875
FXUS66 KSEW 221756
AFDSEW
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SEATTLE WA
956 AM PST MON DEC 22 2025
SYNOPSIS
A FRONTAL SYSTEM WILL MOVE ACROSS WESTERN WASHINGTON
THIS AFTERNOON INTO TONIGHT FOR INCREASING PRECIPITATION AND
BREEZY WINDS. A BRIEF BREAK IN PRECIPITATION IS POSSIBLE
TUESDAY. A STRENGTHENING SURFACE LOW TRACKING NORTHWARDS WILL
BRING WIDESPREAD PRECIPITATION ON WEDNESDAY, WITH THE POTENTIAL
FOR GUSTY WINDS. UNSETTLED WEATHER WILL CONTINUE THURSDAY INTO
LATE WEEK WITH TROUGHING OVER THE WESTERN US.
SHORT TERM /TODAY THROUGH WEDNESDAY/
THE LATEST FORECAST REMAINS ON TRACK WITH NO UPDATES THIS
MORNING. ANOTHER FRONTAL SYSTEM WILL APPROACH WESTERN
WASHINGTON OFFSHORE THIS MORNING, AND MOVE ACROSS THE AREA
MIDDAY THROUGH THIS EVENING. STEADIER PRECIPITATION WILL
INCREASE ALONG THE OLYMPIC PENINSULA MIDDAY, AND MOVE INTO THE
INTERIOR LATER THIS AFTERNOON. INCREASING SOUTHERLY WINDS
EXPECTED WITH THIS FRONTAL PASSAGE. WIND GUSTS ARE EXPECTED TO
RANGE 35 TO 45 MPH FOR THE COAST, AS WELL AS HOOD CANAL
NORTHWARDS. A WIND ADVISORY REMAINS IN EFFECT FOR THESE AREAS,
WITH GUSTS PEAKING THIS AFTERNOON. BREEZY CONDITIONS WILL EXIST
ELSEWHERE, WITH GUSTS RANGING 25 TO 40 MPH. LOCAL TREE LIMB
DAMAGE AND POWER OUTAGES ARE POSSIBLE. IN ADDITION TO THE WIND,
HEAVIER MOUNTAIN SNOWFALL WILL OCCUR WITH THE FRONT, WITH THE
HEAVIEST SNOWFALL AMOUNTS NEAR MT. BAKER. THE WINTER STORM
WARNING FOR THE NORTH CASCADES HAS BEEN EXTENDED THROUGH THIS
EVENING, WITH A WINTER WEATHER ADVISORY IN PLACE FOR THE
OLYMPICS. SNOW RATES WILL PEAK FOR THE CASCADE PASSES LATE
AFTERNOON THROUGH THIS EVENING, WITH 3 TO 6 INCHES OF SNOW FOR
SNOQUALMIE PASS. POST-FRONTAL SHOWERS WILL LINGER ON TUESDAY,
ESPECIALLY FOR THE OLYMPIC PENINSULA AND CASCADES, WITH A BRIEF
PERIOD OF DRIER WEATHER FOR THE INTERIOR.
THE NEXT SURFACE LOW THAT WILL IMPACT THE AREA IS EXPECTED TO
STRENGTHEN RAPIDLY OFFSHORE OF NORTHERN CALIFORNIA TUESDAY
NIGHT, AND TRACK NORTHWARDS ON WEDNESDAY. THIS SYSTEM WILL BE
ASSOCIATED WITH A DEEPENING UPPER TROUGH OFFSHORE OF THE
WESTERN US. THERE HAS BEEN A STEADY TREND IN 00Z/06Z ENSEMBLES
(PARTICULARLY IN GEFS/EPS) SHOWING A STRONGER SYSTEM IN THE
VICINITY OF WESTERN WASHINGTON BETWEEN 18Z WEDNESDAY-00Z
THURSDAY. THE 00Z EPS PROBABILITIES OF SUB 990MB MSLP PEAKS 18Z
WEDNESDAY NEAR UIL BETWEEN 70-80%, WITH PROBS AROUND 30-40% FOR
GEFS, BOTH AN INCREASE FROM THEIR PRIOR COUNTERPARTS ON 12Z
SUNDAY GUIDANCE. WITH THAT SAID, THERE CONTINUES TO REMAIN QUITE
A SPREAD IN EXTENT AND MAGNITUDE OF WINDS IN THE INDIVIDUAL
ENSEMBLE MEMBERS. FOR EXAMPLE.. THE 10-90TH PERCENTILE MAX WIND
GUSTS FOR SEA (FROM EPS) ON WEDNESDAY RANGE 7 TO 60 MPH, A
SPREAD OF 53 MPH FOR AN EVENT LESS THAN 72 HOURS OUT. THE
UNCERTAINTY CAN ALSO BE SEEN WELL ON THE UWWRF GFS ENSEMBLES,
RANGING FROM A SUB 985 MB LOW OFFSHORE OF WA/OR TO RELATIVELY
CALM WINDS DUE TO A WEAKER SYSTEM OR EASTWARD TRACK. GIVEN THE
HIGH LEVEL OF UNCERTAINTY, IT WILL REMAIN EXTREMELY IMPORTANT TO
MONITOR THE FORECAST OVER THE NEXT FEW DAYS, PARTICULARLY GIVEN
THE ANTECEDENT SOIL MOISTURE IF A WINDIER SOLUTION OCCURS.
