Polar vortex 2021: Winter makes a comeback, plus what we can expect in Rochester

Weather Blog

ROCHESTER, N.Y. (WROC) — The buzzword made famous from an arctic blast in 2015 is making a comeback.

The polar vortex, a rotating bubble of cold air around the north pole, is about to break off and head into much of the United States for the second half of January.

The polar vortex gets its name from a counter-clockwise spin around the north pole. The constant air mass is protected by the polar jet stream. It weakens in the summer and strengthens in the winter.

Occasionally, the air mass splits and sends cold air southward into the middle latitudes. This happened to excess in 2015 when Rochester clocked in its coldest February on record at 12.2°.

This polar vortex caught on as a buzzword and became one of the most recognizable “new” terms in meteorology, even though the polar vortex itself has been known about and studied within the weather community for decades.

When the polar vortex is strong, it remains solidly in place over the poles. When it starts to weaken as warmer air “injects” into the poles, the stronghold can erode away and cooler air can be forced southward, where more people live and will be impacted by an arctic blast. While the polar vortex is always around, we only feel its cold a few times a year, if at all.

WHERE THE POLAR VORTEX IS HEADED

Note the United States at the bottom of this image. See where the blue colors are over Alaska and the Midwest U.S., and the purple colors over Russia and northern Canada. Those are pieces of the polar vortex. Image as of Friday, January 15th.

Long range models are forecasting for a chunk of the polar vortex to break off and invade the central United States across the Dakotas, eastern Great Lakes, central United States, and a bit into the Northeast. Long range models are forecasting for a chunk of the polar vortex to break off and invade the central United States across the Dakotas, eastern Great Lakes, central United States and a section of the Northeast. While this specific intrusion of polar air is not the most overwhelming we’ve seen, it does look like we’ll see a decent return to colder air by month’s end.

This shot of cold will not be nearly as potent as arctic blast in the past, but it may bring Rochester the coldest stretch so far this winter.

This is relative to 2020-2021 as temperatures have been above average for both December and January. The shot of cold air locally will open the door for lake-effect snow showers if winds set up and any larger storm systems that pass by could bring snow as well.

Expect the temperatures to drop over Dr. Martin Luther King Jr. weekend thanks in part to a sliver of the polar vortex. Rochester will not see any significant or prolonged cold air. The bulk of the cold will remain well west of the region.

Find the News 8 weather team’s daily updated forecast here for more details on what to expect.

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