372
FXUS66 KSEW 080348
AFDSEW
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SEATTLE WA
848 PM PDT MON SEP 7 2026
UPDATE
SATELLITE IMAGERY SHOWS MIDDLE AND HIGH LEVEL CLOUDS WRAPPING
AROUND THE UPPER LEVEL TROUGH OVER EASTERN WASHINGTON MOVING
INTO THE NORTHERN PORTION OF THE AREA. MOSTLY CLEAR SKIES
ELSEWHERE. FLOW ALOFT TURNING NORTHERLY OVERNIGHT DECREASING THE
AMOUNT OF MIDDLE AND HIGH LEVEL CLOUDS. WITH THE LONGER NIGHTS
AND LIGHT NORTHERLY GRADIENTS POSSIBILITY OF FOG/LOW STRATUS
FORMING NEAR THE STRAIT OF JUAN DE FUCA AND PUGET SOUND AS WELL
AS OVER LAKE WASHINGTON. MARINE PUSH NOT STRONG ENOUGH TO
ADVECT STRATUS EAST OF THE PUGET SOUND OVERNIGHT. SUNNY TUESDAY
AFTER THE AREAS OF MORNING LOW CLOUDS AND FOG. LOW LEVEL FLOW
TURNING LIGHT OFFSHORE LATER TOMORROW INTO WEDNESDAY. WEDNESDAY
LOOKS TO BE THE WARMEST DAY SINCE AUGUST 25TH. WILL MAKE QUICK
UPDATE FOR THE FOG/LOW CLOUDS TUESDAY MORNING. THE REST OF THE
FORECAST IN GOOD SHAPE. FELTON
SYNOPSIS
LOW PRESSURE WILL MOVE EAST OF THE CASCADES TONIGHT. HIGH
PRESSURE WILL MOVE IN TUESDAY AND WEDNESDAY FOR DRIER AND WARMER
CONDITIONS. A PAIR OF SYSTEMS LOOK TO MOVE THROUGH THURSDAY
THROUGH THE WEEKEND FOR MORE CHANCES FOR SHOWERS AND COOLER
WEATHER.
SHORT TERM /TONIGHT THROUGH WEDNESDAY NIGHT/
WATER VAPOR IMAGERY SHOWS WASHINGTON REMAINING UNDER THE
INFLUENCE OF THE BROAD UPPER LEVEL TROUGH THAT HAS BEEN SITTING
OVER THE AREA SINCE LAST WEEK FINALLY BEGINNING TO EJECT
EASTWARD TOWARDS MONTANA. CHANCES FOR LIGHT SHOWERS WILL
CONTINUE THIS AFTERNOON, BUT EXPECT CLOUDS TO SLOWLY DECREASE IN
COVERAGE INTO THIS EVENING. HIGHS WILL REMAIN IN THE MID TO
UPPER 60S, PERHAPS INTO THE LOW 70S FOR PLACES THAT SEE THE
MOST SUN. CLEARER SKIES EXPECTED THIS EVENING THOUGH EXPECT
ANOTHER MARINE LAYER TO START THE DAY TUESDAY. LOWS IN THE UPPER
40S TO MID 50S.
UPPER LEVEL RIDGING WILL BRIEFLY BUILD ACROSS THE AREA THROUGH
WEDNESDAY. WEAK SURFACE THERMAL TROUGHING WILL DEVELOP ON
TUESDAY AND WILL ALLOW THE LOW LEVEL FLOW TO TURN OFFSHORE.
WINDS WILL NOT BE VERY STRONG BUT IT WILL ALLOW FOR CLEAR SKIES
AND TEMPERATURES TO RISE INTO THE MID 70S ON TUESDAY, THEN INTO
THE UPPER 70S TO LOW 80S ON WEDNESDAY. LOW TEMPERATURES WILL
ALSO NOTICEABLY INCREASE, UP INTO THE MID TO UPPER 50S BY
WEDNESDAY NIGHT. 62
LONG TERM /THURSDAY THROUGH MONDAY/
ENSEMBLE GUIDANCE REMAINS PRETTY WELL CLUSTERED THROUGH THURSDAY AS
THE NEXT DISTURBANCE DROPS DOWN ACROSS THE PACIFIC NORTHWEST.
THIS WILL BRING A RETURN OF COOLER MARINE AIR, CLOUD COVER, RAIN
CHANCES. TYPICALLY WINDY LOCATIONS MAY SEE INCREASED BREEZES BY
THURSDAY EVENING IN THE STRONGER ONSHORE LOW-LEVEL FLOW.
CONFIDENCE BEGINS TO DECREASE A BIT BY FRIDAY AND INTO THE WEEKEND
AS THE ENSEMBLES CONTINUE TO DEPICT A FAIRLY LARGE RANGE OF
POSSIBLE OUTCOMES. SPECIFICALLY, MUCH OF THIS UNCERTAINTY CENTERS
AROUND THE DEPTH AND TIMING OF THE NEXT UPPER TROUGH SWINGING ACROSS
THE REGION. HOWEVER, REGARDLESS OF SPECIFICS, THERE'S NOT A
SIGNIFICANTLY STRONG SIGNAL FOR IMPACTFUL WEATHER.
