754
FXUS66 KSEW 180622
AFDSEW
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SEATTLE WA
1022 PM PST WED DEC 17 2025
SYNOPSIS
A SERIES OF FRONTAL SYSTEMS WILL CONTINUE TO
PRODUCE UNSETTLED CONDITIONS ACROSS WESTERN WASHINGTON INTO
THROUGH EARLY NEXT WEEK WITH LOWLAND RAIN, MOUNTAIN SNOW, AND
BREEZY CONDITIONS AT TIMES.
UPDATE
THERE WERE UPDATES TO THE COASTAL FLOOD ADVISORY FOR SAN
JUAN COUNTY - IT GOES IN EFFECT FROM 4 AM TO 8 AM, AND ALSO NOW
INCLUDES THE PORT ANGELES AREA (SAME THREAT OF 1.5-2 FT OF
INUNDATION ALONG SHORELINES AND LOW-LYING COASTAL AREAS). THE WIND
ADVISORY WAS ALSO UPDATED TO START EARLIER IN THE NORTHWEST
INTERIOR, AS REFS/HREF GUIDANCE SHOWS WINDS PICKING UP EARLIER
TOMORROW MORNING FROM WHIDBEY ISLAND UP TO BELLINGHAM (INCLUDING THE
SAN JUANS, WESTERN WHATCOM/SKAGIT COUNTIES). REMAINDER OF THE
FORECAST IS ON TRACK BELOW.
HPR
SHORT TERM /TONIGHT THROUGH FRIDAY NIGHT/
RECENT RADAR
IMAGERY DEPICTS SCATTERED SHOWERS ACROSS MOST OF THE REGION, AS
POST FRONTAL SHOWERS CONTINUE FROM THE FRONTAL SYSTEM THIS
MORNING. LIGHT RAIN SHOWERS WILL CONTINUE OVER THE LOWLANDS
THROUGH THIS EVENING, ALONG WITH SNOW SHOWERS IN THE CASCADES.
HIGH TEMPERATURES THIS AFTERNOON HAVE BEEN IN THE MID TO UPPER
40S ACROSS THE REGION, BACK TO SEASONAL NORMALS. THIS LULL IN
ACTIVITY WILL BE BRIEF AS ANOTHER SYSTEM MOVES ACROSS WESTERN
WASHINGTON LATE TONIGHT INTO THURSDAY MORNING. THE BULK OF THIS
PRECIPITATION WITH THIS SYSTEM WILL BE AIMED TOWARDS NORTHWEST
OREGON, BUT IT WILL STILL GENERALLY BE ANOTHER WET DAY ACROSS
THE AREA, WITH RAIN TOTALS ACROSS THE LOWLANDS GENERALLY AROUND
0.25-0.75 INCHES, WITH LOCALLY HIGHER AMOUNTS MORE IN THE SOUTH
SOUND. FOR INFORMATION REGARDING RIVER FLOODING, SEE .HYDROLOGY
DOWN BELOW FOR MORE DETAILS.
LOCALLY WINDY CONDITIONS CAN BE EXPECTED ACROSS ALONG THE
COAST, ESPECIALLY WHIDBEY ISLAND NORTHWARD THROUGH BELLINGHAM,
AND GENERALLY SOUTH OF THE SOUND WITH INCREASING S/SW WINDS.
SNOW LEVELS GENERALLY 2500 TO 3000 FEET THIS AFTERNOON WILL
HOVER THIS EVENING AND INTO THE OVERNIGHT HOURS.. WITH SNOW
ACCUMULATIONS AROUND 5 TO 10 INCHES EXPECTED OVER THE CASCADES.
ADDITIONALLY, AS THIS SYSTEM MOVES OVER THE REGION, WARMER AIR
ALOFT WILL INCREASE SNOW LEVELS TO 6000 TO 7000 FEET BY LATE
THURSDAY MORNING INTO THE AFTERNOON, WHICH LEAVES A BRIEF TIME
WINDOW WHERE FREEZING RAIN COULD BE POSSIBLE. UNCERTAINTY EXISTS
IN HOW LONG THE WARM AIR LINGERS, AS SNOW LEVELS IMMEDIATELY
DROP DOWN TO 1500 TO 2000 FEET BY LATE THURSDAY EVENING,
TRANSITIONING THE RAIN MIX TO SNOW.
WE WILL SEE SNOW LEVELS REMAIN AT 1500 TO 2000 FEET THROUGH
FRIDAY AND INTO THE WEEKEND WHERE WE COULD SEE SIGNIFICANT
CONTINUOUS SNOWFALL IN THE MOUNTAINS, A GOOD THING IF YOU LIKE
TO SKI OR SNOWBOARD.
LONG TERM /SATURDAY THROUGH WEDNESDAY/
THE UNSETTLED WEATHER
PATTERN WILL CONTINUE INTO THE EARLY HALF OF NEXT WEEK, WHERE
WE WILL CONTINUE TO SEE LOWLAND RAIN, MOUNTAIN SNOW, AND AT
TIMES, BREEZY CONDITIONS ACROSS WESTERN WASHINGTON. TEMPERATURES
LOOK TO SETTLE RIGHT AROUND SEASONAL NORMALS DURING THIS
PERIOD, IN THE MID TO UPPER 40S ACROSS MOST OF THE REGION.
