weather below average forecast temperature 20210818
CNN  — 

With little over 30 days left in a summer marked by record-setting heatwaves and historic wildfires, a dramatic change is coming for parts of the West on Wednesday and into the weekend.

A potent autumn-like storm is slowly moving across the Rockies, setting the stage for a sharp drop in temperatures and even the season’s first snowfall. But it is also elevating wildfire conditions and bringing wildfire smoke and poor air quality to major cities in California.

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Temperatures take a nosedive

On Monday and Tuesday, temperatures soared past the century mark in cities like Billings, Montana, and Rapid City, South Dakota, fueling dozens of wildfires in the region. But relief is on the horizon.

A potent frontal boundary is marching across the region, introducing the chance for significant rainfall, much cooler temperatures and respite from smokey skies in states like Montana, Wyoming, and Utah. The cold front is forecast to slice through temperatures in the region and, at least briefly, put an end to the oppressive heat.

“Given the strong cold front, much below normal temperatures, especially in terms of highs, are expected, particularly today in Montana, where highs could be as much as 30 degrees below average,” the Weather Prediction Center wrote Wednesday morning.

The temperature in Casper, Wyoming, was just shy of 100 degrees on Tuesday, but highs will fail to reach 70 degrees by Thursday. After similar heat in Miles City, North Dakota, the system is forecast to usher in an impressive 30-degree departure by Wednesday with temperatures falling into the 70’s.

The slow-moving system will bring periods of thunderstorms and potentially heavy rainfall to parts of Wyoming, Colorado, and Utah through Thursday. The National Weather Service in Salt Lake City has issued flood watches for much of the state of Utah through Wednesday as the risk for flooding remains elevated in many of its burn scars and dry washes.

Cold air will couple with moisture in the high Rockies to support some of the season’s first snowflakes. Hikers planning to head to higher elevations of the Northern Rockies and the Wasatch Mountains could be greeted by snow above above 10,000 feet.

However, the passage of the cold front is no cakewalk for some.

Fanning the flames

On Tuesday, the cold front swung through Northern California, which increased fire activity around the Dixie Fire, the second-largest fire in state history.

This front also brought gusty winds that prompted the Caldor fire to explode to three times its size Monday night into Tuesday.

Temperatures may drop to around normal in Northern California, but the wind will persist and humidity will remain low, creating critical fire weather conditions.

“As a result of the elevated to critical fire weather conditions, almost every ongoing large fire was active, with many of the fires exhibiting rapid and significant growth,” the National Interagency Fire Center wrote.

“(The) next two days will produce extreme burning conditions … I have never seen anything like what is presenting,” former Cal Fire Chief John Hawkins tweeted Tuesday.

Despite the cool down, poor air quality from wildfire smoke will remain a problem. Nearly 10 million people in parts of eight states continue battling smoke-filled skies from the ongoing flames.

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As the front passes through California, winds are forecast to push smoke into major population centers, including Sacramento, San Francisco and Oakland.

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Computer models predict widespread smoke aloft will spread across the region and will mix down into the lower elevations at times, especially over the Bay Area beginning Wednesday, according to the National Weather Service.