870 FXUS62 KCHS 300218 AFDCHS Area Forecast Discussion National Weather Service Charleston SC 1018 PM EDT Thu Jun 29 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 FRIDAY MORNING/... Late this evening: Plentiful cirrus will continue to stream in from the northwest as it blows off from upstream convective clusters. This will be the main cloud cover through the overnight. Overall, expect a quiet night. Can't rule out a brief period of shallow ground fog around sunrise, but it shouldn't cause any significant visibility issues. && .SHORT TERM /6 AM FRIDAY MORNING THROUGH SUNDAY/... Friday: Mid level High pressure will be centered over the Lower MS Valley while a trough is offshore. The trough will get pushed a little further offshore as time progresses due to the High moving slowly to the east. This will cause heights to gradually rise over our area. Surface High pressure centered roughly to our north in the morning will shift offshore into the afternoon. Though, another area of High pressure will approach from the Gulf of Mexico. Moisture is forecasted to increase into the afternoon and evening, with PWATs rising to near 2", which is a bit above normal. However, instability is not overly impressive for this time of year. Models indicate MLCAPEs struggling to reach 1,000 J/kg in the afternoon far inland. But even with this in mind, various models hint at isolated to maybe scattered convection along the sea breeze in the afternoon and evening, followed by potentially some convection approaching from Central SC and GA in the evening. This seems reasonable, given it's tough to be completely dry this time of year. We have slight chance POPs to account for this. It should be mainly dry after midnight. Highs will remain several degrees above normal, well into the 90s, except cooler at the beaches. Heat indices should peak just above 100 degrees. Overnight lows will be in the 70s. Saturday: The mid-levels will consist of High pressure over the Deep South in the morning. It's expected to slowly move into the rest of the Southeast as time progresses. Though, it should 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 Gulf of Mexico. Moisture will continue to be around 2" across our area. Likewise, models indicate the potential for some convection forming along parts of the sea breeze in the afternoon and then moving inland. Once again, instability is not impressive, with MLCAPEs struggling to reach 1,000 J/kg. So while isolated to scattered convection is certainly possible, the overall severe risk appears to be low. Any convection that develops is expected to dissipate in the evening. As for temperatures, they should be slightly higher than on Friday, peaking well into the 90s away from the beaches, with some areas making a run for the century mark. Heat indices also increase, peaking around 105 degrees. At this time, it's not hot enough to warrant a head advisory, with the criteria being 110 degrees. Overnight lows will again be in the 70s. Sunday: Mid-level High pressure will move over the Southeast, weakening as it does so. This is because an approaching trough will stretch from the Great Lakes Region into the Lower Plains. Surface High pressure becomes less noticeable nearby as troughing develops over the Mid-Atlantic and Southeast during the afternoon. Moisture will continue to persist, with PWATs possibly increasing above 2" across our area. Instability also appears to increase across a larger portion of our area. Therefore, scattered convection is possible along the sea breeze in the afternoon. This may be the day with the hottest temperatures. They should peak in the mid to upper 90s away from the beaches, with some areas maybe reaching 100 degrees. Heat indices should peak around 110 degrees, so Heat Advisories may be needed before the convection develops. && .LONG TERM /SUNDAY NIGHT THROUGH THURSDAY/... The ridge will shift east of the area Sunday night through the middle of next week, yielding an increase in shortwaves. Meanwhile, a relatively tropical airmass will be in place. Mainly afternoon/evening showers and thunderstorms are expected. A Heat Advisory could be needed again on Monday. Temperatures trend cooler Wednesday and Thursday. && .AVIATION /02Z FRIDAY THROUGH TUESDAY/... VFR conditions are expected to prevail at KCHS, KJZI, and KSAV through 00z Saturday. Can't rule out a brief period of shallow ground fog right around sunrise, but no visibility reductions are expected. The chance of a thunderstorm will be a bit higher Friday afternoon, but overall coverage will remain isolated at best so certainly no mention of thunder in the TAF at this point. Also, expect a stronger sea breeze so southerly winds could get breezy late in the period. Extended Aviation Outlook: Mainly VFR. There are Low probabilities of afternoon/evening flight restrictions due to convection Friday through Sunday. Flight restrictions appear more likely Monday and Tuesday afternoon/evening due to convection. && .MARINE... Tonight: No marine concerns tonight as high pressure prevails. East/southeast winds will persist through much of the night with speeds 10 knots or less and seas 1-3 feet. High pressure will prevail near our region through most of next week. The High is not expected to bring our area significant winds during this 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: Our internal calculator indicates a potentially elevated threat of rip currents on Saturday due to onshore winds and swell. Additionally, the weather will be nice ahead of the holiday. We went with a Low Risk for now, but this may need to be upgraded with future forecasts. && .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 && .CHS WATCHES/WARNINGS/ADVISORIES... GA...None. SC...None. MARINE...None. && $$ NEAR TERM...BSH SHORT TERM... LONG TERM... AVIATION...BSH MARINE...ETM CLIMATE...