Heavy snow, dangerous travel to expand as cold storms sweep from Cascades to interior West

Cold storms moving inland this week will bring heavy mountain snow from the Cascades to the Rockies, creating dangerous travel over mountain passes and potential delays in cities such as Salt Lake City and Denver as the system pushes southeast.

These storms will sweep from Washington and Oregon into Arizona, New Mexico and Colorado and bring rounds of snow to the mountains and interior West, along with cold rain at lower elevations near the Pacific coast.

A wintry week for the Northwest

Several feet of snow will pile up over the Cascades through Thursday night, with 6 to 10 feet possible in the highest elevations. As fresh snow piles up, the risk of avalanches will increase on steep mountain slopes.

Heavy snow, dangerous travel to expand as cold storms sweep from Cascades to interior West

Up to a few feet of snow will accumulate at pass levels in the Cascades. Snowfall rates may approach or exceed 2 inches per hour at times. As snow levels drop in the Cascades, snow will broaden into lower elevations. This combination of heavy snowfall and high rates could make it difficult for road crews to keep up, closing some mountain passes.

Heavy snow will also pile up over the Olympics, with moderate to heavy snow spreading across the Blue Mountains of northeastern Oregon and parts of Idaho, western Montana and northwestern Wyoming.

Cold rain will fall along the Interstate 5 corridor in Washington and much of Oregon, leading to slick roads and ponding in areas with poor drainage. However, snow levels may dip as low as 1,000 to 1,500 feet with some accumulation possible over the hills. Slippery conditions are likely over Siskiyou Summit in southern Oregon.

Winter arrives over the interior West

As the storms move southeast, snow will spread farther south as snow levels drop across Nevada, Utah, Colorado, Arizona and New Mexico. While the snow will help ease drought concerns in the Colorado River Basin, it is likely to cause travel problems in areas that have seen little winter weather so far.

From Thursday into Friday, rain may remain just east of Las Vegas, while Phoenix is likely to receive a soaking that leads to slick travel. Rain will become mixed with and may end as snow in Albuquerque, New Mexico, especially over the heights.

Up to a few inches of snow are expected to fall around Salt Lake City from Wednesday night to Thursday, with similar accumulations forecast for Flagstaff, Arizona, Thursday.

Denver will receive accumulating snow from Thursday afternoon into Friday morning, with up to a few inches in the metro area and a foot or more possible in the nearby mountains. While crews should be able to keep up with the storm, roads and runways will be slippery for a time, and airline delays are likely due to deicing operations.

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Freeze-ups, Santa Ana follows western US storms

After the storm moves out late this week into the weekend, high pressure will build from the Pacific into the Great Basin, leading to two weather concerns.

Temperatures will plummet over the interior West, where there is fresh snow on the ground and winds are light. Untreated surfaces that become wet from daytime melting will refreeze into sheets of dangerous ice.

As air pressure rises over the Great Basin and interior California, winds will strengthen as they move over mountain passes, funnel through canyons and surge toward the Southern California coast.

While recent rain will keep wildfire risk low and winds will be far weaker than last year's firestorms, soggy ground and top-heavy trees could still be toppled by moderate Santa Ana winds, leading to blocked roads, minor damage and isolated power outages.

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