166
FXUS66 KSEW 231704
AFDSEW
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SEATTLE WA
904 AM PST TUE DEC 23 2025
SYNOPSIS
SLIGHTLY DRIER CONDITIONS ON TUESDAY, WITH LINGERING SHOWERS ALONG
THE COAST. A LOW PRESSURE SYSTEM IS EXPECTED TO MOVE NORTHWARD INTO
WESTERN WASHINGTON ON WEDNESDAY, BRINGING ANOTHER ROUND OF
PRECIPITATION AND THE POTENTIAL FOR STRONG WINDS. UNSETTLED
CONDITIONS WILL CONTINUE THURSDAY AND FRIDAY. DRIER CONDITIONS
FAVORED TO RETURN THIS WEEKEND INTO EARLY NEXT WEEK.
SHORT TERM /TODAY THROUGH THURSDAY/
THE ONLY FORECAST UPDATE THAT HAS BEEN MADE THIS MORNING WAS TO
REPLACE THE WIND ADVISORY WITH A HIGH WIND WATCH FOR THE
POTENTIAL FOR STRONG WINDS TOMORROW. THE REST OF THE FORECAST
DETAILS REMAIN VALID AND THE PREVIOUS FORECAST CAN BE FOUND
BELOW.
A LOW PRESSURE SYSTEM WILL SHIFT NORTHWARD FROM CALIFORNIA INTO
WESTERN WASHINGTON BRINGING ANOTHER ROUND OF LOWLAND RAIN, MOUNTAIN
SNOW, AND THE POTENTIAL FOR WIDESPREAD STRONG WINDS. SNOW LEVELS
WILL RISE WEDNESDAY MORNING TO 4500-5500 FT, WITH HIGHER VALUES OVER
THE CENTRAL AND SOUTHERN CASCADES. SNOW LEVELS WILL THEN GRADUALLY
DECREASE THROUGHOUT THE AFTERNOON TO AROUND 2500-3000 FT. LATEST
GUIDANCE FOR SNOW ACCUMULATIONS THROUGH THURSDAY MORNING RANGE
BETWEEN: 3-6 INCHES FOR RAINY PASS, 1-3 INCHES FOR STEVENS PASS, AND
AROUND 1 INCH FOR SNOQUALMIE PASS. THE LOWLANDS WILL GET AROUND 0.15-
0.25 INCHES OF RAIN, WHILE COASTAL REGIONS WILL GET AROUND 0.40-0.70
INCHES. IN ADDITION, ASTRONOMICAL TIDES WILL REMAIN HIGH THIS WEEK.
THE COMBINATION OF HIGH BACKGROUND TIDES AND THE LOW PRESSURE
SYSTEM MAY ALLOW FOR THE POTENTIAL FOR MINOR COASTAL FLOODING
IMPACTS FOR LOCATIONS ALONG THE SALISH SEA AND PUGET SOUND.
ONTO THE WIND FORECAST.. WHICH REMAINS ALMOST AS UNCERTAIN AS 24
HOURS AGO WHEN WRITING THE AM AFD. THE LARGER SCALE PATTERN
WILL BECOME MORE AMPLIFIED INTO WEDNESDAY WITH A DEEPENING UPPER
LOW OFFSHORE IN THE NE PACIFIC. SHORTWAVE ENERGY WILL ROTATE
NORTHWARDS ALONG THE EASTERN PERIPHERY OF THIS CLOSED LOW,
LEADING TO THE DEVELOPMENT OF A COMPACT LOW PRESSURE SYSTEM
ALONG THE CA COAST LATER TODAY. THIS MESO LOW WILL THEN TRACK
NORTHWARDS INTO WA/OR (OR JUST OFFSHORE) LATE TUESDAY THROUGH
WEDNESDAY. THERE CONTINUES TO REMAIN UNCERTAINTY IN BOTH THE
TRACK AND MAGNITUDE OF THIS MESO-LOW, PARTICULARLY ONCE IT
REACHES OR/WA. THIS UNCERTAINTY CAN BE SEEN WELL IN THE GLOBAL
GUIDANCE, I.E. THE EPS/GEFS ENSEMBLE LOW LOCATIONS. NEARLY EVERY
INDIVIDUAL 00Z GEFS ENS. MEMBER KEEPS THE LOW TRACK ALONG THE
OR/WA COAST ON WEDNESDAY, WITH HIGH PROBABILITIES (80-90%) OF
SUB 990 MB MSLP OFFSHORE OF GRAYS HARBOR COUNTY BY 18Z WED. ON
THE OTHER HAND, THE EPS TRACKS THE LOW FARTHER INLAND, WITH LESS
THAN 20% PROBABILITIES OF SUB 990MB MSLP ANYWHERE OVER WA AT
18Z. THE EPS SOLUTION LEADS TO A SIGNIFICANT REDUCTION IN THE
WIND THREAT FOR WESTERN WASHINGTON, WITH ONLY APPROX. 15% OF
ENSEMBLE MEMBERS SHOWING WIND ADVISORY GUSTS ON WEDNESDAY. DUE
TO THE TIMEFRAME DRAWING CLOSER, WE'RE ALSO ABLE TO INVESTIGATE
HI-RES GUIDANCE, INCLUDING REFS/HREF. THERE IS A STRONGER SIGNAL
IN BOTH OF THESE ENSEMBLES FOR A WINDIER SOLUTION.
