AIR STAGNATION ADVISORY
Warning Issue Date: 1000 AM PST SUN DEC 27 2009
...AIR STAGNATION ADVISORY NOW IN EFFECT UNTIL 10 AM PST SUNDAY
FOR THE CENTRAL AND SOUTHERN WILLAMETTE VALLEY...
THE AIR STAGNATION ADVISORY IS NOW IN EFFECT UNTIL 10 AM PST
SUNDAY.
* OFFSHORE FLOW OVER THE REGION WILL CONTINUE THROUGH THE WEEKEND
HOWEVER A STRONG LOW LEVEL INVERSION WILL MINIMIZE MIXING AT
LOWER ELEVATIONS.
* THE AREAS MOST IMPACTED WILL BE THE WIND SHELTERED LOWLANDS OF
THE CENTRAL AND SOUTHERN WILLAMETTE VALLEY BELOW 1500 FEET.
* AIR QUALITY IS EXPECTED TO SLOWLY DEGRADE THROUGH SUNDAY MORNING
THEN IMPROVE AS A WEAK FRONTAL SYSTEM LIFTING UP FROM THE SOUTH
IMPROVES MIXING ENOUGH TO BREAK THE INVERSION.
PRECAUTIONARY/PREPAREDNESS ACTIONS...
AN AIR STAGNATION ADVISORY IS ISSUED WHEN LOCALLY ESTABLISHED
CRITICAL VALUES OF TRANSPORT WINDS...MIXING HEIGHT...AND
VENTILATION ARE EXPECTED TO PERSIST FOR AT LEAST 72 HOURS. THIS
PRODUCT WILL BE UPDATED AT LEAST EVERY 24 HOURS WHEN CONDITIONS
EXIST OR ARE EXPECTED TO CONTINUE.
$$
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