Today, conditions look favorable for ozone levels to increase and potentially exceed the health standard in Phoenix. Therefore, an Ozone High Pollution Advisory has been issued for today. Highest ozone levels are expected during the afternoon.

Then by tomorrow and beyond, ozone levels are forecast to decrease, thanks to better winds (i.e. better atmospheric dispersion). This will be especially true for the weekend, as a large low-pressure wave migrates into the continent from the Pacific Ocean. During this time, ozone is still forecast in the Moderate AQI category each day. But, we'll watch for any changes in daily trends.

As for PM10 (dust), we have more to talk about other than the usual mention of "local activity." Yes, PM10 will be highest in industrial areas south/southwest of the Phoenix metro area, particularly on weekday mornings. And yes, the hourly forecast graphs above reflect this. But, we will also have the possibility of dust this evening from winds from thunderstorms over eastern Arizona. Furthermore, dust could be possible again Thursday evening from breezes originating from the Gulf of California.

Lastly, stronger daytime breezes over the weekend could result in dust for dust-prone areas.

As for PM2.5 (smoke), PM2.5 will be locally driven in the mornings and generally follow PM10 trends.

Check back tomorrow for the next update to the Phoenix forecast.

- M. Graves
ADEQ Meteorologist