The storm has rapidly intensified and reached "major hurricane" classification on Monday morning (with maximum sustained winds of 130 miles per hour, making it a Category 4), although eyes are also on Isaac and Helene for the future.
"With the possibility that Tropical Storm Florence could make landfall in SC, likely as a hurricane, our people have already started making preparations", Attorney General Alan Wilson said.
Hurricane Florence is plowing toward the East Coast as a Category 4 storm with a 500-mile wing span, forcing dire warnings and mandatory evacuations - including the entire coastline of SC and parts of Virginia and North Carolina.
State emergency management officials already are considering whether to recommend counties evacuate some homes along the Tar, Lumber and Neuse rivers.
The first effects were already being seen on barrier islands Monday as risky rip currents and seawater flowed over the state highway.
North Carolina Governor Roy Cooper also urged his state's residents to get ready, noting the storm already was generating swelling waves and unsafe currents along the coast.
Major flooding is predicted for a vast swath of land from Roanoke, Virginia to Charlotte, North Carolina.
The NHC also says the storm could become more powerful.
All eyes are on Hurricane Florence and its path toward the Carolinas, but other hurricanes and tropical storms are brewing as well.
"Pretend, assume, presume that a major hurricane is going to hit right smack dab in the middle of SC and is going to go way inshore", McMaster said in a press conference.
Florence crossed the 74 miles per hour threshold from a tropical storm to a hurricane on Sunday morning and by 11 p.m. that night had sustained a maximum of 90 miles per hour winds. We will experience tropical storm-force winds as early as Wednesday evening.
As of 5 a.m., there are no coastal warnings or watches in effect as those are only issued until a storm is about 48 hours from landfall.
The hurricane has been rapidly strengthening all morning.
The US Navy added that it was sending almost 30 ships from Virginia to sea in order to avoid damage.
The counter-clockwise rotation of hurricanes means more damage to the storm's upper right quadrant, viewing it from above, but less impact to the lower left side.
"With this order government agencies will begin to mobilize in anticipation of a hurricane", McMaster said. The center warns that such storms will snap or uproot most trees and down power poles and that power can be out in some areas for weeks or months.