There's a mandatory evacuation in place for three towns in Louisiana's Jefferson Parish as heavy rains from Tropical Storm Lee began pounding southern parts of the state on Saturday morning.

Lee is still lingering a ilittle offshore in the Gulf of Mexico, but it is surely gathering strength and packing maximum sustained winds of about 60 mph.

Jefferson Parish Council member Chris Roberts said the evacuation was in effect for the towns of Lafitte, Crown Point and Barataria.

The storm is expected to cause extensive flooding in southern Alabama, Louisiana and Mississippi, with rainfall that can amount to 20 inches in some areas.

There are reports that heavy rains and tidal surge pushed Bayou Barataria over its banks in the area near New Orleans.

Roberts told Reuters that if residents in low-lying areas didn't leave now, it could be a couple of days before they were able to get out.

The National Weather Service said the center of Tropical Storm Lee should hit the Louisiana coast on Saturday morning or early afternoon, then move slowly across southern Louisiana on Sunday.

New Orleans was battered by Hurricane Katrina in 2005, which broke levees and flooded areas for weeks. Officials believe the levees can withstand Lee's force.