Hurricane Florence, a Category 4 storm that could become the most catastrophic to hit the Carolinas in decades, might become a Category 5 briefly before it makes landfall.
The National Hurricane Center has issued hurricane and storm surge watches for parts of South Carolina and North Carolina, where the storm is expected to make landfall as early as Thursday and as late as Friday.
The storm was becoming better organized and increasing in size Tuesday afternoon as evacuations are underway in three states.
Parts of South Carolina, North Carolina and Virginia have been ordered to evacuate. In the latest NHC update, a tropical storm watch was issued for many coastal areas in Virginia, and hurricane warnings were issued for many South and North Carolina rivers.
The storm still has sustaining winds of 140 mph, Channel 2 Action News reported. Florence could become a Category 5 storm sometime Wednesday, according to the news station.
Additional watches could go into effect as the storm’s path becomes clear.
Four states — South Carolina, North Carolina, Virginia and Maryland — have declared states of emergency.
South Carolina Gov. Henry McMaster issued a mandatory evacuation for several coastal counties: Charleston, Berkeley, Dorchester, Georgetown and Horry. With the exception of Edisto Beach, evacuation orders for Beaufort, Colleton and Jasper counties were lifted.
RELATED: Hurricane Florence: Atlanta shelter takes in South Carolina dogs, cats
McMaster predicted more than 1 million South Carolina residents will flee the path of the storm, and I-26 reversed Tuesday at noon to flow all traffic away from the coast.
North Carolina has been hit by only one other Category 4 storm since reliable record-keeping began in the 1850s. That was Hurricane Hazel in 1954, which destroyed 15,000 buildings and killed 19 people.
MORE: Florence may miss Georgia, but residents aren’t taking chances
Atlanta Motor Speedway is opening campgrounds to Florence evacuees, according to a post on the Henry County facility’s official Twitter account.
And Georgia Department of Transportation spokeswoman Natalie Dale said the agency is increasing the number of responding CHAMP operators on I-20, I-95 and I-16 to prepare for heavy traffic. CHAMP units provide highway assistance, clear debris and help at accident scenes.
ALSO: Georgia DOT prepares for Hurricane Florence
Georgia Gov. Nathan Deal has not issued a state of emergency, but his chief of staff, Chris Riley, told AJC.com that the Georgia Emergency Management Agency began tracking and monitoring the storm Monday.
RELATED: A look at some of Georgia's worst hurricanes
Here’s what you need to know to prepare for the storm’s impact.
When and where should Florence make landfall?
The latest models have the center of Florence hitting the Wilmington, N.C., area early Friday morning, Channel 2 meteorologist Karen Minton said.
MORE: Where is Florence now?
“The earliest reasonable time that tropical storm-force winds could arrive in the United States from Florence is late Wednesday, and the most likely time is Thursday morning,” the Hurricane Center said. “Wednesday should be the last full day to prepare, so plan accordingly.”
Conditions along the South Carolina-North Carolina coast will rapidly deteriorate starting late Wednesday, Channel 2 meteorologist Brian Monahan said.
The path of the storm should avoid Georgia, but Minton said some models show the eastern part of the state getting some moisture when Florence hits the East Coast. For the most part, Georgia should benefit from sinking air on the backside of the system that will help to drive rain chances down.
ALSO: Delta caps fares for flights from cities in path of Florence
Hurricane and storm surge watches are in effect from Edisto Beach north to the North Carolina-Virginia border, including the Pamlico and Albemarle sounds.
That means there is a possibility of hurricane conditions and life-threatening surges from rising water moving inland from the coastline over the next 48 hours, according to the Hurricane Center. A watch is typically issued 48 hours before tropical storm-force winds are expected.
“This is going to send enormous waves, beach erosion, rip currents all along the East Coast,” Monahan said. “This will come in along the Carolinas, but the impacts are going to be wide-reaching all along the East Coast.”
How strong should Florence be?
Florence has been classified a Category 4 storm since Monday afternoon. Sustained winds have reached 140 mph and gusts have registered as high as 165 mph, the NHC reported.
As Florence travels over deep, warm water, it could become a Category 5 hurricane before losing some steam and making landfall as a Category 4 storm, Monahan said.
“Some strengthening is expected during the next day or so, and Florence is expected to be an extremely dangerous major hurricane through Thursday night,” the Hurricane Center said. “Hurricane-force winds extend outward up to 40 miles from the center and tropical storm-force winds extend outward up to 150 miles.”
Homes can incur major damage and trees can be snapped or uprooted. Even in nearby areas where the storm doesn’t make landfall, rough seas and beach erosion are highly likely, Monahan said.
Thirty- to 40-foot waves to the coast and flooding are concerns, he said.
Flood waters could reach heights of 2 to 8 feet above ground in some places, with the deepest water expected along the immediate coast in the path of onshore winds, where the surge will be accompanied by “large and destructive waves,” according to the Hurricane Center.
Even beyond the coast, flooding could be significant if Florence stalls and dumps huge amounts of rain over the Appalachian Mountains and as far away as West Virginia, Monahan said. Flash floods, mudslides and other dangerous conditions are possible with rain accumulations upwards of 20 inches in some spots.
Ga. EMCs prepared to send 150 workers for relief
Ga. Power: Mass outages not expected, but it’s early
Monahan said Florence could do what Hurricane Harvey did last year over Texas, dumping days of rain, although he said the flooding won’t be quite that scale.
“I expect that’s going to be a significant concern if it makes this inland trek and stalls as expected for Washington, D.C., Raleigh, along back into the mountains of North Carolina, Virginia, West Virginia,” Nitz said. “And even into parts of South Carolina, especially northern South Carolina, they could have some significant inland flooding.”
- Will this be the last storm this hurricane season?
Not even close. In fact, there’s already a “conga line” of storms coming off the west coast of Africa that all have the potential to develop into tropical storms or hurricanes, Channel 2 Chief meteorologist Glenn Burns said.
Channel 2 is tracking hurricanes Isaac and Helene and another wave headed off the west coast of Africa, Nitz said. The tropics remain “very active.”
Hurricane season reached its official peak Monday, so make sure to continue to check for severe weather updates in the upcoming weeks.
—The Associated Press contributed to this article.
» For a detailed forecast, visit The Atlanta Journal-Constitution weather page.
» Download The Atlanta Journal-Constitution app for weather alerts on-the-go.