Melting record snowpack, rain expected to cause flooding

Storm drain catch basins are backing up on streets around the Twin Cities.
Storm drain catch basins are backing up on streets around the Twin Cities, leaving ponds of meltwater in the street, like this corner of Finn Street in St. Paul on Sunday.
Tim Nelson | MPR News file

More than an inch of rain is forecast for much of Minnesota Wednesday and Thursday including the Twin Cities metro area. That normally would not be a cause for concern, but with the heavier-than-normal snowpack starting to melt, forecasters say there could be some flooding of roads across the region.

Many Minnesotans have been longing for spring, not least because of the heavy snowfall — a record-setting 39 inches of snow fell in the Twin Cities last month. Temperatures are expected in the 40s on Wednesday and Thursday.

Now all that meltwater needs somewhere to go, and its options are limited. Thick frost is preventing a lot of it from soaking into the ground. With rain falling, the chances for evaporation don't look too good either. And many of the normal drainage paths — creeks and storm sewers — are blocked with ice and snow.

The Minnehaha Creek Watershed District says it is tracking the potential for flooding on the creek that flows through south Minneapolis, St. Louis Park, Hopkins and Minnetonka. Most years, rain comes after the creek is thawed and flowing, and the snowmelt is well underway.

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"Having this 1 or 2 inches of rain on top of a heavy snowpack is a little bit unknown for us and we're trying to forecast and predict to the best of our ability what we think might happen," said Tiffany Schaufler, project manager for the Minnehaha Creek Watershed District.

Schaufler said she's been in close contact with National Weather Service forecasters, who expect an inch and a half of rain to melt about an inch of water out of the snow. Ice jams are a concern, but she says the latest predictions are below the 100-year flood level, so people don't need to fill sandbags quite yet.

Another concern this week is flooding along low-lying roads. Kevin Gutknecht, a spokesperson for the Minnesota Department of Transportation, says Interstate 35W between Bloomington and Burnsville is a frequent trouble spot in wet weather, as are many roads in the Red River Valley.

"We'll be out watching the roads. We'll be doing our best to keep drainage areas clear, culverts and things like that, as well as storm drains along the roadway. And like everybody else, just watch the weather and see what happens," Gutknecht said.

The precipitation is expected to taper off by late Thursday. Daytime highs into next week are forecast to be in the mid-30s, but nighttime lows will be below freezing. That means the snow isn't likely to melt all at once, but the wet streets and sidewalks could refreeze, making for some slippery morning commutes.