467
FXUS66 KSEW 151642
AFDSEW
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SEATTLE WA
842 AM PST SUN DEC 15 2024
SYNOPSIS
SCATTERED SHOWERS PERSIST THIS MORNING, WITH A BREAK
IN THE PRECIPITATION EXPECTED BY THE AFTERNOON. ANOTHER FRONTAL
SYSTEM IS OFFSHORE AND WILL MOVE INTO THE AREA TONIGHT INTO MONDAY
FOR ADDITIONAL RAIN. THE ACTIVE PATTERN WILL LINGER INTO THE
MIDDLE OF THE WEEK FOR ADDITIONAL CHANCES OF LOWLAND RAIN,
SLIGHTLY WARMER TEMPERATURES AND BREEZY WINDS.
SHORT TERM /TODAY THROUGH TUESDAY/
NO MAJOR UPDATES THIS
MORNING, OTHER THAT THE COASTAL FLOOD ADVISORY FOR THE INLAND
WATERS OF PUGET SOUND AND AREAS NORTH OF ADMIRALTY INLET HAS BEEN
ALLOWED TO EXPIRE AT 9 AM THIS MORNING. HIGH TIDE HAS PEAKED AND
IS ON THE WAY BACK DOWN. THE COASTAL FLOOD HEADLINE FOR THE COAST
IS STILL IN EFFECT.
THE BREAK IN PRECIPITATION WILL BE BRIEF AS ANOTHER FRONTAL
SYSTEM WILL SPREAD PRECIPITATION NORTHWARD TONIGHT INTO MONDAY FOR
ADDITIONAL LOWLAND RAIN AND MOUNTAIN SNOWFALL. WINDS WILL BE
LIGHTER WITH THIS FRONT COMPARED TO THE SATURDAY WEATHER SYSTEM,
WITH BREEZIER WINDS MAINLY CONFINED TO THE COAST. THE ACTIVE
PATTERN WILL CONTINUE TUESDAY INTO MIDWEEK AS ANOTHER SYSTEM
OFFSHORE LOOKS TO TRACK TOWARDS VANCOUVER ISLAND. A WARM FRONT
WILL LIKELY LIFT NORTHWARD TUESDAY INTO TUESDAY NIGHT FOR
ADDITIONAL PRECIPITATION, AS WELL AS INCREASING SNOW LEVELS. HIGH
TEMPERATURES THROUGH TUESDAY EXPECTED TO BE IN THE MID TO UPPER
40S.
LONG TERM /WEDNESDAY THROUGH SATURDAY/
THE AFOREMENTIONED
SYSTEM WILL CONTINUE TO IMPACT WESTERN WASHINGTON INTO WEDNESDAY.
UNCERTAINTY REMAINS IN ENSEMBLES IN THE EXACT TRACK OF THE SYSTEM.
HOWEVER, ECMWF EFI HIGHLIGHTS BOTH WINDS AND QPF AS ANOMALOUS
FROM CLIMO FROM 00Z WED TO 00Z THURS. THIS WILL BE ANOTHER PERIOD
TO MONITOR FOR PERHAPS MORE IMPACTFUL WEATHER. RIDGING THEN
BUILDS ACROSS THE INTERIOR WESTERN US THURSDAY INTO THE WEEKEND.
HOWEVER, THERE REMAINS CONTINUED UNCERTAINTY AS TO THE EXTENT THE
RIDGING INFLUENCES WESTERN WASHINGTON WITH SOME TROUGHING WELL
OFFSHORE. KEPT THE FORECAST NBM PRECIPITATION POTENTIAL IN THE
FORECAST DURING THIS PERIOD LATER THURSDAY INTO SATURDAY, BUT
ECMWF ENSEMBLES REMAIN THE DRIER SOLUTION OUT OF THE CLUSTERS.
TEMPERATURES WILL WARM ABOVE NORMAL LATER IN THE WEEK. JD/KRISTELL
AVIATION
WEST TO NORTHWEST FLOW ALOFT EXPECTED TODAY AS
A WEAK UPPER RIDGE SLIDES ONSHORE. THE FLOW ALOFT WILL BACK TO
SOUTHERLY AND INCREASE LATE TONIGHT INTO MONDAY AS ANOTHER UPPER
TROUGH AND ASSOCIATED FRONTAL SYSTEM APPROACHES THE REGION. AREAS OF
MVFR CEILINGS THIS MORNING WILL SCATTER OUT BY AFTERNOON AND
REMAINING SHOWER ACTIVITY WILL DISSIPATE. MID AND HIGH LEVEL
MOISTURE WILL INCREASE AGAIN THIS AFTERNOON AND EVENING AHEAD OF THE
NEXT SYSTEM. CEILINGS WILL DROP BACK TO MVFR IN INCREASING RAIN
ALONG THE COAST AFTER 00Z WITH SAID CONDITIONS GRADUALLY SPREADING
THE INTERIOR 06Z-12Z TONIGHT. LOW LEVEL OFFSHORE FLOW WILL INCREASE
TONIGHT WITH LOCALLY GUSTY EASTERLY SURFACE WINDS EXPECTED NEAR GAPS
IN TERRAIN LATE TONIGHT INTO MONDAY MORNING.
