621
FXUS66 KPDT 090535
AFDPDT
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE PENDLETON OR
935 PM PST SAT NOV 8 2025
UPDATED FOR AVIATION
AVIATION
06Z TAFS...VFR CONDITIONS ARE EXPECTED THROUGH THE TAF PERIOD FOR
THE MOST PART, WITH WINDS 10 KTS OR LESS. WITH HIGH PRESSURE IN
PLACE OVER THE AREA, SOME FOG OR STRATUS IS POSSIBLE, WITH THE
MOST LIKELY LOCATION BEING DLS. IFR CIGS ARE BEING FORECAST THERE
SUNDAY MORNING. IT IS POSSIBLE THAT THERE COULD BE FOG OR STRATUS
IN OTHER LOCATIONS AS WELL (LIKE PSC) BUT PROBABILITIES ARE LOW
ENOUGH (<30 PERCENT) SO HAVE NOT INCLUDED ANY LOWER CIGS/VSBYS AT
THIS TIME.
PREV DISCUSSION
/ISSUED 205 PM PST SAT NOV 8 2025/
DISCUSSION...TODAY THROUGH WEDNESDAY MORNING: A RIDGE OF HIGH
PRESSURE WILL CONTINUE TO BUILD OVER THE PACNW TODAY, WITH
SCATTERED CIRRUS DECKS PUSHING OVER THE FORECAST AREA THROUGHOUT
TODAY AND INTO TOMORROW. TEMPERATURES WILL MODERATE UNDER A
STRENGTHENING LOW LEVEL INVERSION ACROSS THE COLUMBIA BASIN AND
ADJACENT VALLEYS/FOOTHILLS (INCLUDING NORTH CENTRAL OR) THROUGH
SUNDAY, KEEPING TEMPERATES MAINLY IN THE 50S, WHILE TEMPERATURES
WARM INTO THE 60S TO LOW 70S ELSEWHERE.
THE RIDGE WILL FLATTEN SUNDAY NIGHT THROUGH MONDAY AS A SHORTWAVE
TROUGH AND A DETERIORATING COLD FRONT IMPACT THE PACNW. MOISTURE
WILL LIMITED WITH THIS SYSTEM, ONLY RESULTING IN LIGHT
PRECIPITATION ALONG THE CASCADE CREST AND NORTHERN BLUES, WITH
LIGHT SNOW LIMITED TO ABOVE 7.5KFT ALONG THE CASCADE CREST. PRESSURE
GRADIENTS ACROSS THE BLUES WILL TIGHTEN AHEAD OF THE SYSTEM
ARRIVAL SUNDAY MORNING, AND REMAIN WILL STRENGTHENED UNTIL THE
SHORTWAVE/FRONT PASSAGE MONDAY MORNING. IN RESPONSE, BREEZY SOUTH
WINDS 15-25MPH AND GUSTS UP TO 40MPH WILL DEVELOP THROUGH THE
GRANDE RONDE VALLEY, WITH ONLY A 10-20% CHANCE THAT WINDS 45MPH OR
GREATER WILL DEVELOP. BREEZY SOUTH TO SOUTHWEST WINDS WILL ALSO
DEVELOP OVER THE BLUE MOUNTAINS, WHICH WILL TRANSITION INTO
DOWNSLOPE WINDS ALONG THE BLUE MOUNTAIN FOOTHILLS BY MONDAY. THERE
IS MODERATE CONFIDENCE (50-70%) THAT THE DOWNSLOPING WINDS WILL
ALSO ERODE AWAY THE LOW LEVEL INVERSION AND COLD POOL ALONG THE
FOOTHILLS, ALLOWING FOR TEMPERATURES TO WARM INTO THE 60S IN THESE
AREAS. THE RIDGE WILL REBOUND BACK LATE MONDAY THROUGH WEDNESDAY
MORNING WITH LIGHT WINDS AND DRY CONDITIONS.
FOG AND LOW STRATUS DEVELOPING IN THE OVERNIGHT HOURS AND EARLY
MORNINGS WILL BECOME A CONCERN THROUGH EARLY IN THE WEEK,
ESPECIALLY IN AREAS OF THE COLUMBIA RIVER GORGE, AND BLUE
MOUNTAIN FOOTHILLS, AND YAKIMA/KITTITAS VALLEYS. CURRENTLY,
PROBABILITIES FOR LOW STRATUS TO DEVELOP ARE ONLY 20-30% THROUGH
MONDAY MORNING, BUT RISE TO 35-55% BY TUESDAY MORNING. AS FOR
PATCHY FOG, CHANCES WILL GENERALLY REMAIN LESS THAN 20%, BUT
CONFIDENCE IS MODERATE (50-70%) THAT PATCHY FOG WILL DEVELOP ALONG
SOME AREAS OF THE COLUMBIA/SNAKE RIVERS AS WELL AS ALONG SOME
THEIR TRIBUTARY RIVERS.
