530
FXUS66 KSEW 190442
AFDSEW
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SEATTLE WA
840 PM PST WED DEC 18 2024
SYNOPSIS
DRIER CONDITIONS TONIGHT AS UPPER-RIDGING BUILDS.
A SYSTEM WILL BRING LIGHTER PRECIPITATION THURSDAY INTO THURSDAY
NIGHT. ADDITIONAL WEAKER FRONTS WILL BRING PRECIPITATION CHANCES
LATE IN THE WEEK. A MORE ACTIVE PATTERN DEVELOPS LATER IN THE
WEEKEND THROUGH NEXT WEEK.
SHORT TERM /TONIGHT THROUGH SATURDAY/
RADAR AND SATELLITE IMAGERY
BOTH LOOKING VASTLY DIFFERENT FROM 24 HOURS AGO, WITH THE RADAR
VITUALLY EMPTY OF ECHOES AND SATELLITE SHOWING HIGH TO MID CLOUDS
OVER MUCH OF THE OLYMPIC PENINSULA AND THE CENTRAL AND SOUTH SOUND
AREAS. SOME RIVERS REMAIN IN FLOOD STAGE THIS EVENING, INCLUDING THE
SKOKOMISH AND THE SATSOP...BOTH OF WHICH HAVE CRESTED AND ARE ON
THEIR WAY DOWN THANKS TO CURRENT DRY CONDITIONS. STILL KEEPING AN
EYE ON THE CHEHALIS AT BOTH GRAND MOUND AND PORTER, WHERE LEVELS
CONTINUE TO RISE...ALTHOUGH CURRENT FORECAST KEEPS BOTH LOCATIONS
JUST A WEE BIT BELOW FLOOD STAGE. THAT SAID, INHERITED FLOOD WATCH
WILL REMAIN UP AND UNALTERED FOR NOW.
THAT SAID, NO PLANNED CHANGES OR UPDATES TO FORECAST AT THIS TIME.
FOR FURTHER FORECAST DETAILS, PLEASE REFER TO THE PREVIOUS
DISCUSSION SECTION BELOW.
18
FROM PREVIOUS DISCUSSION...A CONVERGENCE ZONE OVER SNOHOMISH COUNTY
HAS FIZZLED OUT THIS AFTERNOON. ONSHORE FLOW WILL KEEP SHOWERS IN
THE FORECAST, MAINLY FOR THE MOUNTAINS BUT SHOULD END BY THE
EVENING. DRIER WEATHER TONIGHT HOWEVER IT WON'T BE LONG LASTING
UNTIL THE NEXT DISTURBANCE ARRIVES. CLOUD COVERAGE WILL BE ON THE
INCREASE, KEEPING TEMPERATURES FROM BOTTOMING OUT TOO MUCH.
OVERNIGHT LOWS ARE FORECAST TO BE IN THE LOWER TO MID 40S WITH A FEW
UPPER 30S.
A LOW CENTER IN THE GULF OF ALASKA WILL SWEEP A WARM FRONT INTO
THE AREA ON THURSDAY, REACHING THE COAST BY THE EARLY MORNING
HOURS BEFORE SPREADING INLAND TOWARDS DAYBREAK WITH LIGHT RAIN.
THE ASSOCIATED TRAILING AND DECAYING "COLD" FRONT WILL USHER
ANOTHER ROUND OF PRECIPITATION INTO THE AFTERNOON-EVENING. SNOW
LEVELS WILL BE WELL-ABOVE THE PASSES SO WINTRY PRECIPITATION IS
NOT EXPECTED. BRIEF RIDGING OVERNIGHT THURSDAY INTO FRIDAY BUT AN
ADDITIONAL FRONT WILL ENTER FRIDAY AFTERNOON WITH ANOTHER SHOT OF
LIGHT PRECIPITATION ALONG WITH A VERY SIMILAR STORY INTO SATURDAY.
NO MAJOR IMPACTS ARE EXPECTED FROM THIS NEXT SET OF SYSTEMS
CURRENTLY BUT NEVERTHELESS THE PATTERN LOOKS TO REMAIN ACTIVE.
TEMPERATURES ARE FORECAST TO BE ABOVE-AVERAGE WITH HIGHS IN THE
LOWER TO MID 50S AND OVERNIGHT LOWS IN THE 40S.
LONG TERM /SUNDAY THROUGH WEDNESDAY/...FROM PREVIOUS DISCUSSION
A
STRONGER SYSTEM IS EXPECTED TO APPROACH THE AREA ON SUNDAY WITH THE
POTENTIAL FOR BREEZY WINDS. ENSEMBLES SUGGEST THIS ACTIVE PATTERN
CONTINUES THROUGH AT LEAST THE MIDDLE OF NEXT WEEK, WITH SYSTEMS
ACCOMPANIED BY LOWLAND RAIN, MOUNTAIN SNOWFALL, AND GUSTY WINDS
PARTICULARLY MONDAY INTO TUESDAY. THIS IS HIGHLIGHTED WELL BY THE
CPC WEEK 2 HAZARDS OUTLOOK. TEMPERATURES WILL BE SLIGHTLY COOLER
SATURDAY INTO NEXT WEEK.
