Mississippi floodwaters expected to affect areas downstream into June

While water levels will fluctuate, flooding is likely to continue along a portion of the Mississippi River and perhaps others over the central United States into June as rounds of excessive rain continue.

High water levels will continue to put pressure on earthen levees for an extended period in some cases. Where drenching rain falls at the same time, there will be an increased risk of levee failure.

"We expect areas of heavy rain to shift around from north to south and perhaps back over the Central states through May," according to AccuWeather lead long-range meteorologist Paul Pastelok.

"We are not out of the woods yet in terms of the risk of widespread heavy rain and its consequences in terms of flooding over the North Central states this spring."

Flooding to continue

This week, a slow-moving storm will bring enough rain to aggravate existing flooding along the middle portion of the Mississippi River, as well as much of the Illinois River and the lower portion of the Missouri River.

How much rain falls from Kansas and Nebraska to Wisconsin and Illinois will ultimately determine the new surge of runoff and downstream flooding.

While the Mississippi has crested and will generally recede in Iowa, rounds of rain into Thursday may slow the rate of recession, or may produce a secondary crest this weekend into next week.

That crest, should it occur, is likely to be at moderate to major flood stages, but will be lower than the historic levels achieved over the past couple of weeks.

Some waterways, such as the Des Moines River, may also react to the heavy rain this week by briefly surging above flood stage.

There is some positive news for flooding concerns over the North Central states in the mid-range.

"We expect enough of a pattern change to bring a break from widespread heavy rain events from portions of the central and northern Plains to part of the Midwest late this week into much of next week," Pastelok said.

This break should be enough to allow the middle and upper portion of the Mississippi and others over the North Central states to continue to recede significantly for a time.

"That dry break should be enough to allow many farmers to get into the fields to plant over the North Central states," according to AccuWeather agricultural meteorologist Dale Mohler.

Exceptions will be where the Mississippi has broken through the levees and flooded farmlands. These areas may take a month or more to dry out, assuming no additional rainfall.

Pastelok offered some words of caution about a lasting end to heavy rain and the risk of flooding over the North Central states.

"There are some some long-range indications of big rain later in May for portions of the central Plains to the Midwest," Pastelok said.

Long-term flooding

The dry air coming to the North Central states will work into part of the South Central states, but not everywhere.

There is the potential for a new round of heavy rain to erupt from parts of central and coastal Texas late this week and then spread across the lower Mississippi Valley this weekend.

A portion of the lower Mississippi River and a few others in the region such as the Trinity and Sabine were already above flood stage from prior rainfall and runoff early this week.

The Mississippi River at Baton Rouge, La., was at major flood stage and rising as of Tuesday.

As heavy rain from the late-week downpours and thunderstorms cascades through the watershed, higher water levels are likely with the potential for major flooding in some cases this weekend into next week.

In the case of the lower Mississippi River, flooding is likely through the end of May and into June. This, as the surge of water along the middle portion of the Mississippi moves in while more rounds of rain occur at the local level.

As is always the case, there is a delayed reaction to excessive rain and dry spells on very large rivers, such as the Mississippi.

It is likely to take a month or more for the crest occurring along the Mississippi River in Missouri and southern Illinois to work downstream through the delta region, even after it stops raining.

Flooding along the Mississippi River is rarely short-term because of its shear volume and flat terrain. During the Great Flood of 1993, which still holds record crests in many areas, it took seven months for flooding to run its course. This year, flooding along portions of the Mississippi River has been ongoing since the middle to latter part of the winter and has challenged those set in 1993 in some locations.