[ADEQ Forecasts] ADEQ Daily Air Quality Forecast - Friday, May 18, 2012

[forecasts@lists.azdeq.gov]

Health message for Thursday May 17: Unusually sensitive people should consider reducing prolonged or heavy exertion outdoors.

Health message for Friday May 18: Unusually sensitive people should consider reducing prolonged or heavy exertion outdoors.

Synopsis and Discussion
OZONE:  At noon today local hourly ozone concentrations ranged from 37 parts per billion at the West Phoenix monitoring site to 56ppb at Humboldt Mountain.  These readings were 22 and nine ppb lower than the same time 24 hours ago.  Wednesday 8-hour average ozone concentrations dropped into the good range of the Air Quality Index at at least one monitoring site within the Valley - for the first time since Thursday May 10.  Since that date all ozone levels have been elevated to unhealthy over not only the Phoenix metro area but over much of Arizona as well with exceedances at Yuma, Grand Canyon, and near-exceedances at Flagstaff & Prescott.  Fortunately, a significant weather pattern change in the form of an upper level trough passage will bring an episode of gusty winds to the Valley and this should help produce one day of relatively low ozone levels.  Unfortunately, in its wake the wind-flow over and to the west of the metro area will again become conducive to another influx of additional ozone and/or its precursors as early as Friday afternoon.  This situation bears watching since historically this situation can result in rapid increases in ozone levels from one day to the next.    

PARTICLES:  On Friday the southern end of a vigorous but dry upper level trough in the mid-latitude storm track will bring an increase in gradient winds to the Valley by late morning.   It now appears that gusty winds may begin over the metro area as early as mid-morning and continue into the early evening hours.  In addition, low-level wind-flow will be capable of transporting dust from desert areas located to the southwest and west of the Valley.  Also, areas of local blowing dust are possible by Friday afternoon as wind gusts over 30 mph occur.  For these reasons highest PM-10 (coarse particle) concentration are forecast to reach the mid-moderate range of the Air Quality Index.


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:

Mark Shaffer, Communications Director
Arizona Department of Environmental Quality
Office of Communications
1110 W. Washington St., Phoenix, AZ 85007
(602) 771-2215
ms15@azdeq.gov