textproduct: Charleston

WHAT HAS CHANGED

All sections have been updated

KEY MESSAGES

- 1) Scattered showers and thunderstorms could impact portions of southeast South Carolina and southeast Georgia today. Rain Chances continue through the remainder of the week along the coast.

- 2) Coastal flooding is expected at least through the middle of the week, especially along portions of the southeast South Carolina coast.

- 3) There is a High Risk of rip currents along the entire coastline Tuesday and Wednesday.

DISCUSSION

KEY MESSAGE 1: Scattered showers and thunderstorms could impact portions of southeast South Carolina and southeast Georgia today. Rain Chances continue through the remainder of the week along the coast.

Upper ridging will begin to build over the central US as our northeast upper trough lifts out into the North Atlantic. With surface high pressure to our north and weak sfc troughing across the marine waters; east-northeasterly surface flow should prevail throughout the forecast. Scattered to possibly numerous showers and thunderstorms have developed across the marine waters and are progressing inland with the movement of a pseudo seabreeze/sfc convergence zone. Drier air is expected to slowly push into the area from the north-northwest this afternoon and evening as PWATS should fall to around 1.5 inches across interior SC. There will be some potential for locally heavy rainfall, primarily along the coast from around Beaufort County south to the Altamaha. The overall flood risk is relatively low but it is possible a few locations could pick up 1- 2 inches of rain. If this locally heavy rain were to occur around the time of the late afternoon high tide (~5:45 pm) the flood risk could be slightly enhanced along the coast. Temperatures should remain on the cooler side through the first half of the week given increased cloud cover and northeasterly flow across the area.

With little change in the synoptic pattern through most of this week, scattered showers and thunderstorms will be possible each afternoon mainly along the coast.

KEY MESSAGE 2: Coastal flooding is expected at least through the middle of the week, especially along portions of the southeast South Carolina coast.

Astronomical tide levels will continue to rise through the middle of the week thanks to the recent lunar perigee (9/6) and the upcoming new moon (9/11). These factors will push astronomical tides as high as 6.55 ft MLLW at Charleston Wednesday evening, setting the stage for coastal flooding potential with each evening high tide cycle. Northeast flow will strengthen along the coast today and persist into Tuesday night which is expected to drive increasing tidal departures. The first round of coastal flooding is expected to occur with the upcoming late afternoon high tide at Charleston (~5:45 pm) and we are currently forecasting a peak tide value of 7.4 ft MLLW. The potential for moderate coastal flooding (7.5ft MLLW or higher) will increase with the Tuesday and Wednesday evening high tides as tidal departures likely build within the persistent northeast flow. Current forecasts are for Moderate coastal flooding at Charleston on Tuesday (7.5ft MLLW). Coastal Flood Advisories are in effect and will certainly be needed for Charleston and coastal Colleton counties with each late afternoon and early evening high tide cycle through at least Wednesday.

For the rest of the coast from Beaufort County south including the southeast GA coast, tidal departures would need to exceed 1 ft to reach the minor coastal flood threshold (9.5 ft MLLW) at Fort Pulaski. Therefore, coastal flooding is less likely along this part of the coast but can't be ruled out especially with the late afternoon and early evening high tide cycle on Tuesday and Wednesday.

KEY MESSAGE 3: There is a High Risk of rip currents along the entire coastline Tuesday and Wednesday.

Persistent and gusty NE winds and building seas will support a High Risk of rip currents at all beaches along the southeast SC and southeast GA coast Tuesday and Wednesday. An enhanced risk of rip currents will likely last through the end of the week.

AVIATION /18Z MONDAY THROUGH SATURDAY/

Mostly VFR conditions are prevailing across all area TAF sites with scattered showers and an isolated storm occurring mainly east of I-95 this afternoon. Showers and storms should spread inland across southern SC into eastern GA later this afternoon; however, overall impacts to aviation are expected to be minimal. Northeast winds have increased this afternoon and gusts up to around 20 knots will be possible through the remainder of the afternoon. Showers should relax by the early evening with mainly VFR conditions prevailing overnight. Winds will also relax; however, should remain out of the northeast through tomorrow morning.

Extended Aviation Outlook: Scattered thunderstorms could impact the terminals again on Tuesday. Northeast winds will be breezy on Tuesday as well.

MARINE

Through Tonight: Northeast flow will dominate across the marine waters today, with gusts as high as 25 knots across the nearshore SC waters and the Charleston Harbor. A Small Craft Advisory remains in effect for these waters. The SCA in the Charleston Harbor will expire at 02Z this evening, however gusts will likely remain elevated (around 15 to 20 knots) through the overnight period.

Tuesday through Friday: Northeast flow across the local waters is expected to surge a bit on Tuesday with gusts to 25 knots becoming more frequent across all the nearshore waters and the Charleston Harbor. The Small Craft Advisories for the SC nearshore waters will remain valid through 06Z Wednesday. Another Small Craft Advisory may be required for the Charleston Harbor Tuesday afternoon. The gradient will begin to weaken and diminish Tuesday night through Wednesday. For Thursday and Friday we expect to see a return to southwest flow.

CHS WATCHES/WARNINGS/ADVISORIES

GA...High Risk for Rip Currents from Tuesday morning through Tuesday evening for GAZ217-219-239-241. SC...High Risk for Rip Currents from Tuesday morning through Tuesday evening for SCZ148>151. Coastal Flood Advisory until 8 PM EDT this evening for SCZ149- 150. MARINE...Small Craft Advisory until 10 PM EDT this evening for AMZ340. Small Craft Advisory until 2 AM EDT Wednesday for AMZ360-362.