644
FXUS66 KSEW 102137
AFDSEW
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SEATTLE WA
237 PM PDT WED SEP 10 2025
SYNOPSIS
SHOWERS OR ISOLATED THUNDERSTORMS WILL BE POSSIBLE
IN THE CASCADES AGAIN THIS AFTERNOON/EVENING. BROAD UPPER LEVEL
TROUGHING WILL SLOWLY SLIDE EAST THURSDAY AND FRIDAY, BRINGING
MOSTLY DRY CONDITIONS TO THE REGION THAT WILL PERSIST INTO
SATURDAY. BY SUNDAY, THE NEXT WEATHER SYSTEM WILL BRING A CHANCE
FOR PRECIPITATION BACK TO THE REGION.
SHORT TERM /TONIGHT THROUGH SATURDAY/
FAIRLY QUIET
CONDITIONS TODAY. LOW LEVEL STRATUS CONTINUES TO RETREAT TOWARD
THE COAST THIS AFTERNOON. THE ONLY ADDITIONAL CONCERN IS A
20-30% CHANCE OF SHOWERS AND 10-15% CHANCE OF THUNDERSTORMS
ACROSS THE CENTRAL/SOUTHERN CASCADES THIS AFTERNOON AND EVENING.
AS WE MOVE INTO THURSDAY, UPPER LEVEL RIDGING WILL BECOME THE
DOMINANT FEATURE. WE WILL SEE AN INCREASE IN MARINE STRATUS
THURSDAY MORNING AS WELL AS THE POTENTIAL FOR MORE WIDESPREAD
FOG THROUGH AT LEAST THE FIRST PART OF THE DAY. HOWEVER, THIS
HIGH PRESSURE WILL ALSO BRING DRIER CONDITIONS AND SEASONABLE
TEMPERATURES THAT WILL PERSIST THROUGH SATURDAY.
LONG TERM /SATURDAY NIGHT THROUGH WEDNESDAY/
FORECAST
CONFIDENCE IN THE DETAILS BEGINS TO WANE AS WE GET INTO SATURDAY
NIGHT AND SUNDAY. THERE HAS BEEN A TREND TOWARDS A MORE
PROGRESSIVE FRONTAL SYSTEM IMPACTING THE REGION SUNDAY, BRINGING
A QUICK SHOT OF PRECIPITATION AND A SLIGHT CHANCE OF
THUNDERSTORMS. THEN WE MAY RINSE AND REPEAT WITH TEMPORARY HIGH
PRESSURE EARLY NEXT WEEK.
-WOLCOTT-
AVIATION
CURRENTLY VFR ACROSS ALL TERMINALS THIS AFTERNOON
(EXCEPT FOR THE COAST WHICH STILL RETAINS IFR STRATUS THAT WILL
CONTINUE TO RECEDE SLOWLY OFFSHORE THROUGH THE AFTERNOON). WINDS
WILL REMAIN LIGHT OUT OF THE NORTH AT 4-8KT. WEAK FORCING PATTERN
WILL REMAIN TONIGHT INTO TOMORROW WITH AN UPPER LEVEL LOW TO THE
SOUTH, AND A NORTHEAST TILTED RIDGE UP INTO SOUTHWEST CANADA INTO
TOMORROW (LIGHT NORTHEAST FLOW). A STRONGER MARINE PUSH TONIGHT IS
EXPECTED, WHICH WILL LIKELY RESULT IN INCREASED STRATUS AND/OR FOG
COVERAGE IN THE INTERIOR (ESPECIALLY FOR THE COASTAL TERMINALS
WITH A 50-60% CHANCE OF LIFR CONDITIONS). NORTH INTERIOR TERMINALS
(FROM KPAE UP TO KBLI) ALSO HAVE A 20-30% CHANCE OF LIFR
CONDITIONS (30-50% CHANCE OF IFR CIGS). CENTRAL PUGET SOUND
TERMINALS HAVE A LOWER 20-30% CHANCE OF IFR CONDITIONS THURSDAY
MORNING. ANY LOW CIGS/VIS THAT DEVELOP OVERNIGHT WILL DIMINISH
FROM 18-21Z FROM EAST TO WEST. WINDS WILL BE LIGHT AND VARIABLE
TONIGHT, AND SWITCH TO THE SOUTHWEST 3-6 KT THURSDAY.
KSEA...VFR THROUGH TONIGHT WITH 4-8 KT NORTH WINDS. WINDS WILL
BECOME LIGHT TONIGHT AND SWITCH TO SOUTHWEST 3-6 KT THURSDAY. SOME
UNCERTAINTY REMAINS WITH HOW FAR THE STRATUS WILL MAKE IT INTO
PUGET SOUND, BUT NBM GIVES A 45% CHANCE OF MVFR, AND A 25% CHANCE
OF IFR IN THE MORNING. GIVEN THE WEAKER GRADIENTS TONIGHT, WILL
FORECAST IFR CONDITIONS IN THE MORNING.
HPR
MARINE
HIGH PRESSURE WILL REMAIN OFFSHORE WITH LOWER PRESSURE
INLAND THROUGH AT LEAST THURSDAY. A STRONGER PUSH WILL LIKELY
BRING WESTERLIES DOWN THE STRAIT OF JUAN DE FUCA THURSDAY
NIGHT/FRIDAY MORNING (HREF GIVES A 60-80% CHANCE OF SUSTAINED
WESTERLIES EXCEEDING 20 KT, AND A 80-90% CHANCE OF GUSTS EXCEEDING
20 KT). ADDITIONALLY, THE WEAKER GRADIENTS/LIGHT WINDS OVER MUCH
OF THE WATERS WILL INCREASE THE CHANCE OF FOG IN THE COASTAL
WATERS/STRAIT OF JUAN DE FUCA (30-50% CHANCE OF VISIBILITIES LESS
THAN 1 NM). A FRONT WILL THEN APPROACH THE COASTAL WATERS
SATURDAY NIGHT/SUNDAY WITH A SMALL UPTICK IN WAVES/WINDS (BUT
REMAINING BELOW ADVISORY LEVELS AT THIS TIME).
SEAS WILL RANGE 4-7 FT, THEN RISE TO 6-8 FT THROUGH THE WEEKEND
(LOW CHANCE FOR 10 FT WAVES AT THIS POINT), BUT WILL DECREASE BACK
TO 3-5 FT EARLY NEXT WEEK.
HPR
SEW WATCHES/WARNINGS/ADVISORIES
WA...NONE.
PZ...NONE.
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