AFD_CHS

FXUS62 KCHS 020145 AFDCHS

Area Forecast Discussion National Weather Service Charleston SC 945 PM EDT Tue Jul 1 2025

.SYNOPSIS...

A cold front is expected to move into the area Wednesday and Wednesday night and could then linger along or just off the coast through the weekend.

.NEAR TERM /UNTIL 6 AM WEDNESDAY MORNING/...

Tonight: Aloft, a mid-lvl trough will continue to advance east across the Ohio/Tennessee Valleys and towards the East Coast through the night. At the sfc, a cold front will make progress towards the region, but will stay west of the local area while high pressure remains anchored offshore. An isolated shower/thunderstorm can not be ruled out overnight, especially over the interior where increasing moisture and some upper level support resides. Temperatures will only fall to the low to mid 70s, except upper 70s at the immediate coast, with cloud cover and 5-10 mph southerly wind occurring during the second half of the night.

.SHORT TERM /6 AM WEDNESDAY MORNING THROUGH FRIDAY/...

Wednesday through Friday: Aloft, the mid to late week period will begin with troughing in place as a shortwave passes through on Wednesday and then offshore Wednesday night. Then for Thursday and Friday ridging will build to the west and the forecast area will be situated within northwest to north flow aloft. At the surface, an upstream front will draw closer to the area on Wednesday and then become rather ill-defined just along or off the coast through Friday. Wednesday continues to look like the most convectively active day thanks to the front approaching from the west, the aforementioned trough aloft, and the presence of a feed of ~2.25" precipitable water across the region. Compared to yesterday's guidance, there appears to be an inland shift to the axis of greatest convective coverage where the best moisture should reside. This could mean that the best coverage and locally heavy rainfall potential will be inland during the day, then shift to the coast and offshore during the evening and overnight. The severe threat continues to look minimal. Convective coverage is then expected to lessen each day Thursday and Friday with lower precipitable water values and the weak front situated offshore. Highs are expected to be in the upper 80s to right around 90 for Wednesday, then back back into the low to mid 90s by Friday.

.LONG TERM /FRIDAY NIGHT THROUGH TUESDAY/...

Overall, the forecast is for pretty typical summertime conditions this weekend into early next week. Convective coverage looks as though it will be on the lower end, with isolated to scattered coverage each day (favoring the coast). Temperatures should be typical with widespread low 90s and even some mid 90s at times. We continue to keep an eye on the weak front along or just off the coast as some model guidance suggests that an area of low pressure could develop along it somewhere from the northeast Gulf to the Southeast coast through the weekend. NHC continues to highlight this area with a low chance for tropical development in the Tropical Weather Outlook.

.AVIATION /02Z WEDNESDAY THROUGH SUNDAY/...

VFR conditions are expected at CHS/JZI/SAV through at least 12-15Z Wednesday, but guidance does indicate increasing chances of showers and thunderstorms across the region late Wednesday morning and afternoon. Flight restrictions will be possible with activity, but confidence in convection timing at any terminal remains low for inclusion of restrictions in the latest TAF issuance. For now, VCSH and VCTS prevailing groups have been started at CHS/JZI at 15Z and 21Z Wednesday, while VCTS has also been introduced at SAV at 20Z Wednesday. Breezy winds are also possible at the terminals Wednesday afternoon, with gusts up to the 15-18 kt range.

Extended Aviation Outlook: The best chance for thunderstorm impacts will come Wednesday evening and possibly overnight. Thunderstorm chances should decrease for Thursday and then especially Friday through the weekend.

.MARINE...

Tonight: A tight pressure gradient between an Atlantic high centered offshore and a trough inland will maintain southerly winds averaging in the 15-20 kt range across local waters this evening, although a few gusts up to 25 kt remain possible across the Charleston County waters during the next hour or two. Winds will settle a bit after midnight to around 15 kt across most waters. Seas 3-5 ft initially will gradually subside to 2-4 ft by daybreak Wednesday.

Wednesday through Sunday: Elevated south to southwest flow is expected across the local waters on Wednesday, with speeds mostly topping out in the 15-20 knot range. Thereafter, the gradient is quite weak on Thursday and should remain no more than 15 knots through the weekend. Seas should peak 2-4 feet on Wednesday, then average 2-3 feet thereafter. Also of note, the area that stretches from the northeast Gulf to the Southeast coast continues to be monitored for possible tropical development through the weekend. An area of low pressure could form along a lingering front, and NHC continues to highlight this area with a low chance of tropical development.

.CHS WATCHES/WARNINGS/ADVISORIES...

GA...None. SC...None. MARINE...None.

NEAR TERM...DPB SHORT TERM...BSH LONG TERM...BSH AVIATION...BSH/DPB MARINE...BSH/DPB