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Hurricane Florence threatens to unleash catastrophic inland flooding in Carolinas, Virginias

By Alex Sosnowski • Sep 10, 2018 at 4:53 PM

With the potential for Florence's forward speed to slow and possibly stall, a current forecast of feet of rain would lead to catastrophic flash flooding and major river flooding in parts of the Carolinas, Virginia and possibly other neighboring states.

“Most of hurricane damage and loss of life occurs not on the coast, but from flooding as the result of heavy rain. And even though Hurricane Florence is a powerful storm, that will be the case here too,” AccuWeather President and Founder Dr. Joel N. Myers said.

“There could be devastating floods well in from the coast back in the hills and mountains of North Carolina, Virginia and West Virginia,” Myers said.

As AccuWeather meteorologists have warned about since the middle of the summer, any tropical storm or hurricane that moves over saturated ground in the eastern United States during the height of the hurricane season may lead to disastrous flooding.

"Strength, track and forward speed of Florence will be the major players in determining the scope and amount of rainfall and correspondingly the severity of inland flooding," said Dan Kottlowski, AccuWeather hurricane expert.

Even in lieu of the worst-case scenario, Florence has the potential to join the ranks of the costliest natural disasters in the history of the United States joining Irma, Maria and Harvey in 2017; Sandy in 2012; Katrina in 2005 and Andrew in 1992.

In addition to storm surge flooding, inland flooding will escalate from urban and poor drainage areas to small streams. However, even as torrential rain ceases days after the initial first drops from Florence, some major rivers in the region are likely to reach major flood stage.

Some communities may be under water for days and possibly a week or more.

"Precautionary preparations for major flooding are advised," Kottlowski said.

Following the state of emergency that has been declared in North Carolina, South Carolina and Virginia, property owners are urged to take action.

"People should expect not only travel disruptions but also disruptions to daily activities related to work or school."

Moving the most valuable items out of the basement and first floor onto the second floor in flood-prone areas may be of interest at this time. Locate important papers and photographs.

As the rain pours down during the storm, inland evacuations may become necessary and the time for completing such tasks will come to an end.

Have a plan of action in place ahead of the flooding. Work-at-home plans may not be an option in some communities where the power goes out or flooding commences. Without a means of power, computer and cell phone batteries will drain.

On Thursday, the first bands of rain directly associated with Florence will arrive on the Carolina and Virginia coasts. Rainfall will then spread inland and northward and intensify through Friday and during the weekend.

"At this time, the most likely scenario is for 1-2 feet of rain with a Local AccuWeather StormMax of 32 inches centered on portions of North Carolina and Virginia from Florence," Kottlowski said.

"Torrential rain would still affect portions of South Carolina as well."

This leading scenario assumes that Florence's forward speed slows upon nearing the coast, but the storm continues to drift inland slowly.

A continued northwestward drift or curve to the north may cause heavy rain to fall and raise the risk of flooding farther north and west in Tennessee, West Virginia, Maryland and Pennsylvania this weekend.

A more extreme scenario suggests that Florence completely stalls on the coast or inland for days. In such a scenario, a number of locations may receive more than 2 feet of rain with perhaps some locations topping 3 feet from the coast to the Piedmont and southern Appalachians.

There is still a scenario that brings Florence to near the North Carolina coast, but keeps the hurricane offshore. Such a track may spare the southern Appalachians and Piedmont of catastrophic rain and flooding.

There is another scenario, where Florence may slow near the coast and crawl northward to some extent along the mid-Atlantic coast, Kottlowski stated.

In this case, areas as far north New York City and southern New England should monitor Florence's track for strong winds and above-normal tides, let alone the risk of flooding from torrential rainfall.

Meanwhile, rain, partially associated with Tropical Rainstorm Gordon, will continue to drench some of the Northeast into Tuesday.

Were rain from Florence to overlap rain from Gordon, a mere several inches of rain this weekend could be enough to initiate stream and river flooding.

Some streams and rivers in parts of the Northeast are at major flood stage as of Monday morning following two or more days of steady rain. Up to 8 inches of rain have fallen on parts of Pennsylvania this past weekend, on top of what has been the wettest summer on record for a number of locations in the mid-Atlantic states.

Will areas south of the storm track be spared?

The heaviest and steadiest rain tends to focus north and northwest of a hurricane making landfall along the Atlantic coast.

At this time, it appears that Georgia and Florida is likely to be spared the risk of torrential rain and flooding from Florence. Only a track more to the west or west-southwest would cause that forecast to change.

Rain could wrap in and linger across part of mid- and upstate South Carolina even with a North Carolina or Virginia storm track.

Initially, sporadic showers and thunderstorms not associated with Florence are in store for the southern Atlantic region into Wednesday.

Most likely, dry air will sweep in across Georgia, Florida and part of South Carolina from the west as Florence either pushes inland over North Carolina and Virginia or hovers along the North Carolina and Virginia coasts.

EDITOR’S NOTE: Alex Sosnowski is a AccuWeather senior meteorologist

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