textproduct: Charleston

WHAT HAS CHANGED

All sections have been updated.

KEY MESSAGES

- 1) Dry conditions and below normal temperatures will continue through early next week before gradually warming up by the end of the week.

- 2) A significant multi-day coastal flooding event is expected this weekend through at least the middle of next week.

- 3) Strong northeast flow this weekend and into early next week will result in several hazards including gusty lake winds, rip currents, high surf, and beach erosion.

DISCUSSION

KEY MESSAGE 1: Dry conditions and below normal temperatures will continue through early next week before gradually warming up by the end of the week.

Today through Friday: The overall pattern will be rather persistent over the next 7 days or so with upper level ridging over the northern Gulf coast and a rather pesky upper trough/cutoff low meandering around the Bahamas. Surface high pressure has built down through the mid-atlantic with a weak wedge setting up across the Carolinas. Dry and cool conditions will prevail under the wedge through Sunday. The wedge should relax Monday into Tuesday as temperatures slowly climb back towards normal by midweek. By late in the week, the upper ridge should begin to breakdown and translate east across the southeastern US bringing a temporary warming to the area as highs climb back close to 80 degrees by Friday.

KEY MESSAGE 2: A significant multi-day coastal flooding event is expected this weekend through at least the middle of next week.

Astronomical tides will continue to rise through the weekend and into next week due to the upcoming full moon (10/26) and the lunar perigee (10/28). Large tidal departures are already ongoing, and with an extended period of strong northeast flow this weekend and into next week, these departures will increase in magnitude. The combination of the highest astronomical tides of the year and persistent strong northeast flow will result in a multi-day moderate to major coastal flooding event for the entire southeast GA/SC coast.

Upcoming morning high tide (~7 am): Moderate coastal flooding will likely occur at Charleston with the morning high tide cycle. The astronomical high tide is 6.19 ft MLLW and we are currently running a 1.3 ft departure as we head into the preceding low tide. We are expecting winds to increase offshore this morning leading to likely even higher departures occurring. We currently expect high tide to peak in the 7.5-7.6 ft MLLW range, and a Coastal Flood Advisory is in effect for Charleston and coastal Colleton counties. At Fort Pulaski, the astronomical high tide is expected to reach 8.05 ft MLLW and with the same expectations with departures we expect Fort Pulaski to reach 9.6 ft. A Coastal Flood ADvisory is in effect for all of the Georgia Coastline, coastal Beaufort and Coastal Jasper counties in South Carolina.

Over the weekend and into the middle of next week, there is increasing potential for multiple rounds of moderate to major coastal flooding at Charleston and minor to moderate coastal flooding at Fort Pulaski. The highest water levels are expected to occur with the Monday, Tuesday, and Wednesday morning high tide cycles. During these cycles, confidence is increasing that Charleston will exceed major flood stage (8.0 ft MLLW) and Fort Pulaski will exceed moderate flood stage (10.0 ft MLLW). There is even concern that Fort Pulaski could reach or exceed its major flood stage (10.5 ft MLLW), which has never happened in its history (records begin in 1935) outside of a tropical system. Coastal flooding will likely occur with both the morning and evening high cycles for several days, though the evening tide will be the lower of the two. Coastal Flood Advisories will definitely be needed, and Coastal Flood Watches/Warnings are very likely for some or all of the coast from Sunday through Wednesday.

KEY MESSAGE 3: Strong northeast flow this weekend and into early next week will result in several hazards including gusty lake winds, rip currents, high surf, and beach erosion.

Rip Currents: Strong northeast winds and increased wave action will result in dangerous rip currents this weekend. A High Risk of rip currents is in effect for all area beaches both Saturday and Sunday, with an elevated risk persisting through mid-next week.

