720
FXUS66 KSEW 201618
AFDSEW
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SEATTLE WA
918 AM PDT WED MAY 20 2026
UPDATE
FORECAST ON TRACK THIS MORNING. MARINE LAYER ALREADY
ERODING ALONG THE EDGES WITH BREAKS IN THE OVERCAST. PILOT
REPORTS INDICATE LAYER IS LESS THAN 1000 FEET THICK. THIS
COMBINED WITH WEAKENING LOW LEVEL ONSHORE FLOW WILL RESULT IN A
SUNNY AFTERNOON. WARMER THURSDAY AND FRIDAY. ONSHORE FLOW
INCREASING OVER THE WEEKEND ESPECIALLY SUNDAY FOR MORE CLOUDS
AND COOLER TEMPERATURES. FIRST LOOK AT 12Z MODELS SHOW THE
POSSIBILITY OF THE SYSTEM FOR MEMORIAL DAY SLOWING DOWN A TOUCH
WHICH COULD HOLD THE RAIN OFF UNTIL EVENING FOR THE INTERIOR.
NO UPDATE THIS MORNING. PREVIOUS DISCUSSION FOLLOWS. FELTON
SYNOPSIS
HIGH PRESSURE ALOFT WILL BEGIN TO REBUILD ACROSS WESTERN
WASHINGTON TODAY AND REMAIN IN PLACE INTO FRIDAY FOR A RETURN
SUNNIER AND WARMER TEMPERATURES. THE RIDGE WILL WEAKEN OVER THE
HOLIDAY WEEKEND FOR A COOLING TREND. NEXT SYSTEM ARRIVING
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. STRATUS ACROSS
MUCH OF THE INTERIOR THIS MORNING IS BEGINNING TO ERODE ALONG
THE EDGES AND OVER THE OLYMPIC PENINSULA 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. N/NW WINDS 5-10 KT WILL PREVAIL THROUGH THE PERIOD,
BECOMING LIGHT N/NE OVERNIGHT.
KSEA...MVFR CONDITIONS THIS MORNING WITH IMPROVING CONDITIONS 19-
21Z. LIGHT/VARIABLE WIND BECOMING N/NW TO 10 KT THIS AFTERNOON,
BACKING TO LIGHT NE OVERNIGHT. VFR CONDITIONS TONIGHT.
33/62
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 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.
CLICK HERE TO GO TO PREVIOUS BULLETINS.
Main Text Page