282
FXUS66 KSEW 082204
AFDSEW
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SEATTLE WA
304 PM PDT WED OCT 8 2025
SYNOPSIS
A DEEP UPPER LOW OFFSHORE WILL LINGER ALONG THE
WEST COAST THROUGH FRIDAY, RESULTING IN PERIODIC SHOWERS. UPPER
TROUGHING WILL BE REINFORCED OVER THE PACIFIC NORTHWEST OVER
THE WEEKEND INTO EARLY NEXT WEEK WITH COOLER TEMPERATURES AND
CONTINUED UNSETTLED WEATHER.
SHORT TERM /TODAY THROUGH FRIDAY/
DRIER WEATHER CONTINUES
THIS AFTERNOON WITH A MIX OF CLOUDS AND SUNSHINE AS AN UPPER LOW
DEEPENS OFFSHORE OF THE PACIFIC NORTHWEST. THE UPPER LOW WILL BE
SITUATED OFFSHORE OF THE OREGON COAST TONIGHT INTO FRIDAY AND BE
THE PRIMARY WEATHER FEATURE OVER THE NEXT FEW DAYS. GIVEN THE
POSITION OF THE UPPER LOW, SOUTH-SOUTHEASTERLY FLOW ALOFT WILL
INCREASE TONIGHT. SHOWERS ARE INITIALLY EXPECTED TO DEVELOP OVER
THE OREGON & WASHINGTON CASCADES LATER THIS EVENING, AND MOVE
NORTHWARDS INTO THURSDAY MORNING. DESPITE THE CONVECTIVE NATURE
OF THE PRECIPITATION, THUNDERSTORM CHANCES TONIGHT INTO
THURSDAY REMAIN LIMITED DUE TO A LACK OF INSTABILITY. ANOTHER
ROUND OF SHOWERS ARE EXPECTED AGAIN THURSDAY NIGHT INTO FRIDAY.
ALTHOUGH MUCAPE VALUES ARE LIMITED FRIDAY (LESS THAN 100 J/KG),
WILL NEED TO MONITOR ANY EMBEDDED THUNDERSTORM IN SHOWERS, AND
AS SUCH A GENERAL THUNDERSTORM RISK HAS BEEN INCLUDED FOR
PORTIONS OF WESTERN WASHINGTON FROM STORM PREDICTION CENTER.
OTHERWISE, THERE WILL BE BREAKS IN PRECIPITATION, PARTICULARLY
EACH AFTERNOON, WITH SOME SUNSHINE AS WELL. TEMPERATURES WILL BE
NEAR NORMAL THROUGH FRIDAY, WITH HIGHS IN THE UPPER 50S TO MID
60S.
LONG TERM /SATURDAY THROUGH WEDNESDAY/
THE AFOREMENTIONED
UPPER LOW OFFSHORE WILL MOVE INLAND OVER OREGON ON SATURDAY.
DURING THIS TIME, TROUGHING WILL BE REINFORCED OVER WESTERN
WASHINGTON AS AN UPPER LOW DIVES SOUTHWARDS OUT OF BC AND
DEEPENS ACROSS THE PACIFIC NORTHWEST SUNDAY. ALTHOUGH THERE IS
SOME UNCERTAINTY INTO THE LOCATION OF THE UPPER LOW BY TUESDAY
NEXT WEEK, THE UPPER LOW LOOKS TO CONTINUE TO DEEPEN TOWARDS
CALIFORNIA. THIS WILL RESULT IN UNSETTLED WEATHER SATURDAY
THROUGH AT LEAST MONDAY FOR WESTERN WASHINGTON. FURTHERMORE,
TEMPERATURES WILL ALSO BECOME SIGNIFICANTLY COOLER SUNDAY INTO
MONDAY, ESPECIALLY OVER THE MOUNTAINS. SNOW LEVELS INITIALLY
AROUND 6000 FEET EARLY SATURDAY WILL FALL TO 3000 TO 4000 FEET
BY MONDAY. HIGHER ELEVATION MOUNTAIN SNOWFALL IS EXPECTED DURING
THIS PERIOD. AT THIS TIME, NBM PROBABILITIES OF 3" OF SNOW (72
HOURS ENDING TUESDAY) RANGES 80 TO 95% FOR RAINY PASS AND
PARADISE, WITH PROBABILITIES OF 50 TO 75% FOR STEVENS PASS AND
HEATHER MEADOWS. FOR THOSE HEADING INTO THE HIGHER ELEVATIONS
OF THE CASCADES AND OLYMPICS SATURDAY INTO MONDAY, CONTINUE TO
MONITOR THE WEATHER FORECAST, AND PREPARE FOR SNOW AND MUCH
COOLER TEMPERATURES.
