923
FXUS66 KSEW 192317
AFDSEW
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SEATTLE WA
417 PM PDT THU MAR 19 2026
SYNOPSIS
AN ATMOSPHERIC RIVER REMAINS SITUATED OVER WESTERN
WASHINGTON WITH CONTINUED RAINFALL AND WARMER TEMPERATURES. A
COLD FRONT WILL PROGRESS THROUGH THE AREA ON FRIDAY. ZONAL FLOW
ALOFT OVER THE WEEKEND WITH A WEAK SYSTEM MOVING BY TO THE
NORTH ON SUNDAY. ANOTHER SYSTEM ARRIVES ON TUESDAY WITH
PRECIPITATION THROUGH WEDNESDAY.
SHORT TERM /TONIGHT THROUGH SATURDAY NIGHT/
RAIN CONTINUES AT TIMES ACROSS WESTERN WASHINGTON WITH THE AR
AIMED TOWARDS THE NORTHERN PACIFIC NORTHWEST. OBSERVED RAINFALL
AMOUNTS OVER THE LAST 24 HOURS HAVE BEEN HEAVIEST OVER THE SW
SLOPES OF THE OLYMPICS, AND CASCADES OF SNOHOMISH/KING COUNTIES,
WHERE 2 TO 4 INCHES OF RAIN HAVE FALLEN. OTHERWISE, LIGHTER
AMOUNTS HAVE BEEN OBSERVED IN THE INTERIOR AREAS. A FRONTAL
SYSTEM WILL MOVE ACROSS WESTERN WASHINGTON ON FRIDAY, WITH
ENHANCED RAINFALL RATES THROUGH THE PERIOD DUE TO THE FRONTAL
PASSAGE. IN TOTAL, ADDITIONAL RAINFALL AMOUNTS WILL RANGE UP TO
1" FOR PUGET SOUND, 1-2" FOR THE COAST, AND IN THE 2 TO 4" RANGE
FOR THE MOUNTAINS (WITH LOCALLY HIGHER AMOUNTS). RAINFALL,
ALONG WITH HIGH SNOW LEVELS NEAR 9000 FEET WILL RESULT IN
CONTINUED RIVER FLOOD FOR PORTIONS OF WESTERN WASHINGTON. REFER
TO THE .HYDROLOGY DISCUSSION FOR MORE INFORMATION. IN ADDITION
TO THE PRECIPITATION, SOUTH WINDS WILL REMAIN BREEZY AT TIMES
THROUGH FRIDAY, WITH GUSTS GENERALLY RANGING 20 TO 30, WITH
LOCALIZED SOUTH WIND GUSTS NEAR 35 MPH ON FRIDAY.
THE BULK OF THE PRECIPITATION WILL BE EAST OF PUGET SOUND BY
FRIDAY EVENING, WITH THE EXCEPTION OF A POTENTIAL CONVERGENCE
ZONE DEVELOPMENT IN THE VICINITY OF SNOHOMISH COUNTY. ALONG WITH
THE CZ, POST-ONSHORE FLOW WILL INCREASE WITH THE FRONT, AND
WEST WIND GUSTS THROUGH THE STRAIT OF JUAN DE FUCA, INCLUDING
WHIDBEY ISLAND, WILL LIKELY RANGE 30 TO 40 MPH FRIDAY EVENING. A
FEW SHOWERS MAY LINGER ON SATURDAY, BUT GENERALLY DRIER
CONDITIONS WILL PREVAIL. TEMPERATURES WILL COOL BY SATURDAY IN A
POST-FRONTAL AIRMASS.
LONG TERM /SUNDAY THROUGH THURSDAY/
A WEAK SYSTEM WILL MOVE INTO BRITISH COLUMBIA ON SUNDAY,
RESULTING IN A SLIGHT INCREASE IN PRECIPITATION, MAINLY FOR
NORTHERN AREAS. OTHERWISE, SOME RIDGING INFLUENCE ON MONDAY WILL
KEEP DRIER CONDITIONS EARLY NEXT WEEK. A STRONGER FRONTAL
SYSTEM WILL MOVE ACROSS WESTERN WASHINGTON ON TUESDAY, RESULTING
IN THE RETURN OF STEADIER LOWLAND RAIN, HIGH ELEVATION MOUNTAIN
SNOWFALL, AND BREEZY WINDS. SOME UNCERTAINTY EXISTS IN THE
ENSEMBLES WEDNESDAY INTO THURSDAY, BUT UNSETTLED WEATHER LIKELY
IS TO CONTINUE AT TIMES. TEMPERATURES WILL RUN A FEW DEGREES
BELOW NORMAL NEXT WEEK WITH MORE OF A TROUGHING INFLUENCE. JD
AVIATION
WEST-SOUTHWEST FLOW ALOFT AS BROAD TROUGHING SITS OVER THE GULF
OF ALASKA ALONG WITH RIDGING OVER THE SW US. AN ATMOSPHERIC
RIVER CONTINUES TO RIDE ALONG THE FLOW AS THIS STEADY STREAM OF
RAINFALL BRINGS IMPACTS TO AVIATION. A MIX OF CIGS (VFR TO IFR)
HAVE BEEN OBSERVED THIS AFTERNOON WITH THE TREND OF MOSTLY MVFR
TO IFR PERSISTING INTO TONIGHT AND FRIDAY. BREEZY SOUTHERLY
WINDS AT TIMES WITH GUSTS UP 25 KT FOR TERMINALS SUCH AS KPAE
AND BLI.
