615
FXUS66 KPDT 252236
AFDPDT
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE PENDLETON OR
236 PM PST TUE NOV 25 2025
DISCUSSION
TODAY THROUGH WEDNESDAY MORNING: CURRENT RADAR AND
SATELLITE IMAGERY THIS AFTERNOON SHOWS THE LEADING EDGE OF A WARM
FRONT BOUNDARY PUSHING A VERY LIGHT BAND OF PRECIPITATION ACROSS
THE COLUMBIA BASIN, WITH LIGHT TO MODERATE RAIN/SNOW FALLING
ACROSS THE WA CASCADE CREST AND KITTITAS VALLEY.
THE FRONTAL BOUNDARY WILL CONTINUE TO PUSH ACROSS THE PACNW
TONIGHT, ALLOWING A WARM, MOIST AIRMASS TO FILTER INTO THE REGION
AND FOR SNOW LEVELS TO RISE ABOVE PASS LEVEL BY TOMORROW MORNING.
THAT SAID, THIS WARM AIRMASS WILL BE SLOW TO MIX OUT STUBBORN
COLD POOL POCKETS ACROSS PORTIONS OF THE WA CASCADE EAST SLOPES,
BLUES, WALLOWA/KITTITAS VALLEYS, AND HIGHER ELEVATIONS OF THE
YAKIMA VALLEY OVERNIGHT, WHERE SNOW(MOUNTAINS) OR A RAIN/SNOW MIX
(VALLEYS) WILL MOSTLY DOMINATE THE PRECIPITATION TYPE. FORECAST
SOUNDINGS INDICATE THAT THE WARMER AIRMASS WILL OVERRIDE THESE
AREAS WHEN PRECIPITATION IS ONGOING TONIGHT, RESULTING IN LOW TO
MODERATE CHANCES(20-50%) FOR LIGHT FREEZING RAIN (0.01-0.1 INCHES)
TO MIX IN WITH SNOW AND/OR RAIN BETWEEN 10PM AND 7AM TONIGHT AND
TOMORROW MORNING. IN THE REMAINDER OF THE LOWER ELEVATION AREAS,
THE WARM AIRMASS WILL HAVE LESS TROUBLE MIXING DOWN TO THE SURFACE
RESULTING IN MOSTLY LIGHT RAIN THROUGHOUT TOMORROW MORNING. IN
THE MOUNTAINS, LIGHT TO MODERATE SNOW ACCUMULATIONS WILL CONTINUE
INTO TONIGHT BEFORE TRANSITIONING INTO A RAIN/SNOW MIX OR MOSTLY
RAIN BY TOMORROW MORNING. LATE IN THE MORNING INTO THE EARLY
AFTERNOON, A BRIEF BREAK IN PRECIPITATION WILL DEVELOP BEFORE THE
NEXT SYSTEM ARRIVES TO THE FORECAST AREA.
THERE IS MODERATE TO HIGH CONFIDENCE (55-85%) THAT BY TOMORROW
MORNING THE WA CASCADE EAST SLOPES WILL SEE 5-8 INCHES OF SNOW
ACCUMULATIONS; THE KITTITAS/WALLOWA VALLEYS AND RIDGES OF THE
YAKIMA VALLEY WILL SEE UP TO 1.5 INCHES OF SNOWFALL; THE NORTHERN
BLUES WILL SEE 3 TO 6 INCHES OF SNOWFALL; AND THE OR CASCADES 1 TO
3 INCHES OF SNOWFALL. IN THE AFOREMENTIONED AREAS, THERE IS ALSO A
MODERATE CONFIDENCE (50-70%) IN AT LEAST A LIGHT GLAZE OF ICE
ACCUMULATIONS THROUGH TOMORROW MORNING.
WEDNESDAY AFTERNOON THROUGH FRIDAY: ENSEMBLE AND DETERMINISTIC
GUIDANCE ARE IN GOOD AGREEMENT THAT A TRANSIENT RIDGE WILL SLIDE
OVER THE PACNW WEDNESDAY AFTERNOON. WHILE CONDITIONS WOULD
NORMALLY REMAIN DRY UNDER A RIDGE, A WARM FRONT LIFTING NORTH LATE
WEDNESDAY AFTERNOON WILL RESULT IN A RENEWAL OF LIGHT RAIN WITH
HIGH MOUNTAIN SNOW OR RAIN/SNOW MIX THROUGH WEDNESDAY
NIGHT(CONFIDENCE 55-75%).
HIGH MOUNTAIN SNOW AND/OR A WINTRY MIX WITH LOWER ELEVATION RAIN
WILL CONTINUE THURSDAY AS A CLOSED LOW SLIDES INTO WA, THEN
OPENING INTO A TROUGH AND SWINGING SOUTHEAST AS THE LOW FEATURE
PUSHES FURTHER INLAND THURSDAY NIGHT THROUGH FRIDAY MORNING. BY
FRIDAY NIGHT THE TROUGH WILL EXIT THE REGION TO THE SOUTHEAST WITH
A DRY NORTHWEST FLOW DEVELOPING ALOFT. THIS WILL RESULT IN
PRECIPITATION CHANCES WANING ACROSS THE REGION INTO
SATURDAY(CONFIDENCE 50-75%).
