FORECAST SUMMARY: Saturday, July 3rd, 2021, through Tuesday, July 6th, 2021
OZONE: 8-Hour average Ozone concentrations are expected to range from Good to Moderate.
PM-2.5: 24-hour average Fine Particulate concentrations will also be in the Good and Moderate range.
FORECAST DISCUSSION:
The forecast is on track with generally sunny skies and warming temperatures this July 4th weekend. There is usually a bright blue sky in the current weather set-up, but it may look a bit hazy the next few days. That can be attributed to wildfire smoke sinking south from fires in Canada. The next weather system is a frontal boundary moving in later Monday. This system should bring some clouds later in the day and small chances for precipitation into Tuesday
For air quality, as mentioned wildfire smoke is traveling in from the north/northwest. While much of the plume should stay at upper levels, there is the possibility some may mix down increasing fine particulate concentrations into the Moderate range for a period of time. Because of this, they are forecasting Moderate fine particulate for the next two days. Another reason for a Moderate forecast increases in fireworks displays in celebration of the July 4th Holiday. These displays will cause short-term high spikes in fine particulate for a few hours afterward that could, in turn, allow for Moderate daily averages.
For ozone, there is currently a low background in place thanks to the stronger northwesterly winds the past few days. While surface and upper-level temperatures will continue to increase, the wind field remains from a non-conducive direction through most of Sunday. There is a small chance for a monitor or two right along the west Michigan lakeshore to reach low-end USG, but they do not foresee any widespread ozone concerns through July 4th.
A frontal boundary sinks closer to the region Monday. While winds turn more southwesterly, clouds look to move in early enough to hamper a significant ozone development. This is something that will be keeping an eye on, but for now, we are forecasting Moderate ozone Monday. They plan to take a look at weather maps again Sunday morning and will update this forecast if our thoughts change and we feel ozone concentrations higher than Moderate become a concern. The smoke plume forecast will be monitored and updated this forecast if warranted.
EXTENDED FORECAST:
The system dropping in from the north later Monday/early Tuesday should bring in cooler temperatures and cleaner air. Air quality by Tuesday should improve towards the Good range.