River flooding may rival records in Mississippi Valley into January

By AccuWeather

Flooding in the upcoming days and weeks following a tremendous December rainfall could be one for the record books in the Mississippi Valley.

Major flooding along the Mississippi, Illinois, Ohio, Missouri, Arkansas and Meramec rivers will have communities dealing with long-duration high water. Freezing temperatures will cause some flooded areas to turn icy and will add to the challenges.

See images from areas hit by flooding:

Flooding on the middle portion of the Mississippi River and its tributaries may reach levels not seen during the winter months since records began during the middle 1800s.

Water levels could rival the mark set during the summer of 1993 and spring of 1995 and 2011 in some cases. Chester and Cape Girardeau, Missouri, as well as Thebes, Illinois, could experience record high Mississippi River levels.

As of 11 a.m. CST Tuesday, Dec. 29, 2015, St. Charles County officials had issued mandatory evacuation orders for West Alton, Missouri, as water was topping levees on the Mississippi River.

Springlike flooding occurs amid El Niño pattern

Since December and November have been so warm and so wet, the atmosphere and watershed are behaving more like the spring.

Temperatures over much of the Mississippi Valley have averaged 8-12 degrees Fahrenheit above normal and featured highs in the 60s and 70s during December.

See the effects of the El Niño weather pattern:

During November and December, frequent storms loaded with abundant moisture have delivered rainfall well above average to much of the Mississippi Basin.

The pattern is typical of an El Niño, but rainfall of this magnitude has crossed into uncharted territory for the region.

Since Nov. 1, St. Louis has received more than 18 inches of rain versus the average of 6.50 inches typical for this time frame. St. Louis shattered its December rainfall record of 7.82 inches set during the El Niño of 1982. This December, St. Louis received 11.74 inches of rain.

Farther north along the Mississippi River, Minneapolis has received nearly two and a half times its normal rainfall since Nov. 1.

Just after Christmas the bursts of rain, which amounted to 6-12 inches in some areas, sealed the fate for river flooding.

According to AccuWeather Meteorologist Jim Andrews, "Rainfall is significantly less over the central United States during the winter, when compared to the spring and summer."

"During the wintertime, more precipitation falls as snow over the region, which tends to absorb the runoff and causes river levels to fall."

One thing that is contributing to the amount of runoff is low evaporation this time of the year.

"During the summer months, the sun and heat take their cut out of the rainfall. You don't have that during the wintertime, so the ground can stay wet longer," Andrews said.

While the smaller tributaries of the Mississippi will crest quickly following the tremendous rainfall from the storms near Christmas, the larger tributaries and the Mississippi itself will take an extended period of time to crest and then fall below flood stage.

"It will take weeks or until the latter part of January for the last of the crests to cycle southward to the Gulf of Mexico," Andrews said.

Melting snow along with showers and thunderstorms typically herald spring flooding along portions of the Mississippi River every two to three years.

"What is so amazing about the flooding is that is is occurring with very little or no snowmelt," Andrews said.

Flooding potential to persist

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There is the potential for another round of flooding during the spring of 2016.

"We still have to go through the snowy part of the winter season over the North Central states," AccuWeather Chief Long-Range Meteorologist Paul Pastelok said.

The storm track will shift southward during the winter, but will return northward in the spring with the combination of a thaw and rainfall.

"El Niño may still be strong enough to enhance the strength of the storms and the amount of rainfall during the spring," Pastelok said.

There is some good news in the short-term for those battling flooding and trying to protect their property.

The spread of colder air will shut down the storm track into the middle part of the nation through at least the middle part of the first week of January.

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