225  
FXUS66 KSEW 101559  
AFDSEW  
 
AREA FORECAST DISCUSSION  
NATIONAL WEATHER SERVICE SEATTLE WA  
859 AM PDT THU JUL 10 2025  
   
UPDATE  
NO CHANGES TO THE OVERALL FORECAST. PLEASE SEE THE  
AVIATION AND MARINE SECTIONS BELOW FOR UPDATES TO THOSE  
FORECASTS.  
 
 
   
SYNOPSIS  
HIGH PRESSURE WILL BUILD INTO THE REGION INTO THE  
WEEKEND AND THROUGH THE FIRST HALF OF NEXT WEEK, RESULTING IN  
WARM AND DRY CONDITIONS ACROSS WESTERN WASHINGTON. THE HEAT IS  
EXPECTED TO PEAK NEXT WEDNESDAY, WHERE TEMPERATURES COULD REACH  
THE LOW TO MID 90S ACROSS MUCH OF THE REGION.  
 
 
   
SHORT TERM /TODAY THROUGH SATURDAY/  
POST FRONTAL ONSHORE  
FLOW THIS MORNING WILL MAINTAIN CLOUDY SKIES AS LIGHT SHOWER  
ACTIVITY TAPERS OFF OVER THE NORTH CASCADES AND ALONG THE  
NORTHERN COAST. THE MARINE LAYER WILL PERSIST ALONG THE COAST  
THROUGHOUT THE DAY TODAY BUT WILL BURN OFF BY THE EARLY  
AFTERNOON ACROSS THE INTERIOR LOWLANDS, GIVING WAY TO MOSTLY  
SUNNY SKIES AS HIGH PRESSURE BUILDS OFFSHORE. THE CLOUDY SKIES  
WILL LIMIT HIGH TEMPERATURES ALONG THE COAST TODAY TO THE MID  
60S, WITH TEMPERATURES PEAKING IN THE LOWER 70S FURTHER INLAND.  
 
A WEAK RIDGE WILL PASS OVER THE REGION ON FRIDAY, ALLOWING  
TEMPERATURES TO REBOUND BACK INTO THE LOWER 80S ACROSS MUCH OF THE  
LOWLANDS. WEAKENING ONSHORE FLOW WILL MAINTAIN CLOUDY SKIES ALONG  
THE PACIFIC COAST WITH MOSTLY CLEAR AND DRY CONDITIONS ELSEWHERE.  
ZONAL FLOW WILL RESUME OVER THE REGION ON SATURDAY AS A WEAK  
DISTURBANCE PASSES OVER THE PERIPHERY OF THE UPPER LEVEL RIDGE  
BUILDING OFFSHORE, WHICH WILL MAINTAIN NEARLY IDENTICAL CONDITIONS  
TO FRIDAY ACROSS WESTERN WASHINGTON THROUGH THE WEEKEND.  
 
 
   
LONG TERM /SATURDAY NIGHT THROUGH WEDNESDAY/  
CONDITIONS ON SUNDAY AND  
MONDAY WILL BRING MORE OF THE SAME UNDER ZONAL FLOW AS HIGH  
PRESSURE CONTINUES TO BUILD OFFSHORE, WITH LIGHT SURFACE ONSHORE  
FLOW AND HIGHS IN THE LOW TO MID 80S.  
 
A HIGH PRESSURE RIDGE SITUATED OFFSHORE WILL SHARPLY AMPLIFY  
DURING THE FIRST HALF OF NEXT WEEK, BRINGING MUCH WARMER  
CONDITIONS AND WIDESPREAD MODERATE (ORANGE) HEATRISK TO WESTERN  
WASHINGTON ON TUESDAY AND WEDNESDAY. BY TUESDAY, THE OFFSHORE  
RIDGE WILL SHARPLY AMPLIFY AND A THERMALLY INDUCED SURFACE TROUGH  
IS ON TRACK TO DEVELOP ALONG THE PACIFIC NORTHWEST COASTLINE.  
HIGHS WILL REACH THE 90S ON TUESDAY FOR AREAS SOUTH OF THE PUGET  
SOUND AND ALONG SOME CASCADE FOOTHILL AND VALLEY LOCATIONS.  
TEMPERATURES WILL CONTINUE TO INCREASE INTO WEDNESDAY AS THE HIGH  
PRESSURE OFFSHORE CONTINUES TO BUILD AND THE THERMAL TROUGH  
SHIFTS NORTHWARD, WITH AREAS ACROSS THE PUGET SOUND LOWLANDS ON  
TRACK TO REACH THE MID 90S. A FEW DAILY TEMPERATURE RECORDS MAY BE  
BROKEN TOWARDS THE MIDDLE OF NEXT WEEK, AND A SHIFT TO EASTERLY  
WINDS THROUGH THE CASCADE GAPS WILL LIKELY BRING ELEVATED FIRE  
WEATHER CONCERNS TO THE REGION.  
 
15  
 
 
   
AVIATION  
A WEAK TROUGH IS SWINGING A FRONT ACROSS W WA THIS  
MORNING. THE FLOW ALOFT WILL TURN MORE NORTHWESTERLY TODAY WITH THIS  
TROUGH. RADAR IS TRACKING LIGHT SHOWERS/DRIZZLE MOVING EASTWARD. A  
SMALLER BAND OF SHOWERS IS TRACKING INLAND ALONG THE COAST. THESE  
WILL BE HIT AND MISS AROUND THE TERMINALS (GIVEN THE SCATTERED  
NATURE).  
 
