AIR STAGNATION ADVISORY
Issue Date: 258 PM PST WED DEC 23 2009
Expiration: 1000 AM PST SAT DEC 26 2009

...AIR STAGNATION ADVISORY IN EFFECT FOR MOST OF THE INTERIOR
LOWLANDS OF WESTERN WASHINGTON FROM 4 AM THURSDAY TO 10 AM PST
SATURDAY...
THERE IS GOOD POTENTIAL FOR STAGNANT CONDITIONS TO DEVELOP
BEGINNING THURSDAY AND PERSISTING THROUGH AT LEAST SATURDAY
MORNING.
FORECAST GUIDANCE INDICATES STRONG HIGH PRESSURE ALOFT WILL BUILD
OVER THE REGION...TRAPPING COLD AIR NEAR THE SURFACE UNDER WARM
AIR ALOFT. THE RESULTING LOW LEVEL TEMPERATURE INVERSION ALONG
WITH LIGHT SURFACE WINDS WILL ALLOW POLLUTANTS LIKE WOOD SMOKE AND
VEHICLE AND INDUSTRIAL EMISSIONS TO ACCUMULATE...DEGRADING AIR
QUALITY OVER THE NEXT FEW DAYS.
WINDS WILL PREVENT STAGNATION ALONG THE COAST...THE STRAIT OF
JUAN DE FUCA AND ALSO ACROSS THE SAN JUAN ISLANDS. THE OLYMPICS
AND CASCADES WILL ALSO BE ABOVE THE STAGNANT INVERSION LAYER.
THEREFORE THESE AREAS ARE NOT INCLUDED IN THE ADVISORY.
GAP WINDS THROUGH THE CASCADE PASSES ARE EXPECTED TO DEVELOP FRIDAY.
THE WINDS ON FRIDAY COULD BE STRONG ENOUGH TO IMPROVE POLLUTION
LEVELS NEAR THE FOOTHILLS AND PORTIONS OF THE EAST PUGET SOUND
LOWLANDS. A PERIOD OF IMPROVED AIR QUALITY IS POSSIBLE IN THESE
AREAS. CONTINUE TO MONITOR THE LATEST FORECASTS.
CHECK WITH YOUR LOCAL AIR QUALITY AGENCY FOR POSSIBLE RESTRICTIONS
IN YOUR AREA.
$$
MERCER
WEATHER.GOV/SEATTLE