ADCIRC predicts Florence's winds will cause 9 to 13 feet of storm surge in some areas along the North Carolina coast.
North Carolina Governor Roy Cooper told a news conference, that a "historic storm" would unleash rains and floods that would inundate nearly the entire state.
More than 421,000 South Carolinians already have evacuated from the coast, McMaster said.
At least 88,000 people were without power in North Carolina with the brunt of the storm yet to come, according to the state's emergency management agency.
Florence's winds weakened as it drew closer to land, dropping from a peak of 225 kph earlier in the week, and the hurricane was downgraded from a terrifying category four to a two.
"A storm surge warning means there is a danger of life-threatening inundation, from rising water moving inland from the coastline".
The coastal area of SC features hundreds of inlets while North Carolina has barrier islands miles away from the mainland. "He is the only caregiver to me and my son", Browning said.
USA television networks said 7pm to 7am curfews had been put in place in several towns surrounding Myrtle Beach. The forecasters say the slow speed will give Florence time to pound the Carolinas with bands of heavy rain.
He said hurricane-force winds extend outward 80 miles from the center of the storm and tropical storm-force winds extend almost 200 miles out.
Preceded first by the storm surge and the winds, heavy rains were picking up as of late Thursday afternoon, the beginning of an onslaught that for some areas may not relent for days. A storm surge warning is in effect for South Santee River South Carolina to Duck North Carolina.
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.
"Your time is running out", he said.
He says he's been through his share of hurricanes.
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Airlines have cancelled more than 1,500 flights, and coastal towns across the Carolinas are largely empty after 1.7 million people in three states were told to clear out.
In Virginia, where about 245,000 residents were ordered to evacuate low-lying areas, officials urged people to remain away from home despite forecast changes showing Florence's path largely missing the state.
A state of emergency has been declared in five coastal states - North Carolina, South Carolina, Georgia, Maryland and Virginia.
Duke Energy said the hurricane could knock out electricity to three-quarters of its 4 million customers in the Carolinas, and outages could last for weeks.
"We call them disasters because they break things", said FEMA's Long.
"We were going to have Chick-fil-A delivered to the airplane after the game but have sent instructions that those meals be distributed wherever it could do the most good".
"In hurricane season, storm surge can have a devastating impact to peoples lives - roughly half of all deaths in tropical cyclones are from storm surge", Potts said. "I'm not leaving him here". "We're ready and God will watch over us".
"I'm not going to lie: I'm scared", she said. "I learned from the past to keep the ice in the washing machine".
"Either no (hotel) rooms are available, or we are denied because the breed or size of dogs", she said. "Have some pity on us because if you stay here and you have a problem and we have to get out in it, there's a chance that we won't because we can't".