FORECAST SUMMARY: Friday, September 15, 2023, through Monday, September 18, 2023

Ozone: 8-hour average Ozone concentrations will remain generally Good with only a few Moderates possible.

PM-2.5: 24-hour average Fine Particulate levels are expected to range between Good to Moderate.

FORECAST DISCUSSION: This forecast period features a frontal boundary moving northwest to southeast through the state between Friday and Sunday. Precipitation chances begin Friday across the Upper Peninsula while generally sunny, dry conditions are seen across the Lower Peninsula. Clouds increase late Friday into Saturday in the south as the boundary sinks southeast and precipitation comes in the forecast. Precipitation may linger in the south Sunday; however, dryer weather moves in late as high pressure settles in from the northwest.

Wildfires persist far to our northwest in Canada and smoke models show a plume sinking in from the northwest behind the weekend front. The smoke plume does not look dense enough to cause significant increases in PM2.5 concentrations, but readings in the upper Good to low Moderate range are possible. We will keep a Moderate forecast Saturday and Sunday as a conservative measure, and levels by Monday are anticipated to fall back into the Good range.

Sunny skies and southwesterly winds in the south Friday are typically conducive for ozone development, but cooler temperatures and less daylight this time of year help keep levels generally Good. Increased clouds and precipitation chances Saturday into Sunday allow for Good readings to continue. Conditions dry out for the start of the new work week, but Good ozone persists thanks to cooler temperatures from northerly winds. 

EXTENDED FORECAST: Extended models show dry weather through midweek with warming temperatures during the period. If this forecast remains on track, pollution levels may increase into the low Moderate range.

Next Forecast Update: Monday, September 18, 2023