Meanwhile, tragedy struck one family in Wilmington when a tree fell on a house; a mother and a child were killed.
More than 800,000 homes and businesses have lost power and Mr Cooper said the danger from flooding would linger for days.
"It's an uninvited brute who doesn't want to leave", said North Carolina Gov. Roy Cooper.
There is this one shark photo without which hurricanes and floods can not wreak havoc in the US.
The NWS says southern and central portions of North Carolina into far northeast SC are expected to report an additional 10 to 15 inches of rainfall - with storm totals between 30 and 40 inches along the coastal areas south of Cape Hatteras.
In Lenoir County a 78-year-old man was electrocuted while trying to connect extension cords and another man died after being blown away by high winds while checking on his dogs.
Properties within one mile of the river were hastily evacuated on Saturday.
Former congressman and GOP gubernatorial nominee Ron DeSantis - an ardent Trump defender who campaigned with the president during the Republican primary - also said he disagreed with Trump Thursday. It came ashore along a mostly boarded-up, emptied-out stretch of coastline.
Homes and roads have been utterly submerged by the barrage of rain caused by the remnants of hurricane Florence - now a tropical storm. But it was clear that this was really about the water, not the wind.
Florence's forward movement during the day slowed to a near-standstill - sometimes it was going no faster than a human can walk - and that enabled it to pile on the rain. Morehead City, North Carolina, had received 23 inches (58 centimeters) of rain by Friday night with more torrents on the way.
In general, south eastern sections of North Carolina like Wilmington and Fayetteville are at risk of flooding. "This rainfall will continue to produce catastrophic flash flooding and prolonged significant river flooding", the advisory said.
Two fins were spotted in the high water in Wilmington.
"And we're not done yet", Graham said, adding that some hard-hit areas could get an additional 15 to 20 inches because the storm was moving so slowly.
Hurricane Florence was making landfall in North Carolina early Friday pushing a life-threatening storm surge for miles inland with screaming wind that was destroying buildings in its path. That's enough to fill the Chesapeake Bay or cover the entire state of Texas with almost 4 inches (10 centimeters) of water, he calculated.
North Carolina alone is forecast to get 9.6 trillion gallons (36 trillion litres), enough to cover the Tar Heel state to a depth of about 10 inches (25 centimetres). Ocean water flowed between homes and on to streets on the Outer Banks; waves crashed against wooden fishing piers.
A wind gust at the Wilmington airport was clocked at 105 miles per hour (nearly 170 kph), the highest since Hurricane Helene in 1958. Nationwide, airlines cancelled more than 2,400 flights through Sunday.
The Neuse is expected to crest at more than nine feet (3 meters) above flood stage Monday and Sheehan said the company expects the same ash basins are likely to be inundated again. "I think we're OK".
Boat teams including volunteers rescued some 360 residents, including Sadie Marie Holt, 67, who first tried to row out of her neighbourhood during Florence's assault. Though Florence did not arrive with winds as violent as once feared, forecasters got the storm surge and rainfall correct.
"Honestly, I grew up in Wilmington". Her 6-foot-2 husband went to see what he could do, but the water was above his chest, she said.