329
FXUS66 KSEW 152218
AFDSEW
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SEATTLE WA
318 PM PDT FRI MAY 15 2026
SYNOPSIS
A COLD UPPER LEVEL TROUGH WILL CONTINUE MOVING EAST INTO
WESTERN WASHINGTON THIS AFTERNOON AND REMAIN OVER THE AREA
THROUGH SATURDAY NIGHT. AN UPPER LEVEL RIDGE BUILDS OFFSHORE ON
SUNDAY, WITH WESTERN WASHINGTON REMAINING ON THE BACKSIDE OF
THE RIDGE THROUGH THE MIDDLE OF NEXT WEEK.
SHORT TERM /TONIGHT THROUGH SUNDAY NIGHT/
BROAD SHOWERS CONTINUE ACROSS WESTERN WASHINGTON THIS AFTERNOON.
THE FAIRLY EXTENSIVE CLOUD COVER. DESTABILIZATION COULD LEAD TO
THUNDERSTORM ACTIVITY TODAY WITH AT LEAST A 15-20% CHANCE OF
THUNDER AREA WIDE, MEANWHILE THE BEST CHANCES (25-35%) WILL BE
ALONG THE COAST AND INTO THE NORTH INTERIOR. LIGHTNING, SMALL
HAIL, AND BRIEF HEAVY DOWNPOURS WILL BE THE PRIMARY HAZARDS. A
WINTER WEATHER ADVISORY WAS ADDED FOR THE MOUNTAINS OF WESTERN
WASHINGTON ABOVE 4000 FEET. THIS WAS PUT OUT MAINLY AS A HEADS
UP FOR THOSE WITH OUTDOOR RECREATION PLANS TODAY THROUGH
SATURDAY NIGHT. SNOW SHOWERS AND THUNDERSTORMS CANNOT BE RULED
OUT. ROAD TRAVEL CONDITIONS COULD SEE MINOR TEMPORARY IMPACTS,
BUT GENERALLY GROUND TEMPERATURES WILL BE WARM ENOUGH TO LIMIT
ROAD ACCUMULATION.
WIDESPREAD CHANCES FOR THUNDER EXIST THROUGH SATURDAY, THOUGH THE
FOCUS OF THE CONVECTIVE POTENTIAL WILL SHIFT INTO THE CENTRAL
PUGET SOUND SOUTH THROUGH SW WASHINGTON (PEAKING IN THE 25-35%
RANGE). SHOWER COVERAGE THEN QUICKLY DECREASES INTO SUNDAY WITH
AN UPPER RIDGE BUILDING OFFSHORE. THE RIDGE AXIS WILL REMAIN FAR
ENOUGH AWAY, AND IN COMBINATION WITH LOWER-LEVEL MOISTURE, WILL
EXPECT TO SEE ABUNDANT CLOUD COVER THAT MAY BE A BIT PERSISTENT
THROUGH THE MORNING AND PERHAPS MIDDAY HOURS. AFTERNOON SUNSHINE
SHOULD RESULT, BRINGING HIGHS BACK TO THE LOWER TO MID 60S
SUNDAY.
LONG TERM /MONDAY THROUGH FRIDAY/
ENSEMBLE GUIDANCE REMAINS IN GOOD AGREEMENT WITH THE UPPER
LEVEL RIDGE REMAINING IN PLACE AT LEAST THROUGH TUESDAY.
DIFFERENCES IN THE MODEL SOLUTIONS BEGINNING WEDNESDAY WITH SOME
SOLUTIONS MOVING THE RIDGE INLAND OVER WESTERN WASHINGTON WHILE
OTHER SOLUTIONS KEEP THE RIDGE AXIS OFFSHORE. EITHER SCENARIO
KEEPS THE WEATHER DRY OVER THE AREA. THE RIDGE AXIS MOVING
OVERHEAD WOULD RESULT IN A LITTLE WARMER DAYS. FOR NOW WITH THE
UNCERTAINTY WILL KEEP HIGHS JUST A COUPLE OF DEGREES ABOVE
NORMAL WEDNESDAY AND THURSDAY, IN THE MID 60S TO LOWER 70S.
