511
FXUS66 KSEW 162145
AFDSEW
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SEATTLE WA
245 PM PDT SAT MAY 16 2026
SYNOPSIS
A COLD UPPER LEVEL TROUGH WILL CONTINUE TO PASS THROUGH WESTERN
WASHINGTON THROUGH SUNDAY MORNING, MAINTAINING SHOWERS AND LIGHT
SNOW ABOVE 4000 FEET. AN UPPER LEVEL RIDGE WILL BUILD OFFSHORE
THEREAFTER, WITH WESTERN WASHINGTON REMAINING ON THE BACKSIDE OF
THE RIDGE THROUGHOUT MUCH OF NEXT WEEK.
SHORT TERM /TONIGHT THROUGH MONDAY NIGHT/
AN UPPER LEVEL LOW WILL CONTINUE TO TRAVERSE ACROSS WESTERN
WASHINGTON TODAY, MAINTAINING WIDESPREAD SHOWER ACTIVITY ACROSS
THE REGION. LATEST RADAR SHOWS A PUGET SOUND CONVERGENCE ZONE
OVER THE CENTRAL SOUND, WITH FORECAST MODELS SHOWING THE
CONVERGENCE ZONE SHOWERS PERSISTING THROUGH THE EVENING AND
SHIFTING SOUTHEASTWARD LATER THIS EVENING TOWARDS MOUNT
RAINIER. THESE CONVERGENCE SHOWERS ARE PRODUCING SEVERAL
LIGHTNING STRIKES ALONGSIDE LOCALLY HEAVY RAIN, PEA SIZED HAIL,
AND GUSTY WINDS. WITH MARGINAL INSTABILITY IN PLACE OVER THE
REGION, ISOLATED THUNDERSTORMS ARE ALSO FAVORED TO CONTINUE
OUTSIDE OF THE CONVERGENCE ZONE THIS AFTERNOON, PRIMARILY SOUTH
OF THE PUGET SOUND TOWARDS THE COAST, WITH SPOTTER REPORTS OF
ABUNDANT SMALL HAIL. WITH SNOW LEVELS NEAR 3500-4000 FEET AND
CONVERGENCE ZONE ACTIVITY EXPECTED TO CONTINUE OVER THE
MOUNTAINS INTO THE EVENING HOURS, A WINTER WEATHER ADVISORY
REMAINS IN EFFECT OVER THE CASCADES AND OLYMPICS.
THE UPPER LEVEL TROUGH WILL SHIFT SOUTHEASTWARD BY SUNDAY
MORNING, WITH AN UPPER LEVEL RIDGE BUILDING OFFSHORE. CONDITIONS
ACROSS MUCH OF WESTERN WASHINGTON WILL DRY OUT DESPITE A MOSTLY
CLOUDY MORNING AND SOME SUN BREAKS IN THE AFTERNOON. WRAP AROUND
MOISTURE MAY RESULT IN LINGERING SHOWER ACTIVITY ACROSS THE
NORTH CASCADES WITH LITTLE TO NO ACCUMULATION. COOLER
TEMPERATURES WILL CONTINUE ACROSS THE REGION ON SUNDAY, WITH
HIGHS PEAKING IN THE LOW 60S ACROSS MUCH OF THE LOWLANDS.
LOW CLOUDS ARE FAVORED TO DEVELOP ACROSS MUCH OF THE LOWLANDS
AGAIN INTO MONDAY MORNING AS HIGH PRESSURE BUILDS INTO THE
REGION. THE CLOUDS ARE FAVORED TO BREAK UP FOR MOST AREAS BY THE
AFTERNOON, WITH NEAR NORMAL TEMPERATURES AND MOSTLY DRY
CONDITIONS FOR MONDAY.
LONG TERM /TUESDAY THROUGH SATURDAY/
ENSEMBLES REMAIN IN GOOD AGREEMENT OVER HIGH PRESSURE REMAINING
SITUATED OFFSHORE THROUGH MUCH OF NEXT WEEK. A SERIES OF LOW
PRESSURE SYSTEMS WILL MOVE INLAND NEXT WEEK, BUT ARE FAVORED TO
SPLIT APART OR STAY NORTH OF THE WASHINGTON/CANADA BORDER.
CONDITIONS ACROSS WESTERN WASHINGTON ARE FAVORED TO REMAIN
MOSTLY DRY THROUGH THE FORECAST PERIOD WITH NEAR NORMAL
TEMPERATURES.
15
AVIATION
A TROUGH WITH A COLD FRONT WILL CONTINUE TO ADVANCE EAST OF THE
TERMINALS THIS AFTERNOON. THE FLOW BEHIND THE TROUGH ALOFT WILL
INCREASE FROM THE NORTH. SCATTERED SHOWERS CONTINUE POST-FRONT
ACROSS WESTERN WA WITH A CONVERGENCE ZONE TAKING SHAPE IN THE SOUTH
KITSAP AND FAR SOUTHERN KING COUNTY/PIERCE COUNTY AREAS. THERE
REMAINS A 30% CHANCE OF THUNDER WITH THIS ACTIVITY THROUGH EARLY
THIS EVENING. THREATS REMAIN LIGHTNING, SMALL HAIL, GUSTY VARIABLE
WINDS AND DOWNPOURS REDUCING VISIBILITIES. CLOUD TOPS OF
THUNDERSTORMS ARE LIKELY TO REMAIN LOW-TOPPED (BELOW 20,000 FT).
