588
FXUS66 KSEW 181653
AFDSEW
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SEATTLE WA
953 AM PDT SAT OCT 18 2025
SYNOPSIS
A FRONT WILL MOVE THROUGH THE AREA TONIGHT. COOL AND
UNSTABLE AIR MASS BEHIND THE FRONT SUNDAY. WEAK UPPER LEVEL RIDGE
OVER THE AREA SUNDAY NIGHT INTO MONDAY. WEAK SYSTEM MOVING BY TO
THE NORTH MONDAY NIGHT AND TUESDAY. STRONGER AND WETTER SYSTEMS
ARRIVING WEDNESDAY AND AGAIN LATER THURSDAY INTO FRIDAY.
SHORT TERM /TODAY THROUGH MONDAY/
NO SIGNIFICANT CHANGES MADE
TO THE FORECAST THIS MORNING. THE PREVIOUS DISCUSSION CAN BE FOUND
BELOW ALONG WITH UPDATES TO THE AVIATION AND MARINE SECTIONS:
CLOUDS THICKENING AND LOWERING TODAY AS THE FRONTAL SYSTEM
OFFSHORE APPROACHES THE AREA. RAIN BEGINNING ALONG THE COAST THIS
MORNING WITH THE RAIN SPREADING INLAND THIS AFTERNOON. WINDS
PICKING UP ALONG THE COAST AND OVER THE NORTHWEST INTERIOR IN THE
AFTERNOON. NOT STRONG ENOUGH FOR A WIND ADVISORY BUT IT WILL BE
BREEZY. HIGHS TODAY IN THE MID 50S.
RAIN AND BREEZY CONDITIONS THIS EVENING WITH THE FRONT REACHING
THE COAST BY MIDNIGHT. THE FRONT WILL BE THROUGH THE PUGET SOUND
AREA IN THE EARLY MORNING HOURS. SNOW LEVELS RISING UP TO 8000 TO
10000 FEET IN THE MOUNTAINS AHEAD OF THE FRONT MAKING THE
PRECIPITATION TYPE RAIN EXCEPT THE HIGHER REACHES OF THE VOLCANOS.
IN GENERAL ONE TO TWO INCHES OF RAIN IN THE MOUNTAINS WITH AROUND
AN INCH ON THE COAST AND A HALF TO ONE INCH OVER THE INTERIOR.
LOWS IN THE UPPER 40S.
AIR MASS COOLING QUICKLY AND DESTABILIZING POST FRONTAL SUNDAY.
SNOW LEVELS LOWERING TO AROUND 5000 FEET WITH AN INCH TO AROUND 5
INCHES OF NEW SNOW IN THE FORECAST. HIGHEST ACCUMULATIONS IN THE
NORTH CASCADES. WITH THE AIR MASS DESTABILIZING CAN'T RULE OUT THE
POSSIBILITY OF THUNDERSTORMS BUT THE CHANCES ARE NOT HIGH, 20
PERCENT OR LESS. FOR THE MOST PART SUNDAY ENDING UP BEING A BREEZY
DAY WITH SHOWERS I.E. FALL IN THE PACIFIC NORTHWEST. CONVERGENCE
ZONE DEVELOPING IN THE AFTERNOON OVER SNOHOMISH COUNTY ENHANCING
THE SHOWER ACTIVITY. HIGHS IN THE MID 50S.
CONVERGENCE ZONE MOVING SOUTH INTO THE METRO AREA AND DISSIPATING
SUNDAY NIGHT. SHOWER ACTIVITY OUTSIDE OF THE CONVERGENCE ZONE
DRYING UP QUICKLY WITH THE END OF DAYTIME "HEATING" AND THE
SUBSIDENCE ASSOCIATED WITH THE BUILDING OF A WEAK UPPER LEVEL
RIDGE. COULD SEE ANOTHER COUPLE INCHES OF SNOW IN THE CASCADES
ESPECIALLY IN THE NORTH CASCADES. WITH THE HIGH PASS IN THE NORTH
CASCADES WILL STAY WITH THE WINTER WEATHER ADVISORY THROUGH THE
EVENING HOURS. IN ALL EXPECTING 4 TO 8 INCHES OF NEW SNOW IN THE
NORTH CASCADES ABOVE ABOUT 5000 FEET TONIGHT THROUGH SUNDAY
EVENING WITH LESSER AMOUNTS FOR THE REMAINDER OF THE MOUNTAINS.
LOWS MONDAY MORNING IN THE LOWER TO MID 40S.
WEAK UPPER LEVEL RIDGE REMAINING OVER THE AREA MONDAY. THE
COMBINATION OF LOW LEVEL ONSHORE FLOW AND A WEAKENING SYSTEM
APPROACHING WILL KEEP SKIES MOSTLY CLOUDY/PARTLY SUNNY. HIGHS
AROUND 60.