MCMILLIAN
AVIATION
TEMPORARY UPPER LEVEL RIDGE OVER THE AREA THIS
EVENING WILL SHIFT EAST OVERNIGHT. WEAKENING WARM FRONT MOVING
THROUGH THURSDAY. NORTHWESTERLY FLOW ALOFT BECOMING SOUTHWESTERLY
AFTER 12Z THURSDAY. LIGHT FLOW OVERNIGHT IN THE LOWER LEVELS
BECOMING OFFSHORE THURSDAY.
HIGH CLOUDS OVER THE AREA THIS EVENING WITH LOCAL MVFR CEILINGS
ALONG THE COAST. PATCHY FOG OVER THE SOUTHWEST INTERIOR REDUCING
VISIBILITY TO A MILE OR LESS UNTIL 10Z. INCREASING CLOUD COVER WITH
WARM FRONT APPROACHING. CEILINGS IN THE 4000-6000 FOOT RANGE
BEGINNING AROUND 12Z AND CONTINUING INTO THE AFTERNOON HOURS FOR THE
INTERIOR. CEILINGS LOWERING ALONG THE COAST TO THE LOW END OF MVFR
WITH POSSIBLE IFR CEILINGS AFTER 00Z.
KSEA...JUST SOME HIGH CLOUDS RIGHT NOW. 2500 FOOT SCATTERED DECK
FLOATING AROUND COULD BRIEFLY GO BROKEN IN THE NEXT COUPLE OF HOURS.
CEILINGS LOWERING TO AROUND 6000 FEET BY 12Z AND TO 4000 FEET BY 18Z
THURSDAY. LIGHT WIND BECOMING EASTERLY 4 TO 8 KNOTS AFTER 09Z. FELTON
MARINE
A BREAK IN THE WEATHER AS THE PREVIOUS WEATHER
SYSTEM PUSHES EASTWARD AWAY FROM OUR AREA. THE NEXT FRONTAL SYSTEM
WILL BE APPROACHING RIGHT BEHIND, PUSHING THROUGH THE COASTAL WATERS
INTO THURSDAY AFTERNOON. SMALL CRAFT SOUTHERLIES CAN BE EXPECTED
ACROSS THE COASTAL WATER ZONES, WITH LATEST GUIDANCE DECREASING THE
INTENSITY OF THESE WINDS, ALTHOUGH CANNOT RULE OUT A GUST UP TO GALE
STRENGTH HERE AND THERE - BUT NOT WIDESPREAD.
ADDITIONAL WEATHER SYSTEMS WILL IMPACT THE WATERS THROUGH THE
WEEKEND AND INTO EARLY NEXT WEEK, WITH MORE CHANCES OF GUSTY WINDS
AND ELEVATED SEAS.
COASTAL SEAS THIS AFTERNOON AROUND 9 TO 12 FEET, WITH SEAS REMAINING
LARGELY ABOVE 10 FEET THROUGH FRIDAY. AS WE HEAD INTO THE WEEKEND,
SEAS WILL BEGIN TO BUILD UPWARDS TOWARDS 15 TO 20 FEET.
MAZURKIEWICZ
HYDROLOGY
RIVERS FOR THE MOST PART ARE RECEDING THIS EVENING
WITH SOME RISES STILL OCCURRING ON THE LOWER REACHES OF THE MAIN
STEM RIVERS. SATSOP RIVER RECEDING QUICKLY AND ALREADY BACK DOWN TO
NEAR FLOOD STAGE. THE OTHER RIVER WITH A WARNING OUT, THE SKOKOMISH
WILL BE SLOW TO RECEDE TONIGHT. GOOD CHANCE THE RIVER REMAINS ABOVE
FLOOD STAGE THROUGH THURSDAY. THE CHEHALIS RIVER AT GRAND MOUND IS
STILL RISING AND WILL CREST NEAR FLOOD STAGE BETWEEN 4 AND 10 AM
THURSDAY. SAME STORY DOWNSTREAM FOR THE CHEHALIS AT PORTER, CRESTING
CLOSE TO FLOOD STAGE LATER THURSDAY.
ADDITIONAL INCOMING PRECIPITATION LATER IN THE 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. FELTON
SEW WATCHES/WARNINGS/ADVISORIES
WA...FLOOD WATCH THROUGH THURSDAY AFTERNOON FOR SOUTHWEST INTERIOR.
FLOOD WATCH THROUGH LATE THURSDAY NIGHT FOR CENTRAL COAST-LOWER
CHEHALIS VALLEY AREA-OLYMPICS.
PZ...SMALL CRAFT ADVISORY UNTIL 8 PM PST 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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