Blizzard and Heavy Snow in Oregon, November 30, 2010

AREA FORECAST DISCUSSION...UPDATED
NATIONAL WEATHER SERVICE PENDLETON OR
337 AM PST TUE NOV 30 2010

UPDATED AVIATION DISCUSSION

.SHORT TERM...TODAY THROUGH WEDNESDAY NIGHT. COMPLEX WEATHER
SCENARIO SHAPING UP TODAY WITH A MIXTURE OF RAIN...FREEZING
RAIN...SNOW...AND BLOWING SNOW/WIND ACROSS THE ENTIRE AREA. MULTIPLE
WINTER WEATHER WARNINGS/ADVISORIES REMAIN PLACE THROUGH TOMORROW.

AN INTENSE STORM SYSTEM IS STRIKING THE WA/OR CASCADES THIS MORNING
AND ITS MOISTURE WILL MOVE INTO THE REGION TODAY. -SN HAD ALREADY
DEVELOPED OVER ELN/YKM ALONG WITH RDM BUT THE TEMPS IN CENTRAL
OREGON HAD JUST BEGUN TO CLIMB. THE INTRUSION AND TIMING OF THIS
LOW LAYER WARM AIR FROM CENTRAL OREGON WILL BE THE CHALLENGE THIS
MORNING AS IT WORKS IT WAY INTO THE COLUMBIA BASIN.

WINTER WEATHER ADVISORIES REMAIN IN PLACE ACROSS THE EAST SLOPES OF
THE OREGON CASCADES WHERE THEY CAN SEE A MIX OF RAIN/SNOW THAT WILL
HINDER SNOW ACCUMULATION. HOWEVER ALONG THE EAST SLOPES OF THE WA
CASCADES IT SHOULD BE ALL SNOW WITH UPWARDS TO FOOT ACCUMULATION IS
EXPECTED BY WEDNESDAY MORNING. IN ADDITION TO THE WINTER STORM
WARNING ALONG THE EAST SLOPES OF THE WA CASCADES...THE KITTITAS
VALLEY IS ALSO UNDER A WARNING WITH 3-6 INCHES EXPECTED AND IN THE
WINTER WEATHER ADVISORY AREA OF THE YAKIMA VALLEY 2-4 INCHES OF SNOW
IS EXPECTED.

THE FAVORED GFS MODEL INDICATED THAT TEMPS AT 850MBS WILL CLIMB
ABOVE FREEZING BY 18Z ACROSS THE GORGE/BLUE MOUNTAIN
FOOTHILLS...WHEN THE WINTER WX ADVISORY EXPIRES...AND REMAINS AROUND
THE FREEZING MARK ACROSS THE LOWER COLUMBIA BASIN BY THIS SAME TIME.
THEREFORE SNOW AMOUNTS WERE KEPT SLIGHTLY HIER ACROSS THE PSC AREA.
FOR TONIGHT TEMPS COOL AND THE PCPN SHUD RETURN TO MOSTLY SNOW
BEFORE DECREASING LATER TONIGHT.

OTHERWISE SNOW WILL DEVELOP ACROSS THE BLUE/WALLOWA/OCHOCOS
MOUNTAINS THIS MORNING WHERE A WINTER STORM WARNING IS IN PLACE
INTO WEDNESDAY WITH UPWARDS TO A FOOT OF SNOW IS EXPECTED. IN
ADDITION...WINDY SOUTH WINDS ACROSS THE GRANDE RONDE VALLEY WILL
CREATE HAZARDOUS DRIVING CONDITIONS AND LOW VSBY SO A BLIZZARD
WARNING IS IN EFFECT ACROSS THIS AREA.

THE STORM SYSTEM SLOWLY DRIFTS EAST WEDNESDAY WITH DRIER CONDITIONS
MOVG INTO THE AREA FROM THE WEST. HOWEVER...ANOTHER STORM SYSTEM
WILL TAKE AIM ON OUR AREA WEDNESDAY NIGHT. MOISTURE FROM THE PACIFIC
WILL INCREASE ACROSS THE AREA AND ANOTHER ROUND OF SNOW MAY BE
EXPECTED FOR THE AREA.

