In a display of the early effects of the storm, one flood gauge on the Neuse River in New Bern, North Carolina, showed 10 feet (three meters) of flooding, the NHC said.
More than 60 people had to be pulled from a collapsing motel at the height of the storm, and many more who defied evacuation orders held out hope of being rescued.
Florence flattened trees, crumbled roads and the assault wasn't anywhere close to being over, with the siege in the Carolinas expected to last all weekend.
"More on the way to help us".
"This storm will bring destruction", North Carolina Governor Roy Cooper said. "We might leave", she said.
Forecasters said conditions will deteriorate as the storm pushes ashore early Friday near the North Carolina-South Carolina line and makes its way slowly inland.
The dead included a mother and baby who were killed when a tree fell on their home in Wilmington, North Carolina. The city tweeted early Friday that 150 people were awaiting rescue.
"I feel like the dumbest human being who ever walked the face of the earth", he said.
Florence, a strong Category 1 storm with maximum sustained winds of 90 miles per hour, is causing life-threatening storm surges and pounding the coast with hurricane-force winds, the advisory said. It came ashore along a mostly boarded-up, emptied-out stretch of coastline. Hurricane-force winds extended 80 miles (130 kilometers) from its center, and tropical-storm-force winds reached out 195 miles (315 kilometers).
But it was clear that this was really about the water, not the wind.
After landfall, Florence slowed to a pace that meant it would plague the area with days of flooding.More news: USA businesses to lobby against Trump's tariffs
Storm clouds are seen over the 2nd ave pier as the force of Hurricane Florence is beginning to be felt on September 14, 2018 in Myrtle Beach, United States.
Storm chaser Jeff Piotrowski posted photos of downed trees in Wrightsville Beach and a toppled gas station awning in Wilmington. This is expected to cause "catastrophic flash flooding and prolonged significant river flooding".
Preparing for the worst, about 9,700 National Guard troops and civilians were deployed with high-water vehicles, helicopters and boats that could be used to pluck people from the floodwaters.
Florence was seen as a major test for FEMA, which was heavily criticized as slow and unprepared past year for Hurricane Maria in Puerto Rico, where the storm was blamed for almost 3,000 deaths in the desperate months that followed.
The tropical cyclone is expected to unload 10 trillion gallons of rainfall in North Carolina, weather.us meteorologist Ryan Maue said. Pieces of torn-apart buildings flew through the air. It was crawling west-southwest at 3 miles per hour, lifting huge amounts of ocean moisture and dumping it far from the coast. Airlines canceled more than 2,400 flights through Sunday.
The powerful Atlantic storm began battering the Carolinas with rain, wind and floodwater.
In New Bern, North Carolina, the storm surge overwhelmed the town of 30,000 which is located at the confluence of the Neuse and Trent rivers.
"We're on our way, we will get you rescued", Outlaw said while cautioning that first responders have to be careful of their own safety.
A friend later tweeted that the woman and her family had been rescued.
"The wind was so hard, the waters were so hard, that trying to get out we got thrown into trailers". Ballance called the rainfall "biblical", saying he's gotten reports from friends that his downtown seafood restaurant was flooded, just like the rest of the small city's historic downtown, and he's anxious about the hundreds of people who needed to be rescued overnight in the city.
People have left homes and taken precautions ahead of the hurricane.