AIR STAGNATION ADVISORY
Warning Issue Date: 241 PM PST FRI DEC 25 2009
...AIR STAGNATION ADVISORY REMAINS IN EFFECT UNTIL 6 PM PST
SATURDAY FOR NORTHERN CLARK COUNTY AND COWLITZ VALLEY...
AN AIR STAGNATION ADVISORY REMAINS IN EFFECT UNTIL 6 PM PST
SATURDAY.
OFFSHORE FLOW OVER THE REGION WILL STRENGTHEN LATER TONIGHT AND
CONTINUE INTO THE SATURDAY. HOWEVER...STRONG LOW LEVEL INVERSIONS
WILL KEEP AREAS BELOW 1500 FEET FROM MIXING WELL. THIS WILL LEAD
TO AIR QUALITY THAT WILL GRADUALLY BECOME MORE POOR WITH TIME.
DEPENDING ON THE STRENGTH OF THE EAST WINDS...IT IS POSSIBLE THAT
CONDITIONS MAY BRIEFLY IMPROVE AT TIMES...BUT ONLY BRIEFLY.
EAST WINDS OVER SOUTHERN CLARK COUNTY WILL BE STRONG ENOUGH TO
KEEP AREAS MIXED...WITH NO SIGNIFICANT AIR QUALITY CHANGE.
* AREAS AFFECTED...ACROSS NORTHERN CLARK COUNTY...EXTENDING
NORTH THROUGH THE COWLITZ VALLEY.
* TIMING...NOW THROUGH SATURDAY.
* AIR QUALITY...EXPECT SLOWLY DEGRADING AIR QUALITY.
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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