434
FXUS66 KSEW 121038
AFDSEW
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SEATTLE WA
338 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/
MOST RECENT TEMPERATURE
READINGS ACROSS WESTERN WASHINGTON EARLY THIS MORNING SHOW MANY
SPOTS STILL HOVERING IN THE 60S TO MID 70S ACROSS THE AREA. SOME
OVERNIGHT LOWS MAY STRUGGLE TO DIP DOWN MUCH PAST THE UPPER 60S
THIS MORNING, ESPECIALLY IN THE URBAN AREAS- PROVIDING LITTLE RELIEF
FROM THE HEAT. 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 WITH PATCHY FOG NEAR THE COAST AND STRAIT OF
JUAN DE FUCA DISSIPATING BY 15Z. 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
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.
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 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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