As an added punch, one of the things meteorologists are keeping an eye on is high tide, Wagstaffe said, which is expected late Thursday into Friday - exactly around the time when Florence is expected to make landfall.
On the heels of the most expensive hurricane season ever, the approaching storm raises the questions: What role is climate change playing - and could technology offset these growing dangers? Current forecasts call for Florence to be at least a Category 3 storm when it arrives at the Carolinas.
U.S. President Donald Trump on Twitter warned of the storm's dangers and praised his administration's handling of past hurricanes, rejecting criticism for its response to Hurricane Maria a year ago in Puerto Rico. It remains an extremely unsafe major hurricane through Thursday night. Texas saw a similar scenario in 2017, when Hurricane Harvey's center moved just inland, and its counter-clockwise rotation allowed the storm to continually pull moisture inland from the Gulf of Mexico.
Long cautioned coastal residents via Twitter of storm surges up to 12ft - "rapid rise of water that is overwhelming and deadly". At 8 a.m. (1200 GMT) on Wednesday the storm was located about 530 miles (855 km) southeast of Cape Fear, North Carolina.
"Florence is forecast to be an extremely risky major hurricane as it approaches the US coast", the NHC said.
With the storm churning across the Atlantic with 140 miles per hour winds, hurricane watches and warnings include the homes of more than 5.4 million people on the East Coast.
The storm taking aim at the Carolinas is likely to bring "life-threatening, catastrophic flash flooding and significant river flooding" when it sweeps in on Thursday and Friday, the National Weather Service (NWS) said. While it may or may not officially become a Category 5 storm, it will still be a major Hurricane at landfall.
Two other hurricanes, Helene and Isaac, are now trailing Florence in the Atlantic and forecasters have warned that they could head for the UK.
A storm surge watch is also in effect for part of this area. Sustained winds were 130 miles per hour (215 kph) Tuesday morning, but it remains a Category 4 storm and is expected to approach the most-damaging Category 5 status as it slows and strengthens over very warm ocean water near North and SC.
Forecasters said parts of North Carolina could get 20in of rain, if not more, with as much as 10in elsewhere in the state and in Virginia, parts of Maryland and Washington DC.
The last time the U.S. capital declared a state of emergency was in January 2016 when a winter storm dubbed "Snowzilla" blanketed the capital region in knee-deep snow.
Several inches of rain will fall across the state.
On the right side of this view is Helene, a Category 2 hurricane that will likely peter out in the Atlantic without making landfall, according to the latest update from the National Hurricane Center (NHC), a division of NOAA. He said the federal government is "absolutely, totally prepared" for Florence. "When you stall a system like this and it moves real slow, some of that rainfall can extend well away from the center".
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.
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.
"This paper doesn't really say what we've had so far, if there's a trend", said Bhatia.