Heavy rains will continue to fall in the Carolinas and heavier rains are expected to spread into western parts of North Carolina, in addition to some parts of eastern Tennessee and eastern Georgia, Doll said.
More than 1 million people, mainly in North Carolina, were without power a day after Florence made landfall a few miles east of Wilmington as a howling Category 1 hurricane.
The program was used in North Carolina after Hurricane Matthew in October 2016.
On Saturday some residents tried to return home, driving through flooded highways armed with chainsaws to clear fallen pine trees that covered the road. The great danger now, experts say, is river flooding.
In a separate briefing, Steve Goldstein of the National Oceanic and Atmospheric Administration (NOAA) said some areas have already received two feet of rain and could expect up to 20 inches more as the system moved "slowly, almost stationary" over eastern North Carolina.
A man sits on a park bench in a flooded park as the Cape Fear River rises above its usual height in Wilmington, North Carolina, on September 15, 2018.
In all, hundreds of people have been rescued in New Bern, according to Gov. Roy Cooper.
"This is one of the most devastating hurricanes we've ever had", Mayor Dana Outlaw told CNN.
Duke spokeswoman Paige Sheehan said about 2,000 cubic yards (1,530 cubic meters) of ash were displaced at the L. V. Sutton Power Station outside Wilmington and that contaminated runoff likely flowed into the plant's cooling pond.
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"The cost to SC, if that happens, if the storm continues the way it is going, could be in the billions", Dahler said.
SC recorded its first death from the storm, with officials saying a 61-year-old woman was killed when her vehicle hit a tree that had fallen across a highway.
"You evacuate from water", Cline said.
Charley English of the American Red Cross said anyone wondering how to help from afar can donate blood, registering first at their local Red Cross websites.
Authorities also confirmed a 78-year-old man's body was found outside by family after being electrocuted while trying to connect extension cords in the rain.
Florence had weakened to a Category 1 storm with 90 miles per hour (145 kph) winds by the time it arrived at the North Carolina coastline.
Munich Re's Rauch said about 30 to 50 percent of storm damage is usually insured in the United States but often less than 10 percent in developing countries, meaning nine-tenths of the people hit will end up shouldering a bigger economic burden.
The White House said President Donald Trump approved making federal funding available in some affected counties.
Ex-hurricane Florence's top sustained winds have weakened to 80-kilometres-per-hour but it's projected to bring further catastrophic flash flooding. Disaster response efforts are underway.
Zooming out to the full projection, shown above, the core of the storm is slated to enter North Carolina around 2 p.m. ET on Sunday.