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000
FXUS66 KSEW 211129
AFDSEW

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SEATTLE WA
330 AM PST SUN DEC 21 2014

.SYNOPSIS...STRONG MOIST WEST FLOW ALOFT WILL CONTINUE TODAY THEN
WEAKEN TONIGHT...BRINGING LIGHT RAIN TO THE LOWLANDS AND HEAVIER
RAIN TO THE CASCADES. AN UPPER LEVEL RIDGE WILL BUILD OVER THE
REGION MONDAY FOR DRIER WEATHER. A FRONTAL SYSTEM WILL MOVE OVER
WESTERN WASHINGTON LATE MONDAY NIGHT AND TUESDAY FOLLOWED BY AN
UPPER LEVEL TROUGH ON WEDNESDAY FOR PERIODS OF RAIN. DRIER AND
COOLER NORTHWEST FLOW ALOFT WILL DEVELOP AFTER MIDWEEK.

&&

.SHORT TERM...STRONG WEST FLOW ALOFT WILL CONTINUE OVER W WA
TODAY...THEN EASE A LITTLE TONIGHT. LOW LEVEL MOISTURE AND LARGE
SCALE LIFT HAS DIMINISHED AS WELL...SO MUCH OF THE LOWLANDS IS
CURRENTLY FREE OF RAIN. GIVEN THE STRONG W FLOW THE MAIN FORCING
TODAY WILL BE OROGRAPHIC IN NATURE...WITH PRECIPITATION MAINLY OVER
THE MOUNTAINS. THE STRONGEST OROGRAPHIC FLOW WILL BE FROM ABOUT
SNOHOMISH COUNTY SOUTHWARD. LOW LEVEL ONSHORE FLOW IS ALSO PRESENT
SO COMBINED WITH THE STRONG W FLOW ALOFT THIS MAY CREATE SOME NARROW
CONVERGENCE LIKE RAIN BANDS OVER PARTS OF THE PUGET SOUND REGION.
OTHER THAN THESE RAIN BANDS THE PUGET SOUND REGION WILL BE IN THE
EAST RAIN SHADOW OF THE OLYMPICS SO OVERALL NOT MUCH RAIN IS
EXPECTED. THE ONSHORE FLOW IS STRONG ENOUGH TO KEEP WINDS BREEZY IN
MANY AREAS.

THE AIR MASS IS RATHER WARM THIS MORNING WITH SNOW LEVELS 5000 FEET
AROUND MT BAKER TO 6500 FEET AROUND MT RAINIER. THE SNOW LEVEL WILL
GRADUALLY LOWER TO 4000 TO 5500 FEET BY LATE THIS AFTERNOON. WITH
SNOW STARTING TO ACCUMULATE AT LOWER ELEVATIONS WHILE PRECIP RATES
DECLINE...SNOW ACCUMULATIONS SHOULD STAY BELOW ADVISORY LEVELS AT MT
BAKER AND STEVENS PASS. UP TO 10 INCHES MAY FALL ON MT RAINIER BUT
THIS SHOULD BE JUST ABOVE THE CRITICAL 5500 FOOT LEVEL OF PARADISE.

A MODERATE AMPLITUDE UPPER LEVEL RIDGE WILL BE BUILDING OFFSHORE
TONIGHT THEN SLIDE E OVER W WA ON MONDAY. GRADUAL DRYING WILL LOWER
THE CHANCE OF RAIN TONIGHT. ACCUMULATIONS OVER THE LOWLANDS WILL
GENERALLY BE A TENTH OF AN INCH OR LESS. ACCUMULATIONS OVER THE
CASCADES WILL BE HIGHER BUT HYDROLOGICALLY INSIGNIFICANT.

WITH THE UPPER LEVEL RIDGE AXIS JUST OFFSHORE...MONDAY WILL BE
PRETTY MUCH DRY. I KEPT LOW CHANCE POPS MONDAY MORNING MAINLY
BECAUSE THE AIR MASS WILL STILL BE ON THE MOIST SIDE. MONDAY
AFTERNOON WILL BE DRY WITH A LITTLE BIT OF SUNSHINE. THE DRY PERIOD
SHOULD EXTEND INTO MONDAY EVENING.

MODELS HAVE BEEN PRETTY CONSISTENT IN SLIDING THE UPPER LEVEL RIDGE
INLAND AND FLATTENING IT MONDAY NIGHT. THIS WILL ALLOW A FRONTAL
SYSTEM PUSHING INTO THE UPSTREAM SIDE OF THE RIDGE TO MOVE INLAND
OVER W WA. WEAK WARM ADVECTION WILL BRING LIGHT RAIN TO THE AREA
LATE MONDAY NIGHT AND TUESDAY. KAM

.LONG TERM...MODELS STILL AGREE THAT AN UPPER LEVEL TROUGH WILL MOVE
ACROSS W WA ON WEDNESDAY. THE REMNANTS OF THE TUESDAY FRONTAL
SYSTEM WILL STILL BE OVER W WA ON WEDNESDAY AND THE APPROACHING
TROUGH WILL MAKE GOOD USE OF THE MOISTURE. POPS HAVE BEEN INCREASED
WITH RAIN EXPECTED OVER ALL OF W WA. DRIER NW FLOW ALOFT SETS UP
OVER THE REGION BEHIND THE UPPER LEVEL TROUGH THURSDAY AND FRIDAY.
THE CURRENT FORECAST IS DRY...BUT MAY BE A LITTLE OPTIMISTIC. THERE
COULD STILL BE SOME LEFTOVER RAIN AS THE TROUGH DEPARTS WEDNESDAY
EVENING...AND THERE IS A CHANCE THAT ANY VERY WEAK SHORTWAVES
EMBEDDED IN THE NW FLOW COULD BRING A CHANCE OF RAIN THURSDAY AND
FRIDAY. THE GFS/ECMWF SEEM A LITTLE MORE CONSISTENT FOR THE LATE
WEEK PERIOD...BUT CONFIDENCE IS STILL ON THE LOW SIDE. KAM

&&

.HYDROLOGY...RAINFALL AMOUNTS FOR THE PAST 12 HOURS ENDING AT 3 AM
HAVE GENERALLY BEEN BETWEEN 1 AND 3 INCHES IN THE OLYMPICS AND
CASCADES WITH THE HIGHEST AMOUNT AT WHITE PASS WITH A LITTLE MORE
THAN 3 AND A HALF INCHES. RAINFALL RATES HAVE SLOWED CONSIDERABLY IN
THE LAST HOUR OR TWO...DOWN TO AROUND A TENTH TO TWO TENTHS AN HOUR.
RAINFALL RATES WILL CONTINUE TO DECREASE THIS MORNING IN THE
MOUNTAINS. IN ADDITION THE PRECIPITATION WILL TURN OVER TO SNOW
ABOVE ABOUT 5000 FEET AS A SLIGHTLY COOLER AIR MASS MOVES INTO THE
AREA.

WITH THE DECREASING RAINFALL RATES THE FLOOD WATCH FOR CLALLAM AND
JEFFERSON COUNTY WILL BE CANCELLED WITH THE EARLY MORNING FORECAST
PACKAGE. THERE IS A GOOD CHANCE THE WATCH FOR THE REMAINING COUNTIES
GRAYS HARBOR...KING...LEWIS...PIERCE...SNOHOMISH...AND THURSTON WILL
BE CANCELLED AS WELL DURING THE DAY TODAY.

THE ONLY RIVER WITH A FLOOD WARNING IN EFFECT EARLY THIS MORNING IS
THE SKOKOMISH. WITH THE HEAVIEST RAIN OVERNIGHT FROM MOUNT RAINIER
SOUTH THE BEST CHANCE FOR ANY ADDITIONAL RIVER FLOODING IS ON THE
COWLITZ RIVER AND EVEN THAT WILL BE MINOR IF THE RIVER REACHES FLOOD
STAGE.

FLOODING IS NOT EXPECTED MON THROUGH SATURDAY. FELTON

&&

.AVIATION...STRONG WESTERLY FLOW ALOFT WILL PREVAIL TODAY AND
TONIGHT. AT THE SURFACE...MODERATE TO STRONG ONSHORE FLOW WILL
GRADUALLY EASE TODAY AND TONIGHT WITH HIGH PRESSURE BUILDING OVER
THE COAST TONIGHT. AIR MASS MOIST AND SLIGHTLY UNSTABLE. THERE WILL
BE AREAS OF LOW CLOUDS TODAY BUT ALSO SOME BREAKS. THERE WILL LIKELY
BE A PUGET SOUND CONVERGENCE ZONE OVER NORTHERN PUGET SOUND TODAY.

KSEA...THERE SHOULD BE LOW CLOUDS AT TIMES TODAY BUT ALSO SOME
BREAKS. SOUTHERLY WIND 15G30KT...EASING A BIT BY AFTERNOON. SCHNEIDER

&&

.MARINE...MODERATE TO STRONG ONSHORE FLOW WILL PREVAIL TODAY WITH
WESTERLY GALES IN THE STRAIT AND SMALL CRAFT ADVISORIES ALL OTHER
WATERS. ONSHORE FLOW WILL EASE TONIGHT WITH HIGH PRESSURE BUILDING
OVER THE AREA ON MONDAY. A FRONTAL SYSTEM WILL ARRIVE AROUND
TUESDAY. SCHNEIDER

&&

.SEW WATCHES/WARNINGS/ADVISORIES...
WA...FLOOD WARNINGS OR WATCHES ARE IN EFFECT FOR PARTS OF THE
      CWA.
PZ...GALE WARNING CENTRAL AND EASTERN STRAIT OF JUAN DE FUCA.
     SMALL CRAFT ADVISORY ALL OTHER WATERS.
     SMALL CRAFT ADVISORY FOR SEVERE CONDITIONS GRAYS HARBOR BAR.

&&

$$

WWW.WEATHER.GOV/SEATTLE

YOU CAN SEE AN ILLUSTRATED VERSION OF THIS FORECAST DISCUSSION AT
WWW.WEATHER.GOV/SEATTLE/GAFD/LATEST_WEBAFD.HTML









000
FXUS66 KSEW 211129
AFDSEW

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SEATTLE WA
330 AM PST SUN DEC 21 2014

.SYNOPSIS...STRONG MOIST WEST FLOW ALOFT WILL CONTINUE TODAY THEN
WEAKEN TONIGHT...BRINGING LIGHT RAIN TO THE LOWLANDS AND HEAVIER
RAIN TO THE CASCADES. AN UPPER LEVEL RIDGE WILL BUILD OVER THE
REGION MONDAY FOR DRIER WEATHER. A FRONTAL SYSTEM WILL MOVE OVER
WESTERN WASHINGTON LATE MONDAY NIGHT AND TUESDAY FOLLOWED BY AN
UPPER LEVEL TROUGH ON WEDNESDAY FOR PERIODS OF RAIN. DRIER AND
COOLER NORTHWEST FLOW ALOFT WILL DEVELOP AFTER MIDWEEK.

&&

.SHORT TERM...STRONG WEST FLOW ALOFT WILL CONTINUE OVER W WA
TODAY...THEN EASE A LITTLE TONIGHT. LOW LEVEL MOISTURE AND LARGE
SCALE LIFT HAS DIMINISHED AS WELL...SO MUCH OF THE LOWLANDS IS
CURRENTLY FREE OF RAIN. GIVEN THE STRONG W FLOW THE MAIN FORCING
TODAY WILL BE OROGRAPHIC IN NATURE...WITH PRECIPITATION MAINLY OVER
THE MOUNTAINS. THE STRONGEST OROGRAPHIC FLOW WILL BE FROM ABOUT
SNOHOMISH COUNTY SOUTHWARD. LOW LEVEL ONSHORE FLOW IS ALSO PRESENT
SO COMBINED WITH THE STRONG W FLOW ALOFT THIS MAY CREATE SOME NARROW
CONVERGENCE LIKE RAIN BANDS OVER PARTS OF THE PUGET SOUND REGION.
OTHER THAN THESE RAIN BANDS THE PUGET SOUND REGION WILL BE IN THE
EAST RAIN SHADOW OF THE OLYMPICS SO OVERALL NOT MUCH RAIN IS
EXPECTED. THE ONSHORE FLOW IS STRONG ENOUGH TO KEEP WINDS BREEZY IN
MANY AREAS.

THE AIR MASS IS RATHER WARM THIS MORNING WITH SNOW LEVELS 5000 FEET
AROUND MT BAKER TO 6500 FEET AROUND MT RAINIER. THE SNOW LEVEL WILL
GRADUALLY LOWER TO 4000 TO 5500 FEET BY LATE THIS AFTERNOON. WITH
SNOW STARTING TO ACCUMULATE AT LOWER ELEVATIONS WHILE PRECIP RATES
DECLINE...SNOW ACCUMULATIONS SHOULD STAY BELOW ADVISORY LEVELS AT MT
BAKER AND STEVENS PASS. UP TO 10 INCHES MAY FALL ON MT RAINIER BUT
THIS SHOULD BE JUST ABOVE THE CRITICAL 5500 FOOT LEVEL OF PARADISE.

A MODERATE AMPLITUDE UPPER LEVEL RIDGE WILL BE BUILDING OFFSHORE
TONIGHT THEN SLIDE E OVER W WA ON MONDAY. GRADUAL DRYING WILL LOWER
THE CHANCE OF RAIN TONIGHT. ACCUMULATIONS OVER THE LOWLANDS WILL
GENERALLY BE A TENTH OF AN INCH OR LESS. ACCUMULATIONS OVER THE
CASCADES WILL BE HIGHER BUT HYDROLOGICALLY INSIGNIFICANT.

WITH THE UPPER LEVEL RIDGE AXIS JUST OFFSHORE...MONDAY WILL BE
PRETTY MUCH DRY. I KEPT LOW CHANCE POPS MONDAY MORNING MAINLY
BECAUSE THE AIR MASS WILL STILL BE ON THE MOIST SIDE. MONDAY
AFTERNOON WILL BE DRY WITH A LITTLE BIT OF SUNSHINE. THE DRY PERIOD
SHOULD EXTEND INTO MONDAY EVENING.

MODELS HAVE BEEN PRETTY CONSISTENT IN SLIDING THE UPPER LEVEL RIDGE
INLAND AND FLATTENING IT MONDAY NIGHT. THIS WILL ALLOW A FRONTAL
SYSTEM PUSHING INTO THE UPSTREAM SIDE OF THE RIDGE TO MOVE INLAND
OVER W WA. WEAK WARM ADVECTION WILL BRING LIGHT RAIN TO THE AREA
LATE MONDAY NIGHT AND TUESDAY. KAM

.LONG TERM...MODELS STILL AGREE THAT AN UPPER LEVEL TROUGH WILL MOVE
ACROSS W WA ON WEDNESDAY. THE REMNANTS OF THE TUESDAY FRONTAL
SYSTEM WILL STILL BE OVER W WA ON WEDNESDAY AND THE APPROACHING
TROUGH WILL MAKE GOOD USE OF THE MOISTURE. POPS HAVE BEEN INCREASED
WITH RAIN EXPECTED OVER ALL OF W WA. DRIER NW FLOW ALOFT SETS UP
OVER THE REGION BEHIND THE UPPER LEVEL TROUGH THURSDAY AND FRIDAY.
THE CURRENT FORECAST IS DRY...BUT MAY BE A LITTLE OPTIMISTIC. THERE
COULD STILL BE SOME LEFTOVER RAIN AS THE TROUGH DEPARTS WEDNESDAY
EVENING...AND THERE IS A CHANCE THAT ANY VERY WEAK SHORTWAVES
EMBEDDED IN THE NW FLOW COULD BRING A CHANCE OF RAIN THURSDAY AND
FRIDAY. THE GFS/ECMWF SEEM A LITTLE MORE CONSISTENT FOR THE LATE
WEEK PERIOD...BUT CONFIDENCE IS STILL ON THE LOW SIDE. KAM

&&

.HYDROLOGY...RAINFALL AMOUNTS FOR THE PAST 12 HOURS ENDING AT 3 AM
HAVE GENERALLY BEEN BETWEEN 1 AND 3 INCHES IN THE OLYMPICS AND
CASCADES WITH THE HIGHEST AMOUNT AT WHITE PASS WITH A LITTLE MORE
THAN 3 AND A HALF INCHES. RAINFALL RATES HAVE SLOWED CONSIDERABLY IN
THE LAST HOUR OR TWO...DOWN TO AROUND A TENTH TO TWO TENTHS AN HOUR.
RAINFALL RATES WILL CONTINUE TO DECREASE THIS MORNING IN THE
MOUNTAINS. IN ADDITION THE PRECIPITATION WILL TURN OVER TO SNOW
ABOVE ABOUT 5000 FEET AS A SLIGHTLY COOLER AIR MASS MOVES INTO THE
AREA.

WITH THE DECREASING RAINFALL RATES THE FLOOD WATCH FOR CLALLAM AND
JEFFERSON COUNTY WILL BE CANCELLED WITH THE EARLY MORNING FORECAST
PACKAGE. THERE IS A GOOD CHANCE THE WATCH FOR THE REMAINING COUNTIES
GRAYS HARBOR...KING...LEWIS...PIERCE...SNOHOMISH...AND THURSTON WILL
BE CANCELLED AS WELL DURING THE DAY TODAY.

THE ONLY RIVER WITH A FLOOD WARNING IN EFFECT EARLY THIS MORNING IS
THE SKOKOMISH. WITH THE HEAVIEST RAIN OVERNIGHT FROM MOUNT RAINIER
SOUTH THE BEST CHANCE FOR ANY ADDITIONAL RIVER FLOODING IS ON THE
COWLITZ RIVER AND EVEN THAT WILL BE MINOR IF THE RIVER REACHES FLOOD
STAGE.

FLOODING IS NOT EXPECTED MON THROUGH SATURDAY. FELTON

&&

.AVIATION...STRONG WESTERLY FLOW ALOFT WILL PREVAIL TODAY AND
TONIGHT. AT THE SURFACE...MODERATE TO STRONG ONSHORE FLOW WILL
GRADUALLY EASE TODAY AND TONIGHT WITH HIGH PRESSURE BUILDING OVER
THE COAST TONIGHT. AIR MASS MOIST AND SLIGHTLY UNSTABLE. THERE WILL
BE AREAS OF LOW CLOUDS TODAY BUT ALSO SOME BREAKS. THERE WILL LIKELY
BE A PUGET SOUND CONVERGENCE ZONE OVER NORTHERN PUGET SOUND TODAY.

KSEA...THERE SHOULD BE LOW CLOUDS AT TIMES TODAY BUT ALSO SOME
BREAKS. SOUTHERLY WIND 15G30KT...EASING A BIT BY AFTERNOON. SCHNEIDER

&&

.MARINE...MODERATE TO STRONG ONSHORE FLOW WILL PREVAIL TODAY WITH
WESTERLY GALES IN THE STRAIT AND SMALL CRAFT ADVISORIES ALL OTHER
WATERS. ONSHORE FLOW WILL EASE TONIGHT WITH HIGH PRESSURE BUILDING
OVER THE AREA ON MONDAY. A FRONTAL SYSTEM WILL ARRIVE AROUND
TUESDAY. SCHNEIDER

&&

.SEW WATCHES/WARNINGS/ADVISORIES...
WA...FLOOD WARNINGS OR WATCHES ARE IN EFFECT FOR PARTS OF THE
      CWA.
PZ...GALE WARNING CENTRAL AND EASTERN STRAIT OF JUAN DE FUCA.
     SMALL CRAFT ADVISORY ALL OTHER WATERS.
     SMALL CRAFT ADVISORY FOR SEVERE CONDITIONS GRAYS HARBOR BAR.

&&

$$

WWW.WEATHER.GOV/SEATTLE

YOU CAN SEE AN ILLUSTRATED VERSION OF THIS FORECAST DISCUSSION AT
WWW.WEATHER.GOV/SEATTLE/GAFD/LATEST_WEBAFD.HTML








000
FXUS66 KSEW 210540
AFDSEW

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SEATTLE WA
940 PM PST SAT DEC 20 2014

.SYNOPSIS...STRONG AND MOIST WESTERLY FLOW ALOFT WILL PERSIST
THROUGH SUNDAY. HIGH PRESSURE ALOFT WILL BUILD OVER THE REGION
SUNDAY NIGHT AND WILL REMAIN OVER THE AREA ON MONDAY FOR A DRYING
TREND. THE HIGH WILL WEAKEN ON ON TUESDAY...ALLOWING A FRONT TO
SAG INTO THE AREA FROM THE NORTHWEST.

&&

.SHORT TERM...
THE STEADY PRECIP HAS BECOME SHOWERY ACROSS THE CWA. HOWEVER
STRONG OROGRAPHIC ENHANCEMENT WILL RESULT IN LOCALLY HEAVY SHOWERS
AT TIMES ON THE WEST FACING SLOPES OF THE MOUNTAINS. STRONG
SHADOWING TO THE LEE OF THE OLYMPIC RANGE WILL RESULT IN PARTS OF
THE PUGET SOUND REGION BEING MAINLY DRY OVERNIGHT.

STRONG AND MOIST ZONAL FLOW ALOFT WILL CONTINUE ON SUNDAY. FAST-
MOVING DISTURBANCES EMBEDDED IN THIS FLOW WILL RESULT IN LOCALLY
HEAVY SHOWERS ON THE WEST FACING SLOPES OF THE CASCADES. THE SNOW
LEVEL SHOULD BE MAINLY IN THE 4000 TO 5000 FOOT RANGE DURING THE
DAY...SO EXPECT THE PRECIP TO FALL MAINLY AS SNOW ABOVE THE 4000
FOOT LEVEL. IN FACT...IT LOOKS LIKE A WINTER WEATHER ADVISORY WILL
BE NEEDED FOR THE CASCADES FOR SUNDAY AS AMOUNTS COULD END UP IN
THE 6 TO 11 INCH RANGE...ESPECIALLY IN THE CENTRAL CASCADES.

EXPECT A GRADUAL DRYING TREND SUNDAY NIGHT DUE TO AN UPPER RIDGE
BUILDING OVER THE REGION. THIS RIDGE WILL PREVAIL OVER THE AREA ON
MON FOR DRY CONDITIONS ACROSS MUCH OF THE CWA.

MODELS SHOWED THE RIDGE FLATTENING ON TUE WITH A BAROCLINIC ZONE
SAGGING SOUTH OVER THE CWA DURING THE DAY. 33/05

.LONG TERM FROM THE PREVIOUS DISCUSSION...
A COOL UPPER LEVEL TROUGH WILL CUT THROUGH WESTERN WA ON WEDNESDAY
FOR COOLER WEATHER AND MORE SHOWERS. SNOW LEVELS WILL DROP TO
AROUND 2000 FT. DRY NORTHERLY FLOW WILL PREVAIL ON CHRISTMAS DAY
FOR MAINLY DRY WEATHER...WITH JUST ISOLATED SHOWERS IN THE CASCADES.
THIS PATTERN WILL CONTINUE INTO FRIDAY. MODELS THEN SHOW ANOTHER
COOL UPPER TROUGH CROSSING THE PAC NW ON SATURDAY...WITH SHOWERS
LINGERING INTO SUN. 33

&&

.HYDROLOGY...
A FLOOD WARNING WAS ISSUED FOR THE SKOKOMISH RIVER LATE IN THE
AFTERNOON. THE RIVER WAS STILL RISING AND WAS AT 16.9 FEET AROUND
915 PM PST. OTHER RIVERS SUCH AS THE ELWHA WERE SHOWING SHARP
RISES. A FLOOD WATCH REMAINS IN EFFECT FOR MUCH OF THE RIVERS
DRAINING OFF THE OLYMPICS AND CENTRAL CASCADES THROUGH LATE SUNDAY
NIGHT.

SNOW LEVELS ALSO ROSE THIS EVENING...WITH THE SNOW CHANGING OVER
TO RAIN ABOVE THE 3000 FOOT LEVEL. A MILDER AIR MASS ALONG WITH
STRONG UPSLOPE FLOW WILL RESULT IN LOCALLY HEAVY SHOWERS AT
TIMES...MAINLY ON THE CASCADES...THROUGH SUNDAY. THE MODELS
INDICATED AN ADDITIONAL 1-2 INCHES OF PRECIP WILL FALL ON THE
CASCADES OVERNIGHT INTO SUNDAY MORNING. HOWEVER THE SNOW LEVELS
WILL LOWER INTO THE 4500 TO 5500 FOOT RANGE BY SUNDAY MORNING...SO
SOME OF THIS PRECIP WILL BE IN THE FORM OF SNOW.

THE RIVERS THAT DO EXPERIENCE FLOODING SHOULD CREST DURING THE
DAY SUNDAY...SUNDAY NIGHT AT THE LATEST.

FLOODING IS NOT EXPECTED MON THROUGH SATURDAY.

&&

.AVIATION...STRONG WESTERLY FLOW ALOFT WILL PREVAIL TONIGHT AND
SUNDAY. STRONG ONSHORE FLOW AT THE SURFACE WILL START TO EASE LATER
SUNDAY. THE AIR MASS WILL BE MOIST AND STABLE. LOW CLOUDS TONIGHT.
CEILINGS SHOULD LIFT A LITTLE DURING THE DAY ON SUNDAY.

KSEA...LOW CLOUDS. CEILINGS LIFTING A BIT SUNDAY AFTERNOON.
SOUTHERLY WIND 15G30KT...EASING A BIT SUNDAY AFTERNOON. SCHNEIDER

&&

.MARINE...A STRONG FRONTAL SYSTEM WILL MOVE ONSHORE TONIGHT...
BRINGING GALES TO MOST WATERS. SUNDAY WILL BE A POST-FRONTAL DAY WITH
ONSHORE FLOW EASING SUNDAY NIGHT AND MONDAY. HIGH PRESSURE WILL
BUILD OVER THE AREA ON MONDAY. A WEAKER FRONTAL SYSTEM WILL ARRIVE
AROUND TUESDAY. SCHNEIDER

&&

.SEW WATCHES/WARNINGS/ADVISORIES...
WA...FLOOD WARNINGS OR WATCHES ARE IN EFFECT FOR MUCH OF THE CWA.

PZ...GALE WARNINGS ARE IN EFFECT FOR THE COASTAL WATERS...STRAIT
     OF JUAN DE FUCA...AND NORTHERN INLAND WATERS.

     SMALL CRAFT ADVISORIES ARE IN EFFECT FOR THE REMAINING
     WATERS.

     SMALL CRAFT ADVISORY FOR ROUGH BAR IN EFFECT TIL 6 PM SUNDAY
     FOR THE GRAYS HARBOR BAR.

&&

$$

WWW.WEATHER.GOV/SEATTLE

YOU CAN SEE AN ILLUSTRATED VERSION OF THIS FORECAST DISCUSSION AT
WWW.WEATHER.GOV/SEATTLE/GAFD/LATEST_WEBAFD.HTML





000
FXUS66 KSEW 210540
AFDSEW

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SEATTLE WA
940 PM PST SAT DEC 20 2014

.SYNOPSIS...STRONG AND MOIST WESTERLY FLOW ALOFT WILL PERSIST
THROUGH SUNDAY. HIGH PRESSURE ALOFT WILL BUILD OVER THE REGION
SUNDAY NIGHT AND WILL REMAIN OVER THE AREA ON MONDAY FOR A DRYING
TREND. THE HIGH WILL WEAKEN ON ON TUESDAY...ALLOWING A FRONT TO
SAG INTO THE AREA FROM THE NORTHWEST.

&&

.SHORT TERM...
THE STEADY PRECIP HAS BECOME SHOWERY ACROSS THE CWA. HOWEVER
STRONG OROGRAPHIC ENHANCEMENT WILL RESULT IN LOCALLY HEAVY SHOWERS
AT TIMES ON THE WEST FACING SLOPES OF THE MOUNTAINS. STRONG
SHADOWING TO THE LEE OF THE OLYMPIC RANGE WILL RESULT IN PARTS OF
THE PUGET SOUND REGION BEING MAINLY DRY OVERNIGHT.

STRONG AND MOIST ZONAL FLOW ALOFT WILL CONTINUE ON SUNDAY. FAST-
MOVING DISTURBANCES EMBEDDED IN THIS FLOW WILL RESULT IN LOCALLY
HEAVY SHOWERS ON THE WEST FACING SLOPES OF THE CASCADES. THE SNOW
LEVEL SHOULD BE MAINLY IN THE 4000 TO 5000 FOOT RANGE DURING THE
DAY...SO EXPECT THE PRECIP TO FALL MAINLY AS SNOW ABOVE THE 4000
FOOT LEVEL. IN FACT...IT LOOKS LIKE A WINTER WEATHER ADVISORY WILL
BE NEEDED FOR THE CASCADES FOR SUNDAY AS AMOUNTS COULD END UP IN
THE 6 TO 11 INCH RANGE...ESPECIALLY IN THE CENTRAL CASCADES.

EXPECT A GRADUAL DRYING TREND SUNDAY NIGHT DUE TO AN UPPER RIDGE
BUILDING OVER THE REGION. THIS RIDGE WILL PREVAIL OVER THE AREA ON
MON FOR DRY CONDITIONS ACROSS MUCH OF THE CWA.

MODELS SHOWED THE RIDGE FLATTENING ON TUE WITH A BAROCLINIC ZONE
SAGGING SOUTH OVER THE CWA DURING THE DAY. 33/05

.LONG TERM FROM THE PREVIOUS DISCUSSION...
A COOL UPPER LEVEL TROUGH WILL CUT THROUGH WESTERN WA ON WEDNESDAY
FOR COOLER WEATHER AND MORE SHOWERS. SNOW LEVELS WILL DROP TO
AROUND 2000 FT. DRY NORTHERLY FLOW WILL PREVAIL ON CHRISTMAS DAY
FOR MAINLY DRY WEATHER...WITH JUST ISOLATED SHOWERS IN THE CASCADES.
THIS PATTERN WILL CONTINUE INTO FRIDAY. MODELS THEN SHOW ANOTHER
COOL UPPER TROUGH CROSSING THE PAC NW ON SATURDAY...WITH SHOWERS
LINGERING INTO SUN. 33

&&

.HYDROLOGY...
A FLOOD WARNING WAS ISSUED FOR THE SKOKOMISH RIVER LATE IN THE
AFTERNOON. THE RIVER WAS STILL RISING AND WAS AT 16.9 FEET AROUND
915 PM PST. OTHER RIVERS SUCH AS THE ELWHA WERE SHOWING SHARP
RISES. A FLOOD WATCH REMAINS IN EFFECT FOR MUCH OF THE RIVERS
DRAINING OFF THE OLYMPICS AND CENTRAL CASCADES THROUGH LATE SUNDAY
NIGHT.

SNOW LEVELS ALSO ROSE THIS EVENING...WITH THE SNOW CHANGING OVER
TO RAIN ABOVE THE 3000 FOOT LEVEL. A MILDER AIR MASS ALONG WITH
STRONG UPSLOPE FLOW WILL RESULT IN LOCALLY HEAVY SHOWERS AT
TIMES...MAINLY ON THE CASCADES...THROUGH SUNDAY. THE MODELS
INDICATED AN ADDITIONAL 1-2 INCHES OF PRECIP WILL FALL ON THE
CASCADES OVERNIGHT INTO SUNDAY MORNING. HOWEVER THE SNOW LEVELS
WILL LOWER INTO THE 4500 TO 5500 FOOT RANGE BY SUNDAY MORNING...SO
SOME OF THIS PRECIP WILL BE IN THE FORM OF SNOW.

THE RIVERS THAT DO EXPERIENCE FLOODING SHOULD CREST DURING THE
DAY SUNDAY...SUNDAY NIGHT AT THE LATEST.

FLOODING IS NOT EXPECTED MON THROUGH SATURDAY.

&&

.AVIATION...STRONG WESTERLY FLOW ALOFT WILL PREVAIL TONIGHT AND
SUNDAY. STRONG ONSHORE FLOW AT THE SURFACE WILL START TO EASE LATER
SUNDAY. THE AIR MASS WILL BE MOIST AND STABLE. LOW CLOUDS TONIGHT.
CEILINGS SHOULD LIFT A LITTLE DURING THE DAY ON SUNDAY.

KSEA...LOW CLOUDS. CEILINGS LIFTING A BIT SUNDAY AFTERNOON.
SOUTHERLY WIND 15G30KT...EASING A BIT SUNDAY AFTERNOON. SCHNEIDER

&&

.MARINE...A STRONG FRONTAL SYSTEM WILL MOVE ONSHORE TONIGHT...
BRINGING GALES TO MOST WATERS. SUNDAY WILL BE A POST-FRONTAL DAY WITH
ONSHORE FLOW EASING SUNDAY NIGHT AND MONDAY. HIGH PRESSURE WILL
BUILD OVER THE AREA ON MONDAY. A WEAKER FRONTAL SYSTEM WILL ARRIVE
AROUND TUESDAY. SCHNEIDER

&&

.SEW WATCHES/WARNINGS/ADVISORIES...
WA...FLOOD WARNINGS OR WATCHES ARE IN EFFECT FOR MUCH OF THE CWA.

PZ...GALE WARNINGS ARE IN EFFECT FOR THE COASTAL WATERS...STRAIT
     OF JUAN DE FUCA...AND NORTHERN INLAND WATERS.

     SMALL CRAFT ADVISORIES ARE IN EFFECT FOR THE REMAINING
     WATERS.

     SMALL CRAFT ADVISORY FOR ROUGH BAR IN EFFECT TIL 6 PM SUNDAY
     FOR THE GRAYS HARBOR BAR.

&&

$$

WWW.WEATHER.GOV/SEATTLE

YOU CAN SEE AN ILLUSTRATED VERSION OF THIS FORECAST DISCUSSION AT
WWW.WEATHER.GOV/SEATTLE/GAFD/LATEST_WEBAFD.HTML






000
FXUS66 KSEW 202322
AFDSEW

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SEATTLE WA
330 PM PST SAT DEC 20 2014

.SYNOPSIS...STRONG MOIST FLOW WILL CONTINUE TONIGHT AND SUNDAY FOR
RAIN AT TIMES. AN UPPER LEVEL RIDGE WILL BUILD OVER THE REGION
MONDAY FOR DRIER WEATHER. A COLD FRONT WILL SLIDE SOUTHEAST THROUGH
THE AREA ON TUESDAY. A COOL UPPER TROUGH WILL CROSS WESTERN
WASHINGTON ON WEDNESDAY. DRY NORTHERLY FLOW WILL PREVAIL ON
CHRISTMAS DAY.

