Area Forecast Discussion
Issued by NWS Charleston, SC
Issued by NWS Charleston, SC
420 FXUS62 KCHS 182232 AFDCHS Area Forecast Discussion National Weather Service Charleston SC 632 PM EDT Fri Jul 18 2025 .SYNOPSIS... High pressure will prevail in the Atlantic through early next week, with surface troughing inland. A front could stall nearby towards the middle of next week. && .NEAR TERM /THROUGH SATURDAY/... Rest of today: Aloft, a large anticyclone centered just north of the Bahamas with the ridge axis solidly in control across the forecast area. At the surface, high pressure just to our east over the western Atlantic will continue to drive low-lvl southerly flow. With temperatures into the 90s, combined with dewpoints in the mid-70s, heat indices have been ranging from 107 to 109 today, especially along and east of I-95. If heat indices remain above 108 for 2 hours or more, a Heat Advisory will be issued. However, opted for a Special Weather Statement regarding the heat until 6PM for portions of southeastern South Carolina and southeastern Georgia (will expire at 6PM EDT). Recent satellite and radar shows that the seabreeze has already kicked inland and allowed some relief from the heat. Also, showers and thunderstorms along the Charleston County has started to initiate off the seabreeze as it continues to move inland. MLCAPE values ranging from 2500 to 3250 J/kg with DCAPE values of above 1000 J/kg, any shower and thunderstorm will pose a microburst risk given the environment. Additionally, with PWATs ranging from 1.75 to 2.0 inches, a flood advisory might be needed for any shower, or thunderstorm, that stalls over an area. Tonight: With the sea breeze pushing inland, any storms ongoing in the early evening hours should progress inland and steadily diminish through the late evening. The rest of the overnight should be quiet with very warm/muggy conditions. Lows will only fall into the mid to upper 70s for most of the area with the coastal corridor likely struggling to fall below 80. && .SHORT TERM /SATURDAY NIGHT THROUGH MONDAY/... The weekend will feature ridging aloft over the western Atlantic prevailing over the local forecast area. Additionally high pressure will dominate at the surface. This will yield PoPs below climo both Saturday and Sunday, with no mentionable PoPs on Saturday and only around 20% on Sunday. The main forecast highlight through the weekend will be the heat. High temperatures in the mid to upper 90s, with some spots possibly reaching triple digits, combined with dew points in the low to mid 70s will result in heat index values around 105 to 110F. A Heat Advisory will likely be required on Saturday and possibly again on Sunday. Monday will feature more coverage of showers and thunderstorms, with PoPs around 40% across the region. While Monday will still be hot and muggy, afternoon thunderstorms should provide some relief to the heat and lessen the chance of a Heat Advisory. On Monday a strong to marginally severe thunderstorm cannot be ruled out as the environment will be supportive of damaging wind gusts. Heavy rainfall is also possible on Monday within any thunderstorm as PWATs are forecast to be upwards of 2.2 inches. Any convection should wane with nightfall, with each overnight featuring temperatures in the mid to upper 70s, warmest along the beaches. && .LONG TERM /MONDAY NIGHT THROUGH FRIDAY/... Ensembles are generally in good agreement through the long term period, with an upper level ridge remaining in place. At the surface a weak cold front is expected to sag into the region mid-week, providing an, albeit weak, forcing mechanism for showers and thunderstorms each afternoon. A slightly wetter pattern is forecast through the end of the week, with diurnal convection forecast each afternoon. Temperatures will remain near to slightly above normal. && .AVIATION /00Z SATURDAY THROUGH WEDNESDAY/... VFR at all terminals through 00Z Sunday. Extended Aviation Outlook: Mainly VFR. Though, there could be brief flight restrictions due to afternoon/evening showers and thunderstorms. && .MARINE... Rest of today: High pressure will remain the primary feature just to the east of the local waters through tonight. This setup will continue to drive south to southwest flow across the local waters in the 10-15 knot range, with some gusts approaching 20 knots possible. This will especially be true along the land/sea interface early this evening including Charleston Harbor. Overnight, southwest winds will continue to average around 15 knots. Seas are expected to average 2-3 feet through the period. Extended Marine: High pressure will prevail in the Atlantic through early next week, while surface troughing is inland. This will yield a typical summertime wind pattern. Each day, expect backing winds with the formation of the afternoon sea breeze. The highest gusts will be along the land/sea interface and across Charleston Harbor (with its passage). Each night, expect veering of the winds as a nocturnal jet tries to set up close to shore. Winds will change both speed and direction as a front approaches and stalls nearby towards the middle of next week. && .CHS WATCHES/WARNINGS/ADVISORIES... GA...None. SC...None. MARINE...None. && $$ NEAR TERM...Dennis SHORT TERM...CPM LONG TERM...CPM AVIATION...BRS/CPM MARINE...CPM/Dennis