textproduct: Charleston

WHAT HAS CHANGED

Minor updates made to Key Message 1 and the Marine Section for trends tonight. The Aviation Section has been updated for the 00Z TAF issuance.

KEY MESSAGES

- 1) The typical summertime pattern will continue this weekend into next week. The threat for isolated strong to severe thunderstorms and localized heavy rainfall will exist each day.

- 2) Hot and humid conditions will return next week.

- 3) Minor coastal flooding possible along the South Carolina coast with evening high tide cycles next week.

DISCUSSION

KEY MESSAGE 1: The typical summertime pattern will continue this weekend into next week. The threat for isolated strong to severe thunderstorms and localized heavy rainfall will exist each day.

High pressure will gradually build back into the area from the east overnight leading to a transition back towards a more standard summertime pattern. Tomorrow may be the one day where things could remain a little drier than normal as trends in guidance have supported less development along the afternoon seabreeze than previous runs. Like most days, the seabreeze will be the driving factor for storms as it pushes inland with the diurnal heating of the land areas. Some shortwave ridging will likely be in place tomorrow in the wake of the system going through today likely leading to some subsidence across our area. This subsidence or sinking motion will likely limit what the seabreeze will be able to cook up during the afternoon and with that we have lowered the rain chances to more isolated to low end scattered.

By the early to middle parts of next week, storm chances should return to a more normal pattern with more scattered showers and thunderstorms each afternoon. With area wide PWATS remaining in the 2 inch range, any storms that do develop will be possible of locally heavy rainfall. Couple this with some inverted V soundings by the middle part of the week and a couple strong to severe storms especially Tuesday through Thursday.

KEY MESSAGE 2: Hot and humid conditions will return next week.

Heat and humidity is expected to return next week, especially mid to late week. Highs are forecast to peak in the mid 90s, with heat indices of 100+. Areas east of I-95 and closer to the coast will see the highest heat indices, generally averaging in the 105-110F range. Heat Advisories could be required. Overnight lows will also be seasonally warm in these locations, only falling to the upper 70s. NWS HeatRisk currently shows a Major (level 3/4) HeatRisk, especially Tuesday through late week, so regardless of heat product issuance, these conditions will bring a risk of heat-related impacts, especially to those more vulnerable to heat or those without adequate cooling/hydration.

KEY MESSAGE 3: Minor coastal flooding possible along the South Carolina coast with evening high tide cycles next week.

Elevated tide cycles are expected next week due to the upcoming perigee and new moon. Base astronomical levels in the Charleston Harbor with the evening high tides Monday through Thursday will be in the 6.4-6.6 ft MLLW range, so it will not take much to approach minor coastal flood thresholds (7.0 ft MLLW). However, south- southwest flow should keep departures low, limiting the overall coastal flood threat. This also jives with some of the latest probabilistic guidance.

AVIATION /00Z SUNDAY THROUGH THURSDAY/

VFR conditions are anticipated to prevail at CHS/JZI/SAV through 00Z Monday. However, there is a low risk for patchy fog to develop near the SAV terminal late tonight/around daybreak Sunday and a few showers that could impact any terminal briefly early Sunday afternoon. Confidence is too low to include TEMPO or PROB30 groups at any terminal for the latest TAF issuance.

Extended Aviation Outlook: Brief flight restrictions are possible in afternoon showers/thunderstorms.

MARINE

Tonight into Sunday Morning: Scattered showers and storms will likely develop across the nearshore waters during the early morning hours with the development of the overnight land breeze. Conditions will once again be favorable for the development of waterspouts across the nearshore and offshore waters of Southeast South Carolina and Southeast Georgia, including the Charleston Harbor. The waterspout risk will be highest near lines of towering clouds and in the vicinity of showers and thunderstorms. Conditions will become less favorable for waterspout development by late this morning as the sea breeze begins to form along the beaches.

Sunday through Thursday: The coastal waters will largely remain in between Atlantic high pressure and a trough of low pressure inland. This set-up favors south to southwest winds through the period. Winds speeds and seas are forecast to stay below Small Craft Advisory criteria.

CHS WATCHES/WARNINGS/ADVISORIES

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