&&

.SHORT TERM...WARMER AIR WILL SURGE INLAND THIS AFTERNOON AND
EVENING WITH SNOW LEVELS RISING TO 5000-7000 FT. SNOW WILL CHANGE
OVER TO RAIN IN THE PASSES. STRONG WESTERLY FLOW WILL PREVAIL
TONIGHT WITH HEAVY RAIN CONTINUING IN THE MOUNTAINS. THIS WILL LEAD
TO POSSIBLE RIVER FLOODING AND A FLOOD WATCH REMAINS IN EFFECT.
WHATCOM AND SKAGIT COUNTIES WERE DROPPED FROM THE WATCH AS PRECIP
AMOUNTS ARE NOT HIGH ENOUGH TO FORCE FLOODING. MODELS SHOW SEATTLE
IN THE RAIN SHADOW TONIGHT DUE TO WESTERLY DOWNSLOPE FLOW OFF THE
OLYMPICS...RAINFALL TOTALS WILL BE LIGHT IF ANYTHING.

STRONG WESTERLY UPSLOPE FLOW WILL CONTINUE ON SUN WITH MORE HEAVY
RAIN ACROSS THE WEST SLOPES OF THE MOUNTAINS...THE THREAT OF RIVER
FLOODING WILL CONTINUE. AN UPPER LEVEL RIDGE WILL THEN BUILD INLAND
SUN NIGHT WITH HEAVY PRECIP TAPERING OFF. THE RIDGE WILL REMAIN IN
PLACE ON MON FOR DRIER WEATHER.

MODELS SHOW THE RIDGE FLATTENING ON TUE WHILE A BAROCLINIC ZONE SITS
OVER NW WA AND SOUTHERN B.C. THIS SYSTEM MAY BRING MORE RAIN TO THE
NORTH COAST...OLYMPICS AND NORTH CASCADES. THIS BAROCLINIC ZONE WILL
THEN SLOWLY SHIFT S/SE TUE NIGHT AS AN UPPER LEVEL TROUGH DIGS
OFFSHORE. 33

.LONG TERM...A COOL UPPER LEVEL TROUGH WILL CUT THROUGH WESTERN WA
ON WEDNESDAY FOR COOLER WEATHER AND MORE SHOWERS. SNOW LEVELS WILL
DROP TO AROUND 2000 FT. DRY NORTHERLY FLOW WILL PREVAIL ON CHRISTMAS
DAY FOR MAINLY DRY WEATHER...WITH JUST ISOLATED SHOWERS IN THE
CASCADES. THIS PATTERN WILL CONTINUE INTO FRIDAY. MODELS THEN SHOW
ANOTHER COOL UPPER TROUGH CROSSING THE PAC NW ON SATURDAY...WITH
SHOWERS LINGERING INTO SUN. 33

&&

.HYDROLOGY...A FLOOD WATCH REMAINS IN EFFECT FOR THE RIVERS FLOWING
OFF THE OLYMPICS AND THE CASCADES FROM LEWIS TO SNOHOMISH COUNTIES.
THE FLOOD WATCH WAS CANCELLED FOR WHATCOM AND SKAGIT COUNTIES AS
PRECIP AMOUNTS ARE NOT HIGH ENOUGH TO FORCE RIVER FLOODING.

MODELS SHOW AN ADDITIONAL 1 TO 3 INCHES OF PRECIP TONIGHT THROUGH
SUN AFTERNOON IN THE OLYMPICS AND CASCADES...MAINLY FROM LEWIS TO
SNOHOMISH COUNTIES. A BULLSEYE OF 5 INCHES IS POSSIBLE OVER MT
RAINIER. THIS AMOUNT OF RAIN IS GREAT ENOUGH TO CAUSE FLOODING ON
SOME OF THE RIVERS FLOWING OFF THE OLYMPICS AND CASCADES.

ANY FLOODING WOULD LIKELY BEGIN AS EARLY AS LATE THIS AFTERNOON OR
EVENING ON THE SKOKOMISH RIVER. THE CASCADE RIVERS COULD FLOOD
TONIGHT OR SUNDAY. MODELS SHOW HEAVY RAIN ENDING SUNDAY NIGHT.

&&

.AVIATION...STRONG WESTERLY FLOW ALOFT WILL CONTINUE TONIGHT AND
SUNDAY. AT THE SURFACE STRONG ONSHORE FLOW WILL DEVELOP TONIGHT. THE
AIR MASS WILL REMAIN MOIST AND STABLE. BY SUNDAY AFTERNOON THE
FRONTAL SYSTEM OVER THE AREA WILL WEAKEN AND SURFACE HIGH PRES WILL
BUILD SUNDAY NIGHT.

CEILINGS ARE GENERALLY MVFR. LOW END MVFR VISIBILITY RESTRICTIONS IN
RAIN ARE WIDESPREAD. THE MOUNTAINS AND FOOTHILLS WILL BE OBSCURED
TONIGHT. SOME IFR CONDITIONS ARE LIKELY OVERNIGHT. IMPROVEMENT IS
LIKELY SUNDAY AFTERNOON.

KSEA...RAIN WILL CONTINUE WITH MVFR CONDITIONS. SOUTHWEST WIND WILL
INCREASE TO 12G22KT THIS EVENING AND CONTINUE OVERNIGHT. CHB

&&

.MARINE...A STRONG SYSTEM WILL CONTINUE MOVING THROUGH WESTERN
WASHINGTON TONIGHT. GALE SOUTHEAST WINDS HAVE ALREADY SWITCHED TO
SOUTHWEST OVER THE COAST. THE SWITCH WILL OCCUR OVER THE INLAND
WATERS THIS EVENING. THE STRAIT AND NORTHERN INLAND WATERS WILL HAVE
GALES WHILE ADMIRALTY INLET AND PUGET SOUND WILL HAVE SMALL CRAFT
ADVISORY STRENGTH WINDS.

SWELLS HAVE SUBSIDED BELOW 15 FEET ON THE COAST SO BOTH THE HIGH
SURF ADVISORY AND THE COASTAL FLOOD ADVISORY HAVE ENDED.

SUNDAY SHOULD BE A POSTFRONTAL DAY WITH ONSHORE FLOW EASING SUNDAY
NIGHT AND MONDAY. A RIDGE OF HIGH PRES WILL BUILD OVER THE AREA ON
MONDAY. A WEAKER SYSTEM WILL ARRIVE AROUND TUESDAY. CHB

&&

.SEW WATCHES/WARNINGS/ADVISORIES...

WA...FLOOD WATCH IN EFFECT FOR PORTIONS OF WESTERN WA.
     WINTER WEATHER ADVISORY CASCADES UNTIL 4 PM THIS AFTERNOON.

PZ...GALE WARNING COAST...STRAIT...NORTHERN INLAND WATERS.
     SMALL CRAFT ADVISORY ADMIRALTY INLET AND PUGET SOUND AND HOOD
     CANAL.
     SMALL CRAFT ADVISORY FOR SEVERE CONDITIONS GRAYS HARBOR BAR.

&&

$$

YOU CAN SEE AN ILLUSTRATED VERSION OF THIS FORECAST DISCUSSION AT
WWW.WEATHER.GOV/SEATTLE/GAFD/LATEST_WEBAFD.HTML






000
FXUS66 KSEW 202322
AFDSEW

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SEATTLE WA
330 PM PST SAT DEC 20 2014

.SYNOPSIS...STRONG MOIST FLOW WILL CONTINUE TONIGHT AND SUNDAY FOR
RAIN AT TIMES. AN UPPER LEVEL RIDGE WILL BUILD OVER THE REGION
MONDAY FOR DRIER WEATHER. A COLD FRONT WILL SLIDE SOUTHEAST THROUGH
THE AREA ON TUESDAY. A COOL UPPER TROUGH WILL CROSS WESTERN
WASHINGTON ON WEDNESDAY. DRY NORTHERLY FLOW WILL PREVAIL ON
CHRISTMAS DAY.

&&

.SHORT TERM...WARMER AIR WILL SURGE INLAND THIS AFTERNOON AND
EVENING WITH SNOW LEVELS RISING TO 5000-7000 FT. SNOW WILL CHANGE
OVER TO RAIN IN THE PASSES. STRONG WESTERLY FLOW WILL PREVAIL
TONIGHT WITH HEAVY RAIN CONTINUING IN THE MOUNTAINS. THIS WILL LEAD
TO POSSIBLE RIVER FLOODING AND A FLOOD WATCH REMAINS IN EFFECT.
WHATCOM AND SKAGIT COUNTIES WERE DROPPED FROM THE WATCH AS PRECIP
AMOUNTS ARE NOT HIGH ENOUGH TO FORCE FLOODING. MODELS SHOW SEATTLE
IN THE RAIN SHADOW TONIGHT DUE TO WESTERLY DOWNSLOPE FLOW OFF THE
OLYMPICS...RAINFALL TOTALS WILL BE LIGHT IF ANYTHING.

STRONG WESTERLY UPSLOPE FLOW WILL CONTINUE ON SUN WITH MORE HEAVY
RAIN ACROSS THE WEST SLOPES OF THE MOUNTAINS...THE THREAT OF RIVER
FLOODING WILL CONTINUE. AN UPPER LEVEL RIDGE WILL THEN BUILD INLAND
SUN NIGHT WITH HEAVY PRECIP TAPERING OFF. THE RIDGE WILL REMAIN IN
PLACE ON MON FOR DRIER WEATHER.

MODELS SHOW THE RIDGE FLATTENING ON TUE WHILE A BAROCLINIC ZONE SITS
OVER NW WA AND SOUTHERN B.C. THIS SYSTEM MAY BRING MORE RAIN TO THE
NORTH COAST...OLYMPICS AND NORTH CASCADES. THIS BAROCLINIC ZONE WILL
THEN SLOWLY SHIFT S/SE TUE NIGHT AS AN UPPER LEVEL TROUGH DIGS
OFFSHORE. 33

.LONG TERM...A COOL UPPER LEVEL TROUGH WILL CUT THROUGH WESTERN WA
ON WEDNESDAY FOR COOLER WEATHER AND MORE SHOWERS. SNOW LEVELS WILL
DROP TO AROUND 2000 FT. DRY NORTHERLY FLOW WILL PREVAIL ON CHRISTMAS
DAY FOR MAINLY DRY WEATHER...WITH JUST ISOLATED SHOWERS IN THE
CASCADES. THIS PATTERN WILL CONTINUE INTO FRIDAY. MODELS THEN SHOW
ANOTHER COOL UPPER TROUGH CROSSING THE PAC NW ON SATURDAY...WITH
SHOWERS LINGERING INTO SUN. 33

&&

.HYDROLOGY...A FLOOD WATCH REMAINS IN EFFECT FOR THE RIVERS FLOWING
OFF THE OLYMPICS AND THE CASCADES FROM LEWIS TO SNOHOMISH COUNTIES.
THE FLOOD WATCH WAS CANCELLED FOR WHATCOM AND SKAGIT COUNTIES AS
PRECIP AMOUNTS ARE NOT HIGH ENOUGH TO FORCE RIVER FLOODING.

MODELS SHOW AN ADDITIONAL 1 TO 3 INCHES OF PRECIP TONIGHT THROUGH
SUN AFTERNOON IN THE OLYMPICS AND CASCADES...MAINLY FROM LEWIS TO
SNOHOMISH COUNTIES. A BULLSEYE OF 5 INCHES IS POSSIBLE OVER MT
RAINIER. THIS AMOUNT OF RAIN IS GREAT ENOUGH TO CAUSE FLOODING ON
SOME OF THE RIVERS FLOWING OFF THE OLYMPICS AND CASCADES.

ANY FLOODING WOULD LIKELY BEGIN AS EARLY AS LATE THIS AFTERNOON OR
EVENING ON THE SKOKOMISH RIVER. THE CASCADE RIVERS COULD FLOOD
TONIGHT OR SUNDAY. MODELS SHOW HEAVY RAIN ENDING SUNDAY NIGHT.

&&

.AVIATION...STRONG WESTERLY FLOW ALOFT WILL CONTINUE TONIGHT AND
SUNDAY. AT THE SURFACE STRONG ONSHORE FLOW WILL DEVELOP TONIGHT. THE
AIR MASS WILL REMAIN MOIST AND STABLE. BY SUNDAY AFTERNOON THE
FRONTAL SYSTEM OVER THE AREA WILL WEAKEN AND SURFACE HIGH PRES WILL
BUILD SUNDAY NIGHT.

CEILINGS ARE GENERALLY MVFR. LOW END MVFR VISIBILITY RESTRICTIONS IN
RAIN ARE WIDESPREAD. THE MOUNTAINS AND FOOTHILLS WILL BE OBSCURED
TONIGHT. SOME IFR CONDITIONS ARE LIKELY OVERNIGHT. IMPROVEMENT IS
LIKELY SUNDAY AFTERNOON.

KSEA...RAIN WILL CONTINUE WITH MVFR CONDITIONS. SOUTHWEST WIND WILL
INCREASE TO 12G22KT THIS EVENING AND CONTINUE OVERNIGHT. CHB

&&

.MARINE...A STRONG SYSTEM WILL CONTINUE MOVING THROUGH WESTERN
WASHINGTON TONIGHT. GALE SOUTHEAST WINDS HAVE ALREADY SWITCHED TO
SOUTHWEST OVER THE COAST. THE SWITCH WILL OCCUR OVER THE INLAND
WATERS THIS EVENING. THE STRAIT AND NORTHERN INLAND WATERS WILL HAVE
GALES WHILE ADMIRALTY INLET AND PUGET SOUND WILL HAVE SMALL CRAFT
ADVISORY STRENGTH WINDS.

SWELLS HAVE SUBSIDED BELOW 15 FEET ON THE COAST SO BOTH THE HIGH
SURF ADVISORY AND THE COASTAL FLOOD ADVISORY HAVE ENDED.

SUNDAY SHOULD BE A POSTFRONTAL DAY WITH ONSHORE FLOW EASING SUNDAY
NIGHT AND MONDAY. A RIDGE OF HIGH PRES WILL BUILD OVER THE AREA ON
MONDAY. A WEAKER SYSTEM WILL ARRIVE AROUND TUESDAY. CHB

&&

.SEW WATCHES/WARNINGS/ADVISORIES...

WA...FLOOD WATCH IN EFFECT FOR PORTIONS OF WESTERN WA.
     WINTER WEATHER ADVISORY CASCADES UNTIL 4 PM THIS AFTERNOON.

PZ...GALE WARNING COAST...STRAIT...NORTHERN INLAND WATERS.
     SMALL CRAFT ADVISORY ADMIRALTY INLET AND PUGET SOUND AND HOOD
     CANAL.
     SMALL CRAFT ADVISORY FOR SEVERE CONDITIONS GRAYS HARBOR BAR.

&&

$$

YOU CAN SEE AN ILLUSTRATED VERSION OF THIS FORECAST DISCUSSION AT
WWW.WEATHER.GOV/SEATTLE/GAFD/LATEST_WEBAFD.HTML







000
FXUS66 KSEW 201722
AFDSEW

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SEATTLE WA
930 AM PST SAT DEC 20 2014

.SYNOPSIS...A WARM FRONT WILL MOVE ACROSS WESTERN WASHINGTON TODAY.
STRONG MOIST WEST FLOW ALOFT WILL FOLLOW TONIGHT AND SUNDAY. THIS
WILL BRING WET AND WINDY CONDITIONS TO THE LOWLANDS AND HEAVY RAIN
OVER THE MOUNTAINS. AN UPPER LEVEL RIDGE WILL BUILD OVER THE REGION
MONDAY FOR DRIER WEATHER. THE RIDGE WILL WEAKEN MONDAY NIGHT
ALLOWING A COUPLE OF WEATHER SYSTEMS TO REACH THE AREA THROUGH MID
NEXT WEEK.

&&

.SHORT TERM...A STRONG WARM FRONT WILL MOVE INLAND TODAY FOR MORE
RAIN AND HEAVY MOUNTAIN PRECIP. HIGH WIND IS MARGINAL OVER THE NORTH
INTERIOR AND WILL LET THE WARNING CONTINUE THROUGH NOON TODAY. WA
DOT SHOWS SNOW IN THE PASSES THIS MORNING AND A WINTER WEATHER
ADVISORY REMAINS IN EFFECT. THE SNOW LEVELS WILL RISE TO 5000-6000
FT THIS AFTERNOON AS WARMER AIR MOVES INLAND...WITH SNOW CHANGING
OVER TO RAIN IN THE PASSES. STRONG PERSISTENT WESTERLY FLOW WILL
PREVAIL TONIGHT WITH HEAVY RAIN CONTINUING IN THE MOUNTAINS. THIS
WILL LEAD TO POSSIBLE RIVER FLOODING AND A FLOOD WATCH REMAINS IN
EFFECT. MODELS SHOW SEATTLE IN THE RAIN SHADOW TONIGHT DUE TO
WESTERLY DOWNSLOPE FLOW OFF THE OLYMPICS...RAINFALL TOTALS WILL BE
LIGHT IF ANYTHING.

STRONG WESTERLY UPSLOPE FLOW WILL CONTINUE ON SUN WITH MORE HEAVY
RAIN ACROSS THE WEST SLOPES OF THE MOUNTAINS. AN UPPER LEVEL RIDGE
WILL THEN BUILD INLAND SUN NIGHT WITH HEAVY PRECIP TAPERING OFF. THE
RIDGE WILL REMAIN IN PLACE ON MON FOR DRIER WEATHER. 33

.LONG TERM...PREVIOUS DISCUSSION...MODEL SOLUTIONS REMAIN IN FLUX
FROM TUESDAY ONWARD. ONCE AGAIN THE LATEST GFS AND ECMWF SOLUTIONS
ARE IN FAIR AGREEMENT...BUT THE SOLUTIONS KEEP CHANGING WITH EACH
NEW RUN. THE WEATHER PATTERN WILL REMAIN ACTIVE NEXT WEEK...BUT NOT
AS WET AND WINDY AS THIS WEEKEND. THE LATEST SOLUTIONS FLATTEN THE
MONDAY RIDGE...ALLOWING WARM ADVECTION RAIN TO CREEP THROUGH IT AND
OVER W WA ON TUESDAY. A NORMAL STRENGTH FRONTAL SYSTEM CROSSES THE
AREA ON WEDNESDAY. NO SIGNIFICANT SYSTEMS SHOW UP THURSDAY AND
FRIDAY...BUT THE NW FLOW ALOFT MAY STILL BE MOIST ENOUGH TO KEEP A
CHANCE OF RAIN. CONFIDENCE REMAINS LOW. KAM

&&

.HYDROLOGY...THREE TO FIVE INCHES OF RAIN IS EXPECTED TO FALL OVER
THE OLYMPICS AND OVER THE CASCADES FROM SNOHOMISH THROUGH LEWIS
COUNTIES. A BULLSEYE OF SEVEN INCHES IS POSSIBLE OVER MT RAINIER.
THIS AMOUNT OF RAIN IS GREAT ENOUGH TO CAUSE FLOODING ON SOME OF THE
RIVERS FLOWING OFF THE OLYMPICS AND CASCADES. A FLOOD WATCH REMAINS
IN EFFECT. LESS PRECIP IS FORECAST OVER THE CASCADES OF WHATCOM AND
SKAGIT COUNTIES WITH TWO TO FOUR INCHES...THE FLOOD THREAT IS LESS
OVERALL.

PRECIPITATION IS STARTING AS SNOW OVER THE CASCADES THIS MORNING BUT
SNOW LEVELS WILL RISE RAPIDLY...TO 5000 TO 7000 FEET THIS AFTERNOON
AND EVENING. THE HEAVIEST RAIN WILL BE OVER THE OLYMPICS TODAY AND
TONIGHT...AND OVER THE CASCADES FROM LATE THIS AFTERNOON THROUGH
SUNDAY MORNING.

ANY FLOODING WOULD LIKELY BEGIN AS EARLY AS LATE THIS AFTERNOON OR
EVENING ON THE SKOKOMISH RIVER. THE CASCADE RIVERS COULD FLOOD
TONIGHT OR SUNDAY. MODELS SHOW HEAVY RAIN ENDING SUNDAY NIGHT.

&&

.AVIATION...A STRONG FRONTAL SYSTEM WILL MOVE THROUGH WESTERN
WASHINGTON TODAY AND TONIGHT WITH WESTERLY FLOW ALOFT. AT THE
SURFACE STRONG SOUTHEAST GRADIENTS TODAY WILL TURN ONSHORE TONIGHT.
THE AIR MASS WILL BE MOIST AND STABLE WITH WIDESPREAD RAIN.

CEILINGS ARE GENERALLY AROUND 3K FT THIS MORNING WITH VISIBILITY
RESTRICTIONS TO 2SM IN RAIN AT TIMES. THERE MIGHT BE A FEW HOURS OF
IMPROVEMENT EARLY THIS AFTERNOON...WITH SOME 4-5K FT CEILINGS...BUT
CONDITIONS WILL DETERIORATE LATE THIS AFTERNOON AND EVENING. THE
MOUNTAINS AND FOOTHILLS WILL BE OBSCURED.

KSEA...RAIN AND AN INCREASING SOUTHERLY WIND OF 12G22KT LATER TODAY
WITH THE PASSAGE OF A SECOND FRONTAL WAVE. CHB

&&

.MARINE...A STRONG SYSTEM WILL MOVE THROUGH WESTERN WASHINGTON TODAY
AND TONIGHT. GALE SOUTHEAST WINDS WILL SWITCH TO SOUTHWEST OVER THE
COAST THIS AFTERNOON. OVER THE INLAND WATERS GALE SOUTHEAST WINDS
WILL BECOME SMALL CRAFT ADVISORY STRENGTH SOUTHWEST WINDS. SEAS OVER
THE COASTAL WATERS WILL BE AROUND 20 FEET TODAY. THERE IS A HIGH
SURF ADVISORY FOR THE COASTAL BEACHES THROUGH TODAY AND A COASTAL
FLOOD ADVISORY FOR MINOR FLOODING OF LOW AREAS NEAR THE BEACHES
DURING THE TIME OF HIGH TIDE THIS MORNING.

SUNDAY SHOULD BE A POSTFRONTAL DAY WITH STRONG ONSHORE FLOW EASING
SUNDAY NIGHT AND MONDAY. A RIDGE OF HIGH PRES WILL BUILD OVER THE
AREA ON MONDAY. A WEAKER SYSTEM WILL ARRIVE AROUND TUESDAY. CHB

&&

.SEW WATCHES/WARNINGS/ADVISORIES...

WA...FLOOD WATCHES IN EFFECT FOR PORTIONS OF WESTERN WA.
     HIGH WIND WARNING WESTERN WHATCOM...SAN JUAN
     ISLANDS..ADMIRALTY INLET.
     WIND ADVISORY WESTERN SKAGIT COUNTY.
     WINTER WEATHER ADVISORY CASCADES.
     HIGH SURF ADVISORY NORTH AND CENTRAL COAST.
     COASTAL FLOOD ADVISORY NORTH AND CENTRAL COAST SATURDAY MORNING.

PZ...GALE WARNING COAST...STRAIT...NORTHERN INLAND WATERS.
     SMALL CRAFT ADVISORY ADMIRALTY INLET AND PUGET SOUND AND HOOD
     CANAL.
     SMALL CRAFT ADVISORY FOR SEVERE CONDITIONS GRAYS HARBOR BAR.

&&

$$

YOU CAN SEE AN ILLUSTRATED VERSION OF THIS FORECAST DISCUSSION AT
WWW.WEATHER.GOV/SEATTLE/GAFD/LATEST_WEBAFD.HTML







000
FXUS66 KSEW 201722
AFDSEW

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SEATTLE WA
930 AM PST SAT DEC 20 2014

.SYNOPSIS...A WARM FRONT WILL MOVE ACROSS WESTERN WASHINGTON TODAY.
STRONG MOIST WEST FLOW ALOFT WILL FOLLOW TONIGHT AND SUNDAY. THIS
WILL BRING WET AND WINDY CONDITIONS TO THE LOWLANDS AND HEAVY RAIN
OVER THE MOUNTAINS. AN UPPER LEVEL RIDGE WILL BUILD OVER THE REGION
MONDAY FOR DRIER WEATHER. THE RIDGE WILL WEAKEN MONDAY NIGHT
ALLOWING A COUPLE OF WEATHER SYSTEMS TO REACH THE AREA THROUGH MID
NEXT WEEK.

&&

.SHORT TERM...A STRONG WARM FRONT WILL MOVE INLAND TODAY FOR MORE
RAIN AND HEAVY MOUNTAIN PRECIP. HIGH WIND IS MARGINAL OVER THE NORTH
INTERIOR AND WILL LET THE WARNING CONTINUE THROUGH NOON TODAY. WA
DOT SHOWS SNOW IN THE PASSES THIS MORNING AND A WINTER WEATHER
ADVISORY REMAINS IN EFFECT. THE SNOW LEVELS WILL RISE TO 5000-6000
FT THIS AFTERNOON AS WARMER AIR MOVES INLAND...WITH SNOW CHANGING
OVER TO RAIN IN THE PASSES. STRONG PERSISTENT WESTERLY FLOW WILL
PREVAIL TONIGHT WITH HEAVY RAIN CONTINUING IN THE MOUNTAINS. THIS
WILL LEAD TO POSSIBLE RIVER FLOODING AND A FLOOD WATCH REMAINS IN
EFFECT. MODELS SHOW SEATTLE IN THE RAIN SHADOW TONIGHT DUE TO
WESTERLY DOWNSLOPE FLOW OFF THE OLYMPICS...RAINFALL TOTALS WILL BE
LIGHT IF ANYTHING.

STRONG WESTERLY UPSLOPE FLOW WILL CONTINUE ON SUN WITH MORE HEAVY
RAIN ACROSS THE WEST SLOPES OF THE MOUNTAINS. AN UPPER LEVEL RIDGE
WILL THEN BUILD INLAND SUN NIGHT WITH HEAVY PRECIP TAPERING OFF. THE
RIDGE WILL REMAIN IN PLACE ON MON FOR DRIER WEATHER. 33

.LONG TERM...PREVIOUS DISCUSSION...MODEL SOLUTIONS REMAIN IN FLUX
FROM TUESDAY ONWARD. ONCE AGAIN THE LATEST GFS AND ECMWF SOLUTIONS
ARE IN FAIR AGREEMENT...BUT THE SOLUTIONS KEEP CHANGING WITH EACH
NEW RUN. THE WEATHER PATTERN WILL REMAIN ACTIVE NEXT WEEK...BUT NOT
AS WET AND WINDY AS THIS WEEKEND. THE LATEST SOLUTIONS FLATTEN THE
MONDAY RIDGE...ALLOWING WARM ADVECTION RAIN TO CREEP THROUGH IT AND
OVER W WA ON TUESDAY. A NORMAL STRENGTH FRONTAL SYSTEM CROSSES THE
AREA ON WEDNESDAY. NO SIGNIFICANT SYSTEMS SHOW UP THURSDAY AND
FRIDAY...BUT THE NW FLOW ALOFT MAY STILL BE MOIST ENOUGH TO KEEP A
CHANCE OF RAIN. CONFIDENCE REMAINS LOW. KAM

&&

.HYDROLOGY...THREE TO FIVE INCHES OF RAIN IS EXPECTED TO FALL OVER
THE OLYMPICS AND OVER THE CASCADES FROM SNOHOMISH THROUGH LEWIS
COUNTIES. A BULLSEYE OF SEVEN INCHES IS POSSIBLE OVER MT RAINIER.
THIS AMOUNT OF RAIN IS GREAT ENOUGH TO CAUSE FLOODING ON SOME OF THE
RIVERS FLOWING OFF THE OLYMPICS AND CASCADES. A FLOOD WATCH REMAINS
IN EFFECT. LESS PRECIP IS FORECAST OVER THE CASCADES OF WHATCOM AND
SKAGIT COUNTIES WITH TWO TO FOUR INCHES...THE FLOOD THREAT IS LESS
OVERALL.

PRECIPITATION IS STARTING AS SNOW OVER THE CASCADES THIS MORNING BUT
SNOW LEVELS WILL RISE RAPIDLY...TO 5000 TO 7000 FEET THIS AFTERNOON
AND EVENING. THE HEAVIEST RAIN WILL BE OVER THE OLYMPICS TODAY AND
TONIGHT...AND OVER THE CASCADES FROM LATE THIS AFTERNOON THROUGH
SUNDAY MORNING.

ANY FLOODING WOULD LIKELY BEGIN AS EARLY AS LATE THIS AFTERNOON OR
EVENING ON THE SKOKOMISH RIVER. THE CASCADE RIVERS COULD FLOOD
TONIGHT OR SUNDAY. MODELS SHOW HEAVY RAIN ENDING SUNDAY NIGHT.

&&

.AVIATION...A STRONG FRONTAL SYSTEM WILL MOVE THROUGH WESTERN
WASHINGTON TODAY AND TONIGHT WITH WESTERLY FLOW ALOFT. AT THE
SURFACE STRONG SOUTHEAST GRADIENTS TODAY WILL TURN ONSHORE TONIGHT.
THE AIR MASS WILL BE MOIST AND STABLE WITH WIDESPREAD RAIN.

CEILINGS ARE GENERALLY AROUND 3K FT THIS MORNING WITH VISIBILITY
RESTRICTIONS TO 2SM IN RAIN AT TIMES. THERE MIGHT BE A FEW HOURS OF
IMPROVEMENT EARLY THIS AFTERNOON...WITH SOME 4-5K FT CEILINGS...BUT
CONDITIONS WILL DETERIORATE LATE THIS AFTERNOON AND EVENING. THE
MOUNTAINS AND FOOTHILLS WILL BE OBSCURED.

KSEA...RAIN AND AN INCREASING SOUTHERLY WIND OF 12G22KT LATER TODAY
WITH THE PASSAGE OF A SECOND FRONTAL WAVE. CHB

&&

.MARINE...A STRONG SYSTEM WILL MOVE THROUGH WESTERN WASHINGTON TODAY
AND TONIGHT. GALE SOUTHEAST WINDS WILL SWITCH TO SOUTHWEST OVER THE
COAST THIS AFTERNOON. OVER THE INLAND WATERS GALE SOUTHEAST WINDS
WILL BECOME SMALL CRAFT ADVISORY STRENGTH SOUTHWEST WINDS. SEAS OVER
THE COASTAL WATERS WILL BE AROUND 20 FEET TODAY. THERE IS A HIGH
SURF ADVISORY FOR THE COASTAL BEACHES THROUGH TODAY AND A COASTAL
FLOOD ADVISORY FOR MINOR FLOODING OF LOW AREAS NEAR THE BEACHES
DURING THE TIME OF HIGH TIDE THIS MORNING.

SUNDAY SHOULD BE A POSTFRONTAL DAY WITH STRONG ONSHORE FLOW EASING
SUNDAY NIGHT AND MONDAY. A RIDGE OF HIGH PRES WILL BUILD OVER THE
AREA ON MONDAY. A WEAKER SYSTEM WILL ARRIVE AROUND TUESDAY. CHB

&&

.SEW WATCHES/WARNINGS/ADVISORIES...

WA...FLOOD WATCHES IN EFFECT FOR PORTIONS OF WESTERN WA.
     HIGH WIND WARNING WESTERN WHATCOM...SAN JUAN
     ISLANDS..ADMIRALTY INLET.
     WIND ADVISORY WESTERN SKAGIT COUNTY.
     WINTER WEATHER ADVISORY CASCADES.
     HIGH SURF ADVISORY NORTH AND CENTRAL COAST.
     COASTAL FLOOD ADVISORY NORTH AND CENTRAL COAST SATURDAY MORNING.

PZ...GALE WARNING COAST...STRAIT...NORTHERN INLAND WATERS.
     SMALL CRAFT ADVISORY ADMIRALTY INLET AND PUGET SOUND AND HOOD
     CANAL.
     SMALL CRAFT ADVISORY FOR SEVERE CONDITIONS GRAYS HARBOR BAR.

&&

$$

YOU CAN SEE AN ILLUSTRATED VERSION OF THIS FORECAST DISCUSSION AT
WWW.WEATHER.GOV/SEATTLE/GAFD/LATEST_WEBAFD.HTML






000
FXUS66 KSEW 201200
AFDSEW

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SEATTLE WA
400 AM PST SAT DEC 20 2014

.SYNOPSIS...TWO STRONG WARM FRONTS WILL MOVE ACROSS WESTERN
WASHINGTON EARLY THIS MORNING AND LATE THIS AFTERNOON. STRONG MOIST
WEST FLOW ALOFT WILL FOLLOW TONIGHT AND SUNDAY. THIS WILL BRING WET
AND WINDY CONDITIONS TO THE LOWLANDS AND HEAVY RAIN OVER THE
MOUNTAINS. AN UPPER LEVEL RIDGE WILL BUILD OVER THE REGION MONDAY
FOR DRIER WEATHER. THE RIDGE WILL WEAKEN MONDAY NIGHT ALLOWING A
COUPLE OF WEATHER SYSTEMS TO REACH THE AREA THROUGH MID NEXT WEEK.

&&

.SHORT TERM...STRONG ZONAL FLOW ACROSS THE NE PACIFIC PUMPED UP BY A
170 KT JETSTREAK WILL DRIVE A PLUME OF WARM MOIST AIR OVER W WA THIS
WEEKEND. MODELS HAVE BEEN GENERALLY CONSISTENT. A STRONG WARM FRONT
WILL MOVE ACROSS W WA EARLY THIS MORNING...WITH STRONG S FLOW ALOFT
AHEAD OF THE WARM FRONT CRANKING UP HEAVY RAIN OVER THE OLYMPICS.
RADAR SHOWS HEAVY RAIN BEGINNING TO REACH THE COAST AND OLYMPICS AT
11Z WITH LIGHT RAIN OVER PUGET SOUND. SURFACE WINDS ARE RISING ALONG
THE COAST AND OVER THE N INTERIOR.

