Yesterday, ozone levels reached the Unhealthy for Sensitive Groups AQI category again, while PM10 and PM2.5 reached the Moderate category due to some blowing dust in the evening. Looking ahead at ozone, we expect similar conditions that will be conducive for ozone formation today, and that include regional smoke from wildfires in the Pacific Northwest and Canada. Therefore, we will continue to have an Ozone High Pollution Advisory in effect for today.

Beginning tomorrow, we are forecasting the ridge overhead to weekend, and winds aloft to shift more out of the southwest. Our thinking here is that these winds will help to clear out the smoke in Arizona, which should result in lower ozone concentrations. Therefore, we are forecasting ozone to drop into the upper Moderate range for the remainder of the forecast period.

As for PM10 and PM2.5, there will continue to be chances for outflow winds from thunderstorms this evening. However, there was a good amount of rain that fell yesterday, particularly to the south in Pinal County where many of the dust source areas are located. Therefore, we have lowered the PM10 and PM2.5 forecast into the Good AQI range today. After today, storm activity is forecast to die down, which should help keep particulate levels in the Good range through the rest of the forecast period.

We hope you have a great weekend!

- R. Nicoll
ADEQ Meteorologist