746
FXUS66 KSEW 202231
AFDSEW
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SEATTLE WA
331 PM PDT WED MAY 20 2026
SYNOPSIS
UPPER LEVEL RIDGE CENTERED OFFSHORE BUILDING TONIGHT
AND REMAINING IN PLACE INTO FRIDAY. THE RIDGE WILL WEAKEN
SATURDAY. SURFACE HIGH PRESSURE OUT AHEAD OF AN APPROACHING
FRONT WILL INCREASE THE LOW LEVEL ONSHORE FLOW SUNDAY FOR
CLOUDIER AND COOLER WEATHER. NEXT SYSTEM ARRIVING MEMORIAL DAY.
ANOTHER UPPER LEVEL RIDGE WILL BUILD INTO BRITISH COLUMBIA
TUESDAY OR WEDNESDAY.
SHORT TERM /TONIGHT THROUGH FRIDAY NIGHT/
SATELLITE IMAGERY SHOWS SOME STRATO CUMULUS BANKED UP AGAIN THE
CENTRAL AND SOUTHERN CASCADES THIS AFTERNOON. ANOTHER AREA OF
STRATUS OVER THE OLYMPICS WITH MOSTLY CLEAR SKIES ELSEWHERE.
TEMPERATURES AT 3 PM/22Z WERE IN THE MID 50S TO MID 60S.
LOW LEVEL ONSHORE FLOW DECREASING OVERNIGHT WITH UPPER LEVEL
RIDGE BUILDING OFFSHORE. BY SUNRISE LIGHT FLOW IN THE LOWER
LEVELS WITH PATCHY FOG DEVELOPING IN THE FOG PRONE LOCATIONS
LIKE THE LOWER CHEHALIS AND SNOHOMISH RIVER VALLEYS. THE FOG
WILL BE SHALLOW AND DISSIPATE SOON AFTER SUNRISE. LOWS IN THE
40S.
UPPER LEVEL RIDGE BUILDING OFFSHORE, TEMPERATURES WARMING ALOFT
AND LIGHT FLOW IN THE LOWER LEVELS WILL GIVE WESTERN WASHINGTON
A WARMER DAY THURSDAY. PATCHY MORNING FOG AND STRATUS WILL BE
GONE BY MID MORNING. HIGHS IN THE MID TO UPPER 60S COAST AND 70S
TO LOWER 80S INLAND.
NOT MUCH CHANGE IN THE PATTERN THURSDAY NIGHT INTO FRIDAY. LOW
LEVEL ONSHORE FLOW A LITTLE STRONGER WITH STRATUS DEVELOPING
ALONG THE COAST SPREADING INLAND IN THE EARLY MORNING HOURS. THE
MARINE LAYER WILL BE SHALLOW AND NOT GET EAST OF PUGET SOUND.
UNDER SUNNY SKIES HIGHS AGAIN IN THE 70S TO LOWER 80S INLAND.
MORNING CLOUDS KEEPING HIGHS IN THE 60S ALONG THE COAST. LOWS
THURSDAY NIGHT IN THE MID 40S TO LOWER 50S.
UPPER LEVEL RIDGE OFFSHORE WEAKENING FRIDAY NIGHT WITH
INCREASING LOW LEVEL ONSHORE FLOW. STRATUS MAKING IT INTO THE
INTERIOR AROUND 12Z. LOWS IN THE MID 40S TO LOWER 50S. MINOR
HEATRISK BOTH THURSDAY AND FRIDAY. FELTON
LONG TERM /SATURDAY THROUGH WEDNESDAY/
FIRST TWO DAYS OF THE HOLIDAY WEEKEND LOOK DRY. STRATUS
DISSIPATING BACK TO THE COAST SATURDAY. MINOR HEATRISK
CONTINUES. UPPER LEVEL RIDGE OUT AHEAD OF AN APPROACHING FRONT
WILL INCREASE THE ONSHORE FLOW SUNDAY FOR MORE CLOUD COVER AND
COOLER TEMPERATURES.
MODELS HAVING A HARD TIME WITH THE TIMING OF THE NEXT SYSTEM.
OPERATIONAL RUNS HOLD OFF RAIN OVER THE INTERIOR UNTIL LATE
MONDAY. ENSEMBLES SHOW THIS SOLUTION IS IN THE MINORITY WITH A
MAJORITY OF THE ENSEMBLES WITH A FASTER EASTWARD PROGRESS OF
THE FRONT. THIS IS IN THE CURRENT FORECAST WITH A CHANCE OF RAIN
SUNDAY NIGHT AND RAIN SPREADING OVER THE AREA ON MEMORIAL DAY.
