Phoenix Forecast
AQI Scale
Air Quality UPDATED: Thu. Apr 19, 2018 12:33 PM
This report is updated Monday through Friday and is valid for areas within and bordering Phoenix, Arizona
Today | Thursday 4/19/2018
89
PM10
MessageHealth Statement:Unusually sensitive people should consider reducing prolonged outdoor exertion.
Notice:Afternoon Blowing Dust - Regional Haze Possible
Tomorrow | Friday 4/20/2018
61
Ozone
MessageHealth Statement:Unusually sensitive people should consider reducing prolonged outdoor exertion.
Notice:Lingering Morning Haze Possible
Extended | Saturday 4/21/2018
87
Ozone
MessageHealth Statement:Unusually sensitive people should consider reducing prolonged outdoor exertion.
Extended | Sunday 4/22/2018
93
Ozone
MessageHealth Statement:Unusually sensitive people should consider reducing prolonged outdoor exertion.
Extended | Monday 4/23/2018
100
Ozone
MessageHealth Statement:Unusually sensitive people should consider reducing prolonged outdoor exertion.

Air Pollutant Breakdown
Pollutant Yesterday
4/18/2018
Thursday
4/19/2018
Friday
4/20/2018
Saturday
4/21/2018
Sunday
4/22/2018
Monday
4/23/2018
O3 126 87 61 87 93 100
CO 9 7 8 11 11 14
PM10 55 89 48 44 43 63
PM2.5 32 54 31 39 43 50
O3 = Ozone, CO = Carbon Monoxide, PM10 = Particles 10 microns and smaller, PM2.5 = Particles smaller than 2.5 microns

Synopsis & Discussion
Forecaster: -J. Malloy
Air quality has not been the best of late. Two days in a row for Valley ozone exceedances! It is not uncommon for us to observe exceedances at this point of the year. For instance, April 2017, there were seven days hitting that mark. Day lengths are only getting longer and recent westerly flow has given plenty of opportunity for ozone transport.

Today, residual ozone concentrations are high. A key difference between today and yesterday is much stronger winds by afternoon. The thought is a brief ramp up in ozone by early afternoon as mixing occurs adding to locally generated ozone and then a drop and plateau in concentrations as background versus local ozone contribution becomes dominant with widespread gusty winds.

Those gusty winds are an issue in terms of blowing dust affecting our PM-10 concentrations. Likeliest period of blowing dust is midafternoon and early evening before sundown. Southwesterly flow puts areas adjacent to open deserts and aligned with dry dust sources, such as the Salt River drainage, at higher risk to see blowing dust. Modelled air parcel trajectories also reveal an afternoon connection between Phoenix and southern California, where blowing dust is underway this morning. Long-range haze transport is on the horizon later today for us. Winds settle down along with PM-10 concentrations overnight. Any haze when we wake up gets kicked out with breezy northwesterly winds Friday.

Stagnation sets up Saturday, Sunday, and Monday. Local accumulation of pollutants, including ozone precursors, need to be watched. A jump in ozone well into the upper Moderate AQI range is forecasted. Stay tuned.

Interestingly, our next wind event is poised for next Thursday, which would be the third time in as many weeks getting a windy Thursday.


Useful Links
- Subcribe to the Forecast
- Yesterday's Monitor Data
- Year-to-Date Reports
- Maricopa County Air Monitoring Site
- Read current issue of "Cracking the AQ Code"


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1110 W.Washington Street
Phoenix, AZ 85007
P: 602.771.2300
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