High Surf Advisory 7, NWS Seattle, WA

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SEATTLE WA
903 PM PST MON DEC 21 2015

.SYNOPSIS...TONIGHT WILL BE SHOWERY IN THE WAKE OF A FRONT. A
BRIEF LULL WILL OCCUR TUESDAY IN BETWEEN SYSTEMS. ANOTHER FRONT
WILL BRING RAIN LATER TUESDAY AND TUESDAY NIGHT. SHOWERS WILL
DECREASE WEDNESDAY AND THURSDAY AS DRIER NORTHERLY FLOW ALOFT
DEVELOPS. AN UPPER RIDGE WILL BRING DRY WEATHER LATE IN THE WEEK.

&&

.SHORT TERM...A FRONT WILL SHIFT INLAND TONIGHT WITH SHOWERS IN
ITS WAKE. SNOW WILL CONTINUE OVER THE MOUNTAINS...TAPERING LATE.
ADVISORIES AND WARNINGS ARE UP FOR TONIGHT FOR THE CASCADES.
AFTER A RELATIVE LULL FOR MUCH OF THE DAY TUESDAY...ANOTHER FRONT
WILL BRING RAIN AND MORE MOUNTAIN SNOW. RAIN SHOULD SPREAD ONTO
THE COAST IN THE AFTERNOON AND INTO THE INTERIOR LATE AFTERNOON OR
EARLY EVENING. RAIN WILL CHANGE TO SHOWERS TUESDAY NIGHT AS THE
FRONT MOVES THROUGH. THERE SHOULD BE ANOTHER GOOD SHOT OF SNOW IN
THE CASCADES TUESDAY NIGHT AND WEDNESDAY. IT LOOKS BREEZY TO WINDY
MOST AREAS BEHIND THE FRONT LATER TUESDAY NIGHT AND WEDNESDAY. A
BAGGY UPPER TROUGH WILL MOVE OVER THE AREA ON THURSDAY WITH
DECREASING SHOWERS. SCHNEIDER

.LONG TERM...DRIER NORTHERLY FLOW ALOFT WILL DEVELOP THURSDAY
NIGHT AND FRIDAY AS A STRONG UPPER RIDGE BUILDS OFFSHORE. SNOW
LEVELS WILL DROP TO NEAR SEA LEVEL THURSDAY NIGHT AND FRIDAY BUT
SHOWER ACTIVITY WILL BE SPOTTY AND COMING TO AN END. LOWLAND
ACCUMULATIONS DO NOT LOOK LIKELY AT THIS TIME. AN UPPER RIDGE WILL
BRING DRY WEATHER SATURDAY. TEMPERATURES WILL BE A FEW DEGREES
BELOW NORMAL. A FRONTAL SYSTEM WILL BRING A LITTLE RAIN EITHER
LATER SUNDAY OR SUNDAY NIGHT AND MONDAY. SCHNEIDER

&&

.AVIATION...MODERATE NW FLOW ALOFT WILL CONTINUE OVER W WA TONIGHT
AS AN UPPER LEVEL TROUGH OVER E WA CONTINUES E AND A WEAK UPPER
LEVEL RIDGE MOVES OVER THE COASTAL WATERS. SHOWERS EMBEDDED IN THE
NW FLOW ARE STILL PRESENT OFFSHORE AND WILL CONTINUE TO MOVE INLAND
ACROSS W WA TONIGHT. THE AIR MASS IS MOIST AND SOMEWHAT UNSTABLE.
THE SHOWERS WILL TAPER OFF TUESDAY MORNING. THE MOIST AIR MASS WILL
KEEP CIGS IN THE MVFR RANGE WITH LOCAL IFR CONDITIONS ACROSS PUGET
SOUND. MINOR IMPROVEMENT IS EXPECTED TUESDAY AFTERNOON WITH A MIX OF
MVFR AND LOW END VFR CIGS.

AN APPROACHING UPPER LEVEL TROUGH AND COLD FRONT WILL REACH THE
COAST TUESDAY AFTERNOON BY 00Z THEN SPREAD LIGHT RAIN INLAND DURING
THE EVENING.

KSEA...MAINLY MVFR CONDITIONS TONIGHT WITH CIGS BKN-OVC010-025.
THERE COULD BE A PERIOD OF IFR CIGS BETWEEN 10Z-16Z. IMPROVEMENT TO
BKN025-040 MAY NOT DEVELOP UNTIL AFTER 18Z. SURFACE WINDS WILL
REMAIN SOUTHERLY 5 TO 10 KT. KAM

&&

.MARINE...A WEAK SURFACE RIDGE WILL BUILD BRIEFLY OVER WESTERN WA
AND THE COASTAL WATERS TONIGHT. A SURGE OF WEST WIND IS EXPECTED IN
THE STRAIT TONIGHT FOR SCA WEST WINDS.

