003
FXUS66 KSEW 160335
AFDSEW
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SEATTLE WA
835 PM PDT TUE SEP 15 2026
SYNOPSIS
CLOUDY SKIES WILL CONTINUE TO SCATTER TODAY AS HIGH PRESSURE
PROMOTES A WARMING AND DRYING TREND THROUGH THURSDAY. NEAR
NORMAL TEMPERATURES AND PARTLY CLOUDY CONDITIONS ARE EXPECTED
TO RETURN THROUGH THE WEEKEND AND INTO EARLY NEXT WEEK WITH
CONTINUED LOW LEVEL ONSHORE FLOW.
SHORT TERM /TONIGHT THROUGH THURSDAY NIGHT/
CLOUDS HAVE SLOWLY SCATTERED THIS EVENING LEAVING MOST AREAS
PARTLY CLOUDY. CLOUD COVER WILL CONTINUE TO DECREASE THIS
EVENING, BUT WITH WINDS DECREASING, THAT WILL OPEN THE DOOR FOR
SOME LOCALIZED PATCHY FOG IN SHELTERED AREAS AND RIVER VALLEYS.
LOWS TONIGHT REMAIN ON TRACK FOR THE MID 40S TO LOW 50S. 62
A HIGH PRESSURE RIDGE WILL SLOWLY BUILD INTO THE REGION TONIGHT
THROUGH THURSDAY, BRINGING A WARMING AND DRYING TREND TO
WESTERN WASHINGTON. TEMPERATURES WILL WARM UP TO NEAR-NORMAL
WEDNESDAY UNDER MOSTLY CLEAR SKIES, WITH HIGHS GENERALLY IN THE
MID 70S. A THERMAL TROUGH BUILDING ALONG THE COAST WILL SHIFT
INLAND ON THURSDAY, INDUCING COOLING ALONG THE COAST WITH EVEN
WARMER TEMPERATURES FURTHER INLAND. TEMPERATURES THURSDAY WILL
BE THE WARMEST OF THE WEEK, WITH HIGHS IN THE MID TO UPPER 70S
AND AROUND 80 DEGREES FOR SOME AREAS ALONG THE CASCADE FOOTHILLS
AND VALLEYS AND OVER THE SOUTHERN INTERIOR.
15
LONG TERM /FRIDAY THROUGH TUESDAY/
HIGH PRESSURE OFFSHORE WILL CONTINUE TO INFLUENCE THE WEATHER
PATTERN OVER THE WEEKEND AND INTO EARLY NEXT WEEK, MAINTAINING
SEASONABLE TEMPERATURES AND DRY CONDITIONS. ONSHORE FLOW WILL
CONTINUE TO PROMOTE MORNING CLOUD COVER WITH PLENTY OF SUN
BREAKS IN THE AFTERNOONS. FORECAST MODELS CONTINUE TO HINT AT A
POTENTIAL PATTERN CHANGE EARLY NEXT WEEK, THOUGH DETERMINISTIC
MODELS CONTINUE TO PUSH BACK THE TIMING OF AN APPROACHING
TROUGH AS THE PACIFIC RIDGE HOLDS ON.
15
AVIATION
NORTH TO NORTHEAST FLOW ALOFT TONIGHT AS A LOW DIGS SOUTHWARD
AND WEAK RIDGING NOSES OVER THE AREA. VFR CONDITIONS THIS
EVENING WITH CLEARING SKIES. WINDS WILL CONTINUE TO EASE,
BECOMING LIGHT TO CALM THROUGH EARLY WEDNESDAY MORNING. CLEARING
SKIES, LIGHT SURFACE WINDS, AND SUBSIDENCE ALOFT WILL ALLOW FOR
AREAS OF VALLEY FOG TO DEVELOP, WITH THE GREATEST CHANCES BEING
AT THE USUAL FOG PRONE LOCATIONS. (OLM, PWT, PAE, HQM) CLEAR
SKIES WILL TAKEOVER THE IFR/LIFR CONDITIONS LATE WEDNESDAY
MORNING. WINDS WEDNESDAY WILL PICK UP OUT THE NORTH 5 TO 10 KT.
KSEA...VFR THROUGH THE EVENING/EARLY TONIGHT WITH NORTH WINDS 5 TO
10 KT DECREASING TO 5 KT OVERNIGHT. THERE REMAINS A 15-25%
CHANCE OF IFR CONDITIONS IN THE MORNING. MODEL GUIDANCE HAS
10-15% LIFR PROBABILITIES OF VICINITY FOG TO THE NORTH AND SOUTH
OF THE TERMINAL. TIME PERIOD FOR FORMATION IS FROM 13-17Z, WITH
CLEAR SKIES WEDNESDAY AFTERNOON. WINDS INCREASE OUT OF THE
NORTH WEDNESDAY 5-10 KT.
HPR/62
MARINE
A THERMAL TROUGH WILL BUILD LOW PRESSURE ALONG THE COAST
WEDNESDAY INTO THURSDAY. THIS WILL CAUSE THE WINDS TO BRIEFLY
TURN OFFSHORE. ONCE THE THERMAL TROUGH MOVES INLAND ON FRIDAY,
THE ONSHORE FLOW WILL RETURN WITH WEAK SYSTEMS PASSING TO THE
NORTH THIS WEEKEND. THE LIKELIHOOD OF WINDS REACHING HEADLINE
THRESHOLDS DURING THE NEXT SEVEN DAYS IS LOW, BUT PORTIONS OF
THE COASTAL WATERS AND THE STRAIT OF JUAN DE FUCA MAY SEE GUSTS
APPROACHING 20-25 KT AS THE WEAK SYSTEM LOOKS TO MOVE THROUGH
EARLY NEXT WEEK. SEAS WILL HOLD AROUND 3-6 FT THROUGH THE
FORECAST PERIOD.
HPR/62
FIRE WEATHER
A BRIEF WARMING AND DRYING TREND WILL KICK OFF TODAY AND
CONTINUE INTO THURSDAY AS HIGH PRESSURE BUILDS OFFSHORE. SURFACE
WINDS WILL BRIEFLY TURN OFFSHORE ON WEDNESDAY AS A THERMAL
TROUGH BUILDS ALONG THE PACIFIC COAST. WEAK OFFSHORE FLOW WILL
CONTINUE THROUGH THURSDAY, CAUSING ADDITIONAL DRYING WITH
RELATIVE HUMIDITY VALUES BOTTOMING OUT IN THE MID 20S TO LOW
30S IN THE NORTH CASCADES AND LOWLANDS SOUTH OF THE PUGET
SOUND. THE THERMAL TROUGH WILL SHIFT INLAND ON THURSDAY AHEAD OF
THE RETURN OF ONSHORE FLOW, WHICH WILL MINIMIZE FIRE WEATHER
CONCERNS THROUGH THE WEEKEND AND INTO EARLY NEXT WEEK.
15
SEW WATCHES/WARNINGS/ADVISORIES
WA...NONE.
PZ...NONE.
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