THE WARM FRONT WILL BRING THE STRONGEST WINDS TO THE COAST EARLY
THIS MORNING...AND TO THE N INTERIOR THROUGH MID MORNING...THEN
SHIFT TO SW-S AND EASE BEHIND THE WARM FRONT.

MODELS STILL HAVE A SECOND STRONG WARM FRONT REACHING THE AREA THIS
AFTERNOON...BUT THE 00Z-06Z RUNS HAVE TRENDED A LITTLE WEAKER WITH
THE SURFACE WINDS. EARLIER MODELS WITH STRONGER SOLUTIONS SHOWED A
SMALL SURFACE LOW TRACKING ACROSS VANCOUVER ISLAND BEHIND THE WARM
FRONT...BUT THE GFS NOW ONLY SHOWS AN OPEN SURFACE TROUGH AND THE
ECMWF AND NAM HAVE WEAKER SURFACE LOWS. IT NOW LOOKS LIKE SURFACE
WINDS WILL REMAIN JUST BELOW ADVISORY LEVELS THIS AFTERNOON AND
EVENING. ONE CONCERN IS THAT STRONG SW FLOW ALOFT ACROSS THE
OLYMPICS MAY ALLOW A SMALL MESO-LOW TO FORM OVER THE NE CORNER OF
THE OLYMPICS BRINGING STRONGER WINDS TO THE HOOD CANAL AND ADMIRALTY
INLET AREA. HOWEVER ONLY THE 06Z NAM SHOWS THIS. FOR NOW I WILL
STICK WITH THE PLAN...ALLOWING THE HIGH WIND WARNINGS FOR THE COAST
AND N INTERIOR TO EXPIRE AT 9 AM AND NOON RESPECTIVELY.

HEAVY PRECIPITATION IS EXPECTED TO DEVELOP OVER THE CASCADES THIS
MORNING AS LOW LEVEL WINDS SHIFT TO SW BEHIND THE WARM FRONT.
CASCADE SNOW LEVELS ARE STARTING OUT AROUND 3000 FEET...SO SOME
BRIEF HEAVY SNOW COULD DEVELOP THIS MORNING BEFORE THE WARM AIR
BEHIND THE WARM FRONT LIFTS SNOW LEVELS ABOVE CRITICAL PASS LEVELS.
PARADISE COULD SEE 6-11 INCHES OF SNOW BEFORE SNOW LEVELS RISE TO
6500 FEET AROUND MIDDAY. STEVENS PASS HAS A CHANCE AT REACHING 3-8
INCHES BY EARLY AFTERNOON...AND MOUNT BAKER COULD SEE UP TO 9 INCHES
THROUGH 4 PM. THE SNOW IS GOING TO HAVE TO RAMP UP PRETTY FAST THIS
MORNING TO MEET THESE ACCUMULATIONS...SO CONFIDENCE IN THESE SNOW
AMOUNTS IS NOT ALL THAT HIGH. THERE IS A GOOD CHANCE THAT SNOW
TOTALS WILL BE LOWER.

THE THIRD PROBLEM IS HEAVY RAIN OVER THE OLYMPICS AND CASCADES
THROUGH SUNDAY AFTERNOON. S FLOW WITH THE FIRST WARM FRONT WILL NOT
BRING MUCH SIGNIFICANT RAIN TO THE CASCADES...BUT IT WILL BRING
HEAVY RAIN TO THE OLYMPICS. LOW LEVEL WINDS WILL SHIFT TO WESTERLY
THIS AFTERNOON THEN STRENGTHEN TO 40-50 KT AT 850 MB THIS
EVENING...THEN SLOWLY EASE THROUGH SUNDAY. HEAVY RAIN WILL DEVELOP
OVER THE CASCADES...AND RAIN WILL CONTINUE TO FALL OVER THE
OLYMPICS. SNOW LEVELS WILL BE HIGH THIS AFTERNOON THROUGH SUNDAY.
THE HEAVIEST RAIN OVER THE CASCADES STILL LOOKS LIKE IT WILL BE
FROM ABOUT SNOQUALMIE PASS SOUTHWARD. THE LATEST QPF FORECAST STILL
HAS 3-5 INCHES OVER MUCH OF THE CASCADES WITH A BULLSEYE OF 7 INCHES
OVER MT RAINIER. THE OLYMPICS GET 3-4.5 INCHES THROUGH 12Z SUNDAY.

STRONG W FLOW ALOFT CONTINUES SUNDAY AFTERNOON AND NIGHT...BUT THE
MOISTURE EMBEDDED IN THE FLOW DIMINISHES...SO THE HEAVY RAIN WILL
END.

MODELS REMAIN ON TRACK BUILDING AN UPPER LEVEL RIDGE JUST OFFSHORE
ON MONDAY...WHILE A SURFACE HIGH SETTLES OVER W WA. WINDS WILL
WEAKEN AND THE AIR MASS WILL DRY...BUT THERE WILL STILL BE ENOUGH
CLOUD COVER AROUND FOR MOSTLY CLOUD SKIES. POPS OVER THE LOWLANDS
HAVE BEEN LOWERED INTO THE 20-30 RANGE...BUT IF THE MODELS KEEP IT
DRY THE CHANCE OF RAIN COULD PROBABLY BE DROPPED IN A LATER
FORECAST. KAM

.LONG TERM...MODEL SOLUTIONS REMAIN IN FLUX FROM TUESDAY ONWARD.
ONCE AGAIN THE LATEST GFS AND ECMWF SOLUTIONS ARE IN FAIR
AGREEMENT...BUT THE SOLUTIONS KEEP CHANGING WITH EACH NEW RUN. THE
WEATHER PATTERN WILL REMAIN ACTIVE NEXT WEEK...BUT NOT AS WET AND
WINDY AS THIS WEEKEND. THE LATEST SOLUTIONS FLATTEN THE MONDAY
RIDGE...ALLOWING WARM ADVECTION RAIN TO CREEP THROUGH IT AND OVER W
WA ON TUESDAY. A NORMAL STRENGTH FRONTAL SYSTEM CROSSES THE AREA ON
WEDNESDAY. NO SIGNIFICANT SYSTEMS SHOW UP THURSDAY AND FRIDAY...BUT
THE NW FLOW ALOFT MAY STILL BE MOIST ENOUGH TO KEEP A CHANCE OF
RAIN. CONFIDENCE REMAINS LOW. KAM

&&

.HYDROLOGY...STRONG MOIST W FLOW ALOFT WITH A COUPLE OF WARM FRONTS
WILL BRING HEAVY RAIN TO THE MOUNTAINS TODAY THROUGH SUNDAY. THREE
TO FIVE INCHES OF RAIN IS EXPECTED TO FALL OVER THE OLYMPICS...AND
OVER THE CASCADES FROM ROUGHLY STEVENS PASS SOUTHWARD. A BULLSEYE OF
7 INCHES IS POSSIBLE OVER MT RAINIER. THIS AMOUNT OF RAIN IS GREAT
ENOUGH TO CAUSE FLOODING ON SOME OF THE RIVERS FLOWING OFF THE
OLYMPICS AND CASCADES. A FLOOD WATCH REMAINS IN EFFECT.

PRECIPITATION WILL START AS SNOW OVER THE CASCADES THIS MORNING BUT
SNOW LEVELS WILL RISE RAPIDLY...PEAKING OUT NEAR 5500 FEET NORTH TO
7500 FEET SOUTH THIS EVENING. THE HEAVIEST RAIN WILL BE OVER THE
OLYMPICS TODAY AND TONIGHT...AND OVER THE CASCADES FROM LATE THIS
AFTERNOON THROUGH SUNDAY MORNING...WHEN LOW LEVEL W FLOW AROUND 850
MB RISES TO 40-50 KT.

ANY FLOODING WOULD LIKELY BEGIN AS EARLY AS SATURDAY NIGHT ON THE
SKOKOMISH RIVER. THE CASCADE RIVERS COULD FLOOD SATURDAY NIGHT OR
SUNDAY. MODELS SHOW HEAVY RAIN ENDING SUNDAY NIGHT. KAM

&&

.AVIATION...A STRONG FRONTAL SYSTEM WILL MOVE THROUGH WESTERN WA
TODAY AND TONIGHT...THERE ARE ACTUALLY TWO FRONTAL WAVES...ONE THIS
MORNING AND ANOTHER LATER THIS AFTERNOON AND EVENING. STRONG WSW
FLOW ALOFT. THE AIR WILL BE MOIST AND STABLE WITH RAIN AND OVERALL
LOWERING CIGS. THERE MIGHT BE A FEW HOURS OF IMPROVEMENT EARLY THIS
AFTERNOON...BUT THERE WONT BE MUCH OF A BREAK BETWEEN THE STRONG
FRONTAL WAVE THIS MORNING...AND THE NEXT ONE LATER THIS AFTERNOON
AND EVENING. THE MOUNTAINS AND FOOTHILLS WILL BE OBSCURED.

KSEA...RAIN AND AN INCREASING SOUTHERLY BLUSTERY SSW WIND LATER
TODAY WITH THE PASSAGE OF THE SECOND FRONTAL WAVE.

&&

.MARINE...A STRONG SYSTEM WILL MOVE THROUGH WESTERN WA TODAY AND
TONIGHT. SUNDAY SHOULD BE A POSTFRONTAL DAY WITH STRONG ONSHORE FLOW
EASING BY SUNDAY NIGHT AND MON. SEAS OVER THE COASTAL WATERS WILL BE
AROUND 20FT TODAY AND THERE IS A HIGH SURF ADVISORY FOR THE COASTAL
BEACHES THROUGH SATURDAY AND A COASTAL FLOOD ADVISORY FOR MINOR
FLOODING OF LOW AREAS NEAR THE BEACHES DURING THE TIME OF HIGH TIDE
THIS MORNING.

&&

.SEW WATCHES/WARNINGS/ADVISORIES...
WA...HIGH WIND WARNINGS ARE IN EFFECT FOR THE COAST AND PARTS OF THE
     NORTH INTERIOR.

     HIGH SURF ADVISORY IN EFFECT TIL 4 PM SATURDAY FOR THE COAST.

     WIND ADVISORY IN EFFECT UNTIL NOON FOR WESTERN SKAGIT COUNTY.

     WINTER WEATHER ADVISORY IN EFFECT FROM UNTIL 4 PM TODAY FOR THE
      CASCADES.

     COASTAL FLOOD ADVISORY IN EFFECT FROM UNTIL 1 PM TODAY FOR THE
      COAST.

     FLOOD WATCHES ARE IN EFFECT FOR MUCH OF THE CWA FROM SATURDAY
     AFTERNOON THROUGH LATE SUNDAY NIGHT.

PZ...GALE WARNING COAST...STRAIT...NORTHERN INLAND WATERS.
     SMALL CRAFT ADVISORY ADMIRALTY INLET AND PUGET SOUND AND HOOD
      CANAL.
     SMALL CRAFT ADVISORY FOR SEVERE CONDITIONS GRAYS HARBOR BAR.

&&

$$

WWW.WEATHER.GOV/SEATTLE

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000
FXUS66 KSEW 201200
AFDSEW

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SEATTLE WA
400 AM PST SAT DEC 20 2014

.SYNOPSIS...TWO STRONG WARM FRONTS WILL MOVE ACROSS WESTERN
WASHINGTON EARLY THIS MORNING AND LATE THIS AFTERNOON. STRONG MOIST
WEST FLOW ALOFT WILL FOLLOW TONIGHT AND SUNDAY. THIS WILL BRING WET
AND WINDY CONDITIONS TO THE LOWLANDS AND HEAVY RAIN OVER THE
MOUNTAINS. AN UPPER LEVEL RIDGE WILL BUILD OVER THE REGION MONDAY
FOR DRIER WEATHER. THE RIDGE WILL WEAKEN MONDAY NIGHT ALLOWING A
COUPLE OF WEATHER SYSTEMS TO REACH THE AREA THROUGH MID NEXT WEEK.

&&

.SHORT TERM...STRONG ZONAL FLOW ACROSS THE NE PACIFIC PUMPED UP BY A
170 KT JETSTREAK WILL DRIVE A PLUME OF WARM MOIST AIR OVER W WA THIS
WEEKEND. MODELS HAVE BEEN GENERALLY CONSISTENT. A STRONG WARM FRONT
WILL MOVE ACROSS W WA EARLY THIS MORNING...WITH STRONG S FLOW ALOFT
AHEAD OF THE WARM FRONT CRANKING UP HEAVY RAIN OVER THE OLYMPICS.
RADAR SHOWS HEAVY RAIN BEGINNING TO REACH THE COAST AND OLYMPICS AT
11Z WITH LIGHT RAIN OVER PUGET SOUND. SURFACE WINDS ARE RISING ALONG
THE COAST AND OVER THE N INTERIOR.

THE WARM FRONT WILL BRING THE STRONGEST WINDS TO THE COAST EARLY
THIS MORNING...AND TO THE N INTERIOR THROUGH MID MORNING...THEN
SHIFT TO SW-S AND EASE BEHIND THE WARM FRONT.

MODELS STILL HAVE A SECOND STRONG WARM FRONT REACHING THE AREA THIS
AFTERNOON...BUT THE 00Z-06Z RUNS HAVE TRENDED A LITTLE WEAKER WITH
THE SURFACE WINDS. EARLIER MODELS WITH STRONGER SOLUTIONS SHOWED A
SMALL SURFACE LOW TRACKING ACROSS VANCOUVER ISLAND BEHIND THE WARM
FRONT...BUT THE GFS NOW ONLY SHOWS AN OPEN SURFACE TROUGH AND THE
ECMWF AND NAM HAVE WEAKER SURFACE LOWS. IT NOW LOOKS LIKE SURFACE
WINDS WILL REMAIN JUST BELOW ADVISORY LEVELS THIS AFTERNOON AND
EVENING. ONE CONCERN IS THAT STRONG SW FLOW ALOFT ACROSS THE
OLYMPICS MAY ALLOW A SMALL MESO-LOW TO FORM OVER THE NE CORNER OF
THE OLYMPICS BRINGING STRONGER WINDS TO THE HOOD CANAL AND ADMIRALTY
INLET AREA. HOWEVER ONLY THE 06Z NAM SHOWS THIS. FOR NOW I WILL
STICK WITH THE PLAN...ALLOWING THE HIGH WIND WARNINGS FOR THE COAST
AND N INTERIOR TO EXPIRE AT 9 AM AND NOON RESPECTIVELY.

HEAVY PRECIPITATION IS EXPECTED TO DEVELOP OVER THE CASCADES THIS
MORNING AS LOW LEVEL WINDS SHIFT TO SW BEHIND THE WARM FRONT.
CASCADE SNOW LEVELS ARE STARTING OUT AROUND 3000 FEET...SO SOME
BRIEF HEAVY SNOW COULD DEVELOP THIS MORNING BEFORE THE WARM AIR
BEHIND THE WARM FRONT LIFTS SNOW LEVELS ABOVE CRITICAL PASS LEVELS.
PARADISE COULD SEE 6-11 INCHES OF SNOW BEFORE SNOW LEVELS RISE TO
6500 FEET AROUND MIDDAY. STEVENS PASS HAS A CHANCE AT REACHING 3-8
INCHES BY EARLY AFTERNOON...AND MOUNT BAKER COULD SEE UP TO 9 INCHES
THROUGH 4 PM. THE SNOW IS GOING TO HAVE TO RAMP UP PRETTY FAST THIS
MORNING TO MEET THESE ACCUMULATIONS...SO CONFIDENCE IN THESE SNOW
AMOUNTS IS NOT ALL THAT HIGH. THERE IS A GOOD CHANCE THAT SNOW
TOTALS WILL BE LOWER.

THE THIRD PROBLEM IS HEAVY RAIN OVER THE OLYMPICS AND CASCADES
THROUGH SUNDAY AFTERNOON. S FLOW WITH THE FIRST WARM FRONT WILL NOT
BRING MUCH SIGNIFICANT RAIN TO THE CASCADES...BUT IT WILL BRING
HEAVY RAIN TO THE OLYMPICS. LOW LEVEL WINDS WILL SHIFT TO WESTERLY
THIS AFTERNOON THEN STRENGTHEN TO 40-50 KT AT 850 MB THIS
EVENING...THEN SLOWLY EASE THROUGH SUNDAY. HEAVY RAIN WILL DEVELOP
OVER THE CASCADES...AND RAIN WILL CONTINUE TO FALL OVER THE
OLYMPICS. SNOW LEVELS WILL BE HIGH THIS AFTERNOON THROUGH SUNDAY.
THE HEAVIEST RAIN OVER THE CASCADES STILL LOOKS LIKE IT WILL BE
FROM ABOUT SNOQUALMIE PASS SOUTHWARD. THE LATEST QPF FORECAST STILL
HAS 3-5 INCHES OVER MUCH OF THE CASCADES WITH A BULLSEYE OF 7 INCHES
OVER MT RAINIER. THE OLYMPICS GET 3-4.5 INCHES THROUGH 12Z SUNDAY.

STRONG W FLOW ALOFT CONTINUES SUNDAY AFTERNOON AND NIGHT...BUT THE
MOISTURE EMBEDDED IN THE FLOW DIMINISHES...SO THE HEAVY RAIN WILL
END.

MODELS REMAIN ON TRACK BUILDING AN UPPER LEVEL RIDGE JUST OFFSHORE
ON MONDAY...WHILE A SURFACE HIGH SETTLES OVER W WA. WINDS WILL
WEAKEN AND THE AIR MASS WILL DRY...BUT THERE WILL STILL BE ENOUGH
CLOUD COVER AROUND FOR MOSTLY CLOUD SKIES. POPS OVER THE LOWLANDS
HAVE BEEN LOWERED INTO THE 20-30 RANGE...BUT IF THE MODELS KEEP IT
DRY THE CHANCE OF RAIN COULD PROBABLY BE DROPPED IN A LATER
FORECAST. KAM

.LONG TERM...MODEL SOLUTIONS REMAIN IN FLUX FROM TUESDAY ONWARD.
ONCE AGAIN THE LATEST GFS AND ECMWF SOLUTIONS ARE IN FAIR
AGREEMENT...BUT THE SOLUTIONS KEEP CHANGING WITH EACH NEW RUN. THE
WEATHER PATTERN WILL REMAIN ACTIVE NEXT WEEK...BUT NOT AS WET AND
WINDY AS THIS WEEKEND. THE LATEST SOLUTIONS FLATTEN THE MONDAY
RIDGE...ALLOWING WARM ADVECTION RAIN TO CREEP THROUGH IT AND OVER W
WA ON TUESDAY. A NORMAL STRENGTH FRONTAL SYSTEM CROSSES THE AREA ON
WEDNESDAY. NO SIGNIFICANT SYSTEMS SHOW UP THURSDAY AND FRIDAY...BUT
THE NW FLOW ALOFT MAY STILL BE MOIST ENOUGH TO KEEP A CHANCE OF
RAIN. CONFIDENCE REMAINS LOW. KAM

&&

.HYDROLOGY...STRONG MOIST W FLOW ALOFT WITH A COUPLE OF WARM FRONTS
WILL BRING HEAVY RAIN TO THE MOUNTAINS TODAY THROUGH SUNDAY. THREE
TO FIVE INCHES OF RAIN IS EXPECTED TO FALL OVER THE OLYMPICS...AND
OVER THE CASCADES FROM ROUGHLY STEVENS PASS SOUTHWARD. A BULLSEYE OF
7 INCHES IS POSSIBLE OVER MT RAINIER. THIS AMOUNT OF RAIN IS GREAT
ENOUGH TO CAUSE FLOODING ON SOME OF THE RIVERS FLOWING OFF THE
OLYMPICS AND CASCADES. A FLOOD WATCH REMAINS IN EFFECT.

PRECIPITATION WILL START AS SNOW OVER THE CASCADES THIS MORNING BUT
SNOW LEVELS WILL RISE RAPIDLY...PEAKING OUT NEAR 5500 FEET NORTH TO
7500 FEET SOUTH THIS EVENING. THE HEAVIEST RAIN WILL BE OVER THE
OLYMPICS TODAY AND TONIGHT...AND OVER THE CASCADES FROM LATE THIS
AFTERNOON THROUGH SUNDAY MORNING...WHEN LOW LEVEL W FLOW AROUND 850
MB RISES TO 40-50 KT.

ANY FLOODING WOULD LIKELY BEGIN AS EARLY AS SATURDAY NIGHT ON THE
SKOKOMISH RIVER. THE CASCADE RIVERS COULD FLOOD SATURDAY NIGHT OR
SUNDAY. MODELS SHOW HEAVY RAIN ENDING SUNDAY NIGHT. KAM

&&

.AVIATION...A STRONG FRONTAL SYSTEM WILL MOVE THROUGH WESTERN WA
TODAY AND TONIGHT...THERE ARE ACTUALLY TWO FRONTAL WAVES...ONE THIS
MORNING AND ANOTHER LATER THIS AFTERNOON AND EVENING. STRONG WSW
FLOW ALOFT. THE AIR WILL BE MOIST AND STABLE WITH RAIN AND OVERALL
LOWERING CIGS. THERE MIGHT BE A FEW HOURS OF IMPROVEMENT EARLY THIS
AFTERNOON...BUT THERE WONT BE MUCH OF A BREAK BETWEEN THE STRONG
FRONTAL WAVE THIS MORNING...AND THE NEXT ONE LATER THIS AFTERNOON
AND EVENING. THE MOUNTAINS AND FOOTHILLS WILL BE OBSCURED.

KSEA...RAIN AND AN INCREASING SOUTHERLY BLUSTERY SSW WIND LATER
TODAY WITH THE PASSAGE OF THE SECOND FRONTAL WAVE.

&&

.MARINE...A STRONG SYSTEM WILL MOVE THROUGH WESTERN WA TODAY AND
TONIGHT. SUNDAY SHOULD BE A POSTFRONTAL DAY WITH STRONG ONSHORE FLOW
EASING BY SUNDAY NIGHT AND MON. SEAS OVER THE COASTAL WATERS WILL BE
AROUND 20FT TODAY AND THERE IS A HIGH SURF ADVISORY FOR THE COASTAL
BEACHES THROUGH SATURDAY AND A COASTAL FLOOD ADVISORY FOR MINOR
FLOODING OF LOW AREAS NEAR THE BEACHES DURING THE TIME OF HIGH TIDE
THIS MORNING.

&&

.SEW WATCHES/WARNINGS/ADVISORIES...
WA...HIGH WIND WARNINGS ARE IN EFFECT FOR THE COAST AND PARTS OF THE
     NORTH INTERIOR.

     HIGH SURF ADVISORY IN EFFECT TIL 4 PM SATURDAY FOR THE COAST.

     WIND ADVISORY IN EFFECT UNTIL NOON FOR WESTERN SKAGIT COUNTY.

     WINTER WEATHER ADVISORY IN EFFECT FROM UNTIL 4 PM TODAY FOR THE
      CASCADES.

     COASTAL FLOOD ADVISORY IN EFFECT FROM UNTIL 1 PM TODAY FOR THE
      COAST.

     FLOOD WATCHES ARE IN EFFECT FOR MUCH OF THE CWA FROM SATURDAY
     AFTERNOON THROUGH LATE SUNDAY NIGHT.

PZ...GALE WARNING COAST...STRAIT...NORTHERN INLAND WATERS.
     SMALL CRAFT ADVISORY ADMIRALTY INLET AND PUGET SOUND AND HOOD
      CANAL.
     SMALL CRAFT ADVISORY FOR SEVERE CONDITIONS GRAYS HARBOR BAR.

&&

$$

WWW.WEATHER.GOV/SEATTLE

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000
FXUS66 KSEW 200548
AFDSEW

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SEATTLE WA
948 PM PST FRI DEC 19 2014

.SYNOPSIS...A STRONG LOW PRESSURE SYSTEM WILL BRING LOCALLY HEAVY
PRECIPITATION AND STRONG WINDS TO THE AREA LATE TONIGHT THROUGH
SATURDAY. STRONG AND MOIST WESTERLY FLOW ALOFT WILL PREVAIL
SATURDAY NIGHT THROUGH SUNDAY FOR HEAVY RAIN AT TIMES IN THE
MOUNTAINS. HIGH PRESSURE ALOFT WILL BUILD INTO THE REGION SUNDAY
NIGHT AND THEN PREVAIL OVER THE AREA ON MONDAY FOR A DRYING TREND.

&&

.SHORT TERM...
THE LEADING EDGE OF THE PRECIP SHIELD ASSOCIATED WITH THE NEXT
PACIFIC STORM WAS APPROACHING THE COAST AT THIS TIME. LOOK FOR THE
PRECIP TO OVERSPREAD THE CWA OVERNIGHT. IN ADDITION TO THE PRECIP...
THE SOUTHEAST TO NORTHWEST SURFACE PRESSURE GRADIENT WILL TIGHTEN
OVERNIGHT AHEAD OF A WEAKENING WARM FRONT. THIS WILL RESULT IN THE
DEVELOPMENT OF LOCALLY GUSTY WINDS OVER THOSE AREAS PRONE TO
STRONG SOUTHEAST WINDS.

THE LATEST GFS AND NAM MOS GUIDANCE INDICATED THAT THE STRONGEST
WINDS WILL HOLD OFF OVER THE COAST AND NORTH INTERIOR UNTIL LATE
SATURDAY MORNING OR SATURDAY AFTERNOON. HOWEVER...THE HRRR
INDICATED THE POTENTIAL FOR HIGH WINDS OVER THE COAST LATE TONIGHT
OR EARLY SATURDAY MORNING...AND OVER THE NORTH INTERIOR SATURDAY
MORNING. THERE IS A POSSIBILITY THAT THERE MAY BE TWO PERIODS OF
VERY STRONG WINDS OVER THE COAST AND NORTH INTERIOR...ONE WITH THE
WEAKENING WARM FRONT LATE TONIGHT/SATURDAY MORNING AND ONE WITH
THE OCCLUDED FRONT SATURDAY AFTERNOON. IT IS POSSIBLE THAT THE
HIGH WIND WARNING MAY NEED TO BE EXTENDED.

CONCERNING THE HIGH SURF AND THE POTENTIAL FOR MINOR COASTAL
FLOODING...SWELL ON THE COAST WILL REACH 20 FEET OR SO TONIGHT
AND SATURDAY. COUPLED WITH HIGH TIDES AROUND NOON SATURDAY THERE
COULD BE SOME MINOR TIDAL OVERFLOW. THERE IS A HIGH SURF ADVISORY
FOR THE COASTAL BEACHES THROUGH SATURDAY AND A COASTAL FLOOD
ADVISORY FOR MINOR FLOODING OF LOW AREAS NEAR THE BEACHES DURING
THE TIME OF HIGH TIDE SATURDAY MORNING.

MEANWHILE...A PLUME OF MOISTURE WAS BEING TRANSPORTED EAST ALONG A
STRONG 180-KNOT JET AIMED AT WESTERN WASHINGTON. THIS WILL RESULT
IN HEAVY PRECIP ON THE COAST AND MOUNTAINS. INITIALLY...SNOW
LEVELS WILL BE IN THE 3000 TO 4000 FOOT RANGE SATURDAY MORNING BUT
WILL RISE INTO THE 6000 TO 7000 FOOT RANGE SATURDAY AFTERNOON AS A
MILDER AIR MASS MOVES IN.

THE CASCADES COULD SEE BRIEF HEAVY SNOW BEFORE THE PRECIP CHANGES
OVER TO RAIN SATURDAY AFTERNOON AND EARLY EVENING. THE SNOW LEVELS
WILL REMAIN RELATIVELY HIGH SATURDAY NIGHT THROUGH SUNDAY WITH
MAINLY RAIN...HEAVY AT TIMES...FALLING IN THE MOUNTAINS. THIS
COULD LEAD TO RIVER FLOODING...HENCE THE FLOOD WATCH.

PERIODS OF HEAVY RAIN WILL CONTINUE IN THE MOUNTAINS SATURDAY NIGHT
THROUGH SUNDAY MORNING DUE TO STRONG WESTERLY WINDS ALOFT. THE
PRECIP WILL TAPER OFF TO SHOWERS SUNDAY NIGHT AS AN UPPER RIDGE
BUILDS IN OVER THE AREA FROM THE WEST.

AN UPPER RIDGE WILL PREVAIL OVER THE REGION ON MONDAY FOR DRIER
CONDITIONS. IN FACT...MUCH OF THE CWA MIGHT END UP DRY ON MON.
33/05/19

.LONG TERM FROM THE PREVIOUS DISCUSSION...
MODELS ARE WEAKENING THE RIDGE OVER THE PAC NW ON TUE WITH
WESTERLY FLOW ALOFT OVER THE REGION. A BAROCLINIC BAND WILL STALL
OVER THE AREA FOR MORE RAIN. SNOW LEVELS ARE STILL HIGH AROUND
5000-6000 FT. THERE ARE SOME SLIGHT DIFFERENCES IN THE MODELS WITH
THE ECMWF ABOUT 6 HOURS FASTER THAN THE GFS. AN UPPER LEVEL TROUGH
WILL THEN MOVE INLAND ON WED...SHIFTING THE BAROCLINIC BAND SOUTH
OF THE CWA. NORTHERLY FLOW WILL PREVAIL ON CHRISTMAS DAY FOR
MAINLY DRY WEATHER. THIS PATTERN CONTINUES ON FRIDAY. 33

&&

.HYDROLOGY...
HEAVY RAIN IS FORECAST SATURDAY AFTERNOON THROUGH SUNDAY IN THE
MOUNTAINS...THUS A FLOOD WATCH IS IN EFFECT FOR THE RIVERS FLOWING
OFF THE OLYMPICS AND CASCADES.

PRECIPITATION WILL INITIALLY FALL AS SNOW IN THE MOUNTAINS WITH SNOW
LEVELS IN THE 3000 TO 4000 FOOT RANGE. A MILDER AIR MASS WILL MOVE
INTO THE CWA SATURDAY AFTERNOON AND EVENING...CAUSING THE SNOW
LEVELS TO RISE INTO THE 6000 TO 7000 FOOT RANGE. THIS MEANS THAT
THE PRECIPITATION WILL FALL AS RAIN IN THE MOUNTAINS BELOW AT
LEAST THE 6000 FOOT LEVEL. AMOUNTS IN THE OLYMPICS AND CASCADES
ARE FORECAST TO BE GENERALLY IN THE 3 TO 5 INCH RANGE...WITH
LOCALLY UP TO 8 INCHES POSSIBLE ON MOUNT RAINIER.

FLOODING WOULD LIKELY BEGIN SATURDAY NIGHT ON THE OLYMPIC RANGE
WHILES FLOODING ON THE CASCADES WOULD PROBABLY HOLD OFF UNTIL
SUNDAY. THE RIVERS WOULD CREST SUNDAY NIGHT OR MONDAY.

THE HEAVY RAIN IS ANTICIPATED TO END SUNDAY NIGHT. BEYOND MONDAY...
FLOODING IS NOT EXPECTED THROUGH FRIDAY.

&&

.AVIATION...A STRONG FRONTAL SYSTEM WILL MOVE INTO WRN WA OVERNIGHT
THROUGH SATURDAY EVENING. THERE WILL BE STRONG WESTERLY FLOW ALOFT.
THE AIR WILL BE MOIST AND STABLE WITH RAIN...LOWERING CIGS TONIGHT
AND SATURDAY MORNING...PERHAPS A LITTLE IMPROVEMENT MIDDAY...THEN
LOWERING AGAIN WITH A SECOND FRONTAL WAVE LATER IN THE AFTERNOON AND
EVENING. THE MOUNTAINS AND FOOTHILLS WILL BE OBSCURED THROUGH THE
WEEKEND.

KSEA...RAIN DEVELOPING OVERNIGHT AND AN INCREASING SOUTHERLY BREEZE
THROUGH SATURDAY...PROBABLY BECOMING QUITE BLUSTERY BY SATURDAY
EVENING WITH THE PASSAGE OF THE SECOND FRONTAL WAVE.

&&

.MARINE...A STRONG SYSTEM WILL APPROACH TONIGHT WITH GALES LIKELY
OVER THE COAST...ENTRANCES...AND NORTHERN INLAND WATERS. AFTER A
BRIEF LULL IN WINDS MIDDAY SATURDAY IT SHOULD BECOME QUITE BLUSTERY
WITH MORE GALES LATER IN THE AFTERNOON AND EVENING. A WEAKER SYSTEM
ARRIVES MONDAY NIGHT OR TUESDAY.

&&

.SEW WATCHES/WARNINGS/ADVISORIES...
WA...HIGH WIND WARNINGS ARE IN EFFECT FOR THE COAST AND PARTS OF THE
     NORTH INTERIOR.

     HIGH SURF ADVISORY IN EFFECT TIL 4 PM SATURDAY FOR THE COAST.

     WIND ADVISORY IN EFFECT FROM MIDNIGHT TONIGHT TIL NOON
     SATURDAY FOR WESTERN SKAGIT COUNTY.

     WINTER WEATHER ADVISORY IN EFFECT FROM 4 AM TIL 4 PM SATURDAY
     FOR THE CASCADES.

     COASTAL FLOOD ADVISORY IN EFFECT FROM 8 AM TIL 1 PM SATURDAY
     FOR THE COAST.

     FLOOD WATCHES ARE IN EFFECT FOR MUCH OF THE CWA FROM SATURDAY
     AFTERNOON THROUGH LATE SUNDAY NIGHT.

PZ...GALE WARNINGS ARE IN EFFECT FOR THE COASTAL WATERS...ENTRANCES
     TO THE STRAIT OF JUAN DE FUCA...AND THE NORTHERN INLAND WATERS.

     SMALL CRAFT ADVISORIES ARE IN EFFECT FOR THE REMAINING WATERS.

