Low flood risk on the Mississippi River this spring, unless big rainstorms sweep in

After another winter with not much snow, there's little spring flood risk on the upper Mississippi River, according to forecasters with the National Weather Service.

Minor to moderate flooding could still occur if rainstorms move through in the coming weeks, but snowmelt — the single biggest predictor of the river's spring flood risk — looks to be negligible, similar to last year.

"You can think of snow as a charged battery, waiting to be used and run off into the river," said Jordan Wendt, service hydrologist for the National Weather Service in La Crosse. "We don't have much snow to talk about this year."

Unlike last year, though, which began with Wisconsin's warmest winter on record, there were stretches of bitter cold this past winter. Without snow to insulate the ground, frost was able to reach deep into the soil — upward of three feet thick in some parts of northern and central Wisconsin, Wendt said. Frozen soil is unable to soak up rain and snow, meaning future precipitation would instead run off into rivers and streams, increasing flood risk.

That's why forecasters will watch how the river and its tributaries handle individual rainstorms that come through, Wendt said. But it would take quite a few weather systems over time to really raise the flood risk.

Communities along the river saw that last summer. Although last spring's flood risk was also low, thunderstorms and excessive rain in Minnesota and northern Wisconsin in May and June caused rivers to rise, resulting in moderate flooding on the upper Mississippi in June and early July. While the floodwaters weren't close to overall record levels, they did set records for the summer season.

Most of the upper Mississippi River basin is currently in drought, according to the U.S. Drought Monitor. Steady rains over longer periods of time can recharge moisture in the soil, Wendt said, but too much rain at once could overwhelm the soil and also cause runoff into rivers.

Further downstream, the Missouri River is seeing below-normal chances of spring flooding, and the Ohio River has a slightly higher potential for spring floods. Both rivers are major tributaries of the Mississippi.

Madeline Heim is a Report for America corps reporter who writes about environmental issues in the Mississippi River watershed and across Wisconsin. Contact her at 920-996-7266 or mheim@gannett.com.