Smoke rolled into the Missoula area last night. In Frenchtown, air quality deteriorated starting at 5pm, briefly reaching UNHEALTHY levels before returning to MODERATE levels by 9pm. Missoula did not fare as well. Smoke moved in around 8pm, reaching UNHEALTHY levels quickly and getting trapped under the inversion. Air quality remains UNHEALTHY in Missoula this morning. Elsewhere, air quality is generally MODERATE in western Montana with some areas of GOOD air quality in southwest and eastern Montana.
The cause of the increased smoke in Missoula compared to the rest of western Montana is a prescribed fire across the border in Idaho. This fire has been burning since Thursday, and increased mixing in the atmosphere allowed the smoke to crash down into the Missoula area Friday night. More information about this burn can be found here. The haze that is impacting the rest of the state is due to smoke moving in from Oregon and California following southwesterly winds.
A cold front is expected to move through the state later today. The increased winds should help clear out smoke from most communities in western Montana. As the cold front sweeps through, areas of eastern Montana may see smoke levels increase this afternoon as smoke is pushed through the state. Conditions should improve from west to east throughout the afternoon, with most of western Montana seeing GOOD air quality by Sunday morning. In eastern Montana, air quality will likely be MODERATE this afternoon, improving to GOOD throughout the day on Sunday.
What about Missoula and areas near active fires in northwest Montana? The Missoula area should see some improvement this afternoon as the smoke lifts off the valley floor, although that smoke may drain into the Bitterroot Valley along northwest winds for a brief time before improving. I would expect Missoula to see periods of MODERATE air quality by later today. In Missoula and areas of Northwest Montana near active fires (Libby, Columbia Falls, etc.), smoke may settle into the valleys overnight for the next few days, causing elevated impacts through the morning hours.
The possibility of a cooler, and potentially wetter, week means widespread air quality impacts are unlikely, although localized impacts near active fires are expected to persist.
Air quality deteriorated in the Missoula area last night, reaching UNHEALTHY levels between 5 and 10pm. Conditions improved in Frenchtown, where air quality is currently MODERATE, but has remained UNHEALTHY in Missoula throughout the morning. Elsewhere, smoke from increased fire activity in Oregon, California, and Idaho has created MODERATE air quality in many locations. A cold front will move through today, which should improve air quality from west to east over the next 24 hours. Unfortunately, areas near active fires will likely see overnight and morning impacts persist for the next few days.