FORECAST SUMMARY: Friday May 29th, 2026, through Monday June 1st, 2026
Ozone:
Ozone concentrations are expected to be in the Good (Green AQI) to Moderate (Yellow AQI) range.
PM-2.5:
PM-2.5 concentrations are expected to be in the Good (Green AQI) to low-Moderate (Yellow AQI) range.
FORECAST DISCUSSION:
Meteorological summer is on the horizon as June 1st kicks off the next work week. With the change in seasons approaching, Mother Nature has flipped a switch over the Great Lakes, going from wet and cooler conditions to warm and clear skies in a matter of weeks. An omega block pattern has set up in the Midwest which has High-pressure influencing our weather for the better part of a week or longer. Sunshine and even more sunshine is expected over the coming days to potentially a week and a half due to this atmospheric set up. Going more in depth, an omega block is when a High-pressure system sets up with two Low-pressure systems on either side of the High. This forces the jet stream to form a shape that looks like the Greek letter ‘omega’, hence the name omega block. This then forces weather systems around the High-pressure, providing clear conditions for those under the High. Once a system like this forms, it typically hangs around for multiple days or even weeks. This is the reason for clear skies, light winds and temperatures in the 70s across Michigan this upcoming weekend and into next week.
For air quality, with the current weather regime in place, wind direction will predominantly be northwesterly to northeasterly this weekend which will provide cleaner air. However, since we will be in the same airmass for numerous days, pollutant buildup may occur so our eyes will be watching both PM2.5 and Ozone concentrations this weekend and into next week. As of now, PM2.5 and Ozone concentrations are expected to remain in the Good to Moderate range, but if any conditions warrant an update to this forecast, an update will be made.
EXTENDED FORECAST:
Clear skies and warm temperatures remain throughout the next week. Air quality will be in the Good to Moderate range to start, but with temperatures increasing mid-to-late next week, Ozone may become an issue.
Analysis of Ozone development on May 27th:
In total, six Ozone monitors exceeded the Unhealthy for Sensitive Groups (USG) range for an 8-hour average on Wednesday May 27th. Four of those monitors were in west Michigan (Cassopolis, Coloma, Kalamazoo and Jenison) with the remaining two in southeast Michigan (Ypsilanti and Tecumseh). Models and forecast guidance on Tuesday looking at Wednesday suggested a few hours exceeding the USG range, but overall 8-hour averages were expected to remain in the Moderate range. Also, northwest to northeast winds were expected to set up in the mid-afternoon which would inhibit additional Ozone production. However, looking at the atmospheric set up on Wednesday the 27th, for inland west Michigan, a budding theory could be that persistently light to minimal winds near the surface allowed for Ozone to develop under clear skies and an already dirty airmass from the day before with necessary precursors in place. Whereas the lakeshore monitors of Holland and Muskegon, both of which were Moderate, were impacted by a building northwest wind coming off the lake which helped to keep the air cleaner, therefore less Ozone development. For southeast Michigan, winds were already shifting to the east-northeast by early afternoon, so areas to the southwest of Detroit were impacted by Ozone more than metro Detroit monitors due to precursor drift along with high-level clouds over metro Detroit. This has been seen before but on rare occasions. With numerous variables that go into the Ozone photochemical reaction, there seems to often be additional factors at play to keep us forecasters on our toes.
Next Forecast update: Monday June 1st, 2026