FORECAST SUMMARY: Thursday, April 13, 2023, through Friday, April 14, 2023
OZONE: 8-hour average ozone concentrations are expected to be Moderate to USG through the forecast period.
PM-2.5: 24-hour average Fine Particulate concentrations are also expected to be mostly Good to Low Moderate through the forecast period.
FORECAST DISCUSSION:
While highly unusual for mid-April, conditions under a slow-moving high-pressure system have created conditions for elevated ozone, this week. The past few days have seen 1-hour concentrations in the low 70 ppb range and 8-hour averages in the mid-60 ppb range. While Thursday is expected to be similar, Friday has changes which create concerns for even higher ozone development.
Of concern are lower wind speeds which will allow for stagnation rather than the well mixed atmosphere under the breezy conditions of the past few days. This will affect SE Michigan the most. Winds will become more southerly which will allow pollutants to stay out over Lake Michigan longer and have a better chance for additional photochemical reaction. An afternoon lake breeze could bring those higher concentrations inland. The other Lake Michigan states are also posting USG warning along the lake shore, as well. In SE Michigan, the ozone plume will be pushed north of Detroit rather than to the east.
As a result of these concern, Air Quality Advisories are being issued for the Lake Michigan shore from the Indiana boundary up to Leelanau County and the seven counties that make up SE Michigan.
The models are showing increasing clouds on Saturday which should make this a one-day event. However, if the approaching system slows, Saturday may still be in play. As such, the forecast will be updated Friday morning.
EXTENDED FORECAST:
Air Quality should be mostly Good begin the next work week.
Next Forecast update: Friday, April 14, 2023