Subtropical Storm Alberto lumbered ashore Monday on the U.S. Gulf Coast, pelting white sand beaches with blustery winds and stinging rain that kept the usual Memorial Day crowds away.

Forecasters warned heavy rain, flash flooding and dangerous surf posed the biggest threats as Alberto’s ragged core made landfall near Laguna Beach in the Florida Panhandle. A few brief tornadoes also were possible in much of Florida and parts of Georgia, South Carolina and Alabama.

The National Hurricane Center in Miami said at 5 p.m. Monday that Alberto was centered about 15 miles west-northwest of Panama City, Fla. With maximum sustained winds of 45 mph, Alberto was moving north at 9 mph.

Rough conditions were whipping up big waves off the eastern and northern Gulf Coast, and authorities warned swimmers to stay out of the surf because of life-threatening swells and rip currents.

Between four and eight inches of rain could pummel the Florida Panhandle, eastern and central Alabama, and western Georgia before the storm moves on. Isolated deluges of 12 inches also were possible as the storm heads inland, threatening heavy rains around the Southeast in the coming hours and days.

As Alberto’s center heads inland — deprived of the warm waters that fuel tropical weather systems — the storm was expected to steadily weaken. A subtropical storm like Alberto has a less defined and cooler center than a tropical storm, and its strongest winds are found farther from its center. A tropical storm warning is in effect for a stretch of coastline between Aucilla River in Florida’s Big Bend and the Alabama-Florida border.

Lifeguards posted red flags along Pensacola Beach, where swimming and wading were banned.

Meanwhile, the storm forced some Memorial Day tributes to be canceled across Florida’s Panhandle. Safety was the priority, but the decision was still a “heartbreaker,” said Tom Rice, a 29-year-old Army veteran who leads the organizations that planned a ceremony Monday at Beal Memorial Cemetery in Fort Walton Beach.

Some stragglers still made their way through the rain to pay tribute at the cemetery’s Veterans Tribute Tower, however. Rice said American flags had been placed Saturday on the graves of all 1,700 veterans buried in the cemetery.

“We got the flags out,” Rice said. “That’s what’s important.”