076
FXUS66 KSEW 191705
AFDSEW
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SEATTLE WA
1005 AM PDT SAT SEP 19 2026
SYNOPSIS
WESTERN WASHINGTON REMAINS ON THE BACK SIDE OF AN UPPER LEVEL
RIDGE THROUGH THE WEEKEND WITH LOW LEVEL ONSHORE FLOW CONTINUING.
THE RIDGE MOVES EAST MONDAY AS A WEAK SYSTEM MOVES BY TO THE
NORTH. AN UPPER LEVEL TROUGH DEVELOPS OFFSHORE ON TUESDAY AND
REMAINING THROUGH FRIDAY. A DISSIPATING SYSTEM ARRIVES
WEDNESDAY WITH ANOTHER POSSIBLE WEAK SYSTEM ON FRIDAY.
SHORT TERM /TODAY THROUGH MONDAY/
THERE IS EXTENSIVE MARINE STRATUS THROUGHOUT PUGET SOUND THIS
MORNING WITH WESTERLY FLOW ALOFT. EXPECT LIMITED VISIBILITIES
IN CENTRAL AND SOUTHERN PUGET SOUND DUE TO FOG AND MIST. MORE
APPRECIABLE SCATTERING OF THE MARINE LAYER WILL OCCUR AFTER 19Z.
NOT MUCH GOING ON WEATHERWISE THIS WEEKEND. WESTERN WASHINGTON ON
THE BACKSIDE OF AN UPPER LEVEL RIDGE WITH WESTERLY FLOW ALOFT OVER
THE AREA. IN THE LOWER LEVELS LIGHT ONSHORE FLOW. STRATUS WILL BE
TOUGH TO GET RID OF ALONG THE COAST WITH JUST SOME LATE DAY
SUNSHINE. HIGHS MID 60S COAST AND MID 60S TO LOWER 70S INLAND.
LITTLE CHANGE IN THE PATTERN TONIGHT AND SUNDAY. ANOTHER ROUND OF
LATE NIGHT AND MORNING LOW CLOUDS WITH PATCHY FOG OVER THE INTERIOR
WHILE THE COAST STAYS MOSTLY CLOUDY. SUNSHINE IN THE AFTERNOON OVER
THE INTERIOR WILL PUT HIGHS IN THE MID 60S TO MID 70S. HIGHS ALONG
THE COAST IN THE MID 60S. IT WILL BE A COOL MORNING SUNDAY WITH LOWS
IN THE MID 40S TO LOWER 50S.
A FEW CHANGES MONDAY BUT THE FORECAST WILL REMAIN THE SAME. UPPER
LEVEL RIDGE MOVES OFF TO THE EAST WHILE A WEAK SYSTEM MOVES INLAND
WELL NORTH OF THE AREA. WEAK LOW LEVEL ONSHORE FLOW IN THE LOWER
LEVELS KEEPING THE MORNING CLOUDS AFTERNOON SUNSHINE SCENARIO
INTACT. HIGHS REMAINING IN THE MID 60S TO MID 70S WITH LOWS IN THE
MID 40S TO LOWER 50S. FELTON/21
LONG TERM /MONDAY NIGHT THROUGH FRIDAY/
MODELS IN GOOD AGREEMENT THROUGH THURSDAY WITH AN UPPER LEVEL
TROUGH OFFSHORE. DISSIPATING SYSTEM MOVING INTO THE AREA
WEDNESDAY FOR A SLIGHT CHANCE OF SHOWERS OVER THE NORTHERN
PORTION. GFS BRINGS THE TROUGH INTO THE AREA FRIDAY WHILE THE
ECMWF KEEPS THE TROUGH OFFSHORE. ENSEMBLES HAVE ENOUGH
SOLUTIONS WITH LIGHT PRECIPITATION TO PUT SLIGHT CHANCE POPS IN
THE FORECAST. SLOW COOLING TREND WITH HIGHS IN THE MID 60S TO
LOWER 70S TUESDAY DROPPING TO THE LOWER TO MID 60S BY FRIDAY.
