935
FXUS66 KSEW 212227
AFDSEW
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SEATTLE WA
327 PM PDT TUE OCT 21 2025
SYNOPSIS
A WEAK FRONTAL SYSTEM WILL MOVE ACROSS WESTERN
WASHINGTON ON WEDNESDAY. A DEEP UPPER TROUGH WILL APPROACH FROM
OFFSHORE THURSDAY AND FRIDAY AS A STRONGER SYSTEM SLIDES THROUGH
FOR HEAVIER PRECIPITATION AND INCREASING WINDS. UNSETTLED
WEATHER THEN CONTINUES OVER THE WEEKEND WITH UPPER TROUGHING
OVER THE PACIFIC NORTHWEST.
SHORT TERM /TONIGHT THROUGH THURSDAY NIGHT/
A MIX OF CLOUDS
AND SUNSHINE THIS AFTERNOON WITH BRIEF RIDGING BUILDING INTO THE
PACIFIC NORTHWEST. TEMPERATURES WILL PEAK IN THE UPPER 50S TO
MID 60S THIS AFTERNOON. ALTHOUGH HIGH CLOUDS WILL INCREASE
TONIGHT INTO WEDNESDAY MORNING, SOME CLEARING AND LIGHT WINDS
WILL PROMOTE FOG DEVELOPMENT, PARTICULARLY AROUND SOUTHERN PUGET
SOUND, AND IN RIVER VALLEYS TOWARDS HOQUIAM. OFFSHORE FLOW
EXPECTED OTHERWISE INTO EARLY WEDNESDAY.
A WEAK FRONTAL SYSTEM WILL MOVE ACROSS WESTERN WASHINGTON ON
WEDNESDAY, RESULTING IN INCREASING LIGHT RAIN DURING THE DAY.
LOCALIZED BREEZY WINDS ARE ALSO EXPECTED, PRIMARILY ALONG THE
COAST, AND IN AREAS AROUND WHIDBEY ISLAND. OTHERWISE,
TEMPERATURES WILL ONCE AGAIN PEAK IN THE LOW TO MID 60S WITH
SOME RIDGING INFLUENCE REMAINING WEDNESDAY.
TROUGHING WILL THEN DEEPEN OVER THE NE PACIFIC BEGINNING
THURSDAY AS A STRONGER FRONT APPROACHES WESTERN WASHINGTON. RAIN
WILL MOVE ONSHORE THURSDAY ACROSS THE OLYMPIC PENINSULA, WITH
PREDOMINANTLY DRIER CONDITIONS THROUGH THURSDAY AFTERNOON FOR
AREAS PUGET SOUND EASTWARDS. THE COLD FRONT WILL PROGRESS ACROSS
THE AREA THURSDAY NIGHT INTO FRIDAY, DURING WHICH THE HEAVIEST
PRECIPITATION IS EXPECTED. SOUTHERLY WINDS WILL LIKELY BE THE
MORE NOTICEABLE WEATHER FACTOR ON THURSDAY AS WINDS INCREASE.
WINDS WILL BE STRONGEST THURSDAY AFTERNOON THROUGH THURSDAY
NIGHT ALONG THE COAST, AS WELL AS NORTH OF EVERETT. FORECAST
WIND GUSTS ARE EXPECTED TO RANGE 30 TO 50 MPH FOR THESE
AFOREMENTIONED AREAS, WITH THE PROBABILITIES OF GUSTS ABOVE 50
MPH PEAKING BETWEEN 30-60% FOR THE NORTH COAST, WHIDBEY ISLAND,
AND WESTERN WHATCOM COUNTY. WILL NEED TO MONITOR THESE AREAS FOR
POTENTIAL HEADLINES OVER THE NEXT FEW DAYS. BREEZY CONDITIONS
ELSEWHERE WITH THE FRONTAL SYSTEM LATE THURSDAY INTO EARLY
FRIDAY.
