Following a surge of cool air into the southwestern United States, temperatures will rebound later this week. However, a major push of cool air may plunge along the Pacific coast and Intermountain West next week.
The cool push, which arrived in the Northwest on Monday, shaved temperatures by an average of 4-8 degrees Fahrenheit.
Snowflakes fell over the high country of the Tetons in northwestern Wyoming early Tuesday. Snow blanketed the ground at Bald Mountain Pass, Utah.
This transition will continue over much of the Southwest into midweek with highs in the middle 90s to low 100s being replaced by highs in the lower to middle 90s across the interior.
The change of air has been producing locally gusty winds which will continue across Southern California and the Southwest into Tuesday night, then focus toward the southern Rockies on Wednesday.
The shifting weather pattern has also produced spotty thunderstorms.
The gusty winds, dry air and storms are creating conditions favorable for the ignition of and quick spread of existing wildfires over the region.
There are dozens of active wildfires in the western U.S. from California to Washington, Montana, Wyoming, Colorado and New Mexico, according to the Incident Information System.
The Walker Fire, burning in the Plumas National Forest in Northern California has consumed more than 44,000 acres and was only 10% contained as of Tuesday morning.
Temperatures are forecast to climb back to and above seasonable levels later this week and into this weekend.
Highs during the middle of September typically range from the lower 70s in Seattle to the lower 100s in Phoenix .
This week's push of cool air may pale in comparison to next week's burst of chilly, autumnlike weather.
While a southward dip in the jet stream set into motion this week's push of cooler air, a major southward plunge in the jet stream is forecast for next week.
When the jet stream dips to the south, it allows not only cool air to drain southward from northern latitudes, but cool air can also be manufactured right over a region within the jet stream trough.
During the early autumn, the cooling can be greatly enhanced over the mountains to the point where snow showers can occur, especially in the western U.S.
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"We expect some snow to fall next week over the high country of the Cascades and perhaps the northern Sierra Nevada and northern Rockies," according to AccuWeather Senior Meteorologist Brett Anderson.
Snow fell atop Big Sky Ski Resort in Montana on Sept. 10, 2019. (Photo/Big Sky Ski Resort)
It is too early to say for sure how low snow levels may dip and how much snow may fall. The odds are against travel disruptions due to snow over the passes this early in the season. However, it is possible that several inches of snow falls on non-paved areas at and above some of the passes.
"The pattern is likely to produce a proliferation of rain showers over the lower elevations that may extend fairly far south," Anderson said. "However, it is not a pattern that favors widespread soaking rainfall."
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Since next week's chilly burst is likely to be more pronounced than this week's cool shot, locally strong winds may occur with perhaps potent thunderstorms along the leading edge of the cooldown.
As the chilly pattern evolves, there may be thundershowers with hail, a brief tornado or even a waterspout along the coast.
As a result, a new round of flare-ups of wildfires and blowing dust are likely. Crosswinds may be strong enough in open areas and through some of the passes to cause trouble for trucks, buses and motor homes.
Details on the extent of the chill and related weather conditions in the West will unfold over the next several days.
It appears that the core of the cool air will be centered along the Pacific coast and over portions of the Great Basin and Intermountain West, rather than along the central and southern Rockies.
The upcoming pattern next week may deliver some of the first frosts and freezes of the season in the normally cold spots.
Download the free AccuWeather app to keep track of temperature trends in your area. Keep checking back for updates on AccuWeather.com and stay tuned to the AccuWeather Network on DirecTV , Frontier and Verizon Fios.
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