[ADEQ Forecasts] ADEQ Daily Air Quality Forecast For Saturday, July 25, 2009

[forecasts@lists.azdeq.gov]

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

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http://www.valleymetro.org


Health message for Friday, July 24: Unusually sensitive people should consider limiting prolonged or heavy exertion outdoors.

Health message for Saturday, July 25: Unusually sensitive people should consider limiting prolonged or heavy exertion outdoors.


Synopsis and Discussion

*OZONE HEALTH WATCH REMAINS IN EFFECT FOR FRIDAY, JULY 24, 2009*

A pretty solid layer of clouds currently covers much of Maricopa and Pinal Counties Friday morning.  These clouds are related to an upper-level disturbance rotating northwest around the Four Corners high.  This disturbance should continue to move northwest, allowing the clouds to decrease by late this afternoon.  Though it may be too late to allow enough surface-heating to spawn thunderstorms for our forecast area, there is still a chance that some outflow dust from storms in Pinal County later this evening.

The current cloud cover will keep Friday's ozone production across the forecast area well below its potential for this time of year.  Lingering precursors could lead to elevated concentrations this weekend if the Four Corner's high remains in place.  However, models suggest that it won't.  It seems there's always at least one weather feature in Canada prevent the ridge of high pressure from setting up camp for longer than a day or two near the Four Corners region.  This positioning is key to a good Monsoon season in terms of rain.  The latest menacing feature is a large trough of low pressure north of the Great Lakes.  This trough is expected to suppress our high to the southwest this weekend, resulting in a somewhat drier west and northwesterly flow over Arizona.  On a positive note, it will push the Valley's ozone plume to the far east and southeast, dispersing it over a fairly broad area.  Maximum concentrations will likely be around Fountain Hills, Apache Junction and Queen Valley this weekend, with values no higher than the mid "Moderate" range.  Decreased moisture means decreased thunderstorm activity, and thus a much very low chance for blowing dust on Sunday and Monday.  

Check back on Sunday for all the latest information on the weather and resulting air quality.  Until then, have a great weekend!

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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