215
FXUS66 KSEW 121115
AFDSEW
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SEATTLE WA
415 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/
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 BAG OF LOW VFR AND MVFR CONDITIONS WITH
THE LOWEST CEILINGS ALONG THE COASTAL AREAS WHERE THE RAIN REMAINS
HEAVIEST. EXPECT LITTLE CHANGE FOR THE NEXT FEW HOURS WITH RAIN
BANDS BRINGING MORE WIDESPREAD MVFR AND LOCAL IFR CONDITIONS AS THEY
PIVOT ACROSS WESTERN WASHINGTON THROUGH THE DAY. WINDS WILL REMAIN
GUSTY NEAR THE COAST, BUT OTHERWISE RATHER CONSISTENT THROUGH THE
DAY.
KSEA...VFR CONDITIONS CONTINUE WITH ROUNDS OF RAIN BRINGING LIKELY
REDUCTIONS TO MVFR CEILINGS THROUGH THE DAY TODAY. SOUTHEAST SURFACE
WINDS WILL CONTINUE THROUGH THE DAY, SHIFTING TO SOUTHWESTERLY
BEHIND THE FRONT THIS AFTERNOON.
MARINE
A FRONT REMAINS STALLED JUST OFFSHORE AND WILL 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. IN ADDITION, SEAS WILL CONTINUE TO
BUILD TO 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...NONE.
PZ...SMALL CRAFT ADVISORY UNTIL 11 AM PDT THIS MORNING FOR WEST
ENTRANCE U.S. WATERS STRAIT OF JUAN DE FUCA.
SMALL CRAFT ADVISORY UNTIL 1 PM PDT THIS AFTERNOON FOR ADMIRALTY
INLET-EAST ENTRANCE U.S. WATERS STRAIT OF JUAN DE FUCA.
SMALL CRAFT ADVISORY UNTIL 2 PM PDT THIS AFTERNOON 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-NORTHERN INLAND WATERS
INCLUDING THE SAN JUAN ISLANDS.
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