The Beaufort Gyre is a wind-driven circular current in the western half of the Arctic Ocean, that alternates between a clockwise and counter-clockwise motion: when it circulates clockwise, it traps ice and melted freshwater, and when it spins counter-clockwise, it releases that freshwater and ice into the North Atlantic Ocean, southward past the east coast of Greenland. This trap-and-release cycle typically reverses every five to seven years, usually when a cyclonic storm in the North Atlantic moves into the Arctic, reversing the Gyre’s direction.

Following nearly two weeks of record-breaking freezing temperatures, a severe winter storm is forming off of the east coast, one that resembles a winter hurricane in many respects, and will run north from Florida through to Atlantic Canada. Aside from being a cyclone that is expected to deliver wind gusts of up to 60-70 mph, the storm is also forecast to develop hurricane-level low barometric pressures, the key ingredient for a strong storm.

An mass of cold Arctic air has descended from the north over the continent, causing temperatures to plunge across Canada and the eastern half of the United States. Many regions between Nunavut and Ontario are seeing temperatures well below zero — Fahrenheit, that is (-32ºC), cold enough to crack windows in Alberta and Saskatchewan. Although low-temperature records in many regions aren’t being broken, these conditions are encroaching on century-old records for the duration of regional cold snaps.

A major cold snap is forecast to push south into the contiguous United States over the Christmas holidays, with regions between North Dakota and Colorado experiencing temperatures 20ºF to 40ºF below normal over Christmas Eve. Conversely, the east coast may see above-seasonal temperatures, with a forecast high of 71ºF in Washington D.C, and 62ºF in New York City on Christmas Day.

"If you’re West of the Mississippi River on Christmas Day, then you may want to ask for coal in your stocking," tweets meteorologist Ryan Maue, with "Extreme cold arriving via Polar Express. Off the charts Arctic cold."