449
FXUS66 KSEW 130330
AFDSEW
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SEATTLE WA
830 PM PDT WED MAR 12 2025
UPDATE
SATELLITE IMAGERY AND DOPPLER RADAR SHOW NEXT BATCH OF
MOISTURE TO MOVE INTO THE AREA REACHING THE SOUTHWEST INTERIOR AT
8 PM/03Z. PORTLAND HAS RECORDED 0.20 INCHES OF RAIN IN THE LAST
THREE HOURS. THIS FEATURE WILL CONTINUE TO MOVE NORTH NORTHEAST
INTO THE REMAINDER OF WESTERN WASHINGTON OVERNIGHT INTO THURSDAY
MORNING. CURRENT FORECAST ON TRACK. WILL UPDATE THE WINTER WEATHER
ADVISORY FOR THE CASCADES AND MENTION THE HEAVIEST SNOW BETWEEN 2
AM AND 8 AM THURSDAY. PREVIOUS DISCUSSION FOLLOWS WITH UPDATED
AVIATION SECTION. FELTON
SYNOPSIS
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 /TONIGHT THROUGH SATURDAY/
MOIST, S/SW DIFFLUENT FLOW
IS OVER WESTERN WA AS A TROUGH DIGS OFFSHORE. WE'RE SEEING OFF-
AND-ON SHOWERS WITH SNOW IN THE MOUNTAINS. SNOW LEVELS WILL HOVER
AROUND 4000 FT THIS AFTERNOON, THEN DROP TO AROUND 1500-2000 FT
BY THURSDAY MORNING. THE CASCADES AND PASSES WILL SEE ACCUMULATING
SNOW WITH A BATCH OF HEAVIER PRECIPITATION MOVING IN TONIGHT INTO
EARLY THURSDAY.
THE AIR MASS WILL REMAIN COOL AND SHOWERY ON THURSDAY AS A TROUGH
MOVES INLAND. TEMPS WILL BE CHILLY WITH MORNING LOWS IN THE 30S
AND HIGHS IN THE 40S. THE AIR MASS IS SLIGHTLY UNSTABLE IN
SW WA WHERE THERE'S A CHANCE OF AFTERNOON THUNDERSTORMS.
MORE COOL AND WET WEATHER IS ON TAP FOR FRIDAY AS ANOTHER SHORT
WAVE TROUGH TRACKS THROUGH. THE BULK OF THE ENERGY AND MOISTURE IS
TO OUR SOUTH WITH MAINLY LIGHT SNOWFALL ACCUMULATIONS EXPECTED IN
THE MOUNTAINS. TEMPS ARE STILL TRACKING COOLER THAN AVERAGE WITH
LOWS IN THE LOWER TO MID 30S AND HIGHS MOSTLY IN THE 40S.
A STEADIER STREAM OF MOISTURE IS AIMED AT WA THIS WEEKEND WITH THE
JET OVERHEAD. GOOD OROGRAPHICS INDICATED IN THE MODELS FOR ANOTHER
ROUND OF POTENTIALLY HEAVY SNOW IN THE MOUNTAINS. MAY ALSO SEE
WINDY/BREEZY CONDITIONS WITH THE SURFACE LOW, ESPECIALLY ALONG THE
COAST. 33
LONG TERM /SUNDAY THROUGH WEDNESDAY/
ACTIVE WEATHER CONTINUES
ON SUNDAY WITH MORE RAIN, MOUNTAIN SNOW AND BREEZY/WINDY
CONDITIONS. HEAVY SNOW IS STILL EXPECTED IN THE CASCADES WHERE
STORM TOTAL SNOW AMOUNTS COULD TOTAL UP TO 2 FEET. HEAVY
PRECIPITATION IN THE OLYMPICS MAY ALSO DRIVE THE SKOKOMISH RIVER
IN MASON COUNTY INTO FLOOD STAGE. THE MOISTURE PLUME GETS CUT OFF
SUNDAY NIGHT AS A TROUGH MOVES IN (PUSHING THE BAND TOWARD OUR
SOUTH). THIS WOULD END THE HEAVY PRECIP THREAT FOR BOTH LOWLANDS
AND MOUNTAINS. MONDAY WILL SEE ADDITIONAL SHOWERS WITH TROUGHING
OVER THE WEST. ENSEMBLE MEMBERS SHOW A DRIER PERIOD MOVING TOWARD
MIDWEEK AS A RIDGE MOVES IN. 33
AVIATION
CEILINGS HAVE LOWERED THIS EVENING INTO MVFR AS MORE
ABUNDANT CLOUD COVER AND MORE RAIN SHOWERS PUSH THROUGH THE REGION.
