It's September. Signs of a rigorous winter ahead for Minnesota?

La Niña winters skew cold and snowy climatologically in Minnesota.

Snow and icicles in Victoria.
Snow and icicles in Victoria.
Paul Huttner | MPR News 2018

Happy meteorological autumn Minnesota.

September marks the first month of meteorological fall in Minnesota. The months of September, October, and November most closely correlate with the fall season for record-keeping purposes.

I’ve always felt like Minnesota seems to have more of a 4-2-4-2 seasonal climate. Our seasonal patterns often more closely resemble 4 months of winter and summer with a fleeting 2 months of spring and fall. All or nothing.

September is also the month where Minnesotans start gearing up for the inevitable march toward winter. We bask in those last sunny 80-degree days. We pack in those last boating and camping trips. The coming change in seasons is in the back of our minds more often now.

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It was a great summer.

10 13 fall color
Fall color in Chanhassen in 2017.
Paul Huttner | MPR News

La Niña watch

I get this question a lot this time of year.

“Hey Paul, what does the upcoming winter look like?

My answer usually depends on what’s happening in the tropical Pacific Ocean. And this year sea surface temperatures (SST’s) are running colder than average with shades of blue developing in the equatorial Pacific.

Tropical Pacific SST departures from average
Tropical Pacific SST departures from average

NOAA’s Climate Prediction Center keeps tabs on all things climate across the globe. One of the great success stories of seasonal forecasting over the past 40 years is discovering teleconnections between tropical Pacific Ocean temperatures and seasonal climate patterns.

NOAA has issued a La Niña watch for the upcoming fall and winter seasons.

In La Niña winters, the jet stream pattern over North America statistically favors a colder pattern overall across the northern Plains and Upper Midwest.

Typical La Nina winter pattern
Typical La Niña winter pattern

La Niña years statistically favor a colder than average winter overall for Minnesota in about 70 to 80 percent of years.

La Nina temps
La Nina winter temperature trends

There is also a slight bias for above-average snowfall across Minnesota during La Niña winters.

La Nina winter snow
La Nina winter snowfall trends

Long-term climate warming

If the statistical bias toward a colder winter materializes, it will be fighting the longer-term trend of significantly milder winter in Minnesota. Average winter temperatures have warmed more than 5 degrees overall in Minnesota since 1970 due to climate change.

Winter temperature trends
Winter temperature trends for Minneapolis
Climate Central

Minnesota and the Upper Midwest are the fastest warming areas of the country in winter.

Winter warming trends.
Climate Central

It is shaping up to be an interesting battle between opposing forces this winter across Minnesota.