899
FXUS66 KSEW 190428
AFDSEW
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SEATTLE WA
828 PM PST THU DEC 18 2025
UPDATE
SNOW HAS FULLY TRANSITIONED TO RAIN AT BOTH SNOQUALMIE AND WHITE
PASS, WITH RAIN BEING INFERRED AT STEVENS PASS BASED ON THE
TEMPERATURE OBSERVATION THERE. THUS, THE WINTER WEATHER ADVISORY
WAS ALLOWED TO EXPIRE. THERE WILL BE A BRIEF PERIOD OF RAIN
THROUGH LATE TONIGHT BEFORE SNOW LEVELS PLUMMET BACK TO THE
1500 TO 2000 FT EARLY TOMORROW MORNING. FROM THEN ON THROUGH
SATURDAY, HEAVY ACCUMULATING SNOW WILL RETURN TO THE MOUNTAINS.
ADDITIONALLY, STRONG WINDS CONTINUE TO BLOW THROUGH THE STRAIT
OF JUAN DE FUCA. STRONG WINDS PERSIST RIGHT ALONG THE COAST OF
THE STRAIT AND INTO ISLAND COUNTY. ELSEWHERE, WINDS REMAIN
ELEVATED BUT BELOW ADVISORY THRESHOLD. WINDS SHOULD CONTINUE TO
SLOWLY EASE TONIGHT. OTHERWISE THE FORECAST REMAINS ON TRACK.
SEE BELOW FOR UPDATES TO MARINE AND AVIATION. 62
SYNOPSIS
A SERIES OF WEATHER SYSTEMS WILL MOVE ACROSS WESTERN WASHINGTON
OVER THE NEXT WEEK, KEEPING THE UNSETTLED CONDITIONS ONGOING
ACROSS THE AREA. THESE UNSETTLED CONDITIONS COULD SEE PERIODS
OF LOWLAND RAIN, MOUNTAIN SNOW, AND BREEZY CONDITIONS AT TIMES
THROUGHOUT THE WEEKEND AND INTO THE EARLY HALF OF NEXT WEEK.
SHORT TERM /TONIGHT THROUGH SATURDAY NIGHT/
RECENT RADAR IMAGERY SHOWS A BULK OF RAINFALL OVER THE SOUTHERN
PORTIONS OF OUR AREA, WITH MOST OF THE HEAVIEST PRECIPITATION
FALLING OVER OREGON. AN UNSETTLED AND RAINY DAY IS STILL
EXPECTED OVER WESTERN WASHINGTON, WITH RAINFALL TOTALS GENERALLY
AROUND 0.25-0.50 OVER THE LOWLANDS, WITH LOCALLY HIGHER AMOUNTS
IN THE SOUTH SOUND. SNOW WILL CONTINUE IN THE MOUNTAINS, WITH
SNOW LEVELS RISING THIS AFTERNOON AND EVENING TO 6000 TO 7000
FEET. AS WARMER AIR MOVES ALOFT, CONTINUING TO MONITOR THE
POTENTIAL FOR A BRIEF PERIOD OF FREEZING RAIN AT THE PASSES, AS
SNOW CHANGES TO RAIN. UNCERTAINTY CONTINUES ON THE TIMING AND
THE DEPTH OF THE WARM LAYER OVER THE MOUNTAINS, AND HOW LONG
THAT LASTS FOR. SNOW LEVELS BEGIN TO QUICKLY PLUMMET LATE
TONIGHT THROUGH FRIDAY DOWNWARDS TO 1500 TO 2500 FEET, ALLOWING
FOR ACCUMULATIONS TO PILE UP WITHIN THE CASCADES. THEREFORE, A
WINTER STORM WARNING HAS BEEN ISSUED FOR MODERATE TO HEAVY
SNOWFALL AT TIMES, AS AREAS LIKE PARADISE AND BAKER COULD SEE
2-3 FEET, ALONG WITH SNOQUALMIE AND STEVENS SEEING A FOOT TO TWO
FEET OF SNOW THROUGHOUT THE WEEKEND.
