Major river flooding expected across north-central US as thaw ramps up
The combination of tremendous snowfall over the winter and the ongoing spring thaw has set into motion a flooding event along the upper Mississippi River and others in the region that cannot be stopped. Heavy spring snowfall, rapid thaw events and additional rain will continue to make matters worse, AccuWeather meteorologists warn.
This snow season ranks among the top for portions of Minnesota and Wisconsin. Minneapolis has received 90.3 inches of snow since the early autumn, which is the third-highest amount for a single season on record there. Meanwhile, Duluth, Minnesota, could end up with its snowiest season on record should the snowfall total sneak past the 135.4 inches from 1995-1996. As of Thursday morning, the record had officially been tied.
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Summerlike warmth last week, which featured temperatures in the 70s and 80s, caused a large amount of the snow from the winter to melt. That snow cover contained anywhere from 5 to 15 inches or more of water. The runoff has already worked through the smaller streams and into the secondary rivers and is on its way to the largest rivers in the region.
As AccuWeather's long-range forecasting team, led by Senior Meteorologist Paul Pastelok, warned about early this winter, major flooding will unfold along the Red River of the North, with at least moderate flooding along the upper portion of the Mississippi River.
At Fargo, North Dakota, the Red River is projected by National Weather Service (NWS) hydrologists to surpass the major flood stage threshold of 30 feet this weekend. Forecasters say the Red River will continue to rise at Fargo into the last week of April.
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Fargo Mayor Tim Mahoney told AccuWeather that the city deals with a "major" flooding event every 4-5 years, and officials are busy preparing for this year's flood potential. "Last week, we made 200,000 sandbags ... we're very efficient around the [city], people come help us out," Mahoney said, adding that volunteer students from local schools also aid in the sandbag-making process.
Other rivers where major flooding is possible include the Minnesota River near Montevideo, Minnesota, and the St. Louis River near Scanlon, Minnesota.
A quick flip to much colder and snowy conditions occurred this past weekend.
The consequences of a storm that dropped as much as 1-2 feet of snow from this weekend to Monday on large portions of Minnesota and Wisconsin will have to be dealt with, AccuWeather Meteorologist Matt Benz said, noting that the heavy, wet nature of the recent snow will only worsen the flooding.
"There is the issue of the 1-2 inches of water that the existing fresh snow cover contains, which will soon work into area streams and rivers," Benz said. "There is also the prospect of a new storm which may not only bring a rapid meltdown of that snow but also throw more even water on the situation," Benz said.
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The new storm, which will last through Thursday, will drop a general 1-2 inches of rain and could bring localized amounts between 2 and 4 inches. The combined fresh snow cover and rain from the storm could unleash 2-6 inches of runoff into area streams and rivers, in addition to any melting from the previously existing snowpack. While last week's warmth melted a sizable percentage of this winter's snow, some still remains across portions of North Dakota and far northern Minnesota.
This flooding is not shaping up to be the worst on record for the upper Mississippi River and all of its tributaries; however, it could rank high in severity as many locations are expected to experience major flooding.
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"Some spots along the Mississippi, especially south of St. Paul ... could be the highest crest on the Mississippi since 2001, so over 20 years since we've seen water levels like this," AccuWeather Snow Expert Matt Benz said.
"The worst flood event for the upper Mississippi watershed as a whole was probably 1965," Benz said. "At La Crosse, Wisconsin, the Mississippi crested at 17.89 feet that year. Farther north, the river reached a record 26.01 feet at St. Paul, Minnesota."
As of Monday, NWS hydrologist projections take the Mississippi to 15.3 feet at La Crosse - the fourth highest on record - later this weekend. However, these projections are subject to change and may not take into account the full impact of the melting snow from the recent storm and the upcoming rain and the rate of meltdown that occurs.
Should the Mississippi reach the projected major flood crest of 18.4 feet at St. Paul by this weekend, it would be the highest level recorded there since March 31, 2019, when floodwaters reached 20.19 feet. Rising water on the Mississippi forced city officials in St. Paul to close parks, facilities and some road systems in the region this past weekend.
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"Levees added in recent years and decades will help contain the rivers in many of the towns and cities," Benz said. "However, days and perhaps weeks of nervous river watching are in store."
Extensive flooding of agricultural areas along the Red and upper Mississippi rivers may be unavoidable. Once water enters the vast areas of flat terrain in portions of the northern Plains, it may take many weeks for the water to recede and the ground to dry out.
Long-lasting flooding could impact travel and shipping operations in the region. Some roads and rail lines will be closed due to high water. Interstate 29, which parallels the Red River in North Dakota, could be especially impacted if flooding is particularly severe.
A significant amount of transportation of grains and goods takes place on the upper Mississippi River from St. Louis to St. Paul. High water will likely force locks along the river to shut down for a time, Benz warned.
Current hydrology forecasts suggest that moderate to major flooding may occur in parts of Iowa and northern Illinois and moderate flooding farther south along the river in Missouri and Illinois.
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The Mississippi River at Rock Island, Illinois, is projected to reach 18 feet, which is major flood stage, next Tuesday, April 25.
It may take several weeks for the crest on the Mississippi River to work downstream to the Ohio River confluence and a month or more for points farther south.
Typically, the surge of water diminishes farther downstream along river systems, provided no additional rain develops along the way.
Unless the surge of water coincides with heavy rain over the next month or two along the Ohio River, the lower part of the Missouri River and other rivers in Missouri, Arkansas, Kentucky and Tennessee, anything more than minor to moderate flooding seems unlikely over the lower Mississippi River, Benz said.
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