[ADEQ Forecasts] ADEQ Daily Air Quality Forecast - Saturday, August 13, 2011

[forecasts@lists.azdeq.gov]

Health message for Friday, August 12: Unusually sensitive people should
consider limiting prolonged exertion outdoors.

Health message for Saturday, August 13: Unusually sensitive people
should consider limiting prolonged exertion outdoors.


Synopsis and Discussion: 
Pleasant weather will continue into next week with afternoon
temperatures at or even slightly below normal for this time of year.
Rain amounts have not been where we would like them to be so far this
season, but the Valley will continue to see a 10 to 30% chance for
storms through the middle of next week.  Saturday has the best
opportunity for rain in the Valley before chances drop off until the
latter half of next week.  This also means that we will continue to see
a threat of blowing dust from distant storms to the south and east of
the forecast area.  Thus, PM10 levels are forecasted to remain in the
MODERATE range of the air quality index (AQI) through at least Monday.  
Ozone continues to defy what models suggest concentrations will be, with
all monitors holding in the GOOD range again on Thursday.  The Queen
Valley monitor had reported anomalously higher levels earlier this week
and was taken down for a calibration check yesterday.  The weather
pattern in Phoenix is expected to experience a shift from a
southwesterly flow to a southeasterly flow on Saturday as high pressure
moves north over Texas.  This could confine the invisible ozone plume to
the central and northern part of the Phoenix forecast area on Saturday.
That shift, however will be short-lived with the high pressure system
being forced south once again Sunday through much of next week.  This
will decrease thunderstorm activity as drier air is pulled in from the
southwest.  Ozone levels should improve as the precursors disperse to
the northeast each day Sunday through next Tuesday.
    
Check back on Sunday for a closer look at next week's weather and air
quality.  Until then, have a great weekend!  - J.Paul


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

For transportation alternatives:
www.valleymetro.org


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