textproduct: Charleston

WHAT HAS CHANGED

Coastal Flooding key message updated to reflect the expectation of Moderate coastal flooding for the South Carolina coast this evening.

KEY MESSAGES

- 1) Scattered showers/thunderstorms expected across the area today with isolated/minor flooding possible.

- 2) A Coastal Flood Advisory is in effect for Charleston and Coastal Colleton Counties for moderate coastal flooding with this evening's high tide.

- 3) Hot and humid conditions are expected to return to the area late this week through early next week. Heat Advisories could be needed.

DISCUSSION

KEY MESSAGE 1: Scattered showers/thunderstorms expected across the area today with isolated/minor flooding possible.

A stationary front remains positioned in the vicinity of SE GA this afternoon, with a weak center of low pressure off the southeastern coastline. Convection this afternoon will likely be tied to the sea breeze and enhanced by the stationary front, especially over SE GA. CAMs this morning are not overly impressive in coverage, with generally scattered showers/tstorms forecast. However, the 12Z HREF does have a contour of 30 percent for >3 inches this afternoon across the forecast area. Slow storm motions and plentiful moisture, this morning's KCHS RAOB Sounding had a PWAT of 1.95", could lead to minor flooding of low lying and poor drainage areas. While widespread severe weather is not anticipated, the SPC Mesoanalysis depicts 500-600 J/kg of DCAPE across the forecast area. Therefore, a strong to marginally severe thunderstorm cannot be ruled out.

KEY MESSAGE 2: A Coastal Flood Advisory is in effect for Charleston and Coastal Colleton Counties for minor coastal flooding with this evening's high tide.

While the highest astronomical tides have passed, a 6.46 ft MLLW astro tide this evening in the Charleston Harbor will bring another round of coastal flooding. Weak and variable surface winds will likely keep tidal departures around 1 foot, resulting in total water levels in 7.4-7.6 ft MLLW range. A Coastal Flood Advisory has been issued for Charleston and Coastal Colleton Counties from 8 PM to Midnight tonight, with high tide occurring around 10 PM. At Fort Pulaski, an 8.37 ft MLLW astro tide with similar tidal departures below 1 foot expected, will likely keep total water levels below minor coastal flood criteria.

If heavy rainfall were to occur near or during the time of the evening high tide cycles, flooding concerns would increase as total water levels would similarly increase.

In the absence of strong tidal departures on Thursday, coastal flooding is not anticipated.

KEY MESSAGE 3: Hot and humid conditions are expected to return to the area late this week through early next week. Heat Advisories could be needed.

Temperatures are forecast to ramp back up into the early to mid 90s beginning Thursday and persist into next week. As the subtropical high becomes established, southwest to south low-level flow will bring dewpoints into the mid to upper 70s along the coast. The combination of highs into the 90s and elevated dewpoints will yield widespread heat index values of 100+ degrees across the area. The highest heat indices are expected along the coast where the probability of values in the 105-110 degree range will be highest. Heat Advisories could be needed, perhaps as soon as Friday. The potential for Heat Advisories will then persist through the weekend and into early next week.

AVIATION /01Z THURSDAY THROUGH MONDAY/

Shower and thunderstorm activity in SE GA has pushed south of KSAV, while the SC Lowcountry remains dry this evening. Ridging continues to build in from the north overnight, with VFR conditions prevailing, though periods of favorable radiational cooling for the Lowcountry could result in some patchy, shallow fog before sunrise. Still, impacts not expected at CHS and JZI. Mostly clear skies and light winds Thursday morning, with limited coverage of showers and storms mainly across SE GA expected Thursday afternoon.

Extended Aviation Outlook: Mostly VFR. Low chances of direct impacts from afternoon and evening showers and thunderstorms each day.

MARINE

Tonight through Monday: The subtropical high will start to become more established beginning Thursday which will bring a return to a more typical flow pattern marked by southwest to south flow surging along the land/sea interface with the sea breeze. A period of stronger flow is expected over the weekend and into early next week as the local waters get pinched between the subtropical high and an inland trough. Over the weekend, wind speeds into the 15-20 knot range will become more common with the potential for gusts up to around 25 knots mainly for the SC coast and Charleston Harbor. This could bring the need for some short duration Small Craft Advisories.

CHS WATCHES/WARNINGS/ADVISORIES

GA...None. SC...Coastal Flood Advisory until midnight EDT tonight for SCZ149- 150. MARINE...None.