PRECIPITATION POTENTIAL BEGINS TO TAPER OFF LATE MONDAY INTO
MIDWEEK AS THE UPPER LOW CONTINUES TO DEEPEN SOUTHWARDS INTO
CALIFORNIA. OVERNIGHT TEMPERATURES EARLY NEXT WEEK MAY DIP INTO
THE 30S FOR AREAS AWAY FROM THE WATER, AND AS SUCH WILL NEED TO
MONITOR ANY FROST POTENTIAL. OTHERWISE, HIGH TEMPERATURES WILL
TREND A FEW DEGREES BELOW NORMAL EARLY NEXT WEEK. JD
AVIATION
AN UPPER-LOW WILL CONTINUE TO SPIN OFFSHORE AS
IT SINKS SOUTHWARD THROUGHOUT THE TAF PERIOD. SOUTHWEST FLOW ALOFT
TURNING MORE SOUTH-SOUTHEASTERLY TONIGHT THROUGH THURSDAY. VFR
CONDITIONS THIS AFTERNOON AND GENERALLY OVERNIGHT INTO THURSDAY.
THERE'S A CHANCE OF MVFR CIGS DEVELOPMENT ACROSS THE INTERIOR
HOWEVER, A MID-LEVEL CLOUD DECK CAUSED BY AN OFFSHORE DISTURBANCE
SHOULD DISCOURAGE LOW-CLOUD DEVELOPMENT. HIGH-BASED RAIN SHOWERS ARE
TRENDING MORE LIKELY (50-75% CHANCE) FOR THURSDAY MORNING BUT
IMPACTS TO VISIBILITY AREN'T EXPECTED. VFR IS IN THE FORECAST FOR
THE REST OF THE DAY ON THURSDAY AS WELL.
KSEA...CONFIDENCE IS LEANING TOWARDS VFR CONDITIONS THROUGHOUT THE
TAF PERIOD. MID TO HIGH LEVEL CLOUDS WILL INCREASE LATE TONIGHT INTO
EARLY THURSDAY MORNING AS RAIN AND SHOWERS SPREAD INTO THE INTERIOR
FROM THE SOUTHWEST. SW SURFACE WINDS 5-10 KT INTO THIS EVENING;
BECOMING LIGHT AND MORE NORTHEASTERLY 3-6 KT OR AFTER 03Z THURSDAY
THROUGH THE OVERNIGHT PERIOD. WINDS RETURN MORE NORTHERLY ON
THURSDAY.
MCMILLIAN
MARINE
A WEATHER SYSTEM WILL BE LOCATED OFFSHORE OF OREGON
INTO FRIDAY. PERIODIC SHOWERS MAY RESULT IN ELEVATED WINDS AT
TIMES, PARTICULARLY FOR THE COASTAL WATERS ON THURSDAY. ALTHOUGH
SOUTHEAST WINDS FOR THE COAST ARE EXPECTED TO REMAIN BELOW SMALL
CRAFT ADVISORY THRESHOLD ON THURSDAY, BRIEF SCA WIND GUSTS ARE
POSSIBLE. OTHERWISE, THE WEATHER SYSTEM OFFSHORE WILL MOVE
INLAND AND WEAKEN ON FRIDAY. A SECONDARY WEATHER SYSTEM WILL
THEN DEVELOP OVER THE AREA SATURDAY, RESULTING IN INCREASED
WINDS. SCA WINDS FOR THE COASTAL WATERS AND STRAIT OF JUAN DE
FUCA ARE EXPECTED SATURDAY INTO EARLY SUNDAY. THERE ALSO REMAINS
A 40 TO 70% CHANCE OF GALE FORCE WIND GUSTS FOR THESE AREAS.
WINDS THEN LOOK TO TRANSITION MORE NORTHEASTERLY EARLY NEXT
WEEK.
SEAS OF 6 TO 8 FEET INTO TONIGHT WILL SUBSIDE TO 4 TO 6 FEET ON
FRIDAY. SEAS THEN WILL BUILD TO NEAR 12 TO 16 FEET OVER THE
WEEKEND ASSOCIATED WITH THE WEATHER SYSTEM. DOMINANT PERIOD OF 9
TO 12 SECONDS WILL CONTINUE THROUGH FRIDAY. JD
SEW WATCHES/WARNINGS/ADVISORIES
WA...NONE.
PZ...NONE.
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