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.
$$