735
FXUS66 KSEW 192306
AFDSEW
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SEATTLE WA
406 PM PDT SAT APR 19 2025
SYNOPSIS
LIGHT ISOLATED SHOWERS POSSIBLE TODAY. A TROUGH WILL
BRING WIDESPREAD RAIN TO WESTERN WASHINGTON SUNDAY. POST TROUGH
CONVERGENCE ZONE MAY LEAD TO ADDITIONAL INCHES OF SNOW ALONG THE
PASSES SUNDAY EVENING. CONDITIONS WILL BEGIN TO DRY OUT ON MONDAY.
HIGH PRESSURE WILL BRING DRY AND WARMER CONDITIONS THROUGH
MIDWEEK. PRECIPITATION CHANCES RETURN LATE IN THE WEEK.
SHORT TERM /TONIGHT THROUGH TUESDAY/
LATEST SATELLITE IMAGERY
SHOWS MOSTLY CLEAR TO PARTLY CLOUDY SKIES ACROSS WESTERN
WASHINGTON THIS AFTERNOON. RADAR ACTIVITY REMAINS PRETTY QUIET AS
WELL, BESIDES SOME LIGHT ISOLATED FLEETING SHOWERS. OVERALL,
CONDITIONS LOOK TO REMAIN GENERALLY DRY THIS AFTERNOON INTO MOST
OF TONIGHT. AN UPPER LEVEL TROUGH WILL MOVE ACROSS THE AREA ON
SUNDAY BRINGING LOWLAND RAIN AND MOUNTAIN SNOW. LOWLAND
ACCUMULATIONS WILL BE LIGHT, AROUND 0.05-0.25 INCHES, AND SNOW
ACCUMULATIONS BETWEEN 2.00-3.00 INCHES. SNOW LEVELS ON SUNDAY WILL
BE AROUND 3500-4000 FT AND WILL LOWER TO AROUND 2800-3000 FT LATE
SUNDAY NIGHT. MODELS ARE IN GENERAL AGREEMENT FOR A CONVERGENCE
ZONE DEVELOPING SUNDAY AFTERNOON/EVENING ALONG CENTRAL PUGET SOUND
AND THE CENTRAL CASCADES. IN ADDITION, SOME HIGH-RESOLUTION
MODELS HINT AT A BAND SETTLING OVER SNOQUALMIE PASS. DEPENDING ON
WHERE THE BAND SETS UP, ADDITIONAL LOCALIZED AMOUNTS ARE POSSIBLE
ALONG SNOQUALMIE PASS. HREF PROBABILITIES SHOW THERE IS A 40%
CHANCE OF EXCEEDING 6 INCHES AT SNOQUALMIE PASS. CONVERGENCE ZONE
ACTIVITY WILL GRADUALLY WEAKEN EARLY MONDAY MORNING.
CONDITIONS WILL BEGIN TO GRADUALLY DRY OUT ON MONDAY AS THE UPPER
LEVEL TROUGH CONTINUES TO PUSH EASTWARD AND UPPER LEVEL RIDGING
BUILDS OFFSHORE. A WEAK SHORTWAVE WILL MOVE OVER THE REGION ON
TUESDAY; HOWEVER LITTLE TO NO PRECIPITATION IS EXPECTED WITH THIS
SYSTEM AT THIS TIME.
LONG TERM /WEDNESDAY THROUGH SATURDAY/
THERE IS GOOD AGREEMENT
AMONG ENSEMBLE GUIDANCE THAT WESTERN WASHINGTON WILL BE UNDER
UPPER LEVEL RIDGING ON WEDNESDAY AND THURSDAY, BRINGING WARMER
AND DRY CONDITIONS. TEMPERATURES WILL PEAK ON THURSDAY, WITH HIGHS
REACHING THE UPPER 60S ALONG THE INTERIOR. SOME LOCATIONS ALONG
THE SOUTHERN INTERIOR MAY APPROACH 70 DEGREES. THE RIDGE WILL
BEGIN TO PUSH OUT OF THE REGION LATE THURSDAY NIGHT AHEAD OF AN
INCOMING TROUGH. THERE IS SOME DISAGREEMENT AMONG ENSEMBLE MEMBERS
IN TERMS OF STRENGTH, TIMING, AND TRAJECTORY WITH THIS TROUGH.
HOWEVER, THERE IS GOOD AGREEMENT AMONG ENSEMBLES THAT COOLER AND
UNSETTLED CONDITIONS ARE FAVORED LATE IN THE WEEK INTO THE
WEEKEND.
29
AVIATION
NORTHWESTERLY FLOW WILL PERSIST ALOFT TODAY AS AN
UPPER LEVEL TROUGH GRADUALLY DEEPENS OVER THE REGION INTO SUNDAY.
CONDITIONS HAVE PRIMARILY REBOUNDED TO VFR ACROSS THE AREA
TERMINALS THIS AFTERNOON AND SHOULD REMAIN MOSTLY VFR THROUGH THE
EVENING HOURS - OUTSIDE OF ANY LINGERING LIGHT SHOWER ACTIVITY.
