FORECAST SUMMARY:
Wednesday, July 8th, 2020 through Monday, July 13th, 2020
OZONE: 8-Hour average Ozone concentrations will be Moderate with a good chance of USG along the southern tier counties of Lake Michigan and Southeast Michigan during Thursday, then transitioning from Moderate to Good during Friday. Conditions should be Good during the weekend.PM-2.5: 24-hour average Fine Particulate concentrations will range from Good to Moderate.
AN ACTION DAY ADVISORY IS ISSUED FOR WEDNESDAY and THURSDAY FOR THE FOLLOWING MICHIGAN COUNTIES...
WEST MICHIGAN
ALLEGAN... BERRIEN… CASS… KENT... MUSKEGON... OTTAWA… AND VAN BUREN COUNTIES; AND
SOUTHEAST MICHIGAN
LIVINGSTON… MACOMB… MONROE… OAKLAND… ST. CLAIR… WASHTENAW… AND WAYNE COUNTIES
FORECAST DISCUSSION
Hot, sunny weather is expected to continue through Thursday before relief arrives in the form of a cold front during Friday. Tuesday experienced ozone concentrations in excess of 70 ppb in both Southeast Michigan and West Michigan, although Southeast Michigan has been getting hit harder during this episode. While light winds have slowed the Chicago plume from impacting West Michigan too severely, it has hurt Southeast Michigan where wind stagnation has caused an accumulation of bad air.
As a result, we will be keeping the Action Day advisories in place through Thursday in both areas. Pop-up shower activity is increasingly possible during Wednesday and Thursday that would provide localized cleanout, but not enough to completely clean out the problem areas.
The expected cold front will arrive along the West Michigan shoreline around 8AM Friday morning and slowly progress across the state. There is some slight concern that Southeast Michigan will not see the cleanout benefit of the front before Friday concentrations elevate but clouds and shower actively ahead of the front should keep those concentrations in check.
Clean, cooler air will follow the front and eliminate the need for further advisories during the weekend. I do expect another low-pressure system to pass over the state during Sunday and follow with more clean air on Monday. As such, I think this forecast should be good through the weekend. Should conditions change significantly, we will update this forecast, as necessary.
EXTENDED FORECAST:
Air Quality should be mostly Good at the start of the next work week.