LAGUNA BEACH, Fla. -- The National Hurricane Center says Subtropical Storm Alberto has come ashore on the Florida Panhandle.
The Miami-based center said in a 5 p.m. EDT advisory that Alberto's core made landfall Monday at Laguna Beach, Florida, about 15 miles west-northwest of Panama City.
Forecasters say heavy rainfall and flash flooding are the biggest threats posed by the storm as it heads inland over the Florida Panhandle. With maximum sustained winds of 45 mph, Alberto was moving north at 9 mph.
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.
The storm was expected to weaken as it continues moving inland. But forecasters said it will dump heavy rain on parts of the Florida Panhandle, Alabama and Georgia, raising the risk of flash flooding.
Rough conditions were roiling the seas off the eastern and northern Gulf Coast region, and officials warned swimmers to stay out of the water through Tuesday due to life-threatening swells and rip currents.
Between four and eight inches of rain could pummel Florida Panhandle, eastern and central Alabama, and western Georgia. Isolated deluges of 12 inches were possible. The Florida Keys were likely to get several inches of rain. Two to six inches were possible from Tennessee east through the Carolinas.
Lifeguards posted red flags along the white sands of Pensacola Beach, where swimming and wading were banned amid high surf and dangerous conditions. Gusty showers began lashing parts of Florida on Sunday, and authorities warned of the possibility of flash flooding.
The hurricane center said a tropical storm warning was in effect from the Suwannee River in Florida to the Alabama-Florida state line.
About 2,600 customers were without power in northwestern Florida on Monday morning, according to Florida's Division of Emergency Management.
Mark Bowen, the Bay County Emergency management director, said Alberto's biggest threat would be its heavy rains, with forecasts of anywhere from four to 12 inches (10 to 30 centimeters) of rain in some areas. Storm surge flooding was less of a concern because Alberto's arrival would not coincide with high tide, he said.
Some tourists said the rainy weather would not dampen their vacations.
Janet Rhumes said her group of friends from Kansas had been planning their Memorial Day weekend on Navarre Beach since October, and no tropical storm could deter them.
"We've never seen one before and we're here celebrating a friend's 20th birthday," Rhumes told the Northwest Florida Daily News. "So how often can you say you rode a storm out?"
Rhumes said her group prepared for the storm by stocking up on groceries.
"We're going to play cards and if there's a break, we'll head down to the beach," she said. "We'll hang out and see how it goes."
In Miami, organizers called off the sea portion of the Miami Beach Air & Sea Show on Sunday because of heavy rain and rough waters. And in the Tampa Bay area on the central Gulf Coast, cities offered sandbags for homeowners worried about floods.
The National Oceanic and Atmospheric Administration released a hurricane season forecast Thursday that calls for 10 to 16 named storms, with five to nine hurricanes. One to four hurricanes could be "major" with sustained winds of at least 111 mph (178 kph).
If that forecast holds, it would make for a near-normal or above-normal season. An average hurricane season produces 12 named storms, of which six become hurricanes, including three major hurricanes.