textproduct: Charleston

WHAT HAS CHANGED

All sections updated.

KEY MESSAGES

- 1)Scattered showers and thunderstorms will continue to impact portions of southeast Georgia and southeast South Carolina daily through the weekend, with localized heavy rainfall possible at times.

- 2) The potential for coastal flooding will persist into Friday, primarily for portions of the southeast South Carolina coast.

- 3) Locally dense fog is possible across inland southeastern GA late tonight and early Thursday morning.

- 4) There is a High Risk of rip currents along the entire coastline today.

DISCUSSION

KEY MESSAGE 1: Scattered showers and thunderstorms will continue to impact portions of southeast Georgia and southeast South Carolina daily through the weekend, with localized heavy rainfall possible at times.

Through Tonight: As surface high pressure over the OBX builds southward into the southeast the flow across the local forecast area will shift more southeasterly. Showers will continue to impact counties generally south of Beaufort as they push inland from the local adjacent Atlantic waters. Showers and storms are forecast to be rather progressive, limiting the heavy rainfall threat. Additionally, while a stronger storm cannot be ruled out this time of year, the overall severe threat appears low.

A more typical summertime pattern takes hold Thursday as subtropical high pressure builds to the east. This will support daily scattered showers and thunderstorms. Convective coverage is expected to peak Friday into Saturday as upper-level shortwave energy traverses the Southeast. Southerly flow will transport deep moisture into the region beginning Thursday, elevating PWATs above 2.0 inches and supporting efficient rainfall rates through the weekend. Instability looks to be modest with daily SBCAPE values peaking around 2200-2500 J/kg. This could support periods of heavy rain at times, especially within thunderstorms, leading to the potential for locally heavy downpours and minor flooding issues.

KEY MESSAGE 2: The potential for coastal flooding will persist into Friday, primarily for portions of the southeast South Carolina coast.

Astronomical tide levels will peak with the upcoming evening high tide cycle, then remain elevated through Friday. Winds across the coastal zones and adjacent Atlantic waters will be ENE this afternoon into the evening. Wind speeds will be less than the past few days, but still strong enough to maintain the large positive tidal departures that have been building for the past few days.

Charleston Harbor: The evening high tide cycle (~7:45 pm) has an astronomical value of 6.55 ft MLLW. We might lose some of the departure with winds diminishing and taking on a more easterly component, but certainly still enough to exceed 7 ft MLLW. A Coastal Flood Advisory is in effect for Charleston and Coastal Colleton Counties with a forecast of 7.3 ft MLLW. Thursday evening will likely bring another round of minor coastal flooding, and potentially even Friday. However, winds will become less favorable.

Fort Pulaski: The peak astronomical tide will come this evening (~7:45 pm) at 8.44 ft MLLW. A tide departure of 1.06 ft would be required to reach the minor coastal flood threshold of 9.5 ft MLLW. Given the departure of 0.88 ft with this morning's high tide, have opted to not issue a Coastal Flood Advisory, with the forecast advertising a value of 9.4 ft MLLW. Thereafter, astronomical tides will decrease along with winds which will likely end the threat of coastal flooding for the week.

KEY MESSAGE 3: Locally dense fog is possible across inland southeastern GA late tonight and early Thursday morning.

This evening winds across southeastern GA are forecast to go light to calm and combined with wet soils from the showers this afternoon will create conditions conducive for fog development. HREF probabilities for visibilities <0.5 mi are generally around 30% across inland southeastern GA along with low condensation pressure deficit values. Fog has been added to the gridded forecast with the most recent forecast update.

KEY MESSAGE 4: There is a High Risk of rip currents along the entire coastline today.

Breezy east-northeasterly winds and an east-southeasterly swell will keep surf conditions dangerous through this evening. The rip current risk will ease to Moderate on Thursday as the swell tapers and winds turn east-southeasterly, before dropping to Low on Friday as conditions further settle.

AVIATION /18Z WEDNESDAY THROUGH MONDAY/

Prevailing VFR at KCHS/KJZI/KSAV through the 18Z TAF period with the exception of some brief MVFR cigs with any showers that impact the terminals. Showers should wane with nightfall. Additional showers streaming in from the adjacent Atlantic waters will be possible tomorrow morning, but confidence was too low to include mention at this time. Additionally, fog is forecast to develop tonight/Thursday morning, especially across southeastern GA. The current suite of guidance keeps the fog inland of the terminals so no mention of MIFG has been included with the 18Z TAFs.

Extended Aviation Outlook: Periodic flight restrictions will be possible each day through the weekend within showers and thunderstorms, mainly during the afternoon hours.

MARINE

Through Tonight: Easterly flow will continue to weaken throughout the day. Expect wind speeds to range from 10-15 kt with gusts up to 20 kt possible, before becoming lighter tonight.

Thursday through Monday: Tranquil marine conditions arrive Thursday and persist through the weekend under light southerly to southwesterly flow. Seas will hold steady at 2 to 3 feet throughout the period.

CHS WATCHES/WARNINGS/ADVISORIES

GA...High Risk for Rip Currents until 8 PM EDT this evening for GAZ217- 219-239-241. SC...High Risk for Rip Currents until 8 PM EDT this evening for SCZ148>151. Coastal Flood Advisory from 6 PM to 10 PM EDT this evening for SCZ149-150. MARINE...None.