522
FXUS66 KSEW 182222
AFDSEW
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SEATTLE WA
322 PM PDT WED MAR 18 2026
SYNOPSIS
AN ATMOSPHERIC RIVER WILL CONTINUE TO BRING WARM AND
WET CONDITIONS TO WESTERN WASHINGTON THROUGH FRIDAY. WITH SNOW
LEVELS AROUND 7000-8000 FEET, RIVER FLOODING DUE TO HEAVY RAIN AND
SNOWMELT REMAINS POSSIBLE FOR MUCH OF THE CASCADES.
CONDITIONS WILL DRY OUT AND COOL DOWN OVER THE WEEKEND, WITH ANOTHER
WEATHER SYSTEM MOVING INTO THE REGION EARLY NEXT WEEK.
SHORT TERM /TONIGHT THROUGH FRIDAY NIGHT/
AN ATMOSPHERIC RIVER CONTINUES TO BRING PERIODS OF MODERATE TO HEAVY
RAINFALL TO WESTERN WASHINGTON ALONGSIDE MILD TEMPERATURES AND
PERIODS OF BREEZY SOUTHERLY WINDS. THE RAIN SHADOWING HAS HELD
STRONG EAST OF THE OLYMPIC MOUNTAINS, BUT WITH SUCH A MOIST AIR
MASS, MORE WIDESPREAD RAINFALL IS EXPECTED TO FILL IN ACROSS THE
REGION LATER TODAY. THE HEAVIEST RAIN WILL BE FOCUSED OVER THE
CASCADES FROM KING COUNTY NORTHWARDS, WHERE A FLOOD WATCH AND
SEVERAL FLOOD WARNINGS REMAIN IN EFFECT. A FLOOD WATCH ALSO REMAINS
IN EFFECT FOR MASON COUNTY, WHERE THE SKOKOMISH RIVER IS PROJECTED
TO REACH MINOR FLOOD STAGE. WITH SNOW LEVELS HOVERING AROUND 7000-
9000 FEET, ALMOST ALL OF THE PRECIPITATION OVER THE MOUNTAINS WILL
CONTINUE TO FALL AS RAIN. THE RAIN- ON-SNOW, AS WELL AS LOW
ELEVATION SNOWMELT, WILL CONTINUE TO CONTRIBUTE TO SIGNIFICANT
RUNOFF IN ADDITION TO THE INCOMING RAINFALL, AND THE RISK OF RIVER
FLOODING CONTINUES, PARTICULARLY FOR RIVERS RUNNING OFF OF THE THE
WEST SLOPES OF THE CASCADES. FOR MORE DETAILS, SEE THE HYDROLOGY
SECTION BELOW.
WARMER CONDITIONS WILL CONTINUE THROUGH FRIDAY, WITH FAIRLY STEADY
TEMPERATURES. HIGHS WILL REACH THE MID TO UPPER 50S FOR MOST AREAS,
WITH LOWS AROUND 50 DEGREES. A STALLED FRONTAL BOUNDARY TO THE NORTH
WILL ALSO MAINTAIN BREEZY SOUTHERLY WINDS ACROSS THE REGION THROUGH
FRIDAY, WITH GUSTS REACHING 20 TO 30 MPH.
LONG TERM /SATURDAY THROUGH WEDNESDAY/
A TRAILING COLD FRONT BEHIND THE ATMOSPHERIC RIVER SYSTEM WILL CROSS
WESTERN WASHINGTON ON FRIDAY EVENING, BRINGING AN END TO THE
ATMOSPHERIC RIVER. THE FRONTAL SYSTEM WILL ALSO BRING BREEZY WINDS
TO THE REGION, WITH A STRONG POST-FRONTAL WESTERLY PUSH THROUGH THE
STRAIT OF JUAN DE FUCA. ENSEMBLES REMAIN IN GOOD AGREEMENT OVER
DRIER CONDITIONS HEADING INTO THE WEEKEND, WITH A FEW LINGERING SNOW
SHOWERS OVER HIGHER TERRAIN. ANOTHER STORM SYSTEM IS ON TRACK TO
MOVE INTO THE PACIFIC NORTHWEST TUESDAY, BRINGING A POTENTIAL RETURN
OF LOWLAND RAIN, MOUNTAIN SNOW, AND BREEZY WINDS.
15
AVIATION
STRONG WESTERLY FLOW WILL PERSIST THROUGH MUCH OF UPCOMING TAF
PERIOD. AN ATMOSPHERIC RIVER CONTINUES TO CHURN THROUGHOUT THE
REGION. WITH IT, LOW CEILINGS HAVE BEEN OBSERVED WITH MVFR/IFR
WIDESPREAD ACROSS AREA TERMINAL. THIS TREND WILL LIKELY PERSIST
TONIGHT INTO THURSDAY AS WIDESPREAD RAIN AND SHOWERS MAINTAIN.