.LONG TERM...THURSDAY THROUGH TUESDAY...WET UNSETTLED CONDITIONS
WILL CONTINUE THROUGH THE END OF THE WEEK. AS A WARM FRONT MOVES
SLOWLY INTO THE AREA ON THURSDAY AND FRIDAY...RAIN AND SNOW CHANCES
WILL INCREASE FROM SOUTHWEST TO NORTHEAST. THE MAIN FORECAST PROBLEM
RIGHT NOW CONCERNS TEMPERATURE PROFILES AND THE THREAT FOR FREEZING
RAIN ON THURSDAY. COLD SURFACE AIR WILL REMAIN IN PLACE DURING THE
MORNING...WHILE WARMER AIR ALOFT ADVECTS INTO THE AREA. THIS WILL
RESULT IN A MIX OF SNOW...RAIN...FREEZING RAIN AND SLEET IN THE
COLUMBIA BASIN AND THE LOWER ELEVATIONS OF CENTRAL OREGON.
TEMPERATURES SHOULD WARM ABOVE FREEZING BY AFTERNOON...BUT WITH
LIGHT BOUNDARY LAYER WINDS EXPECTED...THIS CANNOT BE GUARANTEED.
HAVE THEREFORE KEPT A CHANCE OF SLEET IN THE FORECAST FOR THE
AFTERNOON...BUT HAVE REMOVED THE CHANCE OF FREEZING RAIN.
PRECIPITATION SHOULD THEN TRANSITION BACK TO MOSTLY SNOW ON THURSDAY
NIGHT BEFORE CHANGING BACK TO RAIN ON FRIDAY. IN THE MOUNTAINS
SEVERAL INCHES OF SNOW CAN BE EXPECTED...WITH THE GREATEST AMOUNTS
LIKELY FROM CENTRAL OREGON THROUGH THE BLUE AND WALLOWA MOUNTAINS.
LESSER AMOUNTS ARE ANTICIPATED IN CENTRAL WASHINGTON SINCE THE
PRIMARY MOISTURE AXIS SHOULD REMAIN OVER OREGON.

ONE MORE FORECAST ISSUE IS THE TIMING OF THE WARM FRONTS DEPARTURE
AND THE SUBSEQUENT LOWERING SNOW LEVELS. THE 00Z ECMWF MOVES THIS
SYSTEM OUT OF THE AREA ON FRIDAY AFTERNOON...BUT THE GFS HOLDS THE
TROUGH OVER THE AREA THROUGH FRIDAY NIGHT. SO HAVE KEPT A CHANCE OF
RAIN AND SNOW THROUGH SATURDAY. MUCH DRIER CONDITIONS CAN THEN BE
EXPECTED ON SUNDAY AND MONDAY SINCE BOTH MODELS MOVE A FAIRLY STRONG
RIDGE OF HIGH PRESSURE OVER THE REGION. YET DUE TO HIGH
UNCERTAINTIES IN THIS TIME FRAME...AM RELUCTANT TO LOWER PRECIP
CHANCES TOO FAR BELOW CLIMATOLOGY.

ANOTHER WINTER STORM SHOULD MOVE INTO THE PACIFIC NORTHWEST ON
MONDAY OR MONDAY NIGHT.  TRIMARCO

&&

.AVIATION...12Z TAFS...THE NEXT STORM SYSTEM IS MOVING INLAND.
CIGS/VIS AT KRDM SHOULD RUN VFR THROUGH THE PERIOD...THOUGH BRIEF
DROPS TO MVFR ARE LIKELY IN RAIN AND SNOW. ALL OTHER TAF SITES
STRUGGLED WITH FOG OVERNIGHT...BUT CONDITIONS ARE IMPROVING AS
PRECIPITATION MOVES INTO THE AREA. HOWEVER...MVFR AND LOWER
CONDITIONS CAN BE EXPECTED THROUGH MUCH OF THE PERIOD WITH IFR OR
LOWER COMMON IN SNOW...RAIN AND FREEZING RAIN. SOUTHEAST WINDS OF 10
TO 15 KTS ARE EXPECTED AT KALW AND KPDT BY LATE MORNING. THESE WINDS
SHOULD WARM TEMPS ABOVE FREEZING AND RAISE CIGS/VIS.  82

&&

.PRELIMINARY POINT TEMPS/POPS...
PDT  34  31  38  30 / 100  70  40  70
ALW  34  31  39  32 / 100  70  40  70
PSC  33  30  37  31 / 100  60  30  50
YKM  32  26  35  21 / 100  60  20  20
HRI  33  31  39  31 /  90  60  30  60
ELN  32  26  34  20 / 100  60  30  20
RDM  41  29  42  28 /  80  60  40  60
LGD  32  31  35  33 / 100  90  60  60
GCD  33  30  36  33 /  90  80  60  50
DLS  34  33  39  33 / 100  50  30  40

&&

.PDT WATCHES/WARNINGS/ADVISORIES...
OR...WINTER WEATHER ADVISORY UNTIL 10 AM PST WEDNESDAY ORZ050-505.