WEDNESDAY AFTERNOON THROUGH FRIDAY: ENSEMBLE GUIDANCE IS IN GREAT
AGREEMENT THAT A TROUGH WILL DEVELOP OFFSHORE THE PACNW BY
WEDNESDAY MORNING, BUT ENSEMBLE CLUSTER SOLUTIONS DISAGREE ON
TIMING AND SNOW COVERAGE IN THE MOUNTAINS. ACROSS THE AVAILABLE
SOLUTIONS, THE TROUGH AXIS PASSAGE OVER THE FORECAST AREA RANGES
ANYWHERE FROM THURSDAY NIGHT THROUGH FRIDAY EVENING. SOLUTIONS
THAT HAVE AN EARLIER PASSAGE FRIDAY MORNING ALSO RESULT IN
PRECIPITATION CHANCES ACROSS THE LOWER ELEVATIONS DIMINISHING
BEFORE FRIDAY AFTERNOON (~55% OF MEMBERS) WHILE OTHER SOLUTIONS
(~30% OF MEMBERS) DEPICT THE TROUGH AXIS PASSAGE LATER FRIDAY,
RESULTING IN PRECIPITATION CHANCES STAYING AROUND LONGER. THE
EARLIER PASSAGE SOLUTIONS ALSO DEPICT THE LOWEST SNOW LEVELS
ACROSS THE MOUNTAINS, RESULTING IN LIGHT SNOW ACCUMULATIONS NOT
ONLY ACROSS THE CASCADE CREST, BUT ACROSS PORTIONS OF THE EASTERN
MOUNTAINS AS WELL. FROM THE NBM, 72 HOUR CHANCES OF SNOW GREATER
THAN 4 INCHES THROUGH FRIDAY NIGHT IS ONLY 25-50% ACROSS THE EAGLE
CAPS AND THE CASCADE PASSES; CHANCES ARE GENERALLY 10-30% ACROSS
THE EASTERN MOUNTAINS AND THE BLUES. OTHERWISE, THERE IS MOD-HIGH
CONFIDENCE (60-80%) THAT THE LOWER ELEVATIONS AND MID ELEVATION
AREAS OF THE EASTERN MOUNTAINS WILL SEE AT LEAST LIGHT RAINFALL
THROUGH THE LATTER HALF OF THE WORK WEEK, THOUGH CONFIDENCE IS LOW
(15-25%) IN TIMING OF BEGINNING/ENDING OF RAINFALL AND AMOUNT OF
PRECIPITATION AREAS WILL RECEIVE. LASTLY, CONFIDENCE IS MODERATE
(60-70%) THAT BREEZY SOUTH TO WEST WINDS (15-25MPH WITH GUSTS
25-40MPH) WILL DEVELOP ACROSS THE FORECAST AREA WITH THE PASSAGE
OF THE TROUGH LATE WEDNESDAY THROUGH FRIDAY. LAWHORN/82
AVIATION...00Z...SURFACE HIGH PRESSURE WILL CONTINUE TO DOMINATE
SENSIBLE WEATHER. VFR CONDITIONS ARE EXPECTED WITH LIGHT WINDS
PREVAILING. ONE CONCERN HOWEVER WILL BE THE POTENTIAL FOR STRATUS
TO DEVELOP AGAIN OVERNIGHT IN THE BASIN OVER KDLS. AS LOCALLY EAST
SURFACE WINDS (NEAR AND AROUND DLS) CONTINUE THROUGH 12Z AND
BEYOND SUNDAY MORNING THE REDEVELOPMENT OF THE IFR RESTRICTION
SHOULD BE CONSIDERED AT LEAST A 50% CHANCE, ESPECIALLY GIVEN THE
POOR MODEL PREDICTION AS OF LATE.
PRELIMINARY POINT TEMPS/POPS
PDT 34 54 37 61 / 0 0 0 0
ALW 37 54 41 60 / 0 0 0 10
PSC 32 53 34 56 / 0 0 0 0
YKM 33 55 37 59 / 0 0 0 0
HRI 34 52 36 59 / 0 0 0 0
ELN 31 53 35 57 / 0 0 0 10
RDM 30 66 35 67 / 0 0 0 0
LGD 35 61 42 63 / 0 0 0 0
GCD 35 66 38 67 / 0 0 0 0
DLS 38 56 41 62 / 0 0 0 10
PDT WATCHES/WARNINGS/ADVISORIES
OR...NONE.
WA...NONE.
SHORT TERM...82
LONG TERM....82
AVIATION...77
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