Transcript for State of emergency for New Orleans as flash floods strike city
And we begin tonight with the state of emergency, as a tropical storm now bears down in the gulch. In fact, it could become a hurricane. In fact, hurricane watches are up tonight across several states already. And New Orleans already under water. Tonight, authorities there are bracing for what could be a major test of the levee system after Katrina. Dark clouds and a water spout there on lake pontchartrain. Streets turned into rivers. This streetcar, the only traffic in a flooded downtown new Orleans. And take a look. This satellite image tonight of the tropical threat right now at this hour. Meteorologist rob Marciano is just outside New Orleans tonight, leading us off. Reporter: Tonight, a state of emergency for New Orleans. This water spout spotted marching across lake pontchartrain, as severe storms ripped through homes like this one. Whole bedroom was blown out and my wife and dog were kind of under the rubble. Reporter: And flash floods pounding the dumping up to half a foot of rain, turning roads into rivers. The famed French quarter submerged. Drivers forced to abandon their cars. Residents getting around any way they could. This man swimming through deep water. This is ridiculous. This is like Venice out here. Everybody need a boat or something. This is really sad. Reporter: And it is only the beginning. Louisiana bracing for a hurricane or tropical storm. We don't know yet where this storm is going to land, but we know it's going to be a big storm, a significant rain and storm surge event. Reporter: The people here taking no chances. They're stocking up on supplies. In the gulf of Mexico, oil companies already pulling workers off their rigs. And a scramble to sandbag. Tonight, the levee system facing one of its biggest tests since hurricane Katrina. The Mississippi expected to reach 20 feet, highest level in 70 years. Let's get right to rob Marciano, just outside new Orleans. And I know that's a key to actually relieving pressure on the levees in New Orleans if they need it? Reporter: It is, David. It is key, but it can only relieve so much. It die verdicts 10% of the water flow and it's going to be running hard here over the next several days. The center of this system, about 125 miles to the southeast of the mouth of the Mississippi. It is forecast to become a tropical storm, Barry, tomorrow, and then move towards the Louisiana coast during the day on Friday. Strengthening to potentially a category 1 storm, making landfall during the day on Saturday, somewhere between Houston and New Orleans. We have hurricane watches up for much of the Louisiana coastline. Flash flood watches up, especially for points east. We could see 10 to 20 inches of rainfall. That rain, plus the storm surge, could bring the river levels to the point where they start to overtop in and around new Orleans. David? All right, it seems so early for this, but the season is here.
This transcript has been automatically generated and may not be 100% accurate.