By Michael Griesinger, National Weather Service
All seasons present their own challenges for airport operations in Minnesota, but winter perhaps brings the most. Whether it’s snow or ice making runways and taxiways dangerous, or persistent low clouds shutting down operations at smaller airports for days on end, winter can be a difficult time of year to keep things running smoothly. Although one month of winter is now behind us, we have three more to go. So what does the rest of winter have in store?
To answer that, we need to look at the two key players forcing our weather patterns this winter. One—La Niña—you’re likely familiar with. The other is a bit more obscure—but may be even more important this year.
We’ll start with La Niña. La Niña is a part of the El Niño–Southern Oscillation (ENSO), which describes changes in wind and thunderstorm patterns across the tropical Pacific Ocean. The ENSO has a warm phase, El Niño, and a cold phase, La Niña. During El Niño, the trade winds across the tropical Pacific weaken, which allows warmer-than-normal water to move farther east out into the Pacific Ocean, with tropical convection following suit. During La Niña, the trade winds are stronger than normal, which keeps water in the central Pacific cooler and pushes the tropical convection to the west end of the Pacific (toward Indonesia).
Where the tropical convection ends up during each ENSO phase is key to the weather we see here in North America. During a La Niña phase, the Asian jet stream slows down across the western Pacific, which causes air to converge in the central Pacific. This convergence favors the development of a ridge of high pressure across the central and into the northern Pacific. This ridge forces the jet stream up toward Alaska before it dives southeast across North America, working down the east side of the Pacific ridge. This northwest flow leads to arctic air making frequent runs south out of Canada into the northern United States, resulting in below-normal temperatures across Minnesota.
Now, for something many have likely never heard of—the quasi-biennial oscillation, or QBO. The QBO describes the general direction of winds in the tropical stratosphere, where two phases (westerly and easterly) each last for about two years. This is important because the phase of the QBO drives the strength of the stratospheric polar vortex. During a westerly phase, the polar vortex tends to be stronger. When the QBO is easterly, the polar vortex is more susceptible to breaking down, and when this breakdown occurs in the winter, it tends to push arctic air toward the mid-latitudes—which includes us here in Minnesota. In the fall of 2025, the QBO switched to the easterly phase, which increases our odds for at least a couple of strong arctic outbreaks this winter.
What does all this mean for Minnesota’s weather outlook? During past winters in which ENSO was in its cold phase (La Niña) and the QBO was easterly, we saw more frequent arctic outbreaks and better odds for below-normal average temperatures throughout the entire winter. As a result, the outlook for the rest of the winter favors below-normal temperatures. Regarding precipitation, when winter temperatures are below normal, we typically experience above-normal precipitation—which means more snowfall. What we have for snow cover as we head into March will be key to just how much winter we get that month, but if we start with a healthy snowpack, it will be hard to warm up, and winter conditions may extend into early April. Our best advice for airport operators: keep that snow removal equipment gassed up and ready to go!
—Michael Griesinger is the lead forecaster for the National Weather Service, Twin Cities/Chanhassen, MN.
