Rainfall also is swelling waterways: Meteorologist Ryan Maue of weathermodels.com calculated that 34 million people in the USA are forecast to get at least 3 inches of rain from Hurricane Florence, with more than 5.7 million people probably getting at least a foot of rain.
Weak steering current will allow the hurricane to drift westward along the SC coast and inland, and center over the state's interior Sunday morning, the NHC projected.
Florence had been a Category 3 hurricane with 120 miles per hour winds on Thursday but dropped to Category 1 before coming ashore. As of Friday morning, Atlantic Beach, a town on the state's Outer Banks barrier islands, already had received 30 inches (76 cm) of rain, the US Geological Service said.
In Hampstead, North Carolina, a woman died of a heart attack on Friday since emergency crews could not reach her due to fallen trees in road, local media reported. "Disaster is at the doorstep and it's coming in".
"Significant weakening is forecast over the weekend and into early next week while Florence moves farther inland", NHC said.
North Carolina Governor Roy Cooper said the hurricane was "wreaking havoc" on the coast and will make its "violent grind across our state for days", calling the storm an event that comes along only once every 1,000 years. Heavy rains were forecast to extend into the Appalachians, affecting parts of Alabama, Tennessee, Kentucky and West Virginia.
More than 415,000 homes and businesses were without power, mostly in North Carolina, according to poweroutage.us, which tracks the nation's electrical grid.
Officials said some 1.7 million people in the Carolinas and Virginia were warned to evacuate, but it is unclear how many did. Utility companies said millions were expected to lose power and restoration could take weeks.
The storm is moving toward the northwest at 17 miles per hour (28 kph), the NHC said.
Their entire neighborhood evacuated in Wilmington, North Carolina, David and Janelle Garrigus planned to ride out Florence at their daughter's one-bedroom apartment in Charlotte. "To those in the storm's path, if you can hear me, please stay sheltered in place". "It's going to happen".
"We're just trying to plan for the future here, not having a house for an extended period of time", David Garrigus said.
Farmers have learned lessons from past storms - most recently the devastating flooding of 2016's Hurricane Matthew, but this storm will rip through the state during what is normally harvest season. Shelters in the city were filling and some people were being bused inland to Raleigh, even though some residents there were told they might have to evacuate because of flooding.
"The sun rose this morning on an extremely risky situation and it's going to get worse", he said at a news conference in Raleigh. "But no matter how bad it's going to be, it will pass and our job will be to rebuild this community together".
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