textproduct: Charleston

WHAT HAS CHANGED

All sections have been updated.

KEY MESSAGES

- 1) Locally dense fog will be possible across inland areas this morning.

- 2) Scattered showers and thunderstorms will continue to impact portions of southeast Georgia and southeast South Carolina each day through the upcoming weekend.

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

DISCUSSION

KEY MESSAGE 1: Locally dense fog will be possible across inland areas this morning.

Light to calm winds and ample low-level moisture should allow for fog development this morning. The best chance of locally dense fog will be generally inland of I-95, especially interior southeast GA including Screven, Effingham, Jenkins, Bulloch, Candler, Evans, Tattnall, and inland portions of Bryan/Liberty/Long. In this area, the 10/00z HREF suggests 30-50% probabilities of visibility less than 0.5 miles. Dense Fog Advisories could eventually be needed.

KEY MESSAGE 2: Scattered showers and thunderstorms will continue to impact portions of southeast Georgia and southeast South Carolina each day through the upcoming weekend.

Today: Early this morning, surface analysis shows the coastal trough is still hanging on just off the coast. This is driving scattered shower development over the coastal waters that is trying to push onshore along the Charleston County coast. The setup will change from the past few days as the surface high drifts further out over the subtropical Atlantic, washing out the coastal trough. The forecast area will then sit under the western periphery of the subtropical high in a very typical summertime setup. We then expect to see a progressive diurnal sea breeze with convection initiating along it in the early afternoon. Coverage should be scattered and steadily push inland through the mid to late afternoon hours. Overall, the near storm environment isn't particularly noteworthy with weak flow through the column and MLCAPE values in the 1,500- 2,000 J/kg range. Model soundings do show DCAPE values upwards of 1,000 J/kg which could support an isolated damaging wind threat. Also, precipitable water values will be in excess of 2 inches and with storm motion no more than 10 knots, there could be some locally heavy rainfall. Showers and thunderstorms should come to an end through the evening with the loss of surface heating.

Friday through Sunday: As upper-lvl shortwave energy traverses through the Southeast, southerly flow will continue to transport rich moisture into the region on Friday through the weekend. Expect PWATs to reach above 2.0 inches and support efficient rainfall rates through the weekend. This pattern will yield scattered showers and thunderstorms each day, especially during the afternoon and evening hours. With abundant moisture combined with weak steering flow, thunderstorms will be capable of producing very heavy rainfall over short periods, and slow- moving cells could lead to localized flooding where storms repeatedly affect the same areas. Friday should feature scattered afternoon storms, with Saturday seeing greater coverage, while Sunday looks similar with another round of mainly afternoon and convection. A widespread severe threat seems unlikely through this period, however afternoon instability (peak SBCAPE values of ~2000-2500 J/kg) could yield frequent lightning and damaging wind gusts within the stronger storms that develop. Overall, the main concern through the weekend will be localized heavy rainfall, leading to minor flooding issues within low-lying and poor drainage areas.

KEY MESSAGE 3: The potential for coastal flooding will persist into Friday, primarily for portions of the southeast South Carolina coast.

Astronomical tide levels have peaked with this previous evening's high tide, but will remain elevated into Friday. This could support minor coastal flooding along the southeast South Carolina coast during the next 1-2 evening high tide cycles given recent positive tidal departures that will be slow to change while winds weaken and turn more southerly. This evening's high tide should see the best chance for reaching above 7.0 FT MLLW in the Charleston Harbor before conditions improve further. A Coastal Flood Advisory could eventually be needed.

AVIATION /12Z THURSDAY THROUGH MONDAY/

The 12z TAF period begins with mostly VFR conditions at and near KCHS, KJZI, and KSAV. There remains some concern for low stratus and/or fog to impact KSAV for a couple of hours this morning. So far, most of the fog and stratus has remained inland of KSAV, but it could still spread in. We have maintained a TEMPO group to account for IFR stratus with MVFR visibility through 13z. The next forecast concern continues to be afternoon thunderstorms. Current thinking is that storms will develop along the sea breeze starting around midday or the early afternoon. At KCHS and KSAV, we have introduced VCTS around 16-17z with a PROB30 group for a few hours through 19-20z to account for thunderstorm impacts. At KJZI, current thinking is that development along the sea breeze will be inland of the terminal and there is no mention of thunderstorm impacts there.

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

MARINE

Today through tonight: Light south winds in the 5-10 knot range will prevail this morning before surging more into the 10-15 knot range this afternoon and evening. Overnight, winds will remain 10-15 knots while turning more out of the southwest. Seas are expected to average 2-3 feet.

Friday through Monday: Generally tranquil marine conditions should continue on Friday through early next week, with winds mostly 5 to 10 kts as high pressure remains the dominant feature across the Atlantic. Southwest winds are expected on Friday, becoming more southerly to southwesterly through the weekend before turning westerly around 5 kts on Monday. The main concern for mariners will be scattered showers and thunderstorms, with the greatest coverage likely Friday afternoon through Saturday and additional storms possible on Sunday and Monday. Any stronger storm could produce frequent lightning, heavy rain with reduced visibility, and brief gusts well above prevailing winds. Seas will range from 2-3 ft through the period.

Rip Currents: Lingering swell and the light onshore flow supports a Moderate Risk for rip currents along all beaches today, before conditions improve to a Low Risk on Friday. Beachgoers should swim near a lifeguard and heed local beach patrol guidance.

CHS WATCHES/WARNINGS/ADVISORIES

GA...None. SC...None. MARINE...None.