LONG TERM /TUESDAY THROUGH FRIDAY/
EXTENDED MODELS IN GOOD
AGREEMENT WITH A WARM FRONT BRUSHING THE NORTHERN PORTION MONDAY
NIGHT. DISSIPATING TRAILING COLD FRONT MOSTLY LOSING THE BATTLE
TO THE REBUILDING WEAK UPPER LEVEL RIDGE TUESDAY. UPPER LEVEL
RIDGE MOVING EAST QUICKLY TUESDAY NIGHT OPENING THE DOOR TO A MORE
CONSOLIDATED FRONT WEDNESDAY. A MUCH WETTER SYSTEM, POSSIBLE
ATMOSPHERIC RIVER, ARRIVING LATE IN THE WEEK. GOOD CONSENSUS THAT
THE FRONT WILL MOVE INTO WESTERN WASHINGTON BUT THERE IS A TIMING
AND INTENSITY ISSUE. ECMWF SOLUTIONS ABOUT 12 HOURS FASTER THAN
THE GFS SOLUTIONS WHICH HAVE THE FRONT NOT MOVING THROUGH UNTIL
LATER FRIDAY. THE GFS ENSEMBLE MEAN ALSO WETTER THAN THE ECMWF FOR
THE RAINFALL AMOUNTS. FUN FACT, SEATTLE HAS NOT HAD A DAY WITH AN
INCH OF RAIN OR MORE IN ALMOST TWO YEARS. THE CURRENT STREAK IS
AT 681 DAYS. THE LAST TIME SEATTLE TACOMA AIRPORT GOT OVER AN INCH
OF RAIN WAS DECEMBER 5TH, 2023 ( 2.39 INCHES ). THIS IS THE
LONGEST STREAK OF ITS KIND. THE PREVIOUS LONGEST STRETCH WAS 586
DAYS FROM JANUARY 15, 1976 TO AUGUST 22ND, 1977. THERE HAVE ONLY
BEEN THREE OTHER STREAKS LONGER THAN A YEAR SINCE RECORDS STARTED
IN 1945. EVEN THE ECMWF IS HINTING AT THE FRONT STALLING OVER THE
AREA WITH AN UPPER LEVEL TROUGH DIGGING SOUTH OFFSHORE LATER
THURSDAY INTO FRIDAY. BOTH THURSDAY AND FRIDAY HAVE A CHANCE TO
BREAK THE STREAK IN SEATTLE. FELTON
AVIATION
NORTHWEST TO WESTERLY FLOW ALOFT AS AN UPPER LEVEL
TROUGH APPROACHES THE AREA. MOST TERMINALS ARE VFR EARLY THIS
MORNING WITH THE EXCEPTION OF OLM AND HQM WHERE FOG HAS BEGUN TO
FORM. HIGH CLOUDS OVER MUCH OF THE REST OF THE AREA WILL KEEP
WIDESPREAD FOG CONCERNS AT BAY THIS MORNING. CLOUDS WILL BEGIN TO
FILL IN AND LOWER LATER THIS MORNING AS A FRONTAL SYSTEM BEGINS TO
MOVE INTO THE AREA. RAIN WILL MOVE ONTO THE COAST BY AROUND 18Z THIS
MORNING, FILLING IN ACROSS THE REST OF THE AREA THIS AFTERNOON. THE
FRONT WILL MOVE ACROSS THE AREA LATE TONIGHT INTO EARLY SUNDAY
MORNING, WITH SCATTERED SHOWERS CONTINUING THROUGH MUCH OF THE DAY
SUNDAY. CEILINGS WILL BEGIN TO LOWER TO MVFR THIS EVENING ONCE THE
RAIN HAS FILLED IN, THROUGH THERE MAY BE VISIBILITY RESTRICTIONS IN
RAIN THAT WILL PROMOTE AN EARLIER START TO MVFR CONDITIONS. CEILINGS
MAY LIFT A BIT AND BREAK UP BEHIND THE FRONTAL PASSAGE AT AROUND 09-
12Z SUN, BUT WITH THIS BEING THE VERY END OF THE TAF PERIOD, WILL
KEEP MVFR CONDITIONS CONTINUING IN WIDESPREAD SHOWERS. MOSTLY CALM
WINDS WILL RESUME THIS MORNING AS SOUTH TO SOUTHEASTERLY, INCREASING
TO 8 TO 15 KT THIS AFTERNOON, PERHAPS APPROACHING 20 KT AT BLI.
GUSTS 25 TO 35 KT WILL BE POSSIBLE NORTH OF PAE UP TO BLI. WINDY
CONDITIONS WILL CONTINUE THROUGH TONIGHT INTO EARLY SUNDAY.
KSEA...VFR CONDITIONS THIS MORNING WITH LIGHT AND VARIABLE WINDS.
