[ADEQ Forecasts] ADEQ Daily Air Quality Forecast For Friday November 21, 2008

[forecasts@lists.azdeq.gov]

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

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Health message for Thursday, November 20: Unusually sensitive people
should consider reducing prolonged or heavy exertion. 

Health message for Friday, November 21: Unusually sensitive people
should consider reducing prolonged or heavy exertion. 

Synopsis and Discussion

*A PM-10 HEALTH WATCH REMAINS IN EFFECT FOR THURSDAY, NOVEMBER 20, 2008*
   
Uncertainty in the models leaves the extended forecast up in the air.
It seems that the evening model run (00Z/5pm) wants to put a good chance
of rain in the forecast for Thanksgiving Day here in Phoenix.  The early
morning run (12Z/5am) takes it out with the anticipated trough of low
pressure cutting off and getting absorbed in the overall ridge of high
pressure.  Reality will likely be somewhere in the middle with a weaker
trough making it into Arizona by the middle to end of next week,
producing rain and snow in the higher elevations from Prescott to
Flagstaff and the Grand Canyon.  It's still a week a way, so anything
can happen between now and then.
 
Particulate-wise, we've had three PM-10 Health Watches in the past four
days, and concentrations are still holding in the mid "Moderate" range.
The outlook is not very good as far as forecasted ventilation goes.
Friday will barely reach the Fair category for ventilation.  Then it's
back to Marginal through much of next week.  It's a little surprising
with the lack of surface winds to mix the air with relatively strong
morning inversions that we haven't exceeded the health standard yet.
With Friday's ventilation looking a bit better and the weekend's lack of
commuter traffic looming, it may not happen until early next week.
Keeping a close eye on the situation, we'll ride this latest Health
Watch through Thursday with no further extension.  Check back Sunday for
a look at the coming weekend's weather and air quality.  Have a good
day!


If you have any questions or comments regarding this forecast please
contact:
The Arizona Department of Environmental Quality
Office of Communications
1110 W Washington St, Phoenix, AZ 85007
(602) 771-4583 
communications@azdeq.gov

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