Rare ‘Air Stagnation Advisory’ Issued For Idaho And Oregon

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On Thursday, the National Weather Service issued an “Air Stagnation Advisory” for portions of southwest and west central Idaho and northeast and southeast Oregon. According to the NWS, the advisory is anticipating “an extended period of stagnant air, with light winds and little vertical mixing.” The unique condition is due to “an inversion near the surface that will continue to trap pollutants” and “may cause issues for people with respiratory problems.”

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While a majority of Americans likely don’t worry about air stagnation, limited air mixing can occur in mountainous valleys in the Pacific Northwest and Intermountain West during high pressure systems and periods of low wind. According to Google Trends data, web searches related to air stagnation are most common in Idaho, Oregon, Washington, and Montana.

Air stagnation can be particularly dangerous in times of drought, as dust and particulate matter get trapped and accumulate in breathable air. According to the U.S. Drought Monitor, 87.8% of the contiguous U.S. is currently abnormally dry, the largest share since the USDM began tracking national drought conditions in 1999. Fall drought can be especially deleterious for air quality in areas with extensive vegetation, as dry, brittle leaves break down into small, breathable particles harmful to human health.

Currently, 100% of the counties under air stagnation advisory are abnormally dry. In some affected counties, PM2.5 – particulate matter smaller than 2.5 micrometers – concentrations are currently 40% above normal levels. The NWS advisory is in effect until Sunday.