Area Forecast Discussion
Issued by NWS Charleston, SC
Issued by NWS Charleston, SC
260 FXUS62 KCHS 141759 AFDCHS Area Forecast Discussion National Weather Service Charleston SC 159 PM EDT Mon Jul 14 2025 .SYNOPSIS... Atlantic high pressure will prevail into the upcoming weekend. && .NEAR TERM /THROUGH TONIGHT/... This Afternoon: Aloft, a weak upper-lvl ridge will remain across the Southeast as a surface low offshore of the Florida coastline continues to track westward. These features will yield east- northeastward flow throughout the day, which is uncommon for this time of the year. At the surface, this low developing off the Florida coastline will dominate the flow across the region and might cause for a more progressive seabreeze this afternoon. From KCHS 12Z sounding, moderate instability and a K index value of ~35 suggests isolated to numerous thunderstorms will develop in the afternoon (mainly along and west of I-95 corridor). Recent hi- res guidance has been indicating that drier air will be located along the immediate coastline and just inland of the South Carolina coastline with PWAT values from 1.4 to 1.8 inches with the deeper moisture (PWAT values > 2.0 inches) west of I-95. Thus, the current idea remains that showers and thunderstorms will initiate along and west of the I-95 corridor. DCAPE values will be ~800 J/kg, but nothing looks particularly noteworthy in terms of the severe threat. However, there is still a possibility of strong to marginally severe storms where boundary interactions occur. Locally heavy rainfall will be possible along and west of I-95 where the ample moisture and storm coverage is expected. As far as rainfall amounts .. 1-2 inches with higher amounts possible with these storms. Heat index values as of 2PM are generally between 100-106 across the forecast area, just shy of Heat Advisory criteria. As convection begins this afternoon some relief in the heat is expected. Tonight: Showers and thunderstorms should shift further inland and off to the southwest throughout the evening. Temperatures will drop into the mid to upper 70s (with warmer temperatures closer to the beaches). As the developing low offshore of the Florida coastline travels westward, showers and thunderstorms could develop over the coastal waters overnight. Coverage should increase overnight and could draw closer to the coast by daybreak. && .SHORT TERM /TUESDAY THROUGH THURSDAY/... Tuesday: A weakening TUTT will be approaching Florida with dry air located on the northwest flank. PWATs drop to less than 1.5", with 2"+ PWATs on either side. Surface convergence from Monday will have moved further inland over GA on Tuesday with a sea breeze forecast to move inland during the afternoon. The lower PWAT air will likely limit convection slightly, but the overall extent of coverage should still be at least chance. High temperatures will also be lower on Tuesday as 1000/ 850 mb thicknesses fall to 1415 m (or about 10 m cooler than Monday) due to the undercutting TUTT. Wednesday - Thursday: Another TUTT will break off and approach the region Wednesday allowing thunderstorms to continue both days. Storm motions Wednesday are forecast to be around 10 kt, but increase to near 20 kt by Thursday as the TUTT moves overhead and elongates the wind field slightly. This means the greatest chance for locally heavy rainfall will be on Wednesday, with slightly lower chances on Thursday due to increased storm motion. High temperatures will be near climo or in the lower 90s. && .LONG TERM /THURSDAY NIGHT THROUGH SUNDAY/... The TUTT that was near the area on Thursday will cross Florida Saturday keeping afternoon thunderstorm chances in the forecast through the weekend. High temperatures will also remain near climo/ slightly above climo as low level thicknesses slowly recover. Max heat index values each afternoon will be near or just below advisory criteria (108 F). && .AVIATION /18Z MONDAY THROUGH SATURDAY/... 00Z TAFs: Expect VFR conditions to persist at KCHS/KJZI/KSAV. Showers and thunderstorms are expected to develop along and west of I-95 this afternoon and maintained VCTS starting at 21Z. Most of the thunderstorm activity should remain inland of KCHS and KJZI. There is a chance of fog developing at KSAV before daybreak (~09Z), however left the mention out of the TAFs at this moment as confidence is low with this. Extended Aviation Outlook (Tuesday through Saturday): 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... This Afternoon and Tonight: Expect generally northeast to east- northeast flow at 5 to 10 kt to prevail through tonight. This flow pattern will generally be driven by the circulation around the developing low pressure off the Florida coastline. It could become a bit gusty in the afternoon with gusts up to 15 to 20 kt as the seabreeze pushes inland (gusts strongest across the immediate coastline and the Charleston Harbor). Southeasterly swell will continue to mix into the local waters and seas will be 1 to 2 ft. Showers and thunderstorms will develop over the coastal waters tonight and increase in coverage closer to daybreak. Otherwise, no marine concerns expected. Tuesday through Saturday: A TUTT will be located just off of the SC coast through the extended while at the surface Bermuda high pressure will be in control. For the marine zones, this will translate to each afternoon featuring wind gusts peaking 15 to 20 kt due to an inland advancing sea breeze. Seas through the period will be 2-4 ft. && .CHS WATCHES/WARNINGS/ADVISORIES... GA...None. SC...None. MARINE...None. && $$ NEAR TERM...Dennis SHORT TERM...Haines LONG TERM...Haines AVIATION...Dennis/Haines MARINE...Dennis/Haines