NEW ORLEANS (AP) - As Tropical Storm Marco made landfall, the Gulf Coast turned its attention Monday to Laura, another system following just behind that could grow into a supercharged Category 3 hurricane with winds topping 110 mph and a storm surge that could swamp entire towns.

Laura strengthened to a hurricane on Tuesday morning churned just south of Cuba after killing at least 11 people in the Dominican Republic and Haiti, where it knocked out power and caused flooding in the two nations that share the island of Hispaniola. The deaths reportedly included a 10-year-old girl whose home was hit by a tree and a mother and young son who were crushed by a collapsing wall.

Laura was located about 81 miles northeast of the western tip of Cuba and 765 miles southeast of Lake Charles, Louisiana. The storm was moving west northwest at 20 mph with maximum sustained of 75 mph.

The center of Laura will move away from Cuba and over the southeastern Gulf of Mexico overnight.

The storm is then forecast to move over the central and northwestern Gulf of Mexico Tuesday night and Wednesday, and approach the northwestern coast of the Gulf of Mexico Wednesday night.

“Our sights are on Laura now,” Gov. John Bel Edwards told a news briefing. “It has the potential to be a major hurricane.”

Shrimp trawlers and fishing boats were tied up in a Louisiana harbor ahead of the storms. Red flags warned swimmers away from the pounding surf. Both in-person classes and virtual school sessions were canceled in some districts.

In Port Arthur Texas, Mayor Thurman Bartie warned that unless the forecast changes and pushes Laura’s landfall farther east, he will ask the city’s more than 54,000 residents to evacuate starting at 6 a.m. Tuesday.

“If you decide to stay, you’re staying on your own,” Bartie said.

Officials in Houston asked residents to prepare supplies in case they lose power for a few days or need to evacuate homes along the coast.

Across the border in Louisiana’s Cameron Parish, residents were preparing as well. Mandatory evacuation orders were issued for much of the parish, where officials said seawater pushed inland by the storm could submerge small coastal communities.

In other coastal areas residents moved possessions to higher ground, filled sandbags and in one case, moved pews and other items from a church that has flooded before.