FORECAST SUMMARY:
Wednesday, July 3rd, 2019 through Monday, July 8th, 2019
...AIR QUALITY ACTION DAY ADVISORY FOR WEDNESDAY JULY 3RD... IN SOUTHEAST MICHIGAN:LENAWEE... MACOMB... MONROE... OAKLAND... ST. CLAIR... WASHTENAW... AND WAYNE COUNTIES
Ozone: 8-hour Ozone concentrations will range between Good and Moderate, with scattered USG possible.
PM-2.5: 24-hour Fine Particulate concentrations will range from upper Good to middle Moderate; USG is possible during the evening and overnight in areas with fireworks displays.
FORECAST DISCUSSION:
The weather forecast through Friday hasn’t changed much with warm, muggy conditions continuing, along with the chance for scattered storms. Storm chances Wednesday are confined more to the southern portion of the state closer to a frontal boundary. The threat for storms does increase for the July 4th Holiday and for Friday.
Ozone levels the past few days has increased in some locations, generally the southeastern and southwestern portions of the state. This trend could continue in areas that have more in the way of sunshine. With winds remaining lighter, the best chance for increased ozone Wednesday would be in the southeast and we have an Action Day in place to cover this threat. Storm chances increase Thursday and Friday. Conditions will be warm and southwesterly winds develop. A few locations may reach low-end USG if sunshine prevails; however, storms and associated clouds should stop levels from increasing higher than Moderate Thursday or Friday. An airmass change begins late Friday/Saturday with northeast winds developing as high pressure slides in from the northwest. This will improve ozone levels for Saturday.
As for fine particulate, levels have been ranging from Good to Moderate and this trend will continue. The caveat to this is areas near fireworks displays in celebration of the July 4th Holiday. Fine particulate will quickly increase into the USG range in those localized areas which could linger into the overnight hours.
EXTENDED FORECAST:
Extended models show high pressure in place early next week bringing pleasant conditions Sunday, into Monday. With plenty of sunshine and seasonable temperatures, Moderate ozone may develop; however, levels higher than that are not expected. Fine particulate should be Good early next week.