High Surf/Beach Erosion: Breaking wave heights will increase this morning, reaching 5 to 6 ft or higher along area beaches by late afternoon. High Surf Advisories are in effect for the entire Southeast South Carolina and Southeast Georgia coast into Monday, when breakers should subside below 5 ft. Additionally, the combination of elevated tides, increased wave action, and persistent gusty northeast winds will likely produce beach erosion, with the most significant erosion occurring around high tide cycles this weekend.

Lake Winds: Gusty northeast winds will pick up across Lake Moultrie early this morning and persist through the weekend. Wind gusts up to 25 kt are expected early Saturday morning, mainly between 4 and 9 AM. However, given the early timing and brief duration, we have opted against issuing a Lake Wind Advisory for this morning. Gusts will decrease quickly through late morning as the boundary layer decouples over the relatively cooler lake waters. After sunset this evening, the pattern will flip. Winds will rapidly ramp up as cold air advects over the warmer lake waters, triggering strong vertical mixing and dragging 30 kt gusts down to the surface. A Lake Wind Advisory has been issued for Saturday night into Sunday morning. This diurnal cycle will repeat Sunday, with daytime winds easing before stronger gusts redevelop Sunday night, when an additional Lake Wind Advisory will likely be needed. Furthermore, the combination of steady northeast winds and 2-3 ft waves could yield minor lakeshore erosion along the southwest side of the lake along with some overwash. This includes areas from roughly Pinopolis to Blacks Camp near Cross.

AVIATION /06Z SATURDAY THROUGH WEDNESDAY/

VFR conditions should continue throughout the period with gusty northeasterly winds. Wind gusts up to around 25 knots will be possible throughout the day and potentially persist into the overnight. A few clouds around 3 kft will be possible this morning along the immediate coastline.

Extended Aviation Outlook: Breezy north-northeast winds are expected at KCHS/KJZI/KSAV through the middle of next week, peaking Sunday afternoon with gusts up to 30 kt.

MARINE

Saturday through Monday: High pressure will continue to strengthen across the Mid-Atlantic while low pressure organizes near the Bahamas this weekend. This setup favors a prolonged pinched pressure gradient across the local marine area, with conditions rapidly deteriorating this morning. Gale Warnings are now in effect for all coastal waters outside of Charleston Harbor. Gale-force gusts will persist across both nearshore and offshore legs into Monday, lingering longest over the Georgia outer waters (20-60 nm). Charleston Harbor will see northeast gusts of 25 to 30 kt and waves of 1 to 2 ft through the weekend, and a Small Craft Advisory remains in effect there through Sunday night.

Tuesday through Thursday: Winds and seas will begin a slight downward trend Monday night into Tuesday. However, a prevailing tight gradient between inland high pressure and an offshore low will likely maintain elevated winds and seas through the entire period. Small Craft Advisory level winds and elevated seas are expected to continue across the coastal waters, outside of the Charleston Harbor, through at least the middle of next week.

CHS WATCHES/WARNINGS/ADVISORIES

GA...Coastal Flood Advisory until 9 AM EDT this morning for GAZ217- 219-239-241. High Risk for Rip Currents from 8 AM EDT this morning through this evening for GAZ217-219-239-241. High Surf Advisory from 2 PM this afternoon to 5 PM EDT Monday for GAZ217-219-239-241. SC...Coastal Flood Advisory until 9 AM EDT this morning for SCZ148>151. High Risk for Rip Currents from 8 AM EDT this morning through this evening for SCZ148>151. High Surf Advisory from 2 PM this afternoon to 5 PM EDT Monday for SCZ148>151. Lake Wind Advisory from 9 PM this evening to 11 AM EDT Sunday for SCZ045. MARINE...Small Craft Advisory until 5 AM EDT Monday for AMZ340. Small Craft Advisory until 6 AM EDT early this morning for AMZ360-362-364. Gale Warning from 6 AM this morning to 5 AM EDT Monday for AMZ360-362-364. Gale Warning until 2 PM EDT Monday for AMZ380-382. Gale Warning until 2 AM EDT Tuesday for AMZ384.