520
FXUS66 KSEW 181658
AFDSEW
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SEATTLE WA
958 AM PDT WED MAR 18 2026
SYNOPSIS
ATMOSPHERIC RIVER WILL REMAIN OVER WESTERN WASHINGTON THROUGH
FRIDAY. THE RIVER WILL MOVE OUT FRIDAY NIGHT. ZONAL FLOW ALOFT
OVER THE WEEKEND WITH A WEAK SYSTEM BRUSHING THE AREA. A WARM
FRONT WILL BRING STEADY RAIN BACK TO WESTERN WASHINGTON TUESDAY.
SHORT TERM /TODAY THROUGH FRIDAY/
THE LATEST FORECAST REMAINS ON TRACK WITH NO UPDATES THIS
MORNING. ATMOSPHERIC RIVER REMAINING AIMED AT MOST OF WESTERN
WASHINGTON THROUGH FRIDAY. THE RIVER WILL SAG SOUTH LATER TODAY
INTO TONIGHT. RAIN WILL REDEVELOP OVER THE SOUTHERN PORTION OF
THE AREA THIS AFTERNOON AND EVENING AND CONTINUE INTO FRIDAY.
THE RAIN SHADOW WILL ALSO GIVE WAY WITH SO MUCH MOISTURE IN THE
AIR MASS LATER THIS MORNING WITH RAIN AT TIMES FOR THE CENTRAL
PUGET SOUND INTO FRIDAY. EARLY MODEL RUNS INDICATED AN INCREASE
IN THE MOISTURE FRIDAY BUT THE CURRENT FORECAST HAS IVT VALUES
BETWEEN 500-700 KG/M/S UNTIL THE RIVER MOVES OUT OF THE AREA.
FRONTAL BOUNDARY STALLED TO THE NORTH THROUGH THE PERIOD KEEPING
BREEZY CONDITIONS AT TIME OVER THE NORTHWEST INTERIOR. SNOW
LEVELS BETWEEN 7000 AND 8500 FEET THROUGH FRIDAY. NOT MUCH
CHANGE IN TEMPERATURES WITH HIGHS IN THE MID 50S AND LOWS IN THE
MID 40S TO LOWER 50S. RECORD HIGH MINIMUM TEMPERATURES ARE
POSSIBLE TODAY.
FELTON
LONG TERM /FRIDAY NIGHT THROUGH TUESDAY/
COLD FRONT MOVING THROUGH FRIDAY EVENING BRINGING ABOUT AN END
TO THE ATMOSPHERIC RIVER. RAIN GIVING WAY TO SHOWERS WITH SNOW
LEVELS DROPPING QUICKLY DOWN TO AROUND 4000 FEET. BREEZY
CONDITIONS WITH THE FRONTAL PASSAGE.
LITTLE CHANGE IN THE MODEL SOLUTIONS FOR THE WEEKEND WITH ZONAL
FLOW ALOFT OVER WESTERN WASHINGTON AND A WEATHER SYSTEM MOVING
BY TO THE NORTH. THIS WILL KEEP A CHANCE OF SHOWERS IN THE
FORECAST. SNOW LEVELS CONTINUING TO DROP BOTTOMING OUT BETWEEN
1500 TO 2000 FEET SATURDAY NIGHT INTO SUNDAY MORNING. MOISTURE
WILL BE LIMITED KEEPING NEW SNOW AMOUNTS IN THE MOUNTAINS AT A
MINIMUM.
BEST CHANCE AT A COMPLETELY DRY DAY MONDAY WITH SOME WEAK UPPER
LEVEL RIDGING OUT AHEAD OF THE NEXT FRONTAL SYSTEM. TIMING ON
THIS FEATURE HAS SLOWED DOWN A LITTLE BUT THE WARM FRONT IS STILL
TIMED INTO THE AREA TUESDAY BRINGING RAIN BACK INTO THE
FORECAST. HIGHS NEAR 50 WITH MID 50S POSSIBLE MONDAY. LOWS WILL
COOL SIGNIFICANTLY BEHIND THE FRONT WITH THE COLDER LOCATIONS
BELOW FREEZING SUNDAY AND MONDAY MORNINGS. INCREASING CLOUDS
MONDAY NIGHT KEEPING LOWS IN THE MID 30S TO LOWER 40S.
FELTON
AVIATION
STRONG WESTERLY FLOW ALOFT WILL CONTINUE ACROSS WESTERN WASHINGTON
AS A MOIST AIR MASS CONTINUES TO FUNNEL RAIN INTO THE REGION AHEAD
OF A STALLED FRONTAL BOUNDARY OVER BRITISH COLUMBIA. A MIX OF MVFR
AND TEMPO IFR/LIFR CONDITIONS IN LIGHT TO MODERATE RAIN WILL PERSIST
THROUGH THE DAY AND LIKELY OVERNIGHT INTO THURSDAY AS WELL.
KSEA...MVFR CEILINGS IN LIGHT RAIN ARE EXPECTED THROUGH THE DAY WITH
TEMPO IFR THIS MORNING. SOME GUIDANCE IS SUGGESTING SOME BRIEF
IMPROVEMENT TO VFR LATE THIS AFTERNOON, BUT OVERALL CONFIDENCE IN
THIS OUTCOME IS LOW. SURFACE WINDS SOUTHERLY 5 TO 8 KNOTS RISING TO
8 TO 12 KNOTS THIS AFTERNOON.
27/41
MARINE
PERIODS OF SMALL CRAFT ADVISORY STRENGTH SOUTHERLIES WILL CONTINUE
ACROSS THE WATERS INTO LATE WEEK AS A STALLED FRONTAL BOUNDARY NORTH
OF VANCOUVER ISLAND EVENTUALLY SHIFTS SOUTHEASTWARD ON FRIDAY.
