COLUMBIA — Gov. Henry McMaster defended his earlier order directing all coastal South Carolinians to flee Hurricane Florence's potential swath of destruction starting Tuesday after he told people in three southern counties they could stay.    

"Part of our team approach to this is to prepare for the worst and hope for the best," he said during an emergency briefing Tuesday. "This is a very dangerous hurricane. We do not want to gamble with a single life of a single South Carolinian." 

McMaster lifted the evacuation order for Beaufort, Colleton and Jasper counties less than an hour before people were supposed to start leaving at noon, calling the decision a "precision adjustment" based on Hurricane Florence's latest predicted path. 

Edisto Beach is an exception. People on that beach, the only part of Edisto Island that's part of Colleton County, still must go, he said.

Even with the exemptions, more than 760,000 people from Charleston County northward are instructed to leave. McMaster's initial order Monday affected more than 1 million people along the entire 187-mile coastline.  

Hurricane Florence is on a path to be the most powerful storm to reach the Carolinas in three decades. It remains a Category 4 storm with 130 mph winds and was expected to keep strengthening. Landfall is expected Friday morning.

Though McMaster calls the evacuation orders mandatory, no one will be forcibly removed from their homes. And no one is being asked to sign waiver forms. But anyone refusing to leave could become a victim of the hurricane, McMaster said.   

"There have been instances of people who simply refused to leave, where they say their house would not be flooded — turns out the water was up over the roof," he said.  

Severe inland flooding and weeks-long power outages are expected, Brock Long, head of the Federal Emergency Management Agency, told President Donald Trump in the Oval Office. 

"These are going to be statewide events," he said Tuesday afternoon while standing behind the president. "These hazards will be statewide."

By early Tuesday, drivers could not go east on Interstate 26 from Columbia to Charleston, as ramps were closed to inbound traffic. Drivers also can't go east on U.S. 501 into Myrtle Beach.

The lane reversals, which occurred on I-26 ahead of schedule, are meant to ease traffic flow for evacuees heading inland.

Traffic flow is expected to increase as the storm approaches, said Department of Transportation Secretary Christy Hall. 

"It's really moving very well," McMaster said Tuesday afternoon after looking at live video of traffic on interstates 26 and 20. 

Because of the exemptions, there's no need to reverse lanes in Beaufort County, McMaster said.  

"This is an unpredictable storm," the governor said. "We must be vigilant. We are in a very deadly and important game of chess with Hurricane Florence." 

Sen. Tom Davis, R-Beaufort, said McMaster deserves credit for altering his order to exempt the coastline's southern-most counties. 

"He exercised sound judgment at a time when, as I know from my own experience in the governor's office, many were probably urging him to be overly and unreasonably cautious," Davis, chief of staff to former Gov. Mark Sanford, wrote in a tweet. "Props, guv." 

Hurricane-force winds extend up to 40 miles from Florence's center, while tropical storm-force winds extend out 150 miles.

Much of the South Carolina coastline has been placed under hurricane and storm surge watches stretching 140 miles from Edisto Beach to the North Carolina border with Florence making landfall in southeastern North Carolina on Thursday.

Storm surges between Edisto Beach and Murrells Inlet could reach 2 to 4 feet, and reach up to 6 feet up to the North Carolina border, the National Hurricane Center said.

While North Carolina could take the brunt of the powerful storm, some forecasters said Florence could swirl back into South Carolina on Friday or Saturday.

Follow Seanna Adcox on Twitter at @seannaadcox_pc.

Assistant Columbia bureau chief

Adcox returned to The Post and Courier in October 2017 after 12 years covering the Statehouse for The Associated Press. She previously covered education for The P&C. She has also worked for The AP in Albany, N.Y., and for The Herald in Rock Hill.