Cold storm to bring rain, snow and thunder to western U.S. this weekend

As a storm tracks across the interior West this weekend with rain and thunder, it will generate enough cold air for snow to fall over some of the higher elevations from the Cascades to the Wasatch and northern and central Rockies, AccuWeather meteorologists say.

Showers already dampened areas from coastal Washington and Oregon to the northern parts of Nevada and Utah, as well as portions of Idaho on Friday. The showers will spread farther to the east and south over the course of the weekend, reaching much of Montana, Wyoming and western Colorado by Sunday.

During the afternoon and evening, thunderstorms will erupt in some areas and can produce hail and sudden lightning strikes. Campers and hikers should be aware of quickly changing weather conditions. Hikers should avoid open areas over the ridges to reduce the risk of being struck by lightning.

Hikers could face a different problem as the weekend progresses. The chilly air associated with the storm will allow freezing levels to dip, and snow will begin to reach down from the ridges and peaks to some intermediate elevations from the Cascades to the northern and central Rockies.

In some cases, the snow showers can be accompanied by thunder and lightning.

Wet snow can become mixed in over the passes in the Cascades by Saturday night. During Sunday and Sunday night, some of the passes in western Montana, Wyoming and Colorado can also become a bit wintry with snow and slush.

"With the weekend storm, snow levels in the various ranges of the northern Rockies will drop to 5,500 feet," AccuWeather Senior Meteorologist Chad Merrill said. "Accumulations of 1-3 inches are expected near and just above pass levels, leading to slushy roads over some of the passes."

Over the high country of the Wasatch Range, Tetons, Bighorns, Bitterroots, Clearwater and Colorado Rockies are likely to pick up a foot of snow or more from the storm.

Temperatures can dip to even lower levels than during the latter part of this week and may be no higher than the upper 20s and lower 30s over the high country on Sunday.

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Limited moisture will prevent much in the way of rain or mountain snow in California this weekend.

There can be a little snow over the ridges and peaks in the northern Sierra Nevada on Saturday, but no significant travel problems are expected over Donner Pass due to a limited amount of moisture available that far to the south and west, Merrill said.

"Winds will kick up for the Sacramento and San Joaquin valleys, particularly as the system departs on Sunday," Merrill stated. "Combined with the low humidity and rebounding temperatures in the area, the risk for wildfires will jump. The windy conditions, dry air and fire risk will shift to New Mexico and West Texas by Monday."

The same chilly western storm will behave differently as it swings east of the Rockies by early next week. The storm is likely to start a significant outbreak of severe weather, including tornadoes, over the Plains and Mississippi Valley.

In the storm's wake, some of the highest temperatures of the season may follow in parts of the West before Memorial Day weekend starts.