Frequency of blizzards in the United States could decrease in coming decades, study finds

Vehicles in ditches and medians. Nights without electricity or heating. Injuries sustained. Lives lost. For those in the Midwest, where the frying pan of summer gives way to the snow globe of winter, blizzard scenes are familiar in their frequency. Of the nearly 13,000 blizzards in the United States documented between 1996 and 2020, more than 10,000 hit the Northern Plains and Upper Midwest.

But the average number of blizzards could decline due to lighter snowfall and milder winds in coming decades, according to a first-of-its-kind study from the University of Nebraska-Lincoln published in the journal Environmental Research Letters.

Using the same models used by the Intergovernmental Panel on Climate Change, Liang Chen of Nebraska predicts a decrease in blizzards in the United States through the end of the 21st century. Chen recently presented his findings at the 104th annual meeting of the American Moasting Society.

“Blizzards have a huge impact on a lot of our daily lives: infrastructure, transportation,” said Chen, an assistant professor of earth and atmospheric sciences at Nebraska. “When it comes to planning for climate change, people want to know: In the future, how will these blizzards evolve due to global warming?

“But there are no studies based on climate simulations that examine how these changes will evolve in the future. The main reason is: it’s difficult to quantify.”

The National Weather Service defines a blizzard as a winter storm characterized by sustained winds greater than 35 mph and snow that limits visibility to less than a quarter mile, for at least three consecutive hours. However, due to the difficulty of determining visibility, blizzards have proven difficult to capture using climate data alone, which also inhibits the ability to predict them via climate models.

Thus, the National Weather Service traditionally relies on eyewitness observations to confirm that a blizzard has occurred, compiling the date, location, duration, and other details of observed storms into a database .

Until Chen and his then-advisor, Ahmani Browne, had a thought: Maybe combining daily snowfall and wind speed data, even without visibility readings, could quantify a blizzard . When the researchers compared observations of blizzards with days characterized by both heavy snowfall and sufficiently strong winds, they found substantial agreement between the two, enough to consider the latter a reasonable way to identify winter storms. And after integrating their resulting algorithm into IPCC climate models, Chen and Browne found that the models’ simulations also matched historical observations.

After validating their approach in the past, the duo oriented it towards a short and long term future: 2030-2059 and 2060-2099, respectively. To account for global warming, the researchers included two estimates of future greenhouse gas emissions, one generally considered intermediate and the other more akin to the worst-case scenario.

In both emissions scenarios and over both time periods, the models suggest a gradual decrease in the number of blizzards relative to their frequency from 1996 to 2020, not only in the Midwest, but also in the Northeast. If that happens, Chen said, the trend will come from the projected decrease in the average number of days with extreme winds and days characterized by extreme snowfall, which would reduce the chances of the two elements combining to produce a blizzard.

Iowa, for example, could potentially see 10 fewer strong wind days per year, while Nebraska, the Dakotas, Kansas, Minnesota and other neighboring states are also expected to see a drop in the number of windy days. Part of this could be because the Arctic is warming faster than the Tropics, dampening the so-called temperature gradient that contributes to wind, Chen said.

Along the same lines, global warming will likely break at least some of the daily temperature windows needed for snow, even though winter precipitation overall is expected to increase in the Northern Plains. And given that an increase in greenhouse gas emissions generally results in a greater increase in average temperature, the higher emissions scenario predicts a greater decline in the frequency of blizzards between 2060 and 2099.

“Due to the higher temperature, precipitation will fall on the ground as rain rather than snow,” Chen explained. “So even if precipitation increases overall, your snowfall will decrease.”

“We’ve never had a blizzard.”

The researchers stressed that their study made no claims about the intensity of future snowstorms. Whether the storms could intensify, weaken or neither is among many questions still unanswered. Chen himself plans to study why the number of blizzards increases or decreases so often from decade to decade, both in the past and, if the simulations are accurate, in the future.

This is not what a young Chen would have expected to pursue.

“It’s funny, because I was born and raised in central China,” he said, “where we never had a blizzard.”

Perhaps that’s why Chen remembers the first experience he had, during the winter of 2015-2016, shortly after moving from Texas to Washington, DC. He and his partner, a native of the Lone Star State, were living in an apartment when they learned of a blizzard coming. Chen’s partner suggested buying a shovel.

“I asked myself, ‘Do we really need this?’ I was too naive to pick up the shovel,” he said. “Our cars were stuck in the parking lot for two days, until we finally borrowed a shovel from our neighbors and dug them out.”

Now the former novice is also starting to work with the Nebraska Department of Transportation to study exactly how harsh winter conditions affect road conditions.

“Most of my previous research focused on extreme summer events, such as heat waves, drought and heavy precipitation,” Chen said. “But harsh winters also have an impact, particularly in Nebraska, and we are interested to see its trajectory in a warming climate.

“I hope our study can provide a good understanding of winter extremes and benefit our local community.”