412
FXUS66 KSEW 222301
AFDSEW
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SEATTLE WA
401 PM PDT WED JUL 22 2026
SYNOPSIS
HOT TEMPERATURES WILL CONTINUE THIS AFTERNOON WITH AN
UPPER LEVEL RIDGE OVER WESTERN WASHINGTON AND A THERMALLY INDUCED
TROUGH PUSHING INLAND. THE PATTERN WILL CHANGE TONIGHT AS MOISTURE
WORKS ITS WAY UP INTO THE AREA FROM THE SOUTH AND CHANCES FOR
SHOWERS AND ISOLATED THUNDERSTORMS INCREASE AND PERSIST INTO
THURSDAY. AN UPPER LEVEL TROUGH OFFSHORE WILL THEN PUSH INLAND OVER
THE WEEKEND, BRINGING COOLER TEMPERATURES TO THE AREA AND ADDITIONAL
CHANCES OF SHOWERS. TROUGHING WILL PERSIST THROUGH EARLY NEXT WEEK,
ALLOWING FOR TEMPERATURES TO TREND JUST BELOW TO NEAR NORMAL.
SHORT TERM /TONIGHT THROUGH FRIDAY NIGHT/
IT'S HOT OUT THERE- LATEST OBSERVATIONS SHOW TEMPERATURES TRENDING
IN THE MID 80S TO MID 90S ACROSS MUCH OF THE INTERIOR OF WESTERN
WASHINGTON THIS AFTERNOON. THE THERMAL TROUGH THAT WAS SITUATED
ALONG THE COAST HAS STARTED TO MAKE ITS WAY INLAND AS WINDS
HAVE ALREADY SWITCHED BACK TO ONSHORE THIS AFTERNOON. TEMPERATURES
ALONG THE PACIFIC COAST ARE CURRENTLY TRENDING IN THE MID 50S
TO MID 60S AS A RESULT AND SHOWER ACTIVITY AND CLOUD COVER HAVE
STARTED TO STREAM UP INTO THE AREA. CHANCES OF SHOWERS AND ISOLATED
THUNDERSTORM ACTIVITY WILL INCREASE THIS EVENING ALONG THE COAST,
AREAS SOUTH OF THE SOUND, AND THE SOUTHERN CASCADES AS MOISTURE
FROM A TROUGH OFFSHORE CONTINUES TO STREAM NORTHWARD INTO THE
AREA. WITH DRY CONDITIONS IN THE LOW LEVELS, ANY RAINFALL
ASSOCIATED WITH THE SHOWER ACTIVITY THAT INITIALLY MOVES INTO
THE AREA MAY HAVE A HARD TIME MAKING IT ALL THE WAY TO THE
GROUND. SHOWER AND ISOLATED THUNDERSTORM ACTIVITY WILL THEN
INCREASE IN COVERAGE AND EXPAND AREA WIDE TONIGHT INTO THE
OVERNIGHT PERIOD AS MOISTURE CONTINUES TO STREAM INTO THE REGION
AND WINDS TRANSITION TO SOUTHWESTERLY. CRITICAL FIRE WEATHER
CONDITIONS ARE EXPECTED TO DEVELOP ALONG THE COAST, SOUTH
INTERIOR, AND SOUTHERN CASCADES TONIGHT INTO THURSDAY AS
LIGHTNING FROM ISOLATED THUNDERSTORM ACTIVITY COULD CAUSE
ADDITIONAL IGNITIONS.
THURSDAY MORNING LOW TEMPERATURES WILL REMAIN MILD AND WILL
GENERALLY BE IN THE UPPER 50S TO MID 60S ACROSS THE AREA. SHOWER
AND THUNDERSTORM CHANCES WILL CONTINUE THROUGH THE DAY ON THURSDAY,
BUT WILL GRADUALLY BECOME MORE CONFINED TO THE CASCADES. THE
PATTERN CHANGE WILL ALLOW FOR AFTERNOON HIGH TEMPERATURES TO
COOL 10 TO 15 DEGREES IN COMPARISON TO TODAY, WITH HIGHS EXPECTED
TO TOP OUT IN THE UPPER 70S TO LOW 80S ACROSS THE AREA.
DRIER CONDITIONS AND A SLIGHT WARM UP ARE EXPECTED AGAIN BY
FRIDAY WITH AN UPPER LEVEL TROUGH REMAINING OFFSHORE. ONSHORE
FLOW WILL ALLOW FOR THE MARINE STRATUS TO PUSH INTO THE SOUND BY
EARLY FRIDAY MORNING AND WILL BRING COOLER MORNING LOWS TO THE
AREA- MOSTLY IN THE 50S TO LOW 60S. THE LAYER WILL RETREAT BACK
TO THE COAST BY THE AFTERNOON, ALLOWING FOR HIGHS ACROSS THE
INTERIOR TO WARM BACK INTO THE MID 80S. HIGHS ALONG THE COAST
WILL REMAIN COOLER UNDER THE MARINE STRATUS- AND ONLY LOOK TO
TOP OUT IN THE MID 60S TO LOW 70S.
