[ADEQ Forecasts] ADEQ Daily Air Quality Forecast For Saturday, September 19, 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 Friday, September 18: Unusually sensitive people might want to consider limiting prolonged or heavy exertion outdoors.

Health message for Saturday, September 19: No health impacts are expected.


Synopsis and Discussion
High pressure over the upper Midwest, extending southwest towards Arizona will be pushed east later this weekend.  This will allow a strong area of high pressure to develop off the coast of California.  This means we can expect to see much drier air from the northwest by Saturday and Sunday.  As this flow firmly establishes itself, we'll see dew points plummet into the upper 20s and 30s.  Say goodbye to the summer Monsoon (third driest on record).  

The dry, northwest flow will keep newly-formed ozone moving to the southeast away from the forecast area.  It will also continue to evaporate any remaining moisture from soil, making the topsoil available for easy suspension in the atmosphere.  In addition, drier air means cooler overnight temperatures and increasing morning inversions.  Thus, any pollution that becomes suspended in the lower atmosphere will have a tougher time mixing vertically.  

So what does all this mean?  The northwest flow should keep local ozone concentrations in the "Good" range through the weekend and much of next week.  Increasingly drier soil and strengthening inversions could lead to PM-10 concentrations reaching the "Moderate" category sometime next week.  In the mean time, this weekend's weather and air quality will be favorable for outdoor activities.

Check back on Sunday for the latest on the coming work-week's forecasted conditions.  Until then, have a great weekend!

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

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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