Temperatures to Plunge Up to 50 Degrees as Snow Hits the West

You may experience weather whiplash in the coming days if you live in the western U.S. After days of warm and dry weather, a major pattern shift will bring in cold temperatures and the threat of snow for the higher elevations. Here are the details on the timing and projected impacts of the looming storm system out West.

Dramatic Change in the Weather Headed to the West

A deep dip in the jet stream over the western U.S. will support the development of an early-season snow event for the top terrains of the Rocky Mountains. Areas that do not see snow will still experience noticeably colder temperatures and the chance of rain. Temperatures will fall by as much as 25 to 50 degrees throughout much of the West, bringing an end to the early-fall heat wave that has marked the last several days in this part of the country.

The change in the weather will become noticeable for most people by the weekend. Conditions more typical of the end of the fall season will move into a zone from Washington down into California and to the east into Montana.

For instance, after seeing highs hit the 80s on Tuesday, Great Falls, Montana, will struggle to climb out of the 30s on Sunday and Monday. To say that this 50-degree swing is notable is an understatement.

The surge of cool air will extend as far east as Rapid City, South Dakota. Temperatures in the low 90s on Friday will be replaced by readings that top out in the 50s on Sunday in this part of the northern Plains.

While the change will not be quite as dramatic in California and the Southwest, the shift will still be a marked difference from the sizzling weather as of late. Los Angeles has been dealing with highs near the century mark over the last week; however, top afternoon readings will max out in the 70s by Sunday, marking a return to historical averages for Southern California.

Precipitation Will Accompany the Cooler Temperatures

The dip in the jet stream will do more than just bring down colder air from Canada. This movement will clash with a surge of tropical moisture coming up from the Eastern Pacific to generate widespread precipitation over the western third of the nation by early next week.

What is left of Hurricane Rachel will filter up into the Southwest, turning on the moisture machine up into the Four Corners region and beyond. Rain is also in the forecast for parts of the Pacific Northwest and the Intermountain West.

Snow will be the story for the higher elevations of the region. Snow levels will fall early in the week, resulting in the chance of flakes flying across parts of Washington, Oregon, Idaho, California, and Montana by the end of the weekend. This snow line is forecast to creep east into Utah, Colorado, Wyoming, and the Dakotas to start the new work week.

There have been a few isolated snow events in the highest peaks of the Cascades and the northern Rockies over the last few weeks. However, this event will mark the first major snow event for the mountains of the West. For instance, snow is expected to disrupt outdoor plans for visitors at Montana's Glacier National Park this weekend. The flakes will also fly at the high and intermediate elevations in and around Yellowstone National Park. The cold temperatures will allow the snow to accumulate and hang around for some time.

The latest forecast models are calling for snow totals of 6 to 12 inches at elevations as low as 4,000 feet across the northern tier of the Rockies between Saturday and Monday. A few isolated pockets could pick up up to two feet of snow out of this weather maker.

Motorists heading out over the passes in the Washington Cascades late Friday into early Saturday will want to be mindful of the chance of snow. Warmer ground temperatures will mean that the snow is not likely to stick.  It will be a similar situation over California's Donner Pass beginning late Sunday with wet snow that does not accumulate on the surface of the road.

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