     SMALL CRAFT ADVISORY FOR ROUGH BAR IN EFFECT TIL 9 PM
     SATURDAY FOR THE GRAYS HARBOR BAR.&&

$$

WWW.WEATHER.GOV/SEATTLE

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000
FXUS66 KSEW 200548
AFDSEW

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SEATTLE WA
948 PM PST FRI DEC 19 2014

.SYNOPSIS...A STRONG LOW PRESSURE SYSTEM WILL BRING LOCALLY HEAVY
PRECIPITATION AND STRONG WINDS TO THE AREA LATE TONIGHT THROUGH
SATURDAY. STRONG AND MOIST WESTERLY FLOW ALOFT WILL PREVAIL
SATURDAY NIGHT THROUGH SUNDAY FOR HEAVY RAIN AT TIMES IN THE
MOUNTAINS. HIGH PRESSURE ALOFT WILL BUILD INTO THE REGION SUNDAY
NIGHT AND THEN PREVAIL OVER THE AREA ON MONDAY FOR A DRYING TREND.

&&

.SHORT TERM...
THE LEADING EDGE OF THE PRECIP SHIELD ASSOCIATED WITH THE NEXT
PACIFIC STORM WAS APPROACHING THE COAST AT THIS TIME. LOOK FOR THE
PRECIP TO OVERSPREAD THE CWA OVERNIGHT. IN ADDITION TO THE PRECIP...
THE SOUTHEAST TO NORTHWEST SURFACE PRESSURE GRADIENT WILL TIGHTEN
OVERNIGHT AHEAD OF A WEAKENING WARM FRONT. THIS WILL RESULT IN THE
DEVELOPMENT OF LOCALLY GUSTY WINDS OVER THOSE AREAS PRONE TO
STRONG SOUTHEAST WINDS.

THE LATEST GFS AND NAM MOS GUIDANCE INDICATED THAT THE STRONGEST
WINDS WILL HOLD OFF OVER THE COAST AND NORTH INTERIOR UNTIL LATE
SATURDAY MORNING OR SATURDAY AFTERNOON. HOWEVER...THE HRRR
INDICATED THE POTENTIAL FOR HIGH WINDS OVER THE COAST LATE TONIGHT
OR EARLY SATURDAY MORNING...AND OVER THE NORTH INTERIOR SATURDAY
MORNING. THERE IS A POSSIBILITY THAT THERE MAY BE TWO PERIODS OF
VERY STRONG WINDS OVER THE COAST AND NORTH INTERIOR...ONE WITH THE
WEAKENING WARM FRONT LATE TONIGHT/SATURDAY MORNING AND ONE WITH
THE OCCLUDED FRONT SATURDAY AFTERNOON. IT IS POSSIBLE THAT THE
HIGH WIND WARNING MAY NEED TO BE EXTENDED.

CONCERNING THE HIGH SURF AND THE POTENTIAL FOR MINOR COASTAL
FLOODING...SWELL ON THE COAST WILL REACH 20 FEET OR SO TONIGHT
AND SATURDAY. COUPLED WITH HIGH TIDES AROUND NOON SATURDAY THERE
COULD BE SOME MINOR TIDAL OVERFLOW. THERE IS A HIGH SURF ADVISORY
FOR THE COASTAL BEACHES THROUGH SATURDAY AND A COASTAL FLOOD
ADVISORY FOR MINOR FLOODING OF LOW AREAS NEAR THE BEACHES DURING
THE TIME OF HIGH TIDE SATURDAY MORNING.

MEANWHILE...A PLUME OF MOISTURE WAS BEING TRANSPORTED EAST ALONG A
STRONG 180-KNOT JET AIMED AT WESTERN WASHINGTON. THIS WILL RESULT
IN HEAVY PRECIP ON THE COAST AND MOUNTAINS. INITIALLY...SNOW
LEVELS WILL BE IN THE 3000 TO 4000 FOOT RANGE SATURDAY MORNING BUT
WILL RISE INTO THE 6000 TO 7000 FOOT RANGE SATURDAY AFTERNOON AS A
MILDER AIR MASS MOVES IN.

THE CASCADES COULD SEE BRIEF HEAVY SNOW BEFORE THE PRECIP CHANGES
OVER TO RAIN SATURDAY AFTERNOON AND EARLY EVENING. THE SNOW LEVELS
WILL REMAIN RELATIVELY HIGH SATURDAY NIGHT THROUGH SUNDAY WITH
MAINLY RAIN...HEAVY AT TIMES...FALLING IN THE MOUNTAINS. THIS
COULD LEAD TO RIVER FLOODING...HENCE THE FLOOD WATCH.

PERIODS OF HEAVY RAIN WILL CONTINUE IN THE MOUNTAINS SATURDAY NIGHT
THROUGH SUNDAY MORNING DUE TO STRONG WESTERLY WINDS ALOFT. THE
PRECIP WILL TAPER OFF TO SHOWERS SUNDAY NIGHT AS AN UPPER RIDGE
BUILDS IN OVER THE AREA FROM THE WEST.

AN UPPER RIDGE WILL PREVAIL OVER THE REGION ON MONDAY FOR DRIER
CONDITIONS. IN FACT...MUCH OF THE CWA MIGHT END UP DRY ON MON.
33/05/19

.LONG TERM FROM THE PREVIOUS DISCUSSION...
MODELS ARE WEAKENING THE RIDGE OVER THE PAC NW ON TUE WITH
WESTERLY FLOW ALOFT OVER THE REGION. A BAROCLINIC BAND WILL STALL
OVER THE AREA FOR MORE RAIN. SNOW LEVELS ARE STILL HIGH AROUND
5000-6000 FT. THERE ARE SOME SLIGHT DIFFERENCES IN THE MODELS WITH
THE ECMWF ABOUT 6 HOURS FASTER THAN THE GFS. AN UPPER LEVEL TROUGH
WILL THEN MOVE INLAND ON WED...SHIFTING THE BAROCLINIC BAND SOUTH
OF THE CWA. NORTHERLY FLOW WILL PREVAIL ON CHRISTMAS DAY FOR
MAINLY DRY WEATHER. THIS PATTERN CONTINUES ON FRIDAY. 33

&&

.HYDROLOGY...
HEAVY RAIN IS FORECAST SATURDAY AFTERNOON THROUGH SUNDAY IN THE
MOUNTAINS...THUS A FLOOD WATCH IS IN EFFECT FOR THE RIVERS FLOWING
OFF THE OLYMPICS AND CASCADES.

PRECIPITATION WILL INITIALLY FALL AS SNOW IN THE MOUNTAINS WITH SNOW
LEVELS IN THE 3000 TO 4000 FOOT RANGE. A MILDER AIR MASS WILL MOVE
INTO THE CWA SATURDAY AFTERNOON AND EVENING...CAUSING THE SNOW
LEVELS TO RISE INTO THE 6000 TO 7000 FOOT RANGE. THIS MEANS THAT
THE PRECIPITATION WILL FALL AS RAIN IN THE MOUNTAINS BELOW AT
LEAST THE 6000 FOOT LEVEL. AMOUNTS IN THE OLYMPICS AND CASCADES
ARE FORECAST TO BE GENERALLY IN THE 3 TO 5 INCH RANGE...WITH
LOCALLY UP TO 8 INCHES POSSIBLE ON MOUNT RAINIER.

FLOODING WOULD LIKELY BEGIN SATURDAY NIGHT ON THE OLYMPIC RANGE
WHILES FLOODING ON THE CASCADES WOULD PROBABLY HOLD OFF UNTIL
SUNDAY. THE RIVERS WOULD CREST SUNDAY NIGHT OR MONDAY.

THE HEAVY RAIN IS ANTICIPATED TO END SUNDAY NIGHT. BEYOND MONDAY...
FLOODING IS NOT EXPECTED THROUGH FRIDAY.

&&

.AVIATION...A STRONG FRONTAL SYSTEM WILL MOVE INTO WRN WA OVERNIGHT
THROUGH SATURDAY EVENING. THERE WILL BE STRONG WESTERLY FLOW ALOFT.
THE AIR WILL BE MOIST AND STABLE WITH RAIN...LOWERING CIGS TONIGHT
AND SATURDAY MORNING...PERHAPS A LITTLE IMPROVEMENT MIDDAY...THEN
LOWERING AGAIN WITH A SECOND FRONTAL WAVE LATER IN THE AFTERNOON AND
EVENING. THE MOUNTAINS AND FOOTHILLS WILL BE OBSCURED THROUGH THE
WEEKEND.

KSEA...RAIN DEVELOPING OVERNIGHT AND AN INCREASING SOUTHERLY BREEZE
THROUGH SATURDAY...PROBABLY BECOMING QUITE BLUSTERY BY SATURDAY
EVENING WITH THE PASSAGE OF THE SECOND FRONTAL WAVE.

&&

.MARINE...A STRONG SYSTEM WILL APPROACH TONIGHT WITH GALES LIKELY
OVER THE COAST...ENTRANCES...AND NORTHERN INLAND WATERS. AFTER A
BRIEF LULL IN WINDS MIDDAY SATURDAY IT SHOULD BECOME QUITE BLUSTERY
WITH MORE GALES LATER IN THE AFTERNOON AND EVENING. A WEAKER SYSTEM
ARRIVES MONDAY NIGHT OR TUESDAY.

&&

.SEW WATCHES/WARNINGS/ADVISORIES...
WA...HIGH WIND WARNINGS ARE IN EFFECT FOR THE COAST AND PARTS OF THE
     NORTH INTERIOR.

     HIGH SURF ADVISORY IN EFFECT TIL 4 PM SATURDAY FOR THE COAST.

     WIND ADVISORY IN EFFECT FROM MIDNIGHT TONIGHT TIL NOON
     SATURDAY FOR WESTERN SKAGIT COUNTY.

     WINTER WEATHER ADVISORY IN EFFECT FROM 4 AM TIL 4 PM SATURDAY
     FOR THE CASCADES.

     COASTAL FLOOD ADVISORY IN EFFECT FROM 8 AM TIL 1 PM SATURDAY
     FOR THE COAST.

     FLOOD WATCHES ARE IN EFFECT FOR MUCH OF THE CWA FROM SATURDAY
     AFTERNOON THROUGH LATE SUNDAY NIGHT.

PZ...GALE WARNINGS ARE IN EFFECT FOR THE COASTAL WATERS...ENTRANCES
     TO THE STRAIT OF JUAN DE FUCA...AND THE NORTHERN INLAND WATERS.

     SMALL CRAFT ADVISORIES ARE IN EFFECT FOR THE REMAINING WATERS.

     SMALL CRAFT ADVISORY FOR ROUGH BAR IN EFFECT TIL 9 PM
     SATURDAY FOR THE GRAYS HARBOR BAR.&&

$$

WWW.WEATHER.GOV/SEATTLE

YOU CAN SEE AN ILLUSTRATED VERSION OF THIS FORECAST DISCUSSION AT
WWW.WEATHER.GOV/SEATTLE/GAFD/LATEST_WEBAFD.HTML






000
FXUS66 KSEW 200006 CCA
AFDSEW

AREA FORECAST DISCUSSION...CORRECTION
NATIONAL WEATHER SERVICE SEATTLE WA
330 PM PST FRI DEC 19 2014

CORRECTION TO SYNOPSIS.

.SYNOPSIS...A STRONG PACIFIC FRONTAL SYSTEM WILL BRING RAIN AND WIND
TO WESTERN WASHINGTON LATE TONIGHT THROUGH SATURDAY. HEAVY RAIN WILL
FALL IN THE MOUNTAINS SATURDAY NIGHT THROUGH SUNDAY. AN UPPER LEVEL
RIDGE WILL MOVE BRIEFLY OVER THE REGION MONDAY FOR DRIER WEATHER.
ADDITIONAL FRONTAL SYSTEMS WILL REACH THE REGION NEXT WEEK.

&&

.SHORT TERM...AN UPPER LEVEL TROUGH IS BRINGING SCATTERED SHOWERS TO
WESTERN WA THIS AFTERNOON. THERE WERE A FEW LIGHTNING STRIKES OVER
THE COAST THIS MORNING BUT ACTIVITY HAS SINCE DIMINISHED. THE
TROUGH AXIS WILL EXIT THIS EVENING WITH SHOWERS TAPERING OFF.

ANOTHER ROUND OF WET AND BLUSTERY WEATHER IS ANTICIPATED LATE
TONIGHT THROUGH SATURDAY AS OUR NEXT SYSTEM ARRIVES. THIS SYSTEM MAY
BRING HIGH WIND TO THE COAST AND NORTH INTERIOR A WARM FRONT MOVES
INLAND SATURDAY MORNING. A HIGH WIND WARNING IS IN EFFECT FOR THESE
ZONES. WINDS WILL PEAK AROUND 12-15Z ALONG THE COAST...AND 18-20Z
FOR THE NORTH INTERIOR.

MEANWHILE...A PLUME OF MOISTURE IS BEING TRANSPORTED EAST ALONG A
STRONG 175 KT JET AIMED AT WASHINGTON...WHICH WILL LIKELY RESULT IN
HEAVY PRECIP ALONG THE COAST AND IN THE MOUNTAINS. INITIALLY SNOW
LEVELS WILL HOVER AROUND 3000-4000 FT SATURDAY MORNING BUT WILL RISE
TO 5000-7000 FT SATURDAY AFTERNOON AS WARMER AIR MOVES IN. THE WEST
SLOPES CASCADES COULD SEE BRIEF HEAVY SNOW BEFORE CHANGING OVER TO
RAIN SATURDAY AFTERNOON AND EVENING. THE SNOW LEVELS WILL REMAIN
HIGH SAT NIGHT THROUGH SUN WITH MAINLY RAIN IN THE MOUNTAINS...HEAVY
AT TIMES. THIS MAY RESULT IN RIVER FLOODING AND A FLOOD WATCH WAS
ISSUED. HEAVY RAIN WILL CONTINUE IN THE MOUNTAINS SAT NIGHT INTO SUN
MORNING WITH STRONG WEST WINDS ALOFT. AN UPPER LEVEL RIDGE WILL THEN
BUILD OVER THE AREA SUN NIGHT. THIS RIDGE WILL CUT OFF THE FLOW
WHICH WILL BRING AN END TO THE STEADY/HEAVY PRECIP IN THE MOUNTAINS.
THIS UPPER LEVEL RIDGE WILL REMAIN OVER THE AREA ON MONDAY FOR DRIER
WEATHER. 33

.LONG TERM...MODELS ARE WEAKENING THE RIDGE OVER THE PAC NW ON TUE
WITH WESTERLY FLOW ALOFT OVER THE REGION. A BAROCLINIC BAND WILL
STALL OVER THE AREA FOR MORE RAIN. SNOW LEVELS ARE STILL HIGH AROUND
5000-6000 FT. THERE ARE SOME SLIGHT DIFFERENCES IN THE MODELS WITH
THE ECMWF ABOUT 6 HOURS FASTER THAN THE GFS. AN UPPER LEVEL TROUGH
WILL THEN MOVE INLAND ON WED...SHIFTING THE BAROCLINIC BAND SOUTH OF
THE CWA. NORTHERLY FLOW WILL PREVAIL ON CHRISTMAS DAY FOR MAINLY DRY
WEATHER. THIS PATTERN CONTINUES ON FRIDAY. 33

&&

.HYDROLOGY...HEAVY PRECIPITATION IS FORECAST SATURDAY AND SUNDAY IN
THE MOUNTAINS AND A FLOOD WATCH IS IN EFFECT FOR THE RIVERS FLOWING
OFF THE OLYMPICS AND THE NORTH AND CENTRAL CASCADES.

PRECIPITATION WILL INITIALLY FALL AS SNOW IN THE MOUNTAINS WITH SNOW
LEVELS AROUND 3000-4000 FT. WARMER AIR WILL THEN MOVE INLAND
SATURDAY AFTERNOON AND EVENING WITH SNOW LEVELS RISING TO 6000-7000
FT FOR MAINLY RAIN IN THE MOUNTAINS. PRECIPITATION AMOUNTS IN THE
OLYMPICS AND CASCADES ARE GENERALLY AROUND 3-5 INCHES...WITH 6-9
INCHES POSSIBLE AT MOUNT RAINIER.

ANY FLOODING WOULD LIKELY BEGIN AS EARLY AS SATURDAY NIGHT ON THE
SKOKOMISH RIVER. THE CASCADE RIVERS COULD FLOOD SATURDAY NIGHT OR
SUNDAY. MODELS SHOW HEAVY RAIN ENDING SUNDAY NIGHT.

&&

.AVIATION...SCATTERED SHOWERS REMAIN OVER WESTERN WASHINGTON THIS
AFTERNOON. THERE HAVE BEEN ISOLATED THUNDERSTORMS ON THE COAST. A
STRONG FRONTAL SYSTEM WILL REACH THE AREA LATER TONIGHT AND SATURDAY
WITH WESTERLY FLOW ALOFT. THE SHOWERS WILL END THIS EVENING AND RAIN
WILL DEVELOP OVERNIGHT. AT THE SURFACE STRONG SOUTHEAST WINDS WILL
DEVELOP TONIGHT. THE FLOW WILL TURN ONSHORE SATURDAY NIGHT.

CEILINGS ARE GENERALLY VFR WITH SOME MVFR IN SHOWERS. CLOUDS WILL
THICKEN AND LOWER TONIGHT WITH SATURDAY BEING MOSTLY MVFR WITH RAIN.

KSEA...DISCUSSION ABOVE APPLIES. WIND WILL BE SOUTHERLY 10-15 KT
OVERNIGHT INCREASING TO 15G25KT SATURDAY. CHB

&&

.MARINE...A STRONG SYSTEM WILL APPROACH TONIGHT WITH GALES LIKELY
OVER THE COAST...ENTRANCES...AND NORTHERN INLAND WATERS. AFTER A
BRIEF LULL IN WINDS SATURDAY AFTERNOON MODELS SHOW A PERIOD OF
STRONG ONSHORE FLOW SATURDAY NIGHT THAT MAY ALSO HAVE NEAR GALE
SOUTHWEST WINDS OVER MOST WATERS.

A WEAKER SYSTEM ARRIVES MONDAY NIGHT OR TUESDAY.

SWELL ON THE COAST WILL REACH 20 FEET OR SO TONIGHT AND SATURDAY.
COUPLED WITH HIGH TIDES AROUND NOON SATURDAY THERE COULD BE SOME
MINOR TIDAL OVERFLOW AT SPOTS. SO FAR BUOY 5...ABOUT 300 MILES OFF
THE COAST...SHOWS ONLY 21 FOOT SWELLS. THESE WILL DECAY A BIT BEFORE
ARRIVING AT THE COAST. HAVE ISSUED A HIGH SURF ADVISORY FOR THE
WAVES ON THE BEACHES TONIGHT AND SATURDAY AND A COASTAL FLOOD
ADVISORY FOR MINOR FLOODING OF LOW AREAS NEAR THE BEACHES DURING THE
TIME OF HIGH TIDE SATURDAY MORNING.

&&

.SEW WATCHES/WARNINGS/ADVISORIES...

WA...HIGH WIND WARNING COAST...WESTERN WHATCOM...SAN
     JUANS...ADMIRALTY INLET.
     WIND ADVISORY WESTERN SKAGIT COUNTY.
     WINTER WEATHER ADVISORY CASCADES.
     HIGH SURF ADVISORY NORTH AND CENTRAL COAST.
     COASTAL FLOOD ADVISORY NORTH AND CENTRAL COAST SATURDAY MORNING.

PZ...GALE WARNING COAST...ENTRANCES...NORTHERN INLAND WATERS.
     SMALL CRAFT ADVISORY CENTRAL STRAIT...ADMIRALTY INLET...AND
     PUGET SOUND AND HOOD CANAL.
     SMALL CRAFT ADVISORY FOR ROUGH GRAYS HARBOR BAR.

&&

$$

YOU CAN SEE AN ILLUSTRATED VERSION OF THIS FORECAST DISCUSSION AT
WWW.WEATHER.GOV/SEATTLE/GAFD/LATEST_WEBAFD.HTML














000
FXUS66 KSEW 200006 CCA
AFDSEW

AREA FORECAST DISCUSSION...CORRECTION
NATIONAL WEATHER SERVICE SEATTLE WA
330 PM PST FRI DEC 19 2014

CORRECTION TO SYNOPSIS.

.SYNOPSIS...A STRONG PACIFIC FRONTAL SYSTEM WILL BRING RAIN AND WIND
TO WESTERN WASHINGTON LATE TONIGHT THROUGH SATURDAY. HEAVY RAIN WILL
FALL IN THE MOUNTAINS SATURDAY NIGHT THROUGH SUNDAY. AN UPPER LEVEL
RIDGE WILL MOVE BRIEFLY OVER THE REGION MONDAY FOR DRIER WEATHER.
ADDITIONAL FRONTAL SYSTEMS WILL REACH THE REGION NEXT WEEK.

&&

.SHORT TERM...AN UPPER LEVEL TROUGH IS BRINGING SCATTERED SHOWERS TO
WESTERN WA THIS AFTERNOON. THERE WERE A FEW LIGHTNING STRIKES OVER
THE COAST THIS MORNING BUT ACTIVITY HAS SINCE DIMINISHED. THE
TROUGH AXIS WILL EXIT THIS EVENING WITH SHOWERS TAPERING OFF.

ANOTHER ROUND OF WET AND BLUSTERY WEATHER IS ANTICIPATED LATE
TONIGHT THROUGH SATURDAY AS OUR NEXT SYSTEM ARRIVES. THIS SYSTEM MAY
BRING HIGH WIND TO THE COAST AND NORTH INTERIOR A WARM FRONT MOVES
INLAND SATURDAY MORNING. A HIGH WIND WARNING IS IN EFFECT FOR THESE
ZONES. WINDS WILL PEAK AROUND 12-15Z ALONG THE COAST...AND 18-20Z
FOR THE NORTH INTERIOR.

MEANWHILE...A PLUME OF MOISTURE IS BEING TRANSPORTED EAST ALONG A
STRONG 175 KT JET AIMED AT WASHINGTON...WHICH WILL LIKELY RESULT IN
HEAVY PRECIP ALONG THE COAST AND IN THE MOUNTAINS. INITIALLY SNOW
LEVELS WILL HOVER AROUND 3000-4000 FT SATURDAY MORNING BUT WILL RISE
TO 5000-7000 FT SATURDAY AFTERNOON AS WARMER AIR MOVES IN. THE WEST
SLOPES CASCADES COULD SEE BRIEF HEAVY SNOW BEFORE CHANGING OVER TO
RAIN SATURDAY AFTERNOON AND EVENING. THE SNOW LEVELS WILL REMAIN
HIGH SAT NIGHT THROUGH SUN WITH MAINLY RAIN IN THE MOUNTAINS...HEAVY
AT TIMES. THIS MAY RESULT IN RIVER FLOODING AND A FLOOD WATCH WAS
ISSUED. HEAVY RAIN WILL CONTINUE IN THE MOUNTAINS SAT NIGHT INTO SUN
MORNING WITH STRONG WEST WINDS ALOFT. AN UPPER LEVEL RIDGE WILL THEN
BUILD OVER THE AREA SUN NIGHT. THIS RIDGE WILL CUT OFF THE FLOW
WHICH WILL BRING AN END TO THE STEADY/HEAVY PRECIP IN THE MOUNTAINS.
THIS UPPER LEVEL RIDGE WILL REMAIN OVER THE AREA ON MONDAY FOR DRIER
WEATHER. 33

.LONG TERM...MODELS ARE WEAKENING THE RIDGE OVER THE PAC NW ON TUE
WITH WESTERLY FLOW ALOFT OVER THE REGION. A BAROCLINIC BAND WILL
STALL OVER THE AREA FOR MORE RAIN. SNOW LEVELS ARE STILL HIGH AROUND
5000-6000 FT. THERE ARE SOME SLIGHT DIFFERENCES IN THE MODELS WITH
THE ECMWF ABOUT 6 HOURS FASTER THAN THE GFS. AN UPPER LEVEL TROUGH
WILL THEN MOVE INLAND ON WED...SHIFTING THE BAROCLINIC BAND SOUTH OF
THE CWA. NORTHERLY FLOW WILL PREVAIL ON CHRISTMAS DAY FOR MAINLY DRY
WEATHER. THIS PATTERN CONTINUES ON FRIDAY. 33

&&

.HYDROLOGY...HEAVY PRECIPITATION IS FORECAST SATURDAY AND SUNDAY IN
THE MOUNTAINS AND A FLOOD WATCH IS IN EFFECT FOR THE RIVERS FLOWING
OFF THE OLYMPICS AND THE NORTH AND CENTRAL CASCADES.

PRECIPITATION WILL INITIALLY FALL AS SNOW IN THE MOUNTAINS WITH SNOW
LEVELS AROUND 3000-4000 FT. WARMER AIR WILL THEN MOVE INLAND
SATURDAY AFTERNOON AND EVENING WITH SNOW LEVELS RISING TO 6000-7000
FT FOR MAINLY RAIN IN THE MOUNTAINS. PRECIPITATION AMOUNTS IN THE
OLYMPICS AND CASCADES ARE GENERALLY AROUND 3-5 INCHES...WITH 6-9
INCHES POSSIBLE AT MOUNT RAINIER.

ANY FLOODING WOULD LIKELY BEGIN AS EARLY AS SATURDAY NIGHT ON THE
SKOKOMISH RIVER. THE CASCADE RIVERS COULD FLOOD SATURDAY NIGHT OR
SUNDAY. MODELS SHOW HEAVY RAIN ENDING SUNDAY NIGHT.

&&

.AVIATION...SCATTERED SHOWERS REMAIN OVER WESTERN WASHINGTON THIS
AFTERNOON. THERE HAVE BEEN ISOLATED THUNDERSTORMS ON THE COAST. A
STRONG FRONTAL SYSTEM WILL REACH THE AREA LATER TONIGHT AND SATURDAY
WITH WESTERLY FLOW ALOFT. THE SHOWERS WILL END THIS EVENING AND RAIN
WILL DEVELOP OVERNIGHT. AT THE SURFACE STRONG SOUTHEAST WINDS WILL
DEVELOP TONIGHT. THE FLOW WILL TURN ONSHORE SATURDAY NIGHT.

CEILINGS ARE GENERALLY VFR WITH SOME MVFR IN SHOWERS. CLOUDS WILL
THICKEN AND LOWER TONIGHT WITH SATURDAY BEING MOSTLY MVFR WITH RAIN.

KSEA...DISCUSSION ABOVE APPLIES. WIND WILL BE SOUTHERLY 10-15 KT
OVERNIGHT INCREASING TO 15G25KT SATURDAY. CHB

&&

.MARINE...A STRONG SYSTEM WILL APPROACH TONIGHT WITH GALES LIKELY
OVER THE COAST...ENTRANCES...AND NORTHERN INLAND WATERS. AFTER A
BRIEF LULL IN WINDS SATURDAY AFTERNOON MODELS SHOW A PERIOD OF
STRONG ONSHORE FLOW SATURDAY NIGHT THAT MAY ALSO HAVE NEAR GALE
SOUTHWEST WINDS OVER MOST WATERS.

A WEAKER SYSTEM ARRIVES MONDAY NIGHT OR TUESDAY.

SWELL ON THE COAST WILL REACH 20 FEET OR SO TONIGHT AND SATURDAY.
COUPLED WITH HIGH TIDES AROUND NOON SATURDAY THERE COULD BE SOME
MINOR TIDAL OVERFLOW AT SPOTS. SO FAR BUOY 5...ABOUT 300 MILES OFF
THE COAST...SHOWS ONLY 21 FOOT SWELLS. THESE WILL DECAY A BIT BEFORE
ARRIVING AT THE COAST. HAVE ISSUED A HIGH SURF ADVISORY FOR THE
WAVES ON THE BEACHES TONIGHT AND SATURDAY AND A COASTAL FLOOD
ADVISORY FOR MINOR FLOODING OF LOW AREAS NEAR THE BEACHES DURING THE
TIME OF HIGH TIDE SATURDAY MORNING.

&&

.SEW WATCHES/WARNINGS/ADVISORIES...

WA...HIGH WIND WARNING COAST...WESTERN WHATCOM...SAN
     JUANS...ADMIRALTY INLET.
     WIND ADVISORY WESTERN SKAGIT COUNTY.
     WINTER WEATHER ADVISORY CASCADES.
     HIGH SURF ADVISORY NORTH AND CENTRAL COAST.
     COASTAL FLOOD ADVISORY NORTH AND CENTRAL COAST SATURDAY MORNING.

PZ...GALE WARNING COAST...ENTRANCES...NORTHERN INLAND WATERS.
     SMALL CRAFT ADVISORY CENTRAL STRAIT...ADMIRALTY INLET...AND
     PUGET SOUND AND HOOD CANAL.
     SMALL CRAFT ADVISORY FOR ROUGH GRAYS HARBOR BAR.

&&

$$

YOU CAN SEE AN ILLUSTRATED VERSION OF THIS FORECAST DISCUSSION AT
WWW.WEATHER.GOV/SEATTLE/GAFD/LATEST_WEBAFD.HTML













000
FXUS66 KSEW 192326
AFDSEW

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SEATTLE WA
330 PM PST FRI DEC 19 2014

.SYNOPSIS...AN UPPER LEVEL TROUGH WILL BRING SCATTERED SHOWERS
TODAY. A PAIR OF STRONG WARM FRONTS WILL BRING RAIN AND WIND
TO WESTERN WASHINGTON TONIGHT THROUGH THIS WEEKEND. AN UPPER LEVEL
RIDGE WILL MOVE BRIEFLY OVER THE REGION MONDAY FOR DRIER WEATHER.
ADDITIONAL FRONTAL SYSTEMS WILL REACH THE REGION NEXT WEEK.

&&

.SHORT TERM...AN UPPER LEVEL TROUGH IS BRINGING SCATTERED SHOWERS TO
WESTERN WA THIS AFTERNOON. THERE WERE A FEW LIGHTNING STRIKES OVER
THE COAST THIS MORNING BUT ACTIVITY HAS SINCE DIMINISHED. THE
TROUGH AXIS WILL EXIT THIS EVENING WITH SHOWERS TAPERING OFF.

ANOTHER ROUND OF WET AND BLUSTERY WEATHER IS ANTICIPATED LATE
TONIGHT THROUGH SATURDAY AS OUR NEXT SYSTEM ARRIVES. THIS SYSTEM MAY
BRING HIGH WIND TO THE COAST AND NORTH INTERIOR A WARM FRONT MOVES
INLAND SATURDAY MORNING. A HIGH WIND WARNING IS IN EFFECT FOR THESE
ZONES. WINDS WILL PEAK AROUND 12-15Z ALONG THE COAST...AND 18-20Z
FOR THE NORTH INTERIOR.

MEANWHILE...A PLUME OF MOISTURE IS BEING TRANSPORTED EAST ALONG A
STRONG 175 KT JET AIMED AT WASHINGTON...WHICH WILL LIKELY RESULT IN
HEAVY PRECIP ALONG THE COAST AND IN THE MOUNTAINS. INITIALLY SNOW
LEVELS WILL HOVER AROUND 3000-4000 FT SATURDAY MORNING BUT WILL RISE
TO 5000-7000 FT SATURDAY AFTERNOON AS WARMER AIR MOVES IN. THE WEST
SLOPES CASCADES COULD SEE BRIEF HEAVY SNOW BEFORE CHANGING OVER TO
RAIN SATURDAY AFTERNOON AND EVENING. THE SNOW LEVELS WILL REMAIN
HIGH SAT NIGHT THROUGH SUN WITH MAINLY RAIN IN THE MOUNTAINS...HEAVY
AT TIMES. THIS MAY RESULT IN RIVER FLOODING AND A FLOOD WATCH WAS
ISSUED. HEAVY RAIN WILL CONTINUE IN THE MOUNTAINS SAT NIGHT INTO SUN
MORNING WITH STRONG WEST WINDS ALOFT. AN UPPER LEVEL RIDGE WILL THEN
BUILD OVER THE AREA SUN NIGHT. THIS RIDGE WILL CUT OFF THE FLOW
WHICH WILL BRING AN END TO THE STEADY/HEAVY PRECIP IN THE MOUNTAINS.
THIS UPPER LEVEL RIDGE WILL REMAIN OVER THE AREA ON MONDAY FOR DRIER
WEATHER. 33

.LONG TERM...MODELS ARE WEAKENING THE RIDGE OVER THE PAC NW ON TUE
WITH WESTERLY FLOW ALOFT OVER THE REGION. A BAROCLINIC BAND WILL
STALL OVER THE AREA FOR MORE RAIN. SNOW LEVELS ARE STILL HIGH AROUND
5000-6000 FT. THERE ARE SOME SLIGHT DIFFERENCES IN THE MODELS WITH
THE ECMWF ABOUT 6 HOURS FASTER THAN THE GFS. AN UPPER LEVEL TROUGH
WILL THEN MOVE INLAND ON WED...SHIFTING THE BAROCLINIC BAND SOUTH OF
THE CWA. NORTHERLY FLOW WILL PREVAIL ON CHRISTMAS DAY FOR MAINLY DRY
WEATHER. THIS PATTERN CONTINUES ON FRIDAY. 33

&&

.HYDROLOGY...HEAVY PRECIPITATION IS FORECAST SATURDAY AND SUNDAY IN
THE MOUNTAINS AND A FLOOD WATCH IS IN EFFECT FOR THE RIVERS FLOWING
OFF THE OLYMPICS AND THE NORTH AND CENTRAL CASCADES.

PRECIPITATION WILL INITIALLY FALL AS SNOW IN THE MOUNTAINS WITH SNOW
LEVELS AROUND 3000-4000 FT. WARMER AIR WILL THEN MOVE INLAND
SATURDAY AFTERNOON AND EVENING WITH SNOW LEVELS RISING TO 6000-7000
FT FOR MAINLY RAIN IN THE MOUNTAINS. PRECIPITATION AMOUNTS IN THE
OLYMPICS AND CASCADES ARE GENERALLY AROUND 3-5 INCHES...WITH 6-9
INCHES POSSIBLE AT MOUNT RAINIER.

ANY FLOODING WOULD LIKELY BEGIN AS EARLY AS SATURDAY NIGHT ON THE
SKOKOMISH RIVER. THE CASCADE RIVERS COULD FLOOD SATURDAY NIGHT OR
SUNDAY. MODELS SHOW HEAVY RAIN ENDING SUNDAY NIGHT.

