405
FXUS66 KSEW 200446
AFDSEW
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SEATTLE WA
846 PM PST FRI DEC 19 2025
SYNOPSIS
A SERIES OF WEATHER SYSTEMS MOVING ACROSS THE REGION WILL BRING
PERIODS OF LOWLAND RAIN, MOUNTAIN SNOW, AND BREEZY CONDITIONS
TO WESTERN WASHINGTON AT TIMES THROUGHOUT THE NEXT WEEK.
SHORT TERM /TONIGHT THROUGH SUNDAY NIGHT/
NO CHANGES TO THE FORECAST THIS EVENING. RIVERS ARE CONTINUING
TO FALL TONIGHT. SCATTERED SHOWERS PERSIST ACROSS THE AREA AND
WILL DO SO FOR THE NEXT FEW DAYS. 62
ACTIVE CONDITIONS ARE PERSISTING ACROSS WESTERN WASHINGTON THIS
EVENING. A SUBTLE SHORTWAVE, MOSTLY PREVALENT IN THE 700 MB
LEVELS IS CURRENTLY TRACKING INTO VANCOUVER ISLAND. IN IT'S WAKE
- SHALLOW CUMULUS IS OVER THE NE PAC INDICATIVE OF A CONVECTIVE
ENVIRONMENT. THUNDERSTORMS HAVE BEEN OBSERVED OVER THE OLYMPIC
PENINSULA SO FAR TODAY WITH A SLIGHT CHANCE (15%) REMAINING INTO
TONIGHT. MODERATE TO HEAVY MOUNTAIN SNOW IS ALSO IN THE OFFING
AS A WINTER STORM WARNING REMAINS IN EFFECT THROUGH SATURDAY
AFTERNOON.
A BROAD UPPER-TROUGH OVER THE GULF OF ALASKA WILL CONTINUE TO
STEER SHORTWAVES INTO THE REGION THROUGHOUT THE WEEKEND.
RAINFALL ISN'T EXPECTED TO BE HEAVY BUT 48-HOUR TOTALS ENDING
SUNDAY NIGHT WILL SEE THE LOWLANDS GETTING ANYWHERE BETWEEN
0.50-1.50" OF RAIN WITH LOWER TOTALS FOR AREAS IN THE RAIN
SHADOW LIKE PORT TOWNSEND, SEQUIM AND MOST OF WHIDBEY ISLAND.
MOUNTAIN AREAS BELOW SNOWLEVELS WILL SEE ANYWHERE BETWEEN
1.00-3.00" OF RAINFALL. ALTHOUGH RAINFALL WON'T BE HEAVY, THE
LANDSLIDE THREAT WILL CONTINUE TO BE EXPRESSED DUE TO MOISTURE -
LADEN SOILS. BREEZY SOUTHERLY WINDS ARE ALSO IN THE OFFING.
LONG TERM /MONDAY THROUGH FRIDAY/
ENSEMBLES AND DETERMINISTIC GUIDANCE ARE IN LOCK-STEP IN REGARDS
TO THE UPPER-LEVEL PATTERN FOR NEXT WEEK. THE AFOREMENTIONED
UPPER LEVEL TROUGH DIGGING ACROSS THE NORTHEASTERN PACIFIC WILL
CONTINUE TO SWING ADDITIONAL DISTURBANCES INTO THE REGION. AS A
RESULT, PERIODS OF LOWLAND RAIN AND MOUNTAIN SNOW WILL FOLLOW INTO
WESTERN WASHINGTON THROUGH MUCH OF THE NEXT WEEK ALONG WITH
BREEZY WINDS AT TIMES. THE WEATHER PATTERN WILL ALSO ALLOW FOR A
TREND TOWARDS COOLER TEMPERATURES, ESPECIALLY DURING THE
OVERNIGHT PERIOD, WHERE WE MAY START TO SEE MORNING LOWS
APPROACH FREEZING IN SPOTS BY MIDWEEK.
MCMILLIAN
AVIATION
WESTERLY FLOW ALOFT WILL CONTINUE INTO SATURDAY WITH
MORE ZONAL FLOW. VFR/MVFR CIGS CONTINUE THIS EVENING SCATTERED
SHOWERS ACROSS WESTERN WASHINGTON. CIGS WILL LOWER TO MORE
WIDESPREAD MVFR BETWEEN 07-10Z WITH MVFR CONTINUING FOR MOST SITES
THROUGH SATURDAY. THERE ALSO REMAINS A LOW PROBABILITY FOR IFR,
PRIMARILY AROUND KPWT (PROBABILITIES NEAR 30-40%). RAIN SHOWERS WILL
ALSO CONTINUE AT TIMES THROUGH SATURDAY, WITH A SLIGHT CHANCE (15-
20%) OF THUNDERSTORMS ALONG THE COAST. VSBYS MAY BRIEFLY DROP
TOWARDS 3-4 STATUTE MILES WITHIN HEAVIER SHOWERS. BREEZY S/SW
SURFACE WINDS THROUGH SATURDAY WITH CONTINUED ONSHORE FLOW.
KSEA...VFR/MVFR CIGS CONTINUE THIS EVENING. CONTINUOUS MVFR CIGS
EXPECTED GENERALLY FROM 07-08Z ONWARDS THROUGH SATURDAY AFTERNOON.
CIGS ARE EXPECTED TO PREDOMINANTLY RANGE BETWEEN 010-020 DURING THIS
PERIOD. THERE IS ALSO A 20-25% CHANCE OF IFR CIGS ON SATURDAY.