PROBABILITIES OF GUSTS EXCEEDING 45 MPH ON HREF RANGE 60 TO 80%
FOR PUGET SOUND, WITH SLIGHTLY HIGHER PROBS ON REFS.
PROBABILITIES GENERALLY LOWER FOR THE OLYMPIC PENINSULA, RANGING
30 TO 50%. DESPITE HIGHER PROBS, A FURTHER LOOK INTO THE HI-RES
DATA REVEALS SIGNIFICANT UNCERTAINTY AS WELL. BELOW IS THE 10TH
TO 90TH WIND GUST DATA FOR SEATTLE, BELLINGHAM, AND OLYMPIA ON
WEDNESDAY AFTERNOON FROM REFS:
SEATTLE: 16 MPH (10TH) TO 60 MPH (90TH)
BELLINGHAM: 11 MPH (10TH) TO 73 MPH (90TH)
OLYMPIA: 20 MPH (10TH) TO 62 MPH (90TH)
THIS FURTHER DEMONSTRATES THE WIDE RANGE OF POSSIBILITIES OF THE
WINDS ON WEDNESDAY, DESPITE THE EVENT BEING LESS THAN 42 HOURS
OUT. WITH ALL THAT SAID, HAVE DECIDED TO HOST WIND ADVISORIES
FOR NUMEROUS LOCATIONS ON WEDNESDAY. GIVEN THE HIGHER
PROBABILITIES OF REFS/HREF, ALONG WITH A SIGNAL ON UW WRF
ENSEMBLES, HAVE FOCUSED THE WIND ADVISORY ON THE INTERIOR
AREAS, PRIMARILY PUGET SOUND. THESE AREAS ALSO OVERLAP WITH THE
HIGHEST PROBABILITIES OF HIGHER GUSTS ON EPS (ALBEIT
SIGNIFICANTLY LOWER PROBABILITIES THAN REFS/HREF). HAVE SLIGHTLY
HIGHER CONFIDENCE IN BREEZY WINDS GENERALLY FROM EVERETT
SOUTHWARDS (GIVEN THE ONGOING EPS SOLUTIONS), BUT THE HIGH-END
SCENARIOS AND ELEVATED PROBABILITIES GAVE CREDENCE TO MORE
WIDESPREAD WIND ADVISORY FOR THE INTERIOR. WILL NEED TO
CONTINUE TO MONITOR THE OLYMPIC PENINSULA TODAY IF FURTHER
HEADLINES ARE REQUIRED. IN ADDITION, AS NOTED ABOVE, EXPECT THE
FORECAST TO CHANGE EVEN OVER THE NEXT 36 HOURS, AND IT WILL BE
CRITICAL TO MONITOR THE FORECAST FROM TRUSTED SOURCES. JD
ANOTHER ROUND OF PRECIPITATION IS EXPECTED THURSDAY, AS ANOTHER
SYSTEM MOVES NORTHWARD INTO WESTERN WASHINGTON, BRINGING
ADDITIONAL LIGHT PRECIPITATION TO THE REGION.
