Dust Risk-Based Forecast | Maricopa County

Saturday

Stagnation: Morning stagnation

Wind: Southwest winds of 10-20 mph in the afternoon

Sunday

Stagnation: Morning stagnation

Wind: Southwest winds of 15-25 mph in the afternoon

Monday

Stagnation: Morning and evening stagnation

Wind: Southwest winds of 5-10 mph in the afternoon

Tuesday

Stagnation: Morning and evening stagnation

Wind: West winds of 5-10mph

Wednesday

Stagnation: Morning and evening stagnation

Wind: West winds of 5-10mph

Forecast Discussion:

Yesterday (Thursday), Phoenix Sky Harbor hit a high of 102 degrees, making it the fourth time this year with a high of 100+. Just for fun, looking back at the number of 100 degree plus days from Jan 1st through May 13th, we already had 13 days last year, and the record for that period goes to 1989 with 15 days! So this year is certainly not as bad as it could be.

With that said, today will likely be the fifth day so far this year with a high of 100+ as high pressure still has a bit of control over our weather, although it is on the move. Satellite this morning shows high pressure moving east and is currently centered over New Mexico. This shift is in response to a very weak disturbance moving east through Southern California and another stronger system along the coast of the Pacific Northwest.

Today, the main influence from the weak system will be a slight increase in afternoon breezes. Skies will remain clear throughout the day and for the first part of the day into the early afternoon, expecting mainly light winds. This will likely be enough to increase ozone production and allow the 8-hour average to rise above the federal health standard before breezes increase later this afternoon. As a result, a High Pollution Advisory is in effect for Phoenix today.

This weekend, the stronger system currently in the Pacific Northwest will drop down the coast and into Arizona Sunday through Monday before moving eastward on Tuesday. This system will usher in cooler temperatures, with forecast highs lowering into the low 90s Sunday and Monday. It will also aid in increasing southwest winds into the 10-15mph on Saturday and into the 15-25 mph range on Sunday.

These increased breezes will be enough to limit ozone build-up in the Valley, so forecasting ozone levels to lower back into the Moderate AQI category (below the High Pollution Advisory/Watch threshold). We could see some patches of blowing dust, especially Sunday afternoon, with the stronger winds, so we have raised PM-10 concentrations during the afternoon hours.

Have a great weekend, and enjoy the slightly cooler temperatures coming in on Sunday!

- M. Pace
ADEQ Meteorologist