The slow-moving storm, the most severe hurricane to threaten the USA mainland this year, was located about 785 miles (1,260 km) southeast of Cape Fear, North Carolina, at 4:30 p.m. EDT (2030 GMT), according to the NHC. The National Hurricane Center is predicting central OH could eventually see between 1 and 2 inches of rain from the massive system.
More than a million and a half people have been ordered to evacuate the coastal areas in the Carolinas and Virginia. The storm will likely dump between 20 and 30 inches (50 to 76 centimeters) of rain over its track, causing serious flooding. Tens of thousands of people are also expected to seek higher ground along coastal areas of North Carolina.
South Carolina Gov. Henry McMaster said an estimated 1 million people would be fleeing his state's coast, with eastbound Interstate 26 heading into Charleston and US 501 heading into Myrtle Beach reversed to ease the exodus. Watches were in effect Tuesday for a storm surge that could reach up to 12 feet at high tide on a stretch from Cape Fear to Cape Lookout in North Carolina, forecasters said. That prediction shows Florence stalling out and looping over or near the North Carolina coastline, which would bring tremendous amounts of rain and potential flooding.
Liz Browning Fox was planning to ride out the storm nevertheless on the Outer Banks. "Don't bet your life on riding out a monster", he said.
Forecast models have said that several feet of heavy rain could cause flooding well inland from the coast.
People buy supplies at Home Depot ahead of Hurricane Florence's landfall. To speed evacuations, officials in SC reversed the flow of traffic on some highways so that all major roads led away from the coast. "Everyone was sold out", she said.
Hurricane-force winds (74 to 95 mph) are now extending out up to 60 miles from the center of the storm, and tropical-storm-force winds are being felt as much as 175 miles around the storm. North Carolina has only been hit by one other Category 4 storm since record keeping began in the 1850s - Hurricane Hazel in 1954, which took 19 lives. Tropical storm-force winds would extend almost 300 miles across three states.
One trusted computer model, the European simulation, predicted more than 45in in parts of North Carolina.
The storm's first effects were already apparent on barrier islands as unsafe rip currents hit beaches and seawater flowed over a state highway.
Craig Fugate, a former Fema director, said: "I'm afraid, based on my experience at Fema, that the public is probably not as prepared as everybody would like".
Florence's path has it slowing and spinning just off the coast of North Carolina.
As for what this region could see from the storm, Cantore said it is still hard to pin down exactly what to expect. One power station, Duke Energy Corp's Brunswick plant, the closest to the area where landfall is forecast, faced a likely shutdown as a precaution. If this chimney hits wind shear and gets knocked out of its vertical orientation, the hurricane has a tough time fueling itself, and it's unlikely to intensify.
The American Red Cross said more than 700 workers were headed to the region while shelters had been set up for those unable to flee. A hospital in Hampton, Virginia, was transferring patients to safer places.