756
FXUS66 KSEW 191109
AFDSEW
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SEATTLE WA
309 AM PST THU DEC 19 2024
SYNOPSIS
A SERIES OF WEAK FRONTS WILL BRING SEVERAL ROUNDS OF
LIGHT PRECIPITATION THROUGH THE REST OF THE WEEK, PAIRED WITH
BREEZY WINDS AND WARMER TEMPERATURES. A MORE ACTIVE PATTERN WILL
DEVELOP THIS WEEKEND AND INTO NEXT WEEK, WITH AN INCREASED RISK OF
IMPACTFUL WEATHER DURING THE HOLIDAY.
SHORT TERM /TODAY THROUGH SATURDAY/
SHOWERS WILL CONTINUE TO
SPREAD INLAND EARLY THIS MORNING AS A WARM FRONT SWEEPS ACROSS
WESTERN WASHINGTON. MUCH OF THE REGION WILL SEE LITTLE MORE THAN A
DRIZZLE THIS MORNING, WITH MOST OF THE MEASURABLE RAIN FALLING
OVER THE OLYMPIC PENINSULA. THE MOST NOTABLE FEATURE OF THIS WARM
FRONTAL PASSAGE WILL BE BREEZY WINDS, WHERE GUSTS ALONG THE COAST
COULD REACH 35 TO 40 MPH INTO THE EARLY AFTERNOON. A TRAILING
COLD FRONT WILL MOVE INLAND LATER THIS AFTERNOON, BRINGING IN A
HEAVIER BAND OF PRECIPITATION WITH SNOW LEVELS WELL ABOVE PASS
LEVEL. RAINFALL TOTALS THROUGHOUT THE DAY WILL BE LIGHT, WITH UP
TO A TENTH OR TWO FOR THE INTERIOR LOWLANDS, AND UP TO A HALF OF
AN INCH TO AN INCH OVER THE OLYMPIC PENINSULA AND NORTH CASCADES.
TEMPERATURES WILL PEAK SEVERAL DEGREES ABOVE NORMAL, IN THE MID
50S ACROSS THE LOWLANDS.
FRIDAY IS ON TRACK TO BE THE DRIEST DAY OF THE PERIOD, THOUGH A
CHANCE OF SHOWERS IS MAINTAINED IN THE FORECAST MAINLY OVER HIGHER
TERRAIN. WEAK HIGH PRESSURE WILL BUILD OVERHEAD LATE THURSDAY INTO
FRIDAY MORNING, WITH ANOTHER WEAK WARM FRONT AND TRAILING COLD
FRONT ON TRACK TO BRING ANOTHER ROUND OF BREEZY WINDS AND LIGHT
RAINFALL TO WESTERN WASHINGTON THROUGHOUT THE DAY FRIDAY. FORECAST
MODELS SHOW THIS SYSTEM GRAZING THE OLYMPIC PENINSULA, WITH UP TO
A TENTH OR TWO THROUGHOUT THE DAY AND LITTLE MORE THAN A TRACE
ELSEWHERE. SOUTHERLY FLOW ALOFT WILL MAINTAIN WARM TEMPERATURES
WITH A DEGREE OR TWO OF WARMING, ALLOWING FOR ANOTHER DAY IN THE
MID 50S FOR THE LOWLANDS.
SATURDAY WILL PROVIDE A SIMILAR STORY, THOUGH THIS SYSTEM WILL BE
SLIGHTLY STRONGER. A WAVE OF MORE WIDESPREAD RAINFALL AND BREEZY
WINDS WILL MOVE NORTHWARD ACROSS WESTERN WASHINGTON SATURDAY
AFTERNOON AS A TROUGH LIFTS ACROSS THE REGION. SNOW LEVELS WILL
DROP TO 3500-4000 FT BY SATURDAY EVENING, THOUGH ANY SNOW
ACCUMULATIONS THROUGH THE CASCADE PASSES WILL BE MINIMAL. RAINFALL
AMOUNTS WILL INCREASE WITH THIS SYSTEM, WITH UP TO HALF AN INCH
FOR MOST AREAS AND UP TO AN INCH OR MORE OVER THE OLYMPIC
MOUNTAINS. THIS STORM SYSTEM ALSO HAS HIGHER POTENTIAL TO BRING
ANOTHER ROUND OF GUSTY WINDS TO THE REGION, AND THE POTENTIAL FOR
STRONG WINDS PARTICULARLY ALONG THE COAST CONTINUES TO BE
MONITORED FOR SATURDAY. THE ADDITIONAL RAINFALL THROUGH SATURDAY
WILL ALSO MAINTAIN ELEVATED RIVER FLOWS ACROSS THE REGION, BUT
RIVER FLOODING IS EXPECTED TO BE LIMITED TO THE SKOKOMISH RIVER.
