Phoenix Forecast
AQI Scale
Air Quality ISSUED ON: Wed. Sep 20, 2017
This report is updated Monday through Friday and is valid for areas within and bordering Phoenix, Arizona
Today | Wednesday 9/20/2017
54
PM10
MessageHealth Statement:Unusually sensitive people should consider reducing prolonged outdoor exertion.
Tomorrow | Thursday 9/21/2017
91
PM10
MessageHealth Statement:Unusually sensitive people should consider reducing prolonged outdoor exertion.
Notice:Late Day Haze - Blowing Dust Possible
Extended | Friday 9/22/2017
63
PM10
MessageHealth Statement:Unusually sensitive people should consider reducing prolonged outdoor exertion.
Notice:Early Day Haze Possible
Extended | Saturday 9/23/2017
71
Ozone
MessageHealth Statement:Unusually sensitive people should consider reducing prolonged outdoor exertion.
Extended | Sunday 9/24/2017
80
Ozone
MessageHealth Statement:Unusually sensitive people should consider reducing prolonged outdoor exertion.

Air Pollutant Breakdown
Pollutant Yesterday
9/19/2017
Wednesday
9/20/2017
Thursday
9/21/2017
Friday
9/22/2017
Saturday
9/23/2017
Sunday
9/24/2017
O3 58 51 50 54 71 80
CO 7 8 7 6 7 8
PM10 55 54 91 63 32 34
PM2.5 28 30 30 46 25 26
O3 = Ozone, CO = Carbon Monoxide, PM10 = Particles 10 microns and smaller, PM2.5 = Particles smaller than 2.5 microns

Synopsis & Discussion
Forecaster: -J. Malloy
Forecasted weather and air quality for today is on track: Seasonable temps, mostly sunny skies, afternoon breezes, and upper Good to lower Moderate AQIs for particulates and ozone. Eyes are on that Pacific trough over the Northwest U.S. and how it will evolve over the next 48 hours, which is projected with a high degree of confidence to occupy the entire western U.S. and swing southward into Arizona tomorrow through Friday.

Significance of the weather system and its cold front is going to come in the form of widespread gusty winds (20 to 30+ mph) and blowing dust potential for desert locales. Little to no recent rainfall has fallen over central parts of the state for a while. Southern California would be in the same boat. Thinking a combination of both long-range dust transport from the Lower Colorado River Valley and local dust generation off nature sources near Phoenix is plausible Thursday; enough so to warrant a PM-10 Health Watch issuance for the Phoenix area. After the dry cold frontal passage, winds near the surface on Friday back down, though a haze could linger for the first part of the day elevating particulate AQIs (both coarse and fine varieties).

Regarding ozone, over the last couple of days we are seeing signs of ozone transport aloft from California ahead of the aforementioned trough based on spikes in hourly readings at higher elevation monitoring sites in the state (i.e., Prescott, Flagstaff, and Humboldt Mountain). Impacts at lower elevations monitors within Metro Phoenix are not being noticed, or at least any contribution from transport is being offset by breezier daytime winds. The ozone AQI forecast to start next week will show an upward trend once atmospheric dispersion drops in the wake of the Pacific trough.


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"


Main Office
1110 W.Washington Street
Phoenix, AZ 85007
P: 602.771.2300
azdeq.gov