890
FXUS66 KSEW 092229
AFDSEW
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SEATTLE WA
329 PM PDT SAT AUG 9 2025
SYNOPSIS
SURFACE HIGH PRESSURE WILL BUILD OVER WESTERN
WASHINGTON THROUGH THE WEEKEND AND INTO EARLY NEXT WEEK, BRINGING
WARM AND DRY CONDITIONS OVER THE REGION. MODERATE HEATRISK IS
FORECASTED FOR MOST LOWLAND AREAS SUNDAY AND MONDAY, WITH HIGH
TEMPERATURES REACHING THE UPPER 80S TO LOW 90S. HEAT CONCERNS LOOK
TO LINGER INTO TUESDAY WHERE MODERATE HEATRISK REMAINS. UPPER
LEVEL TROUGHING WILL DEVELOP BY MIDWEEK FOR COOLER TEMPERATURES
AND CHANCES OF PRECIPITATION THROUGHOUT THE REST OF THE WEEK.
SHORT TERM /TONIGHT THROUGH TUESDAY/
HIGH PRESSURE OVER THE
PACIFIC WILL CONTINUE TO BUILD INTO THE PACIFIC NORTHWEST BRINGING
WARMER AND DRIER CONDITIONS OVER THE NEXT SEVERAL DAYS. HIGH
TEMPERATURES THIS AFTERNOON ARE GENERALLY IN THE UPPER 70S TO
LOWER 80S ACROSS MOST OF THE INTERIOR, WITH MID TO UPPER 60S FOR
AREAS ALONG THE COAST, YIELDING MINOR (YELLOW) HEATRISK FOR MUCH
OF THE AREA. HEADING INTO SUNDAY, AREAS ALONG THE COAST MAY SEE
MARINE STRATUS THROUGHOUT THE MORNING BRIEFLY, BUT WILL BURN BACK
RATHER QUICKLY FOR ANOTHER DAY OF CLEAR SKIES AND WARMING
TEMPERATURES.
WE WILL SEE TEMPERATURES WARM ON SUNDAY INTO THE UPPER 80S AND
EVEN LOWER 90S FOR MOST AREAS, WITH AREAS LIKE THE SOUTHWEST
INTERIOR AND THE CASCADE FOOTHILLS BEING THE WARMEST LOCATIONS.
THESE OVERALL TEMPERATURES WILL RESULT IN MODERATE (ORANGE)
HEATRISK FOR ACROSS MUCH OF THE INTERIOR OF WESTERN WASHINGTON.
THEREFORE, A HEAT ADVISORY HAS BEEN ISSUED FOR MOST OF THE
INTERIOR ZONES AND MOUNTAIN VALLEYS STARTING SUNDAY EVENING.
OVERNIGHT TEMPERATURES INTO MONDAY WILL BE ELEVATED, IN THE LOW TO
MID 60S FOR MUCH OF THE LOWLANDS, WHICH CAN PROVIDE LITTLE RELIEF
TO THE WARM DAYTIME TEMPERATURES.
WARM AND DRY WILL CONTINUE INTO MONDAY AS THE HIGH PRESSURE
AMPLIFIES, WARMING UP TEMPERATURES ACROSS THE AREA. AFTERNOON
TEMPERATURES IN THE UPPER 80S AND LOWER TO MID 90S ACROSS MUCH OF
THE INTERIOR CAN BE EXPECTED, WITH AREAS ALONG THE SOUTHWEST
INTERIOR (CHEHALIS RIVER BASIN) AND THE CASCADE FOOTHILLS SEEING
THE WARMEST TEMPERATURES. MOST OF THE INTERIOR WILL CONTINUE TO
BE IN MODERATE (ORANGE) HEATRISK, WITH THOSE AFOREMENTIONED WARMER
LOCATIONS POTENTIALLY SEEING POCKETS OF MAJOR (RED) HEATRISK.
AGAIN, OVERNIGHT TEMPERATURES MONDAY NIGHT WILL BE IN THE LOW TO
MID 60S ACROSS MOST OF THE REGION, WHICH WILL PROVIDE LITTLE
TO NO RELIEF TO THE WARM DAYTIME TEMPERATURES, ESPECIALLY THOSE
WITHOUT EFFECTIVE COOLING.
