577
FXUS66 KSEW 132145
AFDSEW
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SEATTLE WA
245 PM PDT SAT SEP 13 2025
SYNOPSIS
HIGH PRESSURE ALOFT WILL SHIFT EAST AS A WEAK FRONT
TRACKS INTO THE AREA TONIGHT INTO SUNDAY WITH SHOWERS AND COOLER
TEMPERATURES. HIGH PRESSURE WILL REBUILD ACROSS WESTERN WASHINGTON
ON MONDAY FOR A BRIEF RETURN OF WARMER AND DRIER CONDITIONS. THE
RIDGE WILL WEAKEN BY MIDWEEK AS ANOTHER WEATHER SYSTEM BRUSHES THE
AREA AND TEMPERATURES RETURN TO NEAR OR A LITTLE BELOW SEASONAL
NORMALS.
SHORT TERM /TONIGHT THROUGH TUESDAY/
CURRENT SATELLITE IS
INDICATIVE OF STRATUS SCATTERING TO MOSTLY CLEAR SKIES ACROSS W
WA THIS AFTERNOON. HOWEVER, A FRONTAL SYSTEM LOOMS OFFSHORE AS IT
ARRIVES TONIGHT WITH RAINFALL ALONG THE COAST. THIS WEAK FRONT IS
A SLOW MOVER, GRADUALLY SPREADING RAIN INLAND BY SUNDAY MORNING.
AMOUNTS HAVE VARIED FROM RUN TO RUN BUT CONSISTENCY HAS REMAINED
WITH 0.25 TO 0.50" OF RAINFALL ALONG THE MOUNTAINS WITH NOW
SIMILAR AMOUNTS ALONG THE COAST. WITH OROGRAPHIC LIFTING, LOCALLY
HIGHER AMOUNTS ARE POSSIBLE. MAINLY 0.10 TO 0.25" IS FAVORED FOR
THE INTERIOR LOWLANDS. COOLER CONDITIONS WILL ALSO ACCOMPANY THIS
DISTURBANCE WITH HIGHS IN THE 60S, SEVERAL DEGREES BELOW AVERAGE
FOR THIS TIME OF THE YEAR.
THE AFOREMENTIONED FRONT IS CROSSING THE CASCADES BY SUNDAY
EVENING WITH LINGERING SHOWERS AND A CONVERGENCE ZONE. DRY WEATHER
RETURNS OVERNIGHT SUNDAY INTO MONDAY AS AN UPPER-RIDGE SETTLES
OVERHEAD. A WARM UP WILL ALSO COMMENCE WITH NEAR SEASONAL
CONDITIONS ON MONDAY FOLLOWED BY A SHARP RISE IN TEMPERATURES ON
TUESDAY BY OVER 10 DEGREES, AIDED BY RIDGING AND LOW-LEVEL
OFFSHORE FLOW DEVELOPMENT VIA SURFACE THERMAL TROUGH EXPANSION
ALONG THE WEST COAST. A DEVELOPING 995 MB SURFACE LOW SWINGING
NEARLY INTO HAIDA GWAII MAY LIKELY HELPING TO SWITCH THE FLOW
OFFSHORE AS WELL. WILL HAVE TO MONITOR THE POTENTIAL FOR AIR
QUALITY BEING IMPACTING ON TUESDAY AS EASTERLY WINDS MAY PUSH
WILDFIRE SMOKE INTO THE AREA FROM EXISTING FIRES EAST OF THE
CASCADES. THE FLOW IS EXPECTED TO QUICKLY TURN ONSHORE TUESDAY
NIGHT INTO WEDNESDAY AS ANOTHER WEATHER SYSTEM APPROACHES THE
AREA.
LONG TERM /WEDNESDAY THROUGH SATURDAY/
GOING INTO MIDWEEK
ONWARD SOME UNCERTAINTY EXISTS IN THE FORECAST. WHILE THERE'S
FAIRLY GOOD AGREEMENT IN THE MODELS THAT COOLER TEMPERATURES WILL
RETURN, THE ENSEMBLES ARE STILL IN DISAGREEMENT WITH QPF.
NONETHELESS, THIS DOES APPEAR TO SIGNAL SOMETHING OF SEASONAL
TURNING POINT WITH A MORE ACTIVE PATTERN TAKING SHAPE OVER THE
NORTHEAST PACIFIC AS WE TEETER CLOSER TO AUTUMN.
MCMILLIAN
AVIATION
SOUTHERLY FLOW ALOFT THIS AFTERNOON INTO SUNDAY AS A
FRONTAL SYSTEM APPROACHES WESTERN WASHINGTON. VFR CURRENTLY AS
PREVIOUS STRATUS HAS SCATTERED AND CLEARED FOR MOST LOCATIONS. MID
TO HIGH LEVEL CLOUDS WILL INCREASE THIS EVENING AS RAIN AND SHOWERS
ARE EXPECTED TO REACH THE COAST LATE TONIGHT INTO SUNDAY MORNING.
MVFR TO IFR CEILINGS ARE TO RETURN, CAN'T RULE OUT ISOLATED LIFR
AS WELL. A GRADUAL IMPROVEMENT TO VFR IS EXPECTED SUNDAY AFTERNOON
BUT A LINGERING PSCZ MAY KEEP LOW CIGS NEAR KPAE AND OTHER PUGET
SOUND TERMINALS. S TO SW WIND THIS AFTERNOON CONTINUING INTO
SUNDAY WITH SCATTERED GUSTS.
