373
FXUS66 KSEW 202036
AFDSEW
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SEATTLE WA
136 PM PDT SUN SEP 20 2026
SYNOPSIS
AN UPPER RIDGE REMAINS IN PLACE ACROSS THE PACIFIC
NORTHWEST THROUGH TONIGHT. THE RIDGE FLATTENS MONDAY INTO
TUESDAY AS A FRONTAL SYSTEM TRACKS INTO BRITISH COLUMBIA. DEEPER
TROUGHING DEVELOPS LATER THURSDAY INTO FRIDAY FOR MORE
WIDESPREAD PRECIPITATION POTENTIAL.
SHORT TERM /TONIGHT THROUGH TUESDAY NIGHT/
MOSTLY SUNNY SKIES
THIS AFTERNOON WITH LINGERING STRATUS CLEARING ACROSS PORTIONS
OF SOUTHWEST WASHINGTON. DRY CONDITIONS THROUGH TONIGHT WITH AN
UPPER RIDGE OVER THE PACIFIC NORTHWEST. TEMPERATURES PEAKING IN
THE 60S TO LOW 70S TODAY.
ANOTHER ROUND OF STRATUS IS EXPECTED MONDAY MORNING ACROSS
WESTERN WASHINGTON, CLEARING FOR SOME AFTERNOON SUNSHINE. THE
UPPER RIDGE ALSO SHIFTS EASTWARDS ON MONDAY AS A FRONTAL SYSTEM
MOVES INTO BRITISH COLUMBIA. THIS WILL RESULT IN INCREASED
ONSHORE FLOW LATE MONDAY INTO TUESDAY FOR ADDITIONAL CLOUDS.
TEMPERATURES MONDAY AND TUESDAY WILL PEAK IN THE 60S TO LOW
70S.
LONG TERM /WEDNESDAY THROUGH SUNDAY/
A WEAKENING FRONTAL
SYSTEM BRUSHES THE AREA LATE TUESDAY NIGHT THROUGH WEDNESDAY,
BRINGING SLIGHT POPS TO NORTHERN PORTIONS OF THE OLYMPIC
PENINSULA AND SKAGIT COUNTY NORTHWARDS. TROUGHING DEEPENS
OFFSHORE THURSDAY AS A MORE ORGANIZED SYSTEM APPROACHES THE
PACIFIC NORTHWEST. ENSEMBLES ARE CONSISTENT IN TROUGHING
OVERHEAD INTO FRIDAY, ALTHOUGH SOME UNCERTAINTY REMAINS INTO THE
DEPTH OF THE TROUGH. EITHER WAY, MORE WIDESPREAD PRECIPITATION
POTENTIAL EXISTS THURSDAY NIGHT INTO FRIDAY ASSOCIATED WITH THE
FRONTAL SYSTEM MOVING ACROSS THE PACIFIC NORTHWEST. SNOW LEVELS
DURING THIS PERIOD RANGE 6500 TO 8000 FEET RESULTING IN HIGH
ELEVATION MOUNTAIN SNOWFALL. ENSEMBLES SUGGEST A WEAK TROUGHING
TO ZONAL FLOW SIGNAL BY NEXT WEEKEND, WITH PREDOMINANTLY DRIER
CONDITIONS AND COOLER TEMPERATURES. JD
AVIATION
MARINE STRATUS CONTINUES TO ERODE, WITH ONLY PORTIONS OF
SOUTHWESTERN WASHINGTON STILL HOLDING ONTO SOME OF IT. WIDESPREAD
VFR CONDITIONS ARE EXPECTED TO CONTINUE THROUGHOUT THE AFTERNOON
WITH LIGHT NORTHERLY SURFACE WINDS. ANOTHER ROUND OF MARINE STRATUS
CLOUDS IS FORECAST TO ARRIVE LATE TONIGHT INTO EARLY MONDAY MORNING,
BUT LOOKS TO PRIMARILY IMPACT COASTAL TERMINALS, GETTING AS FAR IN
AS KPWT AND KOLM. PATCHY LOW CIGS ARE POSSIBLE FOR THE REST OF THE
PUGET SOUND TERMINALS TOMORROW MORNING, GENERALLY AFTER 12Z, BUT THE
PROBABILITIES FOR MVFR (40%) ARE FAVORED FOR THIS AREA.
PROBABILITIES OF IFR CIGS ALONG THE COAST AND WESTERN PUGET
SOUND AREA ARE FAVORED (60% OR MORE). SURFACE WINDS ARE EXPECTED
TO BECOME MORE SOUTHWESTERLY FOR MUCH OF THE AREA AFTER 12Z
TOMORROW MORNING AT 3-6 KTS.
KSEA...VFR CONDITIONS CONTINUE THIS AFTERNOON WITH NORTHERLY WINDS 6-
8 KTS. CLEAR SKIES ARE FORECAST OVERNIGHT. THE MARINE STRATUS ISN'T
FAVORED TO REACH THE TERMINAL TOMORROW MORNING, BUT THE TAF WILL
INDICATE SOME LOWER CLOUDS (NOT A CEILING AT THIS TIME) AFTER 12Z.
AREAS WEST AND SOUTH OF THE TERMINAL WILL HAVE A HIGHER LIKELIHOOD
OF SEEING LOWER CIGS. SURFACE WINDS WILL BECOME MORE SOUTH TO
SOUTHWESTERLY AFTER 12Z, CONTINUING INTO TOMORROW AFTERNOON AT 5-8
KTS.
21
MARINE
HIGH PRESSURE WILL PERSIST OVER THE OFFSHORE WATERS
INTO MONDAY. A WEAK FRONT MOVES INTO BRITISH COLUMBIA LATER
MONDAY INTO TUESDAY, RESULTING IN INCREASED ONSHORE FLOW.
PROBABILITIES FOR SMALL CRAFT ADVISORY WEST WIND GUSTS RANGE
BETWEEN 70 TO 90% MONDAY NIGHT FOR THE CENTRAL AND EASTERN
STRAIT OF JUAN DE FUCA, AND FOR THIS REASON ISSUED A SCA FOR
THESE AREAS. ANOTHER WESTERLY PUSH IS EXPECTED TUESDAY NIGHT,
BUT AT THIS TIME THE STRONGER WINDS ARE CONFINED TO THE CANADIAN
SIDE OF THE STRAIT. A WEAKENING FRONT THEN MOVES ACROSS THE
WATERS ON WEDNESDAY, WITH ANOTHER WEATHER SYSTEM LATE THURSDAY
INTO FRIDAY.
SEAS OF 3 TO 5 FEET THROUGH MONDAY MORNING WILL BUILD TO 7 TO 9
FEET MONDAY NIGHT AS A LONGER PERIOD NORTHWESTERLY SWELL ARRIVES
ACROSS THE COASTAL WATERS. BRIEF 10 FOOT SEAS MAY OCCUR OVER THE
OUTER COASTAL WATERS MONDAY NIGHT. SEAS THEN SUBSIDE TO 6 TO 8
FEET TUESDAY AFTERNOON THROUGH FRIDAY. JD
SEW WATCHES/WARNINGS/ADVISORIES
WA...NONE.
PZ...SMALL CRAFT ADVISORY FROM 3 PM MONDAY TO MIDNIGHT PDT MONDAY
NIGHT FOR CENTRAL U.S. WATERS STRAIT OF JUAN DE FUCA-EAST
ENTRANCE U.S. WATERS STRAIT OF JUAN DE FUCA.
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