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The smoke forecast for Colorado and the U.S. (NOAA)

Heavy smoke from wildfires in California and Oregon is expected to blow from northwestern Colorado across much of the state Friday afternoon and Saturday, causing hazy conditions and one of the heaviest fine particulate matter concentrations of the year, according to an advisory from the state’s health department and the National Weather Service. 

Residents sensitive to poor air quality, including those with heart disease and respiratory illnesses, are being warned to stay indoors if smoke becomes thick in their neighborhood and to avoid heavy or prolonged exertion through at least Saturday afternoon, the state’s advisory said.

Other residents are advised to reduce “heavy or prolonged exertion” as the amount of particulates in the air increases sharply.  

Sheltered valley locations, like the trough that I-25 runs through in the Denver metro area, should expect the heaviest impact from the smoke, the state’s advisory said.

The smoke forecast for Colorado and the U.S. (NOAA)

The warning comes as the state has had weeks of bad air quality, in part because of enormous fires raging along the West Coast and a wind pattern that has steered fire smoke into Colorado, said Paul Schlatter, a meteorologist with the National Weather Service in Boulder. 

Because the state has been under a “persistent ridge of high pressure” that sends smoke from the western states into Colorado, there’s little wind closer to the ground that could blow the smoke away to the central Plains of the United States, Schlatter said.

“Without strong winds near the surface, the smoke just kind of sticks around,” he said.

The high pressure ridge could break down, and conditions could improve for a few days next week, he said.  But particulate matter will be at all levels of the atmosphere Friday and Saturday, creating vivid red and orange sunsets and heavy haze. 

“We’re expecting very poor air quality throughout the day Saturday,” he said. 

Russell Danielson, another meteorologist with the weather service in Boulder, said Saturday should be one of the worst days of the year in terms of the level of fine particulate matter in the air in Colorado. He said ash may fall from the sky, but that that’s not likely to be widespread given how far away the fire is. 

The smoky conditions also come as a heat wave has repeatedly spiked Colorado’s ground-level ozone levels to “Unhealthy” along the Front Range this summer. The Front Range has had 46 Ozone Action Alert days this year, more than the 43 issued in all of 2020.

Ozone and particulates can irritate and inflame the airways, causing swelling, coughing and scratchy throats. Ozone is mainly attributed to car exhaust, oil and gas drilling and intense sunlight and heat.

As of Friday afternoon, Denver ranked 34th in worst air quality among major cities in the world, according to a dynamic list from IQAir, an air technology company. 

Shannon Najmabadi covered rural affairs and the rural economy for The Colorado Sun from 2021-2023.