Forecasters say Tropical Storm Isaac will weaken to a tropical depression Thursday as it continues on a northern path over the U.S. Gulf Coast state of Louisiana.

The National Hurricane Center said Isaac is carrying maximum sustained winds of 95 kilometers an hour, and could dump as much as 63 centimeters of rain in isolated parts of Louisiana, Mississippi, Alabama and Arkansas through Friday. The storm is expected to move into the drought-stricken midwestern United States, where rain is badly needed.

Isaac struck Louisiana and the neighboring Gulf Coast states of Mississippi and Alabama Wednesday as a category one hurricane, causing strong winds, heavy rain, and massive flooding. Hundreds of residents in Louisiana's Plaquemines Parish, a small coastal area located south of New Orleans, were trapped after floodwaters overtopped levees.

Authorities and residents scrambled to rescue neighbors who had ignored evacuation orders ahead of Isaac's arrival.

But experts say the extensive system of levees, canals and pumps, built after Hurricane Katrina caused widespread death and destruction seven years ago Wednesday, helped spare New Orleans from extensive damage this time.

Seven hundred thousand people were without power at the peak of the storm. Authorities say they will assess storm damage and look for victims once the wind and rain let up.

U.S. President Barack Obama declared emergencies in Louisiana and Mississippi, making both states eligible for federal funding and other aid. Emergency assistance teams were dispatched to the region in advance of the storm.