CEILINGS OUTSIDE OF SHOWERS WILL TREND TOWARDS VFR THROUGH THE REST
OF TODAY (WITH BRIEF MVFR AND ISOLATED IFR POSSIBLE WITH HEAVIER
SHOWERS). THE WINDS IN AND AROUND THE CONVERGENCE ZONE HAVE BECOME
NORTHERLY AROUND 10 KT, AND WILL FLIP BACK TO THE SOUTHWEST AROUND
02Z THIS EVENING. WINDS OUTSIDE OF THIS AREA WILL REMAIN OUT OF THE
SOUTHWEST-NORTHWEST 5-10 KT WITH A FEW GUSTS TO 20 KT FOR TERMINALS
NEAR WATERS. VFR/MVFR CEILINGS ARE LIKELY SUNDAY MORNING BEFORE
CLEARING IN THE AFTERNOON.
KSEA...CONVERGENCE ZONE (CZ) ACTIVITY TO CONTINUE IN AND SOUTH OF
THE TERMINAL THROUGH 02Z. THERE REMAINS A 30% CHANCE OF THUNDER WITH
THIS ACTIVITY THROUGH EARLY EVENING. VFR CEILINGS THROUGH THE
EVENING (WITH THE CHANCE OF MVFR WITH ANY SHOWER/STORM OVER THE
TERMINAL). MVFR IS LIKELY (60% CHANCE) SUNDAY MORNING BEFORE
CLEARING IN THE AFTERNOON. NORTH WINDS WITH THE CZ AT 10 KT WILL
SWITCH TO THE SOUTHWEST AROUND 02Z, DIMINISHING TO 6 KT OR LESS
THROUGH TONIGHT. ANOTHER SHIFT TO THE NORTH IS EXPECTED AFTER 18Z,
WITH WINDS UP TO 6 KTS.
HPR
MARINE
A TROUGH/FRONT MOVED THROUGH THE WATERS EARLIER THIS MORNING, WITH
ONSHORE FLOW INCREASING IN WAKE OF THE FRONT. SHOWERS AND A COUPLE
ISOLATED THUNDERSTORMS WILL CONTINUE ACROSS THE WATERS THIS
AFTERNOON AND EVENING, WITH THE HIGHEST THUNDER THREAT BEING IN THE
PUGET SOUND AREA. GUSTY WINDS WILL CONTINUE WITH THE ONSHORE FLOW
FOR THE COASTAL WATERS, STRAIT OF JUAN DE FUCA AND ADMIRALTY INLET.
THERE REMAINS A MEDIUM CHANCE OF A BRIEF GALE GUST IN THE EASTERN
SECTION OF THE STRAIT EARLY THIS EVENING. THE ONSHORE PUSH WILL
DIMINISH LATE TONIGHT/SUNDAY MORNING. THE PATTERN WILL REMAIN
ONSHORE AS HIGH PRESSURE BUILDS BACK OVER THE WATERS SUNDAY. ANOTHER
WEAK FRONT WILL PASS THROUGH MONDAY INTO TUESDAY. CONTINUAL PUSHES
OF WINDS DOWN THE STRAIT OF JUAN DE FUCA REMAIN LIKELY THROUGH
MIDWEEK.
SEAS OF 8-11 FT WILL CONTINUE IN THE COASTAL WATERS THROUGH EARLY
SUNDAY (WITH ROUGH BAR CONDITIONS). THEY WILL DROP BACK TO 6-8 FT
LATER SUNDAY THROUGH TUESDAY BEFORE INCREASING TO 8-10 FT WEDNESDAY,
AND THEN DROPPING TO 5-6 FT THROUGH THE END OF THE WEEK.
HPR
HYDROLOGY
THE DAILY HYDROLOGY DISCUSSION HAS ENDED UNTIL THE START OF THE
NEXT RAINY SEASON; IT WILL ONLY BE UPDATED DURING THIS TIME AS
NEEDED.
SEW WATCHES/WARNINGS/ADVISORIES
WA...WINTER WEATHER ADVISORY UNTIL 8 AM PDT SUNDAY 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-OLYMPICS.
PZ...SMALL CRAFT ADVISORY UNTIL 3 AM PDT SUNDAY FOR ADMIRALTY INLET-
CENTRAL U.S. WATERS STRAIT OF JUAN DE FUCA-EAST ENTRANCE
U.S. WATERS STRAIT OF JUAN DE FUCA-GRAYS HARBOR BAR.
SMALL CRAFT ADVISORY UNTIL MIDNIGHT PDT TONIGHT FOR WEST
ENTRANCE U.S. WATERS STRAIT OF JUAN DE FUCA.
SMALL CRAFT ADVISORY UNTIL 2 AM PDT SUNDAY 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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