KSEA...MAINLY VFR EXPECTED TODAY WITH LOW LEVEL MOISTURE IN THE
VICINITY OF THE TERMINAL SCATTERING OUT BY LATE MORNING. HIGH AND
MID LEVEL CLOUDS WILL INCREASE THIS AFTERNOON AND TONIGHT.
DEVELOPING EASTERLY FLOW SHOULD DRY OUT THE LOW LEVELS TO SOME
DEGREE TONIGHT AND PRECLUDE THE DEVELOPMENT OF MVFR CEILINGS UNTIL
09Z-12Z MONDAY. LOW MVFR IN RAIN EXPECTED MUCH OF MONDAY.
SURFACE WINDS SOUTHERLY 8 TO 12 KNOTS WILL BACK TO EASTERLY 5 TO 8
KNOTS AFTER 00Z. 27
MARINE
WEAK SURFACE RIDGING OVER THE WATERS THIS MORNING WILL
QUICKLY SHIFT EASTWARD AND A WARM FRONT WILL LIFT NORTHWARD OVER THE
COASTAL AND OFFSHORE WATERS LATE THIS AFTERNOON INTO TONIGHT.
EASTERLY GALES WILL DEVELOP WITH THIS OVER THE COASTAL WATERS AND
THE WEST ENTRANCE TO THE STRAIT WITH SMALL CRAFT ADVISORY STRENGTH
EASTERLIES EXPECTED ACROSS THE REMAINDER OF THE STRAIT AND NORTHERN
INLAND WATERS. A WEAKENING OCCLUDED FRONT WILL PUSH INLAND DURING
THE MORNING ON MONDAY. BROAD TROUGHING WILL REMAIN POISED OVER THE
OFFSHORE WATERS THROUGH MUCH OF THE WEEK AS A SERIES OF SYSTEMS
PIVOT ONSHORE.
COASTAL SEAS HAVE BRIEFLY DROPPED BELOW 10 FEET THIS MORNING. THEY
WILL BUILD BACK INTO DOUBLE DIGITS TONIGHT AND LIKELY REMAIN
HAZARDOUS FOR THE FORESEEABLE FUTURE THEREAFTER. 27
HYDROLOGY
AREA RIVERS WILL RISE WITH ADDITIONAL PRECIPITATION
OVER THE NEXT WEEK, AND INCREASING SNOW LEVELS TUESDAY INTO LATER
IN THE WEEK. ADDITIONAL ROUNDS OF PRECIPITATION WILL KEEP AT LEAST
THE SKOKOMISH RIVER ELEVATED THROUGH THE WEEK. JD
SEW WATCHES/WARNINGS/ADVISORIES
WA...COASTAL FLOOD ADVISORY UNTIL 9 AM PST THIS MORNING FOR BREMERTON
AND VICINITY-EVERETT AND VICINITY-HOOD CANAL AREA-SAN JUAN
COUNTY-SEATTLE AND VICINITY-SOUTHWEST INTERIOR-TACOMA AREA-
WESTERN SKAGIT COUNTY-WESTERN WHATCOM COUNTY.
COASTAL FLOOD ADVISORY UNTIL 3 PM PST THIS AFTERNOON FOR CENTRAL
COAST.
WINTER WEATHER ADVISORY UNTIL 10 AM PST THIS MORNING FOR WEST
SLOPES NORTH CENTRAL CASCADES AND PASSES.
PZ...GALE WARNING FROM 4 PM THIS AFTERNOON TO 4 AM PST MONDAY 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.
SMALL CRAFT ADVISORY FROM 4 PM THIS AFTERNOON TO 10 AM PST
MONDAY FOR CENTRAL U.S. WATERS STRAIT OF JUAN DE FUCA-EAST
ENTRANCE U.S. WATERS STRAIT OF JUAN DE FUCA-NORTHERN INLAND
WATERS INCLUDING THE SAN JUAN ISLANDS.
SMALL CRAFT ADVISORY UNTIL 4 PM PST 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.
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