textproduct: Charleston

WHAT HAS CHANGED

All sections have been updated.

KEY MESSAGES

- 1) A significant, multi-day coastal flooding event will continue this week.

- 2) Strong northeast flow through early week will result in several hazards including rip currents, high surf, and beach erosion.

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

DISCUSSION

KEY MESSAGE 1: A significant, multi-day coastal flooding event will continue this week.

Astronomical tides will continue to rise into early this week due to the upcoming full moon (10/26) and the lunar perigee (10/28). Large tidal departures are ongoing, and with an extended period of strong northeast flow this weekend and into next week, 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.

This Evening: A Coastal Flood Advisory has been issued for Charleston and Coastal Colleton counties from 6 to 10 PM this evening. Tide levels at the Charleston Harbor are forecast to reach 7.2-7.4 ft MLLW. The current forecast keeps Fort Pulaski just shy of minor flood levels, 9.4 ft MLLW. Therefore, a Coastal Flood Advisory is not planned for the rest of the coastline at this juncture.

Monday Morning: The highest tide level of the event is forecast to occur around 8 AM, with 7.9-8.1 ft MLLW forecast at the Charleston Harbor and 10.0-10.2 ft MLLW at Fort Pulaski. A Coastal Flood Watch is in effect for Charleston and Coastal Colleton Counties, as this tide is forecast to reach major flood levels. Elsewhere along the coast a Coastal Flood Advisory will likely be required, including Tidal Berkeley.

Rest of This Week: Coastal flooding is forecast to occur with the Tuesday, and Wednesday morning high tide cycles, with minor flooding possible through the end of the week. During these cycles, it is possible that the Charleston Harbor could exceed major flood stage. Additionally, Fort Pulaski could exceed moderate flood stage (10.0 ft MLLW). Winds will slightly relax heading into this week, leading to lowering tidal departures. Coastal Flood Advisories will be needed, and Coastal Flood Watches/Warnings are not out of the question for for Charleston and Coastal Colleton counties through Wednesday.

KEY MESSAGE 2: Strong northeast flow through early week will result in several hazards including rip currents, high surf, and beach erosion.

Rip Currents: Strong northeast winds, increasing long-period swell and ongoing wave action will continue to support dangerous rip currents along all SC/GA beaches into early week. A High Risk for rip currents is in place for all beaches this afternoon through Monday, and could persist for all beaches again on Tuesday. An enhanced period of rip currents will continue through the middle of the week.

High Surf/Beach Erosion: Breaking wave heights will slowly increase late afternoon and evening, reaching 4-6 ft along area beaches, likely largest along the GA coast. A High Surf Advisory remains in effect for the entire Southeast SC/GA coast into Monday. Another round of high surf is possible mid-week as the pattern holds (mainly along the GA coast), although appears to fall just short of criteria at this time. Additionally, the combination of elevated tides, wave action and the persistent/gusty northeast winds will likely produce beach erosion for the ongoing high surf event, with the most significant impacts occurring around high tide cycles into Monday.

Lake Winds: Latest observations continue to indicate improvement across Lake Moultrie this afternoon with north-northeast winds gusting upwards to 15-18 kt at times. Although winds are anticipated to remain below Lake Wind Advisory levels as 1000mb geostrophic winds gradually decline for the remainder of the day, some guidance suggests an uptick once again overnight with cold air advection favoring a modest increase in winds across the lake. Lake water temps remain in the upper 60s, which will support low-lvl mixing during evening and overnight hours and a brief uptick in wind gusts (between 20-25 kt) is possible. However, the duration of the event is short-lived if realized, so no headline has been issued for a Lake Wind Advisory at this time.

KEY MESSAGE 3: Dry conditions and below normal temperatures will continue through early next week before gradually warming up by the end of the week.

A rather persistent synoptic pattern persists through the week, with upper level ridging over the northern Gulf Coast and an upper trough lingering around the Bahamas. At the surface, high pressure centered over New England will dominate through mid- week allowing for a wedge to remain in place across the Carolinas. Temperatures through the remainder of the weekend and into early next week should remain below normal with the cooler air trapped within the wedge. The wedge of high pressure will weaken slightly mid-week, with temperatures returning to near normal by the end of the week as a result. The forecast remains rain- free through the week.

AVIATION /19Z SUNDAY THROUGH FRIDAY/

VFR Conditions are expected at CHS/JZI/SAV terminals through 18Z Monday. However, breezy/gusty north-northeast winds (around 25 kt) are expected at all terminals this afternoon.

Extended Aviation Outlook: VFR conditions are expected at CHS/JZI/SAV through late week. Although gusty north-northeast winds (15-20 kt) could occur at all terminals during afternoon hours.

MARINE

This Afternoon through Monday: High pressure across the Mid-Atlantic States and low pressure north of the Bahamas continue to favor a strong pressure gradient across local waters. Although a temporary relax in observed winds has been recorded the last few hours with local waters experiencing a few gusts to gale force near 20 nm and further offshore, guidance supports another round of cold air advection returning this evening, likely resulting in an uptick of sustained north-northeast winds 20-30 kt with frequent gusts to 35- 40 kt off the beaches into early morning hours Monday. Seas should also build to 7-10 ft nearshore and 10-14 ft offshore tonight. Thereafter, the pressure gradient gradually slackens with conditions falling below gale force across nearshore before daybreak Monday, then across offshore SC waters Monday afternoon, followed by offshore GA waters Monday night. A Small Craft Advisory continues in the Charleston Harbor (gusts up to 25-30 kt and seas 1-2 ft) this afternoon, but likely ends prior to daybreak Monday. Conditions could improve sooner than anticipated if stronger cold air advection is not realized overnight.

Tuesday through Friday: Winds/seas will gradually trend lower heading into Tuesday, but a tight gradient between inland high pressure and persistent low pressure centered well offshore will likely maintain elevated winds and seas through late week. Solid Small Craft Advisory level conditions outside the Charleston Harbor, north-northeast wind gusts up to 25-30 kt with seas 5-8 ft nearshore and 8-10 ft offshore (largest across GA waters), will be common through the period. An extended period of Small Craft Advisories will likely be necessary following Gale Warnings early week.

CHS WATCHES/WARNINGS/ADVISORIES

GA...High Risk for Rip Currents through Monday evening for GAZ217-219- 239-241. High Surf Advisory until 5 PM EDT Monday for GAZ217-219-239- 241. SC...High Risk for Rip Currents through Monday evening for SCZ148>151. High Surf Advisory until 5 PM EDT Monday for SCZ148>151. Coastal Flood Advisory until 10 PM EDT this evening for SCZ149- 150. Coastal Flood Watch from late tonight through Monday morning for SCZ149-150. MARINE...Small Craft Advisory until 5 AM EDT Monday for AMZ340. Gale Warning until 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.