[ADEQ Forecasts] ADEQ Daily Air Quality Forecast for Sat., Dec. 8

[forecasts@lists.azdeq.gov]

Health message for Saturday, Dec 8: Unusually sensitive people should
consider limiting prolonged exertion outdoors.

Health message for Sunday, Dec 9: Unusually sensitive people should
consider limiting prolonged exertion outdoors.

Synopsis and Discussion
*A PM-10 HEALTH WATCH REMAINS IN EFFECT FOR FRIDAY, DECEMBER 7, 2007*
Another trough of low pressure will make its way into the region late
Friday evening.  This one, however, will be much colder that the one
last week that brought the steady rain.  Coming from the northwest, this
system is currently just off the coast of San Francisco and will dive
southeast through southern California before settling over Arizona.
This also means that there won't be nearly as much moisture by the time
it reaches our region.  Some showers have already begun to develop in
northwestern Arizona around Kingman and as far south as north Maricopa
County.  Models suggest the biggest punch will be late Friday night into
early Saturday.  Some clearing will occur Saturday afternoon making way
for the possibility of afternoon thunderstorms with the slight surface
heating.  This low pressure will be slow leaving with moisture
re-circulating over the region through Tuesday afternoon.  When all is
said and done, many locations in the Phoenix forecast area could see up
to an inch or more of rain.  Again, we will likely finish the calendar
year below normal for precipitation, but it's a nice way to finish.
Winds are not anticipated to be too strong, so blowing dust will not be
an issue this weekend.  As mentioned, this is a cold system, so
afternoon desert temperatures will struggle to reach the low 60s through
Wednesday, warming only slightly Thursday and Friday of next week.
Mixing heights will gradually drop Saturday trough the middle of next
week.  As opposed to what happened this week, stagnation will not become
a concern until Thursday and Friday as the system exits.  That's when
PM-2.5 level will likely spike again.  Until then, we should have a few
days of relatively good air quality.  Check back Sunday for the latest.
Have a great weekend!  
-J.Paul 

For more information, please visit our Web page:
http://www.azdeq.gov/environ/air/ozone/ensemble.pdf

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