[ADEQ Forecasts] ADEQ Issues an Ozone Health Watch for the Phoenix Metro Area for Thursday, May 13, 2010

Wed May 12 12:20:41 MST 2010

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Health message for Wednesday, May 12: Unusually sensitive people should consider reducing prolonged or heavy exertion outdoors.   

Health message for Thursday, May 13: Unusually sensitive people should consider reducing prolonged or heavy exertion outdoors. 

Synopsis and Discussion
Unusual May weather continues with a broad but weak upper level trough lingering over AZ into the weekend.  However, low-level gradients will be quite weak and relatively light winds are forecast thru this forecast period.  Strong warming aloft and overnight inversion formation will likely contribute to elevated to high hourly PM-10 levels during the a.m. periods near the Salt River channel Thursday and Friday, but 24-hour average concentrations will remain well below critical levels. Another influx of CA ozone and its precursors evidently occurred on Tuesday.  Despite local wind gusts of 35 mph and afternoon high temperatures only in the 70's, maximum ozone concentrations were at the same level as two days ago when temperatures were in the middle 90's. (Flagstaff had the highest one-hour and eight-hour ozone concentrations in the entire state).  With mostly light winds, a warming trend back into the 90's, and not much in the way of cloud cover, ozone production and accumulation are expected to increase.  In addition, low-level winds will be conducive to more CA transport into this evening, and this may prime the Valley for higher concentrations on Thursday.  Thus, an Ozone Health Watch has been issued.   -Reith

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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