LONG TERM /FRIDAY THROUGH TUESDAY/
THE AFOREMENTIONED COLD
FRONT WILL CONTINUE TO MOVE ACROSS WESTERN WASHINGTON ON FRIDAY,
WITH RAIN RATES PEAKING LATE THURSDAY NIGHT INTO FRIDAY
AFTERNOON. ELEVATED RAINFALL RATES MAY RESULT IN LOCALIZED URBAN
OR SMALL STREAM FLOODING IN AREAS OF POOR OR BLOCKED DRAINAGE ON
FRIDAY. OTHERWISE, WINDS WILL REMAIN BREEZY LATE FRIDAY INTO
FRIDAY NIGHT. ADDITIONAL DISTURBANCES EMBEDDED IN THE UPPER
TROUGH OFFSHORE ARE EXPECTED TO BRING CONTINUED UNSETTLED
WEATHER OVER THE WEEKEND FOR PERIODS OF BREEZY WINDS, AND
LOWLAND RAIN. SOME UNCERTAINTY REMAINS IN ENSEMBLES IN REGARDS
TO THE TRACK OF THESE ADDITIONAL SYSTEMS. UPPER TROUGHING THEN
LOOKS TO LINGER OVER THE PACIFIC NORTHWEST EARLY NEXT WEEK FOR
ADDITIONAL SHOWERS, ALTHOUGH PRECIPITATION LOOKS TO LIGHTEN FOR
MOST AREAS ON MONDAY.
MOUNTAIN SNOW WILL ALSO BECOME MORE IMPACTFUL OVER THE WEEKEND
INTO EARLY NEXT WEEK WITH THE UPPER TROUGH POSITIONED OVER THE
AREA. SNOW LEVELS WILL INITIALLY RANGE AROUND 6000-6500 FEET ON
FRIDAY BEFORE FALLING TO 4000 FEET BY SATURDAY MORNING. SNOW
LEVELS THEN WILL FALL FURTHER TOWARDS 3000 FEET SUNDAY INTO
MONDAY. COOLER TEMPERATURES ALOFT, COMBINED WITH CONTINUED
PRECIPITATION, WILL RESULT IN PERIODS OF MODERATE TO HEAVY SNOW
FOR THE CASCADES AND OLYMPICS. LATEST 72 HOUR PROBABILITIES
(THRU MONDAY PM) FROM THE NBM HIGHLIGHTS A 60-80% CHANCE OF 12
INCHES OF SNOW FOR STEVENS AND WHITE PASS, WITH LESS
PROBABILITIES AROUND 20% FOR SNOQUALMIE PASS. IF YOU'RE
TRAVELING OVER THE CASCADE PASSES SATURDAY THROUGH EARLY NEXT
WEEK, CONTINUE TO MONITOR THE FORECAST. JD
AVIATION
A WEAK RIDGE WILL AMPLIFY TONIGHT INTO EARLY WEDNESDAY,
PASSING EAST OF THE CASCADES AS A TROUGH APPROACHES WITH A WEAK
FRONTAL SYSTEM LATE WEDNESDAY. THE FLOW WILL BECOME VERY LIGHT ALOFT
AS THE ZONAL FLOW WEAKENS, THEN SWITCH TO THE SOUTHWEST TOMORROW.
MOST TERMINALS THIS AFTERNOON ARE REPORTING VFR, ALTHOUGH A COUPLE
SMALLER GROUPS OF MVFR CIGS WILL LINGER THROUGH LATE THIS AFTERNOON
ALONG THE NORTHWEST COAST AND FAR NORTHERN INTERIOR WATERS. LIGHT
NORTH WINDS 4-6 KT THIS AFTERNOON WILL BECOME NORTHEAST LESS THAN 5
KT OR LIGHT AND VARIABLE TONIGHT. FOG TOMORROW REMAINS LIKELY IN
SOUTH INTERIOR/KITSAP TERMINALS IN THE MORNING (OUT TO THE PACIFIC
COAST) - WITH A 20-30% PROBABILITIES FOR VISIBILITIES LESS THAN A
MILE AND CEILINGS LESS THAN 500 FT. TERMINALS OUTSIDE OF THIS AREA
WILL STILL HAVE A LOWER CHANCE OF SEEING AT LEAST SOME PATCHY OR
VICINITY FOG (ESPECIALLY NEAR WATERS AND LOW LYING AREAS) - BUT
PROBABILITIES ARE TOO LOW TO INCLUDE IN THE TAF AT THIS TIME. WINDS
WILL RETURN TO THE SOUTHWEST WEDNESDAY, PICK UP TO 8-12 KT WITH
GUSTS TO 20 KT POSSIBLE IN THE AFTERNOON. MORNING FOG WILL CLEAR
FROM 17-19Z AS HIGH CLOUDS BUILD IN WITH THE FRONT. THERE IS A 60-
80% CHANCE OF SHOWERS WEDNESDAY AFTERNOON/EVENING, WHICH MAY RESULT
IN BRIEF VISIBILITY/CEILING REDUCTIONS.
