EAU CLAIRE, WISCONSIN — Two separate storm systems are set to combine for widespread 2 to 4 inches of rainfall across the Upper Midwest by Saturday, September 19, according to a National Blend of Models, or NBM, forecast valid through 7:00 p.m. CT that day. The first system is already moving through the region and bringing rain over the next 36 hours, forecasters said, with a second system tracking in Friday into Saturday to add a second round of heavy rain on top of already-saturated ground across parts of Minnesota, Wisconsin and Iowa.
Two Storm Systems Combine for Widespread 2 to 4 Inch Rainfall Through Saturday
Forecasters say the combination of back-to-back systems is the key reason rainfall totals are stacking up so high across such a broad footprint of the Upper Midwest heading into the weekend. Rather than a single quick-moving system dropping an inch or two and exiting, the region is set to see two distinct rounds of rain layer on top of one another over a roughly five-day window, pushing widespread totals into the 2 to 4 inch range by the time the second system finally clears out on Saturday.
First System Already Moving Through With Rain Expected Over the Next 36 Hours
The first of the two systems is already in progress, moving across the Upper Midwest and expected to continue producing rain over the next 36 hours. That initial round is forecast to lay down a meaningful base of rainfall across much of Minnesota, Iowa and Wisconsin before any break in the action, setting the stage for the ground to already be wet and less able to absorb additional rain once the second system arrives just a few days later.
Second System Tracks Through Friday Into Saturday Across the Region
Once the first system clears, forecasters say a second storm system is set to move through beginning Friday and continuing into Saturday, adding another substantial round of rainfall on top of totals from earlier in the week. It is this second system, tracking directly over ground already softened by the first round, that pushes the NBM forecast’s highest totals well past 3 inches across the hardest-hit corridor, with the full 7:00 p.m. CT Saturday forecast representing the combined output of both systems together.
Eau Claire, Rochester and Des Moines Lead All Totals at 3.5 Inches or More
The single highest forecast total on the map belongs to Eau Claire, Wisconsin, at 3.74 inches, with Rochester, Minnesota, close behind at 3.65 inches and Des Moines, Iowa, at 3.57 inches. Rounding out the top tier, La Crosse, Wisconsin, is forecast for 3.33 inches, Wausau, Wisconsin, for 3.26 inches and Cedar Rapids, Iowa, for 3.41 inches, marking a core corridor stretching from southeastern Minnesota through western Wisconsin and into eastern Iowa as the epicenter of this week’s heaviest rainfall.
Minneapolis, Mankato, Appleton and Davenport See Widespread 2 to 3 Inch Totals
Just outside that top-tier core, a wide band of communities is forecast to see totals in the 2 to 3 inch range. Minneapolis is forecast for 2.66 inches, with Mankato, Minnesota, at 3.03 inches and Worthington, Minnesota, at 2.07 inches. To the east, Appleton, Wisconsin, checks in at 2.46 inches, while Davenport and Rockford both land at 2.01 inches and Duluth, Minnesota, is forecast for 2.01 inches as well. Farther west, Omaha, Nebraska, rounds out this tier at 2.46 inches.
Lighter Totals of an Inch or Less Expected Across the Dakotas and Central Nebraska
Rainfall totals taper off considerably heading west into the Dakotas and Nebraska, where the NBM forecast shows far lighter amounts. Bismarck and Fargo, North Dakota, are both forecast for just 0.42 inches, with Linton, North Dakota, at only 0.17 inches. Farther south, Pierre, South Dakota, is forecast for 0.7 inches and Mobridge for 0.27 inches, while in Nebraska, North Platte comes in at 0.44 inches and Kearney at 0.7 inches, reflecting how sharply the heaviest rain corridor is concentrated toward the eastern half of the outlined region.
Great Lakes Communities From Milwaukee to Traverse City See More Modest 1 to 2 Inch Totals
Along the Great Lakes, forecast totals settle into a more moderate 1 to 2 inch range for most communities. Milwaukee is forecast for 1.25 inches, Madison for 1.95 inches and Chicago for 1.15 inches, while farther north, Traverse City, Michigan, checks in at 1.61 inches, Ludington at 1.83 inches and Marquette at 1.3 inches. Grand Rapids and Lansing, Michigan, come in lighter still at 0.89 inches and 0.67 inches respectively, marking the eastern edge of the widespread heavy rainfall event as totals ease closer to the Michigan shoreline.
