Ozone High Pollution Advisory for Maricopa County

 What is an High Pollution Advisory (HPA)?

A High Pollution Advisory (HPA) is issued when it is imminent or there is a high probability for ozone or PM levels to exceed the federal health standard for Clean Air 

Arizona Air Quality Information

Published on: 04/17/2023 at 10:54 AM by M. Pace

Phoenix: First ozone exceedance of 2023

You can't see it because it's invisible, but it is that time of year again to pay attention to ozone in the Valley of the Sun.
Yesterday (Sunday), ozone exceeded the federal health standard for the first time this year, and this is the first exceedance since September 8th, 2022. 

The average (2010-2022) first exceedance day of the year is April 20th, so we are ahead of the average by just a bit. On the flip side, the earliest first exceedance was February 16th, 1981, and the latest first exceedance occurred May 5th, 2021.

It is not a shock to see ozone rise 

as it is the highest from May through September due to several factors,

 including longer day lengths allowing ozone more time to form and stagnant conditions that develop as high pressure moves overhead.

Air Quality By Pollutant:

Pollutant

Friday
7/14/2023

Saturday
7/15/2023

Sunday
7/16/2023

Monday
7/17/2023

Tuesday
7/18/2023

O3

101

105

108

87

80

PM10

54

43

36

51

53

PM2.5

45

36

34

33

34

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

Notice:
The Maricopa County Air Quality Department has issued a No Burn Day for today, 7/16/2023. Full Details >

Forecast Discussion:

After three days of dormancy, signs of returning ozone appeared yesterday as hourly levels rapidly increased through the late morning hours. Fortunately, due to afternoon westerly winds enveloping the area, ozone levels quickly fell by 2:00pm, coming in the low Moderate AQI for the day.

With yesterday's ozone trends in mind, in addition to winds decreasing day by day through the weekend, today's Ozone High Pollution Advisory for Maricopa County will also carry over to tomorrow and Sunday.

High pressure is currently situated overtop central California, and is expected to build and slowly propagate to the east, centering over Arizona by early Monday morning. 

• Increased surface pressure means more surface stagnation, and higher surface temperatures, reaching near 120°F by tomorrow afternoon and persisting through the first half of next week.

Apart from the intense heat, Phoenix has seen the third day in a row of dew points above 55°F, marking the official beginning of the 2023 monsoon season in Phoenix back on July 11th. 

• The absence of rainfall however has been the main story over the past month, as monsoonal conditions have struggled to materialize in the desert southwest. 
• However, looking towards the end of our forecasting period, high pressure overtop Arizona may induce southeasterly flow by early next week, providing the first real chance for thunderstorms to reach the valley this summer. Temperatures are still expected to be high, but late afternoon cloud cover and possible outflow winds may help to ease the prolonged heat.

As for air quality, next week's monsoonal setup is expected to lower daily ozone levels with the help from afternoon cloud cover. 

• Due to chances of thunderstorms making it to the metro area, elevated evening PM10 (dust) will become a factor as outflow boundaries may cause blowing dust. 
• Though we are still relatively far out forecast wise, predictability is always up in the air when considering monsoon past three days.

Be sure to check in with us on Monday for our latest forecast on this monsoonal thunderstorm potential.

Have a safe and hydrated weekend!
- B. Droppleman
ADEQ Meteorologist 

Media Contacts

Ari Halpert
Communications Department Officer
Maricopa County Air Quality Department
Ari.Halpert@maricopa.gov
602-506-6713
301 W. Jefferson St., Suite 410
Phoenix, AZ 85003