276
FXUS66 KSEW 121011
AFDSEW
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SEATTLE WA
311 AM PDT MON OCT 12 2026
SYNOPSIS
DRY NORTHERLY FLOW ALOFT TODAY WITH UPPER LEVEL LOW OVER
SOUTHEAST OREGON AND UPPER LEVEL RIDGE OVER SOUTHERN BRITISH
COLUMBIA. RIDGE MOVING OVER WESTERN WASHINGTON TONIGHT WILL
WEAKEN TUESDAY AS AN ATMOSPHERIC RIVER MOVES INTO SOUTHERN
BRITISH COLUMBIA. THE RIDGE WILL REBUILD OVER THE AREA
WEDNESDAY AND THURSDAY THEN SHIFT EAST FRIDAY. LOW LEVEL
OFFSHORE FLOW THURSDAY AND FRIDAY FOR A COUPLE OF WARM DAYS.
WEAKENING SYSTEM MOVING INTO WESTERN WASHINGTON FRIDAY NIGHT
AND SATURDAY WITH ANOTHER SYSTEM POSSIBLE SUNDAY NIGHT.
SHORT TERM /TODAY THROUGH WEDNESDAY/
SATELLITE IMAGERY SHOWS CLEAR SKIES OVER WESTERN WASHINGTON
THIS MORNING WITH FOG IN THE SNOHOMISH AND LOWER CHEHALIS RIVER
VALLEYS. IT'S A BRISK FALL MORNING WITH TEMPERATURES AT 3
AM/10Z RANGING FROM NEAR FREEZING AT SHELTON AND OLYMPIA TO THE
MID 40S IN THE SEATTLE METRO AREA. SEATTLE TACOMA AIRPORT AT 44
DEGREES. THE LAST TIME SEATTLE HAD A LOW IN THE 30S WAS APRIL
16TH ( 36 DEGREES ).
SUNNY TODAY WITH DRY NORTHERLY FLOW ALOFT OVER THE AREA. MORNING
VALLEY FOG WILL NOT LAST MORE THAN A COUPLE OF HOURS AFTER
SUNRISE. FROST ADVISORY FOR MOST LOCATIONS SOUTH OF SEATTLE AND
ALONG THE NORTH COAST WILL EXPIRE AT 8 AM/15Z. HIGHS NEAR
NORMAL, IN THE UPPER 50S TO MID 60S.
UPPER LEVEL RIDGE OVER BRITISH COLUMBIA TODAY MOVING SOUTH OVER
WESTERN WASHINGTON TONIGHT. ATMOSPHERIC RIVER APPROACHING
BRITISH COLUMBIA SPREADING HIGH CLOUDS OVER THE AREA. THIS WILL
KEEP LOW TEMPERATURES A LITTLE WARMER TUESDAY MORNING, IN THE
MID 30S TO MID 40S.
HIGH CLOUDS CONTINUING INTO TUESDAY WITH THE ATMOSPHERIC RIVER
MOVING INTO THE CENTRAL BRITISH COLUMBIA COAST. UPPER LEVEL
RIDGE OVER THE AREA WEAKENING TUESDAY NIGHT WITH THE
ATMOSPHERIC RIVER SAGGING SLIGHTLY SOUTH PUTTING THE NORTH
COAST AND THE NORTHWEST INTERIOR ON THE VERY SOUTHERN EDGE OF
THE RIVER. LIKELY POPS ALONG THE NORTH COAST WITH CHANCE POPS
OVER THE NORTHWEST INTERIOR. HIGHS TUESDAY IN THE MID 50S TO MID
60S WITH THE COLDER HIGHS TO THE NORTH WITH THE THICKER CLOUD
COVER. LOWS TUESDAY NIGHT IN THE 40S.