MORE WIDESPREAD MVFR CEILINGS ARE EXPECTED HEADED INTO SUNDAY
MORNING AS THE NEXT DISTURBANCE CROSSES THE REGION. AS A RESULT,
SHOWER ACTIVITY WILL INCREASE ACROSS THE REGION OVERNIGHT INTO
SUNDAY MORNING. BREEZY SURFACE WINDS TO 20-25 KT REMAIN LIKELY
INTO THIS EVENING FOR TERMINALS ALONG THE PACIFIC COAST AND ALONG
THE STRAIT OF JUAN DE FUCA. ELSEWHERE, WINDS HAVE BEEN MOSTLY
WEST- SOUTHWESTERLY, PERSISTING AT 5-10 KTS THIS AFTERNOON. THE
EXCEPTION IS KPAE, WHICH REMAINS NORTHERLY AT 5-10 KT. EXPECT
WINDS TO EASE TONIGHT AND FOR THE INTERIOR TERMINALS TO SEE A MORE
WIDESPREAD SHIFT BACK TO THE SOUTHWEST.
KSEA...CEILINGS HAVE REBOUNDED TO VFR THIS AFTERNOON. SOME LIGHT
SHOWER ACTIVITY IS STILL POSSIBLE IN THE VICINITY OF THE TERMINAL
THROUGH THIS EVENING AND COULD BRIEFLY DROP CONDITIONS DOWN TO
MVFR AT TIMES. WINDS REMAIN OUT OF THE SOUTH, PERSISTING AT 5 TO
10 KT, BEFORE EASING AGAIN THIS EVENING. SHOWER ACTIVITY WILL
INCREASE IN THE VICINITY OF THE TERMINAL OVERNIGHT, WITH CEILINGS
LOOKING TO DROP TO MVFR BETWEEN 12-15Z SUNDAY MORNING. A PSCZ LOOKS
TO DEVELOP LATE SUNDAY AFTERNOON INTO EVENING, LIKELY SINKING
SOUTHWARD TOWARDS THE TERMINAL BY SUNDAY NIGHT.
14
MARINE
NORTHWESTERLY WINDS WILL REMAIN BREEZY ACROSS THE
COASTAL WATERS TODAY IN THE WAKE OF A FRONTAL SYSTEM THAT MOVED
THROUGH EARLIER THIS MORNING. HIGH PRESSURE WILL BUILD ACROSS THE
NORTHEASTERN PACIFIC THIS WEEKEND, THOUGH ANOTHER DISTURBANCE
WILL MOVE ALONG ITS PERIPHERY AND ACROSS THE AREA WATERS SUNDAY
INTO MONDAY. ONSHORE FLOW WILL CONTINUE, WITH ANOTHER ROUND OF
SMALL CRAFT STRENGTH WESTERLIES EXPECTED DOWN THE STRAIT OF JUAN
DE FUCA THIS AFTERNOON AND EVENING. ANOTHER ONSHORE PUSH IS
EXPECTED ALONG THE STRAIT SUNDAY NIGHT INTO MONDAY, LIKELY
YIELDING ANOTHER ROUND OF SMALL CRAFT HEADLINES. HIGH PRESSURE
WILL THEN PERSIST ACROSS THE NORTHEASTERN PACIFIC THROUGH MIDWEEK,
BEFORE WEAKENING ON THURSDAY AS THE NEXT SYSTEM APPROACHES THE
WATERS THURSDAY NIGHT INTO FRIDAY.
SEAS ACROSS THE COASTAL WATERS REMAIN STEEP AND GENERALLY PERSIST
BETWEEN 8-10 FT AT AROUND 8-10 SECONDS THIS AFTERNOON. SEAS WILL
SUBSIDE TOWARDS 7-9 FT BY TONIGHT, BEFORE FALLING TO 6-8 FT ON
SUNDAY. A BRIEF UPTICK TOWARDS 10 FT IS POSSIBLE AGAIN LATE SUNDAY
INTO MONDAY, BEFORE SEAS SUBSIDE TOWARDS 4-6 FT ON TUESDAY.
14
HYDROLOGY
NO RIVER FLOODING EXPECTED IN THE NEXT 7 DAYS.
SEW WATCHES/WARNINGS/ADVISORIES
WA...NONE.
PZ...SMALL CRAFT ADVISORY UNTIL 3 AM PDT SUNDAY FOR ADMIRALTY INLET-
CENTRAL U.S. WATERS STRAIT OF JUAN DE FUCA-EAST ENTRANCE
U.S. WATERS STRAIT OF JUAN DE FUCA-WEST ENTRANCE U.S.
WATERS STRAIT OF JUAN DE FUCA.
SMALL CRAFT ADVISORY UNTIL 5 AM PDT SUNDAY FOR COASTAL WATERS
FROM CAPE FLATTERY TO JAMES ISLAND 10 TO 60 NM-COASTAL
WATERS FROM CAPE FLATTERY TO JAMES ISLAND OUT 10 NM-COASTAL
WATERS FROM JAMES ISLAND TO POINT GRENVILLE 10 TO 60 NM-
COASTAL WATERS FROM JAMES ISLAND TO POINT GRENVILLE OUT 10
NM-COASTAL WATERS FROM POINT GRENVILLE TO CAPE SHOALWATER
10 TO 60 NM-COASTAL WATERS FROM POINT GRENVILLE TO CAPE
SHOALWATER OUT 10 NM.
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