FORECAST SUMMARY: Friday, February 23, 2024, through monday, February 26, 2024

PM-2.5: 24-hour daily average Fine Particulate concentrations are expected to range between Good and low Moderate through the forecast period.

FORECAST DISCUSSION: Fine particulate levels on Thursday were running high across the southern half of lower Michigan thanks to an inversion that lingered through the day, causing pollution to increase at ground level. Hourly fine particulate readings reached the USG range for a portion of the day; however, only one monitor ended up reaching low-end USG for the daily average; most other sites ended the day in the middle to upper Moderate range. Pollution levels are improving today, Friday, thanks to a frontal boundary dropping in. This front will bring in cooler temperatures for the end of the week, along with small chances for snow showers. This cooldown will be short-lived, as a warmup is already anticipated for Sunday.

Hourly readings of fine particulate Friday morning range from Good further north to Moderate in southern locations. As the front passes during the day, winds pick up from the northeast, which will bring hourly concentrations back into the Good range statewide. Daily averages of fine particulate are expected to be mostly Good Friday, aside from a possible low-Moderate lingering in the southeast.

Cooler temperatures move over the state Friday and Saturday as surface high pressure moves in behind the cold front. Temperatures will fall during the day on Friday, and highs on Saturday will be below normal for this time of year. Weaker winds will be in place Saturday as the high slides overhead, but fine particulate should remain mostly Good for the day. Stronger southerly winds develop on Sunday, rebounding temperatures from the cool Saturday. Wind speeds should be strong enough to keep the atmosphere well-mixed, allowing for a continuation of mostly Good fine particulate levels.

EXTENDED FORECAST: Extended forecast models show a weak system passing northeast of the state late Sunday, decreasing wind speeds for a time early Monday. Stronger southwest winds move in quickly behind it, and a warmup is still in the forecast for early to mid-week. Without a stagnant period anticipated in the long term, pollution levels into next week should remain in the Good to low Moderate range.

Next Forecast Update: Monday, February 26th, 2024