Dust Risk-Based Forecast | Maricopa County

Saturday

Stagnation: Morning and evening stagnation

Wind: Southwest winds of 5-10 mph

Sunday

Stagnation: Morning and evening stagnation

Wind: Southwest winds of 5-10 mph

Monday

Stagnation: Morning and evening stagnation

Wind: Southwest winds of 10-15 mph; outflow winds possible

Tuesday

Stagnation: Morning and evening stagnation

Wind: Light westerly winds

Wednesday

Stagnation: Morning and evening stagnation

Wind: Light westerly winds

Forecast Discussion:

Today through the weekend, a trough of low pressure is expected to develop along the West Coast, with the large ridge of high pressure moving eastward and centering itself over the southeast portion of the United States. This pattern will bring a drier southwest to northeast flow to the region, meaning thunderstorm chances in Phoenix will be minimal today into this weekend. With that said, we may see some storms try to approach the far E/NE Valley this afternoon, with some gusty outflows winds possible as well, but the chance of storms in the Valley will only be slight.

By July 4th into next week, the trough will begin to shift northeast as the high moves back to the west. This shift may set up a more southerly flow allowing for a slight increase in thunderstorm chances by the 4th as moisture increases. This will also increase the risk of outflow winds in the Valley, which may produce blowing dust.

As for air quality, expecting similar conditions today as yesterday, and with two monitors exceeding the federal health standard for ozone yesterday, it will be very likely again today, so an Ozone High Pollution Advisory is in place. Tomorrow through July 4th, expect enough southwest breezes at the surface and stronger winds just above the surface to help keep ozone below the federal standard, so no High Pollution Watches or Advisories will be in place this weekend. By Tuesday of next week, with lighter winds as the high moves back westward, expecting ozone values to once again rise, so an Ozone High Pollution Watch will be issued.

The other air quality concern will be July 4th itself. While we do not typically exceed from July 4th festivities alone, PM-2.5 (smoke) levels do normally rise during the evening hours, and that is expected to be the case this year as well. We could also see some outflow winds producing some blowing dust during the late afternoon/evening hours on July 4th. Stay alert to quick changes in weather conditions if you have outdoor plans!

Have a great weekend!

- M. Pace
ADEQ Meteorologist