The storm threatened to hit coastal North and SC with 130 mile-per-hour (215 kph) winds and massive waves when it makes landfall on Friday, and its rains will take a heavy toll for miles inland, the National Hurricane Center in Miami warned.
"Interests elsewhere in the southeastern and mid-Atlantic states should monitor the progress of Florence".
Asked whether additional evacuation orders could be lifted, McMaster said: "Everything is possible".More news: Rodgers returns from injury, leads incredible comeback over Bears
Hurricane Florence is predicted to slam into the US East Coast as a "major" storm.
Tropical Storm Isaac, located 775 miles east of the Lesser Antilles, is moving towards the west near 16 miles per hour (mph). It is now located 950 miles east-southeast of Cape Fear.
The National Hurricane Center says a new report from an Air Force Reserve Unit hurricane hunter aircraft indicates that Hurricane Florence's top sustained winds have decreased slightly to 130 miles per hour (215 kph), with higher gusts. The storm could soon be on the brink of a Category 5. Homes could lose their roofs and exterior walls.
Any of these storms could strengthen into more powerful cyclones in the coming days. Power and water outages could last for weeks.
The storm is now between 500-600 miles wide and gaining strength.More news: Alibaba chairman Jack Ma to step down in 2019: company
If a Category 5 hits the southeastern US, "a high percentage of framed homes will be destroyed, with total roof failure and wall collapse", said the NHC. That would mean more flooding rains across a large part of the U.S. South, expanding the damage, according to Chuck Watson, a disaster modeler with Enki Research in Savannah, Georgia.
In North Carolina, Governor Roy Cooper's evacuation order included the Outer Banks barrier islands.
The threat for life-threatening conditions from Hurricane Florence in North Carolina is increasing. The potential for the storm to stall has residents packing sandbags and preparing for the major flooding that could follow.
Areas near where the eye moves inland will likely see catastrophic storm surge and 120-140mph winds.
Forecasters have said that if it lingers over the region, several feet of rain might fall.More news: Paris stabbing: Several injured in knife spree, suspect arrested
"Our ships can better weather storms of this magnitude when they are underway", Adm. Christopher Grady said in a statement.