June 13 (Bloomberg) -- Tropical Storm Alberto weakened slightly as it approached Florida's Gulf Coast, where some residents were ordered to evacuate before the arrival of the first named system of the Atlantic hurricane season.

Alberto's maximum sustained winds were 65 miles per hour (105 kph) at 5 a.m. Florida time, from 70 mph late yesterday, the National Hurricane Center in Miami said in an online advisory. Florida's Gulf Coast from Longboat Key to the Ochlockonee River was under a hurricane warning, indicating hurricane conditions are expected within 24 hours.

``Although some potential still exists for restrengthening, the likelihood that Alberto will become a hurricane prior to landfall is decreasing,'' the center said. Hurricanes have sustained winds of at least 74 mph.

The storm's eye was about 60 miles southeast of Apalachicola, in Florida's Panhandle, and 65 miles west of Cedar Key, and moving toward the northeast at about 9 mph, according to the advisory. Tropical storm-force winds of between 39 mph and 73 mph extended 175 miles from the storm's center.

"There could be minor structural damage," meteorologist Eric Blake said in a telephone interview from the Hurricane Center. "You don't want to be in a mobile home -- it's not a pleasant place to be."