Missouri towns along the Mississippi River and its tributaries should brace for the prospect of potentially serious flooding this spring, in large part because of an unusually snowy winter to the north.

The National Weather Service office in suburban St. Louis on Friday released its spring flood outlook for eastern Missouri and a portion of southern Illinois. The outlook cites a high risk of major flooding along the Mississippi, Missouri and Illinois rivers.

Hydrologist Mark Fuchs said snowpack and soil moisture levels are unusually high in Minnesota, Wisconsin and Iowa. As that snow melts when the weather warms, much of the water ends up in the Mississippi and the rivers that feed into it.

Even an average amount of spring rain could cause major flooding.

"The bottom line is rainfall," Fuchs said in an interview. "If we get a decent amount of rainfall this spring, the odds of significant flooding along the Mississippi in particular are really high."

The flood outlook uses statistical models based on decades of data collected from along the rivers. Fuchs' evaluation looked only at the region covered by the weather service office near St. Louis.

Minor flooding is "a virtual certainty" at Missouri points that include Hannibal, Louisiana and Clarksville. St. Louis has a 91 percent chance of minor flooding, a 77 percent chance of a moderate flood and a 44 percent chance of a major flood, Fuchs said.

Major floods have become more common in recent years. In Hannibal, Mark Twain's hometown and a popular tourist destination, six of the 10 worst floods on record have occurred since 2001, including four since 2013. A flood wall protects the Twain sites and the rest of downtown.

Parts of the region in southeast Missouri and southern Illinois have already experienced minor flooding that has forced road closures. Several Mississippi River towns are currently experiencing minor to moderate flooding south of Missouri.

"The lower Mississippi is already under the gun," Fuchs said.

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