SOUTHERLY WINDS WILL REMAIN ELEVATED THIS AFTERNOON, AROUND 25
TO 35 MPH, WITH OCCASIONAL GUSTS 45 TO 50 MPH POSSIBLE AT TIMES
THROUGHOUT THE INTERIOR THROUGH THIS EVENING. WINDS WILL EASE BY
TONIGHT. A SURGE OF WESTERLY WINDS THROUGH THE STRAIT WILL KEEP
AREAS LIKE WHIDBEY ISLAND BREEZY OVERNIGHT.
THE AFOREMENTIONED SYSTEM WILL CONTINUE TO SHIFT SOUTHWARD ON
FRIDAY, BUT CONDITIONS STILL REMAIN UNSETTLED OVER THE AREA,
WITH LOWLAND RAIN, MOUNTAIN SNOW, AND LOCALLY BREEZY CONDITIONS
AT TIMES. SNOW LEVELS WILL STAY AROUND 1500-2500 FEET, ALLOWING
FOR SNOWFALL TO CONTINUE IN THE MOUNTAINS.
LONG TERM /SUNDAY THROUGH THURSDAY/
ENSEMBLES ARE IN GENERALLY GOOD AGREEMENT IN UPPER LEVEL
TROUGHING OVER THE PACIFIC NORTHWEST THROUGH THE FIRST HALF OF
NEXT WEEK. ADDITIONAL SYSTEMS LOOK TO MOVE OVER THE AREA,
KEEPING UNSETTLED CONDITIONS OVER MOST OF THE AREA, WITH THESE
SYSTEMS GENERALLY REMAINING ON THE WEAKER SIDE. SNOW LEVELS LOOK
TO REMAIN BELOW PASS LEVEL, WHICH WOULD BRING MORE ROUNDS OF
MOUNTAIN SNOW, WITH RAIN EXPECTED IN THE LOWLANDS.
MAZURKIEWICZ
AVIATION
WEST-SOUTHWEST FLOW ALOFT WILL CONTINUE THROUGH FRIDAY
WITH TROUGHING OVER BRITISH COLUMBIA. VFR/MVFR FOR MOST AREAS THIS
EVENING IN A POST-FRONTAL AIRMASS AND CONTINUED ONSHORE FLOW.
LOCALIZED LIFR/IFR EXISTS IN THE VICINITY OF A CONVERGENCE ZONE OVER
SNOHOMISH COUNTY. VFR/MVFR CIGS WILL CONTINUE INTO FRIDAY. SCATTERED
SHOWERS WILL ALSO CONTINUE INTO FRIDAY, WITH DRIER CONDITIONS AT
TIMES IN THE VICINITY OF CENTRAL PUGET SOUND DUE TO RAIN SHADOWING.
BREEZY WEST-SOUTHWEST SURFACE WINDS THIS EVENING WILL SLOWLY SUBSIDE
TONIGHT INTO FRIDAY, BUT REMAIN ELEVATED DUE TO CONTINUED ONSHORE
FLOW.
KSEA...VFR CONDITIONS EARLY THIS EVENING WITH SCT/BKN LOW CLOUDS.
PREDOMINANTLY VFR CIGS EXPECTED TONIGHT, WITH PERIODS OF MVFR
POSSIBLE. PROBABILITIES (AROUND 40-50%) FOR MVFR CIGS PEAK BETWEEN
17-23Z ON FRIDAY. BREEZY SW SURFACE WINDS THIS EVENING, WITH GUSTS
RANGING 25 TO 35 KTS, WITH WINDS SLOWLY SUBSIDING LATE TONIGHT INTO
FRIDAY. JD
MARINE
A FRONTAL SYSTEM WILL IS CURRENTLY TRAVERSING NORTHWEST
WASHINGTON. WINDS HAVE SWITCHED TO WESTERLY THROUGH THE STRAIT
OF JUAN DE FUCA, CONTINUING TO PRODUCE GALE FORCE WINDS.
