By SARA CLINE and JAMIE STENGLE Associated Press

BATON ROUGE, La. (AP) — Tropical Storm Francine strengthened in the Gulf of Mexico on Monday and was forecast to make landfall as a hurricane this week in Louisiana, where evacuation orders were quickly issued in some coastal communities and residents began filling sandbags in preparation for heavy rains and widespread flooding.

Francine, the sixth named storm of the hurricane season, was expected to become a hurricane by Monday night or Tuesday morning, U.S. National Hurricane Center in Miami said. The storm, expected to make landfall Wednesday night in Louisiana, was already being felt in Mexico, where rains closed schools as the storm gathered strength in the Gulf.

“We’re going to have a very dangerous situation developing by the time we get into Wednesday for portions of the north-central Gulf Coast, primarily along the coast of Louisiana, where we’re going to see the potential for life-threatening storm surge inundation and hurricane-force winds,” said Michael Brennan, director of the U.S. National Hurricane Center in Miami.

Francine is taking aim at a stretch of coastline that has yet to fully recover since hurricanes Laura and Delta decimated Lake Charles, Louisiana, in 2020, followed a year later by Hurricane Ida. Over the weekend, a 22-story building in Lake Charles that had become a symbol of the destruction was imploded after sitting vacant for nearly four years, its windows shattered and covered in shredded tarps.

The storm surge pushed by Francine could reach as much as 10 feet (3 meters) along a stretch of Louisiana coastline from Cameron to Port Fourchon and into Vermilion Bay, forecasters said. And if the current track holds, the storm could blow northward up the Mississippi River, into the Illinois area by Saturday.

“Francine is expected to bring multiple days of heavy rainfall, considerable flash flooding risk,” Brennan said.

Louisiana officials urged residents to immediately prepare for the storm while “conditions still allow” for it, Mike Steele, spokesperson for the Governor’s Office of Homeland Security and Emergency Preparedness, told The Associated Press.

Storms like Francine can rapidly intensify and people don’t have the luxury of days to prepare, Steele said.

“We always talk about how anytime something gets into the Gulf, things can change quickly, and this is a perfect example of that,” Steele said.

Residents of Baton Rouge, Louisiana’s riverfront capital, began forming long lines as people filled up their gas tanks and stocked up on groceries. Others went to fill sandbags at city-operated locations to try to keep floodwaters from entering their homes.

“It’s crucial that all of us take this storm very seriously and begin our preparations immediately,” Baton Rouge Mayor-President Sharon Weston Broome said during a news conference Monday morning.

She urged residents to prepare a disaster supply kit, complete with enough food, water and essential supplies for three days.

A mandatory evacuation was ordered for seven remote coastal communities by the Cameron Parish Office of Homeland Security & Emergency Preparedness. They include Holly Beach, a laid-back stretch dubbed Louisiana’s “Cajun Riviera,” where many homes sit on stilts. The storm-battered town has been a low-cost paradise for oil industry workers, families and retirees, rebuilt multiple times after being struck by hurricanes.

And in Grand Isle, Louisiana’s last inhabited barrier island, Mayor David Camardelle recommended residents evacuate and ordered a mandatory evacuation for those in recreational vehicles. Hurricane Ida decimated the city three years ago, damaging almost all of its 2,500 structures and destroying 700 homes.

Officials warn that flooding in the area is likely to begin Tuesday afternoon and persist through Thursday. There are also threats of high winds, downed trees and power outages.

The hurricane center said late Monday afternoon that Francine was about 150 miles (245 kilometers) south-southeast of the mouth of the Rio Grande, and about 435 miles (700 kilometers) south-southwest of Cameron, Louisiana, with top sustained winds of about 65 miles per hour (100 kilometers per hour). It was moving north-northwest at 7 mph (11 kph).

As the rains from the storm began falling early Monday in northern Mexico, more than a dozen neighborhoods in Matamoros — across the border from Brownsville, Texas — flooded, forcing schools to close Monday and Tuesday. Marco Antonio Hernandez Acosta, manager of the Matamoros Water and Drainage Board, said they were waiting for Mexico’s federal government to provide pumps to drain the affected areas.

The storm was expected to move in north-northeast motion through Monday evening and then accelerate to the northeast beginning Tuesday before nearing the upper Texas and Louisiana coastlines Wednesday.

A storm surge warning has been issued from east of Galveston, Texas, to the mouth of the Mississippi River in Louisiana, while a hurricane warning has been issued for the Louisiana coast from Sabine Pass to Morgan City.