"You can still get a push of water 50 miles away. It's not just on the coast with the storm surge," NHC Director Ken Graham said on a livestream. "50 percent of the fatalities in these tropical systems is the storm surge."

"Although slow weakening is expected to begin by late Thursday, Florence is still forecast to be an extremely dangerous major hurricane when it nears the U.S. coast late Thursday and Friday," the NHC said in a press release. The NHC has forecast storm surges as high as 13 feet in some areas, while scientists estimate up to 20 feet – bringing with it catastrophic floods. The latest forecasting models show the storm stalling along the coast before moving south slightly, combining a severe surge with heavy rains.

Hurricane Florence is closing in on the coast of the Carolinas, with officials expecting the storm to make a direct hit by early Friday. The hurricane weakened on Wednesday to a Category 3 storm with winds of 120 mph. Earlier, Florence was on track to become the first Category 4 storm to directly hit North Carolina in 60 years. The National Hurricane Center (NHC) warned that although Florence's peak winds have decreased slightly, the size of its wind field has increased. The storm is still expected to hit portions of the Carolinas with life-threatening storm surge and rainfall, according to the NHC.

Source: NOAA GOES-East satellite on Wednesday morning.

More than 1½ million people have been ordered to evacuate their homes along the coast as government officials in Georgia, North Carolina, South Carolina, Virginia, Maryland and Washington, D.C. declared states of emergency. Florence weakened slightly to a Category 3 about 385 miles southeast of Wilmington, North Carolina as of 5 p.m. ET Wednesday, the NHC said. The storm has maximum sustained winds of 120 miles per hour.

"About 170 miles out from the center you can get some of these high tropical storm force winds," Graham said.

Florence is expected "to be an extremely dangerous major hurricane when it nears the U.S. coast," the National Hurricane Center said.

Duke Energy said that Florence could cause as many as 1 million to 3 million power outages out of its 4 million customers in the Carolinas.

@Astro_Alex: Ever stared down the gaping eye of a category 4 hurricane? It's chilling, even from space. #HurricaneFlorence #Horizons https://flic.kr/s/aHsmsk7Krv

The Center expects Florence to produce between 20 to 40 inches of total rainfall across portions of North Carolina, Virginia and South Carolina until Saturday. Florence may also create "life-threatening flash flooding" and "damaging hurricane-force winds" the Center said.

"It's not just coastal here," Graham said, adding that these are "catastrophic rainfall" levels expected.

Florence is generating waves as high as 83 feet, the Center said.

@NHC_TAFB: Wave heights to 83 ft were measured early this morning under the NE quadrant of Hurricane Florence. These enormous waves are produced by being trapped along with very strong winds moving in the same direction the storm's motion.

The National Hurricane Center has issued a storm surge warning from the South Santee River in South Carolina to Duck, North Carolina. Coastal areas may see waters surge by as much as 13 feet or more above ground if Florence's peak surge coincides with a high tide.

"A life-threatening storm surge is now highly likely along portions of the coastlines of South Carolina and North Carolina," the Center said.

@NHC_Atlantic: 5 PM EDT Sept. 12: Here are the Key Messages for Hurricane #Florence.

Several companies are already taking steps to prepare for the storm. BMW is working to load vehicles at its Spartanburg, South Carolina plant on ships headed out to sea to avoid Florence's path. Boeing will suspend operations at its Charleston, South Carolina location with 6,700 employees "so our employees can properly evacuate," the company said.

Lowe's has already shipped 800 truckloads of products to about 100 stores that will be affected by the hurricane, VP of Store Operations Jennifer Thayer told CNBC. The company also closed its coastal stores on Tuesday to allow employees to evacuate.

Airbnb launched a portal on its site Wednesday that displays hosts who have opened their homes for free to relief workers and those displaced by Florence.

@NOAASatellites: Hurricane #Florence looks enormous, even from space. Here are three dramatic views of the storm approaching the East Coast, seen from the #GOESEast satellite this morning. Latest updates: http://go.usa.gov/xPr6g #HurricaneFlorence

JetBlue, Delta and United Airlines have all capped fares and waived change fees ahead of the storm hitting land. Comcast has opened more than 233,000 free Wi-Fi hotspots along the East Coast.

J.P. Morgan estimated Monday that Hurricane Florence could cause the insurance industry to lose between $8 billion and $20 billion, depending on the timing and intensity of the storm when it makes landfall.

"This would make Hurricane Florence one of the top 10 most costly hurricanes to hit the U.S.," J.P. Morgan analyst Sarah DeWitt said in a note.

Florence is currently the most dangerous of three tropical systems being tracked in the Atlantic. Tropical Storm Isaac is expected to pass south of Puerto Rico and Cuba, while Hurricane Helene was moving northward away from land. Forecasters also were tracking two other disturbances.