Despite a winter-long buildup of snow, particularly in eastern Minnesota, chances of serious spring river flooding across the region are slight, according to a Thursday update by the North Central River Forecast Center.
Probabilities of flooding that would close roads or bridges or have other widespread public impact are less than 25 percent at cities along the Minnesota and Mississippi rivers and throughout southeastern Minnesota and western Wisconsin. Along the flood-prone Red River, Fargo-Moorhead's chances of seeing a flood approaching even the level of last year's anticlimactic peak is less than 20 percent.
Forecast Center hydrologist Steve Buan noted that while metro residents are still hemmed in by deep snow, areas to the west have received less snow, meaning that western tributaries of the Minnesota and Mississippi rivers won't be sending massive volumes of spring snowmelt into those major rivers. A melt of deep snow to the north and east of the metro, however, could produce some high water.
At Stillwater, for example, it's virtually certain that officials will invoke a no-wake zone for boaters on the St. Croix River, and there's a 90 percent chance the Stillwater Lift Bridge will be closed. But the chance that Hwy. 95 between Afton and Bayport might close is less than 20 percent. That stretch of highway runs under Interstate 94.
In Fargo-Moorhead, some waterfront and park flooding is possible, along with some minor street and bridge closings. But a flood that would prompt sandbagging has been given a 10 percent likelihood chance. Snow cover across northwestern Minnesota and eastern North Dakota is about normal, and its water content slightly below normal, forecasters indicated.
Buan said a key wild card in the outlook is thick river ice. If it breaks up in a way that produces major ice dams, unexpected flooding could happen.
On Lake Pepin, U.S. Army Corps of Engineers workers making their first ice-thickness measurements of the season on Feb. 27 drilled as far down as their auger would go at one milepost — 30 inches — and never hit water, said spokesman George Stringham. Measurements along 17 miles of the lake, which is a widening of the Mississippi River southeast of the Twin Cities, averaged 24 inches — 5 inches thicker than the season-opening measurements last year. The next measurement is scheduled for next Wednesday.
The flood outlooks, which incorporate conditions as of March 3 and 60 years of actual spring weather, are considered valid through June 3.