Isaac Strengthens To Category One Hurricane, Louisiana Landfall Expected Tonight

The storm was about 160 miles from New Orleans as of 11:20 a.m., with its central pressure lowering to 975 mb, which leads to stronger winds. It is the fourth hurricane of the 2012 Atlantic season. It could gain strength as it continues its trek northwest.

The storm's surge and heavy rains pose a serious flood risk for four states lining the Gulf Coast. Isaac's expected landfall in New Orleans Tuesday night or early Wednesday morning would line it up nearly seven years to the day since Hurricane Katrina hit the city. Isaac may present the first significant test of the city's bolstered levies in the seven years since Katrina decimated the Big Easy.

President Barack Obama urged Gulf Coast residents act with caution when dealing with the "dangerous" storm, suggesting they follow the instructions of their local officials. (See video below). He also signed a disaster declaration for Louisiana, which opens the valves on federal aid to the state.

"We are dealing with a big storm, and there could be significant flooding and other damage across a large area," Obama said. "Now is not the time to tempt fate."