406
FXUS66 KSEW 201035
AFDSEW
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SEATTLE WA
335 AM PDT WED MAY 20 2026
SYNOPSIS
HIGH PRESSURE ALOFT WILL BEGIN TO REBUILD ACROSS WESTERN
WASHINGTON ON WEDNESDAY AND REMAIN IN PLACE INTO FRIDAY FOR A
RETURN TO SOME SUNSHINE AND WARMER TEMPERATURES. THE RIDGE WILL
WEAKEN OVER THE UPCOMING HOLIDAY WEEKEND FOR A COOLING TREND AND
A CHANCE OF RAIN BY MEMORIAL DAY.
SHORT TERM /TODAY THROUGH FRIDAY/
BROAD UPPER-LEVEL TROUGHING RESIDES OVER WESTERN CONUS WHILE A
RIDGE CONTINUES TO REMAIN JUST OFFSHORE THE PNW. MID-HIGH LEVEL
CLOUD COVERAGE IS STREAMING OVERHEAD UNDER NORTHWEST FLOW AS
THE RIDGE AXIS STRETCHES WELL INTO NORTHERN BC. LOW STRATUS HAS
DEVELOPED AGAIN THIS MORNING ACROSS THE COAST, SOUTHWEST
INTERIOR AND PUGET SOUND. IT'LL BECOME MORE WIDESPREAD AS THE
MORNING PROGRESS BEFORE GIVING WAY TO HIGH CLOUDS AND FILTERED
SUNSHINE DURING THE AFTERNOON. HIGH TEMPERATURES ARE FORECAST TO
BE AROUND AVERAGE - IN THE 60S ACROSS THE INTERIOR WITH LOWER
70S THROUGHOUT THE CHEHALIS RIVER VALLEY. OVERNIGHT LOWS WILL
FALL INTO THE 40S.
UPPER-RIDGING IS LIKELY TO AMPLIFY ON THURSDAY BEFORE
FLATTENING ON FRIDAY. TEMPERATURES WILL WARM READILY INTO THE
70S TO NEAR 80 F ACROSS THE INTERIOR FOR BOTH THURSDAY AND
FRIDAY. COASTAL AREAS WILL SEE AFTERNOON HIGHS IN THE 60S WITH
LOWS IN THE 40S AREA- WIDE.
LONG TERM /FRIDAY NIGHT THROUGH TUESDAY/
ZONAL FLOW ALOFT BY FRIDAY NIGHT ALONG WITH MORE ONSHORE FLOW
TOWARDS THE WEEKEND. THIS SHOULD NOT ONLY BRING COOLER
TEMPERATURES, BUT ALSO INCREASE THE CHANCE FOR WIDESPREAD POPS
INTO EARLY NEXT WEEK. SUNDAY SHOULD FEATURE ADDITIONAL COOLING
AND CLOUD COVER WITH PRECIP CHANCES INCREASING AREAWIDE SUNDAY
NIGHT INTO MEMORIAL DAY.
41
AVIATION
HIGH PRESSURE IS ANCHORED OFFSHORE WITH N/NW FLOW
OVER WESTERN WA TODAY. THE LOW LEVEL FLOW REMAINS ONSHORE. THERE
ARE POCKETS OF MVFR CEILINGS ALONG THE COAST AND IN THE INTERIOR
THIS MORNING. THE TREND IS FOR IMPROVING CONDITIONS AND VFR BY
18-21Z IN THE INTERIOR AND 21-00Z ALONG THE COAST. LOW CLOUDS
WILL REFORM ALONG THE COAST OVERNIGHT. 33
KSEA...MVFR CONDITIONS THIS MORNING WITH IMPROVING CONDITIONS
18-21Z. LIGHT/VARIABLE WIND BECOMING N/NW TO 10 KT THIS
AFTERNOON. VFR CONDITIONS TONIGHT. 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. A
SYSTEM FRIDAY WILL BRING ELEVATED WINDS AND SEAS OVER THE
COASTAL WATERS. 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 UNTIL 5 AM PDT EARLY THIS MORNING FOR
CENTRAL U.S. WATERS STRAIT OF JUAN DE FUCA-EAST ENTRANCE
U.S. WATERS STRAIT OF JUAN DE FUCA.
SMALL CRAFT ADVISORY FROM 5 PM THIS AFTERNOON TO 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.
SMALL CRAFT ADVISORY UNTIL 11 AM PDT THIS MORNING 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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