Hurricane Florence evacuations expand, with 'disaster at doorstep'

* Storm still a major hurricane but weakens to Category 3

* Intense inland flooding expected

* More than 1 million people under evacuation (Adds latest rainfall and storm surge forecasts)

By Ernest Scheyder

WILMINGTON, N.C., Sept 12 (Reuters) - Hurricane Florence, growing in size despite its weakening winds, churned ever closer to the U.S. East Coast on Wednesday as evacuations expanded south from the Carolinas into Georgia to counter the threat of deadly high seas and calamitous floods.

The center of Florence, a slow-moving Category 3 hurricane on the five-step Saffir-Simpson scale, is expected to strike North Carolina late Thursday or early Friday and could drift southwest along the coast before turning inland, according to the National Hurricane Center in Miami.

The storm's maximum sustained winds were clocked at 120 miles per hour (193 km per hour), down from a peak of 140 mph a day earlier before Florence was downgraded from a Category 4.

But the NHC warned that Florence still poses a deadly threat to a wide stretch of the U.S. Eastern Seaboard, from southern Georgia into southern Virginia, and remained capable of unleashing rain-fueled catastrophic flooding of rivers and low-lying areas.

"The time to prepare is almost over," North Carolina Governor Roy Cooper told a morning news conference. "Disaster is at the doorstep and it's coming in."

In addition to inundating the coast with wind-driven storm surges of seawater as high as 9 feet (2.7 meters) along the Carolina coast, Florence could dump 20 to 30 inches (51-76 cm) of rain, with up to 40 inches (1 meter) in parts of North Carolina, the NHC said.

Downpours and flooding would be especially severe, lasting for days, if the storm stalls over land. Heavy rains were forecast to extend into the Appalachians, affecting parts of Alabama, Tennessee, Kentucky and West Virginia.

Tens of thousands of homes and businesses could be flooded in North Carolina alone, Governor Cooper warned.

Georgia Governor Nathan Deal, concerned the storm would bring its devastation south, issued an emergency declaration for all 159 counties in his state. Similar declarations were made earlier in North and South Carolina, Virginia, Maryland and the District of Columbia.

More than 1 million people have been ordered to evacuate the coastlines of the Carolinas and Virginia.

Duke Energy Corp expected between 25 percent and 75 percent of its 4 million customers would lose power in the Carolinas. Spokesman Howard Fowler said restoration could take "weeks instead of days," even though 20,000 workers, including crews from outside the area, were standing by.

The NHC said the first tropical storm-force winds of at least 39 mph (63 kph) would hit the region early on Thursday with the storm's center reaching the coast Friday.

BRACING FOR THE HIT

Emergency preparations in the region included activating 2,800 National Guard troops in North Carolina, stockpiling food, setting up shelters, switching traffic patterns so major roads led away from shore, and securing 16 nuclear power reactors in the Carolinas and Virginia.

Wilmington, North Carolina, just north of where the hurricane is expected to come ashore, was sunny around midday on Wednesday as the town appeared to be emptying.

"I'm not approaching Florence from fear or panic," said Brad Corpening, 35, who planned to ride out the storm in his boarded-up delicatessen in Wilmington. "It's going to happen. We just need to figure out how to make it through."

Officials in New Hanover County, which includes Wilmington, have stockpiled enough food and water for 60,000 people for four days, along with more than 28,000 tarps. 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.

"It's going to be bad," said Woody White, chairman of the New Hanover County Commissioners. "But no matter how bad it's going to be, it will pass and our job will be to rebuild this community together, and that's what we're going to do."

(Reporting by Ernest Scheyder Additional reporting by Scott DiSavino in New York, Brendan O'Brien in Milwaukee and Bernie Woodall in Fort Lauderdale, Florida, Writing by Bill Trott and Steve Gorman; Editing by Bill Tarrant and Lisa Shumaker)