Heavy Snow in Oregon, January 22 to 23, 2010

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE PENDLETON OR
230 PM PST FRI JAN 22 2010

.SHORT TERM...TONIGHT THROUGH MONDAY. THE PACIFIC NW IS UNDER A
LARGE AND COMPLEX TROUGH PATTERN WITH NUMEROUS EMBEDDED WAVES
THROUGHOUT WASHINGTON AND OREGON. A WEAK DEFORMATION BAND HAS ALSO
SET UP OVER THE NORTHERN HALF OF OREGON...AND DOPPLER RADAR SHOWS A
BAND OF LOW LEVEL CLOUDS AND LIGHT PRECIPITATION EXTENDING FROM
NORTH CENTRAL OREGON ACROSS NORTHERN WHEELER AND NORTHERN GRANT
COUNTIES.  A WINTER WEATHER ADVISORY IS CURRENTLY IN EFFECT FOR THE
OCHOCO-JOHN DAY HIGHLANDS.  SPOTTER REPORTS AND WEB CAMS SEEM TO
SHOW VERY LIGHT ACCUMULATIONS THUS FAR.  WILL KEEP THE ADVISORY IN
THIS ZONE BUT LOWER SNOW AMOUNTS IN THE FORECAST.  WINTER WEATHER
ADVISORIES FOR SNOW WILL REMAIN FOR THE BLUE MOUNTAINS AND WALLOWA
COUNTY.  WRAP-AROUND MOISTURE ASSOCIATED WITH A LOW OVER IDAHO AND
THE DEFORMATION BAND LIFTING NORTH SHOULD HELP ENHANCE SNOW.  ON
SATURDAY...THE BLUES WILL BE UNDER A NW FLOW ALOFT WITH OROGRAPHIC
SHOWERS CONTINUING.  PRECIPITATION WILL TAPER OFF FROM THE WEST
SATURDAY AND SATURDAY NIGHT AS A SHORTWAVE RIDGE MOVES EAST OF THE
CASCADES.

THE NEXT PACIFIC SYSTEM WILL BRING ANOTHER ROUND OF PRECIPITATION IN
OUR FAR WESTERN ZONES SUNDAY AFTERNOON THEN OVER THE REMAINDER OF
THE AREA SUNDAY NIGHT AND MONDAY.  THE AREA OF MOST CONCERN FOR
SIGNIFICANT SNOW WILL BE ALONG THE EAST SLOPES OF THE WA CASCADES AS
WELL AS THE KITTITAS AND YAKIMA VALLEYS.  ON SUNDAY NIGHT...THERE
WILL BE DECENT LOW LEVEL UPSLOPE AND A MOIST SW FLOW ALOFT AND
BELIEVE AMOUNTS COULD REACH ADVISORY CRITERIA ALONG THE CASCADE EAST
SLOPES.  CONFIDENCE IS HIGH THAT THE COLUMBIA BASIN EAST OF YAKIMA
AND ARLINGTON WILL SEE RAIN OR RAIN/SNOW SUNDAY NIGHT AND MONDAY
WHILE MOST OF THE AREA WILL SEE SNOW.  JOHNSON

.LONG TERM...MONDAY NIGHT THROUGH FRIDAY...THE SYSTEM THAT MOVES
INTO THE REGION MONDAY LOOKS TO SPLIT MONDAY NIGHT...WITH SOME
ONSHORE FLOW BEHIND THE SYSTEM TUESDAY AND TUESDAY NIGHT. AS A
RESULT...EXPECT SOME SHOWERS TO LINGER ACROSS THE REGION MONDAY
NIGHT THROUGH TUESDAY NIGHT. A WEAK UPPER RIDGE WILL MOVE OVER THE
AREA WEDNESDAY AND WEDNESDAY NIGHT FOR MOSTLY DRY CONDITIONS...
THOUGH MAY HAVE A FEW LINGERING SHOWERS OVER THE EASTERN MOUNTAIN
ZONES. THERE STILL IS SOME DIVERGENCE BETWEEN MID RANGE MODELS ABOUT
THE SYSTEM EXPECTED TO REACH THE COAST THURSDAY AND FRIDAY. SOME
SOLUTIONS SHOW THIS SYSTEM SPLITTING WHILE OTHERS KEEP IT
CONSOLIDATED AND MORE PROGRESSIVE. FOR NOW WILL CONTINUE CURRENT
FORECAST THAT LEANS TOWARDS THE PROGRESSIVE SOLUTIONS DUE TO THE
UNCERTAINTY. 90

