Relentless Storms Trigger Mississippi River Flooding

Round after round of thunderstorm complexes have not only put a dent in long-term drought in parts of the Plains but also have the upper Mississippi River on the rise.

Rainfall between two and three times that of normal has fallen on portions of the northern and central Plains so far this June with near normal to double the average rainfall for the month in many areas farther south. Additional rounds of showers and thunderstorms are in the forecast through the coming week.

A large portion of the central and northern Plains will finish June with over a foot of rain.

The greatest amount of rain from Sunday to Monday will focus across Kansas and southern Nebraska, where an average of 2 to 3 inches is likely and the ground will absorb much of the water. However, another 1 to locally 2 inches of rain can fall over saturated areas of Iowa, Minnesota, Wisconsin and Illinois, where much of the rain will run off into streams and rivers.

Some beneficial rain will reach hard-hit drought areas of Oklahoma, northern Texas, western Kansas and and southeastern Colorado into next week.

The rain has been and will continue to be a frequent visitor to the northern part the Ogallala Aquifer. The underground water supply extends from Nebraska to western Texas.

The complexes of thunderstorms will also bring incidents of severe weather in parts of Kansas, Colorado and Oklahoma on Sunday. There is the potential for damaging wind gusts, large hail and isolated tornadoes.

Since much of the rainfall will be concentrated to a several-hour period during thunderstorms Sunday into Monday, there is a risk of flash and urban flooding no matter what the drought status may be.

The Situation on the Mississippi River

Enough rain is forecast to fall on tributaries of the upper Mississippi River to continue to cause the waterway to rise into next week.

Hydrologists with the National Weather Service are projecting the Mississippi to reach major flood stage at St. Paul, Minnesota, during much of the coming week and similar levels at Burlington, Iowa, during late June.

Mississippi River levels will continue to rise during late June into early July farther downstream at Quincy, Illinois, and eventually St. Louis but lock and dam operations will significantly mitigate these levels.

Low-lying areas not protected by levees, such as farmland, waterfront properties and some roadways, will be inundated once river levels surpass flood stage.

Heavy rainfall over the past couple of weeks has pushed the Big Sioux and Little Sioux rivers out of their banks in Iowa.

At Akron, Iowa, the Big Sioux River crested at a record 25.58 feet on Wednesday. The Little Sioux River at Linn Grove, Iowa, nearly equaled a record high level on Wednesday.

Minor to moderate flooding is forecast along portions of the Red River (of the North) at Fargo and Grand Forks, North Dakota. Minor flooding is projected along portions of the Missouri River in Nebraska and Missouri.

No significant impact to barge traffic is expected from St. Louis on to the south at this time. However, if heavy rainfall continues over the central Plains and were to expand farther east over the Midwest, the situation could change in the weeks ahead.

As long as there is enough separation between individual complexes of thunderstorms farther east over the Midwest, water levels on the major rivers, such as the Ohio and lower Mississippi, should remain fairly stable or well within the operating range of barges.