall below hazardous levels Tuesday and Wednesday, allowing Small Craft Advisories to come down. Then, a backdoor cold front will cross the waters late Wednesday into Thursday morning, bringing strong NE winds and a return of hazardous conditions. Gale force winds are possible late in the week and into the weekend, depending on the development of low pressure that will pass well offshore.
Rip Currents: A high risk of rip currents will continue through today in primarily medium period E to NE swells. The risk for enhanced rips will continue into Tuesday as well.
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.TIDES/COASTAL FLOODING... This Morning: Latest tide observations and guidance support minor/moderate coastal flooding for Charleston and Coastal Colleton Counties, near 7.5 ft MLLW with the morning high tide around 7:35 AM at Charleston Harbor. A Coastal Flood Advisory is now in effect from 5 AM to 10 AM this morning. At Fort Pulaski, recent observations suggest tidal departures not as large as the previous high tide cycle, which could limit the potential for coastal flooding along Beaufort, SC and south across Southeast Georgia coastal communities. Tide levels could fall just short of minor coastal flooding levels. Trends will need to be monitored during the next few hours to determine if the Coastal Flood Advisory needs to be extended south along the coast.
Astronomical tides will continue to increase this week due to the upcoming full moon (Oct 7) and perigee (Oct 8). Additionally, tidal departure values will only slowly decrease through midweek, before increasing again Thursday into the weekend as strong NE winds return. As a result, the threat for mainly minor to moderate coastal flooding with each high tide cycles continues through mid-week. Then, late week, the threat for major coastal flooding arrives with the late morning high tides.
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.CHS WATCHES/WARNINGS/ADVISORIES... GA...Coastal Flood Advisory until 10 AM EDT this morning for GAZ117- 119-139-141. High Risk for Rip Currents through this evening for GAZ117-119-139- 141. SC...Coastal Flood Advisory until 10 AM EDT this morning for SCZ048>051. High Risk for Rip Currents through this evening for SCZ048>051. MARINE...Small Craft Advisory until 2 AM EDT Tuesday for AMZ350-352. Small Craft Advisory until 11 AM EDT Tuesday for AMZ354. Small Craft Advisory until 6 AM EDT Wednesday for AMZ374.
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NEAR TERM...DPB SHORT TERM...CEB LONG TERM...CEB AVIATION...CEB/DPB MARINE...CEB/DPB
NWS CHS Office Area Forecast Discussion