DUE TO THE VARIABILITY IN GUIDANCE, UNCERTAINTY ALSO EXISTS AS
TO THE EXTENT OF QPF ON WEDNESDAY, AND THE SNOW LEVELS OVER THE
CASCADES. THE 25TH TO 75TH SPREAD ON NBM FOR SNOW LEVELS RANGE
2500 TO 4500 FEET OVER THE CENTRAL CASCADES DURING THE BULK OF
THE PRECIPITATION. WITH THAT SAID, THE RISK FOR ADDITIONAL SNOW
IS EXPECTED ON WEDNESDAY FOR ALL CASCADE PASSES, WITH TOTAL
SNOWFALL AMOUNTS GENERALLY UP TO 4" AT THIS TIME. THOSE
TRAVELING OVER THE CASCADE PASSES SHOULD CONTINUE TO MONITOR THE
FORECAST.
LONG TERM /WEDNESDAY NIGHT THROUGH SUNDAY/
THE AFOREMENTIONED SURFACE LOW WILL CONTINUE TO TRACK
NORTHWARDS AND WEAKEN INTO BRITISH COLUMBIA WEDNESDAY NIGHT.
ADDITIONAL PRECIPITATION, ALBEIT LIGHTER IN AMOUNTS, LOOKS TO
SPREAD NORTHWARDS INTO WESTERN WASHINGTON THURSDAY WITH
CONTINUED UNSETTLED WEATHER LATE WEEK DUE TO TROUGHING OFFSHORE.
SNOW LEVELS LOOK TO ALSO LOWER FRIDAY INTO SATURDAY,
PARTICULARLY NEAR THE BC BORDER AND CASCADE FOOTHILLS WITH
LINGERING SHOWERS. WEAK RIDGING THEN MAY BUILD INTO WESTERN
WASHINGTON NEXT WEEKEND, ALTHOUGH A TRANSITION TO MORE WESTERLY
FLOW MAY ALLOW FOR CONTINUED PRECIPITATION, ESPECIALLY FOR THE
MOUNTAINS AND NEAR BC. A COOLER AIRMASS IS LIKELY THURSDAY INTO
FRIDAY BEFORE SLIGHT WARMING NEXT WEEKEND.
JD
AVIATION
SOUTHWESTERLY FLOW WILL CONTINUE THROUGHOUT THE DAY TODAY AND
INTO TUESDAY AS AN UPPER LEVEL TROUGH ALONG THE CANADIAN COAST
DIGS DEEPER SOUTH. A SERIES OF SYSTEMS CIRCULATING THROUGH THIS
SYSTEM WILL BRING EBBS AND FLOWS TO SURFACE WINDS IN W WA FOR
THE FIRST HALF OF NEXT WEEK. THE NEXT OF WHICH WILL SEE WIND
SPEEDS INCREASING AND BECOMING GUSTY AROUND NOON OR JUST A
LITTLE BEFORE. FOR THE MORNING, WINDS ARE GENERALLY SOUTHERLY
WITH SPEEDS 5-10 KTS, HOWEVER SOME TERMINALS HAVE GONE TO LIGHT
AND VARIABLE AT TIMES THIS EARLY MORNING. ONCE SPEEDS INCREASE,
DIRECTION WILL REMAIN SOUTHERLY BUT SPEEDS RAMP UP TO 10-15 KTS
WITH GUSTS TO 25 KT. MORE WIND PRONE TERMINALS SUCH AS HQM AND
BLI COULD SEE EVEN GREATER SPEEDS RANGING 15-20 KTS WITH GUSTS
TO 30 KTS. STRONGEST WINDS WILL BE EXPECTED ALONG THE COAST, IN
THE SAN JUAN ISLANDS AND ALONG THE COAST OF WESTERN WHATCOM
COUNTY.