&&

.AVIATION...PREVIOUS DISCUSSION...18Z TAFS...A WEATHER SYSTEM WILL
MOVE ACROSS THE REGION DURING THE NEXT 24 HOURS. THE AFFECTS OF THIS
SYSTEM ARE CURRENTLY BEING FELT AT KRDM WHERE SNOW OR A MIX OF SNOW
AND RAIN WILL KEEP CONDITIONS GENERALLY IFR OR LOWER THROUGH 22/23
UTC. CONDITIONS AT KRDM SHOULD IMPROVE THIS EVENING AS THE PRECIP
ENDS. MVFR CIGS CAN BE EXPECTED AT TIMES TODAY AT KPDT AND KALW DUE
WEST SURFACE FLOW. AS THE PRECIP WITH THE SYSTEM MOVES OVER KPDT AND
KALW THIS EVENING EXPECT AT LEAST MVFR CONDITIONS. ELSEWHERE EXPECT
MOSTLY VFR CONDITIONS THOUGH SOME MVFR CIGS MAY DEVELOP OVER KPSC
LATE IN THE PERIOD. 90

&&

.PRELIMINARY POINT TEMPS/POPS...
PDT  34  46  31  45 /  60  50  10  10
ALW  36  46  34  45 /  50  60  10  10
PSC  33  49  29  45 /  20  10  10  10
YKM  29  43  26  40 /  20  10  10  10
HRI  32  48  29  45 /  40  20  10  10
ELN  30  43  26  39 /  10  10  10  10
RDM  25  43  22  40 /  50  10  10  30
LGD  31  40  28  39 /  80  60  20  10
GCD  29  40  21  39 /  80  20  20  10
DLS  35  46  31  41 /  40  10  10  30

&&

.PDT WATCHES/WARNINGS/ADVISORIES...
OR...WINTER WEATHER ADVISORY UNTIL 4 AM PST SATURDAY FOR ORZ506.

     WINTER WEATHER ADVISORY UNTIL 4 PM PST SATURDAY FOR ORZ050-502.

     WINTER WEATHER ADVISORY UNTIL 10 AM PST SATURDAY FOR ORZ503.

WA...WINTER WEATHER ADVISORY UNTIL 4 PM PST SATURDAY FOR WAZ030.

&&

THREAT INDEX
SATURDAY : YELLOW
SUNDAY : YELLOW
MONDAY : GREEN

GREEN: NONE OR LIMITED NEED FOR WATCHES, WARNINGS, OR ADVISORIES.
YELLOW: A FEW WATCHES, WARNINGS, OR ADVISORIES POSSIBLE OR IN EFFECT.
RED: NUMEROUS WATCHES, WARNINGS, OR ADVISORIES POSSIBLE OR IN EFFECT.

