238
FXUS66 KSEW 152202
AFDSEW
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SEATTLE WA
302 PM PDT SAT AUG 15 2026
SYNOPSIS
WESTERN WASHINGTON WILL REMAIN POSITIONED BETWEEN AN UPPER LEVEL
LOW OVER THE NORTHEASTERN PACIFIC AND UPPER LEVEL RIDGING TO
THE SOUTHEAST THROUGH THE WEEKEND. ISOLATED THUNDERSTORMS WILL
BE POSSIBLE ACROSS THE MOUNTAINS THIS AFTERNOON AND EVENING,
WITH THE THUNDERSTORM THREAT DIMINISHING ON SUNDAY. ANOTHER
TROUGH WILL MOVE ACROSS THE REGION EARLY NEXT WEEK. A WARMER AND
DRIER TREND IS THEN EXPECTED MID TO LATE WEEK AS A RIDGE STARTS
TO BUILD INTO THE REGION, HOWEVER SHOWER CHANCES MAY INCREASE
AGAIN BY FRIDAY AS A DISTURBANCE APPROACHES FROM THE WEST.
SHORT TERM /TONIGHT THROUGH MONDAY NIGHT/
WESTERN WASHINGTON WILL REMAIN POSITIONED BETWEEN A WEAK UPPER
LEVEL LOW OVER THE NORTHEASTERN PACIFIC AND UPPER LEVEL RIDGING
BUILDING IN FROM THE SOUTHEAST THROUGH THE WEEKEND. THE LOW
WILL ALLOW FOR A WEAK SHORTWAVE TO MOVE ACROSS THE AREA TODAY,
WITH THE MAIN HIGHLIGHT REMAINING THE SHOWER AND ISOLATED
THUNDERSTORM THREAT FOR THE MOUNTAINS THIS AFTERNOON AND
EVENING.
LATEST SATELLITE IMAGERY THIS AFTERNOON SHOWS STRATUS PERSISTING
ALONG THE PACIFIC COAST AND SOUTHWEST INTERIOR, WHILE GRADUALLY
SCATTERING OUT ACROSS THE INTERIOR LOWLANDS. MEANWHILE, MID-
LEVEL CLOUDS ASSOCIATED WITH SHOWER ACTIVITY CONTINUE TO WORK
THEIR WAY UP ALONG THE SOUTH-CENTRAL CASCADES. ISOLATED THUNDERSTORMS
WILL REMAIN POSSIBLE FOR THE MOUNTAINS THIS AFTERNOON AND EVENING
AS CONDITIONS GRADUALLY BECOME MORE UNSTABLE THIS AFTERNOON.
ELEVATED FIRE WEATHER CONDITIONS WILL CONTINUE FOR THE CASCADES
AS A RESULT DUE TO LIGHTNING AND GUSTY OUTFLOW WINDS IN ANY
STORMS THAT DO FIRE UP. HIGHS TODAY WILL BE IN THE 70S TO LOW
80S ACROSS THE INTERIOR LOWLANDS AND IN THE MID 60S ALONG THE
COAST.
RIDGING WILL BUILD INTO THE REGION FROM THE SOUTHEAST ON
SUNDAY, ALLOWING FOR OVERALL THUNDERSTORM CHANCES TO DIMINISH
ACROSS THE AREA WITH ONLY A SLIGHT CHANCE (15-20%) EXPECTED
ACROSS THE NORTH CASCADES DURING THE AFTERNOON AND EVENING
HOURS. OTHERWISE, EXPECT ANOTHER ROUND OF MARINE STRATUS TO MAKE
ITS WAY INLAND DURING THE MORNING AND TO SCATTER OUT BY THE
AFTERNOON. HIGHS ON SUNDAY WILL BE IN THE UPPER 70S TO LOW 80S
ACROSS THE INTERIOR LOWLANDS AND IN THE MID TO UPPER 60S ALONG
THE COAST. MONDAY WILL BE SIMILAR AS THE THE LOW OFFSHORE
WEAKENS AND SINKS SOUTHWESTWARD. ANOTHER ROUND OF MORNING
STRATUS ACROSS THE AREA WILL SCATTER FOR SOME AFTERNOON SUN,
WITH HIGHS EXPECTED TO BE SIMILAR TO SUNDAY - IN THE UPPER 70S
TO LOW 80S ACROSS THE INTERIOR AND IN THE MID 60S TO LOW 70S
ALONG THE COAST.
LONG TERM /TUESDAY THROUGH SATURDAY/
ENSEMBLE GUIDANCE HAS BECOME
SOMEWHAT MORE CONSOLIDATED WITH RESPECT TO THE PATTERN FOR THE
MIDDLE TO LATE PORTIONS OF NEXT WEEK, WITH A LEAN TOWARD HIGH
PRESSURE BUILDING ACROSS THE GREAT BASIN AND EXTENDING INTO THE
PACIFIC NORTHWEST. THIS WOULD BRING TEMPERATURES TO NEAR TO
SLIGHTLY ABOVE SEASONAL NORMALS INTO THE LATE STAGES OF NEXT
WEEK. WHILE THE PATTERN OF ONSHORE LOW-LEVEL FLOW MAINTAINING
MORNING CLOUDS AND CLEARING IN THE INTERIOR BY EARLY AFTERNOON
EACH DAY WILL PREVENT RELATIVE HUMIDITY VALUES FROM TRENDING TOO
LOW, THERE IS STILL NOT A SIGNIFICANT SIGNAL FOR RAINFALL FOR
THE MIDWEEK PERIOD. THIS MAY BEGIN TO SHIFT TOWARD FRIDAY AS
ENSEMBLE GUIDANCE SUGGESTS THE NEXT DISTURBANCE MAY GET CLOSE
ENOUGH TO BRING ANOTHER ROUND OF SHOWER CHANCES. THAT SAID,
THERE'S STILL AROUND 40% OF ENSEMBLE MEMBERS THAT WOULD FAVOR
MORE OF A RIDGE PATTERN OVER THE WEST COAST THAT COULD CONTINUE
TO BLOCK THE REGION FROM ANY SIGNIFICANT WEATHER SYSTEMS.