&&

.AVIATION...SCATTERED SHOWERS REMAIN OVER WESTERN WASHINGTON THIS
AFTERNOON. THERE HAVE BEEN ISOLATED THUNDERSTORMS ON THE COAST. A
STRONG FRONTAL SYSTEM WILL REACH THE AREA LATER TONIGHT AND SATURDAY
WITH WESTERLY FLOW ALOFT. THE SHOWERS WILL END THIS EVENING AND RAIN
WILL DEVELOP OVERNIGHT. AT THE SURFACE STRONG SOUTHEAST WINDS WILL
DEVELOP TONIGHT. THE FLOW WILL TURN ONSHORE SATURDAY NIGHT.

CEILINGS ARE GENERALLY VFR WITH SOME MVFR IN SHOWERS. CLOUDS WILL
THICKEN AND LOWER TONIGHT WITH SATURDAY BEING MOSTLY MVFR WITH RAIN.

KSEA...DISCUSSION ABOVE APPLIES. WIND WILL BE SOUTHERLY 10-15 KT
OVERNIGHT INCREASING TO 15G25KT SATURDAY. CHB

&&

.MARINE...A STRONG SYSTEM WILL APPROACH TONIGHT WITH GALES LIKELY
OVER THE COAST...ENTRANCES...AND NORTHERN INLAND WATERS. AFTER A
BRIEF LULL IN WINDS SATURDAY AFTERNOON MODELS SHOW A PERIOD OF
STRONG ONSHORE FLOW SATURDAY NIGHT THAT MAY ALSO HAVE NEAR GALE
SOUTHWEST WINDS OVER MOST WATERS.

A WEAKER SYSTEM ARRIVES MONDAY NIGHT OR TUESDAY.

SWELL ON THE COAST WILL REACH 20 FEET OR SO TONIGHT AND SATURDAY.
COUPLED WITH HIGH TIDES AROUND NOON SATURDAY THERE COULD BE SOME
MINOR TIDAL OVERFLOW AT SPOTS. SO FAR BUOY 5...ABOUT 300 MILES OFF
THE COAST...SHOWS ONLY 21 FOOT SWELLS. THESE WILL DECAY A BIT BEFORE
ARRIVING AT THE COAST. HAVE ISSUED A HIGH SURF ADVISORY FOR THE
WAVES ON THE BEACHES TONIGHT AND SATURDAY AND A COASTAL FLOOD
ADVISORY FOR MINOR FLOODING OF LOW AREAS NEAR THE BEACHES DURING THE
TIME OF HIGH TIDE SATURDAY MORNING.

&&

.SEW WATCHES/WARNINGS/ADVISORIES...

WA...HIGH WIND WARNING COAST...WESTERN WHATCOM...SAN
     JUANS...ADMIRALTY INLET.
     WIND ADVISORY WESTERN SKAGIT COUNTY.
     WINTER WEATHER ADVISORY CASCADES.
     HIGH SURF ADVISORY NORTH AND CENTRAL COAST.
     COASTAL FLOOD ADVISORY NORTH AND CENTRAL COAST SATURDAY MORNING.

PZ...GALE WARNING COAST...ENTRANCES...NORTHERN INLAND WATERS.
     SMALL CRAFT ADVISORY CENTRAL STRAIT...ADMIRALTY INLET...AND
     PUGET SOUND AND HOOD CANAL.
     SMALL CRAFT ADVISORY FOR ROUGH GRAYS HARBOR BAR.

&&

$$

YOU CAN SEE AN ILLUSTRATED VERSION OF THIS FORECAST DISCUSSION AT
WWW.WEATHER.GOV/SEATTLE/GAFD/LATEST_WEBAFD.HTML











000
FXUS66 KSEW 192326
AFDSEW

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SEATTLE WA
330 PM PST FRI DEC 19 2014

.SYNOPSIS...AN UPPER LEVEL TROUGH WILL BRING SCATTERED SHOWERS
TODAY. A PAIR OF STRONG WARM FRONTS WILL BRING RAIN AND WIND
TO WESTERN WASHINGTON TONIGHT THROUGH THIS WEEKEND. AN UPPER LEVEL
RIDGE WILL MOVE BRIEFLY OVER THE REGION MONDAY FOR DRIER WEATHER.
ADDITIONAL FRONTAL SYSTEMS WILL REACH THE REGION NEXT WEEK.

&&

.SHORT TERM...AN UPPER LEVEL TROUGH IS BRINGING SCATTERED SHOWERS TO
WESTERN WA THIS AFTERNOON. THERE WERE A FEW LIGHTNING STRIKES OVER
THE COAST THIS MORNING BUT ACTIVITY HAS SINCE DIMINISHED. THE
TROUGH AXIS WILL EXIT THIS EVENING WITH SHOWERS TAPERING OFF.

ANOTHER ROUND OF WET AND BLUSTERY WEATHER IS ANTICIPATED LATE
TONIGHT THROUGH SATURDAY AS OUR NEXT SYSTEM ARRIVES. THIS SYSTEM MAY
BRING HIGH WIND TO THE COAST AND NORTH INTERIOR A WARM FRONT MOVES
INLAND SATURDAY MORNING. A HIGH WIND WARNING IS IN EFFECT FOR THESE
ZONES. WINDS WILL PEAK AROUND 12-15Z ALONG THE COAST...AND 18-20Z
FOR THE NORTH INTERIOR.

MEANWHILE...A PLUME OF MOISTURE IS BEING TRANSPORTED EAST ALONG A
STRONG 175 KT JET AIMED AT WASHINGTON...WHICH WILL LIKELY RESULT IN
HEAVY PRECIP ALONG THE COAST AND IN THE MOUNTAINS. INITIALLY SNOW
LEVELS WILL HOVER AROUND 3000-4000 FT SATURDAY MORNING BUT WILL RISE
TO 5000-7000 FT SATURDAY AFTERNOON AS WARMER AIR MOVES IN. THE WEST
SLOPES CASCADES COULD SEE BRIEF HEAVY SNOW BEFORE CHANGING OVER TO
RAIN SATURDAY AFTERNOON AND EVENING. THE SNOW LEVELS WILL REMAIN
HIGH SAT NIGHT THROUGH SUN WITH MAINLY RAIN IN THE MOUNTAINS...HEAVY
AT TIMES. THIS MAY RESULT IN RIVER FLOODING AND A FLOOD WATCH WAS
ISSUED. HEAVY RAIN WILL CONTINUE IN THE MOUNTAINS SAT NIGHT INTO SUN
MORNING WITH STRONG WEST WINDS ALOFT. AN UPPER LEVEL RIDGE WILL THEN
BUILD OVER THE AREA SUN NIGHT. THIS RIDGE WILL CUT OFF THE FLOW
WHICH WILL BRING AN END TO THE STEADY/HEAVY PRECIP IN THE MOUNTAINS.
THIS UPPER LEVEL RIDGE WILL REMAIN OVER THE AREA ON MONDAY FOR DRIER
WEATHER. 33

.LONG TERM...MODELS ARE WEAKENING THE RIDGE OVER THE PAC NW ON TUE
WITH WESTERLY FLOW ALOFT OVER THE REGION. A BAROCLINIC BAND WILL
STALL OVER THE AREA FOR MORE RAIN. SNOW LEVELS ARE STILL HIGH AROUND
5000-6000 FT. THERE ARE SOME SLIGHT DIFFERENCES IN THE MODELS WITH
THE ECMWF ABOUT 6 HOURS FASTER THAN THE GFS. AN UPPER LEVEL TROUGH
WILL THEN MOVE INLAND ON WED...SHIFTING THE BAROCLINIC BAND SOUTH OF
THE CWA. NORTHERLY FLOW WILL PREVAIL ON CHRISTMAS DAY FOR MAINLY DRY
WEATHER. THIS PATTERN CONTINUES ON FRIDAY. 33

&&

.HYDROLOGY...HEAVY PRECIPITATION IS FORECAST SATURDAY AND SUNDAY IN
THE MOUNTAINS AND A FLOOD WATCH IS IN EFFECT FOR THE RIVERS FLOWING
OFF THE OLYMPICS AND THE NORTH AND CENTRAL CASCADES.

PRECIPITATION WILL INITIALLY FALL AS SNOW IN THE MOUNTAINS WITH SNOW
LEVELS AROUND 3000-4000 FT. WARMER AIR WILL THEN MOVE INLAND
SATURDAY AFTERNOON AND EVENING WITH SNOW LEVELS RISING TO 6000-7000
FT FOR MAINLY RAIN IN THE MOUNTAINS. PRECIPITATION AMOUNTS IN THE
OLYMPICS AND CASCADES ARE GENERALLY AROUND 3-5 INCHES...WITH 6-9
INCHES POSSIBLE AT MOUNT RAINIER.

ANY FLOODING WOULD LIKELY BEGIN AS EARLY AS SATURDAY NIGHT ON THE
SKOKOMISH RIVER. THE CASCADE RIVERS COULD FLOOD SATURDAY NIGHT OR
SUNDAY. MODELS SHOW HEAVY RAIN ENDING SUNDAY NIGHT.

&&

.AVIATION...SCATTERED SHOWERS REMAIN OVER WESTERN WASHINGTON THIS
AFTERNOON. THERE HAVE BEEN ISOLATED THUNDERSTORMS ON THE COAST. A
STRONG FRONTAL SYSTEM WILL REACH THE AREA LATER TONIGHT AND SATURDAY
WITH WESTERLY FLOW ALOFT. THE SHOWERS WILL END THIS EVENING AND RAIN
WILL DEVELOP OVERNIGHT. AT THE SURFACE STRONG SOUTHEAST WINDS WILL
DEVELOP TONIGHT. THE FLOW WILL TURN ONSHORE SATURDAY NIGHT.

CEILINGS ARE GENERALLY VFR WITH SOME MVFR IN SHOWERS. CLOUDS WILL
THICKEN AND LOWER TONIGHT WITH SATURDAY BEING MOSTLY MVFR WITH RAIN.

KSEA...DISCUSSION ABOVE APPLIES. WIND WILL BE SOUTHERLY 10-15 KT
OVERNIGHT INCREASING TO 15G25KT SATURDAY. CHB

&&

.MARINE...A STRONG SYSTEM WILL APPROACH TONIGHT WITH GALES LIKELY
OVER THE COAST...ENTRANCES...AND NORTHERN INLAND WATERS. AFTER A
BRIEF LULL IN WINDS SATURDAY AFTERNOON MODELS SHOW A PERIOD OF
STRONG ONSHORE FLOW SATURDAY NIGHT THAT MAY ALSO HAVE NEAR GALE
SOUTHWEST WINDS OVER MOST WATERS.

A WEAKER SYSTEM ARRIVES MONDAY NIGHT OR TUESDAY.

SWELL ON THE COAST WILL REACH 20 FEET OR SO TONIGHT AND SATURDAY.
COUPLED WITH HIGH TIDES AROUND NOON SATURDAY THERE COULD BE SOME
MINOR TIDAL OVERFLOW AT SPOTS. SO FAR BUOY 5...ABOUT 300 MILES OFF
THE COAST...SHOWS ONLY 21 FOOT SWELLS. THESE WILL DECAY A BIT BEFORE
ARRIVING AT THE COAST. HAVE ISSUED A HIGH SURF ADVISORY FOR THE
WAVES ON THE BEACHES TONIGHT AND SATURDAY AND A COASTAL FLOOD
ADVISORY FOR MINOR FLOODING OF LOW AREAS NEAR THE BEACHES DURING THE
TIME OF HIGH TIDE SATURDAY MORNING.

&&

.SEW WATCHES/WARNINGS/ADVISORIES...

WA...HIGH WIND WARNING COAST...WESTERN WHATCOM...SAN
     JUANS...ADMIRALTY INLET.
     WIND ADVISORY WESTERN SKAGIT COUNTY.
     WINTER WEATHER ADVISORY CASCADES.
     HIGH SURF ADVISORY NORTH AND CENTRAL COAST.
     COASTAL FLOOD ADVISORY NORTH AND CENTRAL COAST SATURDAY MORNING.

PZ...GALE WARNING COAST...ENTRANCES...NORTHERN INLAND WATERS.
     SMALL CRAFT ADVISORY CENTRAL STRAIT...ADMIRALTY INLET...AND
     PUGET SOUND AND HOOD CANAL.
     SMALL CRAFT ADVISORY FOR ROUGH GRAYS HARBOR BAR.

&&

$$

YOU CAN SEE AN ILLUSTRATED VERSION OF THIS FORECAST DISCUSSION AT
WWW.WEATHER.GOV/SEATTLE/GAFD/LATEST_WEBAFD.HTML










000
FXUS66 KSEW 191726
AFDSEW

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SEATTLE WA
930 AM PST FRI DEC 19 2014

.SYNOPSIS...AN UPPER LEVEL TROUGH WILL BRING SCATTERED SHOWERS
TODAY. A PAIR OF STRONG WARM FRONTS WILL BRING RAIN AND WIND
TO WESTERN WASHINGTON TONIGHT THROUGH THIS WEEKEND. AN UPPER LEVEL
RIDGE WILL MOVE BRIEFLY OVER THE REGION MONDAY FOR DRIER WEATHER.
ADDITIONAL FRONTAL SYSTEMS WILL REACH THE REGION NEXT WEEK.

&&

.SHORT TERM...AN UPPER LEVEL TROUGH IS PASSING THROUGH WESTERN WA
THIS MORNING FOR SCATTERED SHOWERS ACROSS THE AREA. THERE WERE A FEW
LIGHTNING STRIKES OVER THE COASTAL WATERS BUT THESE CELLS SHOULD
DRIFT N/NE INTO B.C. THE TROUGH AXIS WILL EXIT THIS AFTERNOON WITH
SHOWERS TAPERING OFF. EXPECT HIGHS IN THE LOWER 50S TODAY.

ANOTHER ROUND OF WEST AND BLUSTERY WEATHER IS ANTICIPATED LATE
TONIGHT THROUGH SATURDAY AS OUR NEXT SYSTEM ARRIVES. THIS SYSTEM MAY
BRING HIGH WIND TO THE COAST AND NORTH INTERIOR AS THE OCCLUDED
FRONT MOVES INLAND SATURDAY MORNING. A HIGH WIND WATCH IS IN EFFECT
FOR THESE ZONES. A PLUME OF MOISTURE IS BEING TRANSPORTED EAST ALONG
A STRONG 175 KT JET AIMED AT WASHINGTON...WHICH WILL LIKELY RESULT
IN HEAVY PRECIP ALONG THE COAST AND IN THE MOUNTAINS. INITIALLY SNOW
LEVELS WILL START AROUND 3000-4000 FT SATURDAY MORNING BUT WILL RISE
TO 5000-7000 FT SATURDAY AFTERNOON AS WARMER AIR MOVES IN FROM
ANOTHER WARM FRONT. PARADISE AND MT BAKER COULD SEE BRIEF HEAVY SNOW
BEFORE CHANGING OVER TO RAIN AND MAY NEED A WINTER WEATHER ADVISORY
TO COVER THIS PERIOD. THE SNOW LEVELS WILL REMAIN HIGH SAT NIGHT
THROUGH SUN WITH MAINLY RAIN IN THE MOUNTAINS. THIS MAY RESULT IN
RIVER FLOODING AND A HYDROLOGIC OUTLOOK HAS BEEN ISSUED. AN UPPER
LEVEL RIDGE WILL BUILD OVER THE AREA SUN NIGHT WHICH SHOULD BRING AN
END TO THE STEADY/HEAVY PRECIP IN THE MOUNTAINS. 33

.LONG TERM...PREVIOUS DISCUSSION...BOTH THE GFS AND ECMWF HAVE A
MODERATE AMPLITUDE UPPER LEVEL RIDGE FORMING OFFSHORE MONDAY MORNING
THEN SHIFTING E OVER W WA MONDAY AFTERNOON. BOTH MODELS ALSO SHOW A
SURFACE RIDGE MOVING OVER W WA ON MONDAY...ALTHOUGH THE GFS IS
STRONGER THAN THE ECMWF. THIS WILL END THE WEEKENDS WET WINDY
PERIOD. ANOTHER WEAKER WARM SYSTEM MOVES OVER THE TOP OF THE RIDGE
MONDAY NIGHT AND TUESDAY...BRINGING A QUICK END TO MONDAYS BRIEF DRY
PERIOD. THE GFS AND ECMWF SEEM TO BE IN FAIR AGREEMENT WITH THE
LARGER PATTERN PAST MID NEXT WEEK...BUT WITH THE MODELS CONTINUING
TO EVOLVE FROM RUN-TO-RUN...CONFIDENCE REMAINS LOW. BOTTOM LINE IS
THAT ACTIVE WEATHER WILL PROBABLY BE CONTINUING. KAM

&&

.HYDROLOGY...HEAVY RAIN COULD CAUSE FLOODING BY LATE THIS WEEKEND. A
PAIR OF STRONG WARM FRONTS WILL BRING HEAVY RAIN AT TIMES TO THE
COAST AND OLYMPICS ON SATURDAY. HEAVY RAIN WILL SPREAD INTO THE
CASCADES SATURDAY AFTERNOON BUT MAY NOT BE AS HEAVY AS INITIALLY
EXPECTED.

MODELS CURRENTLY TAPER RAIN OVER THE OLYMPICS SATURDAY NIGHT AND
SUNDAY...BUT THE STRONGER W FLOW ALOFT SATURDAY NIGHT WILL BRING
HEAVY RAIN TO THE CASCADES...ESPECIALLY OVER THE CASCADES FROM ABOUT
KING COUNTY SOUTH. THE CURRENT RAINFALL FORECAST IN THE 36 HOUR
PERIOD FROM 12Z SATURDAY THROUGH 00Z MONDAY HAS 3-5 INCHES OVER THE
OLYMPICS AND ROUGHLY 3 TO 5 INCHES OVER THE CENTRAL CASCADES WITH
ABOUT 7 INCH BULLSEYE OVER MT RAINIER. THIS IS LESS THAN THE
PREVIOUS FORECAST. THE SNOW LEVEL WILL RISE TO 5000 TO 7000 FEET BY
LATE SATURDAY AFTERNOON AND NIGHT...THEN LOWER BACK TO AROUND 5000
FEET ON SUNDAY.

THESE RAINFALL AMOUNTS MAY BE ENOUGH TO CAUSE FLOODING. AT THIS TIME
THE RIVERS MOST LIKELY TO FLOOD ARE THE ONES FLOWING OFF THE
CASCADES OF KING...PIERCE...AND LEWIS COUNTIES...AS WELL AS THE
UNUSUALLY FLOOD-PRONE SKOKOMISH RIVER IN MASON COUNTY. ANY FLOODING
WOULD LIKELY BEGIN AS EARLY AS SATURDAY NIGHT ON THE SKOKOMISH
RIVER. THE CASCADE RIVERS COULD FLOOD SUNDAY WITH CRESTS SUNDAY
NIGHT OR MONDAY.

&&

.AVIATION...A FRONT MOVED INTO THE CASCADES EARLY THIS MORNING.
SCATTERED SHOWERS REMAIN OVER WESTERN WASHINGTON. A STRONGER FRONTAL
SYSTEM WILL REACH THE AREA LATER TONIGHT AND SATURDAY WITH WESTERLY
FLOW ALOFT. THE AIR MASS WILL REMAIN MOIST BUT THERE MAY BE SOME SUN
BREAKS TODAY. INCREASING MOISTURE AGAIN TONIGHT AND SATURDAY WITH
STRONG WESTERLY FLOW ALOFT. AT THE SURFACE STRONG SOUTHEAST WINDS
WILL DEVELOP TONIGHT. THE FLOW WILL TURN ONSHORE SATURDAY NIGHT.

CEILINGS ARE GENERALLY VFR WITH SOME HIGH END MVFR. SHOWERS AND SUN
BREAKS WILL DEVELOP TODAY WITH VFR CEILINGS EXCEPT MVFR IN SHOWERS.
CLOUDS WILL THICKEN AND LOWER TONIGHT WITH SATURDAY BEING MOSTLY
MVFR WITH RAIN.

KSEA...DISCUSSION ABOVE APPLIES. WIND TODAY WILL BE SOUTHERLY 8-12
KT BECOMING SOUTHEAST TONIGHT AND INCREASING SATURDAY. CHB

&&

.MARINE...SMALL CRAFT ADVISORY WINDS ARE LIKELY OVER MOST WATERS
TODAY IN THE WAKE OF A FRONT THAT PASSED LAST NIGHT. A STRONGER
SYSTEM WILL APPROACH TONIGHT WITH GALES LIKELY OVER MOST WATERS.
BOTH THE ADVISORIES AND WARNINGS ARE ALREADY UP FOR THESE WINDS.
AFTER A BRIEF LULL IN WINDS SATURDAY AFTERNOON...MODELS SHOW A
PERIOD OF STRONG ONSHORE FLOW SATURDAY NIGHT THAT WILL ALSO HAVE
GALE SOUTHWEST WINDS OVER MOST WATERS.

A WEAKER SYSTEM ARRIVES MONDAY NIGHT OR TUESDAY.

SWELL ON THE COAST WILL REACH 20 FEET OR SO TONIGHT AND SATURDAY.
COUPLED WITH HIGH TIDES AROUND NOON SATURDAY THERE COULD BE SOME
MINOR TIDAL OVERFLOW AT SPOTS. SO FAR BUOY 5...ABOUT 300 MILES OFF
THE COAST...SHOWS ONLY 20 FOOT SWELLS. THESE WILL DECAY A BIT BEFORE
ARRIVING AT THE COAST. WILL DECIDE WHAT TO DO WITH THE COASTAL FLOOD
WATCH THIS AFTERNOON. CHB

&&

.SEW WATCHES/WARNINGS/ADVISORIES...

WA...WINTER WEATHER ADVISORY THROUGH 6 AM FOR THE OLYMPICS AND
     CASCADES.
     HIGH WIND WATCH FOR THE COAST AND NORTH INTERIOR LATE TONIGHT
      THROUGH SATURDAY EVENING.
     HIGH SURF ADVISORY FOR THE NORTH AND CENTRAL COAST FROM LATE
      THIS MORNING THROUGH EARLY SATURDAY MORNING.
     COASTAL FLOOD WATCH FOR THE NORTH AND CENTRAL COAST FROM
      SATURDAY MORNING THROUGH SATURDAY AFTERNOON.

PZ...SMALL CRAFT ADVISORY ALL WATERS EXCEPT PUGET SOUND AND
      THE CENTRAL STRAIT OF JUAN DE FUCA THROUGH THIS EVENING.
     GALE WARNING ALL WATERS EXCEPT THE CENTRAL STRAIT AND PUGET
      SOUND LATER TONIGHT THROUGH SAT.
     SMALL CRAFT ADVISORY GRAYS HARBOR BAR.

&&

$$

YOU CAN SEE AN ILLUSTRATED VERSION OF THIS FORECAST DISCUSSION AT
WWW.WEATHER.GOV/SEATTLE/GAFD/LATEST_WEBAFD.HTML







000
FXUS66 KSEW 191143
AFDSEW

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SEATTLE WA
344 AM PST FRI DEC 19 2014

.SYNOPSIS...AN UPPER LEVEL TROUGH WILL BRING SHOWERS TO THE COAST
AND SCATTERED SHOWERS INLAND TODAY. A PAIR OF STRONG WARM FRONTS
WILL BRING RAIN AND WIND TO WESTERN WASHINGTON TONIGHT THROUGH THIS
WEEKEND. AN UPPER LEVEL RIDGE WILL MOVE BRIEFLY OVER THE REGION
MONDAY FOR DRIER WEATHER. ADDITIONAL FRONTAL SYSTEMS WILL REACH THE
REGION NEXT WEEK.

&&

.SHORT TERM...IR SATELLITE IMAGERY AND RADAR SHOWS LAST EVENINGS
COLD FRONT HAS MOVED EAST OF THE AREA. THE UPPER LEVEL TROUGH JUST
OFFSHORE WILL MOVE INLAND OVER W WA LATE THIS MORNING THEN WEAKEN
RAPIDLY AS IT MOVES E OF THE CASCADES THIS AFTERNOON. THE AIR MASS
WILL BE UNSTABLE TODAY WITH NUMEROUS SHOWERS ALONG THE COAST AND
SCATTERED SHOWERS INLAND. GFS SHOWS LIFTED INDICES AS LOW AS -2 OVER
THE COASTAL WATERS TODAY...BUT WITH VERY LITTLE LIGHTNING ACTIVITY
SO FAR I WILL LEAVE OUT THE MENTION OF THUNDERSTORMS.

A STRONG ZONAL JETSTREAM HAS FORMED OVER THE NE PACIFIC AND WILL
DRIVE A COUPLE OF STRONG WET WARM FRONTS ACROSS W WA TONIGHT THROUGH
THIS WEEKEND. MODEL SOLUTIONS ARE IN FAIRLY GOOD AGREEMENT THROUGH
SATURDAY...BUT CONTINUE TO EVOLVE REGARDING SOME DETAILS AND
ESPECIALLY WITH REGARD TO PRECIP AMOUNTS.

THERE IS GOOD CONSISTENCY AND AGREEMENT THAT LIGHT RAIN WILL DEVELOP
THIS EVENING AS THE FIRST STRONG WARM FRONT APPROACHES THE REGION.
GFS/ECMWF BRING THIS FIRST WARM FRONT TO THE COAST EARLY SATURDAY
MORNING. STRONG S-SE WINDS WILL DEVELOP ALONG THE COAST AND OVER THE
N INTERIOR LATE TONIGHT AHEAD OF THE WARM FRONT. A HIGH WIND WATCH
WILL BE ISSUED FOR THESE AREAS.

A NEW WRINKLE IS THAT THE MODELS RESOLVE A SECOND WARM FRONT
TRAILING RIGHT BEHIND THE FIRST. THE SECOND WARM FRONT SHOULD REACH
THE WA COAST LATE SATURDAY AFTERNOON...WITH AN ASSOCIATED WEAK
SURFACE LOW MOVING ACROSS VANCOUVER ISLAND EARLY SATURDAY EVENING.
IT NOW LOOKS LIKE THERE WILL BE A BRIEF LULL IN THE STRONG S-SE
WINDS BETWEEN THE TWO WARM FRONTS...BUT THERE WILL BE A SURGE OF
W-SW WIND BEHIND THE SURFACE LOW SATURDAY EVENING. THE HIGH WIND
WATCH RUNS THROUGH SATURDAY EVENING TO COVER THE SECOND WARM FRONT
AND THE TRAILING SURFACE LOW. MODELS HAVE BEEN PRETTY CONSISTENT
SHOWING UP TO HIGH END WIND ADVISORY WINDS FOR THE COAST/N INTERIOR
THROUGH THIS PERIOD...BUT THERE IS STILL SOME UNCERTAINTY REGARDING
THE STRENGTH OF EACH OF THESE FEATURES. SOME SPOTTY HIGH WINDS ARE
WITHIN REACH...HENCE THE HIGH WIND WATCH.

PERIODS OF HEAVY RAIN ARE STILL EXPECTED OVER THE MOUNTAINS...BUT
RESOLVING THESE FEATURES INTO TWO WARM FRONTS WITH A SURFACE LOW HAS
HAD AN IMPACT ON THE MID LEVEL WIND FIELD WHICH WILL GENERATE
THE UPSLOPE FLOW OVER THE MOUNTAINS. STRONG S FLOW DEVELOPS TONIGHT
AHEAD OF THE FIRST WARM FRONT...BUT RATHER THAN SHIFTING DIRECTLY TO
W BEHIND THE FIRST WARM FRONT...THE FLOW SHIFTS SW WITH A BRIEF LESS
WET PERIOD THROUGH MIDDAY SATURDAY BETWEEN THE WARM FRONTS. STRONG W
FLOW ALOFT DEVELOPS BEHIND THE SECOND WARM FRONT EARLY SATURDAY
EVENING AND CONTINUES THROUGH SATURDAY NIGHT AS THE SURFACE LOW
MOVES INLAND. THE STRONG W FLOW IS WHAT WILL BRING HEAVY RAIN TO THE
CASCADES. OVERALL THE MODELS HAVE BACKED OFF ON RAINFALL AMOUNTS IN
SOME OF THE PERIODS THIS WEEKEND...BUT NOT ALL THE MODELS ARE
CONSISTENT. HEAVY RAIN WILL STILL FALL OVER THE MOUNTAINS WITH 3-5
INCHES OVER THE OLYMPICS AND 3 TO 6+ INCHES OVER MAINLY THE CENTRAL
CASCADES IN THE 36 HOURS FROM 12Z SATURDAY THROUGH 00Z MONDAY...BUT
CONFIDENCE IN THE FORECAST RAINFALL AMOUNTS IS LOWER.

LASTLY THERE COULD BE SOME LOCALLY HEAVY SNOW OVER THE CASCADES
SATURDAY MORNING. COOL AIR FROM TODAYS UPPER LEVEL TROUGH WILL DROP
SNOW LEVELS DOWN TO AROUND 3000 FEET EARLY SATURDAY MORNING. SNOW
LEVELS WILL GRADUALLY RISE TO 5000-7000 FEET BY LATE SATURDAY
AFTERNOON AS THE WARM FRONTS CROSS THE AREA...BUT DURING THE
TRANSITION...UP TO A FOOT OF SNOW COULD FALL OVER MT RAINIER AND MT
BAKER...WITH POSSIBLY UP TO 6-9 INCHES AROUND STEVENS PASS SATURDAY
MORNING. OF COURSE THE SAME UNCERTAINTY REGARDING RAINFALL AMOUNTS
AFFECTS SNOW ACCUMULATIONS. A WINTER WEATHER ADVISORY MAY BE NEEDED
TO ADDRESS THE EARLY SATURDAY SNOW.

W FLOW ALOFT WILL GRADUALLY WEAKEN ON SUNDAY. A CONVERGENCE ZONE MAY
DEVELOP OVER PUGET SOUND ON SUNDAY. KAM

.LONG TERM...BOTH THE GFS AND ECMWF HAVE A MODERATE AMPLITUDE UPPER
LEVEL RIDGE FORMING OFFSHORE MONDAY MORNING THEN SHIFTING E OVER W
WA MONDAY AFTERNOON. BOTH MODELS ALSO SHOW A SURFACE RIDGE MOVING
OVER W WA ON MONDAY...ALTHOUGH THE GFS IS STRONGER THAN THE ECMWF.
THIS WILL END THE WEEKENDS WET WINDY PERIOD. ANOTHER WEAKER WARM
SYSTEM MOVES OVER THE TOP OF THE RIDGE MONDAY NIGHT AND
TUESDAY...BRINGING A QUICK END TO MONDAYS BRIEF DRY PERIOD. THE GFS
AND ECMWF SEEM TO BE IN FAIR AGREEMENT WITH THE LARGER PATTERN PAST
MID NEXT WEEK...BUT WITH THE MODELS CONTINUING TO EVOLVE FROM
RUN-TO-RUN...CONFIDENCE REMAINS LOW. BOTTOM LINE IS THAT ACTIVE
WEATHER WILL PROBABLY BE CONTINUING. KAM

&&

.HYDROLOGY...THOUGH RAIN WILL FALL AT TIMES...FLOODING IS UNLIKELY
ON ANY RIVER THROUGH SATURDAY.

HEAVY RAIN COULD CAUSE FLOODING BY LATE THIS WEEKEND. A PAIR OF
STRONG WARM FRONTS WILL BRING HEAVY RAIN AT TIMES TO THE COAST AND
OLYMPICS ON SATURDAY. HEAVY RAIN WILL SPREAD INTO THE CASCADES
SATURDAY AFTERNOON BUT MAY NOT BE AS HEAVY AS INITIALLY EXPECTED.

MODELS CURRENTLY TAPER RAIN OVER THE OLYMPICS SATURDAY NIGHT AND
SUNDAY...BUT THE STRONGER W FLOW ALOFT SATURDAY NIGHT WILL BRING
HEAVY RAIN TO THE CASCADES...ESPECIALLY OVER THE CASCADES FROM ABOUT
KING COUNTY SOUTH. THE CURRENT RAINFALL FORECAST IN THE 36 HOUR
PERIOD FROM 12Z SATURDAY THROUGH 00Z MONDAY HAS 3-5 INCHES OVER THE
OLYMPICS AND ROUGHLY 3 TO 5 INCHES OVER THE CENTRAL CASCADES WITH
ABOUT 7 INCH BULLSEYE OVER MT RAINIER. THIS IS LESS THAN THE
PREVIOUS FORECAST. AS MENTIONED IN THE SHORT-TERM SECTION
ABOVE...WITH THE EVOLUTION OF THE MID LEVEL WIND FIELD...CONFIDENCE
IN TOTAL RAIN FALL AMOUNTS IS LOWER.

THE SNOW LEVEL WILL RISE TO 5000 TO 7000 FEET BY LATE SATURDAY
AFTERNOON ND NIGHT...THEN LOWER BACK TO AROUND 5000 FEET ON SUNDAY.

THESE RAINFALL AMOUNTS MAY BE ENOUGH TO CAUSE FLOODING. AT THIS TIME
THE RIVERS MOST LIKELY TO FLOOD ARE THE ONES FLOWING OFF THE
CASCADES OF KING...PIERCE...AND LEWIS COUNTIES...AS WELL AS THE
UNUSUALLY FLOOD-PRONE SKOKOMISH RIVER IN MASON COUNTY. ANY FLOODING
WOULD LIKELY BEGIN AS EARLY AS SATURDAY NIGHT ON THE SKOKOMISH
RIVER. THE CASCADE RIVERS COULD FLOOD SUNDAY WITH CRESTS SUNDAY
NIGHT OR MONDAY. KAM

&&

.AVIATION...A FRONT OVER WESTERN WA EARLY THIS MORNING WAS MOVING
INLAND WITH RAIN TURNING TO SHOWERS. A STRONGER FRONTAL SYSTEM WILL
REACH THE AREA LATER TONIGHT AND SATURDAY. THE AIR WILL STAY MOIST
BUT THERE MAY BE SOME SUNBREAKS TODAY...THEN THERE WILL BE
INCREASING MOISTURE AGAIN TONIGHT AND SATURDAY WITH STRONG SW FLOW
ALOFT. A DEEP LOW PRESSURE AREA WILL BE IN THE NE PACIFIC.

