531
FXUS66 KSEW 140839
AFDSEW
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SEATTLE WA
139 AM PDT SUN SEP 14 2025
SYNOPSIS
A FRONTAL BOUNDARY WILL BRING SHOWERS AND COOLER
TEMPERATURES TO WESTERN WASHINGTON TODAY. HIGH PRESSURE WILL
REBUILD ON MONDAY AND TUESDAY 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 /TODAY THROUGH TUESDAY/
SHOWERS CONTINUE TO PRESS
ONSHORE ACROSS THE OLYMPIC PENINSULA EARLY THIS MORNING AS A
WEAKENING COLD FRONT MOVES INTO THE REGION. CONVERGENCE BEHIND
THE FRONT WILL SERVE AS THE INTERIORS BEST CHANCE FOR SOME
APPRECIABLE QPF LATER THIS MORNING INTO THE EARLY AFTERNOON HOURS.
PLENTIFUL CLOUD COVER ALONG WITH THE PRECIP WILL HOLD TEMPERATURES
INTO THE 60S ACROSS THE LOWLANDS TODAY. UPPER RIDGING WILL BEGIN
TO REBUILD INTO THE REGION TONIGHT AND MONDAY AS THERMALLY INDUCED
LOW PRESSURE STARTS TO EXPAND NORTHWARD ALONG THE OREGON COAST.
IT'S STILL ON TRACK TO REACH THE WASHINGTON COAST ON TUESDAY
TURNING THE LOW LEVEL FLOW OFFSHORE. THIS WILL PROVIDE A
CONSIDERABLE BOOST IN TEMPERATURES ACROSS WESTERN WASHINGTON WITH
COASTAL AREAS AS WELL AS MUCH OF THE INTERIOR LOWLANDS APPROACHING
OR EXCEEDING 80 DEGREES.
LONG TERM /WEDNESDAY THROUGH SATURDAY/
A WEAKENING FRONT IS ON
TRACK TO BRUSH THE REGION ON WEDNESDAY. PROSPECTS FOR PRECIP WITH
THIS SYSTEM LOOK MINIMAL, BUT IT WILL FLIP THE FLOW BACK ONSHORE
AND COOL TEMPERATURES TO TEMPER ANY SHORT TERM FIRE WEATHER
CONCERNS. WEAK UPPER TROUGHING LOOKS TO REMAIN OVER THE AREA FOR
MUCH OF THE SECOND HALF OF THE WEEK. THOUGH THE PATTERN LOOKS
FAIRLY DEVOID OF ANY RAINFALL, TEMPERATURES WILL HOLD NEAR OR
LITTLE BELOW SEASONAL NORMS. AS ALLUDED TO YESTERDAY, A GLANCE AT
THE ENSEMBLE HEIGHT ANOMALIES SUGGESTS THAT BROAD UPPER TROUGHING
OVER THE GULF OF ALASKA LATE IN THE UPCOMING WEEKEND MAY WELL BE
A TURNING POINT TOWARD A MORE PROLONGED STRETCH OF FALL-LIKE
WEATHER HEADING INTO NEXT WEEK. STAY TUNED. 27
AVIATION
SOUTHWEST FLOW ALOFT, AS A FRONTAL SYSTEM MOVES
ACROSS THE AREA, WILL TRANSITION NORTHWESTERLY TONIGHT INTO
MONDAY MORNING AS AN UPPER RIDGE BUILDS OFFSHORE. RAIN CONTINUES
ALONG THE COAST EARLY THIS MORNING AS THE FRONT SLOWLY
PROGRESSES EASTWARDS. CIGS WILL SLOWLY LOWER FOR THE INTERIOR
SITES INTO SUNDAY MORNING TOWARDS MVFR/IFR, WITH CONTINUED
MVFR/IFR ALONG THE COAST. LOCALIZED LIFR CIGS POSSIBLE AS WELL.
RAIN WILL REACH THE INTERIOR GENERALLY BETWEEN 11 TO 17Z, WITH
CONDITIONS DRYING ALONG THE COAST. CIGS WILL SLOWLY LIFT IN THE
AFTERNOON FOR MOST AREAS. HOWEVER, A CONVERGENCE ZONE IS
EXPECTED TO DEVELOP GENERALLY FROM KPAE TO KSEA WHICH WILL
RESULT IN CONTINUED MVFR IN THE AFTERNOON WITH SHOWERS
LINGERING. INCREASING W/SW WINDS THROUGH THIS MORNING, WITH
WINDS TRANSITIONING MORE N/NE IN THE VICINITY OF THE CONVERGENCE
ZONE LATER TODAY.