LONG TERM /THURSDAY NIGHT THROUGH MONDAY/
PRECIPITATION WILL CONTINUE THURSDAY NIGHT THROUGH FRIDAY, WITH
PRECIPITATION GRADUALLY TAPERING OFF FRIDAY EVENING. LONG-RANGE
ENSEMBLES ARE IN GOOD AGREEMENT FOR UPPER-LEVEL RIDGING TO BUILD
OVER WESTERN WASHINGTON THIS WEEKEND INTO EARLY NEXT WEEK, WHICH
WILL BRING DRIER CONDITIONS TO THE REGION. SOLUTIONS DO START TO
DIFFER SLIGHTLY ON MONDAY ON THE UPPER LEVEL PATTERN, HOWEVER THE
MAJORITY OF ENSEMBLE MEMBERS FAVOR THE RIDGE TO PERSIST THROUGH
MONDAY. 29
AVIATION
CONDITIONS ARE WIDELY VFR THIS MORNING, WITH THE EXCEPTION OF
OLM AND PWT AS LOW STRATUS LINGERS AT THOSE TERMINALS. LIGHT
SOUTHEASTERLY WINDS WILL CONTINUE AS WELL, BECOMING NORTHEAST
THIS AFTERNOON. RAIN RETURNS TO ALL TERMINALS GENERALLY AFTER
06Z TONIGHT. ANOTHER ROUND OF FOG AND STRATUS IS LIKELY
OVERNIGHT AT OLM AND PWT. STRONG WINDS ARE IN THE FORECAST
TOMORROW, AS A STRONG SOUTHERLY WIND IS DEVELOPING ASSOCIATED
WITH A FRONTAL SYSTEM.
KSEA...VFR TO PERSIST THROUGHOUT THE DAY TODAY. PRESENTLY, A LIGHT
SOUTHEASTERLY WIND IS ONGOING AROUND 6 KTS, BUT WILL LIKELY
TRANSITION TO A NORTHEASTERLY AROUND 00Z. WIND SPEEDS WILL BE
SLIGHTLY HIGHER, BETWEEN 7-9 KTS THROUGH THE EVENING. POTENTIAL IS
GROWING TOMORROW FOR A HIGH WIND EVENT WITH STRONG SOUTHERLY WINDS.
EXPECT AN INCREASE IN SUSTAINED WINDS BY THE END OF THE PRESENT TAF
PERIOD, WITH GUSTS OF UP TO 35 TO 40 KTS TO BE INTRODUCED IN
SUBSEQUENT FORECASTS.
21
MARINE
A POST FRONTAL AIRMASS CONTINUES THIS MORNING OVER
WESTERN WASHINGTON, WITH WEAK ONSHORE FLOW. A BRIEF PERIOD OF
SOUTH WINDS FOR THE EASTERN STRAIT OF JUAN DE FUCA THIS MORNING
MAY RESULT IN BRIEF GUSTS TO 25 KT. OTHERWISE, WINDS WILL TAPER
OFF THIS AFTERNOON INTO THIS EVENING.
EAST TO NORTHEAST WINDS WILL INCREASE LATE TONIGHT INTO
WEDNESDAY MORNING. THIS MAY RESULT IN SCA WINDS FOR PORTIONS OF
THE NORTHERN INLAND WATERS, AS WELL AS THE WESTERN STRAIT OF
JUAN DE FUCA AND NORTHERN COASTAL WATERS. A STRONGER WEATHER
SYSTEM THEN LOOK TO MOVE NORTHWARDS TOWARDS THE WATERS ON
WEDNESDAY. CONSIDERABLE UNCERTAINTY REMAINS IN THE FORECAST FOR
WEDNESDAY, PARTICULARLY IN REGARDS TO THE TRACK OF THE MIDWEEK
SYSTEM. WITH THAT SAID, PROBABILITIES OF GALE FORCE WIND GUSTS
REMAIN ELEVATED (GENERALLY 60 TO 90 PERCENT) FOR THE INTERIOR
WATERS AND MAJORITY OF THE COASTAL WATERS. FOR THAT REASON, HAVE
ISSUED A GALE WATCH FOR THESE AREAS WEDNESDAY. HOWEVER, DUE TO
THE CONTINUED UNCERTAINTY, IT WILL BE CRITICAL TO MONITOR THE
FORECAST THROUGH MIDWEEK FOR ANY INCREASE OR DECREASE TO THE
FORECAST. A BROAD SURFACE TROUGH WILL TO THE SOUTHWEST OF THE
AREA AND HIGH PRESSURE OVER INTERIOR BRITISH COLUMBIA WILL LEAD
TO ANOTHER PERIOD OF NORTHERLY FLOW ON THURSDAY INTO FRIDAY.
