485
FXUS66 KSEW 210940
AFDSEW
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SEATTLE WA
240 AM PDT THU MAY 21 2026
SYNOPSIS
HIGH PRESSURE ALOFT ACROSS WESTERN WASHINGTON TODAY AND REMAIN
INTO FRIDAY WITH SUNNIER AND WARMER CONDITIONS. THE RIDGE WILL
WEAKEN OVER THE HOLIDAY WEEKEND FOR A COOLING TREND LASTING INTO
EARLY NEXT WEEK. NEXT SYSTEM ARRIVING EARLY NEXT WEEK AS WELL.
SHORT TERM /TODAY THROUGH SATURDAY/
BROAD UPPER-LEVEL TROUGHING RESIDES OVER WESTERN CONUS WHILE AN
UPPER-RIDGE IS NOSING INTO BC AND W WA. MOSTLY CLEAR SKIES
ACROSS THE CWA THIS MORNING ASIDE FROM MARINE STRATUS ALONG
SECTIONS OF THE COAST AND SOUTHWEST INTERIOR. THIS ACTIVITY
ALONG WITH PATCHY RIVER VALLEY FOG WILL CONTINUE BEFORE BURNING
OFF AS THE MORNING PROGRESS. MOSTLY SUNNY SKIES TODAY AS LARGE-
SCALE SUBSIDENCE ENSUES. HIGH TEMPERATURES ARE FORECAST TO BE
ABOVE AVERAGE - IN THE 70S ACROSS THE INTERIOR WITH NEAR 80 F
THROUGHOUT THE CHEHALIS RIVER VALLEY. COASTAL AREAS TO REMAIN IN
THE 60S. OVERNIGHT LOWS WILL FALL INTO THE 40S AND LOWER 50S.
UPPER-RIDGING WILL FLATTEN ON FRIDAY AS ZONAL FLOW SWITCHES INTO
GEAR ON SATURDAY. TEMPERATURES WILL WARM INTO INTO THE 70S AGAIN
FOR BOTH FRIDAY AND SATURDAY BUT LOW-LEVEL ONSHORE FLOW WILL
ALSO BEGIN TO STRENGTHEN. COASTAL AREAS WILL SEE AFTERNOON HIGHS
IN THE 60S WITH LOWS IN THE 40S AND LOWER 50S AREA-WIDE.
LONG TERM /SATURDAY NIGHT THROUGH WEDNESDAY/
DETERMINISTIC GUIDANCE CONTINUE TO HOLD OFF RAIN OVER THE
INTERIOR UNTIL LATE MONDAY. HOWEVER, ENSEMBLES ARE MORE
PROGRESSIVE WITH AN EARLIER ARRIVAL OF THE FRONT LATE SUNDAY.
THIS IS IN THE CURRENT FORECAST WITH A CHANCE OF RAIN SUNDAY
NIGHT AND RAIN SPREADING OVER THE AREA ON MEMORIAL DAY. UPPER-
TROUGHING ON MONDAY/TUESDAY BEFORE ANOTHER RIDGE NOSES INTO THE
REGION TOWARDS MIDWEEK.
41
AVIATION
HIGH PRESSURE WILL BRING DRY AND STABLE CONDITIONS
TO WESTERN WA TODAY. THE FLOW ALOFT IS NORTHERLY. LOW LEVEL
STRATUS CLOUDS WILL FORM ALONG THE COAST THIS MORNING FOR MVFR
CONDITIONS. THE INTERIOR WILL REMAIN MOSTLY CLEAR AND VFR. 33
KSEA...VFR TODAY WITH N WIND TO 10 KT. 33
MARINE
ONSHORE FLOW WILL PREVAIL THIS WEEK WITH HIGH
PRESSURE OFFSHORE AND LOWER PRESSURE INLAND. EXPECT DIURNAL
WESTERLY PUSHES THROUGH THE STRAIT OF JUAN DE FUCA WITH HIGHEST
WIND AND WAVES DURING THE LATE AFTERNOON AND EVENING HOURS. 33
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 FROM 5 PM THIS AFTERNOON TO 5 AM PDT
FRIDAY FOR CENTRAL U.S. WATERS STRAIT OF JUAN DE FUCA-
EAST ENTRANCE U.S. WATERS STRAIT OF JUAN DE FUCA.
SMALL CRAFT ADVISORY FROM 2 PM THIS AFTERNOON TO 11 AM PDT
FRIDAY 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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