(FOX 9) - It has been a mild few weeks in Minnesota. Temperatures have been running well above average giving many of us a sense of hope that this winter may not be marked by brutal cold and feet of snow. Well, that may be about to change.
Something called a sudden stratospheric warming event (SSW) has occurred over the last week or so over the North Pole and this could lead to some cold times ahead for much of the U.S. and parts of Europe.
Roughly 100,000 feet above our head lies the stratosphere, an area of the atmosphere that is above the clouds and most of our day to day weather patterns.
But every so often, a disruption in the typically very cold temperatures just below the ozone layer can effect life on the ground. The cause of this disruption is complex and is still up for a bit of debate among scientists, but the result is a significant warming of temperatures in the stratosphere. It is this warming that allows the polar vortex to break down, sending cold and dense arctic air spilling out of the North Pole region and heading into the mid-latitudes.
Just a reminder, the polar vortex does not move like the pop culture use of the term suggests it does.It is always in the pole region, but varies in strength throughout the year. When it is weakened in the winter by a SSW, this broad area of low pressure breaks down and wobbles like a spinning top, allowing little pieces to break off and head southward. It is these pieces that can bring extremely cold air to parts of the U.S. and the rest of the Northern Hemisphere depending on their exact trajectory.
In general, many parts of the Northern Hemisphere experience colder than normal temperatures in the 30 to 60 days following a SSW, but not everyone gets the same effects. It is these “polar vortex pieces” for lack of better term, that ultimately determine who ends up much colder than normal.
It is these same pieces that can bury areas in snow and produce well below average temperatures for significant periods of time for the regions that are unlucky enough to get them. If you recall the “polar vortex winter” of 2013-14, that was a year where one of these pieces got stuck in central North America giving us one of the coldest winters in the last 50 years.
Now, I am absolutely not saying that is going to happen again, but just gives you an idea of the type of weather these warming events can bring. On the other side of the coin, the arctic cold and snow can miss us all together and impact other parts of North America leaving us dry and seasonable, but that option has a much smaller probability.
Time will tell exactly how cold it gets in Minnesota this time around, but I would not count out winter just yet as we have a long ways to go, especially considering it can snow all the way into May and it is only January.