652
FXUS66 KSEW 121759
AFDSEW
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SEATTLE WA
1059 AM PDT TUE AUG 12 2025
SYNOPSIS
HOT AND DRY CONDITIONS WILL CONTINUE TODAY WITH
WIDESPREAD MODERATE HEATRISK EXPECTED ACROSS WESTERN WASHINGTON.
COOLER AND CLOUDIER CONDITIONS RETURN NEAR MIDWEEK AS TROUGHING
DEVELOPS OVER THE REGION. INCREASING CHANCES OF WIDESPREAD RAIN
ARE LIKELY FRIDAY AND SATURDAY AS A WEATHER SYSTEM MOVES ACROSS
THE AREA. LINGERING SHOWERS WILL TAPER ON SUNDAY FOR A DRIER
START TO NEXT WEEK.
SHORT TERM /TODAY THROUGH THURSDAY/
OVERALL, EXPECT ONE LAST
DAY OF HOT AND DRY CONDITIONS ACROSS THE REGION AS AN UPPER
LEVEL RIDGE CONTINUES TO RESIDE OVER THE NORTHEASTERN PACIFIC.
MEANWHILE, AT THE SURFACE, A THERMAL TROUGH WILL CONTINUE TO
MAKE ITS WAY INLAND TODAY. AFTERNOON HIGHS AT THE COAST WILL
COOL SOMEWHAT AS A RESULT- AND ARE ONLY EXPECTED TO BE IN THE
70S. MEANWHILE, AFTERNOON HIGH TEMPERATURES ACROSS THE INTERIOR
WILL PEAK IN THE MID 80S TO MID 90S, RESULTING IN WIDESPREAD
MODERATE (ORANGE) HEATRISK FOR THE AREA AGAIN TODAY. AS SUCH, A
HEAT ADVISORY REMAINS IN EFFECT FOR THE MAJORITY OF THE AREA
THROUGH TONIGHT.
THE UPPER LEVEL RIDGE WILL START TO BREAK DOWN TONIGHT INTO
WEDNESDAY AS AN UPPER LEVEL TROUGH APPROACHES THE REGION AND THE
THERMAL TROUGH CONTINUES TO PUSH FURTHER INLAND. THIS WILL ACT TO
STRENGTHEN ONSHORE FLOW AND WILL HELP USHER IN THE MARINE LAYER. THE
UPPER LEVEL SYSTEM WILL PASS TO THE NORTH OF THE AREA, BUT EXPECT
TEMPERATURES TO COOL CONSIDERABLY AREA-WIDE ON WEDNESDAY, WITH
MOST SPOTS TOPPING OUT IN THE LOW TO MID 70S ACROSS THE INTERIOR
AND IN THE MID 60S ALONG THE COAST.
CONDITIONS WILL REMAIN COOLER AND CLOUDIER INTO THURSDAY AS UPPER
LEVEL TROUGHING BECOMES THE DOMINANT INFLUENCE OVER THE AREA. HIGH
TEMPERATURES ARE EXPECTED TO BE IN THE MID 60S ALONG THE COAST AND
IN THE UPPER 60S TO MID 70S ACROSS THE INTERIOR. CHANCES OF RAIN
WILL INCREASE THROUGHOUT THE DAY ALONG THE COAST AS A FRONTAL
SYSTEM APPROACHES THE REGION. RAIN CHANCES WILL THEN START TO MOVE
INLAND BY THURSDAY NIGHT.
LONG TERM /FRIDAY THROUGH MONDAY/
A WET SYSTEM MOVING ONSHORE
FRIDAY INTO SATURDAY LOOKS TO BRING THE NEXT ROUND OF MORE WIDESPREAD
RAIN TO THE REGION. ENSEMBLES CONTINUE TO SUGGEST A 70-90 PERCENT
CHANCE OF WIDESPREAD WETTING RAIN (QUARTER OF AN INCH) WITHIN 24
TO 36 HOURS ACROSS WESTERN WASHINGTON. THE NBM 50TH PERCENTILE
SUGGESTS ANYWHERE FROM 1-2.5 INCHES OF RAIN FALLING ACROSS THE
OLYMPICS AND CASCADES, WITH SOME LOCALIZED HIGHER AMOUNTS POSSIBLE.
