The projected path shows the storm moving from near Wilmington, North Carolina to near Columbia, South Carolina.
The storm's arrival brought a 105 miles per hour wind gust at the NWS office about 7 a.m. Friday, said meteorologist Jordan Baker.
Will Epperson, a 36-year-old golf course assistant superintendent, said he and his wife had planned to ride out the storm at their home in Hampstead, North Carolina, but then reconsidered.
Forecasters say "it can not be emphasized enough that the most serious hazard associated with slow-moving Florence is extremely heavy rainfall, which will cause disastrous flooding that will be spreading inland".
Once a Category-4 hurricane with winds of 225kph, the hurricane was downgraded to Category 1 on Thursday night.
On the morning of September 14, the National Hurricane Centre warned that "catastrophic" flooding and "life-threatening" storm surges were expected to spread inland.More news: Manafort Agrees to Plead Guilty to Avoid New Washington Trial
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At 5 a.m., the center was all but parked over SC, about 35 miles (55 kilometers) west of Myrtle Beach, moving west-southwest at just 5 mph (8 kph) and scooping massive amounts of moisture from the sea. Its forward movement was 6 miles per hour (9 kph).
At 2 p.m. EDT, Florence, weakening as it moves inland at 5 mph, was 35 miles west-southwest of Wilmington and 35 miles east northeast of Myrtle Beach, South Carolina, packing sustained hurricane-force winds of 75 mph, the National Hurricane Center said.
Authorities in New Bern, a town of about 30,000 people that dates to the early 18th century, said more than 100 people had to be saved from floods and that the downtown area was underwater.
Nearly 20,000 people had taken refuge in 157 emergency shelters, Mr Cooper said. More than 60 people had to be rescued in another town as a cinderblock motel collapsed at the height of the storm's fury.
North Carolina alone is forecast to get 9.6 trillion gallons (36 trillion liters), enough to cover the Tar Heel state to a depth of about 10 inches (25 centimeters). "I've never seen the water as high as it came".
"WE ARE COMING TO GET YOU", New Bern city officials said on Twitter. City spokeswoman Colleen Roberts tells WRAL-TV that 200 people have already been rescued. "Persons located within these areas should take all necessary actions to protect life and property from rising water and the potential for other unsafe conditions", the hurricane center briefing said. Roberts says the storm surge continues to increase as Florence passes over the area.
Warning the 10 million residents of America's Southeastern coast about Hurricane Florence, US President Donald Trump has said, "Don't play games with it".
The hurricane center's best guess was that Florence's eye would blow ashore as early as Friday afternoon around the North Carolina-South Carolina line.