National Weather Service (NWS) forecasters are warning motorists to slow down and use caution in four states as snow, strong winds and reduced visibility are expected to create hazardous travel conditions in mountainous areas through Monday evening.

Urgent winter weather advisory were issued for parts of California, Nevada, Washington and Oregon. Areas affected include the Greater Lake Tahoe region of California and Nevada, the West Slope of the Northern Sierra Nevada, and parts of the Cascades in Washington and Oregon, with snow and hazardous conditions expected in these mountain regions.

Authorities are urging drivers to use cautionespecially on major passes where snow accumulation can range from a few inches to more than a foot. The warnings highlight the potential for slick roads, low visibility and travel delays.

For the Greater Lake Tahoe area, a Winter Weather Advisory has been issued for elevations above 6,500 feet from noon to 10:00 PM PST Monday. Snow accumulations of 2 to 6 inches are expected, with wind gusts up to 45 mph. Drivers should anticipate slick road conditions on passes in the area, including Donner, Echo and Carson, with visibility dropping to less than half a mile at times.

In the North Cascades of Washington, including Washington Pass, a Winter Weather Advisory will be in effect from 6:00 PM Sunday until 1:00 PM Tuesday for elevations above 4,000 feet.

Snow accumulations of 4 to 16 inches are expected with gusty winds of up to 35 mph. Travelers on SR 20 and Washington Pass should prepare for difficult travel conditions. Similarly, the Okanogan County area of ​​Washington will see up to 14 inches of snow above 4,000 feet, with the advisory running from 6 p.m. Sunday through 1 p.m. Tuesday.

In southern Oregon, the Siskiyou Mountains and Southern Oregon Cascades are also bracing for heavy snowfall, with totals in areas above 5,000 feet expected to range from 8 to 16 inches. The advisory, which runs from 4 a.m. to 10 a.m. Tuesday, warns of difficult travel conditions, especially during the Monday morning and evening commute.

Meanwhile, almost 40,000 customers were left without power in Colorado early Saturday after a winter storm swept through the state.

Denver County was the hardest hit, with about 25,000 customers affected as of Saturday, according to PowerOutage.us, an online service that tracks outages across the country.

Counties surrounding Denver, such as Adams, Jefferson and Arapahoe, saw 4,485, 4,400 and 3,630 outages, respectively.

Storm warnings were also issued this week for several other states, including Colorado, New Mexico, Oklahoma and Texas. In Colorado’s mountain regions, up to 24 inches of snow was expected, while cities such as Matheson, Agate, Hugo and Limon could receive up to 20 inches of snow.