TEMPERATURES WILL TREND COOLER THAN NORMAL, WITH MANY SPOTS EXPECTING
TO ONLY BE IN THE 60S ON FRIDAY AND UPPER 60S TO LOW 70S ON SATURDAY.
THE COOL AIRMASS WILL BRING SNOW LEVELS TO AROUND 8500 FT BY SUNDAY.
WITH LINGERING SHOWER ACTIVITY EXPECTED TO PERSIST, ESPECIALLY
OVER THE MOUNTAINS, MAY EVEN SEE SOME LIGHT SNOW ACCUMULATIONS
OVER THE PEAKS OF RAINIER AND BAKER.
ENSEMBLE CLUSTERS SUGGEST UPPER LEVEL TROUGHING REMAINING THE
DOMINANT INFLUENCE ACROSS THE PACIFIC NORTHWEST HEADING INTO
EARLY NEXT WEEK. WITH SHOWERS HAVING TAPERED ACROSS THE REGION,
EXPECT CONDITIONS TO BE DRIER ACROSS WESTERN WASHINGTON BY MONDAY.
TEMPERATURES LOOK TO TREND JUST BELOW TO NEAR NORMAL, WITH HIGHS
ACROSS THE INTERIOR EXPECTED TO BE IN THE 70S AND HIGHS ALONG THE
COAST TRENDING IN THE UPPER 60S AT THIS TIME.
14
AVIATION
UPPER LEVEL RIDGE OFFSHORE MOVING WEST TODAY. UPPER
LEVEL TROUGH MOVING BY TO THE NORTH TONIGHT INTO WEDNESDAY.
NORTHWESTERLY FLOW ALOFT BECOMING WESTERLY TONIGHT. AT THE SURFACE
THERMALLY INDUCED TROUGH OVER THE INTERIOR WILL SHIFT EAST OF THE
CASCADES LATER TODAY AND TONIGHT. INCREASING ONSHORE FLOW TONIGHT.
CLEAR SKIES TODAY BUT CAN'T RULE OUT SMOKE EMANATING FROM THE BEAR
GULCH FIRE FOR TERMINALS SUCH AS KSHN AND POSSIBLY CLOSER TO PUGET
SOUND. STRATUS MOVING UP THE COASTLINE REACHING KHQM AROUND 03Z WITH
LIFR CEILINGS. STRATUS SPREADING INLAND OVERNIGHT WITH IFR CEILINGS
REACHING THE PUGET SOUND AREA 09Z-12Z. CEILINGS LIFTING TO MVFR MID
TO LATE MORNING WITH THE STRATUS RETREATING BACK TO THE COAST EARLY
AFTERNOON.
KSEA...CLEAR SKIES. IFR STRATUS REACHING THE TERMINAL 09Z-12Z
TONIGHT. NORTHEAST WIND 4 TO 8 KNOTS BECOMING NORTHWEST AROUND 19Z
AND SOUTHWEST AROUND 09Z. FELTON/MCMILLIAN
MARINE
HIGH PRESSURE WILL REMAIN OVER THE COASTAL WATERS
THROUGH WEDNESDAY NIGHT THEN WEAKEN THURSDAY. A THERMALLY
INDUCED SURFACE TROUGH OVER THE INLAND WATERS WILL MOVE EAST OF
THE CASCADES TONIGHT. A FRONT WILL REACH THE COASTAL WATERS
FRIDAY AND MOVE INLAND SATURDAY.
