An Ozone High Pollution Advisory is in effect for Maricopa County on Saturday and Sunday. Surface stagnation and mostly clear skies will result in an environment conducive for ample ozone formation in the more populated areas of the Phoenix metro. Let's discuss the upcoming weather.

For today, a weak disturbance will supply persistent southwesterly breezes throughout the afternoon with similar ventilation rates to yesterday. By tomorrow (Saturday), ventilation and winds will decrease, resulting in stagnant conditions and increasing temperatures in the valley. Sunday will be similar, with even higher temperatures approaching the upper 90s.

Early next week, active weather will make a return to the desert southwest. Though rain chances will be minimal, ventilation will increase enough to allow ozone levels to drop back into the upper Moderate AQI category.

In regards to air quality, Saturday and Sunday will be the main area of concern as ozone levels are forecast to exceed the federal health standard. Levels will be highest during the afternoon hours, dropping back into the green by nightfall. Particulate matter will be mainly locally driven, with levels dropping over the weekend as traffic activity decreases compared to the work week.

Have a safe and hydrated weekend as the heat makes its return to the desert.

- B. Droppleman
ADEQ Meteorologist