(NEW YORK) — A significant change in the atmosphere means the weeks after Thanksgiving could be colder and snowier than normal across portions of the United States.

It’s all thanks to a disruption in the polar vortex. Here’s what you need to know.

Why is this happening?

Our atmosphere consists of many layers of moving air; the troposphere is where our weather happens and above it is the stratosphere. Over both poles, a ring of strong mid-level winds called the polar vortex traps cold, sub-arctic air.

There are two of these polar vortexes — one in the troposphere that affects weather every winter, and one in the stratosphere that contains much colder air but only affects the surface weather during winter less frequently.

When polar vortex winds are strong, this frigid air remains near

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