LONG TERM /SATURDAY THROUGH WEDNESDAY/
GUIDANCE REMAINS IN GOOD AGREEMENT THAT THE UPPER LEVEL TROUGH
OFFSHORE WILL MOVE ACROSS THE AREA OVER THE WEEKEND, WHICH WILL
BRING COOLER TEMPERATURES AND ADDITIONAL CHANCES OF SHOWERS TO
WESTERN WASHINGTON. THE GREATEST CHANCES OF PRECIPITATION WILL
BE ALONG THE COAST AND NORTHERN INTERIOR AREAS ON SUNDAY AS A
SHORTWAVE FROM A TROUGH OFF THE COAST OF BRITISH COLUMBIA MOVES
INTO THE AREA. AFTERNOON HIGH TEMPERATURES WILL BE BELOW TO NEAR
NORMAL ACROSS THE AREA AS A RESULT AND ARE EXPECTED TO BE IN
THE UPPER 60S TO MID 70S ACROSS THE INTERIOR AND IN THE 60S ALONG
THE COAST. UPPER LEVEL TROUGHING THEN LOOKS TO REMAIN THE DOMINANT
INFLUENCE ACROSS THE REGION HEADING INTO EARLY NEXT WEEK. THIS
WILL HELP PROMOTE CONTINUED ONSHORE FLOW ACROSS THE AREA AND
HIGH TEMPERATURES IN THE 70S THROUGH WEDNESDAY.
AVIATION
HIGH PRESSURE WITH A RIDGE WILL MOVE TO THE NORTH AS A SHORTWAVE
TROUGH TO THE SOUTH WITH AN ASSOCIATED UPPER LOW WILL MOVE NORTH
TONIGHT INTO THURSDAY, WITH INCREASING FLOW FROM THE SOUTH ALOFT.
MAIN CONCERN THIS EVENING IS THUNDER WITH ACTIVITY FROM OREGON
MOVING INTO WESTERN WASHINGTON THIS EVENING. HIGHER CONFIDENCE WITH
THE TCF FORECAST HAS LED TO THE INCLUSION OF -TSRA FOR THE SOUTHERN
TERMINALS (UP TO AND INCLUDING SEATAC AND BOEING FIELD). COVERAGE IS
EXPECTED TO BE POPCORN IN NATURE WITH NOT A WHOLE LOT OF
PRECIPITATION OUTPUT (AND HIGH BASES TO START, WITH TOPS UP TO
35,000 FT) BUT MAIN CONCERNS WILL BE LIGHTNING, AND GUSTY OUTFLOW
WINDS. THE HIGHEST CHANCES FOR THUNDER FOR THE COAST/SOUTH INTERIOR
WILL BE FROM 00-04Z, AND FOR SOUTH PUGET SOUND FROM 04Z-06Z.
ACTIVITY WILL MOVE TO THE NORTHEAST OVERNIGHT, WITH THUNDER CHANCES
INTO THURSDAY REMAINING IN THE OLYMPICS/NORTHWEST COAST. CEILINGS
WILL ALSO LOWER TONIGHT/THURSDAY MORNING, WITH A 50-60% CHANCE OF
MVFR FOR MOST INTERIOR TERMINALS THURSDAY MORNING (12Z-21Z), WITH
HIGHER CHANCES OF IFR CEILINGS/VISIBILITIES ALONG THE COAST.
NORTHWEST WINDS 8-12 KT WILL SWITCH TO THE SOUTHWEST OVERNIGHT INTO
THURSDAY 5-10 KT.
KSEA...VFR SKIES THROUGH EARLY EVENING. THERE REMAINS A 20-30%
CHANCE OF THUNDER IN AND NEAR THE TERMINAL FROM 04-06Z THIS EVENING
FROM CONVECTION TO THE SOUTH (NOW INCLUDED IN THE TAF WITH THE TCF
FORECAST). AFTER THE THUNDER MOVES OUT, THERE IS A 50-60% CHANCE OF
MVFR CEILINGS DEVELOPING FROM 12Z TO AS LATE AS 21Z. WEST-NORTHWEST
WINDS AT 10 KT WILL SWITCH TO THE SOUTHWEST AS THE CONVECTION MOVES
THROUGH.
