956 FXUS62 KCHS 302026 AFDCHS Area Forecast Discussion National Weather Service Charleston SC 426 PM EDT Fri Jun 30 2023 .SYNOPSIS... High pressure will prevail through early next week. Upper level disturbances could affect the area mid to late next week. && .NEAR TERM /UNTIL 6 AM SATURDAY MORNING/... Surface high pressure will persist through tonight. Aloft, the forecast area will remain on the eastern periphery of an upper high centered over the lower MS Valley. Isolated showers and thunderstorm will be possible this afternoon with the sea breeze and also into the evening as some activity potentially develops upstream then moves into the area. A dry forecast is in place for the latter half of the night. Otherwise, mid/higher level clouds will continue to move in overnight. Low temperatures are expected to mainly be in the lower 70s, except in the upper 70s to near 80 at the beaches and in Downtown Charleston. && .SHORT TERM /6 AM SATURDAY MORNING THROUGH MONDAY/... Saturday: The mid-levels will consist of High pressure over the Deep South in the morning. It's expected to slowly drift towards the rest of the Southeast as time progresses. However, it'll start to weaken late, due to a trough approaching from the Central U.S. At the surface, areas of High pressure will be located in the Atlantic and the Gulf of Mexico. There will be plenty of moisture across our area, with PWATs around 2". This is close to the 90% mark for this time of year per SPC CHS sounding climatology. The models still indicate the potential for some convection forming along parts of the sea breeze in the afternoon and then moving inland. Additionally, there could be some convection moving from Central SC and GA towards our inland areas later in the afternoon, perhaps making it to the coast in the evening. One noteworthy change in the models is they indicate more instability, with MLCAPEs reaching 1,000 J/kg across most of our area and pockets far inland approaching 1,500 J/kg. Lapse rates steepen and DCAPEs rise to almost 1,000 J/kg. But 0-6 km bulk shear is 25-30 kt. Isolated to scattered convection is expected, but a widespread severe threat is not. Certainly a stronger storm could produce gusty winds or maybe a brief damaging gust. Any convection that develops is expected to dissipate in the evening. Temperatures will be above normal, peaking well into the 90s away from the beaches. Heat indices should peak around 105 degrees. Overnight lows will be in the 70s. Sunday: Mid-level High pressure will move over the Southeast, while gradually weakening. This is because a trough will pass to our north, generally over the Great Lakes Region. Surface High pressure nearby weakens as troughing develops over the Mid-Atlantic and Southeast during the afternoon, persisting into the night. Moisture will continue to persist, with PWATs possibly increasing to around 2.15" across our area, which is above normal. Instability appears to be a bit less than on Saturday, with lower MLCAPEs and lapse rates. Even the shear is lower. But the models lean towards scattered convection along the sea breeze in the afternoon, moving inland through the evening. The widespread severe risk is low. But this will be a noticeably hot and humid day. Temperatures should peak in the mid to upper 90s away from the beaches, with some areas maybe reaching 100 degrees across inland GA. Heat indices should peak near 110 degrees. Heat Advisories may be needed for portions of our area. But convection could provide some relief before sunset. The convection is expected to dissipate in the evening. Overnight lows will be in the 70s. Monday: The mid-levels will consist of weak High pressure over the Southeast U.S. and a trough moving over the Northeast U.S. At the surface, areas of High pressure will be in the Atlantic and Gulf of Mexico while troughing is over the Southeast. Moisture continues to prevail across the region with our PWATs around 2.15". Models indicate much more instability and convective potential across our area during the afternoon. Likewise, scattered to perhaps numerous convection is expected to develop along the sea breeze in the afternoon, moving inland through the evening. Higher coverage is possible across inland GA. We can't rule out a few marginally severe storms with damaging wind gusts. Similar to Sunday, temperatures should peak in the mid to upper 90s away from the beaches, with some areas maybe reaching 100 degrees. Heat indices should again peak near 110 degrees, so Heat Advisories may be needed for portions of our area. But the convection is the wild card that could bring relief to the heat sooner than expected. && .LONG TERM /MONDAY NIGHT THROUGH FRIDAY/... The ridge will shift east of the area Tuesday. Behind this will be more shortwaves, which will bring a more active pattern through the end of next week. Scattered to numerous diurnally driven showers and thunderstorms are expected nearly each day. Temperatures will remain in the 90s, but trend cooler towards the end of the week. && .AVIATION /19Z FRIDAY THROUGH WEDNESDAY/... Overall VFR conditions will persist at KCHS, KJZI, and KSAV through 18z Saturday. Risk for direct impacts from a shower or thunderstorm this afternoon is too low to include mention in the TAF at this time. Extended Aviation Outlook: Mainly VFR. There are Low probabilities of afternoon/evening flight restrictions due to convection Saturday and Sunday. Flight restrictions appear more likely Monday, Tuesday, and Wednesday afternoon/evening due to convection. && .MARINE... Tonight: No marine concerns tonight. East/southeast winds this evening will turn more southerly towards morning. Speeds will be 10 knots or less with seas 1-3 feet. Extended Marine: The synoptic pattern will consist of occasional High pressure near our region and occasional surface troughs inland. These features are not expected to bring our area significant winds during the extended time period. Each morning and afternoon, expect backing winds due to the sea breeze. The strongest winds will be along the land/sea interface and across the Charleston Harbor. In the evening and overnight, expect veering of the winds, with some higher gusts possible further offshore. No marine headlines are anticipated. Seas will generally be 3 ft or less. Rip Currents: There will be an onshore swell around 2 ft near 8 seconds and gusty winds associated with the afternoon sea breeze this weekend. Both our internal calculator and RCMOS indicate a borderline Low/Moderate Risk for rip currents. Given it'll be a weekend with hot weather and we have a holiday upcoming, we opted to go with a Moderate Risk for all of our beaches. && .TIDES/COASTAL FLOODING... Astronomical tides are increasing in advance of the July 3rd full moon. Additionally, tidal anomalies are increasing. There is a risk for minor coastal flooding at the Charleston Harbor tide gauge with the evening high tides through early next week. && .CLIMATE... Record High Temperatures: July 2: KCHS: 99/1996 KCXM: 101/1931 KSAV: 101/1931 July 3: KCHS: 98/2019 KCXM: 100/1927 KSAV: 101/2019 July 4: KCHS: 98/1993 KCXM: 98/1902 KSAV: 99/1997 Record High Minimum Temperatures: July 1: KCHS: 77/2016 KCXM: 86/1998 KSAV: 81/1897 July 2: KCHS: 78/1987 KCXM: 82/2019 KSAV: 79/1902 July 3: KCHS: 78/2016 KCXM: 81/2016 KSAV: 80/1880 July 4: KCHS: 79/2016 KCXM: 83/1998 KSAV: 79/1931 July 5: KCHS: 78/2017 KCXM: 82/2016 KSAV: 78/2016 July 6: KCHS: 79/1990 KCXM: 81/1998 KSAV: 78/1990 && .CHS WATCHES/WARNINGS/ADVISORIES... GA...None. SC...None. MARINE...None. && $$ NEAR TERM...ETM SHORT TERM... LONG TERM... AVIATION...ETM MARINE...ETM TIDES/COASTAL FLOODING... CLIMATE...