HAZARDOUS WEATHER OUTLOOK
Issue Date: 658 AM PST MON DEC 21 2009
Expiration: 600 AM PST TUE DEC 22 2009
THIS HAZARDOUS WEATHER OUTLOOK IS FOR CENTRAL...NORTH CENTRAL AND
NORTHEAST OREGON AS WELL AS SOUTH CENTRAL AND SOUTHEAST WASHINGTON.
.DAY ONE...TODAY AND TONIGHT
IMMEDIATE CONCERNS THROUGH TONIGHT ARE FOG AND WINDS AND SOME SNOW
MAINLY TONIGHT IN THE MOUNTAINS. THESE CONCERNS ARE DISCUSSED BELOW
DENSE FOG
KITTITAS VALLEY, YAKIMA VALLEY, LOWER COLUMBIA BASIN OF
WASHINGTON, LOWER COLUMBIA BASIN OF OREGON
PRIOR TO A FRONTAL SYSTEM PASSAGE LATER TODAY...LOW CLOUDS WILL
CONTINUE TO KEEP AREAS OF DENSE FOG IN THE KITTITAS AND YAKIMA
VALLEYS AND IN THE LOWER COLUMBIA BASIN OF WASHINGTON AND OREGON
THROUGH THIS MORNING. AREAS OF DENSE FOG WITH VISIBILITIES AT ONE
QUARTER OF A MILE OR LESS WILL OCCUR THIS MORNING IN THESE AREAS. A
DENSE FOG ADVISORY IS IN EFFECT FOR THE AREAS LISTED ABOVE. PLEASE
REFER TO PRODUCT PDXNPWPDT FOR FURTHER DETAILS. AS THE FRONTAL
SYSTEM MOVES ACROSS THE AREA...WINDS WILL INCREASE FROM THE WEST
AND MIX OUT THE LOW LEVEL CLOUDS AND FOG.
CHINOOK DOWNSLOPE WINDS OUT OF THE SOUTH WILL CONTINUE TODAY ALONG
THE FOOTHILLS OF THE BLUE MOUNTAINS AND HAVE ALREADY SCOURED OUT THE
LOW CLOUDS AND FOG. THE IMPROVED VISIBILITY AND MID LEVEL CLOUD
BASES WILL CONTINUE ALONG THE BLUE MOUNTAIN FOOTHILLS UNTIL AROUND
NOON AND THEN LOWER AGAIN AS THE COLD FRONT APPROACHES. THE FRONT
WILL MOVE THROUGH THE FOOTHILLS BEGINNING AROUND 1-2 PM THIS
AFTERNOON AND THEN VEER TO THE WEST AND INCREASE BETWEEN 2-4 PM PST
THIS AFTERNOON.
STRONG WIND
GRANDE RONDE VALLEY
PRESSURE GRADIENTS WINDS HAVE INCREASED IN UNION AND BAKER COUNTIES
RESULTING IN VERY WINDY CONDITIONS IN THE SOUTHERN GRANDE RONDE
VALLEY. A WIND ADVISORY IS NOW IN EFFECT FOR THE GRANDE RONDE VALLEY
UNTIL 4 PM PST THIS AFTERNOON. FOR DETAILS SEE PRODUCT PDXNPWPDT.
SNOW
SOUTHERN BLUE MOUNTAINS OF OREGON
SNOW LEVELS THIS MORNING WILL BEGIN AROUND 4000-6000 FEET ALONG THE
EAST SLOPES OF THE CENTRAL AND SOUTHERN WASHINGTON CASCADES AND
AROUND 6000-7000 FEET IN THE NORTHERN AND CENTRAL OREGON CASCADES
AND IN THE BLUE MOUNTAINS. A FAIRLY FAST MOVING COLD FRONT AND
ATTENDANT PRECIPITATION WILL MOVE INTO THE FORECAST AREA TODAY FROM
THE WEST AND WILL CONTINUING MOVING ACROSS THE FORECAST AREA THROUGH
THIS EVENING. SNOW LEVELS WILL LOWER DRAMATICALLY THIS AFTERNOON AND
TONIGHT THUS ALLOW SNOW TO BEGIN ACCUMULATING THIS AFTERNOON THROUGH
THIS EVENING WITH EXPECTED TOTALS OF A FEW INCHES UP TO AROUND 5
INCHES...MAINLY ABOVE PASS LEVELS. HOWEVER...THE SOUTHERN BLUE
MOUNTAINS STAND TO GET 3 TO 5 INCHES OF NEW SNOW BY LATE THIS
EVENING. AS SUCH A WINTER WEATHER ADVISORY FOR SNOW IS IN EFFECT FOR
THE SOUTHERN BLUE MOUNTAINS FROM 4 PM THIS AFTERNOON UNTIL 4 AM PST
TUESDAY MORNING. FOR DETAILS SEE PRODUCT PDXWSWPDT (WMO HEADER WWUS
KPDT).
A FAST MOVING MID/UPPER LEVEL TROUGH MOVES ACROSS THE FORECAST AREA
TONIGHT AND EXITS INTO SOUTH CENTRAL AND SOUTHEAST OREGON SOON AFTER
DAYBREAK ON TUESDAY MORNING.
.DAYS TWO THROUGH SEVEN...TUESDAY THROUGH SUNDAY
THE PROBABILITY FOR WIDESPREAD HAZARDOUS WEATHER IS LOW.
HIGH PRESSURE WILL BUILD OVER THE FORECAST AREA TUESDAY AND
WEDNESDAY AND THEN PERSIST OVER THE PACIFIC NORTHWEST THROUGH THE
COMING WEEKEND FOR DRIER CONDITIONS.
.SPOTTER INFORMATION STATEMENT...
SPOTTER ACTIVATION MAY BE REQUIRED.
WEATHER SPOTTERS ARE ENCOURAGED TO REPORT SIGNIFICANT WEATHER
CONDITIONS ACCORDING TO STANDARD OPERATING PROCEDURES.
GRAPHICAL FORECASTS OF WEATHER HAZARDS OUT TO SEVEN DAYS
ARE DISPLAYED ON THE WORLD WIDE WEB AT:
WWW.WRH.NOAA.GOV/PDT/CURRENTHAZARDS/HWO.HTML
ALL LETTERS IN THE ABOVE URL ARE LOWER CASE...EXCEPT THE H IN
CURRENTHAZARDS.
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