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phoenix haze

Hazy skies expected to persist as wildfires push smoke and dust into Arizona

A hazy morning over downtown Phoenix as seen from Camelback Mountain on Sept. 8, 2020. (Photo: Thomas Hawthorne/The Republic)

Skies across Arizona turned a hazy gray on Tuesday after smoke from several massive California wildfires streamed into the Southwest.

Skies are expected to get even murkier as a storm system quickly approaches northwest Arizona, bringing gusty winds that could kick up dust, according to weather officials. The sky will likely clear up slowly over the next several days at the same time that temperatures are forecast to drastically drop throughout the state.

California wildfires like the Creek Fire in the Sierra National Forest, which exploded to 135,000 acres Tuesday, are causing the smokey overcast, according to National Weather Service-Phoenix meteorologist Mark O’Malley. Before Monday, high pressure along the Arizona-Utah border kept at bay most of the smoke from one of the most extreme wildfire seasons our neighboring state has experienced.

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“The wind direction has shifted out of the northwest, and it’s streaming all of that smoke through the Southwest and through all of Arizona,” O’Malley told The Arizona Republic.

Fortunately, hazy skies do not necessarily mean air quality on the surface is bad, said Arizona Department of Environmental Quality spokesperson Caroline Oppleman.

“In the Valley, the vast majority of this smoke is well off the ground. As temperatures warm and winds increase, there is a chance some of this smoke will mix down to the ground; however, ADEQ air quality meteorologists are not expecting PM-2.5 (smoke) to exceed the federal health standard so no high pollution advisory will be issued,” Oppleman said in an email to The Republic. “With that said, you will likely see plenty of haze around the region.”

There are three factors that will help the Phoenix metro area’s air quality Tuesday and Wednesday, Oppleman said. First, steady breezes at the surface and higher up in the atmosphere will help prevent ozone from accumulating and ward off smoke pollution. Second, the thick smoke cover will help blot out some sunlight and heat, which can improve air quality. Finally, although wildfire smoke can often spell an increase in ozone, it doesn’t appear this will be the case this time around as areas upwind from Arizona did not see higher levels of the pollutant.

“With all of this combined, (we’re) forecasting ozone to remain in the Moderate AQI category throughout the week,” Oppleman concluded.

While an approaching storm front and California wildfires bring smoke and dust into the Arizona skies, no high pollution advisory will be issued.

Phoenix haze

O3 = Ozone, PM10 = Particles ≤ 10 microns, PM2.5 = Particles ≤ 2.5 microns

Forecast Discussion:

Satellite this morning shows a large fetch of clouds extending from the Southwestern United States back to just west of Hawaii. With not much change in the weather picture through the middle of Sunday, expecting these clouds to continue streaming overhead, especially tomorrow. Unfortunately, no rain will be associated with these clouds.

Late Sunday, through the day on Monday, a weak weather disturbance is expected to brush through the state. While rain chances will remain zero with this system, it will increase breezes slightly and begin to lower high temperatures back into the 70s.

As for air quality, today into the weekend, our main concern will be PM-10 and PM-2.5 values. It should be noted that 85 percent of the state is now in Extreme or Exceptional drought, which is the worst drought numbers we have seen since July 2002. These very dry conditions, combined with light winds, stronger morning inversions, and an increase in local dust and smoke production, both PM-10 and PM-2.5 values have been on the rise. Yesterday, the West 43rd PM-10 monitor in the south part of the Valley came in at 95 AQI (keep in mind, the federal health standard is exceeded at 101 AQI).

With stagnant conditions likely through late Sunday, PM-10 and PM-2.5 values are forecast to remain in the upper Moderate AQI category. By Monday, with some breezes in the forecast, it should help clear out the dust and smoke build-up just a bit, allowing values to lower slightly; however, they will remain elevated. Right now, we do not have any High Pollution Watches or Advisories in place, but we will be watching trends very closely.

Phoenix haze O 3 = Ozone, PM 10 = Particles ≤ 10 microns, PM 2.5 = Particles ≤ 2.5 microns Forecast Discussion: Satellite this morning shows a large fetch of clouds extending from the