After a small taste of early fall with some refreshing temperatures and much-welcomed sunshine, another system is approaching from the west. This low-pressure system will move over the Gulf Coast, and another cold front, attached to a larger low-pressure system moving over the Great Lakes and Northeast, will enhance cloud coverage and inject enough instability over the area to produce numerous showers and thunderstorms across South Carolina, more pronounced late Sunday and into Labor Day and Tuesday.
From the low-pressure system emerging from the Southern Plains, a slow-moving front extends over Florida. This is the same front that has been affecting the Florida Peninsula this week. This front is moving very slowly northward and will turn into a warm front as the low-pressure system approaches from the west. Luckily, it seems like it will stay south enough to keep the thunderstorm activity confined to about 30 % across the Lowcountry and western Midlands, at best.
Saturday's forecast
The Upstate and most of the Midlands will remain dry. The Lowcountry will receive a few more showers and perhaps a thunderstorm or two. In fact, the Lowcountry, especially the immediate coast, will continue to have a marginal flash flood risk on Saturday and Sunday.
Sunday's forecast
The wind flow coming in from the Atlantic will inject moisture, and the instability from the low-pressure system will be the culprit for the numerous and widespread showers. Most of the activity will remain focused along the immediate coast.
Labor Day & early next week
The low-pressure system will remain east of South Carolina and stay close enough to continue bringing instability and increasing the chance for showers and thunderstorms, especially in the afternoon when they will become more numerous and intense at times, and mostly along the coast.