200
FXUS66 KSEW 141555
AFDSEW
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SEATTLE WA
855 AM PDT MON SEP 14 2026
SYNOPSIS
UPPER LEVEL LOW WELL TO THE EAST THIS MORNING WITH NORTHWESTERLY
FLOW ALOFT. UPPER LEVEL TROUGH MOVING DOWN FROM THE NORTH
MOVING THROUGH TUESDAY MORNING. UPPER LEVEL RIDGE BUILDING
OFFSHORE TUESDAY NIGHT WILL MOVE OVER THE AREA WEDNESDAY. BRIEF
SPELL OF OFFSHORE FLOW WEDNESDAY NIGHT WITH A THERMALLY INDUCED
SURFACE TROUGH ALONG THE COAST. THE TROUGH WILL SHIFT INLAND
THURSDAY. FLAT UPPER LEVEL RIDGE INTO THE WEEKEND WITH LOW LEVEL
ONSHORE KEEPING TEMPERATURES NEAR NORMAL.
SHORT TERM /TODAY THROUGH WEDNESDAY/
THE LATEST FORECAST REMAINS ON TRACK THIS MORNING WITH NO
UPDATES. NORTHWESTERLY FLOW ALOFT WITH LOW LEVEL ONSHORE FLOW
WILL PRODUCE A MOSTLY CLOUDY DAY TODAY. WEAK CONVERGENCE THIS
MORNING OVER SNOHOMISH AND NORTHERN KING COUNTY COULD PRODUCE A
LIGHT SHOWER OR SOME DRIZZLE. WITH THE CLOUD COVER HIGH
TEMPERATURES WILL REMAIN BELOW NORMAL, IN THE 60S.
UPPER LEVEL TROUGH DROPPING DOWN THE BRITISH COLUMBIA COASTLINE
STILL NORTH OF WESTERN WASHINGTON AT 12Z TUESDAY. LOW LEVEL
ONSHORE FLOW WEAKENING WITH SOME BREAKS IN THE CLOUD COVER IN
THE EVENING. WITH ALL THE LOW LEVEL MOISTURE AROUND FROM THE
RAINS SUNDAY CLOUDS FILLING BACK IN OVERNIGHT. LOWS IN THE MID
40S TO MID 50S.
UPPER LEVEL TROUGH MOVING THROUGH TUESDAY MORNING WITH ISOLATED
LIGHT SHOWERS OR AREAS OF DRIZZLE OVER THE NORTHERN PORTION OF
THE AREA. DRY NORTHERLY FLOW ALOFT BEHIND THE TROUGH IN THE
AFTERNOON WITH SKIES CLEARING FROM THE NORTH. ANOTHER DAY OF
BELOW NORMAL HIGH TEMPERATURES IN THE 60S.
SKIES CONTINUING TO CLEAR TUESDAY NIGHT. LIGHT FLOW IN THE LOWER
LEVELS. WITH THE LONGER NIGHTS THIS TIME OF YEAR PLUS THE LOW
LEVEL MOISTURE AREAS OF FOG FORMING. LOWS IN THE MID 40S TO
LOWER 50S. THERE IS AN OUTSIDE CHANCE SEATTLE DROPS INTO THE
40S. THE LAST TIME SEATTLE HAD A LOW IN THE 40S WAS JUNE 8TH
( 49 DEGREES ).
UPPER LEVEL RIDGE BUILDING OFFSHORE NOSING INTO THE AREA
WEDNESDAY. WHAT FOG THAT DOES FORM WILL BE SHALLOW AND DISSIPATE
IN THE MORNING. UNDER SUNNY SKIES HIGH TEMPERATURES WARMING
INTO THE 70S.
FELTON
LONG TERM /WEDNESDAY NIGHT THROUGH SUNDAY/
EXTENDED MODELS IN GOOD AGREEMENT WITH A THERMALLY INDUCED
SURFACE TROUGH DEVELOPING ALONG THE COAST WEDNESDAY NIGHT FOR A
BRIEF SPELL OF LIGHT OFFSHORE FLOW. THE TROUGH SHIFTS INLAND
DURING THE DAY THURSDAY. LOWS IN THE UPPER 40S TO MID 50S.
