935
FXUS66 KSEW 150354
AFDSEW
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SEATTLE WA
854 PM PDT MON SEP 14 2026
SYNOPSIS
AN UPPER LEVEL TROUGH WILL MAINTAIN COOLER TEMPERATURES, CLOUDY
SKIES, AND CHANCES FOR SPRINKLES THROUGH TUESDAY. A RIDGE
BUILDS OVER THE REGION MID-WEEK, BRINGING A DRYING AND WARMING
TREND. NEAR NORMAL TEMPERATURES AND PARTLY CLOUDY CONDITIONS ARE
EXPECTED TO RETURN THROUGH THE WEEKEND WITH CONTINUED LOW LEVEL
ONSHORE FLOW.
SHORT TERM /TONIGHT THROUGH WEDNESDAY NIGHT/
NORTHWEST FLOW ALOFT THIS AFTERNOON WILL CONTINUE TO PROMOTE
ONSHORE FLOW, CLOUDY SKIES, AND COOLER TEMPERATURES THROUGHOUT
THE DAY. HIGH TEMPERATURES WILL PEAK SEVERAL DEGREES BELOW
NORMAL ACROSS THE LOWLANDS, IN THE MID TO UPPER 60S FOR MOST
AREAS. AN UPPER LEVEL TROUGH WILL PASS OVER THE PACIFIC
NORTHWEST THROUGH THE DAY ON TUESDAY, BRINGING CHANCES FOR LIGHT
RAIN MAINLY OVER THE CASCADES AND LOWLANDS EAST OF THE PUGET
SOUND IN THE MORNING WITH SHOWERS TAPERING OFF OVER THE
MOUNTAINS IN THE AFTERNOON. AS THE WEATHER SYSTEM PROGRESSES TO
THE SOUTH TUESDAY AFTERNOON, SKIES WILL SLOWLY BREAK UP WITH
PLENTY OF SUN BREAKS BY THE LATE AFTERNOON.
HIGH PRESSURE WILL CONTINUE TO BUILD OVER THE REGION LATE
TUESDAY, WITH MOSTLY CLEAR SKIES AND RESIDUAL MOISTURE ALLOWING
FOR PATCHY FOG TO DEVELOP EARLY WEDNESDAY MORNING. THE FOG AND
LOW STRATUS WILL BURN OFF BY THE LATE MORNING, REVEALING CLEAR
SKIES AND CALM CONDITIONS. TEMPERATURES WEDNESDAY WILL PEAK
RIGHT AROUND NORMAL FOR EARLY FALL, WITH HIGHS MOSTLY IN THE LOW
TO MID 70S.
LONG TERM /THURSDAY THROUGH MONDAY/
WARMING WILL CONTINUE INTO THURSDAY AS A THERMAL TROUGH DEVELOPS
ALONG THE COAST AND FLOW BRIEFLY TURNS WEAKLY OFFSHORE EARLY
THURSDAY MORNING. THE THERMAL TROUGH WILL SHIFT INLAND DURING
THE DAY THURSDAY, BRINGING HIGH TEMPERATURES INTO THE MID TO
UPPER 70S, WITH SOME SPOTS SOUTH OF THE OLYMPICS AND ALONG THE
CASCADE VALLEYS HITTING 80 DEGREES. ONSHORE FLOW WILL RETURN BY
FRIDAY AND CONTINUE TO VARYING DEGREES THROUGH THE WEEKEND,
WITH TEMPERATURES RETURNING TO NEAR-NORMAL AND PERIODIC MARINE
LOW STRATUS THAT IS EXPECTED TO REMAIN WEST OF THE PUGET SOUND
EACH MORNING.
15
AVIATION
A BROAD UPPER TROUGH REMAINS OVER THE PACIFIC NORTHWEST THROUGH
TUESDAY. LIGHT ONSHORE FLOW AND SCATTERED TO BROKEN MID LEVEL
CLOUDS ARE MAINTAINING VFR CEILINGS THIS EVENING, BUT A FEW
PATCHES OF LOW CLOUDS OR FOG MAY DEVELOP TONIGHT IN THE SOUTH
SOUND. OTHERWISE, AS THE TROUGH PASSES THROUGH EARLY TOMORROW,
EXPECT BRIEF MVFR CEILINGS AND A FEW LIGHT RAIN SHOWERS ACROSS
THE INTERIOR. DRY, NORTHERLY FLOW WILL FOLLOW TUESDAY AFTERNOON
AND EVENING WITH A RETURN TO VFR CONDITIONS.
KSEA...VFR THIS EVENING WITH LIGHT NORTH SURFACE WINDS TONIGHT.
WITH LATEST GUIDANCE SUGGESTING ELEVATED CHANCES FOR MVFR
CEILINGS FOR A FEW HOURS 14-17Z WITH A PASSING WEATHER
SYSTEM AND PERHAPS EVEN A LIGHT RAIN SHOWER OR TWO. CONDITIONS
DRY OUT WITH LIFTING AND SCATTERING CLOUDS LATE TUESDAY
AFTERNOON AND EVENING.
MARINE
WEAK ONSHORE FLOW TONIGHT WITH THE FLOW TURNING MORE NORTHERLY
ON TUESDAY. OFFSHORE FLOW WILL DEVELOP WEDNESDAY AND THURSDAY AS
A THERMAL TROUGH FORMS ALONG THE COAST. ONSHORE FLOW RETURNS
FRIDAY AND INTO THE WEEKEND.
33
FIRE WEATHER
MINIMAL FIRE WEATHER CONCERNS THROUGH NEXT WEEK. A WEAK WEATHER
SYSTEM WILL MOVE THROUGH THE AREA ON TUESDAY, BRINGING THE CHANCE
FOR LIGHT PRECIPITATION. A DRIER AND WARMER PATTERN WEDNESDAY INTO
THURSDAY. SURFACE WINDS WILL BRIEFLY TRANSITION OFFSHORE LATE
TUESDAY INTO WEDNESDAY MORNING, DECREASING MINIMUM RH VALUES
TOWARD THE MID 20S TO LOW 30S, ESPECIALLY IN THE NORTH CASCADES.
MINIMUM RELATIVE HUMIDITY VALUES REBOUND ON FRIDAY AS ONSHORE
FLOW RETURNS AND CONTINUES INTO NEXT WEEK.
29
SEW WATCHES/WARNINGS/ADVISORIES
WA...NONE.
PZ...NONE.
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