Area Forecast Discussion
Issued by NWS Charleston, SC
Issued by NWS Charleston, SC
120 FXUS62 KCHS 162212 AFDCHS Area Forecast Discussion National Weather Service Charleston SC 612 PM EDT Wed Jul 16 2025 .SYNOPSIS... Atlantic high pressure will prevail through early next week. && .NEAR TERM /UNTIL 6 AM THURSDAY MORNING/... 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 /6 AM THURSDAY MORNING 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 /22Z WEDNESDAY THROUGH MONDAY/... 17/00z TAF Discussion: KCHS/KJZI/KSAV: VFR will prevail through early Thursday evening. Isolated showers/tstms should develop west of the terminals Thursday afternoon, although they could get a little close to KSAV for a brief period before the passage of the sea breeze. 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... Tonight: High pressure will dominate across the marine waters through tonight. 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. Thursday through Monday: High pressure will prevail, maintaining typical summertime weather in the marine area. No headlines expected. && .CHS WATCHES/WARNINGS/ADVISORIES... GA...None. SC...None. MARINE...None. && $$