Area Forecast Discussion
Issued by NWS Charleston, SC
Issued by NWS Charleston, SC
923 FXUS62 KCHS 111012 AFDCHS Area Forecast Discussion National Weather Service Charleston SC 612 AM EDT Mon Aug 11 2025 .SYNOPSIS... A stationary front to the south of the region should dissipate today. By mid to late week, surface high pressure will shift into the Atlantic, while weak troughing forms inland. && .NEAR TERM /THROUGH TONIGHT/... The upper-level anticyclone that has been positioned well offshore of the Southeast U.S. for the past several days will begin to build west today and replace the mid-level weakness that has been in place since last Friday. The atmosphere will remain modestly unstable through the afternoon with a plume rich, tropical moisture featuring PWATs holding in the 2.30-2.65". Similar to the past few days, passing bits of vorticity propagating along the western periphery of the upper high will bring several more bands/waves to showers/tstms to the area. Pops today peak 70-90% with 30-50% tonight. Models have been struggling on the exact timing, coverage and placement of these convective clusters which is impacting the ability to pin down where the corridors of heaviest rainfall will set up. The highest rain totals since Friday have been mostly confined to the coastal counties which should continue again today. Some areas have seen as much as foot of rain over the past several days alone which is downright incredible for August outside of a tropical cyclone. Although the net QPF will feature lower overall values through the afternoon with an overall more progressive convective pattern, HREF neighborhood probabilities still support localized amounts >4" where pockets of convective training occur. The risk for flash flooding will remain elevated as a result, especially in the more urbanized areas around Charleston, Beaufort, Savannah and Hinesville. The Flood Watch for the coastal counties has therefore been extended until 6 PM. This may be a bit long for parts of the Georgia coast where much of the convection may push north of there by late morning/early afternoon, so parts of the watch may need to be cleared early. The risk for heavy rainfall/flooding will linger along the lower South Carolina coast until mid-late afternoon. Convection may very well well redevelop over the Atlantic overnight into the early morning hours Tuesday, but current indications suggest coverage will be considerably less than the past several nights. Highs today will range from the lower-mid 80s across the South Carolina Lowcountry with mid-upper 80s across Southeast Georgia. Even a few spots near the Altamaha River could reach 90 with heat indices of 100-103. Overnight lows will range from the lower 70s well inland to the upper 70s/near 80 at the beaches and Downtown Charleston. && .SHORT TERM /TUESDAY THROUGH THURSDAY/... High pressure aloft centered over the western Atlantic will extend into the southeastern states on Tuesday, with the center slowly shifting westward towards the coastline through Thursday. Similarly, high pressure will prevail at the surface. This pattern will support a return to a more typical summertime pattern of diurnally driven showers and thunderstorms and hot and humid conditions. Strong to marginally severe thunderstorms will be possible each afternoon, with CAPE values around 2000 J/kg. There is also the threat of locally heavy rainfall, with PWAT values around 2". Heat index values are forecast to reach triple digits across portions of the region through the period, however the current forecast keeps conditions shy of Heat Advisory criteria. && .LONG TERM /THURSDAY NIGHT THROUGH SUNDAY/... High pressure will dominate at the surface and aloft into the weekend. This pattern should yield a typical summer-time pattern with afternoon thunderstorms and hot and humid conditions. Heat index values will reach triple digits, with 100-105F in the forecast, shy of Heat Advisory criteria. && .AVIATION /10Z MONDAY THROUGH FRIDAY/... 11/12z TAF Discussion: KCHS/KJZI/KSAV: Unsettled conditions will persist at the terminals today with bands of showers/tstms poised to cross the area. Conditions look to remain largely VFR, except MVFR during periods of rain. Bulk of shower/tstm activity looks to clear KSAV by mid-morning and mid-afternoon at KCHS/KJZI. Various TEMPO groups were used to highlight MVFR conditions in RA during these times. Risk for tstms is there, but probabilities are too low to mention at this time. Extended Aviation Outlook: Brief flight restrictions will be possible due to afternoon showers/thunderstorms. && .MARINE... Through Tonight: No concerns. East/southeast winds 15 kt or less will prevail with seas 2-4 ft. Vsbys could drop below 1 NM at times in pockets of heavy rainfall. Tuesday through Saturday: High pressure will prevail over the local waters through the week. The forecast features winds SE/S around 10 to 15 knots. Some gusts could approach 20 knots along the coastline due to the afternoon sea breeze. Seas should average 2 to 3 ft. && .CHS WATCHES/WARNINGS/ADVISORIES... GA...Flood Watch until 6 PM EDT this evening for GAZ116>119-138>141. SC...Flood Watch until 6 PM EDT this evening for SCZ048>051. MARINE...None. && $$