SOUTHERLY SURFACE WINDS BREEZY AT TIMES WITH GUSTS UP TO 25 KT
FOR TERMINALS SUCH AS KBLI, KPAE AND KHQM THROUGHOUT THE PERIOD
AS WELL.
KSEA...
MVFR CIGS THROUGHOUT MUCH OF THE UPCOMING PERIOD. RAIN SHOWERS
MAY LOWER VIS AT TIMES AS WELL. SURFACE WINDS MAINLY OUT OF THE
SOUTH WITH GUSTS UP TO 20 KT, MOSTLY THROUGH 00Z THURSDAY.
41
MARINE
PERIODS OF SMALL CRAFT SOUTHERLIES WILL CONTINUE ACROSS THE WATERS
LATE INTO THE WEEK AS A FRONTAL SYSTEM REMAINS STALLED OVER
VANCOUVER ISLAND. THE FRONTAL SYSTEM WILL MOVE OVER AREA WATERS ON
FRIDAY, WITH A WESTERLY PUSH THROUGH THE STRAIT OF JUAN DE FUCA
EXPECTED TO REACH SMALL CRAFT STRENGTH. WINDS WILL EASE INTO THE
WEEKEND AS A BUILDING SURFACE RIDGE OFFSHORE MOVES INLAND.
SEAS AROUND 6 TO 9 FEET WILL EASE TO 5 FEET OR BELOW OVER THE
WEEKEND.
15
HYDROLOGY
AN ATMOSPHERIC RIVER WILL CONTINUE TO BRING STEADIER
RAINFALL OVER PORTIONS OF WESTERN WASHINGTON THROUGH FRIDAY.
ADDITIONAL RAINFALL AMOUNTS THROUGH FRIDAY EVENING RANGE FROM 4 TO 6
INCHES FOR THE CASCADES OF NORTHERN KING COUNTY, AND NORTHWARDS.
ANOTHER 2 TO 5 INCHES OF RAINFALL ARE EXPECTED FOR THE OLYMPICS.
SNOW LEVELS WILL REMAIN BETWEEN 7000 TO 9000 FEET, RESULTING IN
FURTHER SNOW MELT IN THE MOUNTAINS.
FLOOD WARNINGS ARE CURRENTLY ONGOING ACROSS KING AND SNOHOMISH
COUNTIES. A FLOOD WATCH ALSO REMAINS IN EFFECT FOR KING, SNOHOMISH,
SKAGIT, WHATCOM, AND MASON COUNTIES. ADDITIONAL RIVER FLOODING IS
POSSIBLE ON, BUT NOT LIMITED TO, THE PILCHUCK, SKAGIT, NOOKSACK,
STILLAGUAMISH, AND THE FLOOD PRONE SKOKOMISH RIVER THROUGH FRIDAY.
RIVERS WILL SLOWLY RECEDE SATURDAY, AND CONTINUE TO RECEDE INTO
EARLY NEXT WEEK, WITH PREDOMINANTLY DRIER CONDITIONS OVER THE
WEEKEND. JD
SEW WATCHES/WARNINGS/ADVISORIES
WA...FLOOD WATCH 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-
FOOTHILLS OF THE WESTERN AND SOUTHERN OLYMPIC PENINSULA-
LOWLANDS OF PIERCE AND SOUTHERN KING COUNTIES-LOWLANDS OF
WESTERN SKAGIT AND NORTHWESTERN SNOHOMISH COUNTIES-
LOWLANDS OF WESTERN WHATCOM COUNTY-MIDDLE CHEHALIS RIVER
VALLEY-OLYMPIA AND SOUTHERN PUGET SOUND-OLYMPICS-
SHORELINE / LYNNWOOD / SOUTH EVERETT AREA-SOUTHERN HOOD
CANAL-WILLAPA AND BLACK HILLS.
PZ...SMALL CRAFT ADVISORY UNTIL 5 PM PDT THURSDAY FOR ADMIRALTY
INLET-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-
WEST ENTRANCE U.S. WATERS STRAIT OF JUAN DE FUCA.
SMALL CRAFT ADVISORY UNTIL 5 PM PDT THURSDAY FOR NORTHERN
INLAND WATERS INCLUDING THE SAN JUAN ISLANDS-PUGET SOUND
AND HOOD CANAL.
CLICK HERE TO GO TO PREVIOUS BULLETINS.
Main Text Page