[ADEQ Forecasts] ADEQ Daily Air Quality Forecast for Dec. 24, 2007

[forecasts@lists.azdeq.gov]

Health message for Monday, Dec 24: Unusually sensitive people should
consider reducing prolonged or heavy exertion.

Health message for Tuesday, Dec 25: Unusually sensitive people should
consider reducing prolonged or heavy exertion.

Synopsis and Discussion
A PM-2.5 HEALTH WATCH REMAINS IN EFFECT THRU MIDNIGHT TONIGHT
Sunday's increasingly stagnant weather conditions contributed to another
exceedance of the PM-2.5 (fine particle) standard, as did the suspected
smoke from the increased use of fireplaces during the nighttime hours.
Highest hourly PM-2.5 concentrations ranged from 61ug/m3 at the Durango
monitoring site to 68.8ug/m3 at Phoenix Supersite to 83.8ug/m3 at West
Phoenix.  All of these readings occurred between midnight and 4:00 a.m.
on the 23rd.  Another high PM-2.5 event is shaping up for today and
tonight; since average readings for the period between midnight and
10:00 a.m. were in the 35-40ug/m3 range at most sites. In addition,
morning local ACARS sounding data indicates that a strong (7-8 deg C)
surface-based radiation inversion formed overnight and that it reaches
beyond 2K'.  This will keep the best the mixing depth at or below 3K'
all day and result in POOR to MARGINAL dispersion going into the
potential peak late afternoon and evening PM-2.5 emission period. Thus,
the PM-2.5 Health Watch will remain in effect thru midnight.  High
PM-2.5 concentrations will likely carry over into Christmas Day;
however, a significant increase in northerly surface winds is on tap by
late morning due to the arrival and passage of a vigorous but dry upper
level trough and surface cold front. Cool and somewhat stagnant
conditions will   return on Wednesday ahead of another trough passage on
Thursday.  There is a slight chance for areas of blowing dust on
Tuesday, mainly over the west and northwest valley.  Otherwise, highest
particle pollutant levels should be near the mid-moderate range of the
Air Quality Index Tuesday and Wednesday.  -Reith

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

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