An early winter preview is forecast for the Upper Midwest , the Ohio Valley and the Northeast next week, as a strong dip in the polar jet stream is expected to plunge temperatures anywhere from 10-20 degrees below average for more than 200 million Americans.

The colder conditions will also create the potential for light to moderate snow across that region beginning Sunday, the first of the season for many.

WHAT IS THE JET STREAM?

A strong area of low pressure will usher in the coldest air of the season from Canada into parts of the Lower 48 beginning Sunday.

Major cities around the Great Lakes could see temperatures plunge more than 20 degrees between Friday and Monday.

Cleveland has a forecast high temperature of 60 degrees on Friday and will struggle to reach 40 degrees come Monday.

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