AVIATION
SCATTERED LIGHT RAIN WILL BE PRESENT ACROSS THE
REGION TO START THE TAF PERIOD WITH MVFR TO VFR CEILINGS. AHEAD
OF THE NEXT WEATHER SYSTEM, EXPECT MVFR CEILINGS TO FILTER INTO
ALL TERMINALS AND A BRIEF PERIOD OF REDUCED VISIBILITIES DUE TO
HEAVIER RAIN. THE FRONT AND WEATHER SYSTEM WILL PASS THROUGH THE
REGION BETWEEN 20Z AND 00Z THURSDAY, BRINGING RAIN, WIND, AND
REDUCED FLIGHT CONDITIONS. WINDS AHEAD OF THE FRONT WILL BE
SOUTHERLY AND BECOME WEST TO NORTHWESTERLY BEHIND THE FRONT. THE
GUSTIEST WINDS WILL BE ALONG THE FRONTAL BOUNDARY WITH GUSTS
GENERALLY BETWEEN 30 AND 40 KTS. HOWEVER, A GUST ABOVE 40 KTS
CANNOT BE COMPLETELY RULED OUT. WINDS DIMINISH SLIGHTLY BEHIND
THAT INITIAL PUSH BUT CEILINGS LARGELY REMAIN MVFR.
KSEA...CEILINGS ARE EXPECTED TO JUMP BETWEEN MVFR AND VFR THROUGH
08Z. AFTER 08Z, MVFR CEILINGS ARE FORECAST THE REMINDER OF THE TAF
PERIOD. THERE IS GOOD CONSENSUS THAT WINDS WILL INCREASE WITH GUSTS
AROUND 20 KTS FROM 14Z TO 17Z, FOLLOWED BY A PERIOD OF LIGHT WINDS,
REDUCED VISIBILITIES, AND RAIN AHEAD OF A FRONT. SOUTHWEST WINDS WILL
INCREASE QUICKLY AND GUST AROUND 35 KTS AS THE FRONT PUSHES THROUGH.
WINDS DIMINISH SLIGHTLY BEHIND THE FRONT WITH GUSTS AROUND 25 KTS
AND PREVAILING MVFR CEILINGS.
MARINE
WEAK HIGH PRESSURE WILL WEAKEN TONIGHT WITH ANOTHER
FRONTAL SYSTEM EXPECTED TO MOVE OVER AREA WATERS ON THURSDAY.
THIS SYSTEM WILL BRING ELEVATED WINDS AND SEAS, FOR WHICH
VARIOUS HEADLINES HAVE BEEN ISSUED. THE STRONGEST WINDS WILL BE
ALONG THE COASTAL WATERS AND EAST STRAIT WITH GUSTS UP TO 40-45
KT LIKELY, FOR WHICH A GALE WARNING IS SET TO GO INTO EFFECT
EARLY THURSDAY MORNING. HELD OFF ON UPGRADING THE SMALL CRAFT
ADVISORY TO A GALE WARNING FOR THE WESTERN STRAIT ON THURSDAY,
DUE TO LOW CONFIDENCE (30-40% CHANCE) OF EXCEEDING 34 KT GUSTS.
HOWEVER, CANNOT RULE OUT AN OCCASIONAL LOW- END GALE GUST AT
TIMES. SEAS WILL DECREASE SLIGHTLY TONIGHT TO 10-13 FT AND THEN
BUILD TO 11-15 FT BY LATE THURSDAY MORNING. ADDITIONAL SYSTEMS
ARE EXPECTED TO MOVE OVER AREA WATERS THIS WEEKEND AND INTO
EARLY NEXT WEEK.
HYDROLOGY
PRECIPITATION WILL CONTINUE AT TIMES THROUGH TONIGHT,
BEFORE ANOTHER WEATHER SYSTEM BRING ADDITIONAL, STEADIER
PRECIPITATION ON THURSDAY. SNOW LEVELS WILL REMAIN LOWER INTO
THURSDAY MORNING, AROUND 2500 TO 3000 FEET, BEFORE BRIEFLY RISING TO
5000 TO 7000 FEET THURSDAY AFTERNOON. SNOW LEVELS WILL THEN FALL TO
1500 FEET ON 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.
A FLOOD WATCH ALSO REMAINS IN EFFECT FOR SKAGIT, KING, PIERCE,
THURSTON, AND GRAYS HARBOR COUNTIES THROUGH FRIDAY AFTERNOON DUE TO
THE NEXT SYSTEM ON THURSDAY AND RIVERS CURRENTLY RUNNING HIGH. THE
FLOOD WATCH HAS BEEN CANCELLED FOR LEWIS, SNOHOMISH, AND WHATCOM
COUNTIES AS NO FURTHER FLOODING IS EXPECTED WITH THE ADDITIONAL
PRECIPITATION FROM THE NEXT WEATHER SYSTEM.
THE LANDSLIDE THREAT WILL REMAIN HIGH THROUGH AT LEAST FRIDAY. JD
SEW WATCHES/WARNINGS/ADVISORIES
WA...COASTAL FLOOD ADVISORY FROM 4 AM TO 8 AM PST THURSDAY FOR SAN
JUAN COUNTY.
WIND ADVISORY FROM 6 AM TO 11 PM PST THURSDAY 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 THURSDAY 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-CASCADES
OF WHATCOM AND SKAGIT COUNTIES-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 AND VALLEYS OF THE NORTH CASCADES-
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-LOWLANDS OF WESTERN
SKAGIT AND NORTHWESTERN SNOHOMISH 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 TO 7 PM PST THURSDAY 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 TO 1 PM PST THURSDAY FOR
EASTERN STRAIT OF JUAN DE FUCA.
PZ...SMALL CRAFT ADVISORY UNTIL 6 PM PST THURSDAY FOR GRAYS HARBOR
BAR.
SMALL CRAFT ADVISORY UNTIL 4 PM PST THURSDAY 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 THURSDAY 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 TO 10 PM PST THURSDAY FOR EAST ENTRANCE
U.S. WATERS STRAIT OF JUAN DE FUCA.
GALE WARNING FROM 4 AM TO 4 PM PST THURSDAY 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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