ELSEWHERE, WINDS HAVE BACKED OFF TO SMALL CRAFT ADVISORY
THRESHOLDS. WINDS SHOULD CONTINUE TO EASE OVERNIGHT INTO EARLY
TOMORROW MORNING, WHERE HEADLINES FOR THE INTERIOR WATERS BEGIN
TO DROP OFF. WINDS AND SEAS REMAIN ELEVATED ACROSS THE COASTAL
WATERS, AT LEAST THROUGH SATURDAY AT THIS POINT. THE OVERALL
PATTERN REMAINS ACTIVE ACROSS THE WEEKEND AND INTO EARLY NEXT
WEEK, AS ADDITIONAL SYSTEMS ARE EXPECTED TO MOVE ACROSS AREA
WATERS.
SEAS AT 13-16 FT THIS AFTERNOON WILL GRADUALLY DECREASE INTO THE
WEEKEND TO AROUND 10 FT. ADDITIONAL SYSTEMS EARLY IN THE WEEK WILL
LEAD TO ELEVATED SEAS ACROSS THE COASTAL WATERS. 29/62
HYDROLOGY
A WEATHER SYSTEM CONTINUES TO MOVE EAST OF THE CASCADES
THIS AFTERNOON. 12 HOUR QPF AMOUNTS IN THE MOUNTAINS RANGE 0.50-1.0"
WITH UP TO 2" IN THE CASCADES OF LEWIS COUNTY AND THE OLYMPICS.
ADDITIONAL PRECIPITATION WILL CONTINUE AT TIMES FRIDAY INTO
SATURDAY, PARTICULARLY OVER THE CASCADES. HOWEVER, SNOW LEVELS WILL
FALL TO NEAR 1500 TO 2000 FEET ON FRIDAY, RESULTING IN SNOWFALL FOR
THE MOUNTAINS ABOVE THIS LEVEL.
ONGOING RIVER FLOODING CONTINUES FOR SELECT RIVERS OFF THE CASCADES
FROM KING COUNTY SOUTHWARDS. FOR RIVERS DOWNSTREAM OF DAMS, DAM
OPERATIONS TO MAINTAIN A SAFE FLOOD POOL FOR AREA DAMS COULD
MAINTAIN ELEVATED FLOW LEVELS OR THEY COULD RAISE OR LOWER LEVELS
DOWNSTREAM OF THE DAMS. DAM REGULATION CHANGE RAPIDLY.
ADDITIONAL RISES ON RIVERS ARE EXPECTED FRIDAY INTO SATURDAY,
ESPECIALLY FOR RIVERS IN LEWIS COUNTY, DUE TO THE ONGOING
PRECIPITATION. FOR THAT REASON, THE FLOOD WATCH HAS BEEN UPDATED TO
INCLUDE LEWIS COUNTY INTO THE WEEKEND. THE FLOOD WATCH REMAINS FOR
KING, PIERCE, THURSTON, AND GRAYS HARBOR COUNTY DUE TO ELEVATED
RIVER LEVELS, ESPECIALLY RIVERS DOWNSTREAM OF DAM OPERATIONS.
THE LANDSLIDE THREAT WILL REMAIN HIGH THROUGH AT LEAST FRIDAY.
JD
SEW WATCHES/WARNINGS/ADVISORIES
WA...WIND ADVISORY UNTIL 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 STORM WARNING FROM 4 AM FRIDAY TO 4 PM PST SATURDAY 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 SATURDAY MORNING 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.
PZ...SMALL CRAFT ADVISORY UNTIL 4 PM PST FRIDAY FOR GRAYS HARBOR
BAR.
GALE WARNING UNTIL 4 AM PST FRIDAY FOR CENTRAL U.S. WATERS
STRAIT OF JUAN DE FUCA-EAST ENTRANCE U.S. WATERS STRAIT
OF JUAN DE FUCA-WEST ENTRANCE U.S. WATERS STRAIT OF JUAN
DE FUCA.
SMALL CRAFT ADVISORY UNTIL 4 AM PST FRIDAY FOR ADMIRALTY INLET-
NORTHERN INLAND WATERS INCLUDING THE SAN JUAN ISLANDS-
PUGET SOUND AND HOOD CANAL.
SMALL CRAFT ADVISORY UNTIL 10 PM PST FRIDAY 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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