(CNN) — The Mississippi River is expected to crest Tuesday, a day earlier than previously expected, emergency officials said, as Tennessee residents evacuated from low-lying areas to avoid the swollen waters.

Forecasters say the Mississippi River will crest at 48 feet in Memphis on Tuesday, the Shelby County Emergency Management Agency said.

As the Mississippi River gushes downstream with no clear boundaries, flooding continues to deluge parts of Tennessee as residents farther south brace for what will come.

Shelby County Mayor Mark Luttrell urged residents to be calm and helpful during the crisis. Memphis is in the county.

“Our community is facing what could be a large-scale disaster,” he said. “All of the mayors in the towns and cities throughout our county are staying in close contact with each other.”

Residents of a trailer park were evacuated Saturday because of high waters, said Heather Reynolds, spokeswoman for the Memphis/Shelby County Emergency Management Agency.

Authorities in the Memphis area warned residents that they were at risk from the coming floodwaters and urged them to leave.

“We’re hoping people will self-evacuate” in affected zip codes, Reynolds said Saturday evening.

The flooding in the Mississippi and Ohio river valleys has forced people from their homes in Missouri, Illinois, Indiana, Tennessee, Kentucky and Arkansas.

Now it has Mississippi and Louisiana under the gun.

The Army Corps of Engineers said that it would open a spillway 28 miles upstream from New Orleans to reduce the volume and velocity of the Mississippi River as the record level of water races south to the sea.

The spillway can accommodate about 1.87 million gallons of water per second, diverting it to the Gulf of Mexico by way of Lake Pontchartrain, and sparing the low-lying city of New Orleans from high waters. The spillway is scheduled to open Monday, the Corps said.

Last week, the Corps of Engineers intentionally breached a levee south of where the Ohio River joins the Mississippi River to help alleviate water pressure on levees throughout the region.

The Corps said the breach would help lower river levels and prevent widespread flooding in communities such as Cairo, Illinois, which sits at the confluence of the two rivers.

CNN’s Marlena Baldacci and Phil Gast contributed to this report.