The floodwaters are expected to push many rivers to all-time record high levels and may spur life-threatening landslides
Despite its weakened status to a tropical storm, Florence has deluged parts of the North Carolina coastline with torrential and historic amounts of rain. Many areas in southeastern North Carolina have endured 15 to 30 inches of rain and up to another 15 inches could fall.
The rain is resulting in a catastrophic flooding in southeast North Carolina which is spreading into the interior, reaching even into the population centers of Raleigh and Charlotte. Already, the event has already broken North Carolina's state record for most rain in a tropical storm or hurricane, with a preliminary report over 30 inches.
The floodwaters are expected to push many rivers to all-time record high levels and, toward the mountains of western North Carolina and southwest Virginia, may spur life-threatening landslides.
The Associated Press reports the storm may unload 18 trillion gallons of rain on the Southeast and Mid-Atlantic. "Florence's 18 trillion gallons is as much water as there is in the entire Chesapeake Bay," its article says. "It's also enough to cover the entire state of Texas with nearly four inches (10 centimeters) of water."
Onslow county, located about 50 miles to the northeast of Wilmington, has been hit particularly hard. The National Weather Service office in Newport, North Carolina, (located on the eastern edge of Onslow County) recorded a storm total of 23.75 inches just after midnight. And as of Saturday morning, several other locations scattered across the county were on the verge of passing the 20-inch mark.
A citizen weather observer posted a total of 30.58 inches of rain in Swansboro, which is in Onslow County, and would be a state a record for a tropical storm or hurricane if verified. While the amount is unofficial, it would shatter the old record of 24 inches - set near Wilmington during Hurricane Floyd in 1999. Many locations in southeast North Carolina are likely smash this old record by the time the rain ends.
Florence is forecast to "drop almost double" the volume of rain over the state compared to Floyd, tweeted Ryan Maue, meteorologist for weathermodels.com.
Since making landfall at Wrightsville Beach in North Carolina on Friday morning, Florence's forward speed has slowed down dramatically, with the storm's center of circulation only about 100 miles away from Wrightsville Beach a full 24 hours after landfall. The storm's slow and parallel movement to the coastline created several bands of heavy rain, capable of producing 2 to 4 inches of rain per hour, sitting over the same locations for essentially the last day and a half.
Florence will continue to move very slowly to the southwest on Saturday, which in turn will drag the axis of heavy rain bands to the southwest as well. That should spell some relief for the inundated areas of Onslow County, but unfortunately puts the city of Wilmington, southeast coastal communities of North Carolina and northeast areas of South Carolina in the line of fire instead.
Through Sunday morning, over a foot of rain is expected to fall in and around Wilmington, adding to the 6 or so inches of rain the city has already received from Florence. One model even shows the potential for an additional 30 inches, although that may be overdone.
The heaviest of the rain should gradually taper off in southeast North Carolina throughout Sunday.
Most of the rivers in northeast South Carolina and eastern North Carolina are experiencing moderate to major flooding and, in some cases, many continue rising well into next week as floodwaters from the interior flow downstream.
The Cape Fear River in Fayetteville, North Carolina, is forecast to rise an astonishing 45 feet by Tuesday.
Flooding concerns extend beyond the coast of North Carolina as well. Flash flooding has spread into Raleigh and will expand over Charlotte as well, where flash flood advisories are in effect.
As the storm center shifts further inland, counterclockwise rotation around the center of circulation will continue to pull in loads of tropical moisture from the Atlantic ocean and pushing up against the more rugged terrain of central and western North Carolina.
The elevation will serve as a forcing mechanism for the abundant low level moisture being dragged in by Florence, essentially creating an ideal environment for torrential rain and the possibility of mudslides, especially Sunday into Monday. Through Tuesday, 5 to 10 inches of rain, and isolated 15-inch amounts, are forecast to fall across central and western North Carolina and southwestern Virginia.
Florence will ultimately lose its tropical designation sometime Saturday, but the storm will continue be a danger as it starts to turn north by Sunday afternoon. However, there remains a large amount of uncertainty in the ultimate track of what will become post tropical storm Florence.
Computer models mostly show the remnants of Florence tracking into western North Carolina on Sunday afternoon, before making a sharp turn to the north/northeast as the storm begins to get picked up by the jet stream over North America. However, there is still some disagreement among the models as to how much of the storm center motion is to the north versus to the northeast.
If the storm tracks further to the west and up into the Ohio River Valley, the worst of the heavy rain and associated impacts of the storm would be centered to the west of the Washington area and more focused toward western Pennsylvania and eventually interior New England. However, if the storm takes a more easterly track, much of the Mid-Atlantic would be exposed to a period of heavy rain and even the threat of some severe weather late on Monday and into Tuesday.