Hurricane Florence built momentum in a beeline dash toward the Louisiana coast Friday, chasing thousands of offshore oilworkers and coastal residents to safety in advance of winds forecasters said could exceed 100 mph by the time it slammed ashore.

A hurricane warning extended from Cameron, La., to Pensacola, Fla., as the storm pressed toward the mouth of the Mississippi River with maximum sustained winds of 80 mph, more than minimal hurricane force, and gusts nearly 100 mph.At 2 p.m. MDT, Florence was centered near latitude 28.0 north, longitude 89.2 west or about 150 miles south of New Orleans. It was moving northward at about 15 mph and expected to cross the southeast Louisiana coast at Buras during the night.

New Orleans Mayor Sidney Barthelemy declared a state of emergency and urged all residents of low-lying areas to leave their homes.

"We just want people to start taking precautions because this is a fast-moving storm," Barthelemy said.

The timing and predicted landfall of Florence was reminiscent of the killer hurricane Betsy that hit the mouth of the Mississippi with 136 mph winds on Sept. 9, 1965, and flooded New Orleans, killing 75 people and causing $1.4 billion in damage.

"Satellite pictures and other data indicate Florence may become a little stronger than previously forecast," said Bob Sheets of the National Hurricane Center. "Wind speeds could reach 100 mph with higher gusts in squalls near and to the east of where the center makes landfall."

Evacuations were ordered or advised from low-lying, flood-prone areas from Grand Isle, La., to Biloxi, Miss.