[ADEQ Forecasts] ADEQ Issues Air Pollution Health Watch for Fri., Dec. 7

[forecasts@lists.azdeq.gov]

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

Health message for Friday, Dec 07: Unusually sensitive people should
consider reducing prolonged or heavy exertion.

Synopsis and Discussion
A PM-10 HEALTH WATCH HAS BEEN ISSUED FOR FRIDAY DECEMBER 07
The air mass is still stagnant over the Valley this a.m. but much less
so than on Wednesday.  Local ACARS soundings indicate that the 5-6 deg C
surface-based radiation inversion that formed overnight reaches to
around 2500'.  Fortunately, the best mixing depth today has climbed from
4200' at 7:00 a.m. to 4700' at 11:00 and should continue to increase as
cooling aloft continues.  In addition, dispersion has improved into the
FAIR category with a southerly transport wind speed that is expected to
ultimately increase into the 15-20 mph range by late afternoon.
Although hourly PM-2.5 (fine particle) concentrations have again started
out quite high today, they should decrease significantly later on as
winds and mixing depths increase.  A strong upper level trough and
surface cold front are still on track to impact the local forecast area
on Friday.  It now appears that rainfall will not be as heavy or as
widespread as originally advertised, but it will be turning much cooler
over the next 48 hours.  Strong winds associated with the approach and
passage of the cold front by late Friday morning will likely be
sufficient to cause some blowing dust since the onset of precipitation
is now predicted to not occur until the afternoon hours.  For this
reason a PM-10 (coarse particle) Health Watch has been issued.
Thankfully, this weather change will usher in a new air mass and put an
end to the stagnant conditions experienced since Monday.  -Reith

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

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