Heavy rains were forecast to extend into the Appalachian Mountains, affecting parts of Alabama, Tennessee, Kentucky and West Virginia. Florence's worst aspect: its slowing down and stalling over coastal areas, causing up to 19-foot storm surges, and dropping from 6 to 40 (!) inches of rain.
The NHC notes that amount of rainfall would "produce catastrophic flash flooding and prolonged significant river flooding". The heaviest rainfall is still expected in South and North Carolina, with upwards of 30 inches of rainfall possible in some locations. "It's an extremely risky, life-threatening, historic hurricane". Airlines had canceled almost 1,000 flights and counting.
Florence is about 644 kilometres wide and it's winds have dropped from a peak of 225 km/h to 165 km/h, reducing the hurricane from a terrifying Category 4 to a Category 2.
The storm is not expected to change much in strength before making landfall.
Hurricane Florence in the Atlantic Ocean as it threatens the US East Coast. Governors of those states have already declared states of emergency, as have the governors of Virginia and Maryland.
Weather Underground meteorology director Jeff Masters said Florence eventually could strike as merely a Category 1 hurricane with winds less than 100 miles per hour, but that's still enough to cause at least $1 billion in damage.
Hurricane-force winds now extend up to 80 miles and tropical-storm-force winds extend up to 195 miles from the center of the storm.
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The Carolinas and Virginia are preparing for the onslaught of Hurricane Florence later this week and one of the most life-threatening elements of the storm is the amount of rainfall predicted to hit the area, reports Vox. And 15 counties in North Carolina were under a tornado watch by Thursday morning, including: Beaufort, Carteret, Craven, Dare, Duplin, Greene, Hyde, Jones, Lenoir, Martin, Onslow, Pamlico, Pitt, Tyrrell and Washington Counties. Tropical Storm Isaac is forecast to approach the Lesser Antilles Islands on Thursday. "Once the storm moves further inland to Atlanta and Charlotte, the biggest issue will be rain and thunderstorms", she said.
The other threat for those living along the coast is the wall of water known as storm surge that the hurricane's winds and forward movement push on shore. Storm surge of 13 feet on top of a high tide at 7 feet could overwhelm the town.
People in North Carolina and SC have the daytime hours Thursday to complete their final preparations to ride out or escape the storm.
In August 2017, Harvey made landfall as a Category 4 and practically stalled over southern Texas, dropping record-breaking rain in many areas and causing widespread flooding. Forecasters predict it will make landfall between Thursday and Friday.
An estimated 10 million people live in areas expected to be placed under a hurricane or storm advisory, according to the US Weather Prediction Centre.
And if that isn't enough, Subtropical Storm Joyce formed in the North Atlantic Tuesday afternoon, but it's not expected to hit the U.S. The system is expected to drift to the southwest in the coming days.
Body surfer Andrew Vanotteren, of Savannah, Georgia, crashes into waves in the surf bolstered by the incoming Hurricane Florence on the south beach of Tybee Island, Georgia.