[ADEQ Forecasts] ADEQ AIR QUALITY FORECAST FOR FRIDAY, APRIL 17, 2009

[forecasts@lists.azdeq.gov]

http://www.azdeq.gov/ensemble.pdf

For transportation alternatives:
http://www.valleymetro.org

Health message for Thursday, April 16: Unusually sensitive people should
consider reducing prolonged or heavy outdoor exertion outdoors.  

Health message for Friday, April 17: Unusually sensitive people should
consider reducing prolonged or heavy outdoor exertion outdoors. 
 
Synopsis and Discussion
The large upper level trough that generated strong winds and blowing
dust over the local forecast area on Tuesday and Wednesday will linger
overhead the next few days before moving east on Saturday in response to
a strong ridge approaching from the west.  Strong warming aloft,
combined with overnight inversion formation and lighter winds, will
result in a rather stagnant air mass during the a.m. periods by
Saturday.  Even so, PM-10 levels will remain well below health watch
criteria thru this forecast period.  An impulse rotating
counterclockwise around a Utah upper level low is expected to bring an
increase in convective clouds over the higher terrain northwest thru
northeast of the metro area this afternoon.  Outflow winds from the
larger of these clouds may bring gusty winds and localized blowing dust
to parts of the Valley into the evening hours.  The same winds will be
capable of delivering additional ozone precursors, so a rather high AQI
value has been installed for that pollutant for Friday.  The axis of the
aforementioned ridge is advertised to be overhead by Sunday, at which
time local low-level winds will become increasingly easterly.  This
situation, in combination with sunny skies and afternoon temperatures in
the low to mid 90's, has the potential to boost both local ozone
production and accumulation - and yield high ozone concentrations early
next week.  -Reith   

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