KSEA...RAIN TURNING TO SHOWERS EARLY THIS MORNING...SOME SUNBREAKS
AREA POSSIBLE TODAY. THEN RAIN WILL INCREASE AGAIN TONIGHT AND
SATURDAY WILL BE WET AND BLUSTERY.

&&

.MARINE...A FRONT OVER WESTERN WA EARLY THIS MORNING WILL MOVE
INLAND. A STRONGER FRONTAL SYSTEM WILL REACH THE AREA TONIGHT AND
SATURDAY. THERE ARE SMALL CRAFT ADVISORIES UP FOR MOST AREA INTO
THIS EVENING...AND THEN OVERNIGHT TONIGHT AND SATURDAY THERE WILL BE
GALES MOST WATERS. COASTAL SEAS ARE EXPECTED TO PEAK THIS EVENING
AROUND 22 FT.

&&

.SEW WATCHES/WARNINGS/ADVISORIES...

WA...WINTER WEATHER ADVISORY THROUGH 6 AM FOR THE OLYMPICS AND
      CASCADES.
     HIGH WIND WATCH FOR THE COAST AND NORTH INTERIOR LATE TONIGHT
      THROUGH SATURDAY EVENING.
     HIGH SURF ADVISORY FOR THE NORTH AND CENTRAL COAST FROM LATE
      THIS MORNING THROUGH EARLY SATURDAY MORNING.
     COASTAL FLOOD WATCH FOR THE NORTH AND CENTRAL COAST FROM
      SATURDAY MORNING THROUGH SATURDAY AFTERNOON.

PZ...GALE WARNING EAST ENTRANCE STRAIT.
     SMALL CRAFT ADVISORY ALL REMAINING WATERS.
     SMALL CRAFT ADVISORY FOR ROUGH/SEVERE GRAYS HARBOR BAR
       CONDITIONS.
     GALE WATCH COAST...ENTRANCES TO THE STRAIT OF JUAN DE FUCA...
     ADMIRALTY INLET...AND NORTHERN INLAND WATERS FRIDAY NIGHT
     THROUGH SATURDAY.

&&

$$

YOU CAN SEE AN ILLUSTRATED VERSION OF THIS FORECAST DISCUSSION AT
WWW.WEATHER.GOV/SEATTLE/GAFD/LATEST_WEBAFD.HTML









000
FXUS66 KSEW 190441 CCA
AFDSEW

AREA FORECAST DISCUSSION...CORRECTED ADVISORIES
NATIONAL WEATHER SERVICE SEATTLE WA
900 PM PST THU DEC 18 2014

.SYNOPSIS...A FRONT WILL BRING RAINY AND LOCALLY WINDY WEATHER TO
WESTERN WASHINGTON TONIGHT...FOLLOWED BY AN UPPER TROUGH AND
SCATTERED SHOWERS FRIDAY. A FRONTAL SYSTEM WILL MOVE THROUGH
SATURDAY...FOLLOWED BY MOIST WESTERLY FLOW ON SUNDAY. PRECIPITATION
WILL BE ESPECIALLY HEAVY IN THE MOUNTAINS. THE WEATHER WILL BE
SOMEWHAT DRIER EARLY NEXT WEEK WITH AN UPPER RIDGE OVER THE AREA.

&&

.SHORT TERM...A VIGOROUS FRONTAL SYSTEM IS MOVING INTO THE PACIFIC
NORTHWEST THIS EVENING...WITH RAIN FALLING ACROSS MOST OF WESTERN
WASHINGTON. SOUTHEAST WINDS ARE GUSTING INTO THE 25 TO 35 MPH RANGE
ALONG THE COAST AND IN THE NORTH INTERIOR.

THE SURFACE FRONT MADE LANDFALL ON THE NORTH WASHINGTON COAST JUST
AFTER 7 PM...AND IT SHOULD MOVE THROUGH THE WESTERN WASHINGTON
INTERIOR LATE THIS EVENING OR AROUND MIDNIGHT. LIGHT TO MODERATE
PRECIPITATION AND LOCALLY WINDY CONDITIONS WILL CONTINUE THROUGH THE
FRONTAL PASSAGE. WINDS WILL EASE AND PRECIPITATION WILL DECREASE
OVERNIGHT. THE SNOW LEVEL WILL BE IN THE 4000 TO 5000 FT RANGE AS
THIS SYSTEM MOVES THROUGH...ALTHOUGH EASTERLY WINDS IN THE PASSES
COULD KEEP THE SNOW LEVEL LOCALLY LOWER. SEVERAL INCHES MORE
SNOWFALL CAN BE EXPECTED OVERNIGHT.

THE POST-FRONTAL UPPER TROUGH WILL MOVE THROUGH THE AREA FRIDAY...
AND IT SHOULD BE A SHOWERY DAY IN THE COOLER AND WEAKLY UNSTABLE AIR
MASS. THE SNOW LEVEL WILL BE 3000 TO 4000 FT WITH UP TO 4 INCHES OF
ADDITIONAL SNOW IN THE MOUNTAINS.

ANOTHER MORE VIGOROUS FRONTAL SYSTEM WILL SPREAD PRECIPITATION INTO
WESTERN WASHINGTON FRIDAY NIGHT...WITH THE CORE OF THE SYSTEM MOVING
THROUGH SATURDAY AND SATURDAY NIGHT. THIS SYSTEM WILL BRING SOMEWHAT
WINDIER CONDITIONS TO MAINLY THE COAST AND NORTH INTERIOR...WHERE A
HIGH-END WIND ADVISORY EVENT IS LIKELY -- MEANING SUSTAINED WINDS UP
TO 35 MPH AND GUSTS UP TO 55 MPH. THE SNOW LEVEL WILL BE 2500 TO
3500 FT AS PRECIPITATION BEGINS...BUT IT WILL RISE QUICKLY TO 5500
TO 7000 FT SATURDAY NIGHT. PRECIPITATION AMOUNTS WITH THIS SYSTEM
WILL BE SIGNIFICANT...AS DISCUSSED IN MORE DETAIL IN THE HYDROLOGY
SECTION BELOW.

MOIST WESTERLY FLOW WILL FOLLOW THE SYSTEM ON SUNDAY WITH AREAS OF
MODERATE TO HEAVY PRECIPITATION CONTINUING...ESPECIALLY IN THE
MOUNTAINS.   MCDONNAL

.LONG TERM...HERE IS THE LONG TERM SECTION FROM THE AFTERNOON
FORECAST DISCUSSION -- THE EXTENDED FORECAST REMAINS CHALLENGING
WITH A WIDE RANGE OF SOLUTIONS AMONG THE MODELS. THERE IS SOME
AGREEMENT THAT MONDAY WILL GENERALLY FEATURE SHOWERS OR A LULL IN
RAINFALL AS HIGHER PRESSURE BUILDS ALOFT. MODELS DO NOT AGREE ON THE
STRENGTH OR TRACK OF THE NEXT SYSTEM APPROACHING FROM THE W ON
TUESDAY. THE LATEST 12/18Z GFS BRINGS THE LOW IN FURTHER N WHICH
WOULD STILL PRODUCE WARM ADVECTION RAINFALL ACROSS THE AREA...THOUGH
NOT AS MUCH AS WAS SHOWN BY PREVIOUS SOLUTIONS.

MOST MODELS DIG A COLD UPPER TROUGH SWD OUT OF B.C. THROUGH WRN WA
ON WEDNESDAY. THIS COULD USHER IN COOLER AIR BUT MODELS DISAGREE ON
THE EXTENT OF RIDGING OFFSHORE AND WHERE IT SETS UP. THE ECMWF
CONTINUES TO BE ONE OF THE COLDER SOLUTIONS AND HAS THE KONA LOW CUT
OFF FURTHER W...THUS A FURTHER W DEVELOPMENT OF THE UPPER RIDGE. THE
KONA LOW IS FURTHER E ON THE GFS40 WITH A RIDGE NEAR 135-140 WHICH
WILL STILL USHER IN COOLER NLY FLOW BUT PERHAPS LESS CHANCE OF
PRECIPITATION. IT WILL BE INTERESTING TO SEE HOW THIS PANS OUT BUT A
SWITCH TO COOLER OR COLD TEMPERATURES IS A POSSIBILITY BY THURSDAY.
POPS WERE TRIMMED WAY BACK AND MAY NEED TO BE REMOVED ALTOGETHER IF
MODEL TRENDS CONTINUE. SNOW LEVELS WILL ALSO BE MUCH
LOWER...POSSIBLY TO SEA LEVEL...BUT IT IS VERY UNCLEAR AS TO HOW
MUCH MOISTURE WILL REMAIN BY THAT TIME.

&&

.HYDROLOGY...THOUGH RAIN WILL FALL AT TIMES...FLOODING IS UNLIKELY
ON ANY RIVER THROUGH SATURDAY.

HEAVY RAIN COULD CAUSE FLOODING BY LATE THIS WEEKEND. A WEATHER
SYSTEM WITH STRONG WESTERLY FLOW ALOFT WILL BRING HEAVY RAIN AT
TIMES TO THE COAST AND OLYMPICS ON SATURDAY. HEAVY RAIN WILL SPREAD
INTO THE CASCADES SATURDAY AFTERNOON.

MODELS CURRENTLY TAPER RAIN OVER THE OLYMPICS ON SUNDAY BUT KEEP
HEAVY RAIN GOING IN THE CASCADES...ESPECIALLY OVER THE CASCADES FROM
ABOUT KING COUNTY SOUTH. THE TOTAL MODEL RAINFALL OVER ABOUT 48
HOURS FROM SATURDAY MORNING THROUGH SUNDAY NIGHT AMOUNTS TO AROUND
FOUR TO SIX INCHES OVER THE OLYMPICS AND CENTRAL CASCADES WITH A
TEN-INCH BULLSEYE OVER MOUNT RAINIER. THE SNOW LEVEL WILL BE ABOVE
5000 FEET ON SATURDAY AND SUNDAY BEFORE FALLING TO 3500 FEET OR SO
SUNDAY NIGHT.

THESE RAINFALL AMOUNTS ARE ENOUGH TO CAUSE FLOODING. AT THIS TIME
THE RIVERS MOST LIKELY TO FLOOD ARE THE ONES FLOWING OFF THE
CASCADES OF KING...PIERCE...AND LEWIS COUNTIES...AS WELL AS THE
UNUSUALLY FLOOD-PRONE SKOKOMISH RIVER IN MASON COUNTY. ANY FLOODING
WOULD LIKELY BEGIN AS EARLY AS SATURDAY NIGHT ON THE SKOKOMISH
RIVER. THE CASCADE RIVERS COULD FLOOD SUNDAY WITH CRESTS SUNDAY
NIGHT OR MONDAY.

A COOLER AND DRIER AIR MASS IS FORECAST TO BE OVER THE AREA NEXT
WEEK. AFTER MONDAY THE RIVERS WILL RECEDE AND ANY FURTHER FLOODING
IS UNLIKELY. BURKE

&&

.AVIATION...A FRONT OVER WESTERN WA THIS EVENING WILL MOVE INLAND
OVERNIGHT. A STRONGER FRONT WILL REACH THE AREA FRIDAY NIGHT AND
SATURDAY MORNING. RAIN TONIGHT WILL CHANGE TO SHOWERS...AND THEN
BACK TO RAIN FRIDAY NIGHT. THE AIR WILL BE MOIST...THEN SOME
SUNBREAKS FRIDAY...THEN INCREASING MOISTURE AGAIN FRIDAY NIGHT. SW
FLOW ALOFT.

KSEA...RAIN TURNING TO SHOWERS...SOME SUNBREAKS POSSIBLE
FRIDAY...THEN BACK TO RAIN FRIDAY NIGHT. SOUTHERLY BREEZE.

&&

.MARINE...A FRONT OVER WESTERN WA THIS EVENING WILL MOVE INLAND
OVERNIGHT. A STRONGER FRONT WILL REACH THE AREA FRIDAY NIGHT AND
SATURDAY MORNING. THE WIND HAS FALLEN OFF OVER THE COASTAL WATERS
THIS EVENING BEHIND THE FRONT...BUT THERE IS STILL A GALE WARNING UP
FOR THE EAST ENTRANCE WHERE SMITH ISLAND STILL HAD 30-40KT SE WINDS
AT 8PM. THE SWELL WILL RISE THROUGH FRIDAY NIGHT...PEAKING AROUND 22
FT.

&&

.SEW WATCHES/WARNINGS/ADVISORIES...

WA...WIND ADVISORY THROUGH TONIGHT FOR THE SAN JUAN ISLANDS...
     WESTERN WHATCOM COUNTY...AND THE ADMIRALTY INLET AREA.
     WINTER WEATHER ADVISORY THROUGH TONIGHT FOR THE OLYMPICS.
     WINTER WEATHER ADVISORY FOR THE WEST SLOPES OF THE CASCADES
     4 PM PST THIS AFTERNOON THROUGH TONIGHT.
     HIGH SURF ADVISORY FOR THE NORTH AND CENTRAL COAST FROM LATE
     FRIDAY MORNING THROUGH EARLY SATURDAY MORNING.
     COASTAL FLOOD WATCH FOR THE NORTH AND CENTRAL COAST FROM
     SATURDAY MORNING THROUGH SATURDAY AFTERNOON.

PZ...GALE WARNING EAST ENTRANCE STRAIT.
     SMALL CRAFT ADVISORY ALL REMAINING WATERS.
     SMALL CRAFT ADVISORY FOR ROUGH/SEVERE GRAYS HARBOR BAR
       CONDITIONS.
     GALE WATCH COAST...ENTRANCES TO THE STRAIT OF JUAN DE FUCA...
     ADMIRALTY INLET...AND NORTHERN INLAND WATERS FRIDAY NIGHT
     THROUGH SATURDAY.

&&

$$

YOU CAN SEE AN ILLUSTRATED VERSION OF THIS FORECAST DISCUSSION AT
WWW.WEATHER.GOV/SEATTLE/GAFD/LATEST_WEBAFD.HTML






000
FXUS66 KSEW 190441 CCA
AFDSEW

AREA FORECAST DISCUSSION...CORRECTED ADVISORIES
NATIONAL WEATHER SERVICE SEATTLE WA
900 PM PST THU DEC 18 2014

.SYNOPSIS...A FRONT WILL BRING RAINY AND LOCALLY WINDY WEATHER TO
WESTERN WASHINGTON TONIGHT...FOLLOWED BY AN UPPER TROUGH AND
SCATTERED SHOWERS FRIDAY. A FRONTAL SYSTEM WILL MOVE THROUGH
SATURDAY...FOLLOWED BY MOIST WESTERLY FLOW ON SUNDAY. PRECIPITATION
WILL BE ESPECIALLY HEAVY IN THE MOUNTAINS. THE WEATHER WILL BE
SOMEWHAT DRIER EARLY NEXT WEEK WITH AN UPPER RIDGE OVER THE AREA.

&&

.SHORT TERM...A VIGOROUS FRONTAL SYSTEM IS MOVING INTO THE PACIFIC
NORTHWEST THIS EVENING...WITH RAIN FALLING ACROSS MOST OF WESTERN
WASHINGTON. SOUTHEAST WINDS ARE GUSTING INTO THE 25 TO 35 MPH RANGE
ALONG THE COAST AND IN THE NORTH INTERIOR.

THE SURFACE FRONT MADE LANDFALL ON THE NORTH WASHINGTON COAST JUST
AFTER 7 PM...AND IT SHOULD MOVE THROUGH THE WESTERN WASHINGTON
INTERIOR LATE THIS EVENING OR AROUND MIDNIGHT. LIGHT TO MODERATE
PRECIPITATION AND LOCALLY WINDY CONDITIONS WILL CONTINUE THROUGH THE
FRONTAL PASSAGE. WINDS WILL EASE AND PRECIPITATION WILL DECREASE
OVERNIGHT. THE SNOW LEVEL WILL BE IN THE 4000 TO 5000 FT RANGE AS
THIS SYSTEM MOVES THROUGH...ALTHOUGH EASTERLY WINDS IN THE PASSES
COULD KEEP THE SNOW LEVEL LOCALLY LOWER. SEVERAL INCHES MORE
SNOWFALL CAN BE EXPECTED OVERNIGHT.

THE POST-FRONTAL UPPER TROUGH WILL MOVE THROUGH THE AREA FRIDAY...
AND IT SHOULD BE A SHOWERY DAY IN THE COOLER AND WEAKLY UNSTABLE AIR
MASS. THE SNOW LEVEL WILL BE 3000 TO 4000 FT WITH UP TO 4 INCHES OF
ADDITIONAL SNOW IN THE MOUNTAINS.

ANOTHER MORE VIGOROUS FRONTAL SYSTEM WILL SPREAD PRECIPITATION INTO
WESTERN WASHINGTON FRIDAY NIGHT...WITH THE CORE OF THE SYSTEM MOVING
THROUGH SATURDAY AND SATURDAY NIGHT. THIS SYSTEM WILL BRING SOMEWHAT
WINDIER CONDITIONS TO MAINLY THE COAST AND NORTH INTERIOR...WHERE A
HIGH-END WIND ADVISORY EVENT IS LIKELY -- MEANING SUSTAINED WINDS UP
TO 35 MPH AND GUSTS UP TO 55 MPH. THE SNOW LEVEL WILL BE 2500 TO
3500 FT AS PRECIPITATION BEGINS...BUT IT WILL RISE QUICKLY TO 5500
TO 7000 FT SATURDAY NIGHT. PRECIPITATION AMOUNTS WITH THIS SYSTEM
WILL BE SIGNIFICANT...AS DISCUSSED IN MORE DETAIL IN THE HYDROLOGY
SECTION BELOW.

MOIST WESTERLY FLOW WILL FOLLOW THE SYSTEM ON SUNDAY WITH AREAS OF
MODERATE TO HEAVY PRECIPITATION CONTINUING...ESPECIALLY IN THE
MOUNTAINS.   MCDONNAL

.LONG TERM...HERE IS THE LONG TERM SECTION FROM THE AFTERNOON
FORECAST DISCUSSION -- THE EXTENDED FORECAST REMAINS CHALLENGING
WITH A WIDE RANGE OF SOLUTIONS AMONG THE MODELS. THERE IS SOME
AGREEMENT THAT MONDAY WILL GENERALLY FEATURE SHOWERS OR A LULL IN
RAINFALL AS HIGHER PRESSURE BUILDS ALOFT. MODELS DO NOT AGREE ON THE
STRENGTH OR TRACK OF THE NEXT SYSTEM APPROACHING FROM THE W ON
TUESDAY. THE LATEST 12/18Z GFS BRINGS THE LOW IN FURTHER N WHICH
WOULD STILL PRODUCE WARM ADVECTION RAINFALL ACROSS THE AREA...THOUGH
NOT AS MUCH AS WAS SHOWN BY PREVIOUS SOLUTIONS.

MOST MODELS DIG A COLD UPPER TROUGH SWD OUT OF B.C. THROUGH WRN WA
ON WEDNESDAY. THIS COULD USHER IN COOLER AIR BUT MODELS DISAGREE ON
THE EXTENT OF RIDGING OFFSHORE AND WHERE IT SETS UP. THE ECMWF
CONTINUES TO BE ONE OF THE COLDER SOLUTIONS AND HAS THE KONA LOW CUT
OFF FURTHER W...THUS A FURTHER W DEVELOPMENT OF THE UPPER RIDGE. THE
KONA LOW IS FURTHER E ON THE GFS40 WITH A RIDGE NEAR 135-140 WHICH
WILL STILL USHER IN COOLER NLY FLOW BUT PERHAPS LESS CHANCE OF
PRECIPITATION. IT WILL BE INTERESTING TO SEE HOW THIS PANS OUT BUT A
SWITCH TO COOLER OR COLD TEMPERATURES IS A POSSIBILITY BY THURSDAY.
POPS WERE TRIMMED WAY BACK AND MAY NEED TO BE REMOVED ALTOGETHER IF
MODEL TRENDS CONTINUE. SNOW LEVELS WILL ALSO BE MUCH
LOWER...POSSIBLY TO SEA LEVEL...BUT IT IS VERY UNCLEAR AS TO HOW
MUCH MOISTURE WILL REMAIN BY THAT TIME.

&&

.HYDROLOGY...THOUGH RAIN WILL FALL AT TIMES...FLOODING IS UNLIKELY
ON ANY RIVER THROUGH SATURDAY.

HEAVY RAIN COULD CAUSE FLOODING BY LATE THIS WEEKEND. A WEATHER
SYSTEM WITH STRONG WESTERLY FLOW ALOFT WILL BRING HEAVY RAIN AT
TIMES TO THE COAST AND OLYMPICS ON SATURDAY. HEAVY RAIN WILL SPREAD
INTO THE CASCADES SATURDAY AFTERNOON.

MODELS CURRENTLY TAPER RAIN OVER THE OLYMPICS ON SUNDAY BUT KEEP
HEAVY RAIN GOING IN THE CASCADES...ESPECIALLY OVER THE CASCADES FROM
ABOUT KING COUNTY SOUTH. THE TOTAL MODEL RAINFALL OVER ABOUT 48
HOURS FROM SATURDAY MORNING THROUGH SUNDAY NIGHT AMOUNTS TO AROUND
FOUR TO SIX INCHES OVER THE OLYMPICS AND CENTRAL CASCADES WITH A
TEN-INCH BULLSEYE OVER MOUNT RAINIER. THE SNOW LEVEL WILL BE ABOVE
5000 FEET ON SATURDAY AND SUNDAY BEFORE FALLING TO 3500 FEET OR SO
SUNDAY NIGHT.

THESE RAINFALL AMOUNTS ARE ENOUGH TO CAUSE FLOODING. AT THIS TIME
THE RIVERS MOST LIKELY TO FLOOD ARE THE ONES FLOWING OFF THE
CASCADES OF KING...PIERCE...AND LEWIS COUNTIES...AS WELL AS THE
UNUSUALLY FLOOD-PRONE SKOKOMISH RIVER IN MASON COUNTY. ANY FLOODING
WOULD LIKELY BEGIN AS EARLY AS SATURDAY NIGHT ON THE SKOKOMISH
RIVER. THE CASCADE RIVERS COULD FLOOD SUNDAY WITH CRESTS SUNDAY
NIGHT OR MONDAY.

A COOLER AND DRIER AIR MASS IS FORECAST TO BE OVER THE AREA NEXT
WEEK. AFTER MONDAY THE RIVERS WILL RECEDE AND ANY FURTHER FLOODING
IS UNLIKELY. BURKE

&&

.AVIATION...A FRONT OVER WESTERN WA THIS EVENING WILL MOVE INLAND
OVERNIGHT. A STRONGER FRONT WILL REACH THE AREA FRIDAY NIGHT AND
SATURDAY MORNING. RAIN TONIGHT WILL CHANGE TO SHOWERS...AND THEN
BACK TO RAIN FRIDAY NIGHT. THE AIR WILL BE MOIST...THEN SOME
SUNBREAKS FRIDAY...THEN INCREASING MOISTURE AGAIN FRIDAY NIGHT. SW
FLOW ALOFT.

KSEA...RAIN TURNING TO SHOWERS...SOME SUNBREAKS POSSIBLE
FRIDAY...THEN BACK TO RAIN FRIDAY NIGHT. SOUTHERLY BREEZE.

&&

.MARINE...A FRONT OVER WESTERN WA THIS EVENING WILL MOVE INLAND
OVERNIGHT. A STRONGER FRONT WILL REACH THE AREA FRIDAY NIGHT AND
SATURDAY MORNING. THE WIND HAS FALLEN OFF OVER THE COASTAL WATERS
THIS EVENING BEHIND THE FRONT...BUT THERE IS STILL A GALE WARNING UP
FOR THE EAST ENTRANCE WHERE SMITH ISLAND STILL HAD 30-40KT SE WINDS
AT 8PM. THE SWELL WILL RISE THROUGH FRIDAY NIGHT...PEAKING AROUND 22
FT.

&&

.SEW WATCHES/WARNINGS/ADVISORIES...

WA...WIND ADVISORY THROUGH TONIGHT FOR THE SAN JUAN ISLANDS...
     WESTERN WHATCOM COUNTY...AND THE ADMIRALTY INLET AREA.
     WINTER WEATHER ADVISORY THROUGH TONIGHT FOR THE OLYMPICS.
     WINTER WEATHER ADVISORY FOR THE WEST SLOPES OF THE CASCADES
     4 PM PST THIS AFTERNOON THROUGH TONIGHT.
     HIGH SURF ADVISORY FOR THE NORTH AND CENTRAL COAST FROM LATE
     FRIDAY MORNING THROUGH EARLY SATURDAY MORNING.
     COASTAL FLOOD WATCH FOR THE NORTH AND CENTRAL COAST FROM
     SATURDAY MORNING THROUGH SATURDAY AFTERNOON.

PZ...GALE WARNING EAST ENTRANCE STRAIT.
     SMALL CRAFT ADVISORY ALL REMAINING WATERS.
     SMALL CRAFT ADVISORY FOR ROUGH/SEVERE GRAYS HARBOR BAR
       CONDITIONS.
     GALE WATCH COAST...ENTRANCES TO THE STRAIT OF JUAN DE FUCA...
     ADMIRALTY INLET...AND NORTHERN INLAND WATERS FRIDAY NIGHT
     THROUGH SATURDAY.

&&

$$

YOU CAN SEE AN ILLUSTRATED VERSION OF THIS FORECAST DISCUSSION AT
WWW.WEATHER.GOV/SEATTLE/GAFD/LATEST_WEBAFD.HTML







000
FXUS66 KSEW 190437
AFDSEW

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SEATTLE WA
900 PM PST THU DEC 18 2014

.SYNOPSIS...A FRONT WILL BRING RAINY AND LOCALLY WINDY WEATHER TO
WESTERN WASHINGTON TONIGHT...FOLLOWED BY AN UPPER TROUGH AND
SCATTERED SHOWERS FRIDAY. A FRONTAL SYSTEM WILL MOVE THROUGH
SATURDAY...FOLLOWED BY MOIST WESTERLY FLOW ON SUNDAY. PRECIPITATION
WILL BE ESPECIALLY HEAVY IN THE MOUNTAINS. THE WEATHER WILL BE
SOMEWHAT DRIER EARLY NEXT WEEK WITH AN UPPER RIDGE OVER THE AREA.

&&

.SHORT TERM...A VIGOROUS FRONTAL SYSTEM IS MOVING INTO THE PACIFIC
NORTHWEST THIS EVENING...WITH RAIN FALLING ACROSS MOST OF WESTERN
WASHINGTON. SOUTHEAST WINDS ARE GUSTING INTO THE 25 TO 35 MPH RANGE
ALONG THE COAST AND IN THE NORTH INTERIOR.

THE SURFACE FRONT MADE LANDFALL ON THE NORTH WASHINGTON COAST JUST
AFTER 7 PM...AND IT SHOULD MOVE THROUGH THE WESTERN WASHINGTON
INTERIOR LATE THIS EVENING OR AROUND MIDNIGHT. LIGHT TO MODERATE
PRECIPITATION AND LOCALLY WINDY CONDITIONS WILL CONTINUE THROUGH THE
FRONTAL PASSAGE. WINDS WILL EASE AND PRECIPITATION WILL DECREASE
OVERNIGHT. THE SNOW LEVEL WILL BE IN THE 4000 TO 5000 FT RANGE AS
THIS SYSTEM MOVES THROUGH...ALTHOUGH EASTERLY WINDS IN THE PASSES
COULD KEEP THE SNOW LEVEL LOCALLY LOWER. SEVERAL INCHES MORE
SNOWFALL CAN BE EXPECTED OVERNIGHT.

THE POST-FRONTAL UPPER TROUGH WILL MOVE THROUGH THE AREA FRIDAY...
AND IT SHOULD BE A SHOWERY DAY IN THE COOLER AND WEAKLY UNSTABLE AIR
MASS. THE SNOW LEVEL WILL BE 3000 TO 4000 FT WITH UP TO 4 INCHES OF
ADDITIONAL SNOW IN THE MOUNTAINS.

ANOTHER MORE VIGOROUS FRONTAL SYSTEM WILL SPREAD PRECIPITATION INTO
WESTERN WASHINGTON FRIDAY NIGHT...WITH THE CORE OF THE SYSTEM MOVING
THROUGH SATURDAY AND SATURDAY NIGHT. THIS SYSTEM WILL BRING SOMEWHAT
WINDIER CONDITIONS TO MAINLY THE COAST AND NORTH INTERIOR...WHERE A
HIGH-END WIND ADVISORY EVENT IS LIKELY -- MEANING SUSTAINED WINDS UP
TO 35 MPH AND GUSTS UP TO 55 MPH. THE SNOW LEVEL WILL BE 2500 TO
3500 FT AS PRECIPITATION BEGINS...BUT IT WILL RISE QUICKLY TO 5500
TO 7000 FT SATURDAY NIGHT. PRECIPITATION AMOUNTS WITH THIS SYSTEM
WILL BE SIGNIFICANT...AS DISCUSSED IN MORE DETAIL IN THE HYDROLOGY
SECTION BELOW.

MOIST WESTERLY FLOW WILL FOLLOW THE SYSTEM ON SUNDAY WITH AREAS OF
MODERATE TO HEAVY PRECIPITATION CONTINUING...ESPECIALLY IN THE
MOUNTAINS.   MCDONNAL

.LONG TERM...HERE IS THE LONG TERM SECTION FROM THE AFTERNOON
FORECAST DISCUSSION -- THE EXTENDED FORECAST REMAINS CHALLENGING
WITH A WIDE RANGE OF SOLUTIONS AMONG THE MODELS. THERE IS SOME
AGREEMENT THAT MONDAY WILL GENERALLY FEATURE SHOWERS OR A LULL IN
RAINFALL AS HIGHER PRESSURE BUILDS ALOFT. MODELS DO NOT AGREE ON THE
STRENGTH OR TRACK OF THE NEXT SYSTEM APPROACHING FROM THE W ON
TUESDAY. THE LATEST 12/18Z GFS BRINGS THE LOW IN FURTHER N WHICH
WOULD STILL PRODUCE WARM ADVECTION RAINFALL ACROSS THE AREA...THOUGH
NOT AS MUCH AS WAS SHOWN BY PREVIOUS SOLUTIONS.

MOST MODELS DIG A COLD UPPER TROUGH SWD OUT OF B.C. THROUGH WRN WA
ON WEDNESDAY. THIS COULD USHER IN COOLER AIR BUT MODELS DISAGREE ON
THE EXTENT OF RIDGING OFFSHORE AND WHERE IT SETS UP. THE ECMWF
CONTINUES TO BE ONE OF THE COLDER SOLUTIONS AND HAS THE KONA LOW CUT
OFF FURTHER W...THUS A FURTHER W DEVELOPMENT OF THE UPPER RIDGE. THE
KONA LOW IS FURTHER E ON THE GFS40 WITH A RIDGE NEAR 135-140 WHICH
WILL STILL USHER IN COOLER NLY FLOW BUT PERHAPS LESS CHANCE OF
PRECIPITATION. IT WILL BE INTERESTING TO SEE HOW THIS PANS OUT BUT A
SWITCH TO COOLER OR COLD TEMPERATURES IS A POSSIBILITY BY THURSDAY.
POPS WERE TRIMMED WAY BACK AND MAY NEED TO BE REMOVED ALTOGETHER IF
MODEL TRENDS CONTINUE. SNOW LEVELS WILL ALSO BE MUCH
LOWER...POSSIBLY TO SEA LEVEL...BUT IT IS VERY UNCLEAR AS TO HOW
MUCH MOISTURE WILL REMAIN BY THAT TIME.

&&

.HYDROLOGY...THOUGH RAIN WILL FALL AT TIMES...FLOODING IS UNLIKELY
ON ANY RIVER THROUGH SATURDAY.

HEAVY RAIN COULD CAUSE FLOODING BY LATE THIS WEEKEND. A WEATHER
SYSTEM WITH STRONG WESTERLY FLOW ALOFT WILL BRING HEAVY RAIN AT
TIMES TO THE COAST AND OLYMPICS ON SATURDAY. HEAVY RAIN WILL SPREAD
INTO THE CASCADES SATURDAY AFTERNOON.

MODELS CURRENTLY TAPER RAIN OVER THE OLYMPICS ON SUNDAY BUT KEEP
HEAVY RAIN GOING IN THE CASCADES...ESPECIALLY OVER THE CASCADES FROM
ABOUT KING COUNTY SOUTH. THE TOTAL MODEL RAINFALL OVER ABOUT 48
HOURS FROM SATURDAY MORNING THROUGH SUNDAY NIGHT AMOUNTS TO AROUND
FOUR TO SIX INCHES OVER THE OLYMPICS AND CENTRAL CASCADES WITH A
TEN-INCH BULLSEYE OVER MOUNT RAINIER. THE SNOW LEVEL WILL BE ABOVE
5000 FEET ON SATURDAY AND SUNDAY BEFORE FALLING TO 3500 FEET OR SO
SUNDAY NIGHT.

THESE RAINFALL AMOUNTS ARE ENOUGH TO CAUSE FLOODING. AT THIS TIME
THE RIVERS MOST LIKELY TO FLOOD ARE THE ONES FLOWING OFF THE
CASCADES OF KING...PIERCE...AND LEWIS COUNTIES...AS WELL AS THE
UNUSUALLY FLOOD-PRONE SKOKOMISH RIVER IN MASON COUNTY. ANY FLOODING
WOULD LIKELY BEGIN AS EARLY AS SATURDAY NIGHT ON THE SKOKOMISH
RIVER. THE CASCADE RIVERS COULD FLOOD SUNDAY WITH CRESTS SUNDAY
NIGHT OR MONDAY.

