Snowplow drivers, city engineers and park supervisors across Minnesota are bracing for heavier snowfalls this winter as they come to grips with the way climate change is producing more volatile weather in the state’s coldest months.
Much as rising temperatures and extra moisture have caused heavier rainstorms in the summer, climatologists say they are causing more weather extremes in winter, too. So even as overall snowfall has declined or stayed relatively flat in recent years, Minnesota is seeing more blizzards and near-blizzards.
This calendar year, for example, St. Paul has declared eight snow emergencies — typically announced for storms with more than 4 inches of snow — compared with the average three to four per year. And 15 of the Twin Cities’ top 20 snowfalls since 1884 have occurred within the past 30 years, including the “thunder blizzard” that shut down much of the metro area last April and 2010’s “dome-buster” that collapsed the Metrodome roof.
“It just seems like we’re getting bigger swings, where it’s either much snowier or much less snowy than before,” said Mike Kennedy, director of transportation, maintenance and repair for the city of Minneapolis. “Last winter there just wasn’t a whole lot of snow at all until mid-February. Then it started snowing and never stopped.”
These snowstorms are hitting even as winter temperatures have steadily climbed over time, said Peter Boulay, assistant state climatologist. “We’re still getting our snow,” he said. “But snowfall is highly variable, not only from winter to winter but within the same winter as well.”
But a shifting climate doesn’t simply mean more blizzards. Minnesota is getting much less snow in November, shortening the season on one end, and more snow in April, lengthening it on the other. And in between heavy storms, skies now tend to be clear and sunny, turning winters into bipolar periods that alternate between mild blue-sky days and extreme snowfalls.
These dramatic swings are hard on winter tourism and outdoor sports venues that depend on reliable snowpack. Ramsey County, for example, has seen enough brown Decembers and Januarys that it’s accelerating a multimillion-dollar plan to install snow-making machines on some of its cross-country ski trails so its parks can retain tournaments, competitions and high school team practices.
A hallmark of a strong winter is a sustained period with at least a foot of snow on the ground, Boulay said. Those winters have been declining steadily. Over the past 20 years, Minnesota had just nine winters when at least a foot of snow accumulated on the ground. That’s down from 13 such seasons over the previous 20 years, Boulay said.
“That deep snow cover is on the decline,” he said. “But when you just count the number of days where we [get] 4 or more inches of snowfall, the 2010s have the most we’ve seen in a while.”
These swings can happen abruptly. Even though it saw relatively little snowfall for the first half of the season, last winter ended up being the most costly in nearly a decade for the Minnesota Department of Transportation (MnDOT). That’s because February blizzards were so strong and snowdrifts were so high that MnDOT had to make the rare call to shut down Interstates 35 and 90, while bringing in trucks from all over the state to clear roadways.
Despite these challenges, the plow patrols remain undaunted. The swings between mild and severe years only reinforce a long-standing MnDOT rule of thumb: Be ready to clear roads in any part of the state from October through April, said agency spokeswoman Anne Meyer.
“In Minnesota, nothing is too unusual, even though every year is unique,” she said. “Plow drivers just have to be — and are — ready to go as soon as October until things really start to warm up. We certainly have a lot of tools in the toolbox to get us through these events.”
Extreme precipitation has become most problematic during the spring, when late snowfalls or early rains compound the rush of melting snow, often triggering severe floods. Minnesota is getting 10 to 15% additional precipitation, or more, during the early spring than it did in the early to mid-1900s, according to the National Oceanic and Atmospheric Administration.
And lately, the state has seen heavy snowstorms and rainfalls in April. As a result, three of the 10 largest flood events in St. Paul’s history have happened since 2011, including a deluge last spring.
Late fall precipitation also jumped by more than 15% throughout the state.
In addition, places like St. Paul seem to be dealing with more “fringe weather” — when rain turns to sleet, sleet turns to snow and then back to rain, said Matt Morreim, street maintenance division manager for St. Paul.
“That’s what happened this Thanksgiving,” he said, recalling the way streets quickly iced up. “What we’ve learned is that we need to be out there immediately. … You can either take care of it immediately, or you’re dealing with it for an extended period after.”