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WEB EXTRA: What is a polar vortex?
By: WJAC Web Staff
JOHNSTOWN, Pa. -- As the viewing area braces for some of the coldest air that residents have experienced in nearly 20 years, there has been a lot of talk about what is causing the unusually cold air.
6 News Chief Meteorologist Jim Burton said the cause of the bitterly cold air is the polar vortex, an upper level low. The air mass is usually north of the Hudson Bay in Canada, but on some occasions the cold air moves further south.
In this case, the air mass has encompassed a large portion of the United States, including the Great Lakes region, Mid Atlantic and New England.
The polar air will drop temperatures to near or below zero and cause wind chills to plummet 20 to 40 degrees below zero.