FORECAST SUMMARY:
Friday, July 17th, 2020 through Monday, July 20th, 2020
OZONE: 8-hour average Ozone concentrations will be mostly Moderate Friday and Saturday with a chance for USG, especially Saturday. Levels will be Good to Moderate Sunday and Monday.
PM-2.5: 24-hour average Fine Particulate concentrations will range from upper Good to low Moderate Friday and Saturday with mostly Good concentrations Sunday and Monday.
AN AIR QUALITY ACTION DAY ADVISORY IS ISSUED FOR SATURDAY JULY 18th FOR THE FOLLOWING COUNTIES:IN WEST MICHIGAN:ALLEGAN... berrien… CASS… KENT... MUSKEGON... ottawa… AND van buren COUNTIESIN Southeast MICHIGAN:LIVINGSTON… MACOMB… MONROE… OAKLAND… ST. CLAIR… WASHTENAW… AND WAYNE COUNTIESFORECAST DISCUSSION:
Hot, sunny conditions are expected as we come to the end of the week, and humidity levels will be quite high Saturday. A cold front passes the state Sunday with associated showers and storms expected late Saturday and Sunday ahead of and along the boundary. Conditions dry out Sunday behind the front and northerly winds should produce Good air quality early next week.
Until then, sunny skies coupled with south/southwesterly winds and warm temperatures both at the surface and upper levels will allow ozone to climb Friday. We are coming off a low background, so we are expecting most locations to be Moderate for ozone. But there is a chance a monitor or two could rise faster than anticipated reaching low-end USG along the western shore of Lake Michigan and/or in the southeast.
On Saturday, south/southwest winds increase in speed bringing in higher humidity; heat indices will approach 100 degrees across parts of the state. Mostly sunny skies continue, especially in the southeastern portion of the state. We will have another day of warm surface and upper level temperatures and ozone is expected to reach higher than the Friday increase. With the projected forecast, we feel there is enough threat for USG ozone Saturday to warrant issuing an Air Quality Action Day across the western lakeshore and in the southeast. What could prevent elevated ozone Saturday would be a very small chance for afternoon storm development, especially in the west. We do not feel this risk is high enough to not issue the action day, but any storm development would likely keep ozone from reaching USG.
Fine particulate may increase into the Moderate range Friday and/or Saturday with generally Good concentrations Sunday and Monday.
EXTENDED FORECAST:
Air Quality readings improve Sunday behind the front. Good ozone Sunday could reach into the Moderate range on Monday, but we do not anticipate elevated ozone early next week. If our thoughts on that changes, we will send a forecast update.
Forecast Updated by Stephanie M. Hengesbach July 17th, 2020.
Next forecast update: Monday, July 20th, 2020