624
FXUS66 KSEW 091617
AFDSEW
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SEATTLE WA
917 AM PDT MON JUN 9 2025
SYNOPSIS
AN UPPER LEVEL RIDGE OVER THE REGION WILL PRODUCE
WARM TEMPERATURES AGAIN TODAY. THE RIDGE WILL BEGIN TO WEAKEN
TONIGHT AND ONSHORE FLOW WILL INCREASE FOR COOLING TEMPERATURES.
AN UPPER LEVEL TROUGH WILL SETTLE OVER THE REGION FOR THE SECOND
HALF OF THE WEEK FOR COOLER TEMPERATURES AND INCREASED CLOUD
COVER.
UPDATE
MINOR UPDATE TO THE AVIATION SECTION THIS MORNING.
OTHERWISE NO MAJOR CHANGES - ONE MORE HOT DAY FOR WESTERN WA TODAY
AND A HEAT ADVISORY REMAINS IN EFFECT UNTIL 10 PM PDT TONIGHT.
HPR
SHORT TERM /TODAY THROUGH WEDNESDAY/
THERMALLY INDUCED LOW
PRESSURE REMAINS ORIENTED OVER THE INTERIOR OF WESTERN WASHINGTON
EARLY THIS MORNING. MARINE STRATUS IS GRADUALLY CREEPING NORTHWARD
ALONG THE OREGON COAST, BUT HAD YET TO REACH THE OREGON BORDER AS
OF 07Z. ONSHORE GRADIENTS REMAIN VERY LIGHT WITH OTH/SEA NEAR 1.6
MILLIBARS AND HQM/SEA AT JUST 0.6 MILLIBARS. GIVEN THE VERY WARM
PROFILE ON THE 00Z UIL SOUNDING WITH A TOASTY 19.8 C AT 850
MILLIBARS, IT'S DIFFICULT TO SEE MUCH IN THE WAY OF COOLING FOR
INTERIOR AREAS OVER YESTERDAY'S HIGH TEMPERATURES. WITH THAT SAID,
HIGH TEMPERATURES WERE NUDGED TOWARD THE NBM 75TH PERCENTILE
WHICH GIVES SEA-TAC A PROJECTED 86F TODAY...A FULL 15 DEGREES
ABOVE AVERAGE, BUT WELL SHORT OF THE RECORD 96F BACK IN 1955. HEAT
ADVISORIES REMAIN IN PLACE AND COME WITH ONGOING RECOMMENDED
PRECAUTIONS OF ADEQUATE HYDRATION AND AWARENESS THAT AREA WATERS
ARE STILL QUITE COLD.
THE UPPER RIDGE BEGINS TO WEAKEN LATER TODAY AND GRADUALLY FLATTEN
AS WE HEAD INTO TUESDAY. THIS WILL BE COUPLED WITH INCREASING LOW
LEVEL ONSHORE FLOW AND A COOLING TREND. THOUGH INITIALLY IT WILL
BE RELATIVELY WEAK FOR CONTINUED ABOVE NORMAL TEMPERATURES FOR
MOST INTERIOR AREAS ON TUESDAY. CONTINUED LOWERING HEIGHTS AND THE
APPROACH OF A WEAK UPPER TROUGH KICKS THE PACIFIC A/C MACHINE INTO
FULL THROTTLE ON WEDNESDAY. SOME DEGREE OF MORNING MARINE STRATUS
WILL LIKELY MAKE IT INTO PUGET SOUND AND HIGH TEMPERATURES
WILL BE KNOCKED BACK TO AROUND THEIR TEMPERATE NORMALS FOR THE
SECOND WEEK OF JUNE.
LONG TERM /THURSDAY THROUGH SUNDAY/
A SYNOPTIC SCALE UPPER
LEVEL TROUGH POSITION FINDS A HOME OVER THE PACIFIC NORTHWEST FOR
THE SECOND HALF OF THE WEEK INTO THE WEEKEND. THIS WILL HOLD
TEMPERATURES AROUND, IF NOT SLIGHTLY BELOW, NORMAL FOR THE TIME OF
YEAR. AT THIS TIME, IT GENERALLY APPEARS TO BE A FAIRLY DRY TROUGH
THOUGH EMBEDDED UPPER DISTURBANCES WITHIN IT MIGHT KICK OFF
ISOLATED MOUNTAIN SHOWERS OR SQUEEZE OUT SOME COASTAL DRIZZLE. IF
ANYTHING, IT'S A REMINDER THAT TRUE WESTERN WASHINGTON SUMMER IS
STILL A FEW WEEKS OFF. 27
AVIATION
NORTHWEST FLOW WILL TRANSITION MORE WESTERLY INTO MONDAY
WITH AN UPPER RIDGE OVER THE AREA. VFR WITH MOSTLY CLEAR SKIES INTO
MONDAY. N/NW SURFACE WINDS WILL INCREASE TO 6 TO 12 KT BY MIDDAY,
WITH STRONGER WINDS ALONG THE COAST UP TO AROUND 15 KT.
