PASADENA, Calif. (AP) — Several overturned semis on a Utah highway. Hundreds of thousands without power in California. A wind gust reaching 123-mph in Colorado.

The powerful winds that tore across Western states Thursday created a path destruction that closed schools, left neighborhoods with a snarl of downed trees and power lines, and prompted some communities to declare emergencies.

The storms, described as a once-in-a-decade event, were the result of a dramatic difference in pressure between a strong, high-pressure system and a cold, low-pressure system, meteorologists said. This funnels strong winds down mountain canyons and slopes.

The system brought high wind warnings and advisories for California, Utah, Nevada, Wyoming, Arizona and New Mexico. The blustery weather is expected to eventually hit Oklahoma, Missouri and Indiana.

The violent winds eased but strong gusts still blew through the region Thursday night, at times reaching 60 mph in some California mountains. Forecasters said the winds would continue to diminish through Friday.

The winds were fanning fires in northern California.

The Sacramento Bee reported that as of Thursday evening, seven fires had burned more than 130 acres in El Dorado County. Five fires had also burned more than 250 acres in Tuolumne and Calaveras counties.