KSEA...VFR IS EXPECTED THROUGH THE TAF PERIOD. WHILE SOME BRIEF
PATCHY FOG IN THE VICINITY OF THE TERMINAL CANNOT BE RULED OUT
WEDNESDAY MORNING, THE THREAT IS TOO LOW TO INCLUDE IN THE TAF, AND
IS LARGELY EXPECTED TO REMAIN TO THE WEST OF THE TERMINAL. RAIN
SHOWERS ARE EXPECTED TO ARRIVE AFTER 20Z. WINDS THROUGH TONIGHT
REMAIN NORTHERLY 4-6 KT, DECREASING TO UNDER 5 KT AND SWITCHING TO
THE SOUTH AFTER 12Z WEDNESDAY, THEN PICKING BACK UP TO 8-12 KT
GUSTING TO 20 KT AFTER 18Z WEDNESDAY.
HPR
MARINE
HIGH PRESSURE WILL BUILD INLAND AS A RIDGE PASSES THROUGH
THE AREA TONIGHT INTO WEDNESDAY. WINDS THROUGH WEDNESDAY AFTERNOON
ARE LIGHT OUT OF THE SOUTH ACROSS ALL WATERS. SEAS HOWEVER REMAIN
ELEVATED AT 10-15 FT AT 15 SECONDS, BUT WILL DECREASE DOWN TO 7 TO
10 FT TONIGHT INTO WEDNESDAY. A SMALL CRAFT ADVISORY REMAINS IN
EFFECT THROUGH WEDNESDAY FOR ALL COASTAL WATERS, WESTERN STRAIT OF
JUAN DE FUCA, AND GRAYS HARBOR BAR. ADDITIONALLY, A FEW OF THE
INTERIOR WATERS MAY SEE PATCHY FOG WEDNESDAY MORNING (ESPECIALLY IN
SOUTH PUGET SOUND).
A TROUGH WILL DRIVE A WEAK FRONT ACROSS THE WATERS WEDNESDAY
AFTERNOON INTO THURSDAY WITH SHOWERS. THERE IS A 20% CHANCE OF
ISOLATED THUNDER IN THE WATERS JUST OFFSHORE OF NEAH BAY LATE
WEDNESDAY EVENING. WINDS WILL BECOME SUSTAINED AROUND 15 KT IN THE
COASTAL WATERS. A COUPLE ISOLATED GUSTS ABOVE 20 KT ARE POSSIBLE IN
THE INNER COASTAL WATERS, AS WELL AS THE WEST STRAIT OF JUAN DE FUCA.
A STRONGER TROUGH/FRONTAL SYSTEM WILL IMPACT THE AREA THURSDAY INTO
FRIDAY, WITH A STEADIER RAIN LIKELY ACROSS ALL WATERS. AGAIN, A LOW
CHANCE OF THUNDER (20%) EXISTS FOR THE NORTHERN COASTAL WATERS LATE
THURSDAY EVENING. MAIN CONCERN IS WINDS AND SEAS WITH THIS SYSTEM
ACROSS ALL WATERS. GIVEN THE 60-80% CHANCE OF WIND GUSTS EXCEEDING
GALE FORCE, A GALE WATCH WAS ISSUED THURSDAY MORNING THROUGH FRIDAY
MORNING FOR THE CHANCE OF WINDS OF 30-40 KT WITH ISOLATED GUSTS TO
45 KT POSSIBLE. THIS INCLUDES ALL COASTAL WATERS, STRAIT OF JUAN DE
FUCA, ADMIRALTY INLET, AND NORTHERN INLAND WATERS. THE HIGHEST WINDS
ARE EXPECTED IN THE STRAIT OF JUAN DE FUCA, WHERE THERE IS AN
OUTSIDE (5-10%) CHANCE OF A STORM FORCE GUST TO 50 KT. IN ADDITION,
SEAS WILL INCREASE TO 14 TO 18 FT IN THE COASTAL WATERS, WITH
PERIODS AROUND 15 SECONDS.
