Tropical Storm Alberto was becoming less organized and weakening off the coast of South Carolina, forecasters said late Sunday. At 11 p.m. EDT, the National Hurricane Center in Miami said the center of Alberto was 135 miles east-northeast of St. Augustine, Fla., and 160 miles south of Charleston, S.C. The storm had maximum sustained winds of 40 mph, with higher gusts, and was moving south at 5 mph. Little change in strength was expected during the next 48 hours. No watches or warnings were posted but forecasters said dangerous surf conditions, including rip currents, were possible through Monday along the northeast Florida, Georgia and South Carolina coasts. The storm was expected to take a gradual turn toward the southeast and east Monday, and then pick up forward speed and turn toward the northeast early Tuesday. On its forecast track, the storm was expected to remain off the Georgia and Carolina coasts, forecasters said. The storm is the first of the Atlantic hurricane season, which begins June 1.