Winter weather-related warnings were in place for at least 17 states across the U.S. early on Friday, the National Weather Service (NWS) forecasting 13 inches of snow to hit some parts of the country.

Forecasters warned heavy snow could make roads slick and reduce visibility, making travel in some areas "very difficult to impossible."

PARKS, Ariz. (AP) — A winter storm dumped heavy snow across northern Arizona on Friday, playing a major factor in a more than 15-mile backup on a major interstate. Semi-trucks and other vehicles were stalled on Interstate 40 westbound between Flagstaff and Williams late Friday as the sun set. The standstill dragged on for hours.