A COOLER AND DRIER AIR MASS IS FORECAST TO BE OVER THE AREA NEXT
WEEK. AFTER MONDAY THE RIVERS WILL RECEDE AND ANY FURTHER FLOODING
IS UNLIKELY. BURKE

&&

.AVIATION...A FRONT OVER WESTERN WA THIS EVENING WILL MOVE INLAND
OVERNIGHT. A STRONGER FRONT WILL REACH THE AREA FRIDAY NIGHT AND
SATURDAY MORNING. RAIN TONIGHT WILL CHANGE TO SHOWERS...AND THEN
BACK TO RAIN FRIDAY NIGHT. THE AIR WILL BE MOIST...THEN SOME
SUNBREAKS FRIDAY...THEN INCREASING MOISTURE AGAIN FRIDAY NIGHT. SW
FLOW ALOFT.

KSEA...RAIN TURNING TO SHOWERS...SOME SUNBREAKS POSSIBLE
FRIDAY...THEN BACK TO RAIN FRIDAY NIGHT. SOUTHERLY BREEZE.

&&

.MARINE...A FRONT OVER WESTERN WA THIS EVENING WILL MOVE INLAND
OVERNIGHT. A STRONGER FRONT WILL REACH THE AREA FRIDAY NIGHT AND
SATURDAY MORNING. THE WIND HAS FALLEN OFF OVER THE COASTAL WATERS
THIS EVENING BEHIND THE FRONT...BUT THERE IS STILL A GALE WARNING UP
FOR THE EAST ENTRANCE WHERE SMITH ISLAND STILL HAD 30-40KT SE WINDS
AT 8PM. THE SWELL WILL RISE THROUGH FRIDAY NIGHT...PEAKING AROUND 22
FT.

&&

.SEW WATCHES/WARNINGS/ADVISORIES...

WA...WIND ADVISORY THROUGH TONIGHT FOR THE SAN JUAN ISLANDS...
     WESTERN WHATCOM COUNTY...AND THE ADMIRALTY INLET AREA.
     WINTER WEATHER ADVISORY THROUGH TONIGHT FOR THE OLYMPICS.
     WINTER WEATHER ADVISORY FOR THE WEST SLOPES OF THE CASCADES
     4 PM PST THIS AFTERNOON THROUGH TONIGHT.
     HIGH SURF ADVISORY FOR THE NORTH AND CENTRAL COAST FROM LATE
     FRIDAY MORNING THROUGH EARLY SATURDAY MORNING.
     COASTAL FLOOD WATCH FOR THE NORTH AND CENTRAL COAST FROM
     SATURDAY MORNING THROUGH SATURDAY AFTERNOON.

PZ...GALE WARNING THROUGH TONIGHT COASTAL WATERS AND EAST
     ENTRANCE.
     SMALL CRAFT ADVISORY ALL REMAINING WATERS.
     SMALL CRAFT ADVISORY FOR ROUGH GRAYS HARBOR BAR TONIGHT THROUGH
     FRIDAY.
     GALE WATCH COAST...ENTRANCES TO THE STRAIT OF JUAN DE FUCA...
     ADMIRALTY INLET...AND NORTHERN INLAND WATERS FRIDAY NIGHT
     THROUGH SATURDAY.

&&

$$

YOU CAN SEE AN ILLUSTRATED VERSION OF THIS FORECAST DISCUSSION AT
WWW.WEATHER.GOV/SEATTLE/GAFD/LATEST_WEBAFD.HTML







000
FXUS66 KSEW 190437
AFDSEW

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SEATTLE WA
900 PM PST THU DEC 18 2014

.SYNOPSIS...A FRONT WILL BRING RAINY AND LOCALLY WINDY WEATHER TO
WESTERN WASHINGTON TONIGHT...FOLLOWED BY AN UPPER TROUGH AND
SCATTERED SHOWERS FRIDAY. A FRONTAL SYSTEM WILL MOVE THROUGH
SATURDAY...FOLLOWED BY MOIST WESTERLY FLOW ON SUNDAY. PRECIPITATION
WILL BE ESPECIALLY HEAVY IN THE MOUNTAINS. THE WEATHER WILL BE
SOMEWHAT DRIER EARLY NEXT WEEK WITH AN UPPER RIDGE OVER THE AREA.

&&

.SHORT TERM...A VIGOROUS FRONTAL SYSTEM IS MOVING INTO THE PACIFIC
NORTHWEST THIS EVENING...WITH RAIN FALLING ACROSS MOST OF WESTERN
WASHINGTON. SOUTHEAST WINDS ARE GUSTING INTO THE 25 TO 35 MPH RANGE
ALONG THE COAST AND IN THE NORTH INTERIOR.

THE SURFACE FRONT MADE LANDFALL ON THE NORTH WASHINGTON COAST JUST
AFTER 7 PM...AND IT SHOULD MOVE THROUGH THE WESTERN WASHINGTON
INTERIOR LATE THIS EVENING OR AROUND MIDNIGHT. LIGHT TO MODERATE
PRECIPITATION AND LOCALLY WINDY CONDITIONS WILL CONTINUE THROUGH THE
FRONTAL PASSAGE. WINDS WILL EASE AND PRECIPITATION WILL DECREASE
OVERNIGHT. THE SNOW LEVEL WILL BE IN THE 4000 TO 5000 FT RANGE AS
THIS SYSTEM MOVES THROUGH...ALTHOUGH EASTERLY WINDS IN THE PASSES
COULD KEEP THE SNOW LEVEL LOCALLY LOWER. SEVERAL INCHES MORE
SNOWFALL CAN BE EXPECTED OVERNIGHT.

THE POST-FRONTAL UPPER TROUGH WILL MOVE THROUGH THE AREA FRIDAY...
AND IT SHOULD BE A SHOWERY DAY IN THE COOLER AND WEAKLY UNSTABLE AIR
MASS. THE SNOW LEVEL WILL BE 3000 TO 4000 FT WITH UP TO 4 INCHES OF
ADDITIONAL SNOW IN THE MOUNTAINS.

ANOTHER MORE VIGOROUS FRONTAL SYSTEM WILL SPREAD PRECIPITATION INTO
WESTERN WASHINGTON FRIDAY NIGHT...WITH THE CORE OF THE SYSTEM MOVING
THROUGH SATURDAY AND SATURDAY NIGHT. THIS SYSTEM WILL BRING SOMEWHAT
WINDIER CONDITIONS TO MAINLY THE COAST AND NORTH INTERIOR...WHERE A
HIGH-END WIND ADVISORY EVENT IS LIKELY -- MEANING SUSTAINED WINDS UP
TO 35 MPH AND GUSTS UP TO 55 MPH. THE SNOW LEVEL WILL BE 2500 TO
3500 FT AS PRECIPITATION BEGINS...BUT IT WILL RISE QUICKLY TO 5500
TO 7000 FT SATURDAY NIGHT. PRECIPITATION AMOUNTS WITH THIS SYSTEM
WILL BE SIGNIFICANT...AS DISCUSSED IN MORE DETAIL IN THE HYDROLOGY
SECTION BELOW.

MOIST WESTERLY FLOW WILL FOLLOW THE SYSTEM ON SUNDAY WITH AREAS OF
MODERATE TO HEAVY PRECIPITATION CONTINUING...ESPECIALLY IN THE
MOUNTAINS.   MCDONNAL

.LONG TERM...HERE IS THE LONG TERM SECTION FROM THE AFTERNOON
FORECAST DISCUSSION -- THE EXTENDED FORECAST REMAINS CHALLENGING
WITH A WIDE RANGE OF SOLUTIONS AMONG THE MODELS. THERE IS SOME
AGREEMENT THAT MONDAY WILL GENERALLY FEATURE SHOWERS OR A LULL IN
RAINFALL AS HIGHER PRESSURE BUILDS ALOFT. MODELS DO NOT AGREE ON THE
STRENGTH OR TRACK OF THE NEXT SYSTEM APPROACHING FROM THE W ON
TUESDAY. THE LATEST 12/18Z GFS BRINGS THE LOW IN FURTHER N WHICH
WOULD STILL PRODUCE WARM ADVECTION RAINFALL ACROSS THE AREA...THOUGH
NOT AS MUCH AS WAS SHOWN BY PREVIOUS SOLUTIONS.

MOST MODELS DIG A COLD UPPER TROUGH SWD OUT OF B.C. THROUGH WRN WA
ON WEDNESDAY. THIS COULD USHER IN COOLER AIR BUT MODELS DISAGREE ON
THE EXTENT OF RIDGING OFFSHORE AND WHERE IT SETS UP. THE ECMWF
CONTINUES TO BE ONE OF THE COLDER SOLUTIONS AND HAS THE KONA LOW CUT
OFF FURTHER W...THUS A FURTHER W DEVELOPMENT OF THE UPPER RIDGE. THE
KONA LOW IS FURTHER E ON THE GFS40 WITH A RIDGE NEAR 135-140 WHICH
WILL STILL USHER IN COOLER NLY FLOW BUT PERHAPS LESS CHANCE OF
PRECIPITATION. IT WILL BE INTERESTING TO SEE HOW THIS PANS OUT BUT A
SWITCH TO COOLER OR COLD TEMPERATURES IS A POSSIBILITY BY THURSDAY.
POPS WERE TRIMMED WAY BACK AND MAY NEED TO BE REMOVED ALTOGETHER IF
MODEL TRENDS CONTINUE. SNOW LEVELS WILL ALSO BE MUCH
LOWER...POSSIBLY TO SEA LEVEL...BUT IT IS VERY UNCLEAR AS TO HOW
MUCH MOISTURE WILL REMAIN BY THAT TIME.

&&

.HYDROLOGY...THOUGH RAIN WILL FALL AT TIMES...FLOODING IS UNLIKELY
ON ANY RIVER THROUGH SATURDAY.

HEAVY RAIN COULD CAUSE FLOODING BY LATE THIS WEEKEND. A WEATHER
SYSTEM WITH STRONG WESTERLY FLOW ALOFT WILL BRING HEAVY RAIN AT
TIMES TO THE COAST AND OLYMPICS ON SATURDAY. HEAVY RAIN WILL SPREAD
INTO THE CASCADES SATURDAY AFTERNOON.

MODELS CURRENTLY TAPER RAIN OVER THE OLYMPICS ON SUNDAY BUT KEEP
HEAVY RAIN GOING IN THE CASCADES...ESPECIALLY OVER THE CASCADES FROM
ABOUT KING COUNTY SOUTH. THE TOTAL MODEL RAINFALL OVER ABOUT 48
HOURS FROM SATURDAY MORNING THROUGH SUNDAY NIGHT AMOUNTS TO AROUND
FOUR TO SIX INCHES OVER THE OLYMPICS AND CENTRAL CASCADES WITH A
TEN-INCH BULLSEYE OVER MOUNT RAINIER. THE SNOW LEVEL WILL BE ABOVE
5000 FEET ON SATURDAY AND SUNDAY BEFORE FALLING TO 3500 FEET OR SO
SUNDAY NIGHT.

THESE RAINFALL AMOUNTS ARE ENOUGH TO CAUSE FLOODING. AT THIS TIME
THE RIVERS MOST LIKELY TO FLOOD ARE THE ONES FLOWING OFF THE
CASCADES OF KING...PIERCE...AND LEWIS COUNTIES...AS WELL AS THE
UNUSUALLY FLOOD-PRONE SKOKOMISH RIVER IN MASON COUNTY. ANY FLOODING
WOULD LIKELY BEGIN AS EARLY AS SATURDAY NIGHT ON THE SKOKOMISH
RIVER. THE CASCADE RIVERS COULD FLOOD SUNDAY WITH CRESTS SUNDAY
NIGHT OR MONDAY.

A COOLER AND DRIER AIR MASS IS FORECAST TO BE OVER THE AREA NEXT
WEEK. AFTER MONDAY THE RIVERS WILL RECEDE AND ANY FURTHER FLOODING
IS UNLIKELY. BURKE

&&

.AVIATION...A FRONT OVER WESTERN WA THIS EVENING WILL MOVE INLAND
OVERNIGHT. A STRONGER FRONT WILL REACH THE AREA FRIDAY NIGHT AND
SATURDAY MORNING. RAIN TONIGHT WILL CHANGE TO SHOWERS...AND THEN
BACK TO RAIN FRIDAY NIGHT. THE AIR WILL BE MOIST...THEN SOME
SUNBREAKS FRIDAY...THEN INCREASING MOISTURE AGAIN FRIDAY NIGHT. SW
FLOW ALOFT.

KSEA...RAIN TURNING TO SHOWERS...SOME SUNBREAKS POSSIBLE
FRIDAY...THEN BACK TO RAIN FRIDAY NIGHT. SOUTHERLY BREEZE.

&&

.MARINE...A FRONT OVER WESTERN WA THIS EVENING WILL MOVE INLAND
OVERNIGHT. A STRONGER FRONT WILL REACH THE AREA FRIDAY NIGHT AND
SATURDAY MORNING. THE WIND HAS FALLEN OFF OVER THE COASTAL WATERS
THIS EVENING BEHIND THE FRONT...BUT THERE IS STILL A GALE WARNING UP
FOR THE EAST ENTRANCE WHERE SMITH ISLAND STILL HAD 30-40KT SE WINDS
AT 8PM. THE SWELL WILL RISE THROUGH FRIDAY NIGHT...PEAKING AROUND 22
FT.

&&

.SEW WATCHES/WARNINGS/ADVISORIES...

WA...WIND ADVISORY THROUGH TONIGHT FOR THE SAN JUAN ISLANDS...
     WESTERN WHATCOM COUNTY...AND THE ADMIRALTY INLET AREA.
     WINTER WEATHER ADVISORY THROUGH TONIGHT FOR THE OLYMPICS.
     WINTER WEATHER ADVISORY FOR THE WEST SLOPES OF THE CASCADES
     4 PM PST THIS AFTERNOON THROUGH TONIGHT.
     HIGH SURF ADVISORY FOR THE NORTH AND CENTRAL COAST FROM LATE
     FRIDAY MORNING THROUGH EARLY SATURDAY MORNING.
     COASTAL FLOOD WATCH FOR THE NORTH AND CENTRAL COAST FROM
     SATURDAY MORNING THROUGH SATURDAY AFTERNOON.

PZ...GALE WARNING THROUGH TONIGHT COASTAL WATERS AND EAST
     ENTRANCE.
     SMALL CRAFT ADVISORY ALL REMAINING WATERS.
     SMALL CRAFT ADVISORY FOR ROUGH GRAYS HARBOR BAR TONIGHT THROUGH
     FRIDAY.
     GALE WATCH COAST...ENTRANCES TO THE STRAIT OF JUAN DE FUCA...
     ADMIRALTY INLET...AND NORTHERN INLAND WATERS FRIDAY NIGHT
     THROUGH SATURDAY.

&&

$$

YOU CAN SEE AN ILLUSTRATED VERSION OF THIS FORECAST DISCUSSION AT
WWW.WEATHER.GOV/SEATTLE/GAFD/LATEST_WEBAFD.HTML






000
FXUS66 KSEW 182254 AAA
AFDSEW

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SEATTLE WA
300 PM PST THU DEC 18 2014

.SYNOPSIS...A FRONT WILL BRING RAIN AND LOCALLY WINDY CONDITIONS TO
WESTERN WASHINGTON THROUGH TONIGHT. AN UPPER LEVEL TROUGH WILL BRING
SCATTERED SHOWERS ON FRIDAY. STRONG MOIST WEST FLOW ALOFT OVER THE
NORTHEAST PACIFIC WILL BRING WIND AND RAIN INTO WESTERN WASHINGTON
THIS WEEKEND. A BROAD UPPER LEVEL RIDGE WILL REMAIN OVER THE REGION
EARLY NEXT WEEK FOR NOT QUITE AS WET WEATHER. COOLER TEMPERATURES
ARE POSSIBLE BY MID WEEK.

&&

.SHORT TERM...WARM ADVECTION RAIN IS FILLING IN ACROSS WRN WA THIS
AFTERNOON. VISIBLE SATELLITE IMAGERY IMPLIES THE SURFACE FRONT IS
NOW JUST INSIDE 130 W HEADING TOWARD WRN WA. IR/WV IMAGERY SHOWS A
WAVE FORMING ON THE SRN EXTENT OF THE FRONTAL BAND AS IT BEGINS TO
SPLIT. THIS WILL SLOW THE PROGRESS OF THE SYSTEM EWD BUT ALSO RESULT
IN WEAKER FLOW ALOFT SO OROGRAPHICS WILL NOT PLAY AS BIG A ROLE AS
USUAL. MODELS STILL SHOW 12 HOUR QPF TOTALS RANGING FROM ROUGHLY ONE
HALF TO ONE INCH LIQUID WITH LOCALLY HIGHER AMOUNTS. PLACES WHERE
THIS FALLS AS ALL SNOW COULD SEE UP TO 1 FOOT. SOME OF THE HIGHER
SKI RESORTS AND S/SW FACING SLOPES ARE MOST LIKELY TO SEE THESE TYPE
OF SNOW TOTALS. THE SNOW LEVEL IS DIFFICULT TO PINPOINT WITH THIS
SYSTEM WITH SOME FLUCTUATION LIKELY BETWEEN 3500 AND 5000 FEET.
TEMPERATURES IN MOST PASSES ARE STILL IN THE UPPER 20S TO AROUND 30
DEGREES...SO PRECIPITATION WILL LIKELY START AS SNOW EVEN AT
SNOQUALMIE PASS. A COUPLE INCHES MAY FALL...THEN SNOW LEVELS SHOULD
GENERALLY START TO RISE AS WARMER AIR STARTS TO WORK INLAND. THE
MAIN SNOW LEVEL SHOULD HOVER AROUND 4500 TO 5000 FEET TONIGHT WHICH
PUTS STEVENS PASS ON THE EDGE. UP TO 6 INCHES STILL SEEMS POSSIBLE
DEPENDING ON HOW MUCH RAIN MIXES IN. SNOW LEVELS WILL FALL BACK DOWN
TO AROUND 3000 FEET BEHIND THE FRONT BUT ONLY MINOR ADDITIONAL
ACCUMULATIONS EXPECTED FRIDAY MORNING.

SE PRESSURE GRADIENTS WILL CONTINUE TO TIGHTEN THIS EVENING. SE
WINDS IN THE ADMIRALTY INLET AREA AND SAN JUANS ARE CURRENTLY
GUSTING INTO THE LOW 30 MPH RANGE AND SHOULD PICK UP CONSIDERABLY
THIS EVENING. THE WIND ADVISORY WILL REMAIN IN PLACE FOR GUSTS TO 45
MPH ACROSS THE N INTERIOR...EXCLUDING WRN SKAGIT COUNTY. STRONGEST
WINDS WILL BE ALONG THE WATER AND AT PLACES EXPOSED TO SE WINDS. THE
WIND ADVISORY RUNS THROUGH MIDNIGHT TONIGHT.

IT WILL BE COOL AND SHOWERY ON FRIDAY AS THE FRONT MOVES E AND AN
UPPER TROUGH REACHES THE AREA. COLD TOPPED CU OFFSHORE INDICATES
UNSTABLE CONDITIONS BEHIND THE TROUGH. MODEL LI`S ARE NEGATIVE OVER
THE COASTAL WATERS BUT NOT OVER THE LAND AREAS. BUFFER FORECAST
SOUNDINGS SHOW THE UNSTABLE LAYER CAPPED AT 700 MB SO THUNDERSTORMS
WOULD SEEM UNLIKELY.

STRONG AND MOIST WLY FLOW DRIVEN BY A STRONG 180+ KT JET WILL STEER
A WARM FRONT INTO WRN WA ON SATURDAY. TIMING IS A LITTLE FASTER WITH
MOST MODELS DEVELOPING WIDESPREAD RAIN ACROSS WRN WA BY LATE FRIDAY
NIGHT OR EARLY SATURDAY MORNING. INITIALLY THE FLOW WILL BE OUT OF
THE S/SW AND STRONG AT 40 TO 50 KT. THIS WILL PRODUCE HEFTY
OROGRAPHICALLY ENHANCED RAINFALL AMOUNTS ALONG S/SW FACING SLOPES OF
THE OLYMPICS AND CASCADES. THIS WILL ALMOST CERTAINLY CAUSE FLOODING
ON THE SKOKOMISH RIVER BY LATER SATURDAY NIGHT. THE FLOW TURNS MORE
WLY SATURDAY NIGHT AND SUNDAY WHICH IS A FAVORABLE DIRECTION FOR
HEAVY RAIN IN MORE BASINS ACROSS THE W SLOPES OF THE CASCADES. THIS
WILL CAUSE ADDITIONAL FLOOD CONCERNS. REFER TO THE EXTENDED FLOOD
OUTLOOK STATEMENT AND HYDRO DISCUSSION BELOW FOR FURTHER DETAILS.

THIS NEXT SYSTEM WILL ALSO HAVE STRONGER SE PRESSURE GRADIENTS AND
STRONGER FLOW ALOFT AHEAD OF THE COLD FRONT ON SATURDAY. MESO MODELS
ARE SHOWING HIGH END ADVISORY LEVEL TYPE WINDS BUT HIGH WIND IN A
COUPLE SPOTS CANNOT BE RULED OUT EITHER. THIS IS STILL A COUPLE DAYS
OUT AND WILL OPT TO MAINTAIN A HIGH END ADVISORY WIND FORECAST FOR
THE COAST/N INTERIOR. PUGET SOUND WILL ALSO BECOME
BREEZY...ESPECIALLY AS GRADIENTS BECOME MORE SLY SATURDAY NIGHT AND
SUNDAY. BUT FORECAST GRADIENTS DO NOT SEEM TO SUPPORT EVEN ADVISORY
LEVEL WINDS FOR PUGET SOUND AT THIS TIME.

THE BAROCLINIC BOUNDARY WILL START TO DRIFT SWD SUNDAY AFTERNOON
DIRECTING THE HEAVIEST PRECIPITATION INTO THE WA CASCADES FROM
ABOUT KING COUNTY SWD INTO THE N/CENTRAL OREGON CASCADES. THIS WILL
HELP MITIGATE FLOODING CONCERNS ACROSS THE FAR N ALTHOUGH DETAILS ON
WHERE THIS BOUNDARY SETS UP REMAINS UNCERTAIN. THERE DOES SEEM TO BE
PRETTY GOOD CONSENSUS EVOLVING AMONG THE MODELS THAT THE HEAVY
MOUNTAIN RAIN WILL TAPER OFF FROM N TO S ON SUNDAY AND MOSTLY SHUT
OFF BY SUNDAY NIGHT AS THE RIDGE BEGINS TO BUILD.

.LONG TERM...THE EXTENDED FORECAST REMAINS CHALLENGING WITH A WIDE
RANGE OF SOLUTIONS AMONG THE MODELS. THERE IS SOME AGREEMENT THAT
MONDAY WILL GENERALLY FEATURE SHOWERS OR A LULL IN RAINFALL AS
HIGHER PRESSURE BUILDS ALOFT. MODELS DO NOT AGREE ON THE STRENGTH OR
TRACK OF THE NEXT SYSTEM APPROACHING FROM THE W ON TUESDAY. THE
LATEST 12/18Z GFS BRINGS THE LOW IN FURTHER N WHICH WOULD STILL
PRODUCE WARM ADVECTION RAINFALL ACROSS THE AREA...THOUGH NOT AS MUCH
AS WAS SHOWN BY PREVIOUS SOLUTIONS.

MOST MODELS DIG A COLD UPPER TROUGH SWD OUT OF B.C. THROUGH WRN WA
ON WEDNESDAY. THIS COULD USHER IN COOLER AIR BUT MODELS DISAGREE ON
THE EXTENT OF RIDGING OFFSHORE AND WHERE IT SETS UP. THE ECMWF
CONTINUES TO BE ONE OF THE COLDER SOLUTIONS AND HAS THE KONA LOW CUT
OFF FURTHER W...THUS A FURTHER W DEVELOPMENT OF THE UPPER RIDGE. THE
KONA LOW IS FURTHER E ON THE GFS40 WITH A RIDGE NEAR 135-140 WHICH
WILL STILL USHER IN COOLER NLY FLOW BUT PERHAPS LESS CHANCE OF
PRECIPITATION. IT WILL BE INTERESTING TO SEE HOW THIS PANS OUT BUT A
SWITCH TO COOLER OR COLD TEMPERATURES IS A POSSIBILITY BY THURSDAY.
POPS WERE TRIMMED WAY BACK AND MAY NEED TO BE REMOVED ALTOGETHER IF
MODEL TRENDS CONTINUE. SNOW LEVELS WILL ALSO BE MUCH
LOWER...POSSIBLY TO SEA LEVEL...BUT IT IS VERY UNCLEAR AS TO HOW
MUCH MOISTURE WILL REMAIN BY THAT TIME.

&&

.HYDROLOGY...THOUGH RAIN WILL FALL AT TIMES...FLOODING IS UNLIKELY
ON ANY RIVER THROUGH SATURDAY.

HEAVY RAIN COULD CAUSE FLOODING BY LATE THIS WEEKEND. A WEATHER
SYSTEM WITH STRONG WESTERLY FLOW ALOFT WILL BRING HEAVY RAIN AT
TIMES TO THE COAST AND OLYMPICS ON SATURDAY. HEAVY RAIN WILL SPREAD
INTO THE CASCADES SATURDAY AFTERNOON.

MODELS CURRENTLY TAPER RAIN OVER THE OLYMPICS ON SUNDAY BUT KEEP
HEAVY RAIN GOING IN THE CASCADES...ESPECIALLY OVER THE CASCADES FROM
ABOUT KING COUNTY SOUTH. THE TOTAL MODEL RAINFALL OVER ABOUT 48
HOURS FROM SATURDAY MORNING THROUGH SUNDAY NIGHT AMOUNTS TO AROUND
FOUR TO SIX INCHES OVER THE OLYMPICS AND CENTRAL CASCADES WITH A
TEN-INCH BULLSEYE OVER MOUNT RAINIER. THE SNOW LEVEL WILL BE ABOVE
5000 FEET ON SATURDAY AND SUNDAY BEFORE FALLING TO 3500 FEET OR SO
SUNDAY NIGHT.

THESE RAINFALL AMOUNTS ARE ENOUGH TO CAUSE FLOODING. AT THIS TIME
THE RIVERS MOST LIKELY TO FLOOD ARE THE ONES FLOWING OFF THE
CASCADES OF KING...PIERCE...AND LEWIS COUNTIES...AS WELL AS THE
UNUSUALLY FLOOD-PRONE SKOKOMISH RIVER IN MASON COUNTY. ANY FLOODING
WOULD LIKELY BEGIN AS EARLY AS SATURDAY NIGHT ON THE SKOKOMISH
RIVER. THE CASCADE RIVERS COULD FLOOD SUNDAY WITH CRESTS SUNDAY
NIGHT OR MONDAY.

A COOLER AND DRIER AIR MASS IS FORECAST TO BE OVER THE AREA NEXT
WEEK. AFTER MONDAY THE RIVERS WILL RECEDE AND ANY FURTHER FLOODING
IS UNLIKELY. BURKE

&&

.AVIATION...A STRONG PACIFIC FRONTAL SYSTEM OVER THE OFFSHORE WATERS
WILL MOVE ACROSS THE AREA TONIGHT. SOUTHWESTERLY FLOW ALOFT WILL
INCREASE AND BECOMING STRONG THIS EVENING THEN BECOMING MODERATE ON
FRIDAY. THE AIR MASS IS MOIST AND STABLE...IT WILL BECOME SOMEWHAT
UNSTABLE LATE TONIGHT AND FRIDAY BEHIND THE FRONT.

AT 2230Z A STRONG FRONT WAS MOVING THROUGH THE OFFSHORE WATERS. IT
WILL PUSH ACROSS THE AREA REACHING THE INTERIOR VALLEYS ABOUT 08Z
FRIDAY THEN EAST OF THE CASCADES BY 12Z. LOW END VFR CONDITIONS THIS
AFTERNOON WILL DETERIORATE TO MVFR SHORTLY AFTER 00Z THIS EVENING AS
PRECIPITATION INCREASES WITH THE APPROACH OF THE FRONT.

THERE IS LIKELY TO BE A PERIOD OF LOW LEVEL WIND SHEAR IN THE
INTERIOR FROM ABOUT KPAE SOUTHWARD AND ALONG THE COAST FOR A FEW
HOURS AHEAD OF THE FRONT AS WINDS AT 2000 FT INCREASE TO SSW 40-50KT
AND SURFACE WINDS REMAIN SELY.

POST FRONTAL ONSHORE FLOW WITH SCATTERED SHOWERS ARE EXPECTED BEHIND
THE FRONT LATE TONIGHT AND FRIDAY WITH MVFR CONDITIONS AND SOME
CLEARING AT TIMES IN THE LEE OF THE OLYMPICS. ISOLATED THUNDERSTORMS
ARE NOT OUT OF THE QUESTION ALONG THE COAST ON FRIDAY AS COLD AIR
ALOFT ARRIVES WITH AN UPPER LEVEL TROUGH. ALBRECHT

KSEA...EXPECT BKN-OVC035-040 WITH PERIODS OF LIGHT RAIN...WITH
CEILINGS DETERIORATING TO OVC015 BY 06Z. SE WIND 7-11 KT WILL SHIFT
TO S 11-17 KT WITH GUSTS TO 25 KT BEHIND THE FRONT 08Z-10Z. THERE
WILL BE 2-4 HOURS OF WIND 19035-40KT AT FL020 AHEAD OF THE INCOMING
FRONT ABOUT 05Z-08Z TIME PERIOD. ALBRECHT

&&

.MARINE...A FRONT ASSOCIATED WITH A 970 MB LOW WELL WEST OF HAIDA
GWAII WILL MOVE THROUGH THE WATERS TONIGHT. GALE FORCE WINDS CAN BE
EXPECTED OVER THE COASTAL WATERS AND AT THE EAST ENTRANCE TO THE
STRAIT UNTIL THE FRONT PASSES WITH SMALL CRAFT ADVISORY CONDITIONS
FOR THE STRAIT...NORTHERN INLAND WATERS...ADMIRALTY INLET AND PUGET
SOUND AND HOOD CANAL.

EXPECT MODERATE TO STRONG ONSHORE FLOW BEHIND THE FRONT AND WITH A
SURFACE TROUGH AS IT MOVES ACROSS THE AREA ON FRIDAY. SMALL CRAFT
ADVISORY CONDITIONS WILL CONTINUE OVER THE COASTAL WATERS AND
POSSIBLY SOME OF THE INTERIOR ZONES. ISOLATED THUNDERSTORMS CANNOT
BE RULED OUT OVER THE COASTAL WATERS ON FRIDAY IN A RATHER UNSTABLE
AIR MASS.

30-45 FOOT WAVES OVER A LARGE AREA OF THE NORTH CENTRAL PACIFIC WILL
DECAY TO A LONG PERIOD 22-25 FT SWELL THAT WILL REACH THE COAST
MIDDAY FRIDAY AND CONTINUE TO PUSH ONSHORE THROUGH SATURDAY. TIDAL
ANOMALIES ALONG THE COAST ARE JUST OVER 1 FOOT ABOVE NORMAL AND HIGH
TIDE OCCURS SATURDAY MORNING. SOME COASTAL FLOODING IS POSSIBLE
ALONG THE COAST AROUND THE HIGH TIDE ON SATURDAY...AND A COASTAL
FLOOD WATCH IS IN EFFECT. A HIGH SURF ADVISORY WAS ISSUED FOR THE
COAST FROM MIDDAY FRIDAY THROUGH FRIDAY NIGHT.

ANOTHER STRONG FRONT WILL ARRIVE ON SATURDAY WITH GALE
FORCE WINDS ONCE AGAIN LIKELY OVER THE COASTAL WATERS...THE NORTHERN
INLAND WATERS...AND THE STRAIT ENTRANCES. STRONG ONSHORE FLOW
SATURDAY NIGHT WILL SLOWLY DIMINISH ON SUNDAY. ALBRECHT

&&

.SEW WATCHES/WARNINGS/ADVISORIES...

WA...WIND ADVISORY THROUGH TONIGHT FOR THE SAN JUAN ISLANDS...
     WESTERN WHATCOM COUNTY...AND THE ADMIRALTY INLET AREA.
     WINTER WEATHER ADVISORY THROUGH TONIGHT FOR THE OLYMPICS.
     WINTER WEATHER ADVISORY FOR THE WEST SLOPES OF THE CASCADES
     4 PM PST THIS AFTERNOON THROUGH TONIGHT.
     HIGH SURF ADVISORY FOR THE NORTH AND CENTRAL COAST FROM LATE
     FRIDAY MORNING THROUGH EARLY SATURDAY MORNING.
     COASTAL FLOOD WATCH FOR THE NORTH AND CENTRAL COAST FROM
     SATURDAY MORNING THROUGH SATURDAY AFTERNOON.

PZ...GALE WARNING THROUGH TONIGHT COASTAL WATERS AND EAST
     ENTRANCE.
     SMALL CRAFT ADVISORY ALL REMAINING WATERS.
     SMALL CRAFT ADVISORY FOR ROUGH GRAYS HARBOR BAR TONIGHT THROUGH
     FRIDAY.
     GALE WATCH COAST...ENTRANCES TO THE STRAIT OF JUAN DE FUCA...
     ADMIRALTY INLET...AND NORTHERN INLAND WATERS FRIDAY NIGHT
     THROUGH SATURDAY.




&&

$$

YOU CAN SEE AN ILLUSTRATED VERSION OF THIS FORECAST DISCUSSION AT
WWW.WEATHER.GOV/SEATTLE/GAFD/LATEST_WEBAFD.HTML



















000
FXUS66 KSEW 182254 AAA
AFDSEW

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SEATTLE WA
300 PM PST THU DEC 18 2014

.SYNOPSIS...A FRONT WILL BRING RAIN AND LOCALLY WINDY CONDITIONS TO
WESTERN WASHINGTON THROUGH TONIGHT. AN UPPER LEVEL TROUGH WILL BRING
SCATTERED SHOWERS ON FRIDAY. STRONG MOIST WEST FLOW ALOFT OVER THE
NORTHEAST PACIFIC WILL BRING WIND AND RAIN INTO WESTERN WASHINGTON
THIS WEEKEND. A BROAD UPPER LEVEL RIDGE WILL REMAIN OVER THE REGION
EARLY NEXT WEEK FOR NOT QUITE AS WET WEATHER. COOLER TEMPERATURES
ARE POSSIBLE BY MID WEEK.