KSEA...VFR CIGS EARLY THIS MORNING WITH INCREASING MID AND HIGH
CLOUDS. CIGS EXPECTED TO LOWER TO MVFR GENERALLY BETWEEN 13 TO 14Z
AND CONTINUE INTO THE AFTERNOON. THERE IS ALSO APPROXIMATELY A
35 TO 40% CHANCE OF IFR CIGS BETWEEN 15 TO 19Z. RAIN SHOWERS
WILL BE AROUND ALSO DURING THIS PERIOD. A CONVERGENCE ZONE THEN
LOOKS TO DEVELOP OVER KING & SNOHOMISH COUNTIES THIS AFTERNOON.
ALTHOUGH THE BEST CHANCE FOR SHOWERS DURING THE AFTERNOON WILL
REMAIN N OF THE TERMINAL, WINDS MAY TRANSITION MORE NE AFTER 20Z
DUE TO THE VICINITY OF THE CONVERGENCE ZONE. HOWEVER,
CONFIDENCE REMAINS LOW IN THIS OCCURING. OTHERWISE, CONTINUED
S/SW SURFACE WINDS THIS MORNING. JD
MARINE
A WEATHER SYSTEM WILL CONTINUE TO MOVE INLAND INTO SUNDAY
MORNING. WINDS WILL CONTINUE TO TRANSITION MORE NORTHWESTERLY OVER
THE COASTAL WATERS THIS MORNING AND REMAIN NORTHWEST INTO SUNDAY
NIGHT. WINDS ARE EXPECTED TO REMAIN GENERALLY BELOW SMALL CRAFT
ADVISORY CRITERIA FOR THE COASTAL WATERS TODAY, HOWEVER, BRIEF GUSTS
OF 25 KTS ARE POSSIBLE. IN ADDITION, ONSHORE FLOW WILL INCREASE
BEHIND THE FRONT, RESULTING IN A WESTERLY PUSH THROUGH THE
STRAIT OF JUAN DE FUCA TODAY. SMALL CRAFT ADVISORY WINDS ARE
EXPECTED FOR THE CENTRAL AND EASTERN PORTIONS OF THE STRAIT OF
JUAN DE FUCA LATER THIS MORNING INTO THIS EVENING. WIND GUSTS
MAY ALSO PEAK FOR A BRIEF PERIOD NEAR 35 KTS FOR THE CENTRAL
STRAIT OF JUAN DE FUCA. OTHERWISE, BRIEF SCA WIND GUSTS MAY BE
OBSERVED ALONG THE FAR SOUTHERN PORTIONS OF PUGET SOUND, BUT
WINDS MAINLY EXPECTED BELOW SCA THRESHOLDS.
HIGH PRESSURE WILL BUILD BACK INTO THE WATERS ON MONDAY. A THERMAL
TROUGH WILL DEVELOP NORTHWARDS ALONG THE COAST MONDAY NIGHT INTO
EARLY TUESDAY, RESULTING IN A PERIOD OF OFFSHORE FLOW TO THE WATERS.
DURING THIS TIME, EAST WINDS WILL INCREASE PARTICULARLY FOR THE
CENTRAL AND WESTERN STRAIT OF JUAN DE FUCA. HOWEVER, ONSHORE FLOW
LOOKS TO THEN INCREASE AGAIN MID TO LATE WEEK.
SEAS WILL BE 6 TO 8 FEET THROUGH TODAY. SEAS MAY BRIEFLY BECOME
STEEP AT TIMES FOR THE OUTER COASTAL WATERS AS WELL. SEAS WILL THEN
SUBSIDE TONIGHT INTO MONDAY TO NEAR 4 TO 6 FEET. SEAS MAY THEN BUILD
BACK TO NEAR 7 TO 9 FEET BY WEDNESDAY AND THURSDAY. JD
FIRE WEATHER
A FRONTAL SYSTEM MOVING INTO THE AREA TODAY 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 LATE IN THE WEEK, BRINGING THE NEXT
CHANCES OF RAIN.
14/27
SEW WATCHES/WARNINGS/ADVISORIES
WA...NONE.
PZ...SMALL CRAFT ADVISORY FROM 8 AM THIS MORNING TO 11 PM PDT THIS
EVENING FOR CENTRAL U.S. WATERS STRAIT OF JUAN DE FUCA-
EAST ENTRANCE U.S. WATERS STRAIT OF JUAN DE FUCA.
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