Sven Sundgaard's Minnesota winter forecast: Snow is coming

If you’re hoping for a repeat of the record mild winter of last year, you’re likely out of luck. But, I also don’t think we’ll have a ‘polar vortex’ winter like 2013-2014, which is the last winter that brought real cold in terms of the frequency of the arctic cold snaps and low average temperatures compared to modern averages.

Let’s start with the ‘official’ forecasts from NOAA, which many of you have already seen. The December-January-February outlook (meteorological winter) has the look of a pretty typical weak La Niña pattern.

Higher odds than not of colder than normal conditions are forecast from western Minnesota through the Pacific Northwest, Canadian prairie provinces into Alaska.

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There’s also the potential for above normal precipitation in those similar areas into the Great Lakes.

The climate change factor

As usual, I like to break down what are the main factors likely to affect our winter weather pattern. The first, which is present every season, is climate change. Winter average temperatures are some of our fastest warming. What’s average now is quite different than 50 years ago. This plays into human psychology some. I remember the winters of 2020-2023, when we had that rare ‘triple dip’ La Niña, people complained that it was a cold winter, though I'd wager most of those people were under the age of 35 and don’t remember ‘real winters.’ The table below sets it out quite starkly. If we look at winters since 2010 and line them up compared to the modern average (2010-2024), normal average (1991-2020), and the historic average (1961-1990) of 50 years ago, it's very obvious.

Notice that the only ‘real’ winter in the bunch is the winter of 2013-2014. That’s the only one that truly stands out as a ‘real, cold’ winter as far as temperature on a historic basis.

Even when we compare winters to the normals we’re currently using of the 1991-2020 average (which is updated every decade as we shift forward in time), 8 of the 14 have been above and 6 below. Notably, only 1 of the 3 ‘triple dip La Niña’ winters ended up colder than normal. This is why I always say to be careful with the ‘rules of thumb’ when referring to La Niña patterns.

Now, let’s adjust this chart based on the 4 to 5 degrees of warming over the past 5 decades. You’ll notice something very apparent.

Subtract that warming and we get almost a 50-50 split of above and below normal temperatures. In other words, winters that are cooler compared to the recent decade or two, and feel colder to us because we’re adjusting to modern, warmer winters, would have been normal without climate change.

The reason I bring that up is that the old thinking of ‘colder, snowier winters’ in La Niña patterns doesn’t fit well anymore. If we take climate change out of the equation, then yes.

Polar vortex wrench

The other complicating factor is that a weak La Niña is forecast and the recent shift in the forecast is for it to possibly shorten in duration as well. How will a weaker, shorter La Niña impact our winter?

I did a statistical analysis in a recent article and found that while it does matter if an El Niño is weak or strong, there isn’t much difference on our pattern between a weak or strong La Niña. In other words, we could still have a cold winter in a weak El Niño but almost never in a strong one. Weak and strong La Ninas alike seem to equally make for colder than normal winters overall.

One way that La Niña may impact winter temperatures is by way of disrupting the stratospheric polar vortex. I’ve written about how the polar vortex impacts winter and spring weather, sometimes extensively. Essentially, a strong polar vortex leads to stability, keeping the coldest air locked up near the pole. A weak polar vortex leads to unstable air masses, with cold air escaping into North America and Eurasia. In La Niña years, there’s about a 27% increase in these polar vortex disruptions which tend to impact our late winter and early spring temperature patterns.

One can find hints of this potential in some of the model forecasts for winter temps and precipitation. If a polar vortex disruption is to occur, it’s usually mid winter and can take a couple weeks to impact weather in mid latitudes in our lower atmosphere.

Winter weather forecast enthusiasts have made much noise about how the polar vortex is off to a weaker start this fall and the impacts it could have for the winter, but it appears the polar vortex has caught up and is forecast to continue to strengthen at normal levels.

Recent research has shown that weaker, less stable polar vortices are becoming more common with climate change. That’s because the arctic is warming faster than mid latitudes, decreasing the strength of the jet stream that blows between the air masses, making for more wobbly and highly-amplified patterns (i.e. extreme warmth very far north and extreme cold pushing far south and precipitation implications in between).

This also explains how occasionally (especially in February) we’re getting odd bouts of extreme cold in otherwise increasingly warmer winters. Think of Texas in February 2021. Overall, Februarys are getting much warmer for most, but they are more and more anomalously cold episodes or hiccups in the temperature trends.

What say the models?

The forecast models aren’t very helpful as some are showing warmer than normal winter temps and some are showing colder temps. They are also mixed on winter precipitation. Here’s a sample of models for temperature anomalies (top images) and precipitation anomalies (bottom image):

The Canadian model (left) definitely shows a La Niña signature pattern: colder than normal and snowier than normal. The European (center) and NMME (right) show a much weaker La Niña pattern signature with colder temperatures confined more west/northwest and basically a wash for precipitation. Importantly, all three show the influence of La Niña but at different degrees.

In summary: Sven's take on the upcoming winter

Alright, with all this in mind, I think we’ll end up with a winter pretty close to the 1991-2020 average climatological normal for temperatures. Of course after the record-warm winter last year and the fact the most recent decade is warmer on average than the 1991-2020 normal, this will feel like a ‘real’ winter to many as a result.

We can anticipate more normal outbreaks of cold, especially late January into February and March.

I think we may see slightly above normal snowfall, too.

We average 52 inches of snowfall in a winter, so I’d anticipate us landing in that 50 to 60 inch range. Interestingly, only 6 of the past 15 winters have seen normal or above norma snowfall. The real doozy of course being the winter before last (2022-2023) with 90.3 inches.

The thing I will be watching closely however is the polar vortex as we get into December. If we get a big disruption/weakening event, that could really unleash some February cold air and create ‘snow globe,' too. It might even be enough to pull down winter average temperatures to slightly below normal levels.

I also think this winter will get a late start, keeping with trends of recent years and given just how much heat is still in North America. It’s taking longer and longer to cool things off for winter.

That means December will likely be mild this year, but then January is more likely to be normal and February, colder than normal.

The advantage to significant cold outbreaks in February is that it could get that out of the way instead of creating one of those miserable years where the polar vortex implodes in March or April, making for a nasty cold, snowy April pattern.

Either way, if you’re a winter enthusiast, I’m cautiously optimistic we could have a decent winter for recreation. It may get a late start but it could be ideal, especially mid to late winter.