FORECAST SUMMARY: Thursday, July 27, 2023, through Monday, July 31, 2023

 

OZONE:  8-hour average ozone concentrations are expected to be Moderate to USG through Friday, then Good to Moderate.

 

PM-2.5:  24-hour average Fine Particulate concentrations are expected to be Good to Moderate.

 

...AIR QUALITY ACTION DAY ADVISORIES FOR THURSDAY JULY 27 and FRIDAY JULY 28...

The Action Day Advisories include the following counties:

In West Michigan:

ALLEGAN...  berrien…  CASS…  KENT...  MUSKEGON...  ottawa…  AND van buren COUNTIES

 

In Southeast Michigan:

LIVINGSTON…  MACOMB…  MONROE…  OAKLAND… ST. CLAIR…  WASHTENAW…  AND WAYNE COUNTIES

 

 

FORECAST DISCUSSION

 

The forecast preparation for Friday has been particularly challenging.  There is a lot of uncertainty, both in the forecast models and the National Weather Service discussions, about when clouds and showers may arrive Friday afternoon or evening.  A front will be dropping down from the north, during the day, bringing those clouds and showers along the way but the timing is unclear. 

 

The majority of the ozone models are still predicting areas of elevated ozone along the southwest shores of Lake Michigan and southeast Michigan.  The cloud models are inconsistent on when we can expect clouds to move into the same areas which would retard ozone production.  It is more likely that southeast Michigan will stay under clear skies longer than southwest Michigan.  But if southwest Michigan also stays sunny through the afternoon, their ozone production could be significant.

 

As elevated ozone could be significant in both areas, I will continue the Thursday Action Day advisories into Friday.  Even if clouds do move in and keep ozone levels out of the USG range, I will still be satisfied that this was the correct call on the side of caution.

 

Either way, the front dropping down from the north will occur Friday night putting an end to this episode.  There does not appear to be any continued threat from either smoke or ozone for the remainder of the weekend, although I will continue to monitor conditions.  As such, I do not anticipate the need for another forecast update until Monday.

 

 

EXTENDED FORECAST:

 

Air Quality should be generally Good to Moderate for the weekend and into the next work week.

 

Forecast updated by Jim Haywood: Thursday, July 27, 2023

Next forecast update Monday, July 31, 2023