KSEA...VFR CONDITIONS THIS AFTERNOON, WITH MID AND HIGH CLOUDS
LATER TONIGHT AHEAD OF RAIN SHOWERS ARRIVING SUNDAY MORNING. WITH
THEM, MVFR CIGS ARE LIKELY BUT A GRADUAL IMPROVEMENT TO VFR IS
EXPECTED IN THE AFTERNOON. S/SW WINDS THROUGH MUCH OF THE PERIOD
AROUND 5-10 KT.
MCMILLIAN
MARINE
A FRONTAL SYSTEM WILL MOVE ACROSS THE AREA WATERS
TONIGHT INTO SUNDAY. SOUTHERLY WINDS WILL CONTINUE TO INCREASE
ACROSS THE OUTER COASTAL WATERS THIS AFTERNOON AND WILL BRIEFLY
GUST TO 25 KT, SO HAVE MAINTAINED THE CURRENT SMALL CRAFT ADVISORY
IN EFFECT FOR PORTIONS OF THE OUTER COAST. SOUTHERLY WINDS WILL
THEN TRANSITION TO MORE NORTHWESTERLY IN THE WAKE OF THE FRONT ON
SUNDAY. AT THIS TIME, THE NORTHWESTERLY WINDS PRIMARILY LOOK TO
REMAIN BELOW SMALL CRAFT ADVISORY CRITERIA AND GENERALLY LOOK TO
PERSIST BETWEEN 15-20 KT. INCREASING ONSHORE FLOW WILL BRING A
PUSH OF WESTERLY WINDS DOWN THE CENTRAL AND EASTERN STRAIT OF JUAN
DE FUCA SUNDAY AFTERNOON AND EVENING, WHERE WIND GUSTS TO 25-30
KT WILL BE POSSIBLE.
HIGH PRESSURE WILL THEN BUILD BACK INTO THE AREA WATERS IN THE
WAKE OF THE FRONT SUNDAY NIGHT INTO MONDAY. A THERMAL TROUGH
CREEPING NORTHWARD ALONG THE COAST EARLY ON TUESDAY WILL THEN
BRING A PERIOD OF OFFSHORE FLOW TO THE AREA WATERS. THIS WILL
REMAIN SHORT-LIVED, HOWEVER, AS ADDITIONAL FRONTAL SYSTEMS LOOK
TO MOVE ACROSS THE WATERS MID TO LATE WEEK.
SEAS WILL INCREASE TO 6-8 FT TONIGHT AND MAY BRIEFLY BECOME STEEP
AT TIMES WITH PERIODS OF AROUND 8 SECONDS. STEEP SEAS WILL SUBSIDE
INTO SUNDAY AND SEAS WILL GRADUALLY SUBSIDE TOWARDS 3-5 FT BY MONDAY.
SEAS LOOK TO BUILD BACK UP AGAIN TOWARDS 6-8 FT MID TO LATE WEEK
AS ADDITIONAL SYSTEMS MOVE ACROSS THE AREA WATERS.
14
FIRE WEATHER
A FRONTAL SYSTEM MOVING INTO THE AREA ON SUNDAY
WILL BRING WIDESPREAD LIGHT RAIN TO THE REGION, WITH A FEW SPOTS
OF WETTING RAINS POSSIBLE ALONG THE COAST AND IN THE MOUNTAINS.
CONDITIONS WILL DRY OUT AGAIN ON MONDAY AS AN UPPER LEVEL RIDGE
STARTS TO BUILD BACK INTO THE REGION. A THERMAL TROUGH AT THE
SURFACE WILL CREEP NORTHWARD ALONG THE COAST EARLY ON TUESDAY,
ALLOWING FOR FLOW TO TURN OFFSHORE. LATEST GUIDANCE HIGHLIGHTS
EASTERLY WINDS PICKING UP ACROSS THE CASCADE GAPS DURING THE EARLY
MORNING HOURS AND PERSISTING INTO THE AFTERNOON, WITH GUSTS TO
20-25 MPH POSSIBLE. EASTERLY WINDS WILL HELP TO WARM AND DRY
CONDITIONS OUT FURTHER, WITH RELATIVE HUMIDITIES EXPECTED TO FALL
IN THE LOW 30S ACROSS PORTIONS OF THE CENTRAL AND SOUTHERN CASCADES.
OVERALL, THE COMBINATION OF THESE EASTERLY WINDS AND THE WARM AND
DRY CONDITIONS WILL BRING ELEVATED FIRE WEATHER CONDITIONS TO
PORTIONS OF WESTERN WASHINGTON ON TUESDAY.
ELEVATED CONDITIONS WILL BE SHORT-LIVED, HOWEVER, AS WINDS ARE
EXPECTED TO SWITCH BACK TO ONSHORE BY MIDWEEK. ADDITIONAL SYSTEMS
MAY MOVE ACROSS THE AREA MID TO LATE WEEK, BRINGING THE NEXT
CHANCES OF RAIN.
14
SEW WATCHES/WARNINGS/ADVISORIES
WA...NONE.
PZ...SMALL CRAFT ADVISORY FROM 11 AM SUNDAY TO 2 AM PDT MONDAY FOR
CENTRAL U.S. WATERS STRAIT OF JUAN DE FUCA-EAST ENTRANCE
U.S. WATERS STRAIT OF JUAN DE FUCA.
SMALL CRAFT ADVISORY UNTIL 8 PM PDT THIS EVENING 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.
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