FORECAST SUMMARY: Tuesday, February 17, 2026 through Friday, February 20, 2026
PM-2.5: 24-hour average Fine Particulate concentrations are expected to be mostly Low Moderate (AQI Yellow) throughout the forecast period.
FORECAST DISCUSSION
Most people are aware of the elevated fine particulate episode we endured in SE Michigan over the weekend. The news media attached themselves to the narrative that melting snow was directly emitting particulates into the atmosphere. Unfortunately, this is a misrepresentation of the role that melting snow plays in the formation of fine particulates. Does melting snow directly emit particulates to the atmosphere as it melts? Absolutely not… Can melting snow play a role in the formation of fine particulates. Yes, assuming other elements are in play.
Those other elements include a solid snowpack which keeps the air near the ground cold. Next you have warm air overriding the cold surface, as we did with temperatures nearing 60 degrees. With warm air overriding cold air, the atmosphere is very stable with air tending to sink towards the ground. Add to that a persistent high-pressure dome which created a strong inversion layer, especially during the nighttime hours. That inversion layer can be near the surface effectively trapping the increasing dirty air already hugging the ground. A review of the upper air sounding, Sunday morning, showed that capping inversion layer began only 30 meters above the ground. Consider, too, all the particulates from road salt dust kicked up by urban scale traffic along with all the primary and secondary fine particulates from vehicle emissions. home/industrial heating, and industrial processes being continually pumped into that shallow layer of air trapped near the ground. Compounding the issue is increased moisture from the snow melt which can act as a catalyst for forming secondary particles and also act as a nuclei for other particulates.
With all those pollutants being crammed into this tight 30-meter layer, it was not surprising to see increasing particulate readings. The AQD forecaster observed all the elements coming together and appropriately issued an advisory. The forecasters decided to extend the advisory through noon, Monday, when winds were expected to increase allowing for cleaner air to mix down. This forecast was accurate as we did experience several SE Michigan monitors cross into the USG range.
Following this event on social media, I observed several comments to the effect that people had never seen this phenomena before. Actually, it is quite common for this to occur during this time of year, albeit to different degrees. This was more a of “perfect storm” where all the contributing elements were at an extreme causing higher concentrations.
The rest of the work week should feature AQI’s in the Moderate range. While we do not see a complete cleanout during the week, most of the elements described above are no longer in play.
EXTENDED FORECAST:
Air Quality is expected to a mix of Good to Moderate entering the upcoming weekend.