FORECAST SUMMARY: Friday December 15th, 2023, through Monday December 18th, 2023

PM-2.5:   PM-2.5 concentrations are expected to be in the Good to Moderate range.

FORECAST DISCUSSION: Today, Friday, will see almost spring-like temperatures with highs nearing the 50s for most of the state. The majority of the lower peninsula has these temperatures coupled with clear skies, with the upper peninsula, however, seeing periodic rain for today and much of the weekend. This rain hangs around the region the entire weekend and slowly makes its way southward through Saturday and Sunday. A Low-pressure system lingering in the Midwest is the culprit for the weekend-long rain and cloudy conditions. As the Low-pressure moves off to the east on Sunday, a cold front drifts down from the north, which will drop temperatures back into the normal range of the low-30s. During the transition period of warmer temperatures to cooler, any precipitation that is still falling may turn into a wintry mix, but no real accumulation is expected. The combination of the aforementioned Low-pressure system moving to the east, and two High-pressure systems to the northwest and southwest will cause windy conditions on Monday for much of the Midwest, especially here in Michigan. As differing pressure systems move closer together (i.e., Low-pressure system and High-pressure system), the pressure gradient between the two becomes tighter. When the pressure gradient becomes tighter, this is what causes wind to pick up as wind goes from higher pressure to lower pressure. The pressure gradient being “squeezed” will only last for a day as Tuesday presents us with a change in airmass and pressure systems.

PM-2.5 concentrations currently are in the Moderate range as we have relatively stagnant conditions throughout the state. These concentrations may last through the day and into tomorrow until the wind picks up into the weekend. The more populated areas like Detroit and Grand Rapids will see higher Moderate concentrations compared to other areas in the state today and into tomorrow before the wind picks back up. There is currently no driver of dispersion, so the particulate matter is hanging around near the surface. As we get later into tomorrow, however, we will see plenty of airmass changes, rain, and wind so PM-2.5 will predominantly be in the Good category but expect hourly concentrations in the Moderate range in the aforementioned populated areas.

EXTENDED FORECAST:

After the breezy Monday conditions, temperatures start to rise again on Tuesday with overall Good air quality.

Next Forecast Update: Monday, December 18, 2023