343
FXUS66 KSEW 210451 CCA
AFDSEW
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SEATTLE WA
851 PM PST FRI DEC 20 2024
SYNOPSIS
A SERIES OF FRONTS WILL BRING SEVERAL ROUNDS OF LIGHT
PRECIPITATION INTO TOMORROW, WITH BREEZY WINDS AND SLIGHTLY
WARMER TEMPERATURES. A MORE ACTIVE PATTERN IS SET TO EVOLVE AND
TAKE SHAPE THIS WEEKEND AND LAST INTO NEXT WEEK, WITH AN INCREASED
CHANCE OF IMPACTFUL WEATHER ARRIVING DURING THE HOLIDAYS.
SHORT TERM /TONIGHT THROUGH MONDAY/
WESTERN WASHINGTON IS
BETWEEN WEATHER SYSTEMS THIS EVENING AS THE NEXT ONE POISED OFFSHORE
LIFTS NORTHEASTWARD TOWARD THE AREA. OFFSHORE GRADIENTS WILL TIGHTEN
UP AHEAD OF IT AND A WIND ADVISORY REMAINS IN EFFECT FOR THE EAST
PUGET SOUND LOWLANDS OVERNIGHT. COASTAL AREAS MAY FLIRT WITH WIND
ADVISORY CRITERIA SATURDAY MORNING AS MODELS SHOW A STRONG SOUTHERLY
SURGE REACHING THE COAST AS AN OCCLUSION PUSHES ONSHORE. QPF WITH
SATURDAY'S SYSTEM LOOKS RATHER LIGHT WITH RAIN REACHING THE COAST
EARLY A.M. AND SPREADING INTO THE INTERIOR BY LUNCHTIME THEN QUICKLY
TRANSITIONING TO A FEW SHOWERS. QPF WITH THE FRONT ON SUNDAY LOOKS A
BIT MORE GENEROUS, BUT TYPICAL FOR AN EARLY WINTER FRONT. OVERALL
FORECAST PACKAGE LOOKS IN GOOD SHAPE THIS EVENING WITH NO
SIGNIFICANT UPDATES ANTICIPATED. PREVIOUS DISCUSSION FOLLOWS WITH
UPDATES TO MARINE/AVIATION PORTIONS. 27
AN ACTIVE WEATHER PATTERN CONTINUES ACROSS THE PAC NW AS A SERIES OF
STORMS TRACK THROUGH THE REGION. WE'RE SEEING SOME LIGHT WARM
FRONTAL PRECIPITATION ACROSS WESTERN WA TODAY AND THE TRAILING COLD
FRONT WILL MOVE INLAND TONIGHT. PRESSURE GRADIENTS WILL TIGHTEN
ACROSS THE CASCADES WITH GUSTY EAST WINDS EXPECTED BELOW THE GAPS
(LIKE IN NORTH BEND) - A WIND ADVISORY IS IN EFFECT THROUGH EARLY
SATURDAY MORNING.
WE'LL SEE A BRIEF BREAK IN THE WEATHER SATURDAY MORNING, THEN
MORE RAIN AND BREEZY WINDS SATURDAY AFTERNOON AND EVENING AS THE
NEXT SYSTEM ARRIVES. WINDS WILL BE STRONGEST OVER THE NORTH
COAST. SNOW LEVELS WILL BE LOWERING TO AROUND 4000 FT SATURDAY
NIGHT WITH AN INCH (OR TWO) OF NEW SNOW IN THE HIGHER CASCADE
PASSES LIKE STEVENS PASS AND WHITE PASS.
MORE WET WEATHER IS HEADED OUR WAY ON SUNDAY AND MONDAY, WITH
LITTLE BREAK IN THE ACTION. GUSTY E/SE WINDS ALSO EXPECTED ALONG
THE COAST. SNOW LEVELS HOVER AROUND 4000 FT IN THE CASCADES WITH
A FEW MORE INCHES OF SNOW OVER THE HIGHER PEAKS AND PASSES. 33
LONG TERM /TUESDAY THROUGH FRIDAY/
MORE ACTIVE WEATHER THROUGH
THE WEEK AHEAD AS STORM AFTER STORM BARRELS THROUGH THE PAC NW.
MAIN CONCERNS WILL BE ONGOING LOWLAND RAIN, BREEZY TO WINDY
CONDITIONS, AND POTENTIAL FOR HEAVY MOUNTAIN SNOW. TEMPERATURES
THROUGHOUT THE PERIOD WILL STAY ABOVE FREEZING WITH LOWS IN THE
40S AND HIGHS NEAR 50. THE AIR MASS WILL BE COOLER ON CHRISTMAS
DAY WITH SNOW LEVELS DOWN TO 3000 FT. SNOW IN THE MOUNTAINS MAY
IMPACT ALL CASCADE PASSES. 33
AVIATION
FRONT MOVING INTO THE AREA FROM THE SOUTHWEST
LATE SATURDAY MORNING INTO SATURDAY AFTERNOON. SOUTHERLY FLOW
ALOFT WITH LOW LEVEL OFFSHORE.
