448
FXUS66 KSEW 181059
AFDSEW
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SEATTLE WA
259 AM PST THU DEC 18 2025
SYNOPSIS
A SERIES OF WEATHER SYSTEMS WILL MOVE ACROSS WESTERN WASHINGTON
OVER THE NEXT WEEK, BRINGING PERIODS OF LOWLAND RAIN, MOUNTAIN
SNOW, AND BREEZY CONDITIONS AT TIMES.
SHORT TERM /TODAY THROUGH SATURDAY/
THE NEXT SYSTEM MOVING INTO THE REGION TODAY WILL BRING ANOTHER
ROUND OF GUSTY WINDS, LOWLAND RAIN, AND MOUNTAIN SNOW TO
WESTERN WASHINGTON. LATEST RADAR ALREADY SHOWS LIGHT RAIN
MOVING UP INTO THE REGION THIS MORNING. WHILE THE BULK OF THE
PRECIPITATION WITH THIS SYSTEM WILL BE FOCUSED SOUTH OF THE AREA
OVER NORTHWESTERN OREGON, CAN STILL EXPECT AN UNSETTLED AND
BLUSTERY DAY FOR AREAS ACROSS WESTERN WASHINGTON. RAINFALL
TOTALS FOR THE LOWLANDS REMAIN ON TRACK TO BE BETWEEN 0.25-0.75
INCHES, WITH LOCALLY HIGHER AMOUNTS POSSIBLE SOUTH OF THE SOUND
AND ACROSS THE CHEHALIS RIVER VALLEY. SNOW WILL CONTINUE FOR
THE MOUNTAINS THROUGH THE MORNING HOURS, WITH SNOW LEVELS
GENERALLY HOVERING AROUND 3000 FT. SNOW LEVELS WILL RISE AGAIN
THROUGHOUT THE DAY, INCREASING TO 6000-7000 FT BY THIS AFTERNOON.
WITH WARMER AIR MOVING IN ALOFT, COULD EVEN SEE A BRIEF PERIOD
OF FREEZING RAIN AT THE PASSES AS SNOW CHANGES OVER TO RAIN.
UNCERTAINTY DOES LINGER AS TO HOW LONG THE WARM AIR WILL REMAIN
IN PLACE THOUGH, WITH SNOW LEVELS EXPECTED TO PLUMMET TO 1500-2500
FT AGAIN TONIGHT. SOUTHERLY WINDS WILL PICK UP THIS MORNING,
PEAK THIS AFTERNOON, AND EASE THROUGH THE EVENING HOURS. THE
STRONGEST WINDS WILL BE ALONG THE COAST AND FOR AREAS GENERALLY
NORTH OF EVERETT, THOUGH CONDITIONS WILL BE GUSTY AREA-WIDE.
WINDS WILL PERSIST AT 15 TO 25 MPH, WITH GUSTS TO 45 MPH
POSSIBLE AT TIMES. ANOTHER STRONGER SURGE OF WESTERLY WINDS IN
THE WAKE OF THE FRONT WILL LIKELY KEEP CONDITIONS BLUSTERY FOR
AREAS LIKE WHIDBEY ISLAND THROUGH TONIGHT.
IN ADDITION TO THE PRECIPITATION AND WIND HAZARDS, MINOR COASTAL
FLOODING WILL BE POSSIBLE TODAY WITHIN THE HOURS OF HIGH TIDE
FOR AREAS ALONG THE SAN JUAN ISLANDS AND STRAIT OF JUAN DE FUCA
DUE TO HIGHER ASTRONOMICAL TIDES.
THE SYSTEM WILL SHIFT FURTHER SOUTHWARD ON FRIDAY, THOUGH CONDITIONS
ARE EXPECTED TO REMAIN ACTIVE HEADING INTO THE WEEKEND. ADDITIONAL
ROUNDS OF LOWLAND RAIN AND PERIODS OF SUBSTANTIAL MOUNTAIN SNOW
REMAIN LIKELY AGAIN ON FRIDAY AND SATURDAY WITH SNOW LEVELS
GENERALLY HOVERING BETWEEN 1500-2500 FT.