KSEA...MVFR CIGS MAINLY THROUGHOUT MUCH OF THE UPCOMING TAF
PERIOD. CAN'T RULE OUT INSTANCES OF IFR CIGS UNDER HEAVIER
SHOWERS. WINDS SOUTHERLY 4-8 KT, INCREASING ON FRIDAY WITH GUSTS
UP TO 20-25 KT FRIDAY MORNING AND AFTERNOON.
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
WITH STRONG SCA LEVEL WINDS. CAN'T RULE OUT GUSTS NEAR GALE
FORCE. WINDS WILL EASE INTO THE WEEKEND AS A BUILDING SURFACE
RIDGE OFFSHORE MOVES INLAND. ANOTHER POTENT FRONT WILL ARRIVE
MONDAY NIGHT INTO TUESDAY WITH THE POTENTIAL FOR MORE WIND
RELATED HEADLINES.
41
HYDROLOGY
RAINFALL TOTALS FOR THE LAST 12 HOURS HAVE BEEN 1 TO 2 INCHES OVER
THE CENTRAL CASCADES WITH UP TO ONE AND A QUARTER INCHES ALONG THE
COAST. THE PERIODIC RAIN SHADOW OVER THE CENTRAL PUGET SOUND HAS
CONTINUED AND KEPT RAIN TOTALS DOWN TO A QUARTER INCH OR LESS.
LITTLE CHANGE IN THE PATTERN THROUGH FRIDAY WITH ANOTHER 2 TO 4
INCHES OF RAIN IN THE NORTH AND CENTRAL CASCADES AND ANOTHER 2 TO 3
INCHES OVER THE OLYMPICS. SNOW LEVELS REMAINING ELEVATED, 7500 FEET
TO 9500 FEET. STEADY RAIN WILL GIVE WAY TO SHOWERS AND MUCH LOWER
SNOW LEVELS WHEN THE COLD FRONT MOVES THROUGH FRIDAY EVENING.
THE SNOQUALMIE AND SNOHOMISH RIVERS WILL LIKELY REMAIN ABOVE STAGE.
RAINFALL RATES IN THE MOUNTAINS INCREASE THIS AFTERNOON WITH THE
HIGHER RATES CONTINUING INTO FRIDAY. THIS WILL CREATE A DOUBLE (OR
EVEN TRIPLE) CREST SCENARIO FRIDAY AFTERNOON OR FRIDAY EVENING
PUSHING SOME RIVERS BACK ABOVE FLOOD STAGE. THE RIVERS MOST LIKELY
TO GO BACK ABOVE FLOOD STAGE FRIDAY ARE THE SKYKOMISH AND TOLT
RIVERS. NEW RIVERS LIKELY TO EXCEED FLOOD STAGE ARE THE SKOKOMISH,
STILLAGUAMISH, AND SKAGIT RIVERS, WITH THE LATEST FORECAST SHOWING
SKAGIT RIVERS FORECAST ABOVE MODERATE FLOOD AND JUST BELOW MAJOR
FLOOD.
FARTHER NORTH THE NOOKSACK AT FERNDALE IS FORECAST TO CREST NEAR BUT
BELOW FLOOD STAGE FRIDAY. ALTHOUGH THE SKOKOMISH RIVER IN MASON
COUNTY HAS NOT BEEN RISING VERY QUICKLY AS IS TYPICAL, WITH ANOTHER
ROUND OF MODERATE TO HEAVY WARM RAIN COMING IN OVERNIGHT IT IS
LIKELY THE RIVER GETS TO FLOOD STAGE FRIDAY.
A FLOOD WATCH REMAINS IN EFFECT FOR SKAGIT, WHATCOM, MASON, KING AND
SNOHOMISH COUNTIES DUE TO THE NEW OR RENEWED FLOODING EXPECTED IN
THOSE COUNTIES.
SINCE THE RAIN STARTED ON MONDAY, THE AREA HAS RECEIVED 1 TO 14
INCHES OF RAINFALL WHICH HAS SATURATED THE SOILS. WITH ANOTHER ROUND
OF MODERATE TO HEAVY RAIN, A LANDSLIDE ALERT HAS BEEN ISSUED FOR
INCREASED LANDSLIDE THREAT FOR TODAY THROUGH FRIDAY FOR MOST OF OUR
WESTERN WASHINGTON ZONES. SOME RAIN SHADOWED AREAS HAVE BEEN
EXCLUDED. JBB/FELTON
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 FROM 2 PM FRIDAY TO 11 AM PDT SATURDAY
FOR CENTRAL U.S. WATERS STRAIT OF JUAN DE FUCA-EAST
ENTRANCE U.S. WATERS STRAIT OF JUAN DE FUCA-WEST ENTRANCE
U.S. WATERS STRAIT OF JUAN DE FUCA.
SMALL CRAFT ADVISORY UNTIL 5 AM PDT FRIDAY 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.
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