Winter Storm Warning 4, NWS Pendleton, OR

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE PENDLETON OR
350 AM PST THU DEC 27 2007

UPDATED AVIATION DISCUSSION

.SHORT TERM...TODAY THROUGH FRIDAY NIGHT.  A BIG PACIFIC STORM IS
MOVING ONSHORE AND WILL BE A MAJOR SNOW PRODUCER OVER MOST OF OUR
FORECAST AREA OVER THE NEXT 24-36 HOURS.  SNOW WILL DEVELOP THIS
MORNING ALONG THE EAST SLOPES OF THE CASCADES AND WILL INCREASE IN
INTENSITY BY EARLY AFTERNOON.  THE EASTERN COLUMBIA RIVER
GORGE...THE KITTITAS AND YAKIMA VALLEYS...AND CENTRAL AND NORTH
CENTRAL OREGON  WILL ALSO SEE SNOW DEVELOPING AROUND NOON TODAY AND
INCREASING IN INTENSITY IN THE LATE AFTERNOON AND EVENING. BY EARLY
FRIDAY MORNING...THE FLOW WILL SWITCH TO THE WEST AND THE BOUNDARY
LAYER WINDS WILL SHIFT TO THE SW.  THEREFORE...PRECIPITATION IN THE
VALLEYS AND ACROSS CENTRAL OREGON WILL TAPER OFF ON FRIDAY. THE ONLY
EXCEPTION WILL BE AREAS JUST NEAR THE CASCADES WHERE SNOW WILL SPILL
OVER AND CONTINUE TO BRING PERIODS OF HEAVY SNOW THROUGH FRIDAY
AFTERNOON. WILL CUT THE SNOW ADVISORY FOR THE YAKIMA/KITTITAS VALLEY
AND THE EASTERN COLUMBIA RIVER GORGE TO 4 AM FRIDAY RATHER THAN 10
AM.

THE TIMING OF THE SYSTEM IS A LITTLE SLOWER THAN PREVIOUSLY
FORECAST...SO THE EASTERN MOUNTAINS WILL NOT SEE SNOW INCREASING
UNTIL THIS EVENING.  CONFIDENT THAT HEAVY SNOW WILL DEVELOP OVER THE
NORTHERN BLUES AND THE GRANDE RONDE VALLEY OVERNIGHT AND ON FRIDAY.
I WILL BE ISSUING HEAVY SNOW WARNINGS FOR THE BLUES AND A BLIZZARD
WARNING IN THE GRANDE RONDE VALLEY.  THE EASTERN MOUNTAINS AND
VALLEYS WILL SEE AREAS OF BLOWING SNOW...BUT WHITE OUT CONDITIONS
WILL CAUSE MAJOR PROBLEMS NEAR LADD AND PYLES CANYONS TONIGHT.

FOR THE SOUTHERN BLUES AND THE JOHN DAY BASIN AND OCHOCO
HIGHLANDS...BELIEVE SNOW AMOUNTS TONIGHT WILL REACH ADVISORY
CRITERIA BUT NOT HEAVY SNOW WARNING CRITERIA.

AS FAR AS THE BASIN AND BLUE MOUNTAIN FOOTHILLS...THERE MAY BE  SNOW
ACCUMULATIONS UP TO 2 INCHES IN AREAS WEST OF THE TRI-CITIES AND
HANFORD.  OTHERWISE...SOUTHERLY WINDS WILL PROVIDE ENOUGH
DOWNSLOPING ALONG THE FOOTHILLS TO WARM TEMPERATURES INTO THE 40S.
THE ONLY EXCEPTION WILL BE NEAR CONDON AND FOSSIL THAT MAY SEE LIGHT
ACCUMULATIONS OVER THE NEXT 24 HOURS.  JOHNSON

.LONG TERM...SATURDAY THROUGH WEDNESDAY...ACTIVE WEATHER PATTERN
WILL CONTINUE THROUGH THE WEEKEND. JETSTREAM WILL REMAIN OVER
EASTERN WASHINGTON OR OREGON WITH FREQUENT JET MAXES TRIGGERING
PRECIPITATION IN WEST TO NORTHWEST FLOW. THIS MAY LIMIT
PRECIPITATION IN NORMALLY RAIN SHADOWED AREAS IN COLUMBIA BASIN.
THERE WILL BE A FEW LINGERING SHOWERS IN THE NORTHEAST OREGON
MOUNTAINS MONDAY AS A A RIDGE BUILDS OFFSHORE. MONDAY NIGHT THROUGH
WEDNESDAY THE RIDGE WILL MOVE OVER THE PACIFIC NORTHWEST GIVING US A
TEMPORARY BREAK FROM THE FREQUENT STORMS PASSING THROUGH THE
REGION.  COONFIELD

&&

.AVIATION...VFR CONDITIONS WILL PERSIST UNTIL 18-20Z ACROSS ALL TAF
SITES. CEILINGS WILL LOWER TO 05-10 KFT ACROSS THE AREA AS NEXT
STORM DEVELOPS IN THE AFTERNOON. MVFR CEILING AND VISIBILITY IS
POSSIBLE AS EARLY AS 18Z AT DLS...WITH MVFR CEILINGS AND VISIBILITY
PREVALENT AT YKM AND RDM AS WELL BY 22Z. MVFR AND OCCASIONAL IFR
CONDITIONS WILL CONTINUE INTO THE NIGHT AS THE NEXT SYSTEM MOVES
THROUGH. LOWER CEILINGS AND VISIBILITY WILL BE DELAYED BY
DOWNSLOPING WINDS AT PDT AND ALW...BUT WILL PERSIST LONGER AFTER
DEVELOPMENT BETWEEN 06-08Z.  76

&&

.PRELIMINARY POINT TEMPS/POPS...
PDT  39  38  39  29 /  40  70  30  50
ALW  40  37  38  32 /  40  80  30  50
PSC  38  31  40  30 /  50  80  20  40
YKM  32  26  35  21 /  70  90  30  40
HRI  38  32  40  29 /  50  80  20  50
ELN  30  25  32  24 /  80  90  50  40
RDM  34  24  37  26 /  70  80  50  60
LGD  29  24  33  28 /  40  80  70  60
GCD  31  26  35  26 /  40  70  60  70
DLS  34  31  40  32 /  80  90  40  60

&&

.PDT WATCHES/WARNINGS/ADVISORIES...
OR...SNOW ADVISORY FROM 10 AM THIS MORNING TO 10 AM PST FRIDAY FOR
     ORZ042-043.

     HEAVY SNOW WARNING UNTIL 4 AM PST EARLY THIS MORNING FOR ORZ502.

     WINTER STORM WARNING FROM 6 PM THIS EVENING TO 6 PM PST FRIDAY
     FOR ORZ502.

     SNOW ADVISORY FROM 6 PM THIS EVENING TO 6 PM PST FRIDAY FOR
     ORZ503.

     BLIZZARD WARNING FROM 6 PM THIS EVENING TO 6 PM PST FRIDAY FOR
     ORZ049.

     SNOW ADVISORY FROM 10 AM THIS MORNING TO 4 AM PST FRIDAY FOR
     ORZ041.

     SNOW ADVISORY FROM 6 PM THIS EVENING TO 10 AM PST FRIDAY FOR
     ORZ505-506.

WA...SNOW ADVISORY FROM 10 AM THIS MORNING TO 10 AM PST FRIDAY FOR
     WAZ501-502.

     HEAVY SNOW WARNING UNTIL 4 AM PST EARLY THIS MORNING FOR WAZ030.

     WINTER STORM WARNING FROM 6 PM THIS EVENING TO 6 PM PST FRIDAY
     FOR WAZ030.

     SNOW ADVISORY FROM 10 AM THIS MORNING TO 4 AM PST FRIDAY FOR
     WAZ024-026-027.