SEAS WILL RANGE 8 TO 13 FEET INTO THIS AFTERNOON, BEFORE
SUBSIDING BELOW 10 FEET TONIGHT INTO WEDNESDAY. SEAS MAY BRIEFLY
APPROACH 10 FEET WEDNESDAY AFTERNOON INTO WEDNESDAY NIGHT, BUT
GENERALLY ARE EXPECTED TO REMAIN BELOW 10 FEET THROUGH THURSDAY.
JD
HYDROLOGY
RIVERS ACROSS WESTERN WASHINGTON CONTINUE TO TREND DOWNWARD AS
PRECIPITATION ACROSS THE REGION LIGHTENS UP. THE SKOKOMISH
RIVER IS THE ONLY RIVER TO REMAIN IN FLOOD STAGE UNTIL
WEDNESDAY.
ADDITIONAL RAINFALL THROUGHOUT THE WEEK IS NOT EXPECTED TO CAUSE
ANY ADDITIONAL RISES TO AREA RIVERS, AND FLOODING OUTSIDE OF THE
SKOKOMISH RIVER IN MASON COUNTY IS NOT EXPECTED OVER THE NEXT 7
DAYS.
ADDITIONALLY, THE THREAT OF LANDSLIDES HAS DECREASED ACROSS
WESTERN WASHINGTON.
JD/15
SEW WATCHES/WARNINGS/ADVISORIES
WA...HIGH WIND WATCH FROM WEDNESDAY MORNING THROUGH WEDNESDAY
EVENING FOR CITY OF SEATTLE-DOWNTOWN EVERETT / MARYSVILLE
AREA-EASTERN KITSAP COUNTY-EASTSIDE-FOOTHILLS AND VALLEYS
OF PIERCE AND SOUTHERN KING COUNTIES-FOOTHILLS AND
VALLEYS OF THE NORTH CASCADES-GRAYS HARBOR COUNTY COAST-
ISLAND COUNTY-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-LOWLANDS OF WESTERN
WHATCOM COUNTY-MIDDLE CHEHALIS RIVER VALLEY-NORTHERN HOOD
CANAL-NORTHERN WASHINGTON COAST-OLYMPIA AND SOUTHERN
PUGET SOUND-PORT TOWNSEND AREA-SAN JUAN COUNTY-SHORELINE
/ LYNNWOOD / SOUTH EVERETT AREA-WILLAPA AND BLACK HILLS.
PZ...SMALL CRAFT ADVISORY UNTIL 1 PM PST THIS AFTERNOON FOR EAST
ENTRANCE U.S. WATERS STRAIT OF JUAN DE FUCA-GRAYS HARBOR
BAR.
SMALL CRAFT ADVISORY UNTIL 10 AM PST THIS MORNING FOR WEST
ENTRANCE U.S. WATERS STRAIT OF JUAN DE FUCA.
GALE WATCH FROM WEDNESDAY MORNING THROUGH WEDNESDAY EVENING
FOR EAST ENTRANCE U.S. WATERS STRAIT OF JUAN DE FUCA.
GALE WATCH FROM WEDNESDAY MORNING THROUGH WEDNESDAY EVENING
FOR ADMIRALTY INLET-NORTHERN INLAND WATERS INCLUDING THE
SAN JUAN ISLANDS-PUGET SOUND AND HOOD CANAL.
SMALL CRAFT ADVISORY UNTIL 7 AM PST WEDNESDAY 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.
GALE WATCH FROM WEDNESDAY MORNING THROUGH WEDNESDAY EVENING
FOR 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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