143
FXUS66 KSEW 101613
AFDSEW
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SEATTLE WA
913 AM PDT THU SEP 10 2026
SYNOPSIS
UPPER LEVEL RIDGING PROGRESS OFF AND AWAY ON THURSDAY AS
TROUGHING DEVELOPS OVER THE PACIFIC NORTHWEST LATE THIS WEEK. AN
UPPER LOW PROGRESSES ACROSS THE REGION OVER THE WEEKEND
BRINGING RAIN POTENTIAL AND COOLER TEMPERATURES. DRIER
CONDITIONS ARE EXPECTED ON MONDAY WITH A SLOW WARMING TREND
THROUGH MIDWEEK.
SHORT TERM /TODAY THROUGH SATURDAY/
NO SIGNIFICANT CHANGES
MADE TO THE FORECAST THIS MORNING. THE PREVIOUS DISCUSSION CAN
BE FOUND BELOW ALONG WITH UPDATES TO THE AVIATION AND MARINE
SECTIONS:
THE UPPER-RIDGE THAT BROUGHT SLIGHTLY ABOVE AVERAGE
TEMPERATURES YESTERDAY HAS PROGRESSED OFF AND AWAY WELL EAST OF
THE CASCADES THIS MORNING. AN UPPER-TROUGH IS NOW REPLACING IT
AS LOW-LEVEL ONSHORE FLOW INCREASES ACROSS WESTERN WA. AS A
RESULT, AREAS OF STRATUS AND COOLER TEMPERATURES ARE IN STORE
FOR TODAY. HIGH TEMPERATURES ARE TO REMAIN IN THE LOWER TO MID
70S ACROSS THE INTERIOR, 5-10 DEGREES COOLER COMPARED TO THE
PREVIOUS DAY'S WITH COASTAL AREAS IN THE 60S. ZONAL FLOW IN THE
850 MB LEVELS WILL LEAD TO WEAK CONVERGENCE LATER TONIGHT ACROSS
SNOHOMISH COUNTY. OVERNIGHT LOWS ARE TO RANGE BETWEEN THE UPPER
50S TO MID 50S.
TROUGHING FURTHER DEEPENS FRIDAY AS AN UPPER-LOW DEVELOPS
OFFSHORE OF VANCOUVER ISLAND. AREAS OF DRIZZLE MAY ALSO EXIST
FRIDAY MORNING ASSOCIATED WITH WIDESPREAD STRATUS, HOWEVER,
FRIDAY IS EXPECTED TO REMAIN PREDOMINANTLY DRY WITH THE UPPER
LOW WELL OFFSHORE. POPS WILL INCREASE ON SATURDAY ACROSS THE CWA
AS THE UPPER-LOW MOVES ONSHORE WITH WIDESPREAD RAIN AND SHOWERS.
THERE IS ALSO A 15 TO 25% PROBABILITY OF THUNDERSTORMS SOUTH OF
SNOHOMISH COUNTY SATURDAY AFTERNOON. CAN'T RULE OUT LOCALLY
BREEZY WIND AT TIMES. HIGHS FOR BOTH FRIDAY AND SATURDAY BOTH IN
THE 60S WITH LOWS IN THE 50S.
LONG TERM /SATURDAY NIGHT THROUGH WEDNESDAY/
THE UPPER LOW CONTINUES TO DRIFT EASTWARD ON SUNDAY,
WITH A SLOW DRYING TREND DURING THE EVENING. THE EXCEPTION
BEING THE CASCADES WHERE LINGERING MOISTURE IS EXPECTED AT LEAST
THROUGH SUNDAY AM. AN UPPER RIDGE BEGINS TO BUILD WELL OFFSHORE
MONDAY FOR A SLOW WARMING TREND. PREDOMINANTLY DRY CONDITIONS
ARE THEN FORECAST INTO THE MIDDLE OF NEXT WEEK, BUT WILL NEED TO
MONITOR THE EXISTENCE OF ANY WEAK TROUGHING AROUND THE TUESDAY
TIMEFRAME AS INDICATED BY A SMALL SUBSET OF ENSEMBLES. EITHER
WAY, TEMPERATURES TREND BACK TO NEAR NORMAL EARLY NEXT WEEK.
