426
FXUS66 KSEW 182056
AFDSEW
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SEATTLE WA
156 PM PDT FRI SEP 18 2026
SYNOPSIS
SEASONABLE CONDITIONS WITH MORNING CLOUDS WILL SETTLE INTO THE
REGION INTO NEXT AS ONSHORE FLOW CONTINUES, WITH LITTLE CHANGE
DAY TO DAY.
SHORT TERM /TONIGHT THROUGH SUNDAY NIGHT/
AN UPPER LEVEL RIDGE WILL CONTINUE TO PROGRESS EASTWARD TODAY,
WITH SOUTHWEST FLOW ALOFT AND ONSHORE FLOW AT THE SURFACE. THIS
PATTERN WILL CONTINUE THROUGH THE WEEKEND AS A SERIES OF
WEATHER SYSTEMS PASS TO THE NORTH, WITH LITTLE CHANGE DAY TO DAY
ACROSS WESTERN WASHINGTON. SEASONABLE TEMPERATURES WILL SETTLE
INTO THE REGION, WITH HIGHS GENERALLY IN THE UPPER 60S TO LOWER
70S AND LOWS IN THE UPPER 40S TO LOWER 50S. ONSHORE PUSHES WILL
ALSO BRING MARINE STRATUS INLAND EACH MORNING TO VARYING
DEGREES, WITH SUNSHINE RETURNING TO MOST INLAND AREAS EACH
AFTERNOON.
LONG TERM /MONDAY THROUGH FRIDAY/
THIS FALL-LIKE PATTERN IS FAVORED TO CONTINUE INTO EARLY NEXT
WEEK AS MODELS HAVE BACKED OFF ON INCOMING PRECIPITATION. THERE
WILL LIKELY BE LITTLE CHANGE ONCE AGAIN DAY TO DAY THROUGH AT
LEAST TUESDAY. MODELS HAVE CONTINUED TO TREND DRIER INTO THE
MIDDLE OF NEXT WEEK, AND CONDITIONS MAY REMAIN STEADY THROUGH
NEXT FRIDAY. HOWEVER, FORECAST CONFIDENCE TOWARDS THE END OF THE
PERIOD REMAINS LOW.
15
AVIATION
NORTHERLY FLOW ALOFT THIS AFTERNOON WILL TURN MORE WESTERLY TONIGHT
AS AN UPPER-RIDGE SHIFT TOWARDS THE AREA. MARINE STRATUS IS
SCATTERING AND CLEARING TO VFR ACROSS THE INTERIOR THIS AFTERNOON.
LOW CLOUDS ARE LIKELY TO REMAIN ALONG THE COAST WITH MVFR CIGS FOR
TERMINALS SUCH AS KHQM. TONIGHT, MARINE STRATUS (IFR/MVFR AND
ISOLATED LIFR) WILL TRACK INLAND ONCE MORE - ARRIVING IN THE
INTERIOR BETWEEN 08-12Z SATURDAY. A CLOUDY MORNING WILL GIVE WAY TO
VFR CONDITIONS AROUND 19-20Z.
KSEA...VFR AT THE TERMINAL AND REMAINING THROUGH THE EVENING.
STRATUS WILL RETURN AGAIN OVERNIGHT INTO EARLY SATURDAY MORNING
AROUND 10-12Z. SURFACE WINDS SOUTH TO SOUTHWESTERLY 4 TO 8 KNOTS
THROUGHOUT THE PERIOD.
41
MARINE
ONSHORE FLOW WILL PERSIST INTO NEXT WEEK AS A SERIES OF SYSTEMS PASS
WELL NORTH OF THE AREA. THE ONSHORE FLOW WILL INCREASE SOMEWHAT
EARLY NEXT WEEK AS WEAK FRONTAL SYSTEMS BEGIN TO CLIP THE COASTAL
WATERS. NBM PROBABILITIES FOR SCA GUSTS ARE INCREASING TO 30-60%
THROUGHOUT THE CENTRAL/EASTERN STRAIT OF JUAN DE FUCA SUNDAY NIGHT
INTO MONDAY MORNING AND 60-80% ON MONDAY EVENING.
FIRE WEATHER
ONSHORE FLOW WILL BRING COOLER TEMPERATURES, CLOUD COVER, AND
INCREASED MOISTURE TO THE AREA TODAY THROUGH THE WEEKEND, HELPING
TO MINIMIZE FIRE WEATHER CONCERNS. FIRE WEATHER CONCERNS WILL
REMAIN MINIMAL THROUGH THE NEXT WEEK WITH COOLER TEMPERATURES
AND CHANCES OF PRECIPITATION INCREASING MID TO LATE WEEK.
SEW WATCHES/WARNINGS/ADVISORIES
WA...NONE.
PZ...NONE.
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