EXPECT INCREASED CLOUDS, COOLER TEMPERATURES, AND RAIN CHANCES WHEN
THE TROUGH SWINGS ACROSS, AND SLIGHTLY WARMER AND DRIER CONDITIONS
ONCE IT PASSES. CULLEN
AVIATION
NORTHERLY FLOW ALOFT AS AN UPPER LEVEL OVER EASTERN WASHINGTON
CONTINUES TO MOVE EAST. VFR CONDITIONS THIS EVENING WITH VFR
CONDITIONS CONTINUING IN THE OVERNIGHT HOURS. IFR STRATUS
FORMING ALONG THE COAST AFTER 09Z WILL NOT MAKE IT INTO THE
INTERIOR TERMINALS. COULD SEE LOW STRATUS AND FOG FORM NEAR THE
PUGET SOUND AND LAKE WASHINGTON 12Z-16Z WITH POSSIBLE LIFR
CEILINGS AT KPAE AND KCLM. LIFR CONDITIONS ALSO POSSIBLE AT KOLM
BETWEEN 12Z-16Z. WHAT LITTLE FOG AND LOW CLOUD THAT DOES FORM
OVER THE INTERIOR WILL BE SHALLOW WITH VFR CONDITIONS ALL AREAS
EXCEPT KHQM BY 17Z. KHQM CLEARING OUT BY 19Z.
KSEA...VFR CEILINGS THROUGH TUESDAY. LOW CLOUDS COULD FORM NEAR
THE PUGET SOUND AND LAKE WASHINGTON 12Z-16Z BUT AT THIS POINT
IT DOES NOT LOOK LIKE THE CLOUDS WILL MAKE IT TO THE TERMINAL.
NORTHERLY WIND 4 TO 8 KNOTS. FELTON
MARINE
HIGH PRESSURE WILL GRADUALLY BUILD ACROSS THE COASTAL WATERS
THROUGH WEDNESDAY. WINDS WILL BEGIN TO INCREASE TOMORROW AND
COULD REACH CLOSE TO SMALL CRAFT ADVISORY THRESHOLDS BY
WEDNESDAY NIGHT INTO THURSDAY (50-80% CHC) OVER THE OUTER
COASTAL WATERS AS THE PRESSURE GRADIENT TIGHTENS DUE TO AN
APPROACHING FRONTAL SYSTEM FROM THE NORTH. WINDS THROUGH THE
STRAIT OF JUAN DE FUCA BEGIN TO INCREASE WEDNESDAY EVENING, WITH
HIGHER CONFIDENCE OF SMALL CRAFT WINDS THROUGH LATE THURSDAY
MORNING. THE FRONTAL SYSTEM WEAKENS AS IT MOVES THROUGH ON
THURSDAY, ALLOWING WINDS TO EASE AREA-WIDE. ANOTHER SYSTEM MAY
MOVE THROUGH THE WATERS LATE FRIDAY INTO SATURDAY, BUT IS
CURRENTLY NOT SHOWING A SIGNAL FOR STRONGER WINDS.
SEAS REMAIN 3-6 FT THROUGH WEDNESDAY. SEAS WILL INCREASE
WEDNESDAY NIGHT INTO THURSDAY UP TO AROUND 7-10 FT AND BECOME
STEEP AS SHORT PERIOD WAVES FROM THE STRONGER WINDS OVER THE
COASTAL WATERS BEGIN TO DOMINATE. 62
FIRE WEATHER
WARMER AND DRIER CONDITIONS DEVELOP ACROSS THE REGION TUESDAY
AND ESPECIALLY WEDNESDAY. GIVEN THE RECENT COOL AND MOIST
CONDITIONS, THIS WILL GENERALLY RETURN THE FIRE WEATHER
CONDITIONS TRENDING BACK BACK TO SEASONAL LEVELS OF CONCERN.
LIGHT OFFSHORE FLOW LATE TUESDAY INTO WEDNESDAY COULD YIELD POOR
OVERNIGHT RH RECOVERIES ON THE RIDGES IN CASCADES AND OLYMPICS,
WITH DAYTIME HUMIDITIES APPROACHING CRITICAL THRESHOLDS.
HOWEVER, GIVEN THE SHORT-LIVED PERIOD OF WARMER CONDITIONS AND
OFFSHORE FLOW (MORE HUMID AIR RETURNS BY LATE THURSDAY WITH
BREEZY ONSHORE FLOW), DO NOT EXPECT A SIGNIFICANT RAMP UP IN THE
FIRE WEATHER RISK. CULLEN
SEW WATCHES/WARNINGS/ADVISORIES
WA...NONE.
PZ...NONE.
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