Area Forecast Discussion
Issued by NWS Charleston, SC
Issued by NWS Charleston, SC
822 FXUS62 KCHS 161756 AFDCHS Area Forecast Discussion National Weather Service Charleston SC 156 PM EDT Wed Jul 16 2025 .SYNOPSIS... Atlantic high pressure will prevail through early next week. && .NEAR TERM /THROUGH TONIGHT/... This Afternoon and Tonight: Atlantic high pressure will persist in the upper levels while high pressure centered over the southeastern states dominates at the surface. A tropical-like airmass will remain in place, with SPC Mesoanalysis showing PWAT values between 1.9" and 2.1". Onshore flow will continue to usher in showers with an occasional grumble of thunder off of the Atlantic waters. The 12Z HREF appears to have a decent handle on the current radar trends, indicating that shower activity will begin to wane around 4/5PM and remaining dry through the overnight period. Temperatures this afternoon have reached into the low 90s across the region, with some locations reaching heat index values of 100-103F. The short-lived shower activity has kept heat index values in check though, providing a brief moment of relief from the hot and muggy conditions. Temperatures will remain mild overnight, with mid 70s inland and around 80 at the coastline. && .SHORT TERM /THURSDAY THROUGH SATURDAY/... A strong deep layered ridge will continue to gradually build Thursday through Saturday, bringing increasingly hot and humid conditions. Friday and Saturday will feature highs in the mid/upper 90s, dewpoints in the mid/upper 70s, and heat indices topping 108 in some places and the dry air/subsidence aloft limits afternoon convection. We could need Heat Advisories for part of the area both days. && .LONG TERM /SATURDAY NIGHT THROUGH WEDNESDAY/... By Sunday the forecast becomes more uncertain as H5 heights begin to slowly fall. Well above normal temps and heat index values in the 105-110 range could persist, but are very dependent on afternoon convection which, based on the upper pattern, will likely be greater in coverage that previous days. The upper ridge axis will shift west of the area early next week, allowing some shortwave energy to rotate in from the north. This is expected to result in an increase in convective coverage Monday and Tuesday, with diurnal trends most likely. Toasty conditions will continue into Monday, with Heat Advisories again possible. Temps expected to trend closer to normal by Tuesday. && .AVIATION /18Z WEDNESDAY THROUGH MONDAY/... VFR will prevail through the 18Z TAF period at KCHS/KJZI/KSAV. VCSH has been included at all three TAF sites into this evening as showers continue to stream onshore. No TEMPO groups including any restrictions have been included in the 18Z TAFs as confidence is very low on direct impacts to the terminals. Overall the precipitation will generally be thunder-free, however a grumble or two of thunder cannot be ruled out. Shower activity will wane with nightfall, and likely remain rain-free through the overnight period. Extended Aviation Outlook: VFR will mainly prevail throughout the period, however brief flight restrictions are possible within showers and thunderstorms that develop in the afternoon and/or evening hours. && .MARINE... Rest of This Afternoon and Tonight: High pressure will dominate across the marine waters through the rest of today and through the overnight period. Generally 10 to 15 knots is expected, with the flow transitioning from S/SE to S/SW overnight. Seas should average 2 to 3 ft. Isolated to scattered showers will persist across the waters into this evening, with showers diminishing into the overnight period. High pressure will prevail Thursday through Monday, maintaining typical summertime weather in the marine area. No headlines expected. && .CHS WATCHES/WARNINGS/ADVISORIES... GA...None. SC...None. MARINE...None. && $$ NEAR TERM...CPM SHORT TERM...CEB LONG TERM...CEB AVIATION...CEB/CPM MARINE...CEB/CPM