HPR
MARINE
THE THERMAL TROUGH WILL CONTINUE TO SHIFT INLAND, USHERING
STRONGER ONSHORE FLOW BACK INTO THE REGION. EXPECT WESTERLY WINDS TO
INCREASE TO 25 KT THROUGH THE CENTRAL AND EASTERN STRAIT OF JUAN DE
FUCA TONIGHT. GIVEN HIGHER CONFIDENCE IN INCREASING SOUTHERLY WINDS
AROUND BELLINGHAM BAY AND ALSO THROUGH THE SOUTHERN HALF OF PUGET
SOUND, HAVE ALSO ISSUED SMALL CRAFT ADVISORIES FOR THE TWO
ADDITIONAL ZONES FOR TONIGHT. WITH ONSHORE FLOW CONTAINING INTO THE
WEEKEND, EXPECT TO SEE ADDITIONAL SCA STRENGTH WINDS THROUGH THE
STRAIT LATER THIS WEEK. SEAS OVER THE COASTAL WATERS REMAIN
GENERALLY AROUND 5 TO 6 FT, BUT MAY BUILD FURTHER ON SATURDAY
(ESPECIALLY OVER THE SOUTHERN COASTAL ZONES) AS A RESULT OF STRONGER
SOUTHERLY WINDS WITH A PERSISTENT FETCH THROUGH THE INNER COASTAL
WATERS. CULLEN
FIRE WEATHER
ELEVATED FIRE WEATHER CONCERNS CONTINUE TODAY THROUGH THURSDAY
RESULTING FROM MULTIPLE CAUSES. TODAY IS SEEING HOT AND DRY
CONDITIONS. MINIMUM RELATIVE HUMIDITIES WILL FALL AS LOW AS 20% TO
30% AGAIN LATER THIS AFTERNOON, WITH THE DRIER LOCATIONS ACROSS THE
SOUTHERN PUGET SOUND AND PORTIONS OF THE CASCADES AND OLYMPICS.
THERE IS A CHANCE OF THUNDERSTORMS COMING IN FROM THE SOUTH LATE
WEDNESDAY NIGHT THROUGH THURSDAY WITH THE ARRIVAL OF THE REMNANTS OF
TROPICAL STORM ELIDA, WHICH, GIVEN THE WARM AND DRY CONDITIONS,
COULD CAUSE ADDITIONAL IGNITIONS FROM LIGHTNING. RAINFALL FROM THESE
STORMS WILL MAINLY BE LIGHT. A RED FLAG WARNING WAS ISSUED FOR THE
SOUTHERN CASCADES, SOUTH SOUND, AND OLYMPIC PENINSULA AREAS TONIGHT
THROUGH THURSDAY NIGHT.
INCREASING ONSHORE FLOW BEGINNING LATER THURSDAY WILL BRING A WIND
SHIFT WITH BREEZY SOUTHWEST WINDS. THIS WILL ALSO PRODUCE COOLER
TEMPERATURES AND BETTER OVERNIGHT RH RECOVERIES THROUGH THE WEEKEND
INTO THE FIRST PART OF NEXT WEEK EASING FIRE WEATHER CONCERNS.
FELTON/JBB
SEW WATCHES/WARNINGS/ADVISORIES
WA...RED FLAG WARNING UNTIL 10 PM PDT THURSDAY FOR BLACK HILLS AND
SOUTHWEST INTERIOR LOWLANDS-CENTRAL COASTAL LOWLANDS-EAST
PORTION OF THE OLYMPIC MOUNTAINS-NORTH COASTAL LOWLANDS-
NORTH AND CENTRAL COASTAL STRIP-WEST PORTION OF THE
OLYMPIC MOUNTAINS-WEST SLOPES OF THE CENTRAL CASCADES
GENERALLY ABOVE 1500 FEET.
HEAT ADVISORY UNTIL 11 PM PDT THIS EVENING FOR CITY OF SEATTLE-
DOWNTOWN EVERETT / MARYSVILLE AREA-EASTERN KITSAP COUNTY-
EASTERN STRAIT OF JUAN DE FUCA-EASTSIDE-FOOTHILLS AND
VALLEYS OF CENTRAL KING COUNTY-FOOTHILLS AND VALLEYS OF
PIERCE AND SOUTHERN KING COUNTIES-FOOTHILLS AND VALLEYS
OF SNOHOMISH AND NORTHERN KING COUNTIES-FOOTHILLS AND
VALLEYS OF THURSTON AND LEWIS COUNTIES-FOOTHILLS AND
VALLEYS OF THE NORTH CASCADES-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-
LOWLANDS OF WESTERN SKAGIT AND NORTHWESTERN SNOHOMISH
COUNTIES-LOWLANDS OF WESTERN WHATCOM COUNTY-MIDDLE
CHEHALIS RIVER VALLEY-NORTHERN HOOD CANAL-OLYMPIA AND
SOUTHERN PUGET SOUND-PORT TOWNSEND AREA-SHORELINE /
LYNNWOOD / SOUTH EVERETT AREA-SOUTHERN HOOD CANAL.
PZ...SMALL CRAFT ADVISORY FROM 8 PM THIS EVENING TO 5 AM PDT
THURSDAY FOR CENTRAL U.S. WATERS STRAIT OF JUAN DE FUCA-
EAST ENTRANCE U.S. WATERS STRAIT OF JUAN DE FUCA.
SMALL CRAFT ADVISORY FROM MIDNIGHT TONIGHT TO 9 AM PDT
THURSDAY FOR NORTHERN INLAND WATERS INCLUDING THE SAN
JUAN ISLANDS.
SMALL CRAFT ADVISORY UNTIL 9 AM PDT THURSDAY FOR PUGET SOUND
AND HOOD CANAL.
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