HIGHS IN THE 70S WITH THE WARMEST LOCATIONS GETTING INTO THE
LOWER 80S.
UPPER LEVEL RIDGE REMAINING OVER THE AREA THURSDAY INTO THE
WEEKEND WITH VARYING DEGREES OF ONSHORE FLOW. HIGHS DROPPING
BACK INTO THE MID TO UPPER 60S ALONG THE COAST WITH THE INCREASE
IN THE ONSHORE FLOW FRIDAY. HIGHS OVER THE INTERIOR IN THE 70S.
MARINE LAYER ALONG THE COAST IN THE LATE NIGHT AND MORNING
HOURS OVER THE WEEKEND STAYING WEST OF PUGET SOUND. HIGH
TEMPERATURES COOLING DURING THE WEEKEND INTO THE MID 60S ON THE
COAST AND MID 60S TO LOWER 70S INLAND.
FELTON
AVIATION
NORTHWEST FLOW ALOFT WILL SHIFT MORE WESTERLY LATE TONIGHT AS A
WEAK UPPER TROUGH DIPS SOUTHWARD INTO WESTERN WASHINGTON. LOW
LEVEL ONSHORE FLOW WILL WEAKEN TODAY. RESIDUAL LOW LEVEL
MOISTURE FROM A DEPARTING SYSTEM ALONG WITH ONSHORE FLOW WILL
LEAD TO A MIXED BAG OF MVFR AND VFR CEILINGS THIS MORNING.
CEILINGS WILL GRADUALLY LIFT BACK TO VFR MOST AREAS AFTER 21Z
THIS AFTERNOON.
KSEA...PERIODS OF HIGH END MVFR CEILINGS ARE EXPECTED THIS MORNING
BEFORE LIFTING TO VFR THIS AFTERNOON. SURFACE WINDS SOUTHERLY 7 TO
10 KNOTS WILL EASE TO SOUTHWESTERLY 4 TO 7 KNOTS THIS AFTERNOON. A
GRADUAL SHIFT TO LIGHT NORTH/NORTHEASTERLY WIND IS EXPECTED AROUND
04Z TO 07Z TONIGHT.
33/27
MARINE
ONSHORE FLOW WILL WEAKEN TODAY THEN TURN MORE NORTHERLY ON
TUESDAY. THERMALLY INDUCED LOW PRESSURE EXPANDING NORTHWARD
ALONG THE COAST WILL LEAD TO MORE NORTHERLY OR OFFSHORE FLOW
WEDNESDAY AND THURSDAY. ONSHORE FLOW WILL RETURN FRIDAY INTO THE
WEEKEND AS A SERIES OF SYSTEMS PASS WELL NORTH OF THE AREA.
27
FIRE WEATHER
FIRE WEATHER CONCERNS REMAIN MINIMAL THROUGH THE NEXT WEEK.
RAINS FROM SUNDAY INCREASED FUEL MOISTURE ACROSS AT LEAST THE
SOUTHERN HALF OF THE REGION. THE PATTERN TURNS DRIER AND WARMER
MID TO LATE WEEK, WITH THE SURFACE WINDS GOING LIGHT OFFSHORE
BRIEFLY WEDNESDAY NIGHT INTO THURSDAY. THIS WILL DROP DAYTIME
MINIMUM RELATIVE HUMIDITY JUST BELOW 30%, WHICH WILL ALLOW MORE
REACTIVE FUELS TO START TO DRY OUT. THE OFFSHORE FLOW WILL BE
SHORT LIVED WITH THE LOW LEVEL FLOW TURNING BACK ONSHORE
THURSDAY NIGHT INTO FRIDAY EASING ANY FIRE WEATHER CONCERNS.
FELTON
SEW WATCHES/WARNINGS/ADVISORIES
WA...NONE.
PZ...NONE.
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