FORECAST SUMMARY:
Thursday, July 18th, 2019 through Friday, July 19th, 2019
...AIR QUALITY ACTION DAY ADVISORIES FOR THURSDAY JULY 18TH AND FRIDAY JULY 19TH...
IN WEST MICHIGAN:
ALLEGAN... BERRIEN… CASS… KENT... MUSKEGON... OTTAWA… AND VAN BUREN COUNTIES
Ozone: 8-hour Ozone concentrations will range between Good and Moderate with a threat for USG in the west and southeast.
PM-2.5: 24-hour Fine Particulate concentrations will be in the Good to Moderate range.
FORECAST DISCUSSION:
The easy part of the forecast is the fact that hot, humid conditions can be expected through Saturday with heat indices reaching over 100 degrees in several locations. The difficult part of the forecast is determining when and where storm complexes may develop the next few days.
A storm complex Thursday traveling west to east across southern Lower Michigan was expected to be further north. We currently have Action Days in place across southwest and southeast Michigan since yesterday’s models were showing dryer conditions with plenty of sunshine. The storms may hamper ozone from reaching USG today; but, if the sun breaks out after the system passes ozone may quickly develop in the hot, humid air mass.
We have decided to err on the side of caution for Friday’s air quality forecast and we are continuing the Action Days for both southwest and southeastern parts of the state. Southwesterly winds will prevail under the continued hot, humid air mass. Storm development chances look less for tomorrow and further north. The air quality forecast will be dependent on storm development; however, even just a few hours of afternoon into early evening sunshine could allow for fast increases in ozone. So, Action Days already set in place will be continued.
Fine particulate could also see increases the next few days with readings ranging from upper Good to middle Moderate.
EXTENDED FORECAST:
Extended models show hot conditions lingering through Saturday. Air Quality Division (AQD) forecasters will be holding another call Friday morning to discuss possible Action Days for Saturday. A front passing late Saturday should end the threat for increased pollution early next week.