491  
FXUS66 KSEW 101521  
AFDSEW  
 
AREA FORECAST DISCUSSION  
NATIONAL WEATHER SERVICE SEATTLE WA  
821 AM PDT SUN AUG 10 2025  
   
SYNOPSIS
 
HIGH PRESSURE WILL CONTINUE TO BUILD INTO THE  
REGION THROUGH EARLY NEXT WEEK, BRINGING A WARMING AND DRYING  
TREND. WIDESPREAD MODERATE (ORANGE) HEATRISK WILL CONTINUE  
ACROSS THE LOWLANDS THROUGH TUESDAY, AND A HEAT ADVISORY REMAINS  
IN EFFECT ACROSS THE LOWLANDS. AN UPPER TROUGH WILL MOVE INTO  
THE AREA TOWARDS THE SECOND HALF OF NEXT WEEK, BRINGING IN  
COOLER AND CLOUDIER CONDITIONS WITH INCREASING CHANCES FOR RAIN.  
 

 
   
UPDATE
 
CLEAR SKIES ARE IN PLACE ACROSS WESTERN WA THIS  
MORNING WITH THE EXCEPTION OF SOME LOCALIZED SMOKE FROM THE BEAR  
GULCH FIRE IN MASON COUNTY AND FOG IN THE LOWER CHEHALIS RIVER  
VALLEY AND GRAYS HARBOR (WHICH WILL BURN OFF THIS MORNING). THE  
CURRENT FORECAST IS ON TRACK AN NO UPDATES ARE PLANNED THIS  
MORNING.  
-WOLCOTT-  
 

 
   
SHORT TERM /TODAY THROUGH TUESDAY/
 
A RIDGE OF HIGH PRESSURE  
CENTERED OVER THE PACIFIC WILL CONTINUE TO AMPLIFY THROUGH THE  
SHORT-TERM, RESULTING IN WARM AND DRY CONDITIONS ACROSS WESTERN  
WASHINGTON. FOG AND LOW STRATUS HAS SET UP ALONG THE PACIFIC  
COAST AND THROUGH THE STRAIT OF JUAN DE FUCA EARLY THIS MORNING,  
BUT WILL BURN OFF BY THE AFTERNOON WITH CLEAR SKIES AND WARMING  
RESUMING ACROSS THE REGION. TEMPERATURES TODAY WILL REACH THE  
MID TO UPPER 80S ACROSS MUCH OF THE LOWLANDS, WITH POCKETS OF 90  
DEGREES ACROSS THE CHEHALIS RIVER BASIN SOUTHWEST OF OLYMPIA.  
THIS WILL RESULT IN WIDESPREAD MODERATE (ORANGE) HEATRISK ACROSS  
THE LOWLANDS, AND ELEVATED OVERNIGHT LOW TEMPERATURES IN THE  
UPPER 50S TO LOW 60S WILL PROVIDE LITTLE RELIEF TO THE DAYTIME  
HEAT. A HEAT ADVISORY REMAINS IN EFFECT ACROSS MOST LOWLAND  
AREAS FOR SUNDAY AFTERNOON, AND THE ADVISORY CONTINUES THROUGH  
TUESDAY EVENING AS TEMPERATURES WILL REMAIN ELEVATED.  
 
WARMING WILL CONTINUE ON MONDAY AS HIGH PRESSURE CONTINUES TO  
BUILD INTO WESTERN WASHINGTON. AS A THERMAL TROUGH FORMS ALONG  
THE COAST, MONDAY WILL BE THE WARMEST DAY FOR COASTAL AREAS.  
TEMPERATURES WILL INCREASE INTO THE UPPER 80S AND LOW 90S ACROSS  
THE REGION, WITH THE WARMEST TEMPERATURES SOUTHWEST OF THE PUGET  
SOUND AND SOUTHWARD ALONG THE I-5 CORRIDOR. CLEAR SKIES AND LIGHT  
WINDS WILL PREVAIL ONCE AGAIN, WITH EVEN WARMER OVERNIGHT LOWS IN  
THE MID 60S FOR MUCH OF THE LOWLANDS.  
 
THE THERMAL TROUGH WILL SHIFT INLAND ON TUESDAY, RESULTING IN  
EVEN WARMER TEMPERATURES ACROSS THE INTERIOR LOWLANDS AND SUBTLE  
COOLING ALONG THE COAST. WHILE SOME UNCERTAINTY REMAINS OVER  
TEMPERATURES ON TUESDAY, ENSEMBLES MAINTAIN HIGH CHANCES OF 90  
DEGREES OR HIGHER ACROSS THE METRO AREAS EAST AND SOUTH OF THE  
PUGET SOUND. ENSEMBLES SHOW A MODERATE (60% TO 70%) CHANCE OF  
REACHING 90 DEGREES ON TUESDAY IN SEATTLE, AND A HIGHER (70% TO  
80%) CHANCE OF 90 DEGREES OR HIGHER IN OLYMPIA. THE WARMEST  
TEMPERATURES ARE ON TRACK TO OCCUR SOUTH OF THE PUGET SOUND AND  
ALONG THE CASCADE FOOTHILLS, WITH CONTINUED WIDESPREAD MODERATE  
HEATRISK ACROSS THE LOWLANDS.  
   
