510
FXUS66 KSEW 121656
AFDSEW
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SEATTLE WA
956 AM PDT WED MAR 12 2025
SYNOPSIS
LIGHT RAIN AND MOUNTAIN SNOW WILL PERSIST TODAY AS A
COLD FRONT SLOWLY MOVES ONSHORE WEDNESDAY NIGHT. SHOWERS WILL
PERSIST INTO THURSDAY WITH LOWERING SNOW LEVELS AND A CHANCE FOR
ISOLATED THUNDERSTORMS IN THE AFTERNOON. ADDITIONAL SYSTEMS WILL
MOVE THROUGH FRIDAY AND THROUGH THE WEEKEND WHICH MAY BRING MORE
SIGNIFICANT RAINFALL AND HEAVY MOUNTAIN SNOW.
SHORT TERM /TODAY THROUGH FRIDAY/...PREVIOUS DISCUSSION
SATELLITE
AND RADAR IMAGERY SHOW SCATTERED SHOWERS ACROSS WESTERN
WASHINGTON THIS MORNING, WITH THE COLD FRONT SITUATED OFFSHORE AND
THE LOW PRESSURE CENTER JUST OFF CENTRAL VANCOUVER ISLAND. THIS
LOW WILL CONTINUE TO WORK ITS WAY NORTHEAST INTO BRITISH COLUMBIA,
AS SUCH, IT WILL SLOWLY DRAG THE COLD FRONT ONSHORE. RAIN WILL
CONTINUE INTO TONIGHT, DEVOLVING INTO SCATTERED SHOWERS LATE
TONIGHT INTO THURSDAY MORNING. SHOWERS WILL CONTINUE THROUGHOUT
THE DAY ON THURSDAY. INCREASING INSTABILITY WITH THE UPPER LEVEL
TROUGH AXIS OVERHEAD THURSDAY AFTERNOON WILL PROMOTE THE CHANCE
FOR SCATTERED THUNDERSTORMS. THE BEST CHANCES WILL BE ACROSS
SOUTHWESTERN WASHINGTON, WITH PEAK CAPE VALUES REACHING AROUND
200-300 J/KG, ENOUGH FOR A FEW ISOLATED LIGHTNING STRIKES.
SNOW LEVELS WILL INITIALLY BEGIN FAIRLY HIGH TODAY (AROUND 3500
TO 4000 FT) BEFORE DECREASING TONIGHT, REACHING AROUND 1000 TO
1500 FT ON THURSDAY. SHOWERS MAY ALLOW FOR BRIEF PERIODS OF LIGHT
ACCUMULATING SNOW ACROSS THE CASCADE FOOTHILLS AND HIGHER-
ELEVATION MOUNTAIN VALLEYS, THE WILLAPA AND BLACK HILLS, AS WELL
AS THE HIGHER ELEVATIONS OF THE NORTHWESTERN OLYMPIC PENINSULA,
ESPECIALLY IN THE OVERNIGHT THURSDAY INTO FRIDAY MORNING TIME
RANGE. AT THE PASSES THROUGH THURSDAY NIGHT, SNOWFALL AMOUNTS LOOK
TO REACH AROUND 5 TO 8 INCHES OF SNOW, FOR WHICH A WINTER WEATHER
ADVISORY HAS BEEN ISSUED THROUGH THURSDAY MORNING. HIGHER AMOUNTS
WILL BE FOCUSED TO THE HIGHER ELEVATION ABOVE 5000 FT.
THERE WON'T BE MUCH OF A BREAK IN THE PRECIPITATION THURSDAY
NIGHT BEFORE THE NEXT SYSTEM MOVES INTO THE AREA FROM THE
SOUTHWEST FRIDAY MORNING, MAKING FOR ANOTHER ROUND OF RAIN AND
MOUNTAIN SNOW THROUGHOUT THE DAY ON FRIDAY. SNOW LEVELS WILL BEGIN
TO RISE BACK UP TO 2000 TO 2500 FT.
OVERALL, TEMPERATURES WILL BELOW NORMAL. HIGH TEMPERATURES WILL
BE IN THE MID 40S TO LOW 50S. WITH THE COOLER AIRMASS OVERHEAD
THURSDAY AND FRIDAY, LOW TEMPERATURES WILL BE COOL WITH LOWS
SOLIDLY IN THE 30S. FRIDAY MORNING LOOKS TO BE THE COLDEST MORNING
WITH MUCH OF THE CASCADE AND OLYMPIC FOOTHILLS, AS WELL AS
PORTIONS OF THE SOUTHWEST INTERIOR NEAR OR BELOW FREEZING.
