729
FXUS66 KSEW 142020
AFDSEW
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SEATTLE WA
120 PM PDT WED OCT 14 2026
SYNOPSIS
HIGH PRESSURE WILL BUILD INTO THE NORTHWEST THROUGH THE REST OF
THE WEEK, BEFORE BECOMING UNSETTLED AGAIN AS A SERIES OF WEAK
SYSTEMS TRAVERSE THE AREA OVER THE WEEKEND. THE PATTERN LOOKS TO
REMAIN UNSETTLED INTO THE FIRST HALF OF NEXT WEEK WITH COOLER
TEMPERATURES IN THE FORECAST.
SHORT TERM /TONIGHT THROUGH FRIDAY NIGHT/
SKIES HAVE BEGUN TO CLEAR EARLY THIS AFTERNOON WITH RESIDUAL
CLOUD COVER LINGERING ALONG THE COAST AND SOUTHWEST INTERIOR.
HIGH PRESSURE IS BUILDING IN EARNEST TODAY THROUGH THE END OF
THE WEEK, WITH HIGHS CLIMBING INTO THE UPPER 60S AND LOW 70S
TOMORROW, AND AGAIN ONCE MORE INTO THE MID 70S BY FRIDAY. THIS
WILL CORRESPOND TO SOME MINOR HEATRISK OVER THESE TWO DAYS.
GIVEN A MOIST ATMOSPHERE IN THE LOW LEVELS AND A LIGHT WIND
GRADIENT, THERE IS POTENTIAL FOR SOME STRATUS AND POSSIBLY FOG
ON THURSDAY MORNING. OFFSHORE FLOW WILL GET A LITTLE BREEZY,
PARTICULARLY IN THE CASCADES AND FOOTHILLS THURSDAY NIGHT. GUSTS
WILL BE BETWEEN 25-30 MPH. RH VALUES IN THE CASCADES AND
SOUTHERN OLYMPICS COULD SEE MINIMUMS AROUND 35-40%, WITH A MORE
WIDESPREAD REDUCTION ON FRIDAY AS THE TEMPERATURES CLIMB.
MINIMUMS ON FRIDAY WILL RANGE FROM 35-45%.
LONG TERM /SATURDAY THROUGH WEDNESDAY/
HIGH PRESSURE DAMPENS OVER THE WEEKEND, WITH MORE SOUTHWESTERLY
FLOW ALOFT. THE NEXT SYSTEM ARRIVES ON SATURDAY, LIKELY BRINGING
RAIN TO WESTERN WASHINGTON THROUGHOUT THE DAY. MORE OF THIS RAIN
IS FORECAST TO FALL IN THE NORTH CASCADES WITH ONLY A FEW
HUNDREDTHS OF AN INCH EXPECTED IN LOWLAND LOCATIONS. AREAS OF
THE SEATTLE METRO MAY BE SHADOWED ENTIRELY. MORE NOTABLY,
TEMPERATURES DROP BACK INTO THE LOW 60S WHICH WILL BE A SHARP
DROP OUT OF FRIDAY'S HIGHS IN THE MID 70S.
ZONAL FLOW WITH BROAD TROUGHING IN THE NE PACIFIC KEEPS
CONDITIONS COOLER AND DRIER ON SUNDAY. MORNING LOWS WILL DROP
INTO THE LOW 40S FOR THE PUGET SOUND REGION, AND MID 30S IN THE
CASCADE FOOTHILLS. MODEL GUIDANCE IS STILL KEEPING THAT TROUGH
OFFSHORE INTO SUNDAY FOR LESS OF A WIND THREAT IN WESTERN
WASHINGTON, BUT THIS TRACK WILL BE MONITORED FOR CHANGES.
TROUGHING WILL CONTINUE INTO EARLY NEXT WEEK FOR ADDITIONAL
CHANCES FOR LIGHT RAIN, PARTICULARLY ON TUESDAY. BEYOND THAT,
THERE IS A BIT OF A DISCREPANCY IN WHAT PATTERN IS FAVORED.
