Hurricane Florence, a large and dangerous Category 2 storm, is about a day away from crashing into the coast of the Carolinas, where conditions will begin to rapidly deteriorate Thursday. It marks the beginning of a prolonged assault from wind and water, which – by the time its over – is likely to bring devastating damage and flooding to millions of people in the Southeast.

Starting along the coast, winds will accelerate, the rain will intensify and the angry, agitated ocean will surge ashore.

Landfall is expected Friday in southeast North Carolina, which may bear the storm’s brunt. The storm’s surge, the rise in seawater above normally dry land at the coast, could rise a story high. On top of that, a disastrous amount of rain, 20 or maybe even as many as 40 inches will fall.

Flooding from both the storm surge and rainfall could be “catastrophic,” the National Hurricane Center warned.

This same zone will be hammered by winds gusting up to hurricane force for nearly a day while tropical-storm conditions could linger twice that long. These unforgiving winds will damage homes and buildings, down trees and knock out power.

Gradually, Friday through the weekend, the massive storm – containing a zone of tropical-storm-force winds nearly 400 miles wide – will drift inland, engulfing much of South Carolina and southern North Carolina. Widespread rainfall amounts could reach 6 to 12 inches, spurring flooding. Some of the storm’s wind and rain could even creep into eastern Georgia.

Enough rain could fall to break North Carolina’s record for a tropical storm – 24 inches – set near Wilmington during Hurricane Floyd in 1999, said Greg Carbin, chief of forecast operations at the Weather Service’s national prediction center.

Flooding from heavy rains is the second-leading cause of fatalities in tropical storms and hurricanes that make landfall.

The rain threat may not stop in the Carolinas. By early next week, a weakened but soggy Florence may drop rain on already saturated Virginia, West Virginia , Maryland, Washington and Pennsylvania. These areas are vulnerable to flooding and downed trees after heavy rains this summer.

“North Carolina, my message is clear,” a grim Gov. Roy Cooper said at a briefing Wednesday. “Disaster is at the doorstep and is coming in.”

The pivot in the forecast track of Florence led Georgia’s governor to declare a state of emergency Wednesday afternoon for all 159 counties, home to 10.5 million people.

Federal officials warned that the millions of people in Florence’s sights could be without electricity for weeks, if high winds down power lines and massive rainfall floods equipment. There are 16 nuclear reactors in the region, and crews at the one closest to where landfall is forecast readied the station, at Brunswick, for a shutdown.

The monstrous storm has forced the closing of hundreds of schools throughout the region.

President Donald Trump has approved emergency disaster declarations for the Carolinas and Virginia, which frees up funds for relief and recovery. “We’re as ready as anybody has ever been,” he said after a briefing with Federal Emergency Management Agency Administrator William “Brock” Long and Homeland Security Secretary Kirstjen Nielsen.

“Florence could be the most dangerous storm in the history of the Carolinas,” Long, a North Carolina native, tweeted Tuesday.

As of 5 a.m. Thursday, Florence’s top winds were 110 mph, and it was barreling northwest at 15 mph, about 205 miles east-southeast of Wilmington, North Carolina, and 250 miles east-southeast of Myrtle Beach, South Carolina.

The Hurricane Center predicts the storm to maintain this intensity until landfall, after which wind speeds will steadily decline.

Even as Florence’s peak winds decreased Wednesday, the storm’s wind field grew, the Hurricane Center said. Hurricane-force winds extend 80 miles from the center, while tropical-storm-force winds extend 195 miles outward. The storm’s cloud field is about the size of four Ohios.

Hurricane warnings are in effect for the South Santee River in South Carolina to Duck, North Carolina, and Albemarle and Pamlico sounds. This includes Wilmington. Hurricane watches extend north to the North Carolina-Virginia border and south to the South Santee River, including the Charleston area. A tropical storm warning covers the area from north of Duck to the North Carolina-Virginia border.

More than 10 million people are under watches and warnings, the Associated Press reported.