MAJORITY OF TERMINALS SHOWING VFR CONDITIONS THIS MORNING
ALTHOUGH THERE ARE ISOLATED PATCHES OF MVFR TO IFR CONDITIONS,
ESPECIALLY PWT AND OLM, WHICH ARE MORE PRONE TO LOWER CIGS AND
FOG. CIGS DO LOWER AS WINDS START TO RAMP UP IN ADVANCE OF
INCOMING SYSTEM BUT ARE EXPECTED TO REMAIN VFR INTO THE EARLY
AFTERNOON BEFORE LOWERING TO MVFR CONDITIONS AROUND OR A LITTLE
BEFORE SUNSET. NATURALLY, THIS IS WHEN PRECIP WILL RETURN TO THE
AREA. RAINS SHOULD BEGIN TO WRAP UP TONIGHT BETWEEN 10 PM PST
AND MIDNIGHT. AS THIS HAPPENS, WINDS EASE SLIGHTLY...ALLOWING
CIGS TO SINK A LITTLE BIT MORE BUT MOST LOCATIONS SHOULD REMAIN
MVFR INTO THE OVERNIGHT PERIOD.
KSEA...VFR CONDITIONS AT THE TIME OF THIS WRITING. ABOVE DISCUSSION
PERTAINING TO BOTH WINDS AND CIGS APPLIES. WINDS PICK UP AROUND 19Z
BUT REMAIN SOUTHERLY...RANGING 10-15 KTS WITH GUSTS UP TO 25 KTS.
CLOUDS WILL START TO FILL IN IN THE LATE MORNING WITH CIGS GENERALLY
3000-4000 FT BY NOON. FURTHER LOWERING AROUND 00Z INTO MVFR RANGE.
WINDS EASE AROUND 06Z, WHICH WILL ALLOW CIGS TO LOWER SLIGHTLY,
STILL REMAINING MID-RANGE MVFR.
18
MARINE
STRONGER WINDS WILL DEVELOP OVER THE WATERS AS THE NEXT SYSTEM
MOVES INTO THE AREA STARTING THIS MORNING. INHERITED GALE
WARNINGS AND SMALL CRAFT ADVISORIES LOOK GOOD AND REMAIN IN
EFFECT. THE FLOW WILL TURN NORTHERLY ON TUESDAY OR TUESDAY NIGHT
IN RESPONSE TO LOW PRESSURE OFF CALIFORNIA. THIS FEATURE MAY
PASS THROUGH WESTERN WASHINGTON ON WEDNESDAY. NORTH WINDS RETURN
ON THURSDAY AS ANOTHER LOW FORMS TO OUR SOUTH.
18/33
HYDROLOGY
RIVERS REMAIN ON A DOWNWARD TREND ALTHOUGH A HANDFUL OF RIVERS
COULD SEE SLIGHT RISES DUE TO RAINS ASSOCIATED WITH THE INCOMING
WEATHER SYSTEM TODAY. ANY RISES WILL FALL QUICKLY, POSSIBLY AS
EARLY AS TONIGHT BUT MORE LIKELY TUESDAY MORNING. THE ONLY RIVER
THAT WILL SEE FLOODING BEYOND TODAY IS THE SKOKOMISH RIVER IN
MASON COUNTY.
ADDITIONALLY, THE THREAT OF LANDSLIDES HAS DECREASED ACROSS
WESTERN WASHINGTON.
15
SEW WATCHES/WARNINGS/ADVISORIES
WA...COASTAL FLOOD ADVISORY UNTIL NOON PST TODAY FOR SAN JUAN
COUNTY.
WIND ADVISORY UNTIL 7 PM PST THIS EVENING FOR ISLAND COUNTY-
LOWLANDS OF WESTERN SKAGIT AND NORTHWESTERN SNOHOMISH
COUNTIES-LOWLANDS OF WESTERN WHATCOM COUNTY-PORT TOWNSEND
AREA-SAN JUAN COUNTY.
WINTER STORM WARNING UNTIL 10 PM PST THIS EVENING FOR CASCADES
OF WHATCOM AND SKAGIT COUNTIES.
WINTER WEATHER ADVISORY UNTIL 10 PM PST THIS EVENING FOR
OLYMPICS.
WIND ADVISORY UNTIL 4 PM PST THIS AFTERNOON FOR GRAYS HARBOR
COUNTY COAST-NORTHERN WASHINGTON COAST.
PZ...SMALL CRAFT ADVISORY FROM 1 PM THIS AFTERNOON TO 10 AM PST
TUESDAY FOR GRAYS HARBOR BAR.
SMALL CRAFT ADVISORY UNTIL 4 AM PST TUESDAY FOR ADMIRALTY
INLET-PUGET SOUND AND HOOD CANAL-WEST ENTRANCE U.S.
WATERS STRAIT OF JUAN DE FUCA.
SMALL CRAFT ADVISORY UNTIL 4 AM PST TUESDAY FOR CENTRAL U.S.
WATERS STRAIT OF JUAN DE FUCA.
GALE WARNING UNTIL 10 PM PST THIS EVENING 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 UNTIL 9 PM PST THIS EVENING FOR NORTHERN INLAND
WATERS INCLUDING THE SAN JUAN ISLANDS.
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