DENSE FOG ADVISORY
Issue Date: 503 PM PST THU DEC 24 2009
Expiration: 1000 AM PST FRI DEC 25 2009

...AIR STAGNATION ADVISORY REMAINS IN EFFECT UNTIL 4 PM PST
SATURDAY...
...DENSE FOG ADVISORY IN EFFECT UNTIL 10 AM PST FRIDAY...
THE NATIONAL WEATHER SERVICE IN MEDFORD HAS ISSUED A DENSE FOG
ADVISORY...WHICH IS IN EFFECT UNTIL 10 AM PST FRIDAY. AN AIR
STAGNATION ADVISORY REMAINS IN EFFECT UNTIL 4 PM PST SATURDAY.
* STRENGTHENING HIGH PRESSURE OVER THE REGION HAS DEVELOPED AN
INVERSION OVER THE VALLEYS OF SOUTHERN OREGON.
* THIS INVERSION WILL STRENGTHEN TONIGHT AND PERSIST THROUGH
SATURDAY.
* COLD AND STABLE AIR WILL REMAIN TRAPPED IN THE VALLEYS.
THEREFORE TEMPERATURES WILL BE WARMER IN THE MOUNTAINS THAN IN
THE VALLEYS THROUGH SATURDAY.
* POLLUTANTS SUCH AS SMOKE AND OTHER AIRBORNE PARTICULATES WILL
BECOME TRAPPED IN THE VALLEYS AND...AT TIMES...AT MID
ELEVATIONS. THIS WILL CREATE THE POTENTIAL FOR DIMINISHING AIR
QUALITY.
* LOCALLY VERY DENSE FREEZING FOG WILL FORM IN MANY VALLEYS SUCH
AS THE ROGUE...UMPQUA...AND ILLINOIS VALLEYS. THIS WILL CREATE
VERY POOR VISIBILITIES AND THE POTENTIAL FOR SLIPPERY ROADWAYS
DUE TO FROST FORMATION.
PRECAUTIONARY/PREPAREDNESS ACTIONS...
AN AIR STAGNATION ADVISORY INDICATES THAT DUE TO LIMITED MOVEMENT
OF AN AIRMASS ACROSS THE ADVISORY AREA...POLLUTION WILL INCREASE.
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.
$$

AIR STAGNATION ADVISORY
Issue Date: 234 PM PST WED DEC 23 2009
Expiration: 400 PM PST SAT DEC 26 2009

...AIR STAGNATION ADVISORY IN EFFECT UNTIL 4 PM PST SATURDAY...
THE NATIONAL WEATHER SERVICE IN MEDFORD HAS ISSUED AN AIR
STAGNATION ADVISORY...WHICH IS IN EFFECT UNTIL 4 PM PST SATURDAY.
* STRENGTHENING HIGH PRESSURE OVER THE REGION HAS DEVELOPED AN
INVERSION OVER THE VALLEYS OF SOUTHERN OREGON.
* THIS INVERSION WILL STRENGTHEN TONIGHT AND IS LIKELY TO PERSIST
THROUGH AT LEAST SATURDAY.
* COLD AND STABLE AIR WILL REMAIN TRAPPED IN THE VALLEYS.
THEREFORE TEMPERATURES WILL BE WARMER IN THE MOUNTAINS THAN IN
THE VALLEYS THROUGH SATURDAY.
* POLLUTANTS SUCH AS SMOKE AND OTHER AIRBORNE PARTICULATES WILL
BECOME TRAPPED IN THE VALLEYS AND...AT TIMES...AT MID
ELEVATIONS. THIS WILL CREATE THE POTENTIAL FOR DIMINISHING AIR
QUALITY.
* LOCALLY DENSE FREEZING FOG WILL FORM IN MANY VALLEYS SUCH AS THE
ROGUE...UMPQUA...AND ILLINOIS VALLEYS. THIS WILL CREATE THE
POTENTIAL FOR SLIPPERY ROADWAYS DUE TO FROST FORMATION.
PRECAUTIONARY/PREPAREDNESS ACTIONS...
AN AIR STAGNATION ADVISORY INDICATES THAT DUE TO LIMITED MOVEMENT
OF AN AIRMASS ACROSS THE ADVISORY AREA...POLLUTION WILL INCREASE.
$$