[ADEQ Forecasts] ADEQ Daily Air Quality Forecast - Saturday, July 17, 2010

Fri Jul 16 12:29:17 MST 2010

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Health message for Friday, July 16: Unusually sensitive people should consider limiting prolonged or heavy exertion outdoors. 

Health message for Saturday, July 17: Unusually sensitive people should consider limiting prolonged or heavy exertion outdoors. 

Models are predicting a good chance for showers and thunderstorms in southeastern Arizona today and Saturday.  Tomorrow could be our best shot at seeing a stay storm cell roll into the Valley.  This could be very interesting as far as air quality goes.  Typically storms from southeast generate a lot of dust as opposed to the ones from the northeast which are more electrical in nature.  As they collapse, the massive amounts of energy crash to the ground and spread out like a glass of spilled milk.  Under this scenario, surface winds are capable of reaching or exceeding 60 mph at times.  The deserts have been pretty dry over the past couple of months, so there is plenty of dust ready to become airborne.  Will tonight be the first major dust storm of the Phoenix Monsoon season?  If so, expect local PM10 concentrations to soar into the MODERATE range.  If there is any rain to follow, concentrations would drop rapidly.  Because there is only a slight chance of such scenario impacting our area, we're keeping the forecasted maximum PM10 levels in the lower MODERATE range.

Let's talk Ozone.  Local winds have been fairly light for several days now.  Accumulated ozone and precursors have increased the potential for poor air quality here in the Phoenix forecast area.  A nice thunderstorm complex to the northeast Tuesday night contributed some precursors yesterday, but the early morning clouds inhibited ozone production just enough that maximum levels remained below the health standards, but just barely.  Cave Creek and North Phoenix saw the highest readings at 90 and 87 AQI, respectively.  The weather pattern the next couple of days should result in slightly lower concentrations.  A light west to east flow would put the highest levels in the eastern part of the Valley today through Sunday.  A switch to a more easterly flow could put the central and western part of the Valley at risk on Monday.  

Temperature-wise, we'll be cooling off a bit, to a mild 110°F by Sunday and Monday.  Unfortunately, the trade-off is due to increased moisture.  So, it will feel pretty much the same with heat indices reaching 112-115°F.  Air conditioning, a pitcher of ice water and maybe a dip in the swimming pool will help this weekend. 

Check back Sunday for a look at next week's weather and air quality.  Until then, have a great weekend!  -J.Paul

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


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