775
FXUS66 KSEW 102221
AFDSEW
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SEATTLE WA
321 PM PDT SAT OCT 10 2026
SYNOPSIS
A LOW PRESSURE SYSTEM WILL SLOWLY MOVE SOUTHEASTWARD TONIGHT,
WITH SCATTERED SHOWERS TAPERING OFF BY THIS EVENING. HIGH
PRESSURE BUILDING OVERHEAD WILL BRING DRIER CONDITIONS AND NEAR-
NORMAL TEMPERATURES INTO EARLY NEXT WEEK. COOLER AND UNSETTLED
CONDITIONS MAY RETURN MID-WEEK WITH A SERIES OF SYSTEMS MOVING
INLAND AIMED AT VANCOUVER ISLAND. HIGH PRESSURE WILL RETURN BY
THE END OF THE WEEK, ALLOWING FOR DRIER AND WARMER CONDITIONS
THURSDAY AND FRIDAY.
SHORT TERM /TONIGHT THROUGH MONDAY NIGHT/
A LOW PRESSURE SYSTEM WILL SLOWLY MEANDER SOUTHEASTWARD INTO
SUNDAY, WITH WRAP AROUND MOISTURE MAINTAINING LIGHT SHOWER
ACTIVITY ACROSS THE PACIFIC NORTHWEST THROUGH THE EVENING. MOST
AREAS ACROSS WESTERN WASHINGTON WILL SEE HIGH TEMPERATURES SHY
OF 60 DEGREES TODAY. AS THE UPPER LOW MOVES SOUTHEASTWARD, DRY
NORTHEAST FLOW ALOFT FILLING IN BEHIND WILL BRING IN COOLER AIR
WITH LOWS EXPECTED TO DIP INTO THE MID 30S TO MID 40S. THIS
WILL LIKELY ALLOW FROST TO FORM EARLY SUNDAY MORNING FOR
PORTIONS OF THE SOUTHERN CASCADE FOOTHILLS AND VALLEYS AND AREAS
SOUTH OF THE OLYMPICS, AND A FROST ADVISORY REMAINS IN EFFECT
FOR SUNDAY MORNING.
WEAK RIDGING WILL BUILD INTO BRITISH COLUMBIA ON SUNDAY WITH
CONTINUED DRY NORTHEAST FLOW ALOFT OVER WESTERN WASHINGTON,
BRINGING SLIGHTLY WARMER DAYTIME TEMPERATURES IN THE MID 50S TO
LOWER 60S. SKIES WILL BE MOSTLY CLEAR SUNDAY INTO SUNDAY NIGHT,
WITH EVEN COOLER OVERNIGHT TEMPERATURES GENERALLY IN THE 30S FOR
MOST AREAS. FROST WILL LIKELY BE MORE WIDESPREAD EARLY MONDAY
MORNING, AND A FROST ADVISORY REMAINS IN EFFECT FOR MOST AREAS
SOUTH OF SEATTLE AND ALONG THE HOOD CANAL AND NORTH COAST FOR
MONDAY MORNING.
THE UPPER LEVEL RIDGE AXIS OVER BRITISH COLUMBIA WILL SHIFT
SOUTHWARD OVER THE PACIFIC NORTHWEST ON MONDAY, BRINGING MORE
WARMING TO THE REGION. HIGHS WILL PEAK NEAR NORMAL UNDER SUNNY
SKIES, REACHING THE UPPER 50S TO MID 60S.
LONG TERM /TUESDAY THROUGH SATURDAY/
CLOUD COVER WILL INCREASE OVER WESTERN WASHINGTON ON TUESDAY AS
A WEAK ATMOSPHERIC RIVER BRINGS AMPLE MOISTURE TO BRITISH
COLUMBIA. WHILE THE MAJORITY OF THE PRECIPITATION IS EXPECTED TO
STAY NORTH, CHANCES FOR RAIN INCREASE ON TUESDAY ALONG THE
COAST AND OVER HIGHER TERRAIN. THE DECAYING ATMOSPHERIC RIVER
SYSTEM IS SET TO SHIFT SOUTHWARD LATE TUESDAY INTO WEDNESDAY,
BRINGING INCREASING CHANCES FOR RAIN ACROSS WESTERN WASHINGTON.
HOWEVER, THE PATH OF THE ATMOSPHERIC RIVER REMAINS FAIRLY
UNCERTAIN AT THIS TIME, WITH MANY ENSEMBLE MEMBERS KEEPING
WESTERN WASHINGTON ON THE DRY SIDE.
A HIGH PRESSURE RIDGE WILL THEN BUILD INTO THE PACIFIC NORTHWEST
ON THURSDAY AS ANOTHER ATMOSPHERIC RIVER SYSTEM TRAVERSES WELL
TO THE NORTH. THIS WILL BRING A FEW DAYS OF WARMING AND DRYING,
WITH LOW LEVEL OFFSHORE FLOW AND HIGHS REACHING THE LOWER 70S BY
FRIDAY. SOME UNCERTAINTY REMAINS OVER HOW LONG THE HIGH PRESSURE
WILL REMAIN IN PLACE, WITH POTENTIAL FOR TROUGHING TO BREAK DOWN
THE RIDGE BY THE WEEKEND AND BRING IN SOME MORE RAINFALL AND
COOLER TEMPERATURES.
