FORECAST SUMMARY:

Friday, July 24th, 2020 through Monday, July 27th, 2020

OZONE: 8-hour average Ozone concentrations will range from Good to Moderate through Sunday, with Good readings Monday.

PM-2.5: 24-hour average Fine Particulate concentrations will range from upper Good to low Moderate through the forecast period.

FORECAST DISCUSSION:

Sunny conditions Friday will make a pleasant day, and easterly winds hamper any pollution build up. On Saturday, southwesterly winds develop as high pressure moves east of the region. Temperatures at the surface and upper levels will increase, along with humidity levels. A frontal boundary moves in Sunday bringing chances for precipitation from northwest to southeast as the day progresses. Precipitation chances linger into Monday as the boundary sinks southeast.

As for air quality, Good conditions have been in place and we are starting Friday with a clean background. Easterly winds at the surface and upper levels should keep ozone from increasing much; readings will range from Good to low Moderate. Winds become more conducive for ozone development Saturday, but with coming off such a low background we do not expect levels higher than upper Moderate.

While we don’t feel the threat for elevated ozone is high enough this weekend to warrant Action Days, there is a small chance that a monitor or two Saturday will increase faster than anticipated reaching low-end USG. If this happens it would most likely be along the lakeshore of west Michigan and/or in the southeast upwind of the Detroit area.

With the current timing of the front, increasing clouds Sunday and precipitation moving in as the day progresses should keep ozone from reaching higher than Moderate. If the front slows down keeping mostly sunny skies during the day, then there is a possibility for isolated USG readings in the southwest and/or southeast. Even without an Action Day, we will update the AirNow forecast to USG Saturday or Sunday mornings if we feel the USG threat becomes higher than anticipated.

Fine particulate has been Good most of this week. Good levels will linger Friday with a mix of Good to low Moderate expected until the front passes Monday.

EXTENDED FORECAST:

Northwesterly winds develop Monday after the cold front passes. The cooler, cleaner air will produce Good air quality early next week.

Forecast updated by Stephanie M. Hengesbach
Next forecast update: Monday, July 27th, 2020