textproduct: Charleston

WHAT HAS CHANGED

Former Key Message 2 has been removed as the High Rip Current Risk has expired, and the aviation section has been updated.

KEY MESSAGES

- 1) Below normal temperatures this week as high pressure prevails and a powerful nor'easter meanders off the Mid- Atlantic coast.

- 2) The highest astronomical tides of 2026, combined with near gale force northeast winds, will bring a multi-day coastal flooding threat to SE GA and SC Lowcountry this weekend, with elevated water levels lingering through most of next week.

DISCUSSION

KEY MESSAGE 1: Below normal temperatures this week as high pressure prevails and a powerful nor'easter meanders off the Mid-Atlantic coast.

Surface dewpoints have mixed to around 40 degrees across the forecast area this afternoon. The clear and dry conditions will remain across the forecast area through early this evening. During the mid to late evening, thin mid and high clouds sourced from over the southern Appalachians will drift over the SC Lowcountry later this evening through the overnight hours. The sky across SE GA should remain mostly clear. Given thin cloud cover, light winds, and dry conditions, low temperatures should favor the cooler MOS solutions. Min temperatures are forecast to range from the mid 40s inland to the 50s across the beaches.

Wednesday through Thursday: A nor'easter will be positioned well off the coast of the Mid-Atlantic states Wednesday morning. It will slowly meander slightly further away from the Mid-Atlantic states into Thursday evening. Across the southeastern states high pressure will hold strong both days, centered over the Great Lakes. The prevailing high pressure will yield dry and sunny conditions over the local forecast area with high temperatures in the 70s. Overnight both Wednesday and Thursday nights winds are forecast to go light to calm, resulting in prime radiational cooling conditions. Lows both nights will be several degrees below normal, with lows bottoming out in the mid 40s inland and low 50s along the beaches.

Friday through Monday: With the nor'easter drifting further away from the Mid-Atlantic states, high pressure will begin to build in stronger over the Mid-Atlantic states. Along with the building high pressure, a coastal trough is forecast to develop along the Southeastern coastline. This will yield gusty NE winds across the forecast area, especially along the coast. The advection of cooler air resulting from the NE flow will keep temperatures below normal through the weekend and into early next week.

KEY MESSAGE 2: The highest astronomical tides of 2026, combined with near gale force northeast winds, will bring a multi-day coastal flooding threat to SE GA and SC Lowcountry this weekend, with elevated water levels lingering through most of next week.

Tidal departures will begin to increase as northeast winds strengthen along the coast on Saturday. Minor to moderate coastal flooding is possible for Charleston and coastal Colleton counties Saturday evening. Winds are forecast to strengthen to near gale force on Sunday. Moderate to major coastal flooding is possible for Charleston and Colleton counties, with moderate coastal flooding possible along the southern SC and GA coastlines.

The Perigean spring or King Tides will begin this weekend and continue into early next week, the highest astronomical tides of the year will occur Tuesday and Wednesday mornings. In fact, the morning high in the Charleston Harbor will see astronomical high tide values near 6.9 ft MLLW, just 0.1 ft below flood stage. Ongoing gusty northeast winds and elevated tidal departures may lead to coastal flooding for much of next week, most likely during the morning high tide cycle. Fortunately, no measurable rainfall is expected this weekend into early next week.

AVIATION /00Z WEDNESDAY THROUGH SUNDAY/

No aviation concerns as northerly winds weaken tonight, with 5 to 10 knot north-northeasterly winds expected for Wednesday.

Extended Aviation Outlook: Gusty NE winds upwards of 25 knots are forecast on Saturday.

MARINE

Through Tonight: The marine zones will remain between a ridge of high pressure along the Appalachians and a nor'easter off the Mid- Atlantic coast. The pressure pattern is forecast to support northeast winds between 15-20 kts with gusts around 25 kts across the nearshore and outer waters. Gusty winds should keep seas elevated between 4 to 7 ft across the nearshore and up to 8 across portions of the outer GA waters. Small Craft Advisories will continue for all marine zones outside the CHS Harbor tonight.

Wednesday and Thursday: A nor'easter will be located well off the Mid-Atlantic coast through Thursday, while high pressure centered over the Great Lakes will dominate over the East Coast land zones. The interaction between these two synoptic features will yield gusty NNE winds Wednesday morning, before the nor'easter meanders further away and impacts lessen. Small Craft Advisories will remain in effect for all nearshore waters through Wednesday evening. The Small Craft Advisory for the 20 to 60 nm offshore GA waters is forecast to remain in effect through the weekend and lingering 6+ ft seas are expected.

Friday and Saturday: Friday and Saturday: High pressure will strengthen over the Mid-Atlantic States while a coastal trough develops along the Southeast U.S. coast. The interaction between these two features will cause marine conditions to rapidly deteriorate. Winds and seas will increase, with Small Craft Advisories likely, and Gale Watches/Warnings possible for all of our coastal waters, including the Charleston Harbor.

CHS WATCHES/WARNINGS/ADVISORIES

GA...None. SC...None. MARINE...Small Craft Advisory until 9 PM EDT Wednesday for AMZ360-362- 364. Small Craft Advisory until 8 AM EDT Sunday for AMZ384.