SMALL CRAFT ADVISORY OUTER COASTAL WATERS THROUGH WEDNESDAY NIGHT
FOR SEAS 10 OR 11 FEET WITH A 10 SECOND PERIOD AND NORTHERLY
WINDS OCCASIONALLY 20 TO 25 KNOTS TONIGHT AND WEDNESDAY. SEAS
SUBSIDING WEDNESDAY NIGHT BUT WILL REMAIN CHOPPY AT 8 FEET WITH AN
8 SECOND PERIOD.
SMALL CRAFT ADVISORY WESTERLIES CENTRAL AND EASTERN STRAIT OF
JUAN DE FUCA TONIGHT AND AGAIN WEDNESDAY NIGHT. FELTON
FIRE WEATHER
HOT AND DRY CONDITIONS WILL CONTINUE ACROSS
WESTERN WASHINGTON TODAY, WITH HIGH PRESSURE ALOFT AND A
THERMALLY INDUCED SURFACE TROUGH SLOWLY SHIFTING INLAND.
ELEVATED FIRE WEATHER CONDITIONS ARE EXPECTED AS A RESULT, WITH
HIGH TEMPERATURES CLIMBING INTO THE UPPER 80S TO MID 90S FOR
MOST AREAS ACROSS THE INTERIOR. EXPECT MINIMUM RH VALUES TO DROP
AS LOW AS 20% TO 35% ACROSS MUCH OF THE REGION BY THIS
AFTERNOON. ATMOSPHERIC INSTABILITY WILL LINGER OVER THE OLYMPICS
AND CASCADES TODAY, WHICH MAY RESULT IN INCREASED ACTIVITY ON
ONGOING FIRES IN THOSE AREAS.
THE UPPER RIDGE IS THEN FORECAST TO BREAK DOWN ON WEDNESDAY AS
MORE PERSISTENT TROUGHING DEVELOPS OVER THE REGION. THIS WILL HELP
MITIGATE FIRE WEATHER CONDITIONS BY BRINGING COOLER AND MORE
MOIST CONDITIONS TO THE REGION. CHANCES FOR RAINFALL THEN INCREASE
TOWARDS THE END OF THE WEEK, WITH ELEVATED PROBABILITIES OF
WETTING RAINS ACROSS THE REGION EXPECTED ON FRIDAY AND SATURDAY.
15/14
SEW WATCHES/WARNINGS/ADVISORIES
WA...HEAT ADVISORY UNTIL 10 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-LOWER CHEHALIS RIVER VALLEY-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-SHORELINE /
LYNNWOOD / SOUTH EVERETT AREA-SOUTHERN HOOD CANAL-WILLAPA
AND BLACK HILLS.
AIR QUALITY ALERT UNTIL 9 AM PDT FRIDAY FOR FOOTHILLS OF THE
WESTERN AND SOUTHERN OLYMPIC PENINSULA-MIDDLE CHEHALIS
RIVER VALLEY-OLYMPIA AND SOUTHERN PUGET SOUND-OLYMPICS-
SOUTHERN HOOD CANAL-WILLAPA AND BLACK HILLS.
PZ...SMALL CRAFT ADVISORY FROM 6 PM THIS EVENING TO 5 AM PDT
WEDNESDAY FOR CENTRAL U.S. WATERS STRAIT OF JUAN DE FUCA-
EAST ENTRANCE U.S. WATERS STRAIT OF JUAN DE FUCA.
SMALL CRAFT ADVISORY FROM 5 PM THIS AFTERNOON TO 11 PM PDT
THIS EVENING FOR COASTAL WATERS FROM JAMES ISLAND TO
POINT GRENVILLE OUT 10 NM-COASTAL WATERS FROM POINT
GRENVILLE TO CAPE SHOALWATER OUT 10 NM.
SMALL CRAFT ADVISORY UNTIL 6 AM PDT THURSDAY FOR COASTAL
WATERS FROM CAPE FLATTERY TO JAMES ISLAND 10 TO 60 NM-
COASTAL WATERS FROM JAMES ISLAND TO POINT GRENVILLE 10 TO
60 NM-COASTAL WATERS FROM POINT GRENVILLE TO CAPE
SHOALWATER 10 TO 60 NM.
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