&&

.SHORT TERM...WARM ADVECTION RAIN IS FILLING IN ACROSS WRN WA THIS
AFTERNOON. VISIBLE SATELLITE IMAGERY IMPLIES THE SURFACE FRONT IS
NOW JUST INSIDE 130 W HEADING TOWARD WRN WA. IR/WV IMAGERY SHOWS A
WAVE FORMING ON THE SRN EXTENT OF THE FRONTAL BAND AS IT BEGINS TO
SPLIT. THIS WILL SLOW THE PROGRESS OF THE SYSTEM EWD BUT ALSO RESULT
IN WEAKER FLOW ALOFT SO OROGRAPHICS WILL NOT PLAY AS BIG A ROLE AS
USUAL. MODELS STILL SHOW 12 HOUR QPF TOTALS RANGING FROM ROUGHLY ONE
HALF TO ONE INCH LIQUID WITH LOCALLY HIGHER AMOUNTS. PLACES WHERE
THIS FALLS AS ALL SNOW COULD SEE UP TO 1 FOOT. SOME OF THE HIGHER
SKI RESORTS AND S/SW FACING SLOPES ARE MOST LIKELY TO SEE THESE TYPE
OF SNOW TOTALS. THE SNOW LEVEL IS DIFFICULT TO PINPOINT WITH THIS
SYSTEM WITH SOME FLUCTUATION LIKELY BETWEEN 3500 AND 5000 FEET.
TEMPERATURES IN MOST PASSES ARE STILL IN THE UPPER 20S TO AROUND 30
DEGREES...SO PRECIPITATION WILL LIKELY START AS SNOW EVEN AT
SNOQUALMIE PASS. A COUPLE INCHES MAY FALL...THEN SNOW LEVELS SHOULD
GENERALLY START TO RISE AS WARMER AIR STARTS TO WORK INLAND. THE
MAIN SNOW LEVEL SHOULD HOVER AROUND 4500 TO 5000 FEET TONIGHT WHICH
PUTS STEVENS PASS ON THE EDGE. UP TO 6 INCHES STILL SEEMS POSSIBLE
DEPENDING ON HOW MUCH RAIN MIXES IN. SNOW LEVELS WILL FALL BACK DOWN
TO AROUND 3000 FEET BEHIND THE FRONT BUT ONLY MINOR ADDITIONAL
ACCUMULATIONS EXPECTED FRIDAY MORNING.

SE PRESSURE GRADIENTS WILL CONTINUE TO TIGHTEN THIS EVENING. SE
WINDS IN THE ADMIRALTY INLET AREA AND SAN JUANS ARE CURRENTLY
GUSTING INTO THE LOW 30 MPH RANGE AND SHOULD PICK UP CONSIDERABLY
THIS EVENING. THE WIND ADVISORY WILL REMAIN IN PLACE FOR GUSTS TO 45
MPH ACROSS THE N INTERIOR...EXCLUDING WRN SKAGIT COUNTY. STRONGEST
WINDS WILL BE ALONG THE WATER AND AT PLACES EXPOSED TO SE WINDS. THE
WIND ADVISORY RUNS THROUGH MIDNIGHT TONIGHT.

IT WILL BE COOL AND SHOWERY ON FRIDAY AS THE FRONT MOVES E AND AN
UPPER TROUGH REACHES THE AREA. COLD TOPPED CU OFFSHORE INDICATES
UNSTABLE CONDITIONS BEHIND THE TROUGH. MODEL LI`S ARE NEGATIVE OVER
THE COASTAL WATERS BUT NOT OVER THE LAND AREAS. BUFFER FORECAST
SOUNDINGS SHOW THE UNSTABLE LAYER CAPPED AT 700 MB SO THUNDERSTORMS
WOULD SEEM UNLIKELY.

STRONG AND MOIST WLY FLOW DRIVEN BY A STRONG 180+ KT JET WILL STEER
A WARM FRONT INTO WRN WA ON SATURDAY. TIMING IS A LITTLE FASTER WITH
MOST MODELS DEVELOPING WIDESPREAD RAIN ACROSS WRN WA BY LATE FRIDAY
NIGHT OR EARLY SATURDAY MORNING. INITIALLY THE FLOW WILL BE OUT OF
THE S/SW AND STRONG AT 40 TO 50 KT. THIS WILL PRODUCE HEFTY
OROGRAPHICALLY ENHANCED RAINFALL AMOUNTS ALONG S/SW FACING SLOPES OF
THE OLYMPICS AND CASCADES. THIS WILL ALMOST CERTAINLY CAUSE FLOODING
ON THE SKOKOMISH RIVER BY LATER SATURDAY NIGHT. THE FLOW TURNS MORE
WLY SATURDAY NIGHT AND SUNDAY WHICH IS A FAVORABLE DIRECTION FOR
HEAVY RAIN IN MORE BASINS ACROSS THE W SLOPES OF THE CASCADES. THIS
WILL CAUSE ADDITIONAL FLOOD CONCERNS. REFER TO THE EXTENDED FLOOD
OUTLOOK STATEMENT AND HYDRO DISCUSSION BELOW FOR FURTHER DETAILS.

THIS NEXT SYSTEM WILL ALSO HAVE STRONGER SE PRESSURE GRADIENTS AND
STRONGER FLOW ALOFT AHEAD OF THE COLD FRONT ON SATURDAY. MESO MODELS
ARE SHOWING HIGH END ADVISORY LEVEL TYPE WINDS BUT HIGH WIND IN A
COUPLE SPOTS CANNOT BE RULED OUT EITHER. THIS IS STILL A COUPLE DAYS
OUT AND WILL OPT TO MAINTAIN A HIGH END ADVISORY WIND FORECAST FOR
THE COAST/N INTERIOR. PUGET SOUND WILL ALSO BECOME
BREEZY...ESPECIALLY AS GRADIENTS BECOME MORE SLY SATURDAY NIGHT AND
SUNDAY. BUT FORECAST GRADIENTS DO NOT SEEM TO SUPPORT EVEN ADVISORY
LEVEL WINDS FOR PUGET SOUND AT THIS TIME.

THE BAROCLINIC BOUNDARY WILL START TO DRIFT SWD SUNDAY AFTERNOON
DIRECTING THE HEAVIEST PRECIPITATION INTO THE WA CASCADES FROM
ABOUT KING COUNTY SWD INTO THE N/CENTRAL OREGON CASCADES. THIS WILL
HELP MITIGATE FLOODING CONCERNS ACROSS THE FAR N ALTHOUGH DETAILS ON
WHERE THIS BOUNDARY SETS UP REMAINS UNCERTAIN. THERE DOES SEEM TO BE
PRETTY GOOD CONSENSUS EVOLVING AMONG THE MODELS THAT THE HEAVY
MOUNTAIN RAIN WILL TAPER OFF FROM N TO S ON SUNDAY AND MOSTLY SHUT
OFF BY SUNDAY NIGHT AS THE RIDGE BEGINS TO BUILD.

.LONG TERM...THE EXTENDED FORECAST REMAINS CHALLENGING WITH A WIDE
RANGE OF SOLUTIONS AMONG THE MODELS. THERE IS SOME AGREEMENT THAT
MONDAY WILL GENERALLY FEATURE SHOWERS OR A LULL IN RAINFALL AS
HIGHER PRESSURE BUILDS ALOFT. MODELS DO NOT AGREE ON THE STRENGTH OR
TRACK OF THE NEXT SYSTEM APPROACHING FROM THE W ON TUESDAY. THE
LATEST 12/18Z GFS BRINGS THE LOW IN FURTHER N WHICH WOULD STILL
PRODUCE WARM ADVECTION RAINFALL ACROSS THE AREA...THOUGH NOT AS MUCH
AS WAS SHOWN BY PREVIOUS SOLUTIONS.

MOST MODELS DIG A COLD UPPER TROUGH SWD OUT OF B.C. THROUGH WRN WA
ON WEDNESDAY. THIS COULD USHER IN COOLER AIR BUT MODELS DISAGREE ON
THE EXTENT OF RIDGING OFFSHORE AND WHERE IT SETS UP. THE ECMWF
CONTINUES TO BE ONE OF THE COLDER SOLUTIONS AND HAS THE KONA LOW CUT
OFF FURTHER W...THUS A FURTHER W DEVELOPMENT OF THE UPPER RIDGE. THE
KONA LOW IS FURTHER E ON THE GFS40 WITH A RIDGE NEAR 135-140 WHICH
WILL STILL USHER IN COOLER NLY FLOW BUT PERHAPS LESS CHANCE OF
PRECIPITATION. IT WILL BE INTERESTING TO SEE HOW THIS PANS OUT BUT A
SWITCH TO COOLER OR COLD TEMPERATURES IS A POSSIBILITY BY THURSDAY.
POPS WERE TRIMMED WAY BACK AND MAY NEED TO BE REMOVED ALTOGETHER IF
MODEL TRENDS CONTINUE. SNOW LEVELS WILL ALSO BE MUCH
LOWER...POSSIBLY TO SEA LEVEL...BUT IT IS VERY UNCLEAR AS TO HOW
MUCH MOISTURE WILL REMAIN BY THAT TIME.

&&

.HYDROLOGY...THOUGH RAIN WILL FALL AT TIMES...FLOODING IS UNLIKELY
ON ANY RIVER THROUGH SATURDAY.

HEAVY RAIN COULD CAUSE FLOODING BY LATE THIS WEEKEND. A WEATHER
SYSTEM WITH STRONG WESTERLY FLOW ALOFT WILL BRING HEAVY RAIN AT
TIMES TO THE COAST AND OLYMPICS ON SATURDAY. HEAVY RAIN WILL SPREAD
INTO THE CASCADES SATURDAY AFTERNOON.

MODELS CURRENTLY TAPER RAIN OVER THE OLYMPICS ON SUNDAY BUT KEEP
HEAVY RAIN GOING IN THE CASCADES...ESPECIALLY OVER THE CASCADES FROM
ABOUT KING COUNTY SOUTH. THE TOTAL MODEL RAINFALL OVER ABOUT 48
HOURS FROM SATURDAY MORNING THROUGH SUNDAY NIGHT AMOUNTS TO AROUND
FOUR TO SIX INCHES OVER THE OLYMPICS AND CENTRAL CASCADES WITH A
TEN-INCH BULLSEYE OVER MOUNT RAINIER. THE SNOW LEVEL WILL BE ABOVE
5000 FEET ON SATURDAY AND SUNDAY BEFORE FALLING TO 3500 FEET OR SO
SUNDAY NIGHT.

THESE RAINFALL AMOUNTS ARE ENOUGH TO CAUSE FLOODING. AT THIS TIME
THE RIVERS MOST LIKELY TO FLOOD ARE THE ONES FLOWING OFF THE
CASCADES OF KING...PIERCE...AND LEWIS COUNTIES...AS WELL AS THE
UNUSUALLY FLOOD-PRONE SKOKOMISH RIVER IN MASON COUNTY. ANY FLOODING
WOULD LIKELY BEGIN AS EARLY AS SATURDAY NIGHT ON THE SKOKOMISH
RIVER. THE CASCADE RIVERS COULD FLOOD SUNDAY WITH CRESTS SUNDAY
NIGHT OR MONDAY.

A COOLER AND DRIER AIR MASS IS FORECAST TO BE OVER THE AREA NEXT
WEEK. AFTER MONDAY THE RIVERS WILL RECEDE AND ANY FURTHER FLOODING
IS UNLIKELY. BURKE

&&

.AVIATION...A STRONG PACIFIC FRONTAL SYSTEM OVER THE OFFSHORE WATERS
WILL MOVE ACROSS THE AREA TONIGHT. SOUTHWESTERLY FLOW ALOFT WILL
INCREASE AND BECOMING STRONG THIS EVENING THEN BECOMING MODERATE ON
FRIDAY. THE AIR MASS IS MOIST AND STABLE...IT WILL BECOME SOMEWHAT
UNSTABLE LATE TONIGHT AND FRIDAY BEHIND THE FRONT.

AT 2230Z A STRONG FRONT WAS MOVING THROUGH THE OFFSHORE WATERS. IT
WILL PUSH ACROSS THE AREA REACHING THE INTERIOR VALLEYS ABOUT 08Z
FRIDAY THEN EAST OF THE CASCADES BY 12Z. LOW END VFR CONDITIONS THIS
AFTERNOON WILL DETERIORATE TO MVFR SHORTLY AFTER 00Z THIS EVENING AS
PRECIPITATION INCREASES WITH THE APPROACH OF THE FRONT.

THERE IS LIKELY TO BE A PERIOD OF LOW LEVEL WIND SHEAR IN THE
INTERIOR FROM ABOUT KPAE SOUTHWARD AND ALONG THE COAST FOR A FEW
HOURS AHEAD OF THE FRONT AS WINDS AT 2000 FT INCREASE TO SSW 40-50KT
AND SURFACE WINDS REMAIN SELY.

POST FRONTAL ONSHORE FLOW WITH SCATTERED SHOWERS ARE EXPECTED BEHIND
THE FRONT LATE TONIGHT AND FRIDAY WITH MVFR CONDITIONS AND SOME
CLEARING AT TIMES IN THE LEE OF THE OLYMPICS. ISOLATED THUNDERSTORMS
ARE NOT OUT OF THE QUESTION ALONG THE COAST ON FRIDAY AS COLD AIR
ALOFT ARRIVES WITH AN UPPER LEVEL TROUGH. ALBRECHT

KSEA...EXPECT BKN-OVC035-040 WITH PERIODS OF LIGHT RAIN...WITH
CEILINGS DETERIORATING TO OVC015 BY 06Z. SE WIND 7-11 KT WILL SHIFT
TO S 11-17 KT WITH GUSTS TO 25 KT BEHIND THE FRONT 08Z-10Z. THERE
WILL BE 2-4 HOURS OF WIND 19035-40KT AT FL020 AHEAD OF THE INCOMING
FRONT ABOUT 05Z-08Z TIME PERIOD. ALBRECHT

&&

.MARINE...A FRONT ASSOCIATED WITH A 970 MB LOW WELL WEST OF HAIDA
GWAII WILL MOVE THROUGH THE WATERS TONIGHT. GALE FORCE WINDS CAN BE
EXPECTED OVER THE COASTAL WATERS AND AT THE EAST ENTRANCE TO THE
STRAIT UNTIL THE FRONT PASSES WITH SMALL CRAFT ADVISORY CONDITIONS
FOR THE STRAIT...NORTHERN INLAND WATERS...ADMIRALTY INLET AND PUGET
SOUND AND HOOD CANAL.

EXPECT MODERATE TO STRONG ONSHORE FLOW BEHIND THE FRONT AND WITH A
SURFACE TROUGH AS IT MOVES ACROSS THE AREA ON FRIDAY. SMALL CRAFT
ADVISORY CONDITIONS WILL CONTINUE OVER THE COASTAL WATERS AND
POSSIBLY SOME OF THE INTERIOR ZONES. ISOLATED THUNDERSTORMS CANNOT
BE RULED OUT OVER THE COASTAL WATERS ON FRIDAY IN A RATHER UNSTABLE
AIR MASS.

30-45 FOOT WAVES OVER A LARGE AREA OF THE NORTH CENTRAL PACIFIC WILL
DECAY TO A LONG PERIOD 22-25 FT SWELL THAT WILL REACH THE COAST
MIDDAY FRIDAY AND CONTINUE TO PUSH ONSHORE THROUGH SATURDAY. TIDAL
ANOMALIES ALONG THE COAST ARE JUST OVER 1 FOOT ABOVE NORMAL AND HIGH
TIDE OCCURS SATURDAY MORNING. SOME COASTAL FLOODING IS POSSIBLE
ALONG THE COAST AROUND THE HIGH TIDE ON SATURDAY...AND A COASTAL
FLOOD WATCH IS IN EFFECT. A HIGH SURF ADVISORY WAS ISSUED FOR THE
COAST FROM MIDDAY FRIDAY THROUGH FRIDAY NIGHT.

ANOTHER STRONG FRONT WILL ARRIVE ON SATURDAY WITH GALE
FORCE WINDS ONCE AGAIN LIKELY OVER THE COASTAL WATERS...THE NORTHERN
INLAND WATERS...AND THE STRAIT ENTRANCES. STRONG ONSHORE FLOW
SATURDAY NIGHT WILL SLOWLY DIMINISH ON SUNDAY. ALBRECHT

&&

.SEW WATCHES/WARNINGS/ADVISORIES...

WA...WIND ADVISORY THROUGH TONIGHT FOR THE SAN JUAN ISLANDS...
     WESTERN WHATCOM COUNTY...AND THE ADMIRALTY INLET AREA.
     WINTER WEATHER ADVISORY THROUGH TONIGHT FOR THE OLYMPICS.
     WINTER WEATHER ADVISORY FOR THE WEST SLOPES OF THE CASCADES
     4 PM PST THIS AFTERNOON THROUGH TONIGHT.
     HIGH SURF ADVISORY FOR THE NORTH AND CENTRAL COAST FROM LATE
     FRIDAY MORNING THROUGH EARLY SATURDAY MORNING.
     COASTAL FLOOD WATCH FOR THE NORTH AND CENTRAL COAST FROM
     SATURDAY MORNING THROUGH SATURDAY AFTERNOON.

PZ...GALE WARNING THROUGH TONIGHT COASTAL WATERS AND EAST
     ENTRANCE.
     SMALL CRAFT ADVISORY ALL REMAINING WATERS.
     SMALL CRAFT ADVISORY FOR ROUGH GRAYS HARBOR BAR TONIGHT THROUGH
     FRIDAY.
     GALE WATCH COAST...ENTRANCES TO THE STRAIT OF JUAN DE FUCA...
     ADMIRALTY INLET...AND NORTHERN INLAND WATERS FRIDAY NIGHT
     THROUGH SATURDAY.




&&

$$

YOU CAN SEE AN ILLUSTRATED VERSION OF THIS FORECAST DISCUSSION AT
WWW.WEATHER.GOV/SEATTLE/GAFD/LATEST_WEBAFD.HTML


















000
FXUS66 KSEW 181739 AAA
AFDSEW

AREA FORECAST DISCUSSION...UPDATED
NATIONAL WEATHER SERVICE SEATTLE WA
935 AM PST THU DEC 18 2014

UPDATED ADVISORIES.

.SYNOPSIS...AN APPROACHING FRONTAL SYSTEM WILL BRING A CHANCE OF
RAIN TODAY...FOLLOWED BY MORE CONTINUOUS RAIN TONIGHT AS THE COLD
FRONT MOVES INLAND. AN UPPER LEVEL TROUGH WILL BRING SCATTERED
SHOWERS ON FRIDAY. STRONG MOIST WEST FLOW ALOFT OVER THE NORTHEAST
PACIFIC WILL BRING A WINDY AND RAINY PATTERN THIS WEEKEND. A BROAD
UPPER LEVEL RIDGE WILL REMAIN OVER THE REGION EARLY NEXT WEEK FOR
NOT QUITE AS WET WEATHER.

&&

.SHORT TERM...RADAR AND OBS INDICATE SHOWERS ACROSS MUCH OF WRN WA
THIS MORNING. ALTHOUGH A WEAK UPPER RIDGE IS TRAVERSING THE AREA
TODAY...THE FLOW REMAINS MOIST AND SLY. BUFFER SOUNDS SHOW THE AIR
MASS BELOW 750 MB TO BE WEAKLY UNSTABLE THROUGH MIDDAY SO SHOWERS
WILL CONTINUE THROUGH THE MORNING AND PROBABLY UP THE POINT WHEN
WARM ADVECTION RAIN BEGINS.

IR SATELLITE IMAGERY AND THE COASTAL RADAR SHOW MORE STEADY RAIN
APPROACHING THE COAST. THIS WILL SPREAD INLAND LATE IN THE DAY.
BRIGHTER CLOUD TOPS APPEAR TO INDICATE SOME SPLITTING ALREADY
OCCURING WITH THE FRONT. A STRONGER PORTION IS MOVING E-NE INTO
B.C./WA AND ANOTHER PORTION PUSHING DUE E INTO OREGON. MODELS
INDICATE THE FRONT HOLDS TOGETHER ENOUGH TO PRODUCE MORE WIDESPREAD
RAINFALL THAN PAST SYSTEMS THIS WEEK BUT IT WILL BE IN A WEAKENING
STATE AS IT ARRIVES LATER TODAY/EARLY THIS EVENING.

QPF AMOUNTS ON VARIOUS MESO MODELS GENERALLY AVERAGE A HALF TO ONE
INCH LIQUID IN 12 HOURS FROM 00Z-12Z TONIGHT OVER THE MOUNTAINS.
AREAS THAT PREDOMINATELY REMAIN AS SNOW THROUGH THE EVENT COULD SEE
UP TO A FOOT OF SNOW. SNOW LEVELS ARE THE TRICKY PART OF THE
FORECAST AS CURRENT PASS TEMPERATURES ARE IN THE UPPER 20S WITH ELY
GRADIENT WHICH MAY KEEP SOME PASSES COLD FOR SOME TIME THIS EVENING.
THE MAIN SNOW LEVEL IS CURRENTLY NEAR 3500 FEET BASED ON THE KUIL
FREEZING LEVELS MINUS 1K FT. THIS WILL CLIMB AS WARM ADVECTION
PRECIPITATION OVERSPREADS THE AREA BY LATE TODAY OR THIS EVENING.
WILL GO AHEAD AND ISSUE A SNOW ADVISORY FOR 5 TO 10 INCH SNOW
AMOUNTS BUT STRESSING THE LOWER END AMOUNTS WILL FALL AT HIGHER
PASSES SUCH AS WHITE PASS AND STEVENS PASS ASSUMING SOME CHANGE OVER
TO RAIN OR FREEZING RAIN AS THE FRONT PUSHES ACROSS LATER TONIGHT.
SNOQUALMIE PASS WILL LIKELY SEE SNOW CHANGE OVER TO RAIN PRETTY
QUICKLY WITH LESS THAN A COUPLE INCHES THERE. THE FRONT WILL
ACTUALLY HELP TO MIX THE COLDER AIR OUT OF THE PASSES AND RAISE SNOW
LEVELS THERE. HOWEVER...THE MAIN FREE AIR SNOW LEVELS WILL FALL BACK
TO AROUND 3000 FEET FRIDAY MORNING AFTER LIFTING TO 4500-5000 FEET
TONIGHT. SKI RESORTS EXPOSED TO S/SW FLOW SUCH AS MOUNT BAKER AND
PARADISE SHOULD DO BEST IN THIS FLOW PATTERN IF THEY REMAIN AS ALL
SNOW WITH UP TO 10 INCHES IN THESE AREAS.

LASTLY...WINDY CONDITIONS ARE EXPECTED TO DEVELOP UP N LATER THIS
AFTERNOON THROUGH THIS EVENING. SE GRADIENTS TIGHTEN AND A MESO LOW
WILL LIKELY FORM AROUND PORT ANGELES/SEQUIM.  THIS SHOULD INDUCE
LOCALLY STRONGER SE WINDS W/ GUSTS TO 45 MPH ACROSS ADMIRALTY
INLET...THE SAN JUANS...AND EXPOSED LOCATIONS ALONG THE SHORES OF
WRN WHATCOM COUNTY. BOTH THE HRRR/NAM12 SHOW LOW END ADVISORY WINDS
AND WILL PLAN TO ISSUE AN ADVISORY THIS MORNING FOR THE LATE
AFTERNOON AND EVENING HOURS.

A MOIST ONSHORE POST-FRONTAL PATTERN DEVELOPS FRIDAY WITH WEAK
INSTABILITY IN THE LOWER LEVELS. THIS SHOULD TRANSLATE TO SHOWERS
FOR OUR AREA UNTIL THE NEXT SYSTEM ARRIVES. LATEST 06Z/12Z MODELS
BRING WARM ADVECTION RAIN TO THE COAST LATE FRIDAY NIGHT...THEN
OVERSPREADING THE ENTIRE AREA BY THE MID MORNING HOURS ON SATURDAY.
MODELS CONTINUE TO SHOW A LOT OF FLOW SO RAINFALL RATES WILL BE
HEAVY ALONG THE S/SW FACING SLOPES OF THE MOUNTAINS...ESPECIALLY THE
OLYMPICS. A TRAILING MOISTURE PLUM WILL BECOME DIRECTED AT WRN WA BY
SATURDAY EVENING AS THE FLOW TURNS MORE WLY. THIS WILL GENERATE
ADDITIONAL OROGRAPHICALLY ENHANCED RAIN ALONG THE W/SW SLOPES OF THE
OLYMPICS/CASCADES SATURDAY NIGHT INTO EARLY SUNDAY. THIS COULD CAUSE
SOME MINOR FLOODING ON PRONE RIVERS...SEE THE LATEST HYDRO
DISCUSSION BELOW FOR DETAILS. SE GRADIENTS WILL ALSO BE QUITE STRONG
WITH THE WARM FRONT. AREAS FROM ADMIRALTY INLET NWD WILL LIKELY NEED
A WIND ADVISORY AND POSSIBLY THE COAST. MERCER

.LONG TERM...NO UPDATE FROM PREVIOUS DISCUSSION...ECMWF AND GFS SHOW
STRONG ZONAL FLOW CONTINUING INTO EARLY NEXT WEEK WITH A BROAD FLAT
UPPER LEVEL RIDGE OVER THE REGION. LOTS OF FLOW THROUGH THE RIDGE
WILL KEEP THIS A GENERALLY WET AND BREEZY PERIOD THROUGH SUNDAY. THE
MAIN PROBLEM WILL REMAIN HEAVY RAIN SATURDAY NIGHT. FAIRLY STRONG
WESTERLY 850 MB FLOW WILL REMAIN 30-45KT SATURDAY NIGHT INTO SUNDAY
MORNING...THEN GRADUALLY DIMINISH OVER THE NORTH AND CENTRAL PART OF
W WA SUNDAY AFTERNOON. STRONGER W FLOW WILL CONTINUE OVER NW OREGON
AND THE SOUTHERN WA CASCADES. THERE COULD BE ANOTHER 2-3 INCHES OF
QPF OVER THE CENTRAL CASCADES 12Z SUNDAY THROUGH 12Z MONDAY WHICH
COULD BRING SOME CASCADE RIVERS CLOSE TO FLOOD STAGE.

THE BROAD FLAT RIDGE MAINTAINS STRONG SOMEWHAT MOIST W FLOW ALOFT
OVER THE AREA MONDAY AND TUESDAY...BUT THE AIR MASS IS DRIER FOR
MUCH LESS RAIN. GFS/ECMWF BOTH BRING AN UPPER LEVEL SHORTWAVE TROUGH
ACROSS THE AREA ON WEDNESDAY...THEN DEVELOP COOL DRY N FLOW ALOFT
BEHIND IT FOR THURSDAY. WE WILL SEE IF THIS MODEL AGREEMENT HOLDS.
KAM

&&

.HYDROLOGY...NO UPDATE FROM PREVIOUS DISCUSSION...RIVER FLOODING IS
NOT EXPECTED THROUGH FRIDAY NIGHT. A MOIST WESTERLY FLOW PATTERN
WILL DEVELOP SATURDAY AND CONTINUE THROUGH SUNDAY NIGHT WITH HEAVY
RAIN AT TIMES IN THE MOUNTAINS. A STRONG WARM FRONT WILL CROSS THE
AREA SATURDAY WITH STRONG S FLOW OVER THE OLYMPICS BECOMING W BY
LATE AFTERNOON. THE STRONG W FLOW WILL REACH THE CASCADES SATURDAY
NIGHT. 2-3 INCHES OF RAIN ARE EXPECTED OVER THE OLYMPICS AND PARTS
OF THE CASCADES DURING THE 24 HOUR PERIOD FROM 12Z SATURDAY THROUGH
12Z SUNDAY. THIS COULD CAUSE ANOTHER ROUND OF FLOODING ON THE
SKOKOMISH RIVER AND PRIME SOME OF THE CASCADE RIVERS.

LOW LEVEL W FLOW ALOFT OVER W WA WILL DIMINISH SUNDAY AND SUNDAY
NIGHT AS THE CORE OF STRONGEST WINDS SLIDES DOWN OVER NW OREGON AND
THE SOUTHERN WA CASCADES. STILL...ANOTHER 2-3 INCHES OF RAIN COULD
FALL OVER THE CENTRAL CASCADES BETWEEN 12Z SUNDAY AND 12Z MONDAY.
THIS ADDED RAINFALL COULD PUSH SOME OF THE MORE FLOOD PRONE CASCADE
RIVERS CLOSE TO FLOOD STAGE. KAM

&&

.AVIATION...A STRONG PACIFIC FRONTAL SYSTEM OVER THE OFFSHORE WATERS
WILL MOVE ACROSS THE AREA TONIGHT. SOUTHWESTERLY FLOW ALOFT WILL
INCREASE AND BECOMING STRONG THIS EVENING THEN BECOMING MODERATE ON
FRIDAY. THE AIR MASS IS MOIST AND STABLE...IT WILL BECOME SOMEWHAT
UNSTABLE LATE TONIGHT AND FRIDAY.

AT 1630Z A STRONG FRONT AROUND 130W IS MOVING EAST. IT WILL PUSH
ACROSS THE AREA REACHING THE INTERIOR VALLEYS JUST AFTER 08Z FRIDAY
THEN EAST OF THE CASCADES BY 12Z. PRESSURE GRADIENTS ARE
INCREASINGLY SOUTHEASTERLY IN ADVANCE OF THE FRONT...SO DESPITE RAIN
BANDS OFFSHORE MOVING INLAND...CEILINGS WILL BECOME PREDOMINATELY
VFR. EXPECT CEILINGS AND VISIBILITIES TO DETERIORATE TO MVFR ALONG
THE COAST MIDDAY AND IN THE INTERIOR SHORTLY AFTER 00Z THIS EVENING
AS PRECIPITATION DEVELOPS AND GRADUALLY INCREASES WITH THE APPROACH
OF THE FRONT.

THERE COULD BE A SHORT PERIOD OF LOW LEVEL WIND SHEAR IN THE
INTERIOR FROM ABOUT KPAE SOUTHWARD FOR A FEW HOURS AHEAD OF THE
FRONT AS WINDS AT 2000 FT INCREASE TO SSW 40KT AND SURFACE WINDS
REMAIN SELY.

POST FRONTAL ONSHORE FLOW WITH SCATTERED SHOWERS ARE EXPECTED BEHIND
THE FRONT LATE TONIGHT AND FRIDAY WITH MVFR CONDITIONS AND SOME
CLEARING AT TIMES IN THE LEE OF THE OLYMPICS. ISOLATED THUNDERSTORMS
ARE NOT OUT OF THE QUESTION ALONG THE COAST ON FRIDAY AS COLD AIR
ALOFT ARRIVES WITH AN UPPER LEVEL TROUGH. ALBRECHT

KSEA...EXPECT BKN-OVC040-050 TODAY. PERIODS OF -RA WILL DEVELOP THIS
AFTERNOON. CEILINGS WILL GRADUALLY LOWER TO MVFR THIS EVENING WITH
CIGS BOTTOMING OUT AROUND 015 A COUPLE HOURS AHEAD OF FRONTAL
PASSAGE 08Z-10Z FRIDAY. EXPECT SE WIND 5 KT TO INCREASE TO 9-11 KT
THIS EVENING THEN SHIFT TO S 10-14 KT BEHIND THE FRONT 08Z-10Z.
THERE WILL BE A COUPLE HOURS OF WIND 18035-40KT AT FL020 AHEAD OF
THE INCOMING FRONT ABOUT 06Z-08Z TIME PERIOD. ALBRECHT

&&

.MARINE...A FRONT ASSOCIATED WITH A 968 MB LOW WELL WEST OF HAIDA
GWAII WILL MOVE THROUGH THE OFFSHORE WATERS TODAY...THEN INLAND
TONIGHT. A PERIOD OF GALE FORCE WINDS CAN BE EXPECTED OVER THE
COASTAL WATERS BEGINNING MIDDAY TODAY THROUGH THIS EVENING WITH
SMALL CRAFT ADVISORY CONDITIONS FOR THE STRAIT...NORTHERN INLAND
WATERS...AND ADMIRALTY INLET. GALE FORCE WINDS ARE NOW EXPECTED AT
THE EAST ENTRANCE TO THE STRAIT OF JUAN DE FUCA THIS AFTERNOON AND
TONIGHT AS A MESOSCALE LOW DEVELOPS TO THE NORTHEAST OF THE
OLYMPICS.

EXPECT MODERATE TO STRONG ONSHORE FLOW BEHIND THE FRONT AND WITH A
SURFACE TROUGH AS IT MOVES ACROSS THE AREA ON FRIDAY. SMALL CRAFT
ADVISORY CONDITIONS WILL CONTINUE OVER THE COASTAL WATERS AND
POSSIBLY SOME OF THE INTERIOR ZONES. ISOLATED THUNDERSTORMS CANNOT
BE RULED OUT OVER THE COASTAL WATERS ON FRIDAY IN A RATHER UNSTABLE
AIR MASS.

30-45 FOOT WAVES OVER A LARGE AREA OF THE NORTH CENTRAL PACIFIC WILL
DECAY TO A LONG PERIOD 22-23 FT SWELL THAT WILL REACH THE COAST
FRIDAY AFTERNOON AND CONTINUE TO PUSH ONSHORE THROUGH SATURDAY.
TIDAL ANOMALIES ALONG THE COAST ARE JUST OVER 1 FOOT ABOVE NORMAL
AND HIGH TIDE OCCURS SATURDAY MORNING. IF SWELL REMAINS HIGH INTO
SATURDAY MORNING AS CURRENTLY EXPECTED...SOME COASTAL FLOODING IS
POSSIBLE. A COASTAL FLOOD WATCH MAY BE REQUIRED FOR PORTIONS OF THE
COAST FOR THE SATURDAY MORNING HIGH TIDE.

ANOTHER STRONG FRONT WILL ARRIVE ON SATURDAY WITH GALE
FORCE WINDS ONCE AGAIN LIKELY OVER THE COASTAL WATERS...THE NORTHERN
INLAND WATERS...AND THE STRAIT ENTRANCES. ALBRECHT

&&

.SEW WATCHES/WARNINