J.D. Gallop, Elizabeth LaFleur and John Bacon

USA TODAY NETWORK

MELBOURNE, Fla. — Evacuation of hundreds of thousands of people was underway Wednesday in Florida and South Carolina as Hurricane Matthew roared closer to the U.S. after leaving 16 people dead and carving a path of destruction across Haiti.

The impending weather prompted Florida Gov. Rick Scott to ask President Obama to declare a pre-landfall emergency, activate 1,000 more National Guard members to join the 1,500 already positioned in the state and suspend all tolls in the affected areas, including the entire Florida Turnpike, Alligator Alley, Central Florida Expressway Authority and the Miami-Dade Expressway Authority.

"Based on the most recent forecast I received from the National Hurricane Center, the eye of Hurricane Matthew is going to be much closer to Florida," Scott said Wednesday night in a statement. "There are hurricane watches and warnings along Florida’s entire east coast and we now have Tropical Storm warnings on Florida’s Gulf Coast. This storm is serious and protecting life remains our number one priority."

During a briefing with reporters earlier Wednesday, Scott also implored those who had been ordered to evacuate to do so.

"There is absolutely no excuse not to evacuate," Scott said during the briefing at the Brevard County Emergency Operations Center in Rockledge, Fla. "If you are able to leave early, go now," before evacuation-related traffic tie-ups get worse."

"We can rebuild your home. We can rebuild your business," Scott said. "We cannot rebuild your life."

The governor added that the state is "preparing for the worst, hoping for the best and not taking any chances.

Tropical storm conditions are expected to reach parts of the Florida coast by early Thursday, intensifying to hurricane conditions in some areas later that day, the National Hurricane Center warned. Matthew had top sustained winds of 115 mph, a Category 3 hurricane on the Saffir-Simpson scale, Wednesday evening and is forecast to strengthen in coming days, the center said.

"People have less than 24 hours to prepare," Scott said. "Having a plan could be the difference between life and death."

Florida, Georgia, South Carolina and North Carolina declared states of emergency ahead of the most powerful storm to rock the Atlantic basin since Hurricane Felix killed more than 100 people, most in Nicaragua, in 2007.

“Residents and visitors should take evacuation orders seriously,” Federal Emergency Management Agency chief W. Craig Fugate said. “This is a major hurricane that has the potential to cause significant harm to life and property.”

. Wednesday evening the storm was about 325 miles southeast of West Palm Beach heading northwest at 10 mph. The storm had weakened but was expected to strengthen later Wednesday and on Thursday, according to the National Hurricane Center.

More coverage of Hurricane Matthew

• Here's the latest forecast

• Meteorologist spots 'sinister' face in Hurricane Matthew satellite image

• Some models predict a one-two punch

• NASA images show Matthew from space

• Airlines waive fees ahead of the storm

The National Hurricane Center placed the entire east coast of Florida under some kind of hurricane or tropical storm warning or watch. A warning means storm conditions are expected within 36 hours, a watch means the conditions are possible within 48 hours. On Wednesday, the more sobering warning stretched from Miami to Daytona Beach.

A hurricane watch was in effect for the northeast Florida coast and the coast of Georgia.

"The combination of a dangerous storm surge and the tide will cause normally dry areas near the coast to be flooded," the hurricane center warned. "There is a danger of life-threatening inundation."

Scott warned residents to prepare for power outages and evacuations. A mandatory evacuation of Brevard County's barrier island began at 3 p.m. Wednesday, Satellite Beach City Manager Courtney Barker announced on her city Facebook page. The evacuation also includes anyone living on Merritt Island, in low-lying flood-prone areas and in mobile or manufactured homes.

"This is a unique and dangerous hurricane. People need to take evasive action," said Don Walker, spokesman for Brevard County's Emergency Management Office.

Airlines canceled nearly 1,600 flights by 9 p.m. Wednesday through Friday in anticipation of Matthew, according to FlightAware.com, an online tracking service.

The number could rise depending on the storm's path. Among the 1,594 cancellations, 124 were Wednesday in the U.S., Bahamas and Haiti, according to FlightAware.

The most cancellations were in Miami with 51 and Nassau with 43.

Among the 1,070 cancelled for Thursday, the most are at Miami with 512 and Fort Lauderdale with 287, according to FlightAware. The airlines most affected are American with 477 and Southwest with 145.

"We expect the number of flight cancellations for (Thursday) and Friday to rise depending on how much Florida is impacted by the storm," said Daniel Baker, CEO of FlightAware.

Hurricane Matthew dominated conversation at South Brevard beachside shopping plazas, where storm preppers encountered gas stations with plastic bags wrapped around the pump handles, an array of early business closures, and long lines inside grocery stores.

Inside the Indian Harbour Beach Publix, Indialantic teacher Barbara Sloop bought more than $100 in hurricane-supply groceries — including toddler and baby food — for an unidentified Melbourne Beach client. Sloop works for Shipt, an online grocery delivery service.

"This customer is very lucky because they got two 24-packs of water. Yesterday, I wasn't able to get much water," Sloop said, loading sacks into her vehicle.

Sloop said she may evacuate to Fort Myers to elude the hurricane.

Cheryl Kazmarek is not in an evacuation area of the county — so far. She said she is ready to ride out the storm in her shuttered Rockledge home with her whole-house generator. And she expects to show up for work Thursday at the Home Depot here.

"It's crazy at the store, non-stop," she said. "People are asking for generators, for plywood, for wingnuts for the plywood. It's all gone."

Scott activated 500 National Guard members, with 6,000 ready to join the fray if needed. Schools and government offices along the coast shut down as the region braced for Matthew's fury.

Walt Disney World Resort, about 60 miles west of Merritt Island, was operating under "normal conditions" on Wednesday but said on its website it was monitoring the storm. Scott said tourists and residents should evacuate vulnerable areas as soon as possible.

"If you made a decision not to leave, we cannot send someone to risk their lives to save yours," Scott said. "We can rebuild a home, we can rebuild a business, we cannot rebuild your life."

South Carolina could see warnings and watches issued later Wednesday. Gov. Nikki Haley ordered evacuations for parts of Charleston and Beaufort counties beginning at 3 p.m. and said 315 buses would shuttle residents to Greenville, 200 miles to the northwest. Ann Wright, executive director of the American Red Cross of the Upstate, said shelters would open for those in need.

Wednesday's evacuation was estimated to include 250,000 people, not counting tourists, Haley said. Hundreds of thousands more could be evacuated Thursday when plans call for evacuations in Georgetown and Horry counties.

Interstate 26 near the coast was turned into a one-way street — west only — when authorities began halting traffic headed toward the storm. Traffic heading toward safety was heavy, and Haley urged resident to stock up on gasoline before stations closed. Bottled water, generators and batteries were among hurricane-preparedness items that were in short supply.

Haley echoed Scott's call for residents not to delay their evacuations.

"If you do not leave, you are putting a law enforcement officer or national guardsman's life on the line when they have to go back and get you," Haley said. "So we are being extremely cautious."

At a Lowe’s store in Myrtle Beach, S.C., the home improvement store had run out of bags of play sand to stack against rising waters and hurricane clips, used to ease installation of plywood against windows. Generators were sold out for a few hours, but a new supply arrived Wednesday evening, as customers were dwindling.

Outside, Jan Fogleman of Fresenius Medical Care, returned to his truck already stocked with plywood, used in years past to cover one of the company’s storefronts, which offers kidney dialysis services.

“We’re probably over preparing, to be honest,” Fogleman said.

The company advised patients who can evacuate to leave. To ensure uninterrupted care for patients, it provided dialysis in its clinics before the evacuations and arranged for evacuated patients to receive treatment in clinics safe from the storm.

At the Charleston Area Convention Center in North Charleston, S.C., people hoping to be evacuated to Greenville began filing in after noon Wednesday.

Reynaldo Acosta, a resident of John’s Island, arrived in a motorized wheelchair with his two caged dogs. His said his chief concern was a loss of electricity.

“I lived through three different hurricanes in Florida,”, he said. “Mostly it’s the after effects, the power outages.”

John Phillips, a Boeing manager from Seattle, said he hadn’t been in a hurricane before and did not want to experience one.

“First I was thinking, maybe it would be kind of interesting to experience,” he said. “But Charleston floods at high tide. And they are talking about storm surges. So it didn’t seem like the wise thing to do.”

In Clewiston, Fla., at the local Wal-Mart, only a single banana remained. The store received a shipment of water Wednesday, but it was gone by evening. All of the bread was sold, but tortillas remained. Canned food dwindled as last-minute shoppers made their purchases.

Near the store, families stopped by an ice station on the Sugarland Highway and filled coolers to the top.

“We came to get ice in case the power runs out,” said 19-year-old Kayla Maynard. “We don’t have a generator so we have to get ice to keep our things cool.”

Maynard said she was unfazed by the category three hurricane at first, but then it began to shift.

“It got closer,” Maynard said.

Gallop reports for Florida Today in Melbourne; LaFleur for The Greenville (S.C.) News; Bacon for USA TODAY. Contributing: Rick Neale, Florida Today; Donna Isbell Walker, The Greenville, (S.C.) News, Tonya Maxwell, Asheville Citizen-Times, Tim Smith, The Greenville (S.C.) News, Dave Berman, Florida Today, Brett Blackledge, Naples News, Melissa Montoya, the News-Press in Fort Myers.