454
FXUS66 KPDT 092219
AFDPDT
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE PENDLETON OR
219 PM PST SUN NOV 9 2025
UPDATED AVIATION DISCUSSION
DISCUSSION
KEY MESSAGES:
1. BREEZY WINDS TODAY THROUGH MONDAY MORNING.
2. MOUNTAIN SHOWERS MONDAY, WIDESPREAD LATE WEDNESDAY.
3. PASS LEVEL SNOWFALL THURSDAY THROUGH SATURDAY.
HIGH PRESSURE CONTINUES TO INFLUENCE THE WEATHER ACROSS THE
INTERIOR NORTHWEST THIS AFTERNOON. WINDY CONDITIONS ARE PERSISTING
ACROSS THE GRANDE RONDE VALLEY AS GUSTS MAY OCCASIONALLY HIT
AROUND 35 MPH THIS AFTERNOON, AND GIVEN THE VALUES OF THE PRESSURE
GRADIENT (5-6 MB AVERAGING BETWEEN NBM AND THE SREF) ACROSS THE
BAKER TO MEACHAM AREAS, THE VALUES UPTICK TO AROUND 6 MB
DIFFERENTIAL BY THE OVERNIGHT, KEEPING WINDS STRONG THROUGH MONDAY
MORNING. AN UPPER LEVEL RIDGE AT 500 MPH WILL SLIDE EAST TONIGHT,
ALLOWING A RETURN TO MORE ZONAL FLOW ALOFT ACROSS THE AREA FOR
VETERANS DAY AND TUESDAY. THE PATTERN WILL PROMOTE DRY,CONDITIONS,
MILD TEMPERATURES IN THE 50S AND 60S. SOME INSTABILITY/OROGRAPHIC
LIFTED SHOWERS CAN OCCUR ALONG THE CASCADE CREST MONDAY, HOWEVER
THE REAL UPTICK IN RAIN AND SNOW CHANCES DOES NOT BEGIN UNTIL
ABOUT MIDWEEK WHEN THE INITIAL MOISTURE ADVECTION ASSOCIATED WITH
THE NEXT ATMOSPHERIC RIVER IS REALIZED. TIMING OF BEST MOISTURE
TRANSPORT IN OVERNIGHT WEDNESDAY THROUGH THE DAY THURSDAY. SNOW
LEVELS REMAIN QUITE HIGH AT AROUND 6,000 FT OR HIGHER THROUGH
ABOUT THURSDAY AFTERNOON BEFORE CRASHING THURSDAY NIGHT AND
FALLING TO AROUND 4000 FT OR LESS BY EARLY FRIDAY MORNING ACROSS
THE CASCADES. NBM SNOW TOTALS FOR THE THURSDAY TO SATURDAY PERIOD
DO SHOW POTENTIAL FOR ADVISORY LEVEL SNOW AMOUNTS AT SANTIAM AND
WHITE PASS AREAS (AS MUCH AS 6 INCHES, ABOUT A 50% CHANCE BY
SUNDAY MORNING) AND LESS AT CONSIDERABLY LESS SNOQUALMIE PASS. THE
WARMER REGIME WOULD ALSO IMPLY A WET SNOW AS THE NBM SNOW RATIOS
ARE ONLY AROUND 8-9:1 OVER MOST OF THIS FORECAST ZONE. WSSI -P
(PROBABILISTIC WINTER STORM SEVERITY INDEX) GIVES A 40% CHANCE FOR
MINOR IMPACTS ALONG THE HIGHWAY 12 SECTION NEAR WHITE PASS AND
HIGHWAY 20 SECTIONS NEAR SANTIAM ON THURSDAY, ATTRIBUTABLE TO
SNOW LOAD AND SNOW AMOUNT A LESSER DEGREE. RUSSELL/71
AVIATION...00Z TAFS
VFR CONDITIONS EXPECTED THROUGH THE
PERIOD. A WEAK SYSTEM MOVING INTO THE REGION TONIGHT WILL KEEP
CHANCES OF FOG LOW (<15%) ACROSS MUCH OF THE AREA, WITH ABOUT A
15-30% CHANCE OF MVFR CIGS DEVELOPING AT SITE DLS, WITH LESS THAN
15% CHANCE ELSEWHERE. OTHERWISE, CIGS WILL GENERALLY REMAIN ABOVE
15KFT AGL THROUGH TOMORROW MORNING, WITH SCT-BKN CIGS BETWEEN 6KFT
TO 12KFT AGL AT SITES DLS/PDT/YKM/ALW/PSC. WINDS WILL BE LIGHT,
12KTS OR LESS, THROUGH THE PERIOD. LAWHORN/82
PRELIMINARY POINT TEMPS/POPS
PDT 37 62 40 56 / 0 10 10 0
ALW 42 61 43 56 / 0 10 20 0
PSC 36 57 35 53 / 0 10 0 0
YKM 37 57 32 55 / 0 10 0 0
HRI 37 59 39 55 / 0 10 0 0
ELN 34 57 33 52 / 0 20 0 0
RDM 36 65 34 62 / 0 0 0 0
LGD 42 62 41 61 / 0 0 10 0
GCD 39 66 37 65 / 0 0 0 0
DLS 42 61 41 57 / 0 20 10 0
PDT WATCHES/WARNINGS/ADVISORIES
OR...NONE.
WA...NONE.
DISCUSSION...71
AVIATION...82
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