Updated 7:00 p.m. ET
(CBS/AP) MIAMI - Tropical Storm Isaac is gaining strength as it gets closer to predicted landfall along the northern Gulf Coast. It is not yet a hurricane, but should be soon.
At 5 p.m. Monday, the National Hurricane Center reported that Isaac's top sustained winds had reached 70 mph, up from about 65 mph the evening before. A tropical system becomes a Category 1 hurricane once winds reach 74 mph. CBS News consultant David Bernard reports the storm is predicted to run right over New Orleans, and its maximum sustained winds could be up to 100 mph by the time it makes landfall late Tuesday or early Wednesday.
A hurricane warning is in effect from Morgan City, La., to the Alabama-Florida line -- an area covering 5 million people. East of the state line to Destin, Fla., hurricane forecasters have now posted a tropical storm warning.
The storm's center was located about 255 miles southeast of the mouth of the Mississippi River and is moving northwest at 12 mph. Isaac was expected to make landfall as early as Tuesday, possibly in Louisiana south of New Orleans.
A satellite image of Tropical Storm Isaac as of early Monday evening
Rain and storm surge is considered a major threat, especially if the storm's movement to the northwest at 12 mph slows down. A lot of the lower Mississippi River Valley along the Gulf Coast could see eight to 12 inches of rain. It's not out of the question that some spots could see up to 20 inches of rain. Additionally, coastal flooding will be a problem from both rain and storm surge.
President Barack Obama has declared a state of emergency in Louisiana as that state prepares for Isaac.
he White House said Obama informed Louisiana Gov. Bobby Jindal of the emergency declaration in a phone call Monday. The declaration makes federal funding available for emergency activities related to the storm. Obama also spoke with Alabama Gov. Robert Bentley, Mississippi Gov. Phil Bryant and New Orleans Mayor Mitch Landrieu.
Obama has asked the Federal Emergency Management Agency to coordinate disaster relief efforts with state and local officials along the Gulf Coast.
Forecasters predict Isaac will intensify into a Category 1 hurricane later Monday or Tuesday. Isaac could become the first hurricane to hit the Gulf Coast since 2008.
CBS News correspondent Mark Strassman reports many oil refining facilities in the Gulf's refinery row are exposed to the northeast quadrant of Isaac -- the most powerful and dangerous part of the storm. Just the threat of this storm has already shut down 40 percent of U.S. crude production, and 78 percent of oil well production in the Gulf.
Experts say consumers can expect gas prices to rise through Labor Day before dropping again.
Many New Orleans residents are fleeing the storm's path, as Isaac revives painful memories from Hurricane Katrina in 2005.
As she loaded supplies into her car to prepare for Isaac, Linda Grandison's mind rewound to the nightmare of Katrina: Back in 2005, she had to flee her family's flooded home and waited on a bridge for more than three days before being rescued by helicopter.
Though Isaac is far less powerful than the historic hurricane that crippled New Orleans, the system was on an eerily similar path and forecast to make landfall on the seventh anniversary of Katrina, raising familiar fears and old anxieties in a city still recovering from a near-mortal blow seven years ago.
Traffic is stacked up along Interstate 10 heading West away from New Orleans Monday, Aug. 27, 2012.
(Credit: AP Photo/David J. Phillip)
This time, Grandison is not taking any chances. She will stay with her mother in the New Orleans suburb of Gretna, which did not flood in Katrina. The house has a generator to keep the refrigerator running if power goes out, and she has enough charcoal to grill out for days.
"You can't predict God's work. This is nerve-wracking," she said. "I hate leaving my house, worrying if it's going to flood or get looted. But I'm not going to stay in the city again."
If Isaac comes ashore here, it will find a different city than the one blasted by Katrina. This New Orleans has a bigger, better levee system and other improvements designed to endure all but the most destructive storms. Many neighborhoods have rebuilt. Some remain desolate, filled with empty, dilapidated homes.
The Army Corps of Engineers was given about $14 billion to improve flood defenses, and most of the work has been completed. Experts say the city can handle a storm comparable to a Category 3 hurricane. Isaac is expected to come ashore as early as Tuesday night as a Category 1 storm, striking anywhere from west of New Orleans to the Florida Panhandle.
Mayor Mitch Landrieu said he understood residents' worries, but tried to reassure them that the city was prepared.
"I think everything will be OK," he said.
To keep up the with the latest on Isaac you can visit the National Hurricane Center's website http://www.nhc.noaa.gov/