Phoenix Forecast

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Air Quality Hourly Forecast | Phoenix

Click on each day to view forecast.

Friday Forecast:


Ozone

90 AQI
Max 8-hr Avg: 67 ppb

PM10

53 AQI
24-hr Avg: 59 µg/m3

PM2.5

47 AQI
24-hr Avg: 11.3 µg/m3

Saturday Forecast:


Ozone

67 AQI
Max 8-hr Avg: 60 ppb

PM10

45 AQI
24-hr Avg: 49 µg/m3

PM2.5

43 AQI
24-hr Avg: 10.2 µg/m3

Sunday Forecast:


Ozone

71 AQI
Max 8-hr Avg: 61 ppb

PM10

42 AQI
24-hr Avg: 45 µg/m3

PM2.5

42 AQI
24-hr Avg: 10.1 µg/m3

Monday Forecast:


Ozone

84 AQI
Max 8-hr Avg: 65 ppb

PM10

52 AQI
24-hr Avg: 58 µg/m3

PM2.5

48 AQI
24-hr Avg: 11.5 µg/m3

Tuesday Forecast:


Ozone

77 AQI
Max 8-hr Avg: 63 ppb

PM10

54 AQI
24-hr Avg: 61 µg/m3

PM2.5

46 AQI
24-hr Avg: 11.0 µg/m3

Air Quality By Pollutant:

Pollutant
Friday
9/18/2020
Saturday
9/19/2020
Sunday
9/20/2020
Monday
9/21/2020
Tuesday
9/22/2020
O3
90
67
71
84
77
PM10
53
45
42
52
54
PM2.5
47
43
42
48
46
Pollutant
FRI
SAT
SUN
MON
TUE
O3
90
67
71
84
77
PM10
53
45
42
52
54
PM2.5
47
43
42
48
46
O3 = Ozone, PM10 = Particles ≤ 10 microns, PM2.5 = Particles ≤ 2.5 microns

Forecast Discussion:

This morning (Friday), high pressure is elongated across the region, stretching from Northern Baja back up through Colorado. Water vapor also shows a trough of low pressure moving into the Pacific Northwest. This trough will continue moving eastward today and brush by Arizona to the north tomorrow, which will weaken the high and move it south and east. This pattern will help to increase breezes over the next couple of days, which is forecast to lower ozone concentrations in the Valley, compared to what we have seen over the past couple of days.

Sunday into the first part of next week, a broad area of high pressure will spread across the US, with the center located over the Plains. At the same time, another trough will position itself along the coast of the Pacific Northwest. This pattern is forecast to keep breezes just high enough to allow ozone to stay below the federal health standard. We will likely see a slight increase in clouds during this period, which will keep ozone slightly lower as well. Also, on average, ozone values this time of year begin trending down as day lengths become shorter. For reference, the average ozone for this time of year is right around 67 AQI, and just a month ago, the average was around 87 AQI.

As for wildfire smoke, expect a layer of smoke to remain over the region as it is trapped within or wrapping around the area of high pressure. By Sunday into Monday, we expect smoke to clear out of the region with a more south-southwesterly flow. As high pressure builds back into the West Coast Tuesday into the middle of next week, smoke may move back over the region as the flow becomes favorable for transport once again. This will, of course, be dependent on wildfire activity across the Western US. It should also be noted that this smoke is generally well off the ground (10,000 feet or higher), with very little to no PM-2.5 (smoke) impacts expected at the surface.

And last but certainly not least, let's talk about Monsoon. You might be wondering, is Monsoon 2020 over even though it officially does not end until September 30th? Well, the first question might actually be, did it ever start, but that is a topic for a different time. Typically during this time of the year, the Monsoon turns into more transition events, where monsoon moisture from the south interacts with winter-like storm systems that sweep through the state from the northwest. Right now, we do not see much in the way of moisture moving into the state to interact with weak troughs moving through the region. As a result, any storm systems that brush through the state through the end of September will likely only increase breezes from time-to-time with Phoenix remaining dry. Heading into the fall and winter months, we start to become more concerned with regional dust events. As strong but dry storm systems move into the Southwest US, they often result in strong gusty winds that produce widespread areas of blowing dust, especially considering how dry it has been this summer. Stay tuned, as we will keep you updated on any dust threats that move into the forecast.

Have a great weekend!

- M. Pace
ADEQ Meteorologist


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