SCATTERED SHOWERS WILL CONTINUE THROUGH SATURDAY, PRIMARILY AFTER
18Z. BREEZY S/SW SURFACE WINDS THROUGH SATURDAY WITH GUSTS PEAKING
BETWEEN 20 TO 25 KTS. JD
MARINE
BREEZY WINDS WILL CONTINUE OVER AREA WATERS TODAY. A SMALL CRAFT
ADVISORY REMAINS IN EFFECT FOR THE COASTAL WATERS AND PUGET SOUND.
WITH GUST PROBABILITIES AT 70-90% OF EXCEEDING 21 KT, THE WEST AND
CENTRAL PORTIONS OF THE STRAIT OF JUAN DE FUCA HAVE BEEN INCLUDED IN
THE SMALL CRAFT ADVISORY AS WELL. IN ADDITION, THERE IS A SLIGHT
CHANCE (20-25%) OF THUNDERSTORMS THIS EVENING AND SATURDAY,
SPECIFICALLY OVER THE COASTAL WATERS AND WEST STRAIT.
A WEAKENING FRONTAL SYSTEM WILL MOVE OVER AREA WATERS ON SUNDAY. A
STRONGER SYSTEM IS SET TO FOLLOW ON MONDAY. AN ACTIVE WEATHER
PATTERN IS EXPECTED TO CONTINUE INTO NEXT WEEK.
SEAS WILL BE AROUND 10-12 FT TODAY AND CONTINUE TO SUBSIDE INTO THE
WEEKEND BELOW 10 FT BY SUNDAY EVENING. GUIDANCE HINTS AT SEAS
BUILDING TO 10-13 FT EARLY NEXT WEEK AS ADDITIONAL SYSTEMS ARE
EXPECTED TO MOVE OVER THE WATERS.
29
HYDROLOGY
A MAJORITY OF AREA RIVERS WILL CONTINUE A DOWNWARD TREND THROUGH THE
WEEKEND AS LIGHTER SHOWER ACTIVITY WILL CONTINUE ACROSS THE REGION.
WITH SNOW LEVELS AROUND 1500-2500 FEET AND PRECIPITATION TOTALS OF 1
TO 2 INCHES ACROSS THE LOWLANDS THROUGH THE WEEKEND, MOST RIVERS
WILL RECEDE TO WELL BELOW ACTION STAGE, WITH A FEW EXCEPTIONS:
* THE CHEHALIS RIVER AT PORTER WILL HOVER NEAR MINOR FLOOD STAGE FOR
THE NEXT FEW DAYS BEFORE RECEDING, WHILE THE UPSTREAM GAUGE AT
GRAND MOUND IS EXPECTED TO CREST LATER THIS EVENING.
* THE SKOKOMISH RIVER AT POTLATCH WILL REMAIN ELEVATED IN MINOR
FLOOD STAGE LIKELY THROUGH NEXT THURSDAY BEFORE RECEDING, BUT WILL
REMAIN IN ACTION STAGE THEREAFTER.
* THE COWLITZ RIVER AT RANDLE HAS CRESTED IN MINOR FLOOD STAGE AND
IS ON THE WAY DOWN THIS EVENING, WHILE THE RIVER REGULATED AT
MAYFIELD DAM WILL REMAIN NEAR MINOR FLOOD STAGE INTO THE WEEKEND.
REGULATED RIVERS MAY CONTINUE TO REMAIN ELEVATED OR INCREASE AS
RESERVOIRS AND DAM OPERATORS MANAGE THE WATER LEVELS. RIVER FLOWS
DOWNSTREAM OF DAMS MAY RISE OR LOWER RAPIDLY AS A RESULT. DAM
REGULATIONS CHANGE RAPIDLY TO ACCOUNT FOR INCOMING WATER, AND
ADDITIONAL FLOODING MAY OCCUR DOWNSTREAM, PARTICULARLY FOR THE
COWLITZ RIVER IN LEWIS COUNTY.
FOR THESE REASONS, THE FLOOD WATCH HAS BEEN CANCELLED FOR GRAYS
HARBOR AND THURSTON COUNTIES, AND WATER LEVELS FOR THESE AREAS ARE
EXPECTED TO GRADUALLY RECEDE OVER THE NEXT FEW DAYS.
THE LANDSLIDE THREAT WILL REMAIN HIGH THROUGH THE WEEKEND.
15
SEW WATCHES/WARNINGS/ADVISORIES
WA...WINTER STORM WARNING UNTIL 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-LOWLANDS OF LEWIS AND SOUTHERN THURSTON COUNTIES-
LOWLANDS OF PIERCE AND SOUTHERN KING COUNTIES-SHORELINE /
LYNNWOOD / SOUTH EVERETT AREA-WILLAPA AND BLACK HILLS.
PZ...SMALL CRAFT ADVISORY UNTIL 4 AM PST SATURDAY FOR GRAYS HARBOR
BAR.
SMALL CRAFT ADVISORY UNTIL 10 AM PST SATURDAY FOR CENTRAL U.S.
WATERS STRAIT OF JUAN DE FUCA-WEST ENTRANCE U.S. WATERS
STRAIT OF JUAN DE FUCA.
SMALL CRAFT ADVISORY UNTIL 4 PM PST SATURDAY 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-PUGET SOUND AND
HOOD CANAL.
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