LONG TERM /SUNDAY THROUGH WEDNESDAY/
ACTIVE WEATHER WILL
CONTINUE INTO THE EXTENDED FORECAST PERIOD, WITH EACH SUBSEQUENT
SYSTEM GROWING IN STRENGTH AND BRINGING CASCADING IMPACTS TO THE
REGION. ENSEMBLES CONTINUE TO SHOW POTENTIAL FOR ROUNDS OF STRONG
WINDS AND PERIODS OF MODERATE TO HEAVY RAINFALL SUNDAY AND BEYOND,
WITH PERIODS OF ACCUMULATING MOUNTAIN SNOW THROUGH THE CASCADE
PASSES TUESDAY AND BEYOND. THESE ADDITIONAL STORM SYSTEMS WILL
GRADUALLY INCREASE IN STRENGTH, INCREASING THE RISK OF RIVER
FLOODING AND LANDSLIDE. LONG RANGE MODELS ALSO CONTINUE TO SHOW
POTENTIAL FOR HAZARDOUS WEATHER CONDITIONS THAT MAY IMPACT TRAVEL
MID-WEEK AND BEYOND, DEPENDING ON HOW THE FORECAST TRENDS AS
THINGS GET CLOSER.
LINDEMAN
AVIATION
A QUICK UPPER LEVEL RIDGE HAS SHIFTED INLAND THIS
MORNING. THIS WILL BE FOLLOWED BY A SHORTWAVE TROUGH PUSHING
NORTHEAST TOWARDS THE WASHINGTON COAST TODAY (CREATING SOUTHWEST
FLOW ALOFT). OVERCAST SKIES OVERNIGHT ARE KEEPING A MAJORITY OF
TERMINALS VFR (WITH A COUPLE SPOTS WEST OF PUGET SOUND REPORTING
MVFR CIGS). OCCASIONAL PATCHY FOG WILL CONTINUE IN THE SOUTH
INTERIOR AT TIMES UNTIL DUSK, BUT THIS WILL REMAIN ISOLATED IN
NATURE. CEILINGS WILL REMAIN VFR FOR MOST OF THURSDAY, BEFORE
DROPPING TO MVFR TONIGHT INTO FRIDAY EARLY MORNING.
AN APPROACHING SURFACE SYSTEM WITH TWO FRONTS WILL SWING THROUGH
THIS AFTERNOON. RADAR SHOWS RAIN SHOWERS IN PROGRESS ALONG THE COAST
AND OVER THE PACIFIC OCEAN. THE INITIAL WARM FRONT WILL BRING
ISOLATED TO SCATTERED SHOWERS TO TERMINALS AROUND AND NORTH OF PUGET
SOUND THIS MORNING. THE SECOND COLD FRONT IS EXPECTED TO BRING A
MORE ORGANIZED LINE OF RAIN LATER THIS AFTERNOON AND EVENING.
WIDESPREAD CONVECTION IS NOT EXPECTED, BUT VARIABLE WINDS & WIND
DIRECTIONS WILL BE POSSIBLE IF ANY CONVECTION DOES TAKE PLACE WITHIN
THE LINE (ALONG WITH VISIBILITY DROPS). WIND SHEAR IS NOT EXPECTED
TO BE AS STRONG (COMPARED TO YESTERDAY). MOST OF THE SHOWER ACTIVITY
WILL WRAP UP AROUND 08Z FRIDAY MORNING. WINDS WILL BE SIGNIFICANTLY
LESS (COMPARED TO WEDNESDAY), WITH PEAK GUSTS OF 25 TO 30 KT
EXPECTED AT TERMINALS ALONG THE COAST (AND IN THE NORTHWEST
INTERIOR). REMAINING LOWLAND AREAS WILL NOT LIKELY SEE WIND GUSTS
EXCEED 15 TO 20 KT TODAY. MOST OF THESE WINDS WILL BLOW OUT OF THE
SOUTH (SOME POSSIBILITY FOR EAST WINDS BELOW 6 KT UNTIL EARLY
AFTERNOON).
KSEA...TERMINAL IS REPORTING VFR THIS MORNING. SPOTTY SHOWERS ARE
POSSIBLE BETWEEN 17Z-21Z THIS MORNING. A MORE ORGANIZED AREA OF
PRECIPITATION WILL ARRIVE AFTER 22Z THURSDAY AFTERNOON, AND MOVE OUT
BY 03Z FRIDAY. CONVECTION IS NOT EXPECTED. CEILINGS WILL REMAIN VFR
TROUGH THE DAY TODAY, WITH A DROP TO MVFR GENERALLY EXPECTED AFTER
03Z THIS EVENING THROUGH 15Z FRIDAY. WINDS WILL REMAIN OUT OF THE
SOUTH AT OR BELOW 06 KT.
