[ADEQ Forecasts] ADEQ AIR QUALITY FORECAST FOR WEDNESDAY, MARCH 25, 2009

[forecasts@lists.azdeq.gov]

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

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

Health message for Tuesday, March 24, 2009: Unusually Sensitive People
should consider limiting prolonged or heavy exertion outdoors.

Health message for Wednesday, March 25, 2009: Unusually Sensitive People
should consider limiting prolonged or heavy exertion outdoors. 
	
Synopsis and Discussion
   The forecast is calling for more winds on Thursday, similar yet
slightly lighter than they were this past Sunday.  There is a large
trough of low pressure currently located over the central U.S.  As it
rotates counter-clockwise, embedded disturbances continue to drop south
and then east, before finally being jettisoned to the northeast part of
the country.  The way the trough is positioned, Arizona is in the direct
path of the next disturbance slated to move through Thursday afternoon.
There will be no rain, so the threat of more blowing dust does exist.
One positive thing to note is the direction of the winds.  They will be
out of the northwest this time.  Northwest winds typically don't
generate as much dust as winds from the southwest (more vegetation to
the northwest).  Thus, we will see elevated PM-10 levels once again on
Thursday and early Friday, but we do not expect concentrations to exceed
health standards at this time.   
   Ozone and precursors continue to flow from west to east across
Arizona under this weather pattern.  It's possible to see a small spike
in Ozone here in the Phoenix forecast area on Wednesday ahead of the
winds, but again nothing too extraordinary.  High pressure returns late
Friday through the weekend.  This will allow for afternoon desert
temperatures to warm to the mid 80s by Sunday following the lower 70s on
Friday.  Check back tomorrow for the latest on the pending
Thursday/Friday dust event.  Until then, have a good day!  -J.Paul

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