LONG TERM /WEDNESDAY THROUGH SATURDAY/
 
WHILE FORECAST MODELS  
CONTINUE TO STRUGGLE TO PREDICT THE BREAKDOWN OF THE UPPER RIDGE,  
MOST ENSEMBLE MEMBERS SHOW A PATTERN CHANGE BY WEDNESDAY WITH A  
TROUGH MOVING OVER THE PACIFIC NORTHWEST. THIS WILL BRING  
TEMPERATURES BACK TO NEAR-NORMAL, PEAKING IN THE UPPER 70S ACROSS  
THE LOWLANDS AND IN THE MID TO UPPER 60S ALONG THE COAST.  
INCREASED ONSHORE FLOW WILL PROMOTE CONTINUED COOLER TEMPERATURES  
AND PERIODS OF CLOUDY SKIES THROUGH THE REMAINDER OF THE WEEK AS A  
SERIES OF TROUGHS IS SET TO PASS OVER THE REGION. CHANCES FOR  
RAINFALL INCREASE THURSDAY THROUGH SATURDAY, PRIMARILY OVER HIGHER  
TERRAIN, BUT THE EXACT PLACEMENT AND INTENSITY REMAINS UNCERTAIN  
AT THIS TIME.  
 
15  
 

 
   
AVIATION
 
UPPER LEVEL RIDGE WITH NORTHWESTERLY FLOW ALOFT INTO  
MONDAY. NORTHWESTERLY SURFACE GRADIENTS TODAY GOING LIGHT TONIGHT  
INTO MONDAY AS THERMALLY INDUCED SURFACE TROUGH MOVES UP THE  
COASTLINE THEN INLAND MONDAY.  
 
THE FOG HAS BEGAN TO SCATTER OUT OF KHQM THIS MORNING AND CONDITIONS  
HAVE IMPROVED. IFR/LIFR STRATUS RETURNING TO THE COAST AFTER 02Z-03Z  
TONIGHT. OTHERWISE, VFR WILL PREVAIL FOR THE REST OF THE TERMINALS  
TODAY.  
 
KSEA...MOSTLY CLEAR SKIES TODAY, WITH VFR PREVAILING. NORTHEAST WIND  
6 TO 10 KNOTS THIS MORNING BECOMING NORTH NORTHWEST 10 TO 12 KNOTS  
AROUND 18Z-19Z. WINDS EASING TO NORTHEAST 4 TO 8 KNOTS AFTER 04Z  
TONIGHT.  
 
FELTON/29  
 

 
   
MARINE
 
HIGH PRESSURE WILL REMAIN OVER THE COASTAL WATERS THROUGH  
WEDNESDAY. A THERMALLY INDUCED SURFACE TROUGH WILL MOVE UP THE  
COASTLINE TONIGHT THEN SHIFT INLAND MONDAY AND TUESDAY. HIGH  
PRESSURE WILL WEAKEN WEDNESDAY WITH A WEAK TROUGH MOVING INTO THE  
COASTAL WATERS THURSDAY.  
 
SMALL CRAFT ADVISORY FOR THE OUTER COASTAL WATERS TODAY FOR CHOPPY  
SEAS AT 7 OR 8 FEET WITH 8 TO 9 SECOND PERIOD, WITH WINDS INCREASING  
TO 15 TO 25 KNOTS AND SEAS BUILDING TO 10 FEET TONIGHT. ON MONDAY,  
SEAS WILL CONTINUE BUILDING TO 10 TO 13 FEET. STRONG POSSIBILITY  
THAT SMALL CRAFT ADVISORY CONDITIONS WILL CONTINUE OVER THE OUTER  
COASTAL WATERS UNTIL AT LEAST TUESDAY NIGHT.  
 
SMALL CRAFT ADVISORY WESTERLIES POSSIBLE FOR THE CENTRAL AND EASTERN  
STRAIT OF JUAN DE FUCA TUESDAY.  
 
FELTON  
 

 
   
FIRE WEATHER
 
A WARMING AND DRYING TREND WILL CONTINUE TODAY  
THROUGH TUESDAY AS AN UPPER LEVEL RIDGE BUILDS OVER THE AREA AND  
A WEAK RESULTANT THERMAL TROUGH DEVELOPS ALONG THE COAST. THIS  
WILL ALLOW FOR MINIMUM RH VALUES TODAY THROUGH TUESDAY TO DIP AS  
LOW AS 25-35%, WITH THE LOWEST RH VALUES FROM THE SOUTH PUGET  
SOUND, THE SOUTHWEST INTERIOR, AND THE SOUTHERN WASHINGTON  
CASCADES. A SHORTWAVE TROUGH LOOKS TO MOVE THROUGH LATE SUNDAY  
INTO MONDAY, AND ALONG WITH THE THERMAL TROUGH, WILL RESULT IN  
POORER RH RECOVERIES AND MAY SLIGHTLY INCREASED ATMOSPHERIC  
INSTABILITY, POTENTIALLY RESULTING IN MORE ACTIVITY ON OUR  
ONGOING FIRES. MORE PERSISTENT TROUGHING IS EXPECTED TO DEVELOP  
INTO WEDNESDAY, ALLOWING FOR COOLER AND MORE MOIST AIR TO RETURN  
TO THE REGION WITH A SLIGHT CHANCE FOR LIGHT SHOWERS FOR  
PORTIONS OF THE NORTH CASCADES AND THE PACIFIC COAST BEGINNING  
THURSDAY.  
 
62  
 

 
   
SEW WATCHES/WARNINGS/ADVISORIES
 
 
WA...HEAT ADVISORY FROM 2 PM THIS AFTERNOON TO 10 PM PDT TUESDAY  
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 UNTIL 6 PM PDT MONDAY 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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