Today's ozone is forecasted to be lower than yesterday as rain has already arrived in parts of Phoenix. The rain will move out of the area later this evening, and Saturday will be mostly dry, besides a few isolated cells that could form in the afternoon. There will be a slight increase Saturday because a majority of the day will be dry. Rain returns Saturday evening and it will be more widespread than today. This will once again drop ozone levels. The rain will end late Sunday/early Monday, this drier conditions and an increase in daily ozone levels through early next week.

PM10 is already seeing lower values than normal this morning as the rain has begun. The scattered thunderstorms will continue through the afternoon and evening, with eastern Phoenix seeing it the longest as it moves east. On Saturday there may be isolated cells, but overall there will be dry conditions with lighter winds. More steady rain arrives Saturday evening, and this is forecasted to keep the dust concentrations lower once more into Sunday. Drier conditions return on Monday, and there will be a gradual increase in daily PM10 values, including increases from local activity in the mornings. Daily Good AQI values are forecasted for PM10 through early next week.

Daily PM2.5 values will have similar trends to PM10. When both cooler temperatures and drier conditions are present next week, more wood burning is expected to stay near the surface. This will increase daily PM2.5 values to the upper Good and low Moderate AQI range.

- A. Hermansen
ADEQ Meteorologist