Spring flood potential growing across Minnesota

Water-heavy snowfall adding to flood concerns

Snow Water Equivalent Minnesota march 6
Snow water equivalent map from the North Central River Forecast Center, issued on Monday.
North Central River Forecast Center

Updated 6:38 p.m.

This may be a spring to remember in Minnesota.

Frequent heavy snowfall events have already put the Twin Cities into the top 13 snowiest winters on record. Minneapolis-St. Paul International Airport has already logged 74.7 inches of snow this season. Duluth is pushing the 100-inch mark with 99.5 inches already this season.

The amount of water in the snowpack around the Upper Midwest is significant. The latest spring flood outlook from the North Central River Forecast Center shows from 2 to more than 6 inches of water trapped in the snowpack across the Upper Midwest. (See the image above.)

Flood risk is already running above average across our region. That’s a change from just a few weeks ago.

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According to Monday’s forecast center update: “The addition of another 1-2 inches of water into the snowpack (from rain, then heavy snow) has increased the threat in just two weeks.

“Though we have an ample snowpack, drier soils and little frost depth will help alleviate at least some of the snowmelt threat. The threat of seeing major flooding will still depend on what kind of rainfall/temperature patterns we get during the snowmelt.”

Here is the latest available estimate of flood probabilities on the Mississippi River at St. Paul. The black line is the current forecast. The blue line is the historical probability:

Flood probability for the Mississippi River at St. Paul
Flood probability for the Mississippi River at St. Paul.
North Central River Forecast Center

The Mississippi River at St. Paul went from less than 50 percent probabilities for any flooding to at least a 50 percent chance of moderate flooding, the forecast center’s latest report says. Here are the current probabilities:

  • Minor flooding: 68 percent vs. 24 percent normal

  • Moderate: 57 percent vs. 19 percent normal

  • Major: 35 percent vs. 12 percent normal

Here is the latest available assessment for the St. Croix River at Stillwater — the probability of seeing minor flooding now tops 80 percent:

Flood probability for the MSt. Croix River at Stillwater
Flood probability for the St. Croix River at Stillwater.
North Central River Forecast Center

Other probabilities for the St. Croix at Stillwater include:

  • Minor flooding: 86 percent vs. 23 percent normal

  • Moderate: 64 percent vs. 17 percent normal

  • Major: 39 percent vs. 11 percent normal

So you can see the dice are loaded for a higher-than-average probability of flooding this spring.

More snow on the way

Sunday evening’s wet snow added more water to the snowpack. Most forecast models develop another one or two storms in the next 10 days that will likely produce additional heavy wet snow.

It’s still too early to be confident about precise moisture amounts with our inbound snow event Thursday and Friday. But the early runs of the European and American models suggest another three-fourths to 1 inch of moisture is possible later this week.

Precipitation outlook
Precipitation outlook
NOAA, via Iowa Emergency Management

If that happens, it will boost flood risk even further across our region. Some forecast models suggest another shot of moisture around St. Patrick’s Day.

The barrage of atmospheric rivers that have been blasting California with incredible amounts of rain and snow continues to send pieces of that energy toward the Upper Midwest.

The flood risk in California is growing by the day.

The same weather pattern is increasing flood risk at a smaller scale here in Minnesota.

Stay tuned.