889
FXUS66 KSEW 150341
AFDSEW
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SEATTLE WA
841 PM PDT SUN SEP 14 2025
UPDATE
SHOWERS CONTINUE ACROSS WHATCOM AND SKAGIT COUNTIES THIS
EVENING. A CONVERGENCE ZONE ALSO CONTINUES THIS EVENING IN PUGET
SOUND, WITH AN AREA OF SHOWERS DRIFTING SOUTHWARD FROM SNOHOMISH
COUNTY DOWN INTO KING COUNTY. POST-FRONT, SHOWERS WILL WRAP
OVERNIGHT WITH A MARINE PUSH EXPECTED TO BRING CLOUD COVER IN MONDAY
MORNING, WITH CLEAR SKIES IN THE AFTERNOON. REMAINDER OF THE
FORECAST IS ON TRACK (UPDATES WERE MADE TO THE AVIATION SECTION).
HPR
SHORT TERM /TONIGHT THROUGH WEDNESDAY/
SHOWERS ARE LINGERING
ACROSS W WA AS A COLD FRONT IS NOW EAST OF THE CASCADES.
CONDITIONS WILL GRADUALLY TREND DRIER TONIGHT AS A WEAK CONVERGENCE
ZONE AND ACCOMPANYING SHOWERS PETER OUT. AN UPPER-LOW WILL EXIT
THE REGION AND BE REPLACED BY RIDGING ALOFT. OVERNIGHT LOWS WILL
RANGE BETWEEN THE MID 40S TO LOWER 50S. AREAL LOW CLOUDS AND
PATCHY FOG ARE FAVORED TO DEVELOP INTO MONDAY MORNING AS WELL.
A NOTICEABLE PATTERN CHANGE WILL TAKE HOLD AS WE START THE NEW
WEEK. MODELS INDICATE THE UPPER-RIDGE SETTLING OVERHEAD ON MONDAY
BEFORE AMPLIFYING AS THE DAY PROGRESS. A THERMALLY INDUCED LOW
PRESSURE IS FORECAST TO ALSO EXPAND NORTHWARD ALONG THE OREGON
COAST, LEADING TO A PERIOD OF EASTERLY OFFSHORE FLOW. LARGE-SCALE
SUBSIDENCE WILL NOT ONLY DRY THINGS OUT COMPLETELY, BUT
TEMPERATURES WILL RESPOND BY REBOUNDING TO NEAR SEASONAL
CONDITIONS ON MONDAY BEFORE TOPPING OUT OVER 10 DEGREES ABOVE
AVERAGE ON TUESDAY WITH HIGHS IN THE 80S. 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.
A WEAK FRONT AND ASSOCIATED UPPER-TROUGH IS ON TRACK TO BRUSH THE
REGION ON WEDNESDAY. POPS LOOK MINIMAL, BUT ONSHORE FLOW LOOKS TO
RETURN AND BRING COOLER, SEASONAL 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.
LONG TERM /THURSDAY THROUGH SUNDAY/
GOING INTO THE SECOND HALF
OF THE WEEK, SOME DEGREE OF UPPER-TROUGHING WILL REMAIN OVERHEAD.
WHILE THERE'S FAIRLY GOOD AGREEMENT IN THE MODELS THAT COOLER
TEMPERATURES WILL RETURN, THE ENSEMBLES ARE STILL IN DISAGREEMENT
WITH EXACT QPF POTENTIAL. 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
A COLD FRONT HAS WORKED THROUGH ALL OF WESTERN WA THIS
AFTERNOON (AND HAS MADE IT EAST OF THE CREST). FLOW ALOFT WILL
INCREASE FROM THE NORTHWEST BEHIND THE FRONT INTO MONDAY. A
CONVERGENCE ZONE WILL KEEP SHOWERS GOING INTO 06Z IN PUGET SOUND
THROUGH 06Z. CIGS THIS AFTERNOON ARE MIX BETWEEN MVFR AND VFR
(WITH LOWER CIGS IN THE INTERIOR AND COAST. BREEZY SOUTHWEST
WINDS CONTINUE AT 10-15 KT WITH GUSTS TO 25 KT STILL BEING
REPORTED. MVFR AND IFR CIGS ARE LIKELY TO REDEVELOP TONIGHT/MONDAY
MORNING BEFORE CLEARING. SOME VIS LESS THAN 3 NM IS POSSIBLE IN
THE SOUTH INTERIOR/COAST AREAS. WINDS WILL BE LIGHT OUT OF THE
SOUTH (LESS THAN 5 KT) TONIGHT AND WILL BECOME NORTHWEST 5 TO 10
KT MONDAY AFTERNOON.