LATEST ENSEMBLE GUIDANCE CONTINUES TO SHOW DIFFERENCES IN WHEN THE
UPPER LEVEL RIDGE WILL BEGIN TO BREAK DOWN. THE LATEST FORECAST
RUNS HAVE BEEN SUGGESTING THAT TUESDAYS TEMPERATURES WILL STILL
BE WARM, IN THE UPPER TO LOWER 90S ACROSS THE AREA, THEREFORE, THE
HEAT ADVISORY IS CONTINUED THROUGH TUESDAY EVENING TO ACCOUNT FOR
THIS.
LONG TERM /WEDNESDAY THROUGH SATURDAY/
A SERIES OF UPPER LEVEL
TROUGHS LOOK TO PASS OVER WESTERN WASHINGTON STARTING ON WEDNESDAY,
BRINGING A COOL DOWN FOR THE REGION. TEMPERATURES LOOK TO FALL
BELOW NORMAL STARTING ON WEDNESDAY, IN THE UPPER 60S TO LOWER 70S
WITH ONSHORE FLOW PROMOTING CLOUDIER CONDITIONS ACROSS THE AREA
AND PROVIDING RELIEF TO THE EARLIER WEEKS HEAT. ENSEMBLES ARE
SUGGESTING POSSIBLE RAIN CHANCES THURSDAY AND FRIDAY, BUT
CONFIDENCE IN COVERAGE AND TIMING OF THE INCOMING PRECIPITATION IS
LOW AT THIS TIME.
MAZURKIEWICZ
AVIATION
VFR WILL PERSIST THROUGHOUT THE TAF PERIOD FOR ALL
TERMINALS, WITH THE EXCEPTION OF COASTAL TERMINALS. LOW STRATUS
ALONG THE COAST SUNDAY MORNING WILL LIKELY BRING IFR/LIFR
CONDITIONS. IMPROVEMENT INTO VFR LIKELY AFTER 21Z. OTHERWISE, MOSTLY
CLEAR SKIES ON SUNDAY. GENERALLY NORTHWESTERLY WINDS THIS EVENING
BECOMING NORTHEASTERLY OVERNIGHT.
KSEA...VFR CONDITIONS WILL PREVAIL TODAY AND INTO SUNDAY.
NORTHWESTERLY SURFACE WINDS THIS AFTERNOON AROUND 9-12 KT WILL
BECOME NORTHEASTERLY THIS EVENING AROUND 6-9 KT. WINDS SWITCH BACK
TO NORTHWESTERLY SUNDAY MORNING AT 8-12 KT.
29
MARINE
SURFACE HIGH PRESSURE WILL PERSIST OVER THE COASTAL WATERS
INTO EARLY NEXT WEEK. A WEAK THERMALLY INDUCED SURFACE TROUGH WILL
MOVE UP THE COASTLINE SUNDAY NIGHT AND MOVE INLAND ON MONDAY.
A SMALL CRAFT ADVISORY HAS BEEN ISSUED FOR THE OUTER COASTAL WATERS
FOR STEEP SEAS. COMBINED SEAS WILL BUILD EARLY SUNDAY MORNING TO 7-9
FT WITH A DOMINANT PERIOD OF AROUND 7-8 SECONDS. COMBINED SEAS WILL
CONTINUE BUILDING SUNDAY NIGHT INTO TUESDAY TO 10-12 FT.
NORTHWESTERLY WINDS WILL ALSO INCREASE TO 20-25 KT. ERGO, THE SMALL
CRAFT ADVISORY IS LIKELY TO BE EXTENDED.
WESTERLY PUSHES MEETING SMALL CRAFT CRITERIA ARE POSSIBLE EACH
EVENING IN THE CENTRAL AND EASTERN STRAIT STARTING TUESDAY.
29
FIRE WEATHER
THE WARM AND DRYING TREND WILL CONTINUE ON SUNDAY
AND MONDAY 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 SUNDAY AND MONDAY TO REACH AS LOW AS 25-35%,
WITH THE LOWEST 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
INCREASE ATMOSPHERIC INSTABILITY, POTENTIALLY RESULTING IN MORE
ACTIVITY ON OUR ONGOING FIRES. MORE PERSISTENT TROUGHING IS EXPECTED
TO DEVELOP TUESDAY 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 SUNDAY 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 FROM MIDNIGHT TONIGHT TO 8 PM PDT SUNDAY
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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