LONG TERM /SATURDAY NIGHT THROUGH WEDNESDAY/
CONDITIONS GENERALLY LOOK TO REMAIN RATHER ACTIVE THROUGH THE
LONG TERM, WITH ENSEMBLE CLUSTERS IN DECENT AGREEMENT OF AN
UPPER LEVEL TROUGH DIGGING ACROSS THE NORTHEASTERN PACIFIC AND
SWINGING ADDITIONAL DISTURBANCES ACROSS WESTERN WASHINGTON. WITH
SNOW LEVELS EXPECTED TO REMAIN BELOW PASS LEVEL, THIS WILL
BRING ADDITIONAL ROUNDS OF MOUNTAIN SNOW AND LOWLAND RAIN
THROUGH THE FIRST HALF OF NEXT WEEK. WINDS WILL ALSO BE BREEZY
AT TIMES AS THESE SYSTEMS MOVE THROUGH.
14
AVIATION
GENERALLY ZONAL FLOW ALOFT INTO FRIDAY, ALTHOUGH MINOR SHORTWAVES
EMBEDDED IN THE FLOW MAY ALLOW OCCASIONAL LOCALIZED DEVIATIONS TO
THE NW OR SW. SOUTHERLY TO SOUTHEASTERLY SURFACE WINDS RANGING 8-14
KTS THIS MORNING ARE EXPECTED TO INCREASE FOR MANY TERMINALS IN
ADVANCE OF AN INCOMING FRONTAL SYSTEM THIS MORNING TO SPEEDS 10-15
KTS WITH GUSTS UP TO 25KT. SOME SITES MAY EXPERIENCE A LULL IN WINDS
IN THE LATE MORNING AND EARLY AFTERNOON, BUT BY MID-AFTERNOON SPEEDS
SHOULD RAMP UP AGAIN TO 15-20 MPH WITH GUSTS UP TO 35 MPH.
CIGS THIS EARLY MORNING LARGELY CLUSTERED INTO TWO GROUPS: MVFR
CONDITIONS CONCENTRATED OVER THE SAN JUAN ISLANDS AND WESTERN SKAGIT
AND WHATCOM COUNTIES WHILE THE REMAINDER OF THE CWA IS UNDER
GENERALLY VFR CONDITIONS. AS SHOWERS START TO ENTER INTO THE OLYMPIC
PENINSULA, PRECIP MAY ALLOW FOR CONDITIONS TO DEGRADE THERE TO MVFR
BY 12-14Z. SOME LINGERING SHOWERS OVER SCATTERED PORTIONS OF THE
EASTERN HALF OF THE CWA MAY NOT HAVE MUCH IMPACT ON CIGS, LIKELY
WAITING FOR THE AFOREMENTIONED INITIAL BAND OF PRECIP TO MAKE ITS
WAY EASTWARD...MORE IN THE 14-16Z TIME FRAME. WIDESPREAD MVFR TO IFR
CONDITIONS EXPECTED BY LATE MORNING AND REMAINING THAT WAY INTO THE
EVENING. GUIDANCE SUGGESTS SOME IMPROVEMENT TO HIGH-END MVFR TO LOW-
END VFR CONDITIONS TONIGHT AFTER 06Z...AND THE INCREASED WINDS
EXPECTED DURING THAT TIME MAY HELP FACILITATE THAT. HOWEVER, THE
ABUNDANT LOW-LEVEL MOISTURE MAY WORK COUNTER TO THOSE ENDS. WILL
LEAN A LITTLE MORE ON THE OPTIMISTIC SIDE OF THINGS FOR 12Z
FORECAST, BUT WILL KEEP THIS POSITIVITY RESTRICTED TO, AT BEST, THE
VERY BASEMENT OF VFR CONDITIONS.
KSEA...CIGS CONTINUE TO LOWER, BUT REMAIN VFR AT THE TIME OF THIS
WRITING. AS STATED ABOVE, WHILE CURRENT TAF MAY BE A LITTLE TOO
AGGRESSIVE WITH LOWER CIGS, SHOULD SEE MVFR CONDITIONS ARISE PERHAPS
MORE IN A 13-15Z TIME FRAME. LATEST RUNS ALSO SEEM TO BE BACKING
AWAY FROM IFR CONDITIONS AT THE TERMINAL LATER THIS MORNING AND EARLY
THIS AFTERNOON, WITH LOW-END TO MID MVFR BEING MORE LIKELY. SURFACE
WINDS WILL OBEY PATTERN ILLUSTRATED ABOVE, POSING THE SAME FORECAST
QUANDARY FOR CIGS AND WILL LIKELY OPT AT A SIMILAR SOLUTION,
BRINGING CIGS TONIGHT UP TO 3000 FT BETWEEN 04-06Z TONIGHT AND
KEEPING THEM THERE FOR THE REMAINDER OF THE TAF PERIOD.
