Hurricane Wilma's march toward Florida slowed somewhat Thursday, giving residents an unexpected extra day to prepare for the storm, while authorities stockpiled emergency supplies.

Forecasters at the National Hurricane Center (search) said Wilma would likely strike Florida's western coast about midday Sunday, a da likely weaken the storm from a Category 4 (search), with sustained 150 mph winds, to a Category 3 or less before making landfall in the United States.

Click here to track Hurricane Wilma.

"The timing is certainly working in our favor," Mayfield said. But he added that Wilma probably would still be a strong hurricane with a powerful storm surge when it reached the state. Category 3 storms have winds of 111 mph to 130 mph.

Gov. Jeb Bush (search) declared a state of emergency to ensure that necessary supplies and disaster response teams were in place.

"This is the time to prepare," Bush told reporters in Tallahassee.

The storm was predicted to make a turn to the northeast toward Florida after striking Mexico's Yucatan Peninsula in the western Caribbean Sea.

Mayfield said Wilma is unusually large, with tropical storm-force winds extending out some 260 miles from the center that could cause widespread damage.

"Don't just focus on the eye of the hurricane," Mayfield said.

State meteorologist Ben Nelson (search) warned that Wilma could produce a storm surge of 12 to 17 feet.

At 5 p.m. EDT, forecasters said Wilma was about 135 miles south-southeast of Cozumel, Mexico, and about 448 miles south-southwest of Key West. It was heading west-northwest at about 6 mph toward Mexico's Yucatan Peninsula, where Mayfield said it could do catastrophic damage.

The storm had strengthened slightly, and forecasters said it could regain Category 5 strength winds of 156 mph or more.

Although Wilma was expected to approach from the west, forecasters warned that major Atlantic Coast cities including Miami, Fort Lauderdale and West Palm Beach could be hit by strong winds and heavy rains.

Bush said the state had food, water, ice and other supplies ready, as well as disaster-response teams that included up to 7,500 National Guard (search) members. "We are battle-tested, well-resourced, well-trained," he said.

The Federal Emergency Management Agency was positioning emergency materials in Jacksonville, Lakeland and Homestead. FEMA acting chief R. David Paulison said the agency has 150 truckloads of ice and 150 truckloads of water, and the Red Cross has 200,000 meals available.

"We are ready for the storm, as much as you can be," Paulison said in Washington.

The governor urged people not to hoard gasoline, which frequently causes long lines at gas stations and some to run out of fuel. Bush said an estimated 200 million gallons of fuel were available at Florida ports, enough for an adequate supply.

In the low-lying, vulnerable Keys, the normally crowded historic district in Key West was eerily quiet Thursday. Tourists and nonresidents were already asked to leave. A mandatory evacuation of residents was expected to start Friday, although some did not seem to be hurried.

Mark Brann was relaxing outside Andy's Scooter Shop where he works. He had little to do without tourists.

"Where are you going to go? They don't know where the storm's going," he said, adding that he thinks he will be safe in his seventh-floor condominium.

Wilma was on a path that could threaten areas hit by Hurricane Charley in August 2004. Some houses and businesses in the area are still boarded up because of that storm.