VFR CEILINGS LOWERING TO MVFR ALONG THE COAST SATURDAY MORNING.
CEILINGS LOWERING OVER THE INTERIOR IN THE AFTERNOON TO LOW END
VFR OR HIGH END MVFR. PATCHY FOG ALONG THE STRAIT OF JUAN DE FUCA,
KITSAP PENINSULA AND THE SOUTHWEST INTERIOR LOWERING VISIBILITY TO
A MILE OR LESS UNTIL 11Z.
KSEA...VFR CEILINGS LOWERING TO NEAR 3000 FEET 21Z-00Z AND
REMAINING NEAR 3000 FEET THROUGH SATURDAY EVENING. EAST NORTHEAST
WINDS 4 TO 8 KNOTS BECOMING EAST SOUTHEAST 8 TO 12 KNOTS AROUND
15Z AND SOUTHERLY 8 TO 12 KNOTS 21Z-00Z. FELTON
MARINE
A SERIES OF FRONTS WILL CROSS THE REGION OVER THE NEXT
SEVERAL DAYS, MAINTAINING SEAS ABOVE 10 FEET AND PERIODS OF BREEZY
CONDITIONS THROUGH THE WEEKEND AND INTO NEXT WEEK. A SMALL CRAFT
ADVISORY REMAINS IN EFFECT FOR THE COASTAL WATERS FOR INCREASED
SOUTHERLY WINDS AND ELEVATED SEAS. ANOTHER FRONT WILL MOVE THROUGH
THE COASTAL WATERS BY SATURDAY MORNING, PROMPTING THE UPGRADE FROM
THE GALE WATCH TO A GALE WARNING
COMBINED SEAS THIS AFTERNOON 9 TO 12 FEET. SEAS WILL THEN BEGIN TO
BUILD UPWARDS TO 15 TO 20 FEET ON SATURDAY AND REMAIN ELEVATED
THROUGH SUNDAY WITH LONG PERIOD SWELL. SEAS WILL ONCE AGAIN GROW
ON MONDAY AROUND 18 TO 22 FEET, AS THESE HIGH SEAS LOOK TO
MAINTAIN THROUGH THE MIDDLE OF NEXT WEEK.
MAZURKIEWICZ
HYDROLOGY
A SERIES OF DISTURBANCES OVER THE WEEKEND WITH
ADDITIONAL ROUNDS OF PRECIPITATION. FLOODING IS NOT LIKELY BUT
MINOR RISES ON AREA RIVERS EXPECTED. THE SKOKOMISH RIVER WILL
CONTINUE TO RECEDE SLOWLY DROPPING JUST BELOW FLOOD STAGE
OVERNIGHT THEN REMAIN NEAR FLOOD STAGE THROUGH THE WEEKEND INTO
NEXT WEEK. INCREASING PRECIPITATION AROUND CHRISTMAS COULD PUSH
THE SKOKOMISH BACK UP TO MODERATE FLOOD STAGE. FOR THE REMAINING
RIVERS, THE THREAT OF FLOODING WILL ALSO INCREASE IN THE MIDDLE
OF NEXT WEEK AS ENSEMBLES CONTINUE TO INDICATE THE POTENTIAL FOR
SIGNIFICANT PRECIPITATION. WHILE DISCREPANCIES REMAIN, THIS MOST
LIKELY WILL LEAD TO AN INCREASED CHANCE OF RIVER FLOODING BECOMING
MORE WIDESPREAD AND LANDSLIDE CONCERNS THAT MAY IMPACT HOLIDAY
TRAVEL.
MCMILLIAN/FELTON
SEW WATCHES/WARNINGS/ADVISORIES
WA...WIND ADVISORY FROM 1 AM TO 7 AM PST SATURDAY FOR EAST PUGET
SOUND LOWLANDS.
PZ...SMALL CRAFT ADVISORY FROM 6 AM SATURDAY TO 1 PM PST SUNDAY FOR
GRAYS HARBOR BAR.
SMALL CRAFT ADVISORY FROM 1 AM TO 10 AM PST SATURDAY FOR WEST
ENTRANCE U.S. WATERS STRAIT OF JUAN DE FUCA.
SMALL CRAFT ADVISORY UNTIL 4 AM PST SATURDAY 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.
GALE WARNING FROM 4 AM TO 4 PM PST SATURDAY 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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