FORECAST SUMMARY: MondAY, December 1, 2023, through FRIDAy, December 4, 2023

PM-2.5:  24-hour daily average Fine Particulate concentrations will range between middle Good and middle Moderate through the forecast period.

FORECAST DISCUSSION:

The week ends on a quiet note across the Upper Peninsula and far northern Lower Michigan with weak high pressure dominating; however, conditions differ further south. Weather systems moving along a stalled boundary near the Michigan, Indiana, and Ohio borders bring cold rain in the forecast across southern Michigan, a mix of rain and snow in central locations, and primarily snow further north. The first of these is moving through early Friday, with a second expected late Friday into early Saturday. Each of these disturbances originates from the southern Plains States, tracking northeast into the southern Great Lakes region. A third moves in on Sunday, bringing yet another chance for rain and/or snow. The exact timing and placement of the systems as they move into the region will determine where liquid precipitation will fall in lieu of snow; however, at this time, none of them are expected to produce significant snow accumulations.

Good to low-Moderate daily concentrations of PM2.5 have been seen across the state this week. As often happens near frontal boundaries, concentrations are increasing into the Moderate range across the south early Friday. While a few hourly concentrations, primarily in the southeast, may reach low-end USG, this should be short-lived, with daily averages no higher than Moderate expected. The on-and-off systems through early next week should keep the atmosphere mixed, not allowing for long-term stagnant periods. Also, with the main systems tracking across the southern Great Lakes region, a primary easterly wind flow can be expected. However, without a good northerly wind flow in the wake of these disturbances, PM2.5 increases may not be entirely cleared, leading to Moderate readings at times. Daily averages of PM2.5 during this forecast period will likely remain between upper-Good and middle-Moderate.

EXTENDED FORECAST:

Extended models show dry conditions starting the new workweek, but another system is forecast to drop in from the northwest Tuesday. Air quality in the extended period is expected to continue to range between Good and Moderate.

Next Forecast Update: Monday, December 4th, 2023