     WINTER STORM WARNING UNTIL 10 AM PST WEDNESDAY ORZ502-503.

     WINTER WEATHER ADVISORY UNTIL 10 AM PST THIS MORNING ORZ042.

     WINTER STORM WARNING UNTIL 4 PM PST WEDNESDAY ORZ506.

     WINTER WEATHER ADVISORY UNTIL 4 AM PST WEDNESDAY ORZ509.

     WINTER WEATHER ADVISORY UNTIL 10 AM PST THIS MORNING
     ORZ044-507-508.

     WINTER WEATHER ADVISORY UNTIL 10 AM PST THIS MORNING ORZ041.

     BLIZZARD WARNING UNTIL 10 AM PST WEDNESDAY ORZ049.

WA...WINTER STORM WARNING UNTIL 10 AM PST WEDNESDAY WAZ030.

     WINTER WEATHER ADVISORY UNTIL 4 AM PST WEDNESDAY WAZ027.

     WINTER WEATHER ADVISORY UNTIL 4 AM PST WEDNESDAY WAZ521.

     WINTER STORM WARNING UNTIL 4 AM PST WEDNESDAY WAZ520.

     WINTER WEATHER ADVISORY UNTIL 10 AM PST THIS MORNING WAZ028-029.

     WINTER WEATHER ADVISORY UNTIL 10 AM PST THIS MORNING WAZ024.

     WINTER STORM WARNING UNTIL 4 AM PST WEDNESDAY WAZ026.

&&

THREAT INDEX
TODAY : RED
WEDNESDAY : RED
THURSDAY : YELLOW

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

97/82/82

HAZARDOUS WEATHER OUTLOOK...UPDATED
NATIONAL WEATHER SERVICE PENDLETON OR
1055 PM PST MON NOV 29 2010

UPDATED TO FOR FREEZING FOG ADVISORY EXTENSION

ORZ041-042-044-049-050-502-503-505>509-WAZ024-026>030-520-521-
301415-
EASTERN COLUMBIA RIVER GORGE OF OREGON-NORTH CENTRAL OREGON-
LOWER COLUMBIA BASIN OF OREGON-GRANDE RONDE VALLEY-WALLOWA COUNTY-
NORTHERN BLUE MOUNTAINS OF OREGON-
SOUTHERN BLUE MOUNTAINS OF OREGON-JOHN DAY BASIN-OCHOCO-
JOHN DAY HIGHLANDS-
FOOTHILLS OF THE NORTHERN BLUE MOUNTAINS OF OREGON-
FOOTHILLS OF THE SOUTHERN BLUE MOUNTAINS OF OREGON-
EAST SLOPES OF THE OREGON CASCADES-
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 WASHINGTON CASCADES-SIMCOE HIGHLANDS-
1055 PM PST MON NOV 29 2010

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

.DAY ONE...TODAY AND TONIGHT

WINTER MIX
     EAST SLOPES OF THE WASHINGTON CASCADES, SIMCOE 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, EASTERN COLUMBIA RIVER GORGE OF OREGON, NORTH
     CENTRAL OREGON, EAST SLOPES OF THE OREGON CASCADES, LOWER
     COLUMBIA BASIN OF OREGON, WALLOWA COUNTY, FOOTHILLS OF THE
     NORTHERN BLUE MOUNTAINS OF OREGON, NORTHERN BLUE MOUNTAINS OF
     OREGON, SOUTHERN BLUE MOUNTAINS OF OREGON, FOOTHILLS OF THE
     SOUTHERN BLUE MOUNTAINS OF OREGON, JOHN DAY BASIN, OCHOCO-JOHN
     DAY HIGHLANDS