18
MARINE
A FRONTAL SYSTEM WILL MOVE ACROSS THE WATERS TODAY, BRINGING
ELEVATED WINDS AND SEAS TO THE REGION. THE STRONGEST WINDS WILL
BE ALONG THE COASTAL WATERS AND ALONG THE EASTERN STRAIT OF
JUAN DE FUCA, WHERE GALES WITH FREQUENT GUSTS TO 45 KT WILL BE
LIKELY. WINDS ACROSS THE REMAINDER OF THE INTERIOR WATERS WILL
GUSTY AS WELL, BUT WILL TYPICALLY REMAIN WITHIN SMALL CRAFT
THRESHOLDS. A STRONG WESTERLY PUSH IN THE WAKE OF THE SYSTEM WILL
BRING ANOTHER ROUND OF GALES TO THE CENTRAL AND EAST STRAIT
THIS AFTERNOON AND EVENING BEFORE CONDITIONS EASE SOMEWHAT. THE
OVERALL PATTERN REMAINS ACTIVE OVER THE WEEKEND AND INTO EARLY
NEXT WEEK AS ADDITIONAL SYSTEMS MOVE ACROSS THE AREA WATERS.
SEAS WILL BUILD TOWARDS 14-17 FT TODAY AND LOOK TO GRADUALLY
SUBSIDE BACK BELOW 10 FT OVER THE WEEKEND. AN UPTICK IN SEAS IS
LIKELY AGAIN NEXT WEEK AS ADDITIONAL DISTURBANCES MOVE ACROSS
THE WATERS.
14
HYDROLOGY
THE NEXT WAVE OF PRECIP IS ALREADY MOVING INTO THE WESTERN HALF OF
THE CWA THIS EARLY MORNING BRINGING ANOTHER ROUND OF STEADY RAINFALL
TO THE AREA. SNOW LEVELS WILL REMAIN LOWER THIS MORNING, AROUND 2500
TO 3000 FEET, BUT ARE STILL EXPECTED TO RISE TO 5000 TO 7000 FEET
THIS AFTERNOON. SNOW LEVELS WILL FALL AGAIN TO 1500 FEET FRIDAY. QPF
AMOUNTS THROUGH FRIDAY MORNING WILL RANGE 2 TO 3 INCHES FOR THE
MAJORITY OF THE OLYMPICS AND CASCADES, WITH LOCALIZED HIGHER AMOUNTS
OVER THE CASCADES OF PIERCE AND LEWIS COUNTIES.
ONGOING RIVER FLOODING CONTINUES FOR NUMEROUS RIVERS OFF THE
CASCADES, AS WELL AS THE SKOKOMISH RIVER IN MASON COUNTY. RIVERS
WILL CONTINUE TO REMAIN ELEVATED DUE TO THE CONTINUED PRECIPITATION.
HOWEVER, AS THIS SYSTEM IS NOT EXPECTED TO HAVE THE SAME INTENSITY
AS THE PREVIOUS AR EVENTS, SOME RIVERS WILL STILL SEE LEVELS SLOWLY
RECEDE EVEN WITH THE INCOMING RAINFALL. ADDITIONALLY, GIVEN THE
GENERAL BREAK IN PRECIP YESTERDAY, THERE WILL BE A LITTLE BIT OF A
LAG IN RIVERS THAT DO REACT TO THIS CURRENT INCOMING SYSTEM. RIVERS
THAT DO SEE LEVELS RISE BECAUSE OF THIS MAY NOT SEE IMPACTS UNTIL
LATE TONIGHT OR FRIDAY. STAY TUNED TO THE LATEST HYDROLOGICAL
FORECASTS FOR ANY RIVERS IN YOUR AREA, AS THE RISK FOR ADDITIONAL
FLOODING IS STILL POSSIBLE.
THAT SAID, A FLOOD WATCH REMAINS IN EFFECT FOR SKAGIT, KING, PIERCE,
THURSTON, AND GRAYS HARBOR COUNTIES THROUGH FRIDAY AFTERNOON DUE TO
THIS ADDITIONAL INCOMING PRECIP AND AREA RIVERS CURRENTLY RUNNING
HIGH.