HIGHS IN THE 60S AND LOWER 70S SATURDAY LOWERING TO THE MID 50S
TO LOWER 60S MONDAY.
AVIATION
STRATUS IS CONTINUING TO SCATTER AND LIFT ACROSS THE SOUTHERN
PORTION OF THE CWA THIS AFTERNOON, GIVING WAY TO MOSTLY CLEAR SKIES
WITH SOME THIN HIGH CIRRUS OVERHEAD. VFR CONDITIONS ARE EXPECTED TO
PREVAIL FOR MOST THROUGH THE TAF PERIOD. THE EXCEPTION WILL BE THE
PACIFIC COAST WHERE THE MARINE LAYER WILL REFORM OVERNIGHT INTO
THURSDAY MORNING. STRATUS SHOULD BE MOSTLY CONFINED TO THE
COASTLINE, THROUGH THERE'S A LOW CHANCE IT COULD GET AS FAR EAST AS
SHN AND CLM (15-25% CHANCE). ELSEWHERE SHOULD REMAIN CLEAR (LESS
THAN 15% CHANCE OF MVFR OR LOWER). MOSTLY CLEAR SKIES WILL CONTINUE
TOMORROW WITH CIRRUS CLOUDS STREAMING OVERHEAD. WINDS NW 5-10 KT
WILL EASE AFTER SUNSET, BECOMING LIGHT NE OR VARIABLE OVERNIGHT.
WINDS ONCE AGAIN SWITCH TO NW 5-10 KT DURING THE DAY THURSDAY.
KSEA...VFR CONDITIONS THROUGH THE TAF PERIOD. STRATUS HAS NOW
DISSIPATED; HIGH CLOUDS REMAIN OVERHEAD. WINDS NW 8-10 KT BECOMING
NE AROUND 5 KT OVERNIGHT. WINDS THURSDAY RETURN TO NW 5-10 KT.
62
MARINE
HIGH PRESSURE WILL REMAIN SITUATED OFFSHORE THROUGH THE REST OF THE
WEEK, KEEPING NORTH/NORTHWEST WINDS PREVAILING ACROSS THE COASTAL
WATERS. DIURNALLY DRIVEN PUSHES THROUGH THE STRAIT OF JUAN DE FUCA
EACH AFTERNOON ARE EXPECTED, THOUGH THE WEAKEST DAY LOOKS TO BE
THURSDAY BEFORE THE WINDS REACH BACK UP TO SMALL CRAFT ADVISORY
THRESHOLDS. THE STRONGEST WINDS WILL REMAIN FARTHER OFFSHORE, BUT
OUT NEAR THE 60 NM BORDER WINDS MAY REACH UP TO 20-25 KT AT TIMES.
SMALL CRAFT CONDITIONS LOOK MORE PROBABLE FOR THE OUTER COASTAL
WATERS FRIDAY NIGHT INTO SATURDAY AS HIGH PRESSURE EDGES CLOSER
ONSHORE. THIS WILL ALSO ALLOW FOR STRONGER ONSHORE FLOW, WITH THE
STRONGEST BEING SATURDAY WHICH HAS THE POTENTIAL (30-50%) TO REACH
GALE FORCE THROUGH THE STRAIT OF JUAN DE FUCA. A FRONTAL SYSTEM
REMAINS ON TRACK TO TRAVERSE THE AREA ON MONDAY, WHICH WILL BRING
MORE WIDESPREAD SMALL CRAFT CONDITIONS TO MOST OF THE COASTAL AND
INTERIOR WATERS.
SEAS REMAIN AROUND 6 TO 8 FT THROUGH FRIDAY. SEAS LOOK TO PICK UP
AND STEEPEN WITH THE WINDS LATE FRIDAY INTO SATURDAY AND REACH NEAR
10 FT THROUGH THE OUTER COASTAL WATERS. SEAS THEN EASE ON SUNDAY
BEFORE THE INCOMING LOW PUSHES SEAS UP TO 10 TO 13 FT MONDAY INTO
TUESDAY.
62
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...NONE.
PZ...SMALL CRAFT ADVISORY UNTIL 11 PM PDT THIS EVENING FOR CENTRAL
U.S. WATERS STRAIT OF JUAN DE FUCA-EAST ENTRANCE U.S.
WATERS STRAIT OF JUAN DE FUCA.
CLICK HERE TO GO TO PREVIOUS BULLETINS.
Main Text Page