KSEA...VFR UNDER CLEAR SKIES THROUGH THE TAF PERIOD. N/NW SURFACE
WINDS WILL INCREASE BY MIDDAY TO 7 TO 10 KT.
15/29
MARINE
HIGH PRESSURE WILL REMAIN OVER THE COASTAL WATERS INTO
WEDNESDAY. NORTHERLY DIURNAL DRIVEN WINDS WILL CONTINUE OVER THE
INTERIOR THROUGH THE DAY TODAY. WINDS WILL TRANSITION MORE ONSHORE
LATER TUESDAY, WITH INCREASING ONSHORE FLOW ON WEDNESDAY. AN ONSHORE
FLOW PATTERN WILL THEN CONTINUE THROUGH LATER THIS WEEK.
A SMALL CRAFT ADVISORY IS IN EFFECT FROM THIS EVENING THROUGH
TUESDAY NIGHT FOR INCREASED NORTHERLY WINDS ACROSS THE OUTER COASTAL
WATERS. IN ADDITION, SEAS WILL BUILD TO 8 TO 12 FEET TODAY AND
CONTINUE TO REMAIN ELEVATED THROUGH MIDWEEK. ADDITIONAL HEADLINES
ARE POSSIBLE EACH EVENING BEGINNING WEDNESDAY THROUGH THE CENTRAL
AND EASTERN PORTIONS OF THE STRAIT OF JUAN DE FUCA DUE TO INCREASED
WEST WINDS. WE WILL ALSO CONTINUE TO MONITOR THE POTENTIAL FOR ANY
GALE FORCE WINDS FOR THE STRAIT OF JUAN DE FUCA MIDWEEK WITH THE
INCREASED ONSHORE FLOW.
15
FIRE WEATHER
WARM AND DRY CONDITIONS CONTINUE MONDAY AS AN
UPPER LEVEL RIDGE MOVES ACROSS WESTERN WASHINGTON. THIS WILL
ELEVATE FIRE WEATHER CONCERNS TODAY AS MINIMUM RH VALUES WILL
LIKELY REACH AS LOW AS 30% OVER THE MOUNTAINS WITH SLIGHTLY
HIGHER VALUES THROUGH THE INTERIOR. WHILE LIVE FUELS ARE STILL WET
ENOUGH TO CURB FIRE SPREAD, DEAD FUELS REMAIN VERY DRY. IN
ADDITION, SNOWPACK IS BELOW NORMAL AND SOME LOCATIONS ARE
EXPERIENCING DROUGHT CONDITIONS. WINDS REMAIN LIGHT ENOUGH INTO
MONDAY SUCH THAT CRITICAL FIRE WEATHER CONDITIONS ARE NOT EXPECTED
BUT THE AREA IS DRYING OUT FAST. MOIST ONSHORE FLOW WILL RETURN
MONDAY NIGHT INTO TUESDAY.
SEW WATCHES/WARNINGS/ADVISORIES
WA...HEAT ADVISORY UNTIL 10 PM PDT THIS EVENING FOR CITY OF SEATTLE-
DOWNTOWN EVERETT / MARYSVILLE AREA-EASTERN KITSAP COUNTY-
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-
LOWLANDS OF LEWIS AND SOUTHERN THURSTON COUNTIES-LOWLANDS
OF PIERCE AND SOUTHERN KING COUNTIES-NORTHERN HOOD CANAL-
OLYMPIA AND SOUTHERN PUGET SOUND-SHORELINE / LYNNWOOD /
SOUTH EVERETT AREA-SOUTHERN HOOD CANAL.
PZ...SMALL CRAFT ADVISORY UNTIL 11 PM PDT TUESDAY 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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