SATURDAY THROUGH TUESDAY: ENSEMBLE CLUSTER GUIDANCE BEGINS IN
DISAGREEMENT FOR SATURDAY AS ABOUT 30% OF MEMBERS FROM THE ECMWF
AND GFS ENSEMBLE SUITES SHOW ANOTHER SHORTWAVE TROUGH DIVING
ACROSS THE PACNW BY SATURDAY MORNING, WITH LIGHT LOW ELEVATION
RAIN AND MOUNTAIN SNOW DEVELOPING ACROSS THE FORECAST AREA.
MEANWHILE, THE REMAINING 70% CONTINUE WITH A DRY NORTHWEST FLOW
ALOFT AND LITTLE TO NO PRECIPITATION CHANCES ACROSS THE FORECAST
AREA. SUNDAY THROUGH MONDAY, ENSEMBLE CLUSTER SOLUTIONS ARE IN
MUCH BETTER AGREEMENT WITH EACH SOLUTION DEPICTING AN UPPER RIDGE
DEVELOPING AND A DRY, COLD NORTHERLY FLOW ALOFT PARKED OVER THE
PACNW BY SUNDAY NIGHT (CONFIDENCE 40-75%). THE ENSEMBLE CLUSTER
SOLUTIONS THEN DEPICT THE RIDGE FLATTENING BEGINNING LATE MONDAY,
FOLLOWED BY A SHORTWAVE TROUGH DIVING ACROSS THE FORECAST AREA BY
TUESDAY MORNING, THOUGH SOLUTIONS DIVERGE ON STRENGTH AND HOW COLD
THE SYSTEM WILL BE. OF THE SOLUTIONS, ONE CONTAINING ABOUT 25% OF
MEMBERS FAVORS A COLDER SOLUTION THAT WOULD RESULT IN LIGHT SNOW
ALONG THE NORTHERN BLUE MOUNTAIN FOOTHILLS AND EASTERN PORTIONS
OF THE COLUMBIA BASIN TUESDAY MORNING. LAWHORN/82
AVIATION...00Z TAFS
PRECIP IS STARTING TO MOVE INTO THE FORECAST
AREA, AND IS EXPECTED TO REACH YKM BY THE START OF THE PERIOD,
SPREADING TO DLS, PSC, PDT, AND ALW BY 05Z AT THE LATEST. ALL SITES
ARE EXPECTED TO RECEIVE RAIN, HOWEVER SNOW MAY MIX IN AT TIMES FOR
YKM HEADING INTO THE OVERNIGHT HOURS. EXPECT IFR OR WORSE CONDITIONS
TO OCCUR UNDER PRECIP DUE TO DEGRADED VSBYS AND LOW CIGS. THE
COMBINATION OF LIGHT WINDS AND RECENT MOISTURE IS EXPECTED TO MAKE
FOR LOW CLOUDS HEADING INTO EARLY WEDNESDAY MORNING FOR THE
AFOREMENTIONED SITES, MAKING FOR AT LEAST MVFR CONDITIONS, HOWEVER
CONFIDENCE WITH REGARDS TO TIMING AND EXTENT REMAIN LIMITED. BY
EARLY WEDNESDAY AFTERNOON, ANOTHER ROUND OF RAIN IS EXPECTED TO
OCCUR AT ALL SITES EXCEPT FOR BDN/RDM, HOWEVER THIS ROUND IS
EXPECTED TO BE LIGHTER THAN THE ONE OCCURRING THIS EVENING.
OVERALL FORECAST CONFIDENCE IS 90-100% FOR PRECIP AT ALL SITES
OUTSIDE OF BDN/RDM, 70-80% FOR IFR OR WORSE CONDITIONS AT THE
AFOREMENTIONED SITES THIS EVENING AND OVERNIGHT, AND 40-50% FOR LOW
CIGS MAKING FOR MVFR OR WORSE CONDITIONS EARLY WEDNESDAY MORNING,
AGAIN FOR THE AFOREMENTIONED SITES WHERE PRECIP IS MOST LIKELY TO
OCCUR. 74
PRELIMINARY POINT TEMPS/POPS
PDT 36 50 35 47 / 90 50 50 50
ALW 38 48 38 46 / 100 50 70 60
PSC 34 46 36 45 / 90 20 50 60
YKM 31 45 35 44 / 80 10 60 70
HRI 35 48 36 45 / 80 30 50 50
ELN 28 42 33 41 / 100 10 70 90
RDM 34 55 27 54 / 30 30 10 20
LGD 34 46 34 50 / 90 70 50 40
GCD 36 50 34 55 / 60 40 20 20
DLS 39 49 41 47 / 80 60 70 80
PDT WATCHES/WARNINGS/ADVISORIES
OR...NONE.
WA...WINTER WEATHER ADVISORY UNTIL 4 AM PST WEDNESDAY FOR WAZ026-522-
523.
DISCUSSION...82
AVIATION...74
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