Duke Energy, the nation's No. 2 power company, said Florence could knock out electricity to three-quarters of its 4 million customers in the Carolinas, and outages could last for weeks.
The National Weather Service is forecasting "significant" river flooding, especially in the northeastern portion of the state. "A watch is typically issued 48 hours before the anticipated first occurrence of tropical-storm-force winds, conditions that make outside preparations hard or unsafe".
Winds and waves began battering the Carolinas on Thursday as officials warned that Hurricane Florence - while weakening slightly - remains a "very risky storm" capable of wreaking havoc along a wide swathe of the US East Coast.
The National Hurricane Center (NHC) downgraded it to a tropical storm on Friday, but warned it would dump as much as 30 to 40 inches (76-102 cm) of rain on the southeastern coast of North Carolina and part of northeastern SC.
Meteorologists warn the storm may be one of the worst to hit the region in decades and could potentially be the worst to hit ever.
"Residents in the path of these devastating storms should comply with all evacuation orders and other emergency instructions".
Hurricane Florence could flood thousands of buildings.
"This possibility could bring prolonged hurricane-force winds and storm surge throughout Saturday and Sunday, to coastal areas along North and SC, and significant inland flooding to whole region", RMS said.More news: 3,000 dead, but Trump hails Hurricane Maria response as ‘unsung success’
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But the most risky threat comes from Florence's rains and storm surge, which could bring flooding far inland.
Even if Florence were downgraded to a Category 1 hurricane, it would still cause extensive damage, Abrams says. A slow motion over eastern SC is forecast Friday night through Saturday night.
As of 11 a.m., Florence was located at 33.4 N, 75.5 W, about 145 miles (230 km) ESE of Wilmington, North Carolina, and about 195 miles (315 km) east of Myrtle Beach, South Carolina.
Despite all the warnings from numerous authorities, some residents say are planning to ride out the storm.
A state of emergency has been declared in five coastal states: North Carolina, South Carolina, Georgia, Maryland and Virginia and the USA capital Washington.
"Just because the wind speed came down, the intensity of this storm came down to a Cat 2, please do not let your guard down", warned Brock Long, administrator of the Federal Emergency Management Agency (FEMA). A warning is typically issued 36 hours before the anticipated first occurrence of tropical-storm-force winds, conditions that make outside preparations hard or risky.
With Florence, the surge threats and rain estimates have not changed, Tillis said, and everyone needs to listen to local law enforcement and first responders.
"A storm surge warning means there is a danger of life-threatening inundation, from rising water moving inland from the coastline".
From Thursday night through Sunday morning, CNN reported that Florence would travel only 150 miles, or slower than the average walking pace of 2-3 mph.