Central and eastern Maricopa County have heavier cloud cover this morning and will help limit ozone production as more is expected to move in later this morning. Yesterday one location reached the Moderate AQI category. With the cloud cover and expected rain, ozone is forecast to stay in the Good AQI range today and tomorrow. After, drier conditions will return with more sunshine, and daily ozone values will be in the Moderate AQI range through the weekend.

A few locations saw Moderate PM10 values in the Moderate AQI range yesterday mostly due to overnight and early morning activity from lingering storms or industrial activity. Today will be a difficult forecast as storms start to develop and move across the area today. As of now, there is enough of a probability that there will be dust in the late morning and early afternoon across Maricopa County, and this is noted in the hourly forecast. However, the duration of the dust will have more variability as moderate to heavy rain is possible and could limit further dust production. Either way, more sites are expected to see enough PM10 increases to reach the Moderate AQI category today. After the showers and storms finish early tomorrow morning, short-lived PM10 based increases will largely be from industrial activity and construction. PM10 is expected to return to the Good AQI category tomorrow and through the weekend. PM2.5 will follow similar trends.

- A. Hermansen
ADEQ Meteorologist