Residents of southern states along the Mississippi River are bracing for the flooding that has swamped communities from the Ohio River Valley to eastern Oklahoma over the last week, causing thousands of evacuations and killing at least 31 people.Officials in Louisiana are checking levees daily, and Exxon Mobil Corp has decided to shut its 340,571 barrel-per-day refined products terminal in Memphis, Tennessee, as floodwaters threatened to inundate the facility just south of the city's downtown."All that water's coming south and we have to be ready for it," Louisiana Lieutenant Governor-Elect Billy Nungesser told CNN. "It's a serious concern. It's early in the season. We usually don't see this until much later."Workers in southwestern Tennessee were preparing sandbags on Friday in hopes of limiting damage from the Mississippi when it crests at Memphis next week, state emergency management officials said. Officials were also examining levees, to make sure they would hold."We're moving things up high and we've got our generators out and got some extra water," said Dotty Kirkendoll, a clerk at Riverside Park Marina on McKellar Lake, which feeds off the Mississippi.Flooding in the US Midwest typically occurs in the spring as snowmelt swells rivers. Freezing temperatures that have followed the rare winter flooding have added to regional woes.Most of the deaths in Illinois, Missouri, Oklahoma and Arkansas have been caused by people driving into flooded areas after days of downpours. The dead included a central Illinois teenager whose body was recovered on Friday near where a truck in which he was riding was found the day before. Another teen from the truck was still missing.Authorities also continued searching on Friday for country singer Craig Strickland, who had gone duck hunting on an Oklahoma lake during stormy conditions. His friend, Chase Morland, was found dead on Monday.