[ADEQ Forecasts] ADEQ Issues a 2.5 Particulate Matter Health Watch for the Phoenix Metro Area for Friday, December 24, 2010

[forecasts@lists.azdeq.gov]

Health message for Wednesday December 22: No health impacts are
expected. 
Health message for Thursday December 23: Unusually sensitive people
should consider reducing prolonged or heavy exertion. 
Health message for Friday December 24: Unusually sensitive people should
consider reducing prolonged or heavy exertion. 


Synopsis and Discussion
A PM-2.5 HEALTH WATCH HAS BEEN ISSUED FOR FRIDAY DECEMBER 24
The welcome news is that the approach and arrival of an upper level
trough and surface cold front in the mid-latitude storm track will bring
periods of rain - heavy at times - to the Valley later today and
tonight.  This will contribute to very good air quality.  The unwelcome
news is that in its wake a strong and warm ridge aloft will approach the
Phoenix metro area by Thursday afternoon and continue to strengthen
overhead into the weekend.  As a result, the air mass over the Valley is
expected to become increasingly stagnant due to cold air at the surface,
warming aloft (10-15 deg F in the 5-10K' layer between Thursday evening
and Saturday morning), and overnight inversion formation due to clearing
skies and relatively light winds.  Forecast models are indicating a
local mixing height on Friday of only 3000' along with POOR dispersion
with similar conditions on Saturday.  Unfortunately, these atmospheric
conditions will develop at the same time that many Valley residents use
residential wood-burning fireplaces and appliances to celebrate holiday
events.  The widespread and persistent smoke (PM-2.5) thus generated has
produced unhealthy air quality in the metro area four of the last five
years during this period in December even under more favorable weather
patterns.  Therefore a PM-2.5 Health Watch has been issued for Friday
December 24 with a high possibility for a High Pollution Advisory on
Saturday December 25.  Persons with heart or lung disease can reduce
their exposure by remaining indoors.   -Reith 

NOTE: DUE TO THURSDAY'S STATE OF AZ EMPLOYEE FURLOUGH DAY, AN UPDATED
FORECAST WILL NOT BE AVAILABLE UNTIL FRIDAY MORNING DECEMBER 24.


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

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


If you have any questions or comments regarding this forecast please
contact:

Arizona Department of Environmental Quality
Office of Communications
1110 W. Washington St., Phoenix, AZ 85007
(602) 771-2215
ms15@azdeq.gov


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