&&

TI:RRY
FOR ADDITIONAL WEATHER INFORMATION, CHECK OUR WEB SITE AT...
WWW.WEATHER.GOV/PENDLETON
85/76/76

HAZARDOUS WEATHER OUTLOOK...CORRECTED
NATIONAL WEATHER SERVICE PENDLETON OR
359 PM PST WED DEC 26 2007

UPDATED FOR LATEST HEADLINES

ORZ041>044-049-050-501>506-WAZ024-026>030-501-502-271415-
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-
EAST SLOPES OF THE CENTRAL CASCADES OF WASHINGTON-
EAST SLOPES OF THE SOUTHERN CASCADES OF WASHINGTON-
359 PM PST WED DEC 26 2007

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

.DAY ONE...THIS AFTERNOON AND TONIGHT

HEAVY SNOW WARNING REMAINS IN EFFECT UNTIL 11 PM PST THIS EVENING
     NORTHWEST BLUE MOUNTAINS OF WASHINGTON, NORTHERN BLUE MOUNTAINS
     OF OREGON

AN ONSHORE NORTHWEST FLOW ALOFT WILL CONTINUE TO BRING MOISTURE INTO
THE REGION THIS AFTERNOON AND TONIGHT. MODERATE TO HEAVY SNOW IS
POSSIBLE ALONG THE CASCADE CRESTS AS WELL AS IN THE NORTHERN BLUE
MOUNTAINS IN SOUTHEAST WASHINGTON AND NORTHEAST OREGON. PLEASE REFER
TO PRODUCT PDXWSWPDT (WMO HEADER WWUS KPDT) FOR MORE INFORMATION
REGARDING THE CURRENT HEAVY SNOW WARNING.

.DAYS TWO THROUGH SEVEN...THURSDAY THROUGH TUESDAY

SNOW THURSDAY...THURSDAY NIGHT AND FRIDAY
     EAST SLOPES OF THE CENTRAL CASCADES OF WASHINGTON, EAST SLOPES
     OF THE SOUTHERN CASCADES OF WASHINGTON, KITTITAS VALLEY,
     YAKIMA VALLEY, NORTHWEST BLUE MOUNTAINS, NORTH CENTRAL OREGON,
     CENTRAL OREGON, GRANDE RONDE VALLEY, NORTHERN BLUE MOUNTAINS
     OF OREGON, SOUTHERN BLUE MOUNTAINS OF OREGON

A STRONG PACIFIC STORM SYSTEM WILL IMPACT THE INTERIOR PACIFIC
NORTHWEST FROM THURSDAY THROUGH FRIDAY. MODERATE TO HEAVY SNOW WILL
BE POSSIBLE IN THE ABOVE MENTIONED AREAS FROM THURSDAY THROUGH
FRIDAY AND SEVERAL WINTER STORM WATCHES ARE IN EFFECT FOR THESE
AREAS FROM THURSDAY MORNING THROUGH FRIDAY AFTERNOON. PLEASE REFER
TO PRODUCT PDXWSWPDT (WMO HEADER WWUS KPDT) FOR MORE INFORMATION
CONCERNING THE CURRENT WINTER STORM WATCHES.

.SPOTTER INFORMATION STATEMENT...

SPOTTER ACTIVATION WILL BE LIKELY FOR HEAVY SNOW IN THE NORTHERN
BLUE MOUNTAINS THIS AFTERNOON AND THIS EVENING.

SPOTTER ACTIVATION MAY BE REQUIRED FOR PERIODS OF MODERATE TO HEAVY
SNOW FROM THURSDAY MORNING THROUGH FRIDAY AFTERNOON ALONG THE EAST
SLOPES OF THE CENTRAL AND SOUTHERN WASHINGTON CASCADES...THE
KITTITAS VALLEY...THE YAKIMA VALLEY...THE EASTERN COLUMBIA RIVER
GORGE...THE EAST SLOPES OF THE NORTHERN AND CENTRAL OREGON
CASCADES...NORTH CENTRAL OREGON...CENTRAL OREGON...THE NORTHERN AND
SOUTHERN BLUE MOUNTAINS AND THE GRANDE RONDE VALLEY.

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.