RAINFALL EXPECTED TO START IN THE AFTERNOON AFTER AROUND 20Z,
ALTHOUGH BEST CHANCES TO KICK IN AROUND 00Z. IT IS AFTER 00Z WHERE
RAINFALL RATES MAY ALLOW FOR VIS REDUCTIONS DOWN TO 4SM. CEILINGS
WILL ALSO BEGIN TO FALL TO MVFR AFTER AROUND 03-06Z SUNDAY. S/SE
WINDS WILL INCREASE THIS AFTERNOON, BECOMING 8-15 KT WITH GUSTS UP
TO 20 KT BY THIS EVENING AND CONTINUE INTO SUNDAY MORNING.
62/MAZURKIEWICZ
MARINE
A FRONTAL SYSTEM WILL CROSS THE WATERS LATER TODAY INTO
TONIGHT BRING SMALL CRAFT ADVISORY WINDS TO ALL THE WATERS. POST
FRONTAL SMALL CRAFT ADVISORY WINDS OVER THE COASTAL WATERS AS
WELL AS THROUGH THE STRAIT OF JUAN DE FUCA AND OVER THE NORTHERN
INLAND WATERS SUNDAY. WINDS EASING SUNDAY NIGHT AS HIGH PRESSURE
BUILDS INTO THE AREA. A WEAK FRONT WILL BRUSH THE NORTHERN PORTION
MONDAY NIGHT INTO TUESDAY. STRONGER SYSTEMS WILL ARRIVE WEDNESDAY
AND THURSDAY FOR ANOTHER ROUND OF AT LEAST SMALL CRAFT ADVISORY
WINDS FOR MOST OF THE WATERS.
SEAS IN THE 10 TO 12 FOOT RANGE TODAY BUILDING TO 14 TO 18 FEET
TONIGHT INTO SUNDAY. SEAS AS HIGH AS 20 FEET POSSIBLE OVER THE
OUTER COASTAL WATERS. SEAS SUBSIDING SUNDAY NIGHT INTO MONDAY
DROPPING BELOW 10 FEET OVER THE INNER COASTAL WATERS MONDAY NIGHT.
SEAS WILL BE ON THE INCREASE AGAIN TUESDAY WITH SEAS ABOVE 10
FEET OVER MOST OF THE WATERS AGAIN BY WEDNESDAY. FELTON
HYDROLOGY
A FRONTAL SYSTEM WILL BRING WIDESPREAD RAINFALL TO THE
REGION OVER THE WEEKEND, WITH UP TO AN INCH OF RAIN ACROSS THE
LOWLANDS AND 1 TO 3 INCHES OVER THE MOUNTAINS. WHILE THIS INFLUX OF
MOISTURE IS NOT EXPECTED TO CAUSE ANY RIVER FLOODING, IT COULD CAUSE
RAPID RISES ON SENSITIVE STREAMS AND CREEKS, POTENTIAL IMPACTS TO
BURN SCARS, AND LOCALIZED URBAN FLOODING. CONDITIONS WILL DRY OUT ON
MONDAY AND TUESDAY. ANOTHER SYSTEM ARRIVING WEDNESDAY WILL BRING
ANOTHER ROUND OF RAIN TO THE AREA. A WETTER SYSTEM WILL ARRIVE
THURSDAY OR FRIDAY. THIS SYSTEM COULD BE TAPPING INTO SOME SUB
TROPICAL MOISTURE BRINGING UP THE POSSIBILITY OF HYDROLOGICALLY
SIGNIFICANT RAINFALL OVER THE OLYMPICS THURSDAY NIGHT INTO FRIDAY.
THE FIRST SKOKOMISH RIVER FLOOD OF THE SEASON IS NOT OUT OF THE
QUESTION LATE NEXT WEEK. FELTON
SEW WATCHES/WARNINGS/ADVISORIES
WA...WINTER WEATHER ADVISORY FROM 11 PM THIS EVENING TO 11 PM PDT
SUNDAY FOR CASCADES OF WHATCOM AND SKAGIT COUNTIES.
PZ...SMALL CRAFT ADVISORY UNTIL 6 AM PDT MONDAY FOR GRAYS HARBOR BAR.
SMALL CRAFT ADVISORY FROM 2 PM THIS AFTERNOON TO 6 AM PDT MONDAY
FOR CENTRAL U.S. WATERS STRAIT OF JUAN DE FUCA-EAST
ENTRANCE U.S. WATERS STRAIT OF JUAN DE FUCA-NORTHERN INLAND
WATERS INCLUDING THE SAN JUAN ISLANDS-WEST ENTRANCE U.S.
WATERS STRAIT OF JUAN DE FUCA.
SMALL CRAFT ADVISORY FROM 2 PM THIS AFTERNOON TO 6 AM PDT SUNDAY
FOR ADMIRALTY INLET.
SMALL CRAFT ADVISORY FROM 6 PM THIS EVENING TO 6 AM PDT SUNDAY
FOR PUGET SOUND AND HOOD CANAL.
SMALL CRAFT ADVISORY UNTIL 6 PM PDT MONDAY 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.
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