Storm surge, the rise in seawater above normally dry land at the coast, could rise a story high.
Because hurricane force winds extend 130 kilometers from the center, people on land will experience sharply deteriorating conditions long before the center reaches the coast.
By the time the storm leaves the region, forecasters expect that it will have dumped 50 to 70 centimeters of rain in coastal areas, with some parts possibly being inundated with up to 100 centimeters. The trend is "exceptionally bad news", said University of Miami hurricane researcher Brian McNoldy, since it "smears a landfall out over hundreds of miles of coastline, most notably the storm surge".
The center of Florence is expected to hit North Carolina's southern coast around midnight (0400 GMT) on Friday, then drift southwest before moving inland on Saturday, enough time to drop as much as 40 inches (1 meter) of rain in places, according to the National Hurricane Center. And disruptive, risky winds regardless of official category.
At a press conference Thursday morning, officials stressed that Hurricane Florence's wind speed may have fallen, but the danger has not.
Workers prepare a house with storm shutters ahead of the arrival of Hurricane Florence in Ocean Isle Beach, North Carolina, U.S. September 12, 2018. The problem is, Flo is now expected to stall out over the Carolinas before slowly moving inland.
Even if Florence were downgraded to a Category 1 hurricane, it would still cause extensive damage, Abrams says.
If you want to know more specific information about your area, head to the National Weather Service's social media page, where you can enter your zip code and find your local forecast office.
Of those who left, more than 4,000 had sought housing at emergency shelters across the state.
Like a bulldozer, the storm's winds and forward motion will push a tremendous amount of water onshore when it makes landfall. That storm killed at least 10 people in SC and in Georgia.
The biggest surge should occur just to the north of where the eye of the storm comes ashore, which the Hurricane Center projects in southeastern North Carolina.
Masters said there's a tug-of-war between two clear-skies high-pressure systems - one off the coast and one over MI.
Hurricane Hazel struck the North and SC border area 64 years ago in 1954. The Charleston area is under a storm surge watch.
For the Columbia area, state and city officials warn of flooding and the likelihood of flash flooding.
President Donald Trump has declared states of emergency for North and SC and Virginia, and 1.7 million people have been warned to leave.
It has become likely that the storm will reverse course early next week and turn back north toward West Virginia, Virginia, Maryland and Pennsylvania, albeit significantly weakened. I had to make sure today was Thursday because all of the days seem to run together.
The scale includes five categories and is based on the storm's sustained wind speeds.
The zone where these intense winds occur will be narrow and they will last just a few hours, but the effects will probably be severe, similar to a tornado.
"Catastrophic damage will occur: A high percentage of framed homes will be destroyed, with total roof failure and wall collapse". Many shallowly rooted trees will be snapped or uprooted and block numerous roads.
The company said as many as three-fourths of its 4 million customers in North Carolina and SC could lose power. "I think Florence is going to take all of them out".
It's incredibly hard to pin down a storm's precise death toll because of the myriad, chaotic factors that accompany a natural disaster.