HPR
MARINE
WESTERN WASHINGTON EARLY THIS MORNING SITS IN BETWEEN TWO
SURFACE LOWS, WITH BRIEF HIGH PRESSURE PASSING OVER US EARLY THIS
MORNING WITH THE NEXT SYSTEM ALREADY ON SHORT APPROACH. THE NEXT
SURFACE FRONTAL SYSTEM WILL PRODUCE AREAS OF PRECIPITATION (EXPECTED
TO BE LIGHTER OVERALL COMPARED TO WEDNESDAY). GUSTY WINDS WILL ALSO
PICK BACK UP LATER TODAY INTO THE AFTERNOON. CONFIDENCE INCREASED ON
THE PROBABILITY OF GALES IN THE OUTER COASTAL WATERS (UPGRADED THE
SMALL CRAFT TO A GALE WARNING). ANOTHER AREA OF BLUSTERY SOUTH WINDS
(EXPECTED TO GIVE SMALL CRAFT ISSUES) EXISTS IN THE EAST STRAIT OF
JUAN DE FUCA, ADMIRALTY INLET, AND THE NORTHERN INLAND WATERS. MORE
SYSTEMS ARE EXPECTED TO IMPACT THE REGION, BEGINNING THIS WEEKEND
AND CONTINUING FOR A GOOD CHUNK OF NEXT WEEK.
SEAS WILL REMAIN AT OR ABOVE 10 FEET THROUGH THE FORECAST, AND WILL
APPROACH AT OR ABOVE 20 FEET LATE THIS WEEKEND INTO NEXT WEEK.
HPR
HYDROLOGY
RIVERS WILL CONTINUE TO RECEDE THIS MORNING, WITH THE
SKOKOMISH RIVER BEING THE ONLY RIVER REMAINING IN FLOOD STAGE
THURSDAY. THE CHEHALIS RIVER AT GRAND MOUND HAS CRESTED BELOW
FLOOD STAGE EARLY THIS MORNING AND WILL CONTINUE TO SLOWLY RECEDE
THIS MORNING. THE CHEHALIS RIVER AT PORTER WILL LIKELY FOLLOW
CLOSE BEHIND, CRESTING BELOW FLOOD STAGE LATER THIS MORNING.
ADDITIONAL INCOMING PRECIPITATION LATER THIS WEEK AND INTO NEXT
WEEK WILL MAINTAIN THE THREAT OF RIVER FLOODING ACROSS WESTERN
WASHINGTON, BUT MODELS CONTINUE TO SHOW LARGE DISCREPANCIES AND
THE FORECAST REMAINS UNCERTAIN AT THIS TIME. ENSEMBLES SHOW
POTENTIAL FOR SIGNIFICANT PRECIPITATION TO RETURN BY NEXT WEEK,
WHICH MAY CAUSE ELEVATED RIVER FLOODING AND LANDSLIDE CONCERNS
THAT MAY IMPACT HOLIDAY TRAVEL.
15
SEW WATCHES/WARNINGS/ADVISORIES
WA...FLOOD WATCH THROUGH THIS AFTERNOON FOR SOUTHWEST INTERIOR.
FLOOD WATCH THROUGH LATE TONIGHT FOR CENTRAL COAST-LOWER
CHEHALIS VALLEY AREA-OLYMPICS.
PZ...SMALL CRAFT ADVISORY UNTIL 8 PM PST THIS EVENING FOR COASTAL
WATERS FROM CAPE FLATTERY TO JAMES ISLAND OUT 10 NM-COASTAL
WATERS FROM JAMES ISLAND TO POINT GRENVILLE OUT 10 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 FROM 10 AM THIS MORNING TO 11 PM PST THIS
EVENING FOR EAST ENTRANCE U.S. WATERS STRAIT OF JUAN DE
FUCA.
SMALL CRAFT ADVISORY FROM 4 PM THIS AFTERNOON TO 11 PM PST THIS
EVENING FOR ADMIRALTY INLET-NORTHERN INLAND WATERS
INCLUDING THE SAN JUAN ISLANDS.
SMALL CRAFT ADVISORY UNTIL 7 AM PST THIS MORNING FOR COASTAL
WATERS FROM CAPE FLATTERY TO JAMES ISLAND 10 TO 60 NM-
COASTAL WATERS FROM JAMES ISLAND TO POINT GRENVILLE 10 TO
60 NM-COASTAL WATERS FROM POINT GRENVILLE TO CAPE
SHOALWATER 10 TO 60 NM.
SMALL CRAFT ADVISORY FROM 4 PM THIS AFTERNOON TO 8 PM PST THIS
EVENING FOR COASTAL WATERS FROM CAPE FLATTERY TO JAMES
ISLAND 10 TO 60 NM-COASTAL WATERS FROM JAMES ISLAND TO
POINT GRENVILLE 10 TO 60 NM-COASTAL WATERS FROM POINT
GRENVILLE TO CAPE SHOALWATER 10 TO 60 NM.
GALE WARNING FROM 7 AM THIS MORNING TO 4 PM PST THIS AFTERNOON
FOR COASTAL WATERS FROM CAPE FLATTERY TO JAMES ISLAND 10 TO
60 NM-COASTAL WATERS FROM JAMES ISLAND TO POINT GRENVILLE
10 TO 60 NM-COASTAL WATERS FROM POINT GRENVILLE TO CAPE
SHOALWATER 10 TO 60 NM.
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