KSEA...VFR CONDITIONS THIS EVENING WILL LIKELY DROP BACK TO MVFR
TONIGHT. CIGS WILL SCATTER AFTER 19-21Z MONDAY FOR VFR CONDITIONS.
BREEZY SOUTHWEST WINDS 10-15 KT GUSTS TO 25 KT WILL DIMINISH TO
UNDER 5 KT THIS EVENING, THEN TURN TO THE NORTH 5-10 KT BY MONDAY
AFTERNOON.
HPR
MARINE
HIGH PRESSURE WILL REBUILD OFFSHORE WITH A COLD
FRONT/TROUGH TO THE EAST TONIGHT/MONDAY. A PUSH THIS EVENING WILL
BRING WINDS OF 20-25 KT IN THE CENTRAL/EAST STRAIT OF JUAN DE FUCA
WATERS WITH A COUPLE BRIEF GUSTS TO 30 KT POSSIBLE (HAVE CONTINUED
THE SMALL CRAFT ADVISORY). WINDS AND SEAS WILL CONTINUE TO DECREASE
THIS AFTERNOON IN THE COASTAL WATERS POST-FRONT. AFTER MONDAY, A
THERMAL TROUGH WILL DEVELOP ALONG THE COAST LEADING TO A BRIEF
PERIOD OF OFFSHORE FLOW OVER THE WATERS GOING INTO TUESDAY. SOME
EAST WINDS MAY INCREASE IN PARTS OF THE STRAIT OF JUAN DE FUCA, WITH
ONSHORE FLOW TO FOLLOW TOWARDS MID TO LATE WEEK WITH ANOTHER SYSTEM
POTENTIALLY PASSING THROUGH.
SEAS 5-7 FT TODAY WILL DECREASE BACK TO 4-6 FT, POTENTIALLY BUILDING
BACK TO 5-7 FT TOWARDS THE END OF THE WEEK.
HPR
FIRE WEATHER
SHOWERS CONTINUE ACROSS THE CASCADES THIS AFTERNOON
IN THE WAKE OF A FRONTAL SYSTEM THAT MOVED ACROSS THE AREA THIS
MORNING. CONDITIONS WILL DRY OUT AGAIN ON MONDAY AS AN UPPER LEVEL
RIDGE STARTS TO BUILD BACK INTO THE REGION.
THE ATTENTION THEN TURNS TO TUESDAY AS A THERMAL TROUGH AT THE
SURFACE CREEPS NORTHWARD ALONG THE COAST EARLY IN THE DAY, ALLOWING
FOR FLOW TO TRANSITION TO OFFSHORE. LATEST HI-RES GUIDANCE
INDICATES EASTERLY WINDS PICKING UP ACROSS THE CASCADES DURING
THE EARLY MORNING HOURS AND PERSISTING THROUGH THE AFTERNOON,
WITH GUSTS TO 25-30 MPH POSSIBLE. EASTERLY WINDS WILL HELP TO
WARM AND DRY CONDITIONS OUT FURTHER AND COULD RESULT IN RELATIVE
HUMIDITIES FALLING INTO THE MID 20S TO LOW 30S ACROSS PORTIONS OF
THE CENTRAL AND SOUTHERN CASCADES. THIS COMBINATION OF GUSTY
EASTERLY WINDS AND LOW RHS HAS LED TO THE ISSUANCE OF A FIRE
WEATHER WATCH FOR THE CASCADE AND CASCADE FOOTHILL ZONES FOR
TUESDAY.
OVERALL, EXPECT THESE HEIGHTENED FIRE WEATHER CONDITIONS TO REMAIN
SHORT-LIVED, AS WINDS ARE ANTICIPATED TO TRANSITION BACK TO ONSHORE
BY MIDWEEK. INCREASING ONSHORE FLOW, COOLER CONDITIONS, AND THE
POTENTIAL FOR ADDITIONAL WEATHER SYSTEMS TO MOVE ACROSS THE AREA
WILL HELP MITIGATE FIRE WEATHER CONCERNS LATER IN THE WEEK.
14
SEW WATCHES/WARNINGS/ADVISORIES
WA...FIRE WEATHER WATCH FROM LATE MONDAY NIGHT THROUGH TUESDAY
EVENING FOR BLACK HILLS AND SOUTHWEST INTERIOR LOWLANDS-
NORTHEAST PUGET SOUND LOWLANDS GENERALLY BELOW 1500 FEET-
SOUTHEAST PUGET SOUND LOWLANDS GENERALLY BELOW 1500 FEET-
WEST SLOPES OF THE CENTRAL CASCADES GENERALLY ABOVE 1500
FEET-WEST SLOPES OF THE NORTH CASCADES GENERALLY ABOVE 1500
FEET.
PZ...SMALL CRAFT ADVISORY UNTIL 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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