Hurricane Florence was moving at a slower speed of 5 mph with “life-threatening storm surge and rainfall” forecasted, officials said.
Gusty winds were pummeling the southeastern coast by Thursday evening, as a tattered American flag was seen flying feverishly on a live surf camera at Frying Pan Tower in North Carolina.
"Hurricane-force winds" had begun hitting the state's coast, the National Hurricane Center (NHC) said in an 8 p.m. update.
The storm is currently situated roughly 85 miles east-southeast of Wilmington, North Carolina and about 145 miles east of Myrtle Beach, South Carolina, the NHC said.
Florence is moving northwest at 5 mph with maximum sustained winds of 100 mph, the update said.
A sign at the Harbour View Inn in Chareston, South Carolina. (AP Photo/Mic Smith)
"On the forecast track, the center of Florence will approach the coasts of North and South Carolina later tonight, then move near or over the coast of southern North Carolina and northeastern South Carolina in the hurricane warning area on Friday," the update said. "A slow motion across portions of eastern and central South Carolina is forecast Friday night through Saturday night."
The storm, listed as a Category 2, is likely to bring significant rain to the Carolinas, where some places could see upwards of 20 inches, the update said. This is expected to cause "catastrophic flash flooding and prolonged significant river flooding."
The agency said a mix of storm surge and tides could result in flooding from rising water levels. Cape Fear to Cape Lookout, North Carolina could see as much as 7 to 11 feet of water, according to the update.
Waves slam the Oceana Pier & Pier House Restaurant in Atlantic Beach, North Carolina on Thursday as Hurricane Florence approaches the area. (Travis Long/The News & Observer via AP)
Storm surge and hurricane warnings were in effect for South Santee River, South Carolina through to Duck, North Carolina, as well as Albemarle and Pamlico Sounds in North Carolina, the agency said.
Areas from Edisto Beach to South Santee River in South Carolina were under both a storm surge and hurricane watch, while areas located north of Duck, North Carolina to the state's border with Virginia were under a storm surge watch, according to the update.
Hurricane Florence is forecast to progressively weaken after it's center "meanders near the coast" or moves inland, the update said.
7,000 troops are prepared to deploy in response to Hurricane Florence, Air Force Gen. Terrence J. O'Shaughnessy said during a Pentagon briefing Thursday. The troops have "surrounded" what are expected to be affected areas and are ready to deploy "as soon as request is made," he said.
Dunleavy's Pub on Sullivan's Island, South Carolina wrote "open" on their boarded up windows. (AP Photo/Mic Smith)
The storm's size and sluggish track could cause significant damage in the area, forecasters predicted.
"It truly is really about the whole size of this storm," National Hurricane Center Director Ken Graham said. "The larger and the slower the storm is, the greater the threat and the impact — and we have that."
The hurricane was seen as a major test for the Federal Emergency Management Agency, which was heavily criticized as sluggish and unprepared for Hurricane Maria in Puerto Rico last year.
As Florence drew near, President Donald Trump tweeted that FEMA and first responders are "supplied and ready," and he disputed the official conclusion that nearly 3,000 people died in Puerto Rico, claiming the figure was a Democratic plot to make him look bad.
Schools and businesses as far south as Georgia were closed, about 1,200 flights and counting were canceled, and coastal towns in the Carolinas were largely emptied out.
Fox News' Lucas Tomlinson, Zoe Szathmary and The Associated Press contributed to this report.