STRONG WIND
     GRANDE RONDE VALLEY

DENSE FOG
     FOOTHILLS OF THE BLUE MOUNTAINS OF WASHINGTON, FOOTHILLS OF
     THE NORTHERN BLUE MOUNTAINS OF OREGON, FOOTHILLS OF THE
     SOUTHERN BLUE MOUNTAINS OF OREGON

A STRONG WINTER STORM WILL MOVE INTO THE REGION LATER THIS EVENING.
HEAVY SNOW WILL BECOME POSSIBLE IN THE MOUNTAINS WHILE A WINTRY MIX
OF SNOW...RAIN...FREEZING RAIN AND SLEET CAN BE EXPECTED IN THE
LOWER ELEVATIONS. NUMEROUS WARNINGS AND ADVISORIES ARE IN EFFECT.
PLEASE REFER TO NWS PRODUCT PDXWSWPDT FOR DETAILS.

TIGHT SURFACE PRESSURE GRADIENTS WILL CAUSE STRONG SOUTHERLY WINDS
IN THE GRANDE RONDE VALLEY. ALSO AREAS OF FREEZING FOG WILL DRIFT
AROUND THE BLUE MOUNTAIN FOOTHILLS OVERNIGHT. AS A RESULT A WIND
ADVISORY AND A FREEZING FOG ADVISORY HAVE BEEN ISSUED UNDER NWS
PRODUCT PDXNPWPDT.

.DAYS TWO THROUGH SEVEN...TUESDAY THROUGH SUNDAY

WINTER MIX TUESDAY
     EAST SLOPES OF THE WASHINGTON CASCADES, SIMCOE 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, EASTERN COLUMBIA RIVER GORGE OF OREGON, NORTH
     CENTRAL OREGON, EAST SLOPES OF THE OREGON CASCADES, LOWER
     COLUMBIA BASIN OF OREGON, WALLOWA COUNTY, FOOTHILLS OF THE
     NORTHERN BLUE MOUNTAINS OF OREGON, NORTHERN BLUE MOUNTAINS OF
     OREGON, SOUTHERN BLUE MOUNTAINS OF OREGON, FOOTHILLS OF THE
     SOUTHERN BLUE MOUNTAINS OF OREGON, JOHN DAY BASIN, OCHOCO-JOHN
     DAY HIGHLANDS

STRONG WIND TUESDAY
     GRANDE RONDE VALLEY

A PACIFIC STORM SYSTEM WILL CONTINUE TO BRING HEAVY SNOW TO THE
MOUNTAINS AND MIXED WINTRY PRECIPITATION TO THE LOWER ELEVATIONS
THROUGH TUESDAY. DETAILS CAN BE FOUND IN THE NUMEROUS
WATCHES...WARNINGS AND ADVISORIES LISTED IN NWS PRODUCT PDXWSWPDT.
THE WIND ADVISORY FOR THE GRANDE RONDE VALLEY WILL ALSO CONTINUE
THROUGH TUESDAY NIGHT.

WINTER MIX WEDNESDAY AND THURSDAY
     FOOTHILLS OF THE BLUE MOUNTAINS OF WASHINGTON, NORTHWEST BLUE
     MOUNTAINS OF WASHINGTON, NORTH CENTRAL OREGON, EAST SLOPES OF
     THE OREGON CASCADES, GRANDE RONDE VALLEY, WALLOWA COUNTY,
     FOOTHILLS OF THE NORTHERN BLUE MOUNTAINS OF OREGON, NORTHERN
     BLUE MOUNTAINS OF OREGON, SOUTHERN BLUE MOUNTAINS OF OREGON,
     FOOTHILLS OF THE SOUTHERN BLUE MOUNTAINS OF OREGON, JOHN DAY
     BASIN, OCHOCO-JOHN DAY HIGHLANDS

WET UNSETTLED WEATHER WILL PERSIST ON WEDNESDAY AND THURSDAY AS
SOUTHWESTERLY FLOW PULLS A DEEP FETCH OF PACIFIC MOISTURE INTO THE
AREA. HEAVY SNOW WILL THEREFORE REMAIN POSSIBLE IN THE MOUNTAINS
WITH MIXED PRECIPITATION LIKELY IN THE LOWER ELEVATIONS.

.SPOTTER INFORMATION STATEMENT...

SPOTTER ACTIVATION WILL BE LIKELY.

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.