Heavy Snow in Oregon, December 6 to 7, 2004

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE PENDLETON OREGON
230 PM PST MON DEC 6 2004

.SHORT TERM...TONIGHT THROUGH WEDNESDAY NIGHT...A STRONG SHORT WAVE
THAT MOVED THROUGH THE REGION THIS MORNING IS NOW HEADING NORTHEAST
OUT OF THE AREA INTO NE WASHINGTON AND IDAHO.  MEANWHILE...THE NEXT
SYSTEM IS QUICKLY APPROACHING IN THE FORM OF A SURFACE LOW WHICH IS
EXPECTED TO SWING ACROSS NORTH CENTRAL OREGON AND THE FOOTHILLS OF
THE BLUE MOUNTAINS.  ABUNDANT MOISTURE ON THE EAST SIDE OF THIS LOW
WILL PRODUCE WIDESPREAD RAIN AND SNOW.  MEANWHILE...AREAS ON THE
COLD SIDE OF THE SYSTEM WILL REMAIN OUT OF THE WARM SECTOR WITH
LOWER SNOW LEVELS ACROSS THE EASTERN COLUMBIA RIVER GORGE...YAKIMA
AND KITTITAS VALLEYS...AND THE EAST SLOPES OF THE SOUTHERN
WASHINGTON CASCADES.  SNOW LEVELS WILL GENERALLY BE NEAR 500 FEET IN
THE YAKIMA VALLEY AND 1000 FEET IN THE EASTERN COLUMBIA RIVER
GORGE.  TEMPERATURES AT 1 PM WHERE IN THE UPPER 30S AT YAKIMA AND
ELLENSBURG...BUT WET BULB ZERO TEMPERATURES WILL BE NEAR THE SURFACE
ALLOWING PRECIPITATION TO FALL PRIMARILY AS WET SNOW WITH SURFACE
TEMPERATURES NEAR 32F.  THUS...A SNOW ADVISORY WILL BE ISSUED FOR
THE YAKIMA AND KITTITAS VALLEYS.  ELSEWHERE...4 TO 8 INCHES OF SNOW
IS EXPECTED IN THE OCHOCO-JOHN DAY HIGHLANDS WHERE THE SNOW ADVISORY
WILL BE UPGRADED TO A HEAVY SNOW WARNING.  A HEAVY SNOW WARNING WILL
ALSO BE ISSUED FOR CENTRAL OREGON ABOVE 3500 FEET MAINLY SOUTH OF
BEND WHERE TOTAL SNOW ACCUMULATIONS AFTER SNOW TONIGHT ARE EXPECTED
TO RANGE FROM 7-11 INCHES.  LESSER AMOUNTS OF 3-5 INCHES ARE
EXPECTED IN NORTH CENTRAL OREGON...GRANDE RONDE VALLEY...AND WALLOWA
COUNTY WHERE A SNOW ADVISORY WILL BE ISSUED.

WE WILL BE IN A TEMPORARY LULL TOMORROW AS THE SYSTEM FOR TONIGHT
MOVES EAST OF THE AREA AND THE NEXT SYSTEM RAPIDLY APPROACHES FROM
THE WEST.  THIS SYSTEM WILL BE IN THE FORM OF A MOIST WARM FRONT
WHICH WILL SLIDE ACROSS THE AREA TUESDAY NIGHT AND WEDNESDAY FOR
INCREASING CHANCES OF PRECIPITATION AGAIN.  DUE TO THE STRONG
WESTERLY FLOW WITH THIS SYSTEM PRECIPITATION AMOUNTS WILL BE LIMITED
OVER THE COLUMBIA BASIN.  SNOW LEVELS WILL CONTINUE TO RISE THROUGH
THIS TIME FRAME AS WELL.  GFS/ETA MODELS THEN AGREE IN SHIFTING A
MOIST BAROCLINIC BOUNDARY SOUTH OVER OREGON WHERE PRECIPITATION WILL
LIKELY PERSIST INTO WEDNESDAY NIGHT.  WOLF

.LONG TERM...THURSDAY THROUGH MONDAY...LATEST EURO/GFS/CANADIAN
EXTENDED MODELS ARE IN DECENT AGREEMENT THROUGH THE REMAINDER OF THE
WORK WEEK. A BROAD RIDGE WILL BUILD ACROSS THE GREAT BASIN THURSDAY
AND FRIDAY...LEAVING OUR FORECAST AREA UNDER A NEARLY ZONAL FLOW
ALOFT. ABUNDANT MOISTURE WILL COMBINE WITH A A QUASI-STATIONARY
FRONT SITUATED FROM EAST TO WEST ACROSS THE PAC NW ON THURSDAY TO
PROVIDE A CHANCE OF SHOWERS AREAWIDE...EXCEPT FOR A SLIGHT CHANCE
OVER THE BASIN. MUCH OF THE MOISTURE IS SHUNTED NORTHWARD OUT OF OUR
AREA ON FRIDAY AS THE FRONTAL BOUNDARY MIGRATES NORTH AS WELL. AS A
RESULT...WARM CONDITIONS AND RELATIVELY DRY AIR WILL INFILTRATE THE
REGION. SNOW LEVELS WILL RISE ABOVE 6000 FEET AND MAX TEMPS SHOULD
AT LEAST HIT THE LOWER TO MID 50S IN MANY LOCATIONS. MODEL SOLUTIONS
DIVERGE FOR THE WEEKEND AND EARLY NEXT WEEK...WITH THE GFS BRINGING
A WEAK COLD FRONT THROUGH ON SATURDAY AND THE ECMWF/CAN KEEPING THE
COLDER AIR OFF-SHORE. HAVE TRENDED THE FORECAST TOWARD THE EURO/CAN
SOLUTIONS FOR SAT-MON...BUT HEDGED ON THE COOLER/WETTER SIDE GIVEN
THE GFS. JWM