AVIATION
THE MARINE STRATUS CONTINUES TO ERODE ACROSS THE INTERIOR THIS
AFTERNOON, GIVING WAY TO VFR CIGS. MVFR STRATUS CONFINED TO THE
COAST THIS AFTERNOON. THERE MAY BE SOME BRIEF IMPROVEMENT ALONG THE
COAST THIS EVENING, BUT CONDITIONS ARE EXPECTED TO DETERIORATE
QUICKLY BACK TO MVFR. ANOTHER ROUND OF STRATUS SUNDAY MORNING WILL
BRING A 30-40% CHANCE OF MVFR CIGS AND A 20-30% CHANCE OF IFR CIGS
TO THE INTERIOR TERMINALS. IMPROVEMENT TO VFR SUNDAY AFTERNOON AFTER
17-18Z. WINDS PREDOMINANTLY SW THIS AFTERNOON ACROSS THE INTERIOR
TERMINALS AND WSW ALONG THE COAST. WINDS WILL TRY TO SWITCH WNW
ACROSS CENTRAL PUGET SOUND TERMINALS THIS EVENING AFTER 00Z. LIGHT
SW TO CALM WINDS TONIGHT.
KSEA...VFR CONDITIONS THIS AFTERNOON. MVFR CIGS POSSIBLE (30-40%
CHANCE) AGAIN SUNDAY MORNING, WITH A 20% CHANCE OF IFR CIGS AFTER
12Z SUNDAY. CONDITIONS SHOULD IMPROVE IN THE AFTERNOON TO VFR. SW
WINDS THIS AFTERNOON 5-7 KT WINDS WILL SHIFT MORE W/NW BETWEEN 02-
06Z AROUND 4-5 KT. LIGHT SW WINDS OVERNIGHT INTO SUNDAY MORNING.
GUIDANCE SUGGESTS WNW RETURN SUNDAY AFTERNOON.
29
MARINE
BROAD HIGH PRESSURE OVER THE PACIFIC WILL MAINTAIN LIGHT WINDS OVER
THE COASTAL WATERS. HIGH PRESSURE WILL THEN EXPAND INTO AREA WATERS
ON SUNDAY AND STRENGTHEN INTO NEXT WEEK. THIS WILL LEAD TO INCREASED
NW WINDS OVER THE COASTAL WATERS INTO NEXT WEEK, BUT ARE EXPECTED TO
REMAIN BELOW SCA THRESHOLDS. SEAS WILL BE AROUND 3-6 FT THROUGH
MONDAY. SEAS WILL BUILD SLIGHTLY ON TUESDAY AND BECOME STEEP AROUND
6-8 FT WITH A DOMINANT PERIOD OF 7 SECONDS OVER THE OUTER COASTAL
WATERS. STEEP SEAS LOOK TO CONTINUE THROUGH THURSDAY.
DIURNALLY DRIVEN WESTERLY WINDS WILL CONTINUE TO OCCUR EACH
AFTERNOON AND EVENING THROUGH THE STRAIT OF JUAN DE FUCA THIS
WEEKEND WITH GUSTS LIKELY (70%+ CHANCE REACHING SCA THRESHOLDS. THE
WESTERLY PUSHES LOOK TO START TO WEAKEN STARTING ON MONDAY INTO LATE
IN THE WEEK WITH A 30% OR LOWER CHANCE OF WINDS REACHING SCA
THRESHOLDS.
29
FIRE WEATHER
ELEVATED FIRE WEATHER CONDITIONS WILL CONTINUE ACROSS THE
CASCADES TODAY WITH SLIGHT CHANCES (15-20%) OF THUNDERSTORMS
POSSIBLE ALONG THE CASCADE CREST THIS AFTERNOON AND EVENING.
OVERALL CHANCES FOR CONVECTION WILL DIMINISH INTO SUNDAY AS
UPPER LEVEL RIDGING BUILDS INTO THE AREA FROM THE SOUTHEAST. BY
SUNDAY, EXPECT CONVECTION TO LARGELY BE CONFINED ALONG THE FAR
NORTHERN CASCADE CREST AND AREAS GENERALLY EAST OF THE CREST.
CONTINUED ONSHORE FLOW AND EXCELLENT OVERNIGHT HUMIDITY RECOVERIES
WILL THEN HELP MITIGATE FIRE WEATHER CONDITIONS THROUGH EARLY
NEXT WEEK. WHILE SOME UNCERTAINTY REMAINS IN THE LONG TERM
PATTERN, ENSEMBLE GUIDANCE HAS INCREASINGLY COME TO CONSENSUS
THAT A WARMING AND DRYING TREND IS LIKELY MID TO LATE WEEK,
BEFORE THE POTENTIAL FOR SHOWER AND THUNDERSTORM CHANCES INCREASES
AGAIN LATE WEEK AS THE NEXT DISTURBANCE APPROACHES FROM THE WEST.
THIS COULD POTENTIALLY REINTRODUCE SOME ELEVATED FIRE WEATHER
CONCERNS TO THE AREA.
SEW WATCHES/WARNINGS/ADVISORIES
WA...NONE.
PZ...SMALL CRAFT ADVISORY UNTIL 5 AM PDT SUNDAY FOR CENTRAL U.S.
WATERS STRAIT OF JUAN DE FUCA-EAST ENTRANCE U.S. WATERS
STRAIT OF JUAN DE FUCA.
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