AIR STAGNATION ADVISORY
Warning Issue Date: 1105 PM PST WED DEC 23 2009
...DENSE FOG ADVISORY IN EFFECT UNTIL 10 AM PST THURSDAY...
...AIR STAGNATION ADVISORY REMAINS IN EFFECT UNTIL 6 PM PST
SATURDAY...
THE NATIONAL WEATHER SERVICE IN PORTLAND HAS ISSUED A DENSE FOG
ADVISORY...WHICH IS IN EFFECT UNTIL 10 AM PST THURSDAY. AN AIR
STAGNATION ADVISORY REMAINS IN EFFECT UNTIL 6 PM PST SATURDAY.
* IMPACTS...DENSE FOG WILL INCREASE IN AREA OVERNIGHT.
VISIBILITIES ARE EXPECTED TO LOWER TO ONE QUARTER OF A MILE OR
LESS AT TIMES. FREEZING TEMPERATURES WILL ALLOW THE FOG TO FREEZE
TO SURFACES MAKING THEM SLIPPERY.
* TIMING...THROUGH 10 AM THURSDAY.
OFFSHORE FLOW OVER THE REGION WILL STRENGTHEN OVERNIGHT AND
CONTINUE FOR THE REST OF THE WEEK INTO THE COMING WEEKEND.
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.
* AREAS AFFECTED...THE WIND SHELTERED LOWLANDS OF THE CENTRAL
AND SOUTHERN WILLAMETTE 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.
A DENSE FOG ADVISORY MEANS VISIBILITIES WILL FREQUENTLY BE
REDUCED TO LESS THAN ONE QUARTER MILE. IF DRIVING...SLOW DOWN...
USE YOUR HEADLIGHTS...AND LEAVE PLENTY OF DISTANCE AHEAD OF YOU.
$$
DENSE FOG ADVISORY
Warning Issue Date: 1105 PM PST WED DEC 23 2009
...DENSE FOG ADVISORY IN EFFECT UNTIL 10 AM PST THURSDAY...
...AIR STAGNATION ADVISORY REMAINS IN EFFECT UNTIL 6 PM PST
SATURDAY...
THE NATIONAL WEATHER SERVICE IN PORTLAND HAS ISSUED A DENSE FOG
ADVISORY...WHICH IS IN EFFECT UNTIL 10 AM PST THURSDAY. AN AIR
STAGNATION ADVISORY REMAINS IN EFFECT UNTIL 6 PM PST SATURDAY.
* IMPACTS...DENSE FOG WILL INCREASE IN AREA OVERNIGHT.
VISIBILITIES ARE EXPECTED TO LOWER TO ONE QUARTER OF A MILE OR
LESS AT TIMES. FREEZING TEMPERATURES WILL ALLOW THE FOG TO FREEZE
TO SURFACES MAKING THEM SLIPPERY.
* TIMING...THROUGH 10 AM THURSDAY.
OFFSHORE FLOW OVER THE REGION WILL STRENGTHEN OVERNIGHT AND
CONTINUE FOR THE REST OF THE WEEK INTO THE COMING WEEKEND.
HOWEVER...STRONG LOW LEVEL INVERSIONS WILL KEEP AREAS BELOW
1500 FEET FROM MIXING WELL. THIS WILL LEAD TO AIR QUALITY THAT
WILL GRADUALLY BECOME MORE POOR WITH TIME.
* AREAS AFFECTED...THE WIND SHELTERED LOWLANDS OF THE CENTRAL
AND SOUTHERN WILLAMETTE VALLEY.
* TIMING...NOW THROUGH SATURDAY.
* AIR QUALITY...EXPECT SLOWLY DEGRADING AIR QUALITY.
PRECAUTIONARY/PREPAREDNESS ACTIONS...
AN AIR STAGNATION ADVISORY IS ISSUED WHEN LOCALLY ESTABLISHED
CRITICAL VALUES OF TRANSPORT WINDS...MIXING HEIGHT...AND
VENTILATION ARE EXPECTED TO PERSIST FOR AT LEAST 72 HOURS. THIS
PRODUCT WILL BE UPDATED AT LEAST EVERY 24 HOURS WHEN CONDITIONS
EXIST OR ARE EXPECTED TO CONTINUE.
A DENSE FOG ADVISORY MEANS VISIBILITIES WILL FREQUENTLY BE
REDUCED TO LESS THAN ONE QUARTER MILE. IF DRIVING...SLOW DOWN...
USE YOUR HEADLIGHTS...AND LEAVE PLENTY OF DISTANCE AHEAD OF YOU.
$$
|
