A flip in the weather pattern that pumps heat into the eastern United States will send cooler conditions with spotty rain, high-elevation snow and gusty winds into the West this weekend.

"We expect a major shift in the jet stream to develop," according to AccuWeather Lead Long-Range Meteorologist Paul Pastelok.

"The jet stream is forecast to dip southward in the western United States, which will allow cooler air to drain from northwestern Canada and the northern Pacific Ocean," Pastelok said.

The most substantial change in the weather will be across the Northwest, although high heat will be on hold in the Southwest.

Autumnlike air to refresh the Northwest

Many people who have been struggling with the heat and smoky conditions much of this summer in the Northwest will catch a break this weekend.

Compared to the 90- and 100-degree Fahrenheit heat from earlier this month, temperatures will be slashed by 30 to 40 degrees in the Northwest. Highs will be in the 60s and 70s in many of the low elevations and the 40s and 50s over the high country.

Accompanying the cooler air will be a round or two of cool showers and even some wet snowflakes over the high country of the northern Rockies and perhaps the Washington Cascades. The rain will be steadiest and the prospect of snow on the mountain peaks highest in the northern Rockies Sunday night into Monday.

A positive aspect of the locally gusty winds expected to accompany the cooler air will be smoke dispersal and improved air quality for some upwind communities.

Light winds and heat have trapped smoke from hundreds of large wildfires in the lower layers of the atmosphere for weeks across western Canada and the U.S.

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Lower temperatures and spotty rain showers will assist with firefighting efforts in the Northwest. Both will inhibit fire growth.

However, the gusty winds will be a negative for firefighting efforts as some fires may behave erratically.

"South of where rain is expected to fall from the Sierra Nevada of California to western Wyoming, gusty winds will ramp up the fire danger on Sunday," AccuWeather Senior Meteorologist Kristina Pydynowski said.

Some cooler, less humid air to reach California, Southwest

In Southern California and the interior Southwest, the change in the air will allow lower humidity levels and slightly lower temperatures to arrive.

High and low temperatures by early next week are likely to be trimmed 5 to 10 degrees when compared to early this past week.

Much of Southern California has been experiencing high humidity levels and warmer-than-average nights this summer.

The slightly drier air should allow temperatures to dip more at night, when compared to most nights this summer.

In Las Vegas, instead of highs in the 100s and lows in the 80s, highs will be within a few degrees of 100 and temperatures may sneak into the upper 70s at night by early next week.

In terms of rainfall, largely dry weather is expected to hold across California and Nevada.

"A push of drier air should ease the thunderstorms across the Four Corners region early next week," Pydynowski said.

Download the free AccuWeather app to see just how much temperatures will dip in your region in the coming days.

Weather pattern to shuffle later next week

As next week progresses, heat is likely to build westward across the Plains to the Rockies and part of the Great Basin.

However, cool and breezy conditions may hold from California to Washington.

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