HIGHS MONDAY AND TUESDAY IN THE 60S. LOWS IN THE 40S THROUGH THE
PERIOD.
AVIATION
W/SW FLOW ALOFT THROUGH TONIGHT, VEERING TO THE NW SATURDAY MORNING
AND THEN MORE NORTHERLY LATE SATURDAY NIGHT. AT LOW LEVELS, S WINDS
FOR ALL BUT THE COAST, WHERE WINDS ARE W. SPEEDS RANGING 10-15 KTS
WITH GUSTS UP TO 25 KTS. WIDESPREAD RAIN SHOWERS (AND SLIGHT CHANCE
FOR THUNDERSTORMS) LEADING TO MVFR CEILINGS AND ISOLATED IFR.
SIMILAR CONDITIONS ARE IN STORE FOR TONIGHT INTO SATURDAY MORNING AS
RAIN SHOWERS PERSIST. GUSTS UP TO 20 KT ARE POSSIBLE FOR PUGET SOUND
TERMINALS UNTIL 10-12Z SUNDAY. LOW-END VFR AND MVFR IS IN STORE FOR
SUNDAY AS WELL AS SHOWERS MAINTAIN.
KSEA...LOW-END VFR AND MVFR CEILINGS HAVE BEEN OBSERVED SO FAR THIS
AFTERNOON WITH WIDESPREAD RAIN SHOWERS. SIMILAR CONDITIONS ARE
EXPECTED TONIGHT INTO SATURDAY. SOUTHWESTERLY WINDS 10-15 KTS WITH
GUSTS TO 25 KT WILL MAINTAIN BEFORE GRADUALLY EASING LATE TONIGHT.
FOR SATURDAY, HIRES ENSEMBLES CONSISTENTLY SHOWING THE DEVELOPMENT
OF A PSCZ SATURDAY AFTERNOON WITH A 40-50% CHANCE OF NORTHERLY WINDS
AT THE TERMINAL BY 22Z, AND HIGHER ODDS BY 00-01Z SUNDAY. IN
ADDITION, THERE IS 15 TO 20% CHANCE OF LIGHTNING WITH THE
CONVERGENCE ZONE THROUGH THE SAME PERIOD.
41
MARINE
A SYSTEM PASSING THROUGH THE AREA TONIGHT INTO SATURDAY
WILL ENHANCE WINDS AND SEAS OVER MOST AREA WATERS WITH SMALL CRAFT
ADVISORY CONDITIONS DEVELOPING OVER THE COASTAL WATERS AFTER
MIDNIGHT TONIGHT THEN THE STRAIT OF JUAN DE FUCA SATURDAY MORNING.
IN ADDITION THERE WILL BE A SLIGHT CHANCE OF THUNDERSTORMS FOR MOST
AREA WATERS OVERNIGHT INTO SATURDAY MORNING. ON SATURDAY SEAS OVER
THE COASTAL WATERS WILL BE NEAR OR ABOVE 10 FT, BECOMING STEEP
SATURDAY EVENING. PERSISTENT ONSHORE FLOW WILL RESULT IN DAILY
PUSHES OF THROUGH THE STRAIT OF JUAN DE FUCA INTO NEXT WEEK.
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 7 PM PDT THIS EVENING FOR PUGET
SOUND AND HOOD CANAL.
SMALL CRAFT ADVISORY FROM 11 PM THIS EVENING TO 11 PM PDT
SATURDAY FOR COASTAL WATERS FROM CAPE FLATTERY TO JAMES
ISLAND 10 TO 60 NM-COASTAL WATERS FROM JAMES ISLAND TO
POINT GRENVILLE 10 TO 60 NM-COASTAL WATERS FROM POINT
GRENVILLE TO CAPE SHOALWATER 10 TO 60 NM.
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