Yesterday, ozone was able to exceed the federal health standard at one monitor--the Mesa monitor. Everywhere else in the Valley, ozone remained in the Moderate AQI category (though it was elevated in the afternoon).

Today, weather conditions will favor ozone formation and build-up in the Valley again. Winds even look to be a bit lighter than yesterday. Given yesterday's outcome, and today's outlook, an Ozone High Pollution Advisory has been issued for today. Ozone has the potential to exceed the standard again at one or more monitors.

For tomorrow, all else being equal, we would expect ozone to have the potential to exceed again. However, with a small low-pressure disturbance edging its way into Arizona from the west, better atmospheric ventilation should keep ozone levels slightly lower. Therefore, ozone is forecast in the Moderate AQI category.

Then by Friday, a much larger low-pressure wave will press into the region and result in even greater atmospheric ventilation, stronger winds at the ground, and increased cloud cover. Ozone levels will drop further. But, pockets of dust may be possible for dust-prone areas.

Then over the weekend, on Saturday, breezes will remain, so, lower ozone and pockets of dust are expected. But on Sunday, lighter winds will allow ozone to trend upwards again.

Check back tomorrow for the next update.

- M. Graves
ADEQ Meteorologist