[ADEQ Forecasts] ADEQ Daily Air Quality Forecast for Thurs., Dec. 20

[forecasts@lists.azdeq.gov]

Health message for Wednesday, Dec 19: Unusually sensitive people should
consider reducing prolonged or heavy exertion.

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

Synopsis and Discussion
A weak upper level trough passage was in progress Wednesday morning;
unfortunately all of the precipitation and most of the cloud cover will
stay north of the local forecast area.  However, increased winds and
cooling aloft have taken the edge off what otherwise would have been a
highly stagnant day.  Two local ACARS soundings - one at 6:00 a.m. and
the other at 10:00 a.m. - reveal that the best Valley mixing depth rose
from only 1700' during the earlier sounding to 3500' during the later
sounding.  Temperatures at the 5K' level cooled 2-3 deg F during that
period and dispersion improved from POOR to FAIR.  In this system's wake
some warming aloft is forecast to occur on Thursday which is apt to be
the most stagnant day of the week, especially with increasing cloud
cover by afternoon.  However, a turn to cooler and windy weather is on
tap for Friday as a strong but rather dry upper trough and surface cold
front sweep thru the area.  There is the potential for destabilized
areas of soil to yield significant amounts of blowing dust, especially
over the west and northwest Valley by late morning; some transport of
suspended dust is also possible. Depending on how the situation unfolds,
a PM-10 Health Watch may be issued for Friday.  -Reith

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

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