Like a bulldozer, the storm’s winds and forward motion will push a tremendous amount of water onshore when it makes landfall. The storm surge could reach up to more than a story high, or 13 feet, if the maximum surge coincides with high tide.

The biggest surge should occur just to the north of where the eye of the storm comes ashore, which the Hurricane Center projects in southeastern North Carolina.

The surge will result in “large areas of deep inundation . . . enhanced by battering waves,” the Weather Service said. It warned of likely “structural damage to buildings . . . with several potentially washing away,” “flooded or washed-out coastal roads” and “major damage to marinas.”

Storm surge warnings were issued from South Santee River in South Carolina to Duck. The Charleston area is under a storm surge watch.

The Hurricane Center projects the following surge heights above normally dry land, if the maximum surge coincides with high tide:

• Cape Fear to Cape Lookout, including the Neuse, Pamlico, Pungo and Bay Rivers: 9 to 13 feet;
• North Myrtle Beach to Cape Fear: 6 to 9 feet;
• Cape Lookout to Ocracoke Inlet: 6 to 9 feet;
• South Santee River to North Myrtle Beach: 4 to 6 feet;
• Ocracoke Inlet to Salvo, N.C.: 4 to 6 feet;
• Salvo to North Carolina/Virginia Border: 2 to 4 feet; and
• Edisto Beach to South Santee River: 2 to 4 feet.

Models agree that excessive amounts of rain will fall in southeastern North Carolina.

“Floodwaters may enter numerous structures, and some may become uninhabitable or washed away,” the Weather Service warned.

Where exactly the zone of heaviest rain sets up as the storm meanders inland is more uncertain, but models suggest that it may concentrate in southern North Carolina and northern South Carolina through the weekend.

It has become likely that the storm will reverse course early next week and turn back north toward West Virginia, Virginia, Maryland and Pennsylvania, albeit significantly weakened.

The Hurricane Center forecasts the following rain amounts:

• Coastal North Carolina: 20 to 30 inches, isolated 40 inches.
• South Carolina, western and northern North Carolina: 5 to 10 inches, isolated 20 inches.
• Elsewhere in the Appalachians and Mid-Atlantic states: 3 to 6 inches, isolated 12 inches. Much of this rain would fall early next week, rather than over the weekend.

The strongest winds will occur where and when the storm makes landfall in a ring around the calm eye of the storm known as the eyewall. If the storm makes landfall as a Category 2, these winds will be damaging, sustained at up to 100 mph or so with higher gusts.

The zone where these intense winds occur will be narrow and they will last just a few hours, but the effects will probably be severe, similar to a tornado. The Hurricane Center describes the types of damage associated with Category 2 winds:

Well-constructed frame homes could sustain major roof and siding damage. Many shallowly rooted trees will be snapped or uprooted and block numerous roads. Near-total power loss is expected with outages that could last from several days to weeks.

Outside this zone of destructive winds, damaging winds are still likely, even some distance inland from the coast, which would lead to minor structural damage, downed trees and widespread power outages.

A power outage model run at the University of Michigan projects that 3.2 million customers will be without electricity because of the storm, mostly in the eastern half of North Carolina.

Because the storm will slow it moves over the eastern Carolinas, these wind impacts will be magnified.

While it is extremely likely that the eastern Carolinas will be hardest hit by the storm Thursday into Friday, the storm’s direction becomes far less certain over the weekend and next week.

Models agree the storm should strike land between the North Carolina-South Carolina border and the North Carolina Outer Banks, and then track across South Carolina. But then they gradually diverge. While all simulations show the storm turning back to the north Sunday or Monday, exactly where that turns occurs is a big wild card.

The storm could track north through the Ohio Valley, the Appalachians or even closer to the Interstate 95 corridor. The specifics of the track early next week will have implications for where the heaviest rainfall occurs north of the Carolinas.

The Washington Post’s Joel Achenbach and Ann Gerhart contributed to this report.

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