200
FXUS66 KPDT 221820
AFDPDT
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE PENDLETON OR
1020 AM PST SAT NOV 22 2025
MORNING UPDATE
FOG AND LOW STRATUS REMAINS ENTRENCHED IN THE
COLUMBIA BASIN AND GORGE, AS WELL AS SURROUNDING LOW-LYING AREAS
THIS MORNING. VISIBILITIES OF ONE-QUARTER MILE OR LESS HAVE BEEN
OBSERVED INTO THE LOWER YAKIMA VALLEY, SO OPTED TO EXPAND THE
EXISTING DENSE FOG ADVISORY TO INCLUDE OUR YAKIMA VALLEY FORECAST
ZONE. ANTICIPATING WIDESPREAD DENSE FOG WILL LIFT THROUGH MORNING,
WITH SOME AREAS OF FOG AND STRATUS LINGERING INTO THE EARLY
AFTERNOON HOURS.
PREV DISCUSSION
/ISSUED 300 AM PST SAT NOV 22 2025/
DISCUSSION...A 1028 MB SURFACE HIGH PRESSURE WAS CENTERED OVER
EASTERN OREGON THIS MORNING. FOG WAS PRESENT ON A NUMBER OF METAR
AND ROAD CAMS ACROSS THE TRI-CITIES AREA WITH AN HREF SIGNAL FOR
DENSE FOG/LOW VISIBILITY SNOWING UP WITH A 25-50% CHANCE FOR LESS
THAN ONE QUARTER MILE THROUGH AT LEAST 17Z, FOCUSED THROUGHOUT
THE RIVER BASIN. A DENSE FOG ADVISORY WILL REMAIN IN EFFECT FOR
FRANKLIN AND BENTON COUNTIES IN WA THROUGH 10 AM. LIGHT WINDS
TODAY WILL GIVE WAY TO INCREASINGLY BREEZY SOUTHWESTERLY SURFACE
WINDS FOR SUNDAY AS THE HIGH PRESSURE MOVES AWAY, PRESSURE FALLS
AND A COLD FRONT APPROACHES THE AREA FROM BE PAC NW FOR LATE
SUNDAY AND SUNDAY NIGHT. FROM THE STANDPOINT OF THE EFI, NOTHING
STANDS OUT AS PARTICULARLY STRONG WITH THESE EPISODES THIS WEEK,
AS THE NAEFS STANDARDIZED ANOMALIES ARE ONLY AROUND 1 TO 1.5 FOR
ANY GIVEN WEATHER ELEMENT. HAVING SAID THAT, STILL, PASS LEVEL
SNOW POSSIBLE SUNDAY AND WEDNESDAY. FOR SNOQUALMIE, AROUND 4
INCHES BASED ON THE NBM FOR THE ENTIRE DURATION (BELOW ADVISORY
CRITERIA) FOR EACH OF THE TWO SEPARATE PRECIPITATION EPISODES.
PROBABILISTIC WINTER STORM SEVERITY INDEX BRINGS OUT LITTLE TO NO
CHANCE FOR MODERATE IMPACTS DUE TO SNOW LOAD ON SUNDAY, HOWEVER
DOES INCREASE THIS TO ABOUT A 20-30% CHANCE AT THE PASS BY
WEDNESDAY AFTERNOON (DIFFERENTIATED BY MINOR IMPACTS BY CLOSURES
AND DISRUPTIONS TO INFRASTRUCTURE POSSIBLE). A SIMILAR SNOW IMPACT
MIGHT BE FOUND AT WHITE PASS, AS THESE WILL BE WET SNOWS WITH LOW
SNOW TO LIQUID RATIOS (AROUND 8:1). BREEZIEST CONDITIONS FOR THE
WEEK LOOK TO BE IN THE POST FRONTAL ENVIRONMENT SUNDAY NIGHT INTO
MONDAY AS WESTERLY SURFACE GUSTS ARE BEING PRODUCED BY THE NBM
MEAN AROUND 25 TO 35 KNOTS WHICH IS PUSHING 30 TO 40 MPH ACROSS
THE EASTERN COLUMBIA RIVER GORGE, SIMCOE HIGHLANDS AND NORTHERN
BLUES MOUNTAINS, AS WELL AS MUCH OF THE OREGON COLUMBIA BASIN.
AVIATION...18Z TAFS
FOG AND LOW STRATUS REMAINS ENTRENCHED IN
THE COLUMBIA BASIN AND GORGE, AS WELL AS SURROUNDING LOW-LYING
AREAS SUCH AS THE YAKIMA AND WALLA WALLA VALLEYS, LEADING TO
VLIFR TO IFR VSBYS/CIGS AT PSC/ALW/YKM/DLS. ELSEWHERE, MOSTLY
CLEAR SKIES ARE PRESENT AT RDM/BDN/PDT. ANTICIPATING WIDESPREAD
DENSE FOG WILL LIFT THROUGH MORNING, WITH SOME AREAS OF FOG AND
STRATUS LINGERING INTO THE EARLY AFTERNOON HOURS.
MID- TO HIGH-LEVEL CLOUD COVER WILL BECOME MORE BKN-OVC TONIGHT
THROUGH SUNDAY AS A PACIFIC COLD FRONT APPROACHES THE REGION.
CONFIDENCE IN THE RETURN OF WIDESPREAD FOG AND STRATUS IS LOW-
MEDIUM (20-50 PERCENT, VARYING BY SITE) FOR BASIN SITES AS
FORECAST SOUNDINGS SHOW THE TEMPERATURE INVERSION PERSISTING.
SUSTAINED WINDS OF 10 KTS OR LESS ARE FORECAST FOR ALL SITES
THROUGH THE NEXT 24 HOURS.
PRELIMINARY POINT TEMPS/POPS
PDT 51 34 52 32 / 0 0 20 70
ALW 50 39 53 34 / 0 0 40 80
PSC 47 33 51 32 / 0 0 20 40
YKM 49 35 50 26 / 0 10 30 20
HRI 47 34 52 34 / 0 0 20 50
ELN 47 34 47 29 / 0 20 50 30
RDM 57 28 54 23 / 0 0 20 40
LGD 53 35 52 29 / 0 0 20 90
GCD 55 31 56 28 / 0 0 10 60
DLS 52 39 52 37 / 0 10 60 50
PDT WATCHES/WARNINGS/ADVISORIES
OR...DENSE FOG ADVISORY UNTIL 11 AM PST THIS MORNING FOR ORZ044-507.
WA...DENSE FOG ADVISORY UNTIL 11 AM PST THIS MORNING FOR WAZ027>029.
MORNING UPDATE...86
DISCUSSION...71
AVIATION...86
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