THERE IS SOME UNCERTAINTY GOING INTO THE WEEKEND AS TO WHERE THE
NEXT SYSTEM WILL PASS THROUGH. THERE IS AT LEAST ENOUGH PROBABILITY
AT THIS TIME TO BE CONCERNED OF SMALL CRAFT ADVISORY WINDS IN THE
COASTAL WATERS, AND MOST INTERIOR WATERS SATURDAY INTO SUNDAY, WITH
GALE FORCE WINDS POTENTIALLY CONTINUING IN THE STRAIT OF JUAN DE
FUCA AREAS AS WELL. SEAS THROUGH THE WEEKEND ARE EXPECTED TO REMAIN
AT 10 TO 14 FT THROUGH EARLY NEXT WEEK.
HPR
HYDROLOGY
THE RIVER FLOOD RISK HAS CONTINUED TO DIMINISH TODAY.
WE ARE STILL ANTICIPATING BRIEF ATMOSPHERIC RIVER CONDITIONS,
PRIMARILY THURSDAY NIGHT THROUGH FRIDAY, BUT GENERALLY THE TREND HAS
BEEN WEAKER AND OVER A MORE NARROW TIME FRAME. AT THIS TIME THE RISK
OF RIVER FLOODING IS MAINLY LIMITED TO VERY SENSITIVE RIVERS LIKE
THE SKOKOMISH IN MASON COUNTY. EVEN THERE, THE LATEST FORECAST PUTS
THE RIVER JUST BELOW ACTION STAGE FRIDAY WITH THE POTENTIAL TO POP
ABOVE ACTION STAGE LATER NEXT WEEK WITH ADDITIONAL RAINFALL.
THAT SAID, PRECIPITATION RATES OVER A 12-24 HOUR PERIOD THURSDAY
NIGHT THROUGH FRIDAY MAY BE HIGH ENOUGH TO BRING A RISK OF
URBAN/SMALL STREAM NUISANCE FLOODING, ESPECIALLY IN AREAS WITH
POOR/BLOCKED DRAINAGE (LEAVES WILL BE FALLING DURING THIS EVENT DUE
TO GUSTY WINDS). RISKS TO BURN SCARS WILL ALSO NEED TO BE MONITORED
THROUGH THIS EVENT, BUT CURRENTLY THE RISK APPEARS TO BE BELOW ANY
ALERT LEVELS.
-WOLCOTT-
SEW WATCHES/WARNINGS/ADVISORIES
WA...NONE.
PZ...SMALL CRAFT ADVISORY UNTIL 5 AM PDT WEDNESDAY FOR COASTAL
WATERS FROM CAPE FLATTERY TO JAMES ISLAND 10 TO 60 NM-
COASTAL WATERS FROM CAPE FLATTERY TO JAMES ISLAND OUT 10
NM-COASTAL WATERS FROM JAMES ISLAND TO POINT GRENVILLE 10
TO 60 NM-COASTAL WATERS FROM JAMES ISLAND TO POINT
GRENVILLE OUT 10 NM-COASTAL WATERS FROM POINT GRENVILLE
TO CAPE SHOALWATER 10 TO 60 NM-COASTAL WATERS FROM POINT
GRENVILLE TO CAPE SHOALWATER OUT 10 NM-GRAYS HARBOR BAR-
WEST ENTRANCE U.S. WATERS STRAIT OF JUAN DE FUCA.
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