[ADEQ Forecasts] ADEQ Daily Air Quality Forecast for Wednesday, July 29, 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 Tuesday, July 28: Unusually sensitive people should consider limiting prolonged or heavy exertion outdoors.

Health message for Wednesday, July 29: Unusually sensitive people should consider limiting prolonged or heavy exertion outdoors.


Synopsis and Discussion

High pressure remains fairly strong for this time of year, producing afternoon desert temperatures about 8-10 degrees above normal.  Yesterday's high in Phoenix was 114°F, with slightly warmer temps expected on Tuesday and Wednesday.  Unfortunately, the high pressure system has been out-muscled by a large trough of low pressure that has draped itself over much of the eastern U.S.  This trough has pushed our Monsoon high to the southwest of the region, a position not favorable for thunderstorm activity.  It's this drier air that is also partly responsible for the very hot weather.  By Friday, we could see our high regain some ground by moving over southern New Mexico.  This could shift the flow out of the southeast, resuming the import of more moist air from Old Mexico.  

Right now the Phoenix forecast area is enjoying some rather good air quality (only 5 local sites reached the lower "Moderate" range on Monday).  Looking upstream, however, concentrations in southern California have been climbing well above the ozone health standard.  A persistent west to east flow through Thursday could potentially import some of this ozone its precursors into our forecast area.  The abrupt shift from a westerly to southeasterly flow on Friday could lock the accumulating pollution in the Valley, resulting in much higher local concentrations on Friday and Saturday.  We'll be keeping a close eye on this throughout the week.  Lack of thunderstorm activity means PM-10 and PM-2.5 levels should remain in the "Good" range the next several days.
  
Check back tomorrow for more on this possible import scenario. Until then, have a good day!

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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