After Florence makes landfall, that ridge, now over Washington and NY, will move east - but be replaced by another one forming over the Great Lakes that will likely keep the storm stuck, McNoldy said.
A storm as big as Hurricane Florence will hit with a "one-two punch" deluge of water, Erik Salna, the associate director of the International Hurricane Research Center at Florida International University, says.
"You're going to get heavy rain, catastrophic, life-threatening storm surge, and also the winds", Graham said.
Officials are also predicting major flooding in places "well away" from the storm's landfall, such as West Virginia, Maryland, southern Pennsylvania and northern Georgia, Steve Goldstein, the National Oceanic and Atmospheric Administration liaison to FEMA, said on the call.
North Carolina Governor Roy Cooper has told locals "don't bet your life on riding out a monster" as 140mph winds get set to batter the shoreline, with SC and Virginia also braced for impact.
Florence, a Category 4 storm with winds of 130 miles per hour (210 kph), was about 905 miles (1,455 km) east-southeast of Cape Fear, North Carolina, at 11 in the morning.
"We have to be careful we're not asking them to come back to Beaufort County through a storm", he said.
Florence could hit the Carolinas harder than any hurricane since Hazel packed 130mph (209kph) winds in 1954 and killed 19 people in North Carolina. Unfortunately, the forecast is for the storm to stall out and drop a ton of rain in the Carolinas.
The center of Florence will move over the southwestern Atlantic Ocean between Bermuda and the Bahamas through Wednesday, and approach the coast of North Carolina or SC in the hurricane watch area Thursday and Friday. It took Matheson and her husband almost the whole day Monday to drive the 100km off the barrier island.
Many newcomers have moved to the coast in the almost 19 years since the last strong hurricane - Floyd - threatened the area.
"You may see a smaller footprint from the operations staff, but. that is what is needed at the time, at this time in the state", Byard said.
Since then, the coastal population has grown by thousands of people.
Florence's projected path includes half a dozen nuclear power plants, pits holding coal ash and other industrial waste, and numerous hog farms that store animal waste in massive open-air lagoons.
People living on the coastal barrier islands have been issued with a mandatory evacuation order by Governor Cooper for the first time in history.
"I don't want to be an alarmist, but as we look at storms of the past, there are parts of what we see in Florence that could fall out that way", Barnes said.
Warmer than normal sea temperatures to add energy and rain to a storm.