Phoenix Forecast

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Air Quality Hourly Forecast | Phoenix

Click on each day to view forecast.

Tuesday Forecast:

Alert: Ozone High Pollution Advisory in effect for Tuesday
Notice: Evening Isolated Blowing Dust Possible

Ozone

105 AQI
Max 8-hr Avg: 72 ppb

PM10

55 AQI
24-hr Avg: 63 µg/m3

PM2.5

32 AQI
24-hr Avg: 7.6 µg/m3

Wednesday Forecast:

Alert: Ozone High Pollution Advisory in effect for Wednesday
Notice: Evening Isolated Blowing Dust Possible

Ozone

105 AQI
Max 8-hr Avg: 72 ppb

PM10

57 AQI
24-hr Avg: 68 µg/m3

PM2.5

34 AQI
24-hr Avg: 8.1 µg/m3

Thursday Forecast:


Ozone

74 AQI
Max 8-hr Avg: 62 ppb

PM10

52 AQI
24-hr Avg: 58 µg/m3

PM2.5

31 AQI
24-hr Avg: 7.5 µg/m3

Friday Forecast:


Ozone

77 AQI
Max 8-hr Avg: 63 ppb

PM10

51 AQI
24-hr Avg: 56 µg/m3

PM2.5

31 AQI
24-hr Avg: 7.4 µg/m3

Saturday Forecast:


Ozone

80 AQI
Max 8-hr Avg: 64 ppb

PM10

48 AQI
24-hr Avg: 52 µg/m3

PM2.5

32 AQI
24-hr Avg: 7.6 µg/m3

Air Quality By Pollutant:

Pollutant
Tuesday
7/23/2019
Wednesday
7/24/2019
Thursday
7/25/2019
Friday
7/26/2019
Saturday
7/27/2019
O3
105
105
74
77
80
PM10
55
57
52
51
48
PM2.5
32
34
31
31
32
Pollutant
TUE
WED
THU
FRI
SAT
O3
105
105
74
77
80
PM10
55
57
52
51
48
PM2.5
32
34
31
31
32
O3 = Ozone, PM10 = Particles ≤ 10 microns, PM2.5 = Particles ≤ 2.5 microns

Forecast Discussion:

The Valley ran the gamut for weather and air quality alerts on Monday as the monsoon made its presence known across the lower deserts during the evening hours! Severe thunderstorms, locally heavy rain, blowing dust, and a sky painted with lightning and heard by thunder marked the late arrival of our summer thunderstorm season.

A dust storm was triggered south of the city from thunderstorm outflow winds between Tucson and eastern Pinal County. The dust storm having winds approaching an impressive 50 mph was tracked moving northward and crossed the metro area between 7:30 and 9:00 PM. Dense dust was observed resulting in a peak 5-minute PM10 average of 8,983 micrograms per meter cubed (ug/m3) at the Buckeye monitor! The second highest 5-minute average was 5,811 ug/m3 observed at the Higley monitor on the other side of the Valley near Queen Creek. Many other monitors had brief spikes in the 1,000 plus range, as well. To put those values in perspective many monitors were running between 30 and 50 ug/m3 before the dust storm swept in.

The far reaching impacts stretching between the West and East Valley show how widespread the blowing dust ended up being. The Buckeye location was the only spot exceeding the PM10 federal 24-hour average standard at 237 ug/m3 or 142 AQI (the standard is 150 ug/m3).

Despite the transported dust, no 24-hour PM2.5 exceedances occurred. A typical percentage of windblown dust generated PM2.5 to PM10 is about 15 percent. This is why large dust storms can affect both PM10 and PM2.5 federal standards (i.e., "coarse" and "fine" particulates, respectively).

The variety of significant weather over Phoenix prevented air quality from being worse than what it could have been. The same outflows kicking up dust also provided enough lift in the atmosphere to generate measurable rain for much of the area. That was key! It was not a lot (under a tenth of an inch for the most part), but enough to settle a majority of airborne dust and prevent lingering haze through the overnight hours. Really, air quality pollutant concentrations are very low at the moment with the sunrise. The exception being normal particulate jumps at sites associated with workweek activities (e.g., West 43rd monitor).

Moving forward, an active monsoon pattern stays with us this week. The important difference now is all that measurable rain falling between Maricopa, Pinal, and Pima Counties on Monday. It is not to say that pockets of blowing dust can’t yet occur. The significant and widespread blowing threat is much lower, though. The PM10 High Pollution Advisory for today will be cancelled due to the stabilization of desert dust sources and anticipation for additional rain in the coming days.

On the other hand, the Ozone High Pollution Advisory will continue today and be extended for Wednesday (July 24th). Rapid rises in ozone concentrations are possible under the weak wind dispersion pattern (outside of thunderstorms of course!) and current light easterly flow within the planetary boundary layer noted by today’s Phoenix weather balloon launch.

By Thursday, the shuffling of the upper level monsoon circulation creates deeper and faster westerly flow near the surface during the afternoon hours to help push the daily ozone plume eastward away from the city at a quicker clip.

Be sure to stay up to date with the latest air quality and monsoon forecast!

- J. Malloy
ADEQ Meteorologist


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