It's all any weather forecaster is talking about right now. A massive blast of cold air from the Arctic is spilling down into the United States, causing temperatures to plummet sharply as it advances:
In Denver, temperatures dropped from 65°F to 38°F in a mere half hour on Tuesday morning. The Great Plains and Midwest are getting buried in snow. Meanwhile, the cold front is moving East and will eventually affect roughly two-thirds of the continental US.
And the cold could persist for a good chunk of November as another Arctic blast is expected next week. Here's the 6 to 10 day outlook from the National Weather Service. Blue areas have a higher likelihood of colder-than-normal temperatures:
Where did all this cold come from? The National Weather Service in Tucson put out a good short video explaining what happened. It started with Super Typhoon Nuri in the Bering Sea, which created a high pressure region over Alaska and northern Canada (and is bringing some unusually warm weather there). That, in turn, dislodged some of the frigid air there and sent it south:
Meanwhile, some media outlets are deploying the term "polar vortex" when talking about this bout of cold weather. And that's provoked the ire of more than a few meteorologists, who complain that the word is being wildly misused. They'd prefer to just describe this as a blast of cold air from the Arctic and leave it at that.
For those curious, the National Weather Service explains what the polar vortex actually is here: It's a circulation pattern that's almost always present in the upper atmosphere near the North and South poles. And occasionally its boundary will weaken and a piece of the vortex will push south (although, again, it's still in the upper atmosphere). When that happened in the winter of 2013-2014, it influenced the air closer to the surface and the Midwest got a lot of snow and very cold temperatures.
But the polar vortex is not a new phenomenon — and it's not to blame for any and all unusually cold weather in the United States. The NWS notes that you can have a cold snap in the US without part of the polar vortex intruding southward. Conversely, you can have part of the polar vortex intruding southward without record cold.
ABC's meteorologists say it's better to describe the current bout of cold weather like so: "This is not the polar vortex itself. It is air influenced by part of the polar vortex." Over at Capital Weather Gang, Jason Samenow also urges caution in throwing the term about too loosely:
I tend to agree that we need to be careful about labeling every cold air outbreak a 'polar vortex' event. While it's fine to discuss the role of vortex in a deep explainer about a given cold weather outbreak, media organizations should refrain from using the term in headlines, except for the rare event in which the vortex is breaking down in unusual fashion.
The National Weather Service, for its part, reminds everyone of what's important: "From a practical standpoint, it should be of no consequence whether a particular weather pattern is or is not associated with a southward push of the polar vortex." The debate over specifics is fun to read about. But the one thing we do know is that cold is coming.