THE LANDSLIDE THREAT WILL REMAIN HIGH THROUGH AT LEAST FRIDAY.
18
SEW WATCHES/WARNINGS/ADVISORIES
WA...COASTAL FLOOD ADVISORY FROM 4 AM TO 8 AM PST THIS MORNING FOR
SAN JUAN COUNTY.
WIND ADVISORY FROM 6 AM THIS MORNING TO 11 PM PST THIS EVENING
FOR ISLAND COUNTY-LOWLANDS OF WESTERN SKAGIT AND
NORTHWESTERN SNOHOMISH COUNTIES-LOWLANDS OF WESTERN
WHATCOM COUNTY-SAN JUAN COUNTY.
WINTER WEATHER ADVISORY UNTIL 10 AM PST THIS MORNING FOR
CASCADES OF PIERCE AND LEWIS COUNTIES-CASCADES OF
SNOHOMISH AND NORTHERN KING COUNTIES-CASCADES OF SOUTHERN
KING COUNTY-CASCADES OF WHATCOM AND SKAGIT COUNTIES.
FLOOD WATCH THROUGH FRIDAY AFTERNOON FOR CASCADES OF PIERCE
AND LEWIS COUNTIES-CASCADES OF SNOHOMISH AND NORTHERN
KING COUNTIES-CASCADES OF SOUTHERN KING COUNTY-CITY OF
SEATTLE-EASTSIDE-FOOTHILLS AND VALLEYS OF CENTRAL KING
COUNTY-FOOTHILLS AND VALLEYS OF PIERCE AND SOUTHERN KING
COUNTIES-FOOTHILLS AND VALLEYS OF SNOHOMISH AND NORTHERN
KING COUNTIES-FOOTHILLS AND VALLEYS OF THURSTON AND LEWIS
COUNTIES-FOOTHILLS OF THE WESTERN AND SOUTHERN OLYMPIC
PENINSULA-GRAYS HARBOR COUNTY COAST-LOWER CHEHALIS RIVER
VALLEY-LOWLANDS OF LEWIS AND SOUTHERN THURSTON COUNTIES-
LOWLANDS OF PIERCE AND SOUTHERN KING COUNTIES-MIDDLE
CHEHALIS RIVER VALLEY-OLYMPIA AND SOUTHERN PUGET SOUND-
OLYMPICS-SHORELINE / LYNNWOOD / SOUTH EVERETT AREA-
WILLAPA AND BLACK HILLS.
WIND ADVISORY FROM 11 AM THIS MORNING TO 7 PM PST THIS EVENING
FOR FOOTHILLS AND VALLEYS OF PIERCE AND SOUTHERN KING
COUNTIES-FOOTHILLS AND VALLEYS OF THURSTON AND LEWIS
COUNTIES-GRAYS HARBOR COUNTY COAST-LOWLANDS OF LEWIS AND
SOUTHERN THURSTON COUNTIES-LOWLANDS OF PIERCE AND
SOUTHERN KING COUNTIES-NORTHERN WASHINGTON COAST-OLYMPIA
AND SOUTHERN PUGET SOUND-WILLAPA AND BLACK HILLS.
COASTAL FLOOD ADVISORY FROM 9 AM THIS MORNING TO 1 PM PST THIS
AFTERNOON FOR EASTERN STRAIT OF JUAN DE FUCA.
PZ...SMALL CRAFT ADVISORY UNTIL 6 PM PST THIS EVENING FOR GRAYS
HARBOR BAR.
SMALL CRAFT ADVISORY UNTIL 4 PM PST THIS AFTERNOON FOR
ADMIRALTY INLET-NORTHERN INLAND WATERS INCLUDING THE SAN
JUAN ISLANDS-PUGET SOUND AND HOOD CANAL-WEST ENTRANCE
U.S. WATERS STRAIT OF JUAN DE FUCA.
SMALL CRAFT ADVISORY UNTIL 4 AM PST EARLY THIS MORNING 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-EAST
ENTRANCE U.S. WATERS STRAIT OF JUAN DE FUCA.
GALE WARNING FROM 4 AM EARLY THIS MORNING TO 10 PM PST THIS
EVENING FOR EAST ENTRANCE U.S. WATERS STRAIT OF JUAN DE
FUCA.
GALE WARNING FROM 4 AM EARLY THIS MORNING TO 4 PM PST THIS
AFTERNOON 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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