LONG TERM /SATURDAY THROUGH TUESDAY/
A SERIES OF STRONGER AND
MORE MOIST SYSTEMS WILL MOVE THROUGH THE AREA SATURDAY AND SUNDAY
BRINGING MORE SIGNIFICANT RAINFALL, HEAVY MOUNTAIN SNOW, AND
GUSTY WINDS. SNOW LEVELS WILL RETURN TO AROUND 3000 FT WITH ALL
CASCADE PASSES AT PLAY.
PRECIPITATION LOOKS TO TAPER OFF ON MONDAY AS AN UPPER LEVEL
TROUGH MOVES ACROSS THE REGION, WITH A RIDGE BUILDING IN ON
TUESDAY, POTENTIALLY SIGNALING A DRY PERIOD EARLY NEXT WEEK.
62
AVIATION
MIXED CONDITIONS THIS MORNING RANGING FROM VFR TO MVFR,
AS RAIN SHOWERS CONTINUE TO MOVE ACROSS WESTERN WASHINGTON THIS
MORNING. OUTSIDE OF THE RAIN SHOWERS, VFR CONDITIONS HAVE BEEN
OBSERVED. EXPECT LOWER CEILINGS AND VISIBILITIES AS RAIN MOVES OVER
THE TERMINALS. POSSIBLE LOCALIZED IFR CONDITIONS REMAIN POSSIBLE
WITH THE HEAVIER BANDS OF RAIN. BREEZY CONDITIONS NORTH OF EVERETT
THIS MORNING AND SHOULD SUBSIDE BY THE AFTERNOON.
KSEA...VFR CONDITIONS CONTINUE WITH ROUNDS OF RAIN BRINGING LIKELY
REDUCTIONS TO MVFR CEILINGS THROUGH THE DAY TODAY. THERE IS GROWING
CONFIDENCE THAT NORTHERLY WINDS WILL IMPACT THE TERMINAL STARTING
AFTER 0Z THURSDAY AND PERSIST THROUGH 10-11Z, WITH SPEEDS OF 4-7 KT.
SURFACE FLOW WILL THEN SHIFT SOUTHWESTERLY AND WINDS WILL INCREASE
TO 10-15 KT. HIGH-RESOLUTION GUIDANCE HINTS AT POTENTIALLY SEEING
GUSTS GREATER THAN 20 KT (60-80% PROBABILITY).
MARINE
THE FRONT HAS MOVED ON SHORE AND WILL CONTINUE TO SLIDE
ACROSS THE REGION TODAY AS THE NEXT LOW SLIDES NEAR THE COASTAL
WATERS. EXPECT CONTINUED WINDS NEAR ADVISORY CRITERIA THROUGH THE
MORNING, EASING THROUGH THE DAY. COMBINED SEAS OF 9 TO 13 FT,
LARGEST OVER THE OUTER WATERS, AND REMAINING CHOPPY WITH DOMINANT
PERIODS AROUND 9 SECONDS. A STRONGER FRONT WILL BRING ANOTHER ROUND
OF LIKELY SCA CONDITIONS LATER IN THE WEEK BEFORE A DEEPER LOW COULD
BRING A RETURN OF GALES BY THE END OF THE WEEKEND. THESE LATE WEEK
AND WEEKEND SYSTEMS WILL BRING THE SEAS OVER THE COASTAL WATERS
ABOVE 15 FT.
HYDROLOGY
NO RIVER FLOODING IS EXPECTED OVER THE NEXT 7 DAYS.
THE SKOKOMISH RIVER WILL FLUX IN AND OUT OF ACTION STAGE WITH EACH
PASSING SYSTEM THROUGH THE WEEK BUT IS PRESENTLY NOT FORECAST TO
FLOOD.
SEW WATCHES/WARNINGS/ADVISORIES
WA...WINTER WEATHER ADVISORY UNTIL NOON PDT THURSDAY FOR WEST SLOPES
NORTH CASCADES AND PASSES-WEST SLOPES NORTH CENTRAL
CASCADES AND PASSES.
PZ...SMALL CRAFT ADVISORY UNTIL 3 AM PDT THURSDAY 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-WEST ENTRANCE U.S. WATERS STRAIT OF
JUAN DE FUCA.
SMALL CRAFT ADVISORY UNTIL 2 PM PDT THIS AFTERNOON FOR ADMIRALTY
INLET-EAST ENTRANCE U.S. WATERS STRAIT OF JUAN DE FUCA-
NORTHERN INLAND WATERS INCLUDING THE SAN JUAN ISLANDS.
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