The State of Emergency will help the state coordinate storm response and prepare for any additional impacts.
Another inch of rain is forecasted, before weather systems begin returning to normal Friday.
Evacuations were ordered below the Lake Tahoma Dam in McDowell County.
Local officials said a "class 1 emergency" would be in effect until state inspectors could evaluate the dam in daylight hours.
She said emergency personnel were notifying people who are camping around Lake James, and going door to door warning those about the potential situation.
A mandatory evacuation order has been lifted for parts of McDowell County after concerns about how the weather would affect a dam in the area. We need the public to be a partner with us and do not go around barriers.
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Interstate 40 is closed near Old Fort. Highway 70 at Old Fort is also closed. A flash flood watch for western North Carolina has been extended to early Friday morning.
Elsewhere, four North Carolina dams being closely watched by a state team of special engineers were holding up, Gov. Roy Cooper said Wednesday.
Subtropical storm Alberto rolled ashore Monday afternoon in the Florida Panhandle and then weakened overnight to a depression.
While the storm had weakened by Thursday, it was still dumping rain across large swathes of the country, according to CNN meteorologists. "This is the most significant flooding McDowell County has seen since 2004".
Emergency responders also were conducting several water rescues through McDowell County but no injuries or fatalities were reported, the agency said.
At least five mudslides were reported in Henderson County blocking roads near the towns of Bat Cave and Hendersonville. Asheville, North Carolina, which usually picks up 3.66 inches of rain during May, has received 13.26 inches as of Tuesday, May 29. They include Lake Lure and Chimney Rock Village. "Residents living along the river and in other low-lying areas or areas prone to landslides are urged to take higher ground immediately".
In Virginia, flash flooding blamed on Alberto turned a peaceful creek into a roaring death trap as witnesses reported a man and woman were swept away when their vehicle was washed off a road Wednesday night.