The National Hurricane Center said in an advisory Thursday night that a storm surge of 10 feet above normal level had already been reported by the National Weather Service office in Morehead City, N.C. Rainfall of up to 40 inches could occur in isolated areas of North and SC.
"A turn toward the west-northwest and west at a slow forward speed is expected through Friday, followed by a slow west-southwestward motion Friday night and Saturday", the NHC said. "There is probably not a county or a person that will not be affected in some way by this very massive and violent storm".
The powerful storm already has inundated coastal streets with ocean water and left tens of thousands without power, and forecasters say that "catastrophic" freshwater flooding is expected over portions of the Carolinas as Hurricane Florence inches closer to the U.S. East Coast.
The National Hurricane Center warned the threat of tornadoes was increasing as Florence neared shore and South Carolina Governor Henry McMaster said the heavy rains could trigger landslides in the western part of his state.
Florence's winds dropped from a peak of 225km/h to 165km/h overnight, reducing the hurricane from a terrifying Category 4 to a 2.
Forecasters' European climate model is predicting 2 trillion to 11 trillion gallons of rain will fall on North Carolina over the next week, according to meteorologist Ryan Maue of weathermodels.com.
Because hurricane force winds extend 130 km from the center, people on land will experience sharply deteriorating conditions long before the center reaches the coast. Here's why this storm threatens not only the coast but millions of people inland.
Florence also blew down trees, including one that went through the roof of Kevin DiLoreto's home in Wilmington. They died when a large tree came down over the back of their home, crushing and killing them while leaving the child's father hospitalized Friday morning.
WXII-TV reported that 150 people were waiting to be rescued from rising waters in the city New Bern.
"It's really risky out right now", Beaufort, NC, Mayor Everette Newton told CNN.
"Inland flooding kills a lot of people, unfortunately, and that's what we're about to see", Long added. "My wife's in a panic right now".
Emergency officials on Wrightsville Beach were able to assess the beginning impacts of Hurricane Florence before day turned to night Thursday. "We just bought a new house so I'm kinda nervous".
About 85,000 county residents are under mandatory evacuation orders, she said. "This is a 500- or 1,000-year event".
Antonio Ramirez, a construction worker from El Salvador living in Leland, North Carolina, said he planned to ride out the worst of the weather with his dog Canelo. The figure for SC was 170,000 customers.
At least 12,000 people had taken refuge in 126 emergency shelters, Cooper said, with more facilities being opened.
Winds and rain were arriving later in SC, and a few people were still walking on the sand at Myrtle Beach while North Carolina was getting pounded.
President Donald Trump is expected to travel to areas hit by Florence next week, once it is determined his travel will not disrupt any rescue or recovery efforts, the White House said on Friday.
With winds picking up along the coastline early Thursday, federal and state officials had issued final appeals to residents to get out of the path of the "once in a lifetime" weather system.