Area Forecast Discussion
Issued by NWS Charleston, SC
Issued by NWS Charleston, SC
846 FXUS62 KCHS 131121 AFDCHS Area Forecast Discussion National Weather Service Charleston SC 721 AM EDT Sun Sep 13 2026 .WHAT HAS CHANGED... Aviation section updated for the 12Z TAFs. && .KEY MESSAGES... - 1) Isolated showers and thunderstorms are forecast to develop along the sea breeze this afternoon. && .DISCUSSION... KEY MESSAGE 1: Isolated showers and thunderstorms are forecast to develop along the sea breeze this afternoon. Early this morning, satellite water vapor shows dry air building east of the Southern Appalachians with the passage of H5 trough. The trough axis is timed to push over the CWA by 15Z, sliding offshore between 18-21Z. PW values across the forecast area will begin the day in excess of 2.2", before falling to below 1.7" by late this afternoon. Forecast soundings shows deep dry air increasing above H6 this afternoon, with a significant inversion centered at H65. High resolution guidance shows isolated showers and thunderstorms developing near the sea breeze this afternoon. However, with increasing dry air, shallow lapse rates, and a H65 inversion any convection should remain general. High temperatures should rise above yesterday`s values, ranging between 90 to 95 degrees. && .AVIATION /12Z SUNDAY THROUGH THURSDAY/... Prior to the 12Z TAFs, IR satellite and observations indicated a small patch of MVFR ceilings over KCHS, expected to dissipate by 14z. Otherwise, conditions across the terminals this morning should feature light west-southwest winds and VFR conditions. The sea breeze should advance inland this afternoon, shifting winds from the southwest. Isolated showers and thunderstorms should develop along the sea breeze this afternoon, but coverage appears too low to highlight in the TAFs at this time. Extended Aviation Outlook: VFR. && .MARINE... Today and Tonight: Weak surface troughing inland will cause WSW winds this morning to back to the SSW this afternoon. Winds will start to veer in the evening, becoming W late tonight. Sustained winds should be in the 5-15 kt range. Seas will average 2-3 ft. Extended Marine: Expect light and varying winds along with low seas Monday morning and afternoon. A cold front will move south through our waters late Monday into Tuesday, followed by High pressure persisting to our north, possibly into Thursday. This will cause NE winds to increase to a strong breeze late Monday into Tuesday. Gusts could even reach near gale across portions of our waters on Tuesday. Winds should ease late Tuesday, before increasing again on Wednesday and Thursday. Wind-driven seas will also build Tuesday, then remain elevated through Thursday. Small Craft Advisories will be needed starting late Monday across our SC waters, and early Tuesday across our GA waters. Some of these Advisories could remain in effect through Thursday. Coastal Flooding: Minor coastal flooding is possible with the Tuesday mid-day high tide along the Charleston and Colleton County coasts. Strengthening northeast winds are expected, which will increase tidal departures. The tide would need ~1 ft departure to reach minor flooding thresholds of 7 ft MLLW in the Charleston Harbor. Most guidance indicates tide levels could rise to that level. A Coastal Flood Advisory could be needed. No flooding is expected further south along the lower SC and Southeast GA coasts. && .CHS WATCHES/WARNINGS/ADVISORIES... GA...None. SC...None. MARINE...None. && $$