In North Carolina, coastal evacuations were also underway late Monday - with more scheduled to begin on Tuesday.
McMaster formally declared a state of emergency Saturday, allowing officials to put hurricane preparations into effect and begin coordinating resources. "This helps everyone find vital information more easily".
National Hurricane Center Director Ken Graham warned that Florence was forecast to linger over the Carolinas once it reaches shore.
Virginia Governor Ralph Northam's office predicted "catastrophic inland flooding, high winds and possible widespread power outages", cautioning that the deadliest risk would come from flooding.
"The centre of Florence will move over the southwestern Atlantic Ocean between Bermuda and the Bahamas Tuesday and Wednesday, and approach the southeastern coast of the United States on Thursday", the NHC said. "When you stall a system like this and it moves real slow, some of that rainfall can extend well away from the center".
Hurricane Isaac is moving toward the Caribbean and could make landfall Thursday as a Category 1 hurricane.
Sustained winds Monday afternoon were up to 140 miles per hour.
"Also, looking like a direct hit on North Carolina, South Carolina and Virginia".
Florence's centre was expected to move over the Atlantic Ocean between the Bahamas and Bermuda on Tuesday and Wednesday before approaching North and SC on Thursday.
Meanwhile, two other storms were spinning in the Atlantic.
The center of Florence was forecast to sweep between Bermuda and the Bahamas on Tuesday and Wednesday before making its assault on the US coast.
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Florence continued its path toward the East Coast overnight Monday, maintaining its monstrous Category 4 storm status and 140-mph winds.
The airline issued a travel alert for 23 airports in Georgia, North Carolina, South Carolina and Virginia due to Hurricane Florence.
"This is one of the worst storms to hit the East Coast in many years", President Donald Trump warned on Twitter.
Lifelong Wilmington North Carolina, resident Terry Jackson said he and his wife have made a decision to stay and ride out the storm.
People shop at the Harris Teeter, filling up on water and supplies as Hurricane Florence becomes a threat to the coast Monday in Charleston, S.C.
The state Transportation Department likely will begin diverting eastbound traffic off I-26 in Columbia to USA 321 or I-77 north at 8 a.m. Tuesday, it said.
"If the hurricane miraculously, overnight, decides to go somewhere else, we can take corrective action", he said, saying it was easier to "stand down" state resources than have them "stand up" at a moment's notice.
In a 5 p.m. EDT update from the NHC, the storm's winds rose to 140 miles per hour, and it picked up speed in its westward track, doubling its speed from Sunday to 13 miles per hour.
"First of all it's important to get the notion across to the team that they can't worry or assume anything", Hokies coach Justin Fuente said.
"The bottom line is that there is increasing confidence that Florence will be a large and extremely unsafe hurricane, regardless of its exact intensity", he said.
As has been previously announced, the USC campus is closed beginning Tuesday and until further notice per South Carolina Governor Henry McMaster's order.