PHOENIX (AZFamily) — It’s a First Alert Weather Day as a strong storm system makes its way through Arizona. Expect rain, snow, thunderstorm potential and cooler temperatures to end the work week.

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.

Northern Arizona experienced high levels of snowfall over the weekend causing multiple road way closures and detoured traffic.