The now Category 1 storm's intensity diminished as it neared land, with winds dropping to 90 miles per hour (135 kph) by nightfall.
"The first bands are upon us", Gov. Roy Cooper said Thursday evening. O'Shaughnessy, head of US Northern Command, said search and rescue would be a top priority, but weather may prevent rescuers from getting in during the hours immediately after the storm hits. "Surviving this storm will be a test of endurance, teamwork, common sense and patience".
Cooper requested additional federal disaster assistance in anticipation of what his office called "historic major damage" across the state. Another 400 people were in shelters in Virginia, where forecasts were less dire.More news: Dairy consumption linked to lower rates of cardiovascular disease
The center of Florence will move over the southwestern Atlantic Ocean between Bermuda and the Bahamas Wednesday night, and approach the coast of North Carolina or SC in the hurricane warning area on Thursday and Friday, NHC said.
The National Hurricane Center warned the threat of tornadoes was increasing as Florence neared shore and South Carolina Governor Henry McMaster said the heavy rains could trigger landslides in the western part of his state. The homes of about 10 million were under watches or warnings for the hurricane or tropical storm conditions.
Roads and intersections on North Carolina's Outer Banks barrier islands were already inundated with water.
Coastal towns in the Carolinas were largely empty, and schools and businesses closed as far south as Georgia.More news: Pope Francis Summons Bishops for Sex Abuse Summit
And in Wilmington, North Carolina, a steady rain began to fall as gusts of winds intensified, causing trees to sway and stoplights to flicker.
A buoy off the North Carolina coast recorded waves almost 30 feet (9 meters) high as Florence churned toward shore.
Life-threatening storm surges of up to 13 feet (4m) have been forecast in some areas when the monster storm eventually makes landfall in North and SC. "Ever stared down the gaping eye of a category 4 hurricane?"More news: The Project: Harper Nielsen On Why She Won't Stand For The Anthem
The National Hurricane Center forecasts that it could be centered over southwestern Pennsylvania by early Tuesday morning, potentially bringing more rain to Maryland and another surge of floodwaters down an already swollen Susquehanna River. After criticism for its response in Puerto Rico to last year's Hurricane Maria, which officials there said was responsible for 3,000 deaths, Trump has vowed a vigorous response to Florence and defended his handling of Maria.