AN APPROACHING COLD FRONT NEAR 140W AT 03Z/7 PM WILL REACH THE
COASTAL WATERS TUESDAY AFTERNOON THEN MOVE INLAND TUESDAY EVENING.
STRONG NW FLOW WILL DEVELOP IMMEDIATELY BEHIND THE COLD FRONT WITH
GALES EXPECTED OVER THE COASTAL WATERS TUESDAY NIGHT AND
WEDNESDAY...AND A GALE WATCH IS CURRENTLY IN EFFECT. THE ASSOCIATED
992 MB SURFACE LOW WILL MOVE MOVE OVER CAPE FLATTERY EARLY TUESDAY
EVENING THEN WEAKEN OVER THE NORTH INTERIOR TUESDAY NIGHT. ANOTHER
LOW WILL MOVE OVER THE AREA ON WEDNESDAY THEN GRADUALLY WEAKEN
THROUGH FRIDAY.

THE STRONG NW FLOW ON TUESDAY IS EXPECTED TO GENERATE A LARGE
WESTERLY SWELL 20-25 FT THAT WILL REACH THE COAST TUESDAY
EVENING...PEAK WEDNESDAY MORNING...THEN SLOWLY SUBSIDE THROUGH
WEDNESDAY EVENING. TIDES ARE STILL RUNNING ON THE HIGH SIDE AND THE
MIDDAY HIGH TIDE ALONG THE COAST COULD GENERATE SOME MINOR TIDAL
OVERFLOW IN ADDITION TO WHAT THE LARGE WAVES MAY DO. A COASTAL FLOOD
WATCH IS IN EFFECT. KAM

&&

.HYDROLOGY...FLOODING IS UNLIKELY OVER THE NEXT 7 DAYS.

&&

.CLIMATE...SEATAC AIRPORT RECEIVED 1.03 INCHES OF RAIN TODAY
THROUGH 5 PM. BESIDES BEING A RECORD FOR THE DAY...THIS IS ALSO
THE 14TH DAY THIS YEAR WITH AN INCH OR MORE OF RAIN AT SEATAC.
PRIOR TO 2015...THE MOST OCCURRENCES IN ANY CALENDAR YEAR OF AN
INCH OR MORE OF RAIN IN A DAY AT SEATAC HAD BEEN 9...WHICH
OCCURRED MOST RECENTLY IN 2006.

THE RAIN TODAY THROUGH 5 PM ALSO PUSHED THE TOTAL FOR DECEMBER AT
SEATAC TO 10.01 INCHES. TEN OR MORE INCHES OF RAIN AT SEATAC IN A
MONTH IS RARE. THE TEN INCHES THIS MONTH IS JUST THE NINTH TIME
THAT HAS OCCURRED FOR ANY MONTH AT SEATAC. THE 10.01 INCHES
THROUGH 5 PM TODAY MAKE THIS MONTH CURRENTLY THE THIRD WETTEST
DECEMBER ON RECORD AND COUNTING. THE SECOND WETTEST DECEMBER ON
RECORD IS 10.18 IN 1996. THE WETTEST DECEMBER WAS 11.85 INCHES IN
1979. RECORDS FOR SEATAC GO BACK TO 1945. SCHNEIDER

&&

.SEW WATCHES/WARNINGS/ADVISORIES...
WA...WINTER STORM WARNING UNTIL 4 AM PST TUESDAY FOR CASCADES OF
     PIERCE AND LEWIS COUNTIES.

     WINTER STORM WATCH FROM TUESDAY AFTERNOON THROUGH LATE WEDNESDAY
     NIGHT FOR CASCADES OF PIERCE AND LEWIS COUNTIES-CASCADES OF
     SNOHOMISH AND KING COUNTIES.

     WINTER WEATHER ADVISORY UNTIL 4 AM PST TUESDAY FOR CASCADES OF
     SNOHOMISH AND KING COUNTIES.

     COASTAL FLOOD WATCH FROM WEDNESDAY MORNING THROUGH WEDNESDAY
     AFTERNOON FOR CENTRAL COAST.

PZ...GALE WATCH FROM TUESDAY AFTERNOON THROUGH WEDNESDAY AFTERNOON
     COASTAL WATERS.

     SMALL CRAFT ADVISORY UNTIL 1 PM PST TUESDAY COASTAL WATERS.

     GALE WARNING UNTIL 10 PM PST THIS EVENING COASTAL WATERS.

     SMALL CRAFT ADVISORY FOR ROUGH BAR UNTIL 6 PM PST TUESDAY FOR
     GRAYS HARBOR BAR.

     SMALL CRAFT ADVISORY UNTIL 7 AM PST TUESDAY FOR CENTRAL U.S.
     WATERS STRAIT OF JUAN DE FUCA-EAST ENTRANCE U.S. WATERS
     STRAIT OF JUAN DE FUCA.

     SMALL CRAFT ADVISORY UNTIL 4 AM PST TUESDAY FOR WEST ENTRANCE
     U.S. WATERS STRAIT OF JUAN DE FUCA.

&&

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