21
AVIATION
HIGH PRESSURE BUILDING INTO THE REGION ALOFT WILL ALLOW FOR
NORTHERLY FLOW IN THE MID LEVELS TO BECOME MORE SOUTHERLY BY
THURSDAY MORNING. CLOUDS CONTINUE TO SCATTER ACROSS THE REGION
THIS AFTERNOON, ALLOWING FOR CONDITIONS TO GRADUALLY IMPROVE
ACROSS THE AREA TERMINALS. CEILINGS ARE MOSTLY MVFR TO VFR, WITH
THE EXCEPTION OF IFR LINGERING IN THICKER CLOUD COVER ALONG THE
COAST. EXPECT CEILINGS TO CONTINUE TO SCATTER THROUGH THE
AFTERNOON FOR A RETURN TO MOSTLY VFR CONDITIONS BY THIS
EVENING. SOUTHWESTERLY WINDS BETWEEN 4-8 KT WILL BECOME LIGHT
AND VARIABLE THROUGH THE AFTERNOON HOURS BEFORE SWITCHING TO
NORTHERLY AROUND 00Z. WINDS WILL GENERALLY REMAIN LIGHT, AT 6
KT OR LESS, THROUGH THE OVERNIGHT PERIOD. CLEARING SKIES, LIGHT
WINDS, AND AMPLE LOW LEVEL MOISTURE WILL ALLOW FOR LOW STRATUS/FOG
DEVELOPMENT OVERNIGHT INTO THURSDAY MORNING. IFR/LIFR CONDITIONS
WILL BE LIKELY FOR TERMINALS IN FOG, WITH FOG EXPECTED TO SCATTER
BY LATE MORNING.
KSEA...VFR CONDITIONS WILL CONTINUE THROUGH THIS EVENING. FOG
WILL LIKELY MOVE INTO THE TERMINAL EARLY THURSDAY MORNING, WITH
PROBABILISTIC GUIDANCE SUGGESTING A 25-35% CHANCE OF CEILINGS
AND VISIBILITIES DROPPING TO LIFR BETWEEN 9-12Z. SOUTHWESTERLY
WINDS THIS AFTERNOON WILL SWITCH TO NORTH/NORTHEAST BETWEEN
22-01Z AND REMAIN LIGHT AT 6 KT OR LESS. WINDS WILL SHIFT TO THE
NORTHEAST BY THURSDAY MORNING AND INCREASE TO 4-8 KT BY THE
AFTERNOON.
14
MARINE
HIGH PRESSURE WILL BUILD BACK INTO THE COASTAL WATERS TONIGHT,
WHILE A THERMAL TROUGH BUILDS NORTHWARD ALONG THE COAST. AREAS
OF FOG WILL LIKELY DEVELOP ACROSS PORTIONS OF THE LOCAL WATERS
OVERNIGHT INTO THURSDAY MORNING AND MAY CAUSE VISIBILITIES TO
DROP DOWN TO 1 NM OR LESS IN SPOTS THROUGH THE EARLY MORNING HOURS.
WINDS WILL TURN OFFSHORE BY TONIGHT AND WILL PERSIST THROUGH
FRIDAY MORNING, BECOMING BREEZY THROUGH THE GAPS IN TERRAIN
THURSDAY AFTERNOON AND EVENING. AT THIS TIME, WINDS ARE STILL
FAVORED TO REMAIN BELOW SMALL CRAFT CRITERIA, WITH PROBABILISTIC
GUIDANCE ONLY HIGHLIGHTING A 30-40% CHANCE OF GUSTS EXCEEDING 21
KT ACROSS THE WEST ENTRANCE OF THE STRAIT OF JUAN DE FUCA AND A
SMALL PORTION OF THE NORTHERN COASTAL WATERS.
THE THERMAL TROUGH WILL PUSH INLAND ON FRIDAY AS A FRONT
APPROACHES THE AREA, BRINGING THE RETURN OF ONSHORE FLOW TO THE
WATERS. ONSHORE FLOW WILL THEN INCREASE FRIDAY NIGHT INTO
SATURDAY AS THE SYSTEM MAKES ITS WAY ACROSS THE AREA. ANOTHER
SYSTEM MAY APPROACH THE AREA WATERS SUNDAY NIGHT INTO MONDAY,
THOUGH THERE REMAIN DISCREPANCIES IN REGARDS TO ITS EXACT TRACK.
SEAS WILL LARGELY PERSIST BETWEEN 4-7 FT THROUGH FRIDAY, BUT
WILL STEADILY BUILD TOWARDS 8-11 FT OVER THE WEEKEND AS SYSTEMS
MOVE THROUGH THE REGION. SEAS COULD EVEN BUILD FURTHER EARLY
NEXT WEEK DEPENDING ON THE TRACK OF THE SYSTEMS, WITH THE GEFS
STILL INDICATING A 40-50% OF SEAS EXCEEDING 12 FT ON MONDAY.
14
SEW WATCHES/WARNINGS/ADVISORIES
WA...NONE.
PZ...NONE.
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