[ADEQ Forecasts] ADEQ Issues Air Pollution Health Watch for Fri., Dec. 21

[forecasts@lists.azdeq.gov]

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

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

Synopsis and Discussion
A PM-10 HEALTH WATCH HAS BEEN ISSUED FOR FRIDAY DECEMBER 21
Data derived from a local ACARS sounding at 11:06 shows that the best
mixing depth today will be near 3900' and that dispersion will be POOR
to MARGINAL, depending on whether or not surface winds manage to
increase by late afternoon. Despite these atmospheric properties and
visibilities in the 7-9 mile range at several valley airfields this
a.m., hourly PM-2.5 (fine particle) concentrations at most monitoring
sites as of 10:00 a.m. are roughly half of what they were at the same
hour time Wednesday.  A significant weather change will occur on Friday
as the first in a series of cold but relatively dry upper level troughs
and surface cold fronts in the mid-latitude storm track arrives.
Tightening low-level pressure gradients and strong winds aloft behind
Friday's frontal passage are expected to coincide with clearing skies to
produce strong and gusty winds by the late afternoon that will be
capable of generating and transporting considerable amounts of blowing
dust from destabilized areas of soils; thus, a PM-10 Health Watch has
been issued as a precaution for those with heart or lung disease.  There
is the potential for winds to continue to be gusty and dust to remain
airborne right thru the nighttime hours into mid-morning on Saturday so
the Health Watch may have to be extended.  -Reith

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

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