ONSHORE FLOW WILL DEVELOP BEHIND THE FRONT FRIDAY NIGHT INTO
SATURDAY THEN EASE OVER THE WEEKEND AS A BUILDING SURFACE RIDGE
OFFSHORE MOVES INLAND.
27
HYDROLOGY
ATMOSPHERIC RIVER OVER THE AREA STILL EXPECTED TO CAUSE
POSSIBLE FLOODING PROBLEMS FOR RIVERS FLOWING OUT OF THE
CASCADES FROM KING COUNTY NORTHWARD AND THE SKOKOMISH RIVER IN
MASON COUNTY. RAINFALL AMOUNTS FORECAST FOR THROUGH FRIDAY
EVENING, 4 TO 7 INCHES IN THE NORTH CASCADES, 3 TO 5 INCHES FOR
THE OLYMPICS AND THE COAST AND 1 TO 2 INCHES FOR THE INTERIOR.
SNOW LEVELS REMAINING IN THE 7000 TO 8500 FOOT RANGE.
FLOOD WARNINGS WERE ISSUED LAST NIGHT FOR THE SNOQUALMIE RIVER BOTH
NEAR THE FALLS AND AT CARNATION. FLOOD WARNINGS ARE ALSO IN EFFECT
FOR THE TOLT AND SKYKOMISH RIVERS AS OF THIS MORNING.
FLOOD WATCH FOR KING, SNOHOMISH, SKAGIT, WHATCOM AND MASON
COUNTIES REMAINING IN EFFECT. RAINFALL RATES IN THE MOUNTAINS
INCREASING LATER TODAY WITH FLOODING POSSIBLE ON BUT NOT LIMITED TO
THE FOLLOWING RIVERS SNOHOMISH, PILCHUCK, SKAGIT, NOOKSACK AND OF
COURSE THE FLOOD PRONE THURSDAY OR FRIDAY.
SEW WATCHES/WARNINGS/ADVISORIES
WA...FLOOD WATCH FROM 1 PM PDT THIS AFTERNOON THROUGH FRIDAY
AFTERNOON FOR CASCADES OF SNOHOMISH AND NORTHERN KING
COUNTIES-CASCADES OF SOUTHERN KING COUNTY-CASCADES OF
WHATCOM AND SKAGIT COUNTIES-CITY OF SEATTLE-DOWNTOWN
EVERETT / MARYSVILLE AREA-EASTSIDE-FOOTHILLS AND VALLEYS
OF CENTRAL KING COUNTY-FOOTHILLS AND VALLEYS OF PIERCE
AND SOUTHERN KING COUNTIES-FOOTHILLS AND VALLEYS OF
SNOHOMISH AND NORTHERN KING COUNTIES-FOOTHILLS AND
VALLEYS OF THE NORTH CASCADES-LOWLANDS OF PIERCE AND
SOUTHERN KING COUNTIES-LOWLANDS OF WESTERN SKAGIT AND
NORTHWESTERN SNOHOMISH COUNTIES-LOWLANDS OF WESTERN
WHATCOM COUNTY-SHORELINE / LYNNWOOD / SOUTH EVERETT AREA.
FLOOD WATCH THROUGH FRIDAY AFTERNOON FOR FOOTHILLS OF THE
WESTERN AND SOUTHERN OLYMPIC PENINSULA-MIDDLE CHEHALIS
RIVER VALLEY-OLYMPIA AND SOUTHERN PUGET SOUND-OLYMPICS-
SOUTHERN HOOD CANAL-WILLAPA AND BLACK HILLS.
PZ...SMALL CRAFT ADVISORY FROM NOON TODAY TO 5 PM PDT THURSDAY FOR
WEST ENTRANCE U.S. WATERS STRAIT OF JUAN DE FUCA.
SMALL CRAFT ADVISORY FROM 4 PM THIS AFTERNOON TO 5 PM PDT
THURSDAY FOR NORTHERN INLAND WATERS INCLUDING THE SAN
JUAN ISLANDS-PUGET SOUND AND HOOD CANAL.
SMALL CRAFT ADVISORY FROM 2 PM THIS AFTERNOON TO 5 PM PDT
THURSDAY FOR ADMIRALTY INLET.
SMALL CRAFT ADVISORY UNTIL 5 PM PDT THURSDAY FOR COASTAL
WATERS FROM CAPE FLATTERY TO JAMES ISLAND 10 TO 60 NM-
COASTAL WATERS FROM CAPE FLATTERY TO JAMES ISLAND OUT 10
NM-COASTAL WATERS FROM JAMES ISLAND TO POINT GRENVILLE 10
TO 60 NM-COASTAL WATERS FROM JAMES ISLAND TO POINT
GRENVILLE OUT 10 NM-COASTAL WATERS FROM POINT GRENVILLE
TO CAPE SHOALWATER 10 TO 60 NM-COASTAL WATERS FROM POINT
GRENVILLE TO CAPE SHOALWATER OUT 10 NM.
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