FOR ADDITIONAL WEATHER INFORMATION, CHECK OUR WEB SITE AT...
WWW.WEATHER.GOV/PENDLETON

85/90/90

HAZARDOUS WEATHER OUTLOOK...UPDATED
NATIONAL WEATHER SERVICE PENDLETON OR
235 PM PST FRI JAN 22 2010

UPDATED FOR SNOW INFORMATION ON SUNDAY

ORZ041>044-049-050-501>506-WAZ024-026>030-501-502-231415-
EASTERN COLUMBIA RIVER GORGE OF OREGON-NORTH CENTRAL OREGON-
CENTRAL OREGON-LOWER COLUMBIA BASIN OF OREGON-GRANDE RONDE VALLEY-
WALLOWA COUNTY-FOOTHILLS OF THE BLUE MOUNTAINS OF OREGON-
NORTHERN BLUE MOUNTAINS OF OREGON-
SOUTHERN BLUE MOUNTAINS OF OREGON-
NORTHERN WHEELER AND SOUTHERN GILLIAM COUNTIES-JOHN DAY BASIN-
OCHOCO-JOHN DAY HIGHLANDS-
EASTERN COLUMBIA RIVER GORGE OF WASHINGTON-KITTITAS VALLEY-
YAKIMA VALLEY-LOWER COLUMBIA BASIN OF WASHINGTON-
FOOTHILLS OF THE BLUE MOUNTAINS OF WASHINGTON-
NORTHWEST BLUE MOUNTAINS OF WASHINGTON-
EAST SLOPES OF THE CENTRAL CASCADES OF WASHINGTON-
EAST SLOPES OF THE SOUTHERN CASCADES OF WASHINGTON-
235 PM PST FRI JAN 22 2010

THIS HAZARDOUS WEATHER OUTLOOK IS FOR CENTRAL AND NORTHEAST OREGON
AS WELL AS SOUTH CENTRAL AND SOUTHEAST WASHINGTON.

.DAY ONE...REST OF TODAY AND TONIGHT

SNOW
     NORTHWEST BLUE MOUNTAINS OF WASHINGTON, GRANDE RONDE VALLEY,
     WALLOWA COUNTY, NORTHERN BLUE MOUNTAINS OF OREGON, SOUTHERN
     BLUE MOUNTAINS OF OREGON, OCHOCO-JOHN DAY HIGHLANDS

AN AREA OF LOW PRESSURE WILL MOVE FROM SOUTHEAST OREGON ACROSS IDAHO
THROUGH SATURDAY BRINGING SNOW TO EASTERN OREGON AND EXTREME
SOUTHEAST WASHINGTON. THE HEAVIEST SNOW WILL BE ABOVE 4000 FEET.
NUMEROUS WINTER WEATHER ADVISORIES ARE IN EFFECT. PLEASE REFER TO
THE LATEST PDXWSWPDT PRODUCT FOR MORE DETAILS.

.DAYS TWO THROUGH SEVEN...SATURDAY THROUGH THURSDAY

SNOW SATURDAY
     NORTHWEST BLUE MOUNTAINS OF WASHINGTON, GRANDE RONDE VALLEY,
     WALLOWA COUNTY, NORTHERN BLUE MOUNTAINS OF OREGON, SOUTHERN
     BLUE MOUNTAINS OF OREGON

SNOW SUNDAY
     EAST SLOPES OF THE CENTRAL CASCADES OF WASHINGTON, EAST SLOPES
     OF THE SOUTHERN CASCADES OF WASHINGTON, KITTITAS VALLEY,
     YAKIMA VALLEY

SNOW WILL CONTINUE INTO SATURDAY ENDING FROM SOUTH TO NORTH.
HEAVIEST SNOW WILL BE IN THE NORTHERN BLUE MOUNTAINS.

ANOTHER STORM SYSTEM WILL IMPACT THE AREA LATE SUNDAY INTO MONDAY
BRINGING RAIN IN THE LOWER COLUMBIA BASIN AND BLUE MOUNTAIN
FOOTHILLS AND SNOW OR A RAIN/SNOW MIX ELSEWHERE.  SEVERAL INCHES OF
SNOW ARE POSSIBLE SUNDAY NIGHT ALONG THE EAST SLOPES OF THE CENTRAL
AND SOUTHERN WASHINGTON CASCADES AND THE KITTITAS AND YAKIMA
VALLEYS.

.SPOTTER INFORMATION STATEMENT...

SPOTTER ACTIVATION IS LIKELY THROUGH SATURDAY OVER EASTERN OREGON
AND EXTREME SOUTHEAST WASHINGTON.

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.