Area Forecast Discussion
Issued by NWS Charleston, SC
Issued by NWS Charleston, SC
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550 FXUS62 KCHS 041436 AFDCHS Area Forecast Discussion National Weather Service Charleston SC 1036 AM EDT Thu Jul 4 2024 .SYNOPSIS... A hot and humid air mass will build over the region late week into the weekend. A weak cold front could approach the region by early next week. && .NEAR TERM /THROUGH TONIGHT/... Visible satellite indicated patches of cirrus clouds drifting across the forecast area. In addition, a field of cumulus clouds was expanding across the SC Lowcountry during the late morning hours. The 12Z observed soundings indicated a strong inversion centered at H7 with a convective temperature of 92 degrees. The observed lapse rate between H85-500 was barely over 4 C/km. Recent runs of the HRRR times a weak sea breeze will push inland across SE GA and SC during the afternoon. Dewpoints in the wake of the sea breeze should warm into the mid to upper 70s, possibly developing some weak instability across the coastal counties and along the Altamaha River basin. Isolated showers may occur this afternoon, possibly a lightning strike or two. High temperatures are forecast to range from the mid 90s inland to around 90 along the coast. Tonight: Mid-level High pressure centered over the Lower MS Valley in the evening will continue to weaken into the overnight. Surface troughing will persist over portions of the Southeast U.S., while the periphery of broad High pressure in the western Atlantic will continue to influence our weather. Dry conditions are expected to prevail in the evening and overnight. Expect partly cloudy skies, both low clouds and higher clouds. Temperatures will generally bottom out in the lower to mid 70s across most of our area, and the upper 70s along the immediate coast. && .SHORT TERM /FRIDAY THROUGH SUNDAY/... Mid level ridge will largely persist over the region late week into the weekend, although it will become sandwiched between troughing to the northwest and a closed low over the Atlantic drifting westward towards the Southeast coast. At the surface, high pressure will reside offshore while troughing remains inland. A weak front will approach from the west but should stall out before making it to the local area. Friday should see isolated to scattered showers and thunderstorms in the afternoon and evening. Better coverage is expected over the weekend with higher moisture and weak upper support. Activity could trigger off the sea breeze, as well as the inland trough/front. Rain chances peak 50-60% over inland areas. High temperatures are forecast to reach the mid to upper 90s inland of the immediate coast Friday and Saturday. With elevated dew points, it will feel even hotter. Heat indices could approach or even exceed local heat advisory criteria of 108 degrees, especially on Saturday assuming convection holds off long enough. Sunday should remain below criteria. Highs top out in the lower 90s with heat indices generally 100-105. && .LONG TERM /SUNDAY NIGHT THROUGH WEDNESDAY/... Mid level ridge looks to hold over the Southeast coast through the middle of next week with a broad trough lingering to the northwest and the aforementioned low over the Atlantic weakening. A trough of low pressure should persist over inland areas at the surface. At least scattered showers and thunderstorms are possible each day, with coverage peaking in the afternoon and evenings. Temperatures will be near to slightly above normal. && .AVIATION /14Z THURSDAY THROUGH MONDAY/... 12Z TAFs: Any lingering ground fog is expected to dissipate by 12Z this morning. Ongoing 12Z CHS sounding observed a llvl inversion with close dewpoint depression. As temperatures warm this morning, cumulus with MVFR bases are forecast to develop across the terminals. The low cloud cover may become BKN at times at KSAV, highlighted with a TEMPO between 13-15Z. Otherwise, conditions will remain VFR with light ESE winds. No convection is expected at the TAF sites this Independence Day. As the case in recent years, following this evening`s pyrotechnic displays, smoke or haze may result in periods of visibility restrictions at the terminals tonight. Forecast soundings indicate that a BL inversion may form as early as 2-3Z with light and variable winds. Future TAF issuances may include some degree of visibility restrictions associated with firework smoke. Extended Aviation Outlook: Brief flight restrictions are possible in showers and thunderstorms, mainly in the afternoon and evenings, through the middle of next week. && .MARINE... Today and Tonight: NE winds in the morning will clock around to the ESE in the afternoon with the formation of the sea breeze. Expect the strongest winds along the land/sea interface in the afternoon, and across Charleston Harbor. Gusts in these locations could approach 20 kt. Winds should shift to the S in the evening, then the SW overnight. Seas will average 2-3 ft. Little or no convection is forecasted. Friday through Tuesday: Southerly flow will persist through early next week. Marine conditions will remain well below small craft advisory criteria, with speeds 15 knots or less and seas 2-3 feet. Rip Currents: Today: The combination of a SE swell around 8 seconds, onshore winds this afternoon, and the approaching new moon will lead to a Moderate Risk of rip currents at all of our beaches. Friday: A swell of 2 feet every 10 seconds and proximity to the new moon will maintain an enhanced risk of rip currents on Friday. A Moderate risk is forecast at all area beaches. && .CHS WATCHES/WARNINGS/ADVISORIES... GA...None. SC...None. MARINE...None. && $$ NEAR TERM...NED SHORT TERM...ETM LONG TERM...ETM AVIATION...NED MARINE...ETM