[ADEQ Forecasts] ADEQ Daily Air Quality Forecast for Thurs., Dec. 6

[forecasts@lists.azdeq.gov]

Health message for Wednesday, Dec 05: Unusually sensitive people should
consider reducing prolonged or heavy exertion.

Health message for Thursday, Dec 06: Unusually sensitive people should
consider reducing prolonged or heavy exertion.

Synopsis and Discussion
A PM-2.5 HEALTH WATCH REMAINS IN EFFECT THRU MIDNIGHT
Another stagnant day is underway over the local forecast area.  Morning
ACARS soundings indicate that the strong (8-9 deg C) surface-based
radiation inversion that formed overnight extends all the way to 5800';
however, the best Valley mixing depth is only 2400' and dispersion is
POOR with virtually no transport wind within the mixed layer.  On top of
that, filtered sunshine thru increasing high clouds will make vertical
mixing this afternoon even less efficient.  Hourly PM-2.5 (fine
particle) concentrations were high again this morning at some locations
such as the Durango site with 45.0ug/m3 at 9:00 a.m. and 57.9ug/m3 at
10:00 a.m. Eleven-hour averages from midnight thru 10:00 a.m. included
32.4ug/m3 at Durango and 30.0ug/m3 at West Phoenix; thus, the PM-2.5
Health Watch will remain in effect thru midnight as a precaution for
those with heart or lung disease.   Fortunately, the mid-latitude storm
track is poised to deliver another moisture-laden but colder Pacific
storm system to the state on Friday that will linger thru the weekend.
Although the air mass will still be rather stagnant on Thursday morning,
cooling aloft and increasing winds should result in improving dispersion
with time.  Strong and gusty winds associated with a cold frontal
passage are advertised for Friday and, except for perhaps a few areas of
blowing dust early, air quality will be vastly improved by then with
precipitation on the increase.  -Reith

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

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