Thu Oct 2 12:22:16 MST 2008


For transportation alternatives:

Health message for Thursday, October 2: Unusually sensitive people
should consider reducing prolonged or heavy exertion.

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

Synopsis and Discussion
   Winds have begun to shift as high pressure begins to weaken.  A large
trough of low pressure looming just off the coast will push towards
Arizona Friday.  Winds will increase out of the southwest on Friday to
around 10 to 20 mph.  Stronger winds are expected on Saturday as the
associated cold front pushes through the Phoenix forecast area.  This is
the first major weather event of the "winter" season as afternoon desert
temperatures will plummet into the mid to upper 80s by Sunday.  There is
an outside chance of a passing desert shower, but this system is not
going to be noted for its moisture.
   Air quality-wise, ozone concentrations have risen into the low to mid
"Moderate" range with the shift in winds enabling some southern
California transport.  With the winds strengthening on Friday, this
ozone should disperse pretty well.  On the flipside, Particulates should
climb well into the "Moderate" range.  It's possible that we could issue
at least a PM-10 Health Watch for Saturday due to a likely blowing dust
even.  As mentioned above, this system will have much colder air behind
it.  This means that the Valley's overnight temperatures will dip into
the upper 50s to low 60s.  Ladies and gentlemen, it's possible that we
could have an inversion marked by that ever familiar "brown cloud" on
Sunday and Monday.  With high pressure returning by the end of next
week, the brown cloud will be short-lived, if it happens at all.  It's
just a reminder of what can be expected this winter.  We'll have more
for you tomorrow.  So until then, have a good day!  -J.Paul

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