[ADEQ Forecasts] ADEQ Extends Air Pollution Health Watch through Fri., Sept. 5

[forecasts@lists.azdeq.gov]

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

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

Health message for Thursday, September 4:  Unusually Sensitive People
should consider limiting prolonged exertion outdoors.
 
Health message for Friday, September 5:  Unusually Sensitive People
should consider limiting prolonged exertion outdoors.
 
Synopsis and Discussion
*An Ozone Health Watch remains in effect for Thursday, September 4,
2008, and has been EXTENDED through Friday, September 5, 2008*
   Thanks to that dry westerly flow, the mornings are not nearly as
muggy as they have been this monsoon season.  Continued drying is
expected through the weekend with dewpoints possibly dipping into the
upper 30s by Saturday afternoon.  Models are suggesting that moisture
may return by the middle of next week as another trough of low pressure
dips south into southern California, drawing the moisture up from
Mexico.  We'll see if this holds up.  In the mean time, afternoon desert
temperatures are expected to reach 107 through Sunday under mostly sunny
skies and relatively light winds.
   As discussed in previous forecasts, Ozone concentrations have in fact
risen across the Phoenix forecast area due to that westerly flow.
Models suggest we could see unhealthy levels on Friday, but these same
models have been overestimating for several weeks now.  There's no doubt
that concentrations will approach the health standard (likely in the far
eastern part of the Valley), but it's hard to buy into the inconsistent
forecast model.  The best thing to do for now it is to extend the Ozone
Health Watch one more day and re-evaluate the situation on Friday.  You
may have noticed that Particulate rose into the "Moderate" range on
Wednesday as well.  Don't read too much into that as it was a one-hour
reading of over 600 micrograms at West 43rd that skewed the 24-hr
average.  Was it local burning or someone driving fast on a nearby
unpaved surface?  It's hard to say.  As of now, it is a valid reading
with nothing to suggest otherwise.  Take it out, and West 43rd is well
in the "Good" range with the rest of the local monitors.  Thus, we will
keep the forecast Particulate levels in the mid part of that category.
Check back tomorrow for a look at your weekend's weather and air
quality.  Have a good day!  -J.Paul

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