textproduct: Charleston

WHAT HAS CHANGED

All sections have been updated.

KEY MESSAGES

- 1) Breezy with isolated afternoon and evening thunderstorms today.

- 2) A fairly typical summertime pattern is expected for the weekend into next week with daily shower and thunderstorm chances. Hot and humid conditions are likely Monday and Tuesday.

DISCUSSION

KEY MESSAGE 1: Breezy with isolated afternoon and evening thunderstorms today.

Regional radar composite has indicated a band of thunderstorms just south of the Altamaha River, with stratiform rain and isolated thunderstorms across SE GA into this afternoon. Corfidi vectors indicate that the convection should remain on a track to the SE, keeping the heaviest convection just south of the CWA. The majority of stratiform rain may slide over the nearshore waters by mid- afternoon. Mid to late afternoon temperatures may peak in the upper 80s across SE GA to around 90 across the SC Lowcountry. SPC mesoanalysis indicates that instability will increase across the forecast area this afternoon, with SBCAPE between 3000-3500 J/kg and MLCAPE around 2000 J/kg. At least isolated showers and thunderstorm should develop during the heat of the afternoon, remaining until around sunset this evening. The 12Z run of the HREF indicates that a cluster of thunderstorms may just west of Lake Marion this evening, then tracking east, possibly passing over portions of Berkeley and Charleston Counties late this evening. This late evening round of convection will likely be triggered by an approaching cold front.

The rest of the night should remain generally dry. Gradually cooling llvl thickness are forecast following the slow moving cold front. Low temperatures are forecast to range from the low 70s inland to the mid 70s along the coast.

KEY MESSAGE 2: A fairly typical summertime pattern is expected for the weekend into next week with daily shower and thunderstorm chances. Hot and humid conditions are likely Monday and Tuesday.

A front in the vicinity on Saturday will eventually wash out, with the region to become positioned between high pressure offshore and an approaching cold front Monday into Tuesday. Aloft, a series of weak disturbances will cross the Southeast, before larger scale troughing possibly settles into the eastern CONUS. Isolated to scattered showers and thunderstorms are possible each day, with coverage peaking in the afternoon and evenings when instability is highest. The threat for organized severe weather is low, but cannot rule out a couple strong to severe storms this time of year, especially early next week.

Hot and humid conditions are expected Monday and Tuesday. High temperatures should peak in the low to mid 90s, with heat indices potentially reaching the 105-110F range, particularly along the coastal counties. NWS HeatRisk also shows a Major Risk (level 3/4) in these locations. We will need to watch the potential for Heat Advisories.

AVIATION /18Z FRIDAY THROUGH WEDNESDAY/

Prior to the 18Z TAFs, KCLX detected the ragged back end of a large area of stratiform rainfall tracking across KSAV. Light rain may push east of the KSAV terminal by 20Z. Otherwise, a period or two of MVFR ceilings will remain possible across the terminals through late this afternoon. Southwest winds are forecast to remain around 10 kts with gusts between 15-20 kts through the rest of the daylight hours. After midnight, a backdoor cold front will approach KCHS and KJZI, possibly bringing another round of restrictive ceilings and winds veering from the northwest. Once the front push south, winds should shift from the northeast and ceilings should improve to VFR.

Extended Aviation Outlook: Brief periods of flight restrictions possible with any showers and thunderstorms.

MARINE

Tonight: Following recent observation trends, the Gale Warning for the SC waters will end at 2 PM. Small Craft Advisories will remain for the CHS Harbor, GA nearshore, and lower SC nearshore until 5 PM. The Outer GA and the Charleston County nearshore through 8 PM. A backdoor cold front is forecast to push south across the waters late tonight, shifting winds from the northwest. Seas will subside through the night, reaching 2 to 3 ft by daybreak Saturday.

Saturday through Wednesday: No marine concerns are expected over the weekend. The coastal waters will become positioned between high pressure centered well offshore and an approaching cold front Monday and Tuesday, leading to increasing winds. Gusts could approach 25 knots at times especially in the afternoons, but looks fairly marginal for Small Craft Advisories at this time. Conditions should stay below advisory levels on Wednesday.

Rip Currents: Swells and gusty winds will lead to a Moderate risk for rip currents at South Carolina beaches Friday.

CHS WATCHES/WARNINGS/ADVISORIES

GA...None. SC...None. MARINE...Small Craft Advisory until 5 PM EDT this afternoon for AMZ340- 362-364. Small Craft Advisory until 8 PM EDT this evening for AMZ360- 384.