796
FXUS66 KSEW 180429
AFDSEW
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SEATTLE WA
929 PM PDT THU JUL 17 2025
SYNOPSIS
GRADUALLY COOLER CONDITIONS DEVELOP OVER THE REGION
AS STRENGTHENING ONSHORE FLOW BRINGS INCREASING CLOUDS AND COOLER
CONDITIONS. THE NEXT UPPER LEVEL DISTURBANCE WILL BRING COOLER
CONDITIONS LATE IN THE WEEKEND AND A RETURN OF SHOWER CHANCES,
ESPECIALLY OVER THE CASCADES, EARLY NEXT WEEK. ANOTHER WARM UP
APPEARS LIKELY TOWARD THE MIDDLE OF NEXT WEEK.
SHORT TERM /TODAY THROUGH SATURDAY NIGHT/
INCREASING ONSHORE
FLOW WILL BRING COOLER TEMPERATURES TO THE REGION OVERNIGHT AND,
IN TURN, RELIEF FROM THE HEAT. THUS, HAVE ALLOWED FOR THE HEAT
ADVISORY TO EXPIRE THIS EVENING. TEMPERATURES ACROSS THE AREA
TONIGHT GENERALLY RANGE FROM THE 50S TO 60S ALONG THE COAST TO THE
60S TO 70S ACROSS THE SOUND, THOUGH A FEW SPOTS ARE STILL REPORTING
TEMPERATURES IN THE LOW 80S ACROSS PORTIONS OF THE INTERIOR. EXPECT
ANOTHER ROUND OF STRATUS TO PUSH INLAND ALONG THE COAST AND INTO
SOUTHWEST INTERIOR TONIGHT, THOUGH EXPECT MORE MID TO HIGH LEVEL
CLOUDS TO MOVE OVERHEAD THROUGH THE DAY TOMORROW AS A WEAK
DISTURBANCE MOVES THROUGH THE REGION. OVERALL, THE FORECAST
REMAINS ON TRACK TONIGHT. THE REMAINDER OF THE PREVIOUS DISCUSSION
FOLLOWS BELOW, WITH UPDATES MADE TO THE AVIATION AND FIRE SECTIONS.
14
A WEAK DISTURBANCE WILL SWING THROUGH THE REGION ON FRIDAY,
BRINGING STRONGER ONSHORE FLOW AND PROGRESSIVELY COOLER
CONDITIONS. EXPECT MORNING CLOUDS AND COOLER CONDITIONS, WITH SOME
CLEARING SATURDAY AFTERNOON. THIS WILL BRING TEMPERATURES BACK
DOWN CLOSER TO NORMAL VALUES OVER THE WEEKEND.
LONG TERM /SUNDAY THROUGH THURSDAY/
CONTINUED ONSHORE FLOW,
ENHANCED AS AN UPPER LEVEL TROUGH SLIDES TOWARD THE REGION. THIS
MAY KNOCK TEMPERATURES DOWN TO NEAR OR JUST BELOW SEASONAL
NORMALS ON SUNDAY. ENSEMBLE GUIDANCE IS IN GOOD AGREEMENT THAT
A DEEPER UPPER TROUGH WILL SLIDE DOWN INTO THE PACIFIC NORTHWEST
ON MONDAY AND BRING A RETURN OF SHOWER CHANCES TO PORTIONS OF
THE CASCADES, ESPECIALLY NORTH OF I-90. THIS WILL KEEP COOLER
CONDITIONS AND ADDITIONAL CLOUDS FOR THE START OF THE WEEK.
ENSEMBLE GUIDANCE REMAINS A BIT MORE SPLIT TOWARD MIDWEEK, BUT
THERE'S AN INCREASING LIKELIHOOD THAT A BUILDING RIDGE OFFSHORE
WILL BRING ANOTHER WARMER AND DRIER TREND TOWARD THE MIDDLE OF
NEXT WEEK.
AVIATION
VFR CEILINGS PREVAILING TONIGHT. HOWEVER, LOWER
CEILINGS WILL RETURN OVERNIGHT, WITH MVFR CEILINGS ALONG THE
INTERIOR TERMINALS AND IFR/LIFR ALONG THE COASTAL TERMINALS IN
STRATUS. IMPROVEMENT INTO VFR EXPECTED LATE FRIDAY MORNING/FRIDAY
AFTERNOON, WITH THE EXCEPTION OF THE COAST. RATHER, CONDITIONS
WILL IMPROVE TO MVFR ALONG THE COAST.
