Tornadoes and very strong winds peel the roofs from homes in the Deep South and heaped snow and ice on the Midwest.
Golf-ball and baseball-sized hail pelted parts of Georgia and the Carolinas late Thursday and early Friday.
Three people were killed.
Isaac was downgraded to a tropical depression on Thursday and is moving into the central United States.
It left little damage in New Orleans, where stronger barriers were installed after Hurricane Katrina in 2005 but leaving large areas of the region flooded.
A report says that seven tornadoes have spun off from Isaac in Mississippi and Alabama.
A tornado that touched down in Gulfport, Mississippi had caused significant destruction to homes.
Now, there is a potential failure of Lake Tangipahoa Dam in Mississippi’s Percy Quin State Park.
Authorities ordered the immediate evacuation of tens of thousands of residents in nearby communities in Louisiana and Mississippi as a protective measure if the dam burst flooded the areas.
The Category 1 Hurricane Isaac hit New Orleans exactly seven years after New Orleans was hit by Hurricane Katrina on August 29, 2005.
So far the new barriers built to protect the city after the 2005 Katrina disaster has not been breached.
Anyway a levee on the outskirts of New Orleans has been breached on Wednesday.
Emergency management officials in low-lying Plaquemines Parish reported the over topping of an 8-foot (2.4-meter) high levee between the Braithwaite and White Ditch districts southeast of New Orleans.
There are reports of people on their roofs and attics and 12 to 14 foot of water in their homes.
The greatest concern is an expected storm surge of between 6 and 12 feet off the Louisiana and Mississippi coasts, 4 to 8 feet along the Alabama coast and 2 to 4 feet on the Florida Panhandle.
Storm surge is when hurricane winds raise sea levels off the coast, causing flooding on land.
Farther south, water was pushed over a rural levee and flooded some homes.
Beach front roads were under water, and more than a half-million people had lost power in Louisiana.
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