LOCALIZED IFR IS POSSIBLE IN HEAVIER BANDS OF RAIN. WINDS ARE
BEGINNING TO SHIFT NORTHERLY/NORTHWESTERLY AS THE FRONT NEARS AND
WILL STAY NORTHERLY UNTIL AROUND 10Z-12Z. WINDS WILL THEN SHIFT
SOUTHWESTERLY BETWEEN 10-12Z AND INCREASE IN SPEED, PRIMARILY ALONG
PUGET SOUND TERMINALS AND THE STRAIT OF JUAN DE FUCA (KCLM), WITH
SPEEDS OF 10-15 KT AND GUSTS UP TO 20-25 KT.
KSEA...RAIN AND MVFR TONIGHT AS LOWER CLOUDS AND MORE RAIN PUSH
NORTH FROM THE SOUTH. WINDS ARE SLOWING TURNING AROUND AND COMING
OUT OF THE WNW AND WILL RANGE BETWEEN 5 AND 8 KTS. THIS WILL LAST
UNTIL AROUND 10Z TO 12Z BEFORE SOUTHWESTERLY FLOW RESUMES.
SOUTHWESTERLY FLOW AND INCREASED WIND SPEEDS TO 10-15 KT. HIGH-
RESOLUTION GUIDANCE HINTS AT POTENTIALLY SEEING GUSTS ABOVE 20 KT
(60-80% CHANCE). WINDS WILL GRADUALLY EASE INTO THE AFTERNOON HOURS
ON THURSDAY.
29/21
MARINE
WINDS HAVE EASED OVER THE COASTAL WATERS AND INTERIOR
WATERS. HOWEVER, A SMALL CRAFT ADVISORY STILL REMAINS IN EFFECT FOR
WAVES BETWEEN 8 TO 10 FEET WITH WITH A SHORT DURATION PERIOD OF 8
SECONDS, WITH THE LARGEST WAVES OVER THE OUTER WATERS. MARINE
CONDITIONS WILL EASE THURSDAY AND FRIDAY, BEFORE STRONGER SYSTEMS
TRAVERSE THE WATERS THIS WEEKEND, POTENTIALLY BRINGING GALES AND
SEAS ABOVE 15 FEET OVER THE COASTAL WATERS.
29
MARINE
WINDS HAVE EASED OVER THE COASTAL WATERS AND INTERIOR
WATERS. HOWEVER, A SMALL CRAFT ADVISORY STILL REMAINS IN EFFECT FOR
WAVES BETWEEN 8 TO 10 FEET WITH WITH A SHORT DURATION PERIOD OF 8
SECONDS, WITH THE LARGEST WAVES OVER THE OUTER WATERS. MARINE
CONDITIONS WILL EASE THURSDAY AND FRIDAY, BEFORE STRONGER SYSTEMS
TRAVERSE THE WATERS THIS WEEKEND, POTENTIALLY BRINGING GALES AND
SEAS ABOVE 15 FEET OVER THE COASTAL WATERS.
29
HYDROLOGY
HEAVY PRECIPITATION IN THE SOUTHERN OLYMPICS THIS
WEEKEND WILL FORCE SHARP RISES ON THE SKOKOMISH RIVER WITH
FLOODING POSSIBLE. A HYDROLOGIC OUTLOOK HAS BEEN ISSUED. RIVER
FLOODING IS NOT EXPECTED ELSEWHERE OVER THE NEXT 7 DAYS.
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-WEST SLOPES SOUTH 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.
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