FORECAST SUMMARY: Wednesday, August 23, 2023, through Friday, August 25, 2023

PM-2.5: 24-hour average Fine Particulate levels will range between Good and low Moderate.

OZONE: 8-hour average Ozone concentrations are expected to be Good to Moderate across much of the state, with USG possible in the southwest Wednesday and Thursday.

FORECAST DISCUSSION: As forecast, a complex of storms tracked from the Upper Peninsula southeast into central and southeastern areas Wednesday morning. As Wednesday progresses, a warm front pushes in from the west before stalling for a time across the central part of the state. Strong southerly winds develop south of this boundary bringing in very warm surface and upper-level temperatures and high dew points. This will cause hot, humid conditions to develop Wednesday afternoon into Thursday, especially across the southern portions of the state. The frontal boundary will also be the focus of storm development over the next two days. Temperature and humidity levels improve Friday as the boundary sinks south and northerly winds bring in cooler temperatures and lower dew points.

The threat for increased ozone remains Wednesday and continues into Thursday across the southwestern portions of Michigan. Because of this, we are continuing the current Air Quality Action Day through Thursday and forecasting ozone concentrations in the Unhealthy for Sensitive Groups (Orange AQI) range for the counties listed above. Along and north of the forementioned boundary, cloud cover and higher chances for storm development are expected. These conditions should keep ozone from reaching higher than Moderate, and possibly Good further north. Ozone concentrations improve with the airmass change and northerly winds Friday. Readings Friday should range between middle Good and low Moderate.

Wildfire smoke maps were reviewed and we do not expect wildfire smoke to have an influence on pollution levels the rest of the week. With southerly winds and increased moisture along and south of the boundary, PM2.5 is likely to increase, but readings higher than Moderate are not expected. Any increase in PM2.5 should improve to Good on Friday.

EXTENDED FORECAST: Extended models show another cold front passing late Friday/early Saturday bringing precipitation back into the forecast. Regardless on the exact timing of this boundary, cooler temperatures are expected during the upcoming weekend which should help keep pollution levels low. This forecast will be updated Friday to better detail the coming weekend into early next week.

Next Forecast update: Friday, August 25, 2023