[ADEQ Forecasts] ADEQ AIR QUALITY FORECAST FOR SATURDAY, DECEMBER 13, 2008

[forecasts@lists.azdeq.gov]

http://www.azdeq.gov/ensemble.pdf

For transportation alternatives:
http://www.valleymetro.org


Health message for Friday, December 12: Unusually sensitive people should consider reducing prolonged or heavy exertion. 

Health message for Saturday, December 13: Unusually sensitive people should consider reducing prolonged or heavy exertion. 

Synopsis and Discussion
    It's time to get those sweaters out.  A large trough of low pressure will dive south over the deserts of California and Arizona this weekend.  Tapping into subtropical moisture, clouds will be on the increase with a chance for rain starting Sunday morning and continuing through Wednesday.  About three to four pulses of energy will move through storm track, triggering the periods of rain.  It's possible that the Phoenix forecast area could pick up about a half an inch from Sunday to Wednesday with more possible by the following weekend.  
   The main story, however, will be the cold air crashing in from Canada.  We're looking at afternoon desert temperatures in the upper 50s Sunday through Thursday with lows in the upper 30s to around 40°F on Thursday when the clouds move out.  Snow is likely in the high country next week with Flagstaff possibly getting 6-10 inches, much more on the San Francisco Peaks (SnowBowl).
   Valley PM-10 levels may should be "Moderate" on Saturday as winds will be around 10 to 20 mph with occasional stronger gusts.  Once the moisture moves in, both PM-10 and PM-2.5 levels will drop off considerably.  Depending on the amount rain we get the next couple of weeks, PM-10 may be put on the shelf for a while.  Unfortunately PM-2.5 level will rebound much quicker as festive residential fireplace activity will continue through New Year's.  Check back Sunday for the latest.  Have a great weekend!  -J.Paul  

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