[ADEQ Forecasts] ADEQ AIR QUALITY FORECAST FOR THURSDAY, DECEMBER 4, 2008

[forecasts@lists.azdeq.gov]

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

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

Health message for Wednesday, December 3: Unusually sensitive people
should consider reducing prolonged or heavy exertion. 

Health message for Thursday, December 4: Unusually sensitive people
should consider reducing prolonged or heavy exertion. 

Synopsis and Discussion
  This is a very interesting time air quality-wise.  The Valley has seen
elevated PM-2.5 levels in each of the last 3 years around the 5th and
6th of December, exceeding on both days in 2007.  Interesting to note,
those were weekdays and not the weekend where we would normally expect
to see such readings due to increased fireplace activity.
Concentrations during each episode from 2005-2007 dropped off
considerably following the passage of storm systems.     
   Jumping ahead to 2008, we're beginning to see this same scenario
unfolding with the exception of one thing.  There's no storm system
anticipated in the next few days that could help alleviate some of this
PM-2.5 accumulation.  In fact, stagnant conditions are expected to
continue through early next week.  There is a developing area of low
pressure that will become cut off from the main flow and hang out off
the coast of southern California this coming weekend.  Hopefully by this
time next week another passing trough will absorb its energy, dragging
it through Arizona along with any moisture it may have.  Unfortunately,
that's a big assumption at this point.
   The newly activated South Phoenix PM-2.5 monitor had the highest
concentrations on Tuesday, with levels reaching 69 ("Moderate" range) on
the Air Quality Index (AQI).  With little movement in the lower-level
air the next several days and continued residential fireplace usage,
that number will only increase heading into the weekend.  Thus, a PM-2.5
Health Watch is likely by Friday.  You can help by voluntarily limiting
or altogether eliminating the use of fireplaces or outdoor fire pits
during this period.  Until tomorrow, have a good day!  -J.Paul  

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