15
AVIATION
VFR CONDITIONS FAVORED TODAY AND TOMORROW. HOWEVER, LOW CLOUDS IN
THE AREA MAY CAUSE CEILINGS TO BOUNCE AT TIMES TO MVFR. SCATTERED
SHOWERS CONTINUE TO MOVE ACROSS THE AREA ASSOCIATED WITH A LOW
PRESSURE SYSTEM OVER WASHINGTON. SHOWER ACTIVITY EXPECTED TO SUBSIDE
LATER THIS AFTERNOON. FOG MAY FORM SUNDAY MORNING, WITH THE HIGHEST
CHANCES OF SEEING LIFR CONDITIONS IN THE SOUTHERN INTERIOR AND
MOUNTAIN VALLEYS. BREEZY NORTHERLY WINDS ACROSS PUGET SOUND
TERMINALS AND NORTHERN INTERIOR (BLI) WITH GUSTS TO 15 KT POSSIBLE
THIS AFTERNOON. BREEZY CONDITIONS EXPECTED AGAIN SUNDAY AFTERNOON
ACROSS PUGET SOUND AND NORTHERN INTERIOR WITH WINDS 8-12 KT AND
GUSTS 20-25 KT.
KSEA...VFR CONDITIONS TODAY AND TOMORROW. BREEZY NORTHERLIES THIS
AFTERNOON 6-10 KT WITH GUSTS TO 15 KT POSSIBLE AT TIMES, EASING LATE
THIS EVENING TO 5-6 KT. NORTHERLY WINDS WILL INCREASE AGAIN SUNDAY
AFTERNOON TO 8-11 KT AND GUSTS TO 20 KT. FOG MAY FORM NEAR THE
TERMINAL, BUT NOT EXPECTED TO BRING DIRECT IMPACTS TO THE TERMINAL.
29
MARINE
A LOW PRESSURE SYSTEM OVER THE AREA WILL MOVE SOUTHWARDS TODAY. HIGH
PRESSURE BUILDING OVER THE INTERIOR OF BRITISH COLUMBIA WILL LEAD TO
INCREASING NORTHERLY OR OFFSHORE FLOW TONIGHT INTO SUNDAY. THIS WILL
RESULT IN ENHANCED WINDS OVER THE NORTHERN INLAND WATERS NEAR THE
SAN JUAN ISLANDS, FOR WHICH A SMALL CRAFT ADVISORY HAS BEEN ISSUED.
ADDITIONALLY NORTHERLY WINDS WILL INCREASE ACROSS PUGET SOUND SUNDAY
AFTERNOON, WITH THE 70-80% POSSIBILITY FOR WIND GUSTS TO EXCEED 21
KT. WINDS WILL EASE EARLY NEXT WEEK AS HIGH PRESSURE OVER BRITISH
COLUMBIA WEAKENS AND BROAD SURFACE RIDGING REMAINING OFFSHORE. A
WEAK FRONTAL SYSTEM WILL MOVE ACROSS THE WATERS LATE TUESDAY NIGHT
INTO WEDNESDAY.
SEAS WILL HOVER AROUND 6-9 FEET THIS WEEKEND, DECREASING TO 4-6 FEET
EARLY NEXT WEEK. SEAS WILL BRIEFLY BUILD ON WEDNESDAY BUT WILL
REMAIN BELOW 10 FEET.
29/27
SEW WATCHES/WARNINGS/ADVISORIES
WA...FROST ADVISORY FROM MIDNIGHT TONIGHT TO 8 AM PDT SUNDAY FOR
FOOTHILLS AND VALLEYS OF PIERCE AND SOUTHERN KING
COUNTIES-FOOTHILLS AND VALLEYS OF THURSTON AND LEWIS
COUNTIES-MIDDLE CHEHALIS RIVER VALLEY.
FROST ADVISORY FROM MIDNIGHT SUNDAY NIGHT TO 8 AM PDT MONDAY
FOR EASTERN KITSAP COUNTY-FOOTHILLS AND VALLEYS OF PIERCE
AND SOUTHERN KING COUNTIES-FOOTHILLS AND VALLEYS OF
THURSTON AND LEWIS COUNTIES-FOOTHILLS OF THE WESTERN AND
SOUTHERN OLYMPIC PENINSULA-LAKE CRESCENT AREA INCLUDING
US 101-LOWLANDS OF LEWIS AND SOUTHERN THURSTON COUNTIES-
LOWLANDS OF PIERCE AND SOUTHERN KING COUNTIES-MIDDLE
CHEHALIS RIVER VALLEY-NORTHERN HOOD CANAL-NORTHERN
WASHINGTON COAST-OLYMPIA AND SOUTHERN PUGET SOUND-
SOUTHERN HOOD CANAL-WILLAPA AND BLACK HILLS.
PZ...SMALL CRAFT ADVISORY FROM 10 PM THIS EVENING TO 5 AM PDT
SUNDAY FOR NORTHERN INLAND WATERS INCLUDING THE SAN JUAN
ISLANDS.
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