Some climate scientists have suggested that oceans warmed by climate change cause changes in the behavior of the jet stream, and these disruptions invite the polar vortex to make repeated visits.

https://www.npr.org/sections/thetwo-way/2018/01/12/577688119/scientists-say-a-fluctuating-jet-stream-may-be-causing-extreme-weather-events

is 15 times rarer than it was a century ago, the article says. It's a rarity that bucks the warming trend.

So, it used to be much more common than it is now, for this kind of weather to happen. It sounds like it's more likely we'll see even fewer of these in the future, not more.

and scientists are just discovering how much it is being influenced by warmer waters in the Pacific ocean. Until they gather enough data to plug into a super computer, we really don't know what is going to happen. Hell, the polar vortex may make fewer visits, but they could be more severe and linger longer.

Until it isn’t.

Maybe it will turn out to be an anomaly. But let’s wait until next year, and next, etc before committing to that view.

have been nearly devoid of snowfall (unprecedented).