AVIATION
GENERALLY VFR ACROSS WESTERN WASHINGTON EARLY THIS MORNING, WITH
POCKETS OF DETERIORATED MVFR TO IFR CONDITIONS FROM NOW THROUGH 18Z
AS A FRONTAL SYSTEM BRINGS A MARINE STRATUS LAYER INLAND. LOW
CEILINGS MAY LINGER INTO THE EARLY AFTERNOON TODAY, EXPECTED TO
ERODE FOR MOST INLAND TERMINALS BY 21Z TO REVEAL VFR CONDITIONS.
THERE ARE SIGNALS FOR A WEAK CONVERGENCE ZONE POST-FRONT IN SOUTHERN
SNOHOMISH COUNTY, BUT SHOWER ACTIVITY IS EXPECTED TO BE MINIMAL.
NORTHERLY SURFACE WINDS WILL GENERALLY REMAIN LIGHT 10 KT OR LESS
THROUGH THE TAF PERIOD, ALTHOUGH A FEW PUGET SOUND LOCATIONS WILL
SEE GUSTS UP TO 18 KT FROM THE NORTHEAST THROUGH THE MORNING AS
WINDS SWITCH TO THE NORTHWEST. ANOTHER MARINE PUSH WILL LIKELY BRING
ANOTHER ROUND OF MVFR LOW STRATUS ACROSS THE REGION FRIDAY MORNING,
AS WINDS TURN AROUND TO THE SOUTHWEST.
KSEA...LOWER CLOUDS ARE MOVING TOWARDS THE TERMINAL - THERE REMAINS
A 20-30% CHANCE OF AN MVFR CIG THROUGH 18Z, OTHERWISE CEILINGS FOR
THE REMAINDER OF THE DAY LIKELY TO REMAIN VFR. A FEW NORTHEAST GUSTS
TO 18 KT WILL BE PRESENT THROUGH 18Z, AS WINDS SWITCH TO THE NORTH
AND NORTHWEST 5-10 KT. THERE IS A 40-50% CHANCE OF MVFR CEILINGS
EARLY FRIDAY MORNING THROUGH LATE MORNING. WINDS WILL FLIP AROUND TO
THE SOUTH/SOUTHWEST IN THE MORNING AT 09-12Z.
15/HPR
MARINE
A FRONTAL SYSTEM WILL CONTINUE TO CROSS AREA WATERS TODAY, BRINGING
BREEZY WESTERLIES THROUGH THE STRAIT OF JUAN DE FUCA AND ELEVATED
WAVES OFFSHORE. THE SMALL CRAFT ADVISORY FOR THE CENTRAL/EAST STRAIT
OF JUAN DE FUCA HAS EXPIRED THIS MORNING, AND A SMALL CRAFT OVER THE
OUTER COASTAL WATERS REMAINS IN EFFECT FOR WAVES OF 8 TO 11 FEET AND
STEEP SEAS WITH A PERIOD OF 8 TO 10 SECONDS THROUGH FRIDAY MORNING
BEFORE SEAS BEGIN TO SUBSIDE.
ANOTHER WEATHER SYSTEM IS ON TRACK TO CROSS THE WATERS LATE FRIDAY
IN TO SATURDAY, BRINGING LITTLE IN THE WAY OF WIND BUT WILL GENERATE
SCATTERED THUNDERSTORM ACTIVITY MAINLY OVER THE COASTAL WATERS. SEAS
WILL EASE BY SATURDAY TO AROUND 4 TO 6 FEET, WHERE THEY WILL REMAIN
INTO EARLY NEXT WEEK.
SURFACE HIGH PRESSURE IS EXPECTED TO BUILD OVER AREA WATERS BY THE
END OF THE WEEKEND, MAINTAINING GENERALLY BENIGN CONDITIONS.
15/HPR
FIRE WEATHER
A WEAK AND MOSTLY DRY FRONTAL SYSTEM PASSING OVER THE REGION HAS
BROUGHT A RETURN TO ONSHORE FLOW, MAINTAINING COOLER AND MORE MOIST
CONDITIONS THROUGHOUT THE WEEKEND. LIGHT PRECIPITATION IS LIKELY
LATE FRIDAY INTO SATURDAY AS ANOTHER WEAK SYSTEM MOVES OVER THE
REGION. CONDITIONS ARE EXPECTED TO GRADUALLY WARM AND DRY INTO NEXT
WEEK, THOUGH FIRE WEATHER CONCERNS REMAIN LOW AT THIS TIME.
15
SEW WATCHES/WARNINGS/ADVISORIES
WA...NONE.
PZ...SMALL CRAFT ADVISORY UNTIL 5 AM PDT FRIDAY 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