Area Forecast Discussion
Issued by NWS Charleston, SC
Issued by NWS Charleston, SC
170 FXUS62 KCHS 171803 AFDCHS Area Forecast Discussion National Weather Service Charleston SC 203 PM EDT Thu Jul 17 2025 .SYNOPSIS... Sub-tropical high pressure will prevail through the weekend, then a cold front will stall nearby into the area early next week. && .NEAR TERM /THROUGH TONIGHT/... Rest of this afternoon: Scattered to isolated showers will continue to slowly push inland with south-southwest low level flow around the west side of a deep layer sub-tropical ridge. Brief thunderstorms will be possible, especially over our GA zones and interior SC zones. Temperatures in the lower to mid 90s, coupled with dewpoint temperatures in the lower to mid 70s, will result in max heat indices of 100-105 degrees. Tonight: Any showers or isolated storms are expected to dissipate quickly with the loss of heating. The rest of the night is expected to be mostly clear to partly cloudy, but warm, with lows again in the mid to upper 70s, except near 80 close to the coast. && .SHORT TERM /FRIDAY THROUGH SUNDAY/... This deep layered ridge centered across the Atlantic waters will expand across the region over the weekend, maintaining typical summertime conditions for the Lowcountry. Temperatures slowly increase as this ridge expands overhead, with highs in the mid to upper 90s (with cooler temperatures along the coastline). With this, heat indices could reach above 108F on Saturday and Sunday and a Heat Advisory may be needed. Thanks for fairly strong dry air at the mid-levels, shower and thunderstorm activity should be fairly limited and PoPs were left at 20-30%. && .LONG TERM /SUNDAY NIGHT THROUGH WEDNESDAY/... Heading into the work week, this aforementioned high pressure eventually begins to breakdown as the ridge axis shifts more westward over the Gulf. A series of shortwaves will pass through the region from the north throughout the period. This pattern change will setup for a more active and rainy week ahead. Additionally, a weak surface front might stall nearby on Monday afternoon, possibly lingering into Tuesday. Temperatures will remain near and slight above normal for this time of the year. && .AVIATION /18Z THURSDAY THROUGH TUESDAY/... The 18z TAF period KCHS, KJZI, and KSAV will be dominated by VFR conditions. Isolated to scattered showers are expected to mainly push inland of KCHS and KJZI through this afternoon and evening. KSAV will have the threat for a shower, possibly a brief thunderstorm through about 20z this afternoon. Wind gust of 15 to 20 knots likely through through this afternoon. 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: No highlights are expected. Breezy conditions will continue near the coast and within the Charleston Harbor, where south-southwest winds will gust to 15 to 20 knots. Scattered showers beyond 20 nm are not expected to move any closer to the coast through the afternoon. Seas 2 to 3 feet. Tonight: Winds generally southwest 5 to 15 knots with seas remaining 2 to 3 feet. Isolated to scattered showers late, mainly beyond 20 nm offshore. Friday through Tuesday: Expect generally south to south-westerly flow at 10 to 15 kt. This flow pattern will generally be driven by the circulation around the subtropical high pressure centered over the western Atlantic. It could become a bit gusty each afternoon with gusts up to 15 to 20 kt as the seabreeze pushes inland (gusts strongest across the immediate coastline and the Charleston Harbor). Mix of southerly windswell and underlying southeast swell will be on tap throughout the period. This could set up some good surf for the local beaches over the next couple days. Seas will range from 2 to 3 ft, except a brief swell of 3 to 4 ft on Saturday night through mid- day Sunday across the South Carolina nearshore waters. Otherwise, no marine concerns expected. && .CHS WATCHES/WARNINGS/ADVISORIES... GA...None. SC...None. MARINE...None. && $$ NEAR TERM...RFM SHORT TERM...Dennis LONG TERM...Dennis AVIATION...RFM MARINE...Dennis/RFM