‘Major’ flooding much more likely in latest forecast

Weather Service says the potential for record-setting floods has increased significantly since last week.




3 minute read

Osceola Landing in July 2016, when the water level at Stillwater was about 685 feet. (National Park Service)

A week ago, the National Weather Service predicted a better-than-average risk of high water during the snowmelt this spring. Now, the agency says its models show a nearly 90 percent chance the river will hit 689 feet at Stillwater.

That’s the stage considered ‘major’ flooding. The possibility of seeing 689 feet this spring increased by about 40 percent from last week’s forecast.

The black line shows the probability of reaching certain flood stages throughout the snowmelt season. (National Weather Service)

At 689 feet, the river would be six feet higher than the stage when a no-wake zone is implemented. It would be three feet above the stage at which the Stillwater Lift Bridge might close to traffic if it was still being used for vehicles.

Essentially, it could mean historically high water, with a good chance of breaking into the top seven in recorded history. It would be the highest crest in nearly two decades.

194.1 ftApril 18, 1965
292.3 ftApril 27, 2001
392.2 ftApril 16, 1969
491.1 ft
April 16, 2001
590.45 ftApril 12, 1997
689.7 ftApril 14, 1952
787.9 ftJune 28, 1993

The greatest possibility for high water will be the first few weeks of April.

Water in waiting

The updated forecast and the potential for flooding was informed by new information about the amount of water contained in the deep snow spread across the St. Croix River watershed.

The Army Corps of Engineers has deployed a team of technicians across the region to sample the snowpack and measure how much water is contained in it. The data provides important insights for flood forecasts.

The team will begin in Forest Lake, Minnesota, and make a counterclockwise trip around the region. This area includes most of Minnesota and western Wisconsin. Additionally, Corps of Engineers park rangers will be taking snow surveys in the Mississippi River Headwaters region. Surveys in North Dakota have already been completed.

The snow survey process involves going to a predetermined location, collecting snow through a tube and weighing the melted snow to determine water content.

Corps annual Snow surveys provide flood forecast data ahead of spring thaw, Feb. 27, 2019

The flood forecast would also take into account the major snowfall expected to hit the region again this weekend. From 7 to 13 inches of wet snow are predicted fall across the St. Croix watershed this Saturday and Sunday.

“The most probable track of this particularly intense snow will be … roughly from southwest MN, to east central MN and the Twin Cities, to parts of northwest and west central WI.”

Predictions lead to preparations

Flooded buildings in Afton in 2001, the second-highest flood in recorded history. (Courtesy city of Afton)

The potential record-setting crests could cause problems for communities along the lower river. Officials once again reminded residents that there may still be time to buy flood insurance.

In Stillwater, the city announced all parking lots near the river would be closed on March 18 to allow workers to start preparing for flood control. A Facebook group was also launched to help organize volunteers if needed, and already has nearly 800 members.

Afton mayor Bill Palmquist said his city is preparing, including plans to use new pumps. There is at most a 10 percent chance the St. Croix could hit 695 feet, which would overcome the city’s levees and dikes.

“It looks like our new flood control system will get its first real test this spring,” Palmquist wrote on Facebook. “Our old pumps, if we had all three going at once, pumped 11,000 gallons per minute. Our new system can handle 30,000 GPM.”

Palmquist added that local residents should hope for warm days and cold nights this spring to moderate the melt.