UPPER LEVEL RIDGE REBUILDING OVER WESTERN WASHINGTON WEDNESDAY
WITH THE 500 MB HEIGHTS NEAR 580 DMS BY 00Z THURSDAY. CHANCE OF
RAIN COAST AND NORTH OF SEATTLE IN THE MORNING. ATMOSPHERIC
RIVER DISSIPATING BY AFTERNOON MAKING FOR A MOSTLY CLOUDY TO
CLOUDY DAY. HIGHS IN THE LOWER TO MID 60S. FELTON
LONG TERM /WEDNESDAY NIGHT THROUGH SUNDAY/
MODELS IN GOOD AGREEMENT WITH THE UPPER LEVEL RIDGE CONTINUING
TO BUILD OVER THE AREA WEDNESDAY NIGHT AND THURSDAY. 500 MB
HEIGHTS IN THE MID 580S DMS BY THURSDAY AFTERNOON. LOW LEVEL
FLOW TURNING OFFSHORE THURSDAY WARMING HIGHS INTO THE MID 60S TO
LOWER 70S.
UPPER LEVEL RIDGE SHIFTS EAST THURSDAY NIGHT INTO FRIDAY BUT LOW
LEVEL OFFSHORE FLOW CONTINUING AT LEAST THROUGH FRIDAY MORNING.
FRIDAY LOOKS TO BE THE WARMEST DAY OF THE WEEK WITH HIGHS IN THE
MID 60S TO MID 70S. EVEN WITH HIGHS OVER 10 DEGREES ABOVE NORMAL
FRIDAY ( SEATTLE NORMAL HIGH 60 DEGREES ) NOT EXPECTING ANY
RECORDS AS OCTOBER 16TH BACK IN 2022 WAS ONE OF THE HOTTEST
OCTOBER DAYS ON RECORD ( THE HIGH IN SEATTLE WAS 88 DEGREES ).
UPPER LEVEL RIDGE WELL TO THE EAST FRIDAY NIGHT AND SATURDAY
WITH A DISSIPATING SYSTEM MOVING INTO THE AREA. BEST CHANCES FOR
RAIN NORTH COAST AND NORTH CASCADES. A STRONGER MORE ORGANIZED
SYSTEM WILL APPROACH THE COAST SUNDAY. HIGHS COOLING TO THE
LOWER TO MID 60S SATURDAY AND MID 50S TO LOWER 60S SUNDAY. LOWS
IN THE 40S FOR THE MOST PART THROUGH THE PERIOD WITH LOWER 50S
POSSIBLE IN THE SEATTLE METRO AREA. FELTON
AVIATION
NORTHERLY FLOW ALOFT CONTINUES OVER WESTERN WASHINGTON TODAY WITH AN
UPPER RIDGE OFFSHORE AND AN UPPER LOW GRADUALLY SHIFTING EASTWARD
INTO THE GREAT BASIN. APART FROM SOME PATCHY LIFR FOG IN THE SOME OF
THE RIVER VALLEYS THIS MORNING, VFR CONDITIONS WILL PREVAIL ACROSS
THE REGION TODAY.
KSEA...VFR. SURFACE WINDS LIGHT AND VARIABLE BECOMING W/NW UNDER 7
KNOTS THIS AFTERNOON.
27
MARINE
WEAK PRESSURE GRADIENTS WILL PRODUCE LITTLE IN THE WAY OF WIND
ACROSS AREA WATERS TODAY. A WEAK SURFACE RIDGE WILL SHIFT INLAND ON
TUESDAY AS A FRONTAL SYSTEM APPROACHES THE OFFSHORE WATERS WITH
WINDS SHIFTING TO THE E/SE ACROSS MUCH OF THE WATERS. A WEAK COLD
FRONT WILL REACH THE AREA ON WEDNESDAY WITH POSSIBLE HEADLINES FOR
LOW END SMALL CRAFT ADVISORY WINDS ACROSS PORTIONS OF THE COASTAL
WATERS AND THE WEST ENTRANCE TO THE STRAIT. HIGH PRESSURE REBUILDS
ACROSS THE WATERS ON THURSDAY WITH THE FLOW TURNING NORTHERLY OR
WEAKLY OFFSHORE AS THERMALLY INDUCED LOW PRESSURE EXPANDS NORTHWARD
ACROSS WESTERN OREGON. ANOTHER FRONT IS EXPECTED TO REACH THE WATERS
FRIDAY NIGHT OR SATURDAY WITH POSSIBLE HEADLINES FOR WINDS AND/OR
STEEPENING SEAS ACROSS THE COASTAL WATERS.
27
SEW WATCHES/WARNINGS/ADVISORIES
WA...FROST ADVISORY UNTIL 8 AM PDT THIS MORNING 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...NONE.
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