&&

.PRELIMINARY POINT TEMPS/POPS...
PENDLETON (AIRPORT) 038 052 040 056 / 070 040 030 050
WALLA WALLA         038 049 040 053 / 070 040 030 050
TRI-CITIES          034 049 038 053 / 060 030 030 040
YAKIMA              030 043 033 047 / 080 040 030 040
HERMISTON           034 048 038 052 / 060 030 030 040
ELLENSBURG          029 040 033 044 / 080 040 040 040
REDMOND             034 044 035 048 / 100 050 040 050
LA GRANDE           033 042 036 046 / 090 050 040 060
JOHN DAY            033 046 033 050 / 090 060 040 050
THE DALLES          034 045 035 049 / 080 050 030 070
&&

.PDT WATCHES/WARNINGS/ADVISORIES...
OR...HEAVY SNOW WARNING TONIGHT ZONES 43 AND 48.
  ...SNOW ADVISORY TONIGHT ZONES 42...47...49 AND 50
WA...SNOW ADVISORY TONIGHT ZONES 26...27
&&

FOR ADDITIONAL WEATHER INFORMATION, CHECK OUR WEB SITE AT...
WWW.WEATHER.GOV/PENDLETON
86

HAZARDOUS WEATHER OUTLOOK...UPDATED
NATIONAL WEATHER SERVICE PENDLETON OREGON
300 PM PST MON DEC 6 2004

ORZ041>050-WAZ024>030-071300-
NORTH CENTRAL OREGON-CENTRAL OREGON-LOWER COLUMBIA BASIN (OR)-
FOOTHILLS OF THE BLUE MOUNTAINS (OR)-BLUE MOUNTAINS-JOHN DAY BASIN-
OCHOCO-JOHN DAY HIGHLANDS-GRANDE RONDE VALLEY-WALLOWA COUNTY-
EASTERN COLUMBIA RIVER GORGE (WA)-
EAST SLOPES OF THE SOUTHERN CASCADES-KITTITAS VALLEY-YAKIMA VALLEY-
LOWER COLUMBIA BASIN (WA)-FOOTHILLS OF THE BLUE MOUNTAINS (WA)-
NORTHWEST BLUE MOUNTAINS-
300 PM PST MON DEC 6 2004

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

.DAY ONE...TODAY AND TONIGHT

HEAVY SNOW WARNING TONIGHT
    CENTRAL OREGON AND THE OCHOCO-JOHN DAY HIGHLANDS.

SNOW ADVISORY TONIGHT
    GRANDE RONDE VALLEY-WALLOWA COUNTY...NORTH CENTRAL
    OREGON...JOHN DAY VALLEY...AND KITTITAS-YAKIMA VALLEY.

A PACIFIC WINTER STORM WILL MOVE THROUGH THE REGION
TONIGHT...BRINGING SNOW TO MUCH OF THE MUCH OF THE AREA. A WARM
FRONT WITH ABUNDANT MOISTURE WILL MOVE SOUTH TO NORTH OVER THE AREA
AND BRING HEAVY SNOW TO HIGHER ELEVATIONS ACROSS CENTRAL OREGON AND
THE OCHOCO-JOHN DAY HIGHLANDS. THE SNOW ACROSS THE YAKIMA AND
KITTITAS VALLEYS WILL BE ASSOCIATED WITH COLD AIR TRAPPED NEAR THE
CASCADES. PLEASE REFER TO PRODUCT PDXWSWPDT WWUS46 KPDT FOR
DETAILS.

.DAYS TWO THROUGH SEVEN...TUESDAY THROUGH SUNDAY

THE PROBABILITY FOR WIDESPREAD HAZARDOUS WEATHER IS LOW.

A STRONG WESTERLY FLOW ALOFT AND A SERIES OF DISTURBANCES WILL BRING
MORE RAIN AND SNOW ACROSS THE REGION THROUGH THE END OF THE WEEK.
SNOW LEVELS WILL GRADUALLY RISE THROUGH THE PERIOD AND WILL BE NEAR
5500-6000 FEET THURSDAY AND FRIDAY. BREEZY WINDS WITH LOCAL WIND
GUSTS OF 35-40 MPH CAN ALSO BE EXPECTED.

.SPOTTER INFORMATION STATEMENT...

SPOTTER ACTIVATION WILL BE LIKELY.

WEATHER SPOTTERS ARE ENCOURAGED TO REPORT SIGNIFICANT WEATHER
CONDITIONS ACCORDING TO STANDARD OPERATING PROCEDURES.

PROTOTYPE GRAPHICAL FORECASTS OF WEATHER HAZARDS OUT TO SEVEN DAYS
ARE DISPLAYED ON THE WORLD WIDE WEB AT:

WWW.WRH.NOAA.GOV/PENDLETON/FORECAST/HWOGRAPHICS/HWOGRAPHICS.PHP

ALL LETTERS IN THE ABOVE URL ARE LOWER CASE...EXCEPT THE G IN
HWOGRAPHICS AND THE G IN HWOGRAPHICS.PHP.