LOWS REMAINING IN THE MID 40S TO LOWER 50S. FELTON
AVIATION
WESTERLY ZONAL FLOW WILL PREVAIL ALOFT TODAY. MARINE
STRATUS IS FIRMLY ENTRENCHED THROUGHOUT PUGET SOUND, EXCEPT FOR KBLI
WHERE CLR CONDITIONS PREVAIL. LOWER CIGS WILL STRUGGLE TO DISSIPATE
BEFORE 17Z AND WILL LIKELY BREAK UP MORE APPRECIABLY AFTER 19Z-20Z.
VFR IN THE AFTERNOON IS EXPECTED. TODAY, SOUTHERLY WINDS ARE
EXPECTED UNTIL 18Z-19Z WHEN WINDS WILL TURN WNW, BECOMING MORE NNW
BETWEEN 20Z-00Z. ANOTHER ROUND OF LOW STRATUS CLOUDS LOOKS LIKELY
TOMORROW MORNING, SETTING IN AFTER 12Z AND LASTING THROUGH MUCH OF
SUNDAY MORNING.
KSEA...LIFR CIGS PRESENTLY AT THE TERMINAL THIS MORNING, WITH
LIMITED VISBYS BEYOND 3SM AND CIGS AS LOW AS 300 FT. OSCILLATIONS
BETWEEN LIFR AND IFR CIGS ARE LIKELY BETWEEN NOW AND 19Z AS THE
STRATUS REMAINS FIRMLY IN PLACE. GENERAL SCATTERING AND IMPROVEMENT
ISN'T EXPECTED BEFORE 19Z-20Z AND WILL BE GRADUAL. WINDS WILL BE
LIGHT OUT OF THE SSW THIS MORNING, BECOMING MORE WESTERLY AROUND THE
SAME TIME AS THE CIG AND VIS IMPROVEMENTS. A SWITCH TO A LIGHT
NORTHERLY IS FORECAST AFTER 20Z. SPEEDS WILL BE 5 KTS OR LESS
THROUGHOUT THE PERIOD. THERE IS A 30% CHANCE OF IFR (50% CHANCE OF
MVFR) CIGS RETURNING TO THE TERMINAL EARLY TOMORROW MORNING AROUND
13Z.
21
MARINE
WEAK ONSHORE FLOW WILL CONTINUE INTO NEXT WEEK AS BROAD HIGH
PRESSURE REMAINS OVER THE OFFSHORE WATERS. WEAKENING FRONTAL
SYSTEMS MOVING BY TO THE NORTH THROUGH NEXT WEEK WILL HELP TO
INCREASE ONSHORE FLOW, ALLOWING FOR INCREASED CHANCES FOR SMALL
CRAFT ADVISORY CONDITIONS EACH EVENING WITH WESTERLY PUSHES
THROUGH THE STRAIT OF JUAN DE FUCA. PUSHES WILL BEGIN TO
INCREASE TONIGHT AND SUNDAY EVENING, BUT WILL MOST LIKELY
REMAIN BELOW THRESHOLDS. CHANCES FOR MEETING SMALL CRAFT
THRESHOLDS RISE TO 50-80% BY MONDAY EVENING, WITH SLIGHTLY LOWER
CHANCES ON TUESDAY EVENING.
SEAS REMAIN 3 TO 5 FT UNTIL MONDAY AS INCOMING SWELL RISES SEAS
TO AROUND 6 TO 8 FT. SEAS REMAIN IN THAT RANGE THROUGH MID-WEEK.
62
FIRE WEATHER
WHILE GENERAL LOW-LEVEL ONSHORE FLOW WILL MAINTAIN CLOUD COVER
AND HIGHER HUMIDITIES ACROSS THE REGION, EXPECT TO SEE SOME
LIGHT NORTH OR NORTHEAST WINDS NEAR THE CASCADES TONIGHT THROUGH
SUNDAY, WITH SUNDAY AFTERNOON RH VALUES APPROACHING THE 30-35%
RANGE. GIVEN THE OVERALL PATTERN, CONCERNS REMAIN MINIMAL
THROUGH MUCH OF THE WEEK AHEAD, WITH COOLER TEMPERATURES AND
RAIN CHANCES RETURNING BY THE MIDDLE OF NEXT WEEK.
SEW WATCHES/WARNINGS/ADVISORIES
WA...NONE.
PZ...NONE.
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