CONDITIONS CURRENTLY ARE A MIX OF VFR/MVFR/IFR. MVFR DECKS  
(EXPECTATION IS 2,000-3,000 FT BASES). A FEW SPOTS FROM KPAE TO KHQM  
MAY SEE CIGS DROP BELOW 1,000 FT. MIST MAY DROP VISIBILITIES AT  
COASTAL TERMINALS DOWN TO 2 SM. ONCE THE TROUGH CLEARS THIS  
AFTERNOON, A TRANSIENT RIDGE WILL CLEAR UP MOST CEILINGS (INTERIORS  
WILL SEE IMPROVEMENT TO VFR AS EARLY AS 21Z, WITH SCATTERING TAKING  
PLACE THIS EVENING. ANOTHER PUSH WILL BE POSSIBLE FRIDAY MORNING  
WITH LOWER CEILINGS AS THE ONSHORE FLOW TRANSLATES DOWN TO THE  
SURFACE.  
 
SOUTHWEST WINDS THIS MORNING. THESE WINDS WILL DECREASE THROUGH THE  
DAY, AND TURN NORTHWESTERLY LATE THIS AFTERNOON AND EVENING  
REGIONWIDE AT 4 TO 8 KT.  
 
KSEA...FEW HIT OR MISS SHOWERS POSSIBLE AT THE TERMINAL THIS MORNING  
WITH MVFR CIGS. VFR IS FAVORED TO RETURN AROUND 20-21Z. THE CHANCE  
FOR MVFR FRIDAY MORNING IS SLIGHTLY LOWER, BUT A MARINE PUSH IS  
EXPECTED TO PUSH STRATUS INLAND FROM THE SOUTHWEST. SOUTHWEST WINDS  
4-8 KT WILL DECREASE THIS MORNING, AND TURN NORTHWESTERLY BY 22-00Z.  
 
HPR/MCMILLIAN  
 
 
   
MARINE  
AN OCCLUDED FRONT IS MOVING INLAND THIS MORNING WITH A  
PASSING UPPER LEVEL TROUGH. SOME SCATTERED SHOWERS ARE ONGOING WITH  
THIS TROUGH IN SOME OF THE INLAND WATERS, AND THE COASTAL WATERS  
WILL SEE SOME SHOWERS AS WELL THIS MORNING. ADDITIONALLY, AREAS OF  
LOCALLY DENSE FOG WILL BE POSSIBLE AGAIN THIS MORNING AS THE FRONT  
PASSES. THE COVERAGE IS NOT EXPECTED TO BE WIDESPREAD ENOUGH FOR A  
MARINE DENSE FOG ADVISORY, BUT MAY OPT TO DO A SPECIAL WEATHER  
STATEMENT LATER IN THE MORNING IF FOG DOES DEVELOP. VISIBILITIES  
DOWN TO A MILE ARE POSSIBLE, WITH ISOLATED AREAS SEEING LESS THAN A  
MILE.  
 
THE FLOW OVER THE WATERS WILL TURN NORTHWESTERLY LATER TODAY POST  
FRONT. DIURNAL PUSHES WILL CONTINUE THROUGH THE STRAIT (BUT AT THIS  
TIME DO NOT APPEAR THEY WILL REACH SMALL CRAFT ADVISORY CRITERIA). A  
TROUGH PASSING TO THE NORTH EARLY NEXT WEEK MAY PRODUCE GUSTY WINDS  
IN THE OUTER COASTAL WATERS, ALONG WITH STEEPER SEAS.  
 
SEAS WILL RANGE 3-4 FEET TODAY, INCREASE TO 4-6 FEET FRIDAY, AND  
FURTHER INCREASE TO 6 TO 9 FEET SUNDAY THROUGH WEDNESDAY, COUPLE  
SPOTS FURTHER OFFSHORE MAY SEE 10 FEET SEAS.  
 
HPR/MCMILLIAN  
 
 
   
FIRE WEATHER  
COOLER AND MORE MOIST CONDITIONS WILL BEGIN TO CEASE  
LATER TODAY AS SKIES CLEAR AND CONDITIONS BEING TO WARM UP WITH A  
WEAK UPPER LEVEL RIDGE BUILDING OVER THE AREA. FRIDAY WILL BE THE  
WARMEST AND DRIEST DAY OF THE WORK WEEK WITH RH VALUES DROPPING  
BACK INTO THE 25% TO 35% RANGE OVER THE MOUNTAINS AND ACROSS THE  
INTERIOR LOWLANDS SOUTH OF THE PUGET SOUND. MORE ROBUST ONSHORE  
FLOW WILL HELP USHER IN MOIST AIR THIS WEEKEND DESPITE HIGH  
TEMPERATURES REMAINING IN THE 80S.  
 
WHILE THERE IS SOME MODEL DISCREPANCY, THERE IS CONSENSUS THAT A  
MORE ROBUST UPPER LEVEL RIDGE WILL BEING TO BUILD AND MOVE INTO THE  
AREA BY THE MIDDLE OF NEXT WEEK. MODELS ARE BEGINNING SHOW THE  
DEVELOPMENT OF A THERMAL TROUGH ALONG THE COAST, WHICH WOULD ALLOW  
FOR WINDS TO SHIFT TO OFFSHORE, PROMOTING MUCH DRIER AND WARMER  
CONDITIONS AS WELL AS SOME POTENTIAL BREEZY WINDS THROUGH THE  
CASCADE GAPS. THIS PATTERN WILL CONTINUE TO BE CLOSELY MONITORED AS  
WE APPROACH NEXT WEEK.  
 
62  
 
 
 
   
SEW WATCHES/WARNINGS/ADVISORIES  
 
WA...NONE.  
PZ...NONE.  
 
 
 
 
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