N/NW WINDS PERSISTING TONIGHT AT 6-8 KT, WHILE MORE WESTERLY
WINDS PERSIST ALONG THE COAST AT 8-12 KT. WINDS WILL TURN SW
OVERNIGHT AND WILL BECOME BREEZY FRIDAY MORNING AROUND 8-14KT,
CONTINUING THROUGHOUT THE EVENING. THE BREEZIEST SPOTS WILL BE
ALONG THE SOUTHERN INTERIOR (KOLM), THE COAST, AND STRAIT OF JUAN
DE FUCA, WHERE GUSTS BETWEEN 15-20 KT ARE LIKELY (70%-90% CHANCE).
KSEA...VFR CONDITIONS TONIGHT, BUT MVFR CEILINGS WILL BE POSSIBLE
OVERNIGHT. IMPROVEMENT BACK TO VFR IS EXPECTED AFTER 18Z. NW
WINDS PERSISTING AT 6-8 KT WILL TURNING SW OVERNIGHT AND PERSIST
AT 4-7 KT. BREEZY SW WINDS WILL ENSUE FRIDAY MORNING AND PERSIST
THROUGHOUT THE EVENING, WITH SPEEDS OF 10-12 KT. THE PROBABILITY
OF SEEING GUSTS GREATER THAN 15 KT ARE CURRENTLY AROUND 40%-50%.
29/14
MARINE
NORTHWESTERLY SURFACE WINDS EXPECTED TO PREVAIL OVER THE
COASTAL WATERS. A COLD FRONT WILL DESCEND FROM CANADA ON FRIDAY,
BRINGING ELEVATED WINDS OVER THE OUTER COASTAL WATERS. IN ADDITION,
STEEP SEAS WITH WAVE HEIGHTS OF 8-9 FT WITH A DOMINANT PERIOD OF 9
SECONDS ARE EXPECTED. CONSEQUENTLY, A SMALL CRAFT ADVISORY HAS BEEN
ISSUED FOR THE OUTER COASTAL WATERS. WESTERLY PUSHES ACROSS THE
STRAIT OF JUAN DE FUCA WILL OCCUR EACH EVENING. TONIGHT'S WESTERLY
PUSH WILL MEET SMALL CRAFT CRITERIA, AND AN ADVISORY HAS BEEN
ISSUED. CONFIDENCE HAS ALSO INCREASED THAT A SMALL CRAFT ADVISORY
WILL LIKELY BE NEEDED FRIDAY EVENING, AS PROBABILITIES OF SEEING
SUSTAINED WIND SPEEDS OF 21 KT OR GREATER IS AROUND 70-90%. ON
FRIDAY EVENING, SURFACE HIGH PRESSURE WILL REBUILD OVER AREA WATERS,
WEAKENING ON SUNDAY INTO EARLY NEXT WEEK.
29
FIRE WEATHER
INCREASING ONSHORE FLOW TONIGHT WILL BRING COOLER
AND MORE MOIST AIR INTO THE REGION, LIKELY REACHING THE CASCADES
BY FRIDAY MORNING. COOL AND MOIST CONDITIONS WILL REMAIN THROUGH
THE WEEKEND, WITH TEMPERATURES INCREASING NEXT WEEK. THERE IS A
SLIGHT CHANCE OF SHOWERS AND ISOLATED THUNDERSTORMS IN THE NORTH
CASCADES MONDAY AND TUESDAY, WHICH MAY BRING THE RETURN OF
ELEVATED FIRE WEATHER CONDITIONS (DUE TO LIGHTNING).
HPR/14
SEW WATCHES/WARNINGS/ADVISORIES
WA...NONE.
PZ...SMALL CRAFT ADVISORY UNTIL 5 AM PDT FRIDAY FOR CENTRAL U.S.
WATERS STRAIT OF JUAN DE FUCA-EAST ENTRANCE U.S. WATERS
STRAIT OF JUAN DE FUCA.
SMALL CRAFT ADVISORY UNTIL 2 PM PDT FRIDAY 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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