NEW ORLEANS -- Flood-weary New Orleans braced Thursday for the weekend arrival of Tropical Storm Nate, forecast to hit the area Sunday morning as a weak hurricane that could further test a city drainage system in which weaknesses were exposed during summer deluges.

In nearby St. Bernard Parish on Louisiana's southeast coast, authorities ordered the evacuation of areas unprotected by levees. And to the south of New Orleans, in the barrier island town of Grand Isle, officials called a voluntary evacuation.

In Baton Rouge, Louisiana activated its emergency operations center, and Gov. John Bel Edwards planned an afternoon meeting with emergency officials ahead of a media briefing. According to the Reuters news agency, BP shut down all of its Gulf Coast oil production ahead of the storm.

A map from the National Hurricane Center shows the probable path of Tropical Storm Nate as of 2 p.m. ET on Oct. 5, 2017. D stands for tropical depression. S stands for tropical storm. H stands for hurricane. The blue lines represent areas under tropical storm warnings. National Hurricane Center

Nate formed Thursday in the western Caribbean Sea near Nicaragua. CBS News weather producer David Parkinson said the storm could stall over Mexico's Yucatan peninsula, but the forecast track shows that it likely will intensify in the Gulf of Mexico and could become a Category 1 storm. It has the potential to strengthen to a Category 2 storm, Parkinson said.

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The forecast track had it reaching Louisiana's southeastern tip early Sunday, although the range of possible landfalls extended from the central Louisiana coast westward into Alabama.

In New Orleans, Mayor Mitch Landrieu declared a state of emergency.

"Since early August, we have made substantial progress," Landrieu said of work to upgrade the city drainage system. But he warned at an afternoon news conference that extremely heavy rain and storm surge from Nate still could pose flood dangers.

His office outlined steps being taken to improve weaknesses laid bare in the pumping and drainage system after an Aug. 5 deluge led to flooding of homes and businesses in some sections of the city. In the days that followed came revelations of pumps and power-generating turbines that weren't working, as well as personnel shortages at the Sewerage and Water Board, the agency that runs the drainage system.

The city said 108 of 120 pumps were fully operational Thursday and said 26 backup generators were also in place. Also, the city said efforts to clean thousands of street catch basins had been stepped up, with vacuum trucks dispatched to various areas to suck out thick mud and debris.

New Orleans has faced heavy floods this year. Family-owned Orleans Sheet Metal wearily prepared as the storm neared, with its owners saying they had never seen flooding like this year, CBS affiliate WWL-TV reports. Three times the shop has been affected by floodwaters on Orleans Avenue.

"The first time a little bit forgiving, the next time, okay guys what's going on, now? You have a small rain storm, but things still aren't fixed," said Tracy Schwander Alonzo, whose family has owned the business for four generations.