[ADEQ Forecasts] ADEQ Daily Air Quality Forecast for Friday, August 21, 2009

[forecasts@lists.azdeq.gov]

For more information, please visit our Web page:
http://www.azdeq.gov/ensemble.pdf

For transportation alternatives:
http://www.valleymetro.org


Health message for Thursday, August 20: Unusually Sensitive People should consider limiting prolonged or heave exertion outdoors.

Health message for Friday, August 21: Unusually Sensitive People should consider limiting prolonged or heave exertion outdoors.


Synopsis and Discussion
As expected, the Monsoon pattern has indeed returned.  Moisture will increase significantly across the region from the south over the next 24 hours.  Several upper-level disturbances will also move northwest over the deserts through Sunday, enhancing thunderstorm activity even when the sun goes down.  Thus, there is a good chance for Valley rain over the next 72 hours, particularly Saturday afternoon into Sunday morning.  

As the storm pattern strengthens the next few days, the likelihood of blowing dust from distant storms to the south reaching the Phoenix forecast area will increase.  A good dust storm could impact the Valley Friday evening, possibly followed by an air clear shower.  This could send PM-10 levels into the upper "Moderate" range on Friday.

Ozone concentrations continue to be unseasonably low, with all but one monitor (Queen Valley) in the "Good" category on Wednesday.  As always, though, a shift in winds out of the east or southeast tends to trap local pollution and ozone precursors in the Valley, resulting in elevated ozone concentrations.  There's no doubt we will see plenty of sunshine on Friday.  The key will be how long and how strong the low-level easterly flow will be.  Current models suggest winds will shift out of the southwest by midday, which would allow the invisible ozone plume to push unimpeded out of the forecast area and towards the mountains in the east.  Any thunderstorm buildup along the Mogollon Rim would further aid this eastward movement of the ozone plume.  Thus, we are going to keep the forecast for ozone concentrations in the mid "Moderate" range for Friday.  Any clouds and showers on Saturday would shut down ozone generation, resulting in much lower maximum concentrations.  

Check back tomorrow for any changes to the weather and air quality.  Until then, have a good day!

If you have any questions or comments regarding this forecast please contact:

The Arizona Department of Environmental Quality
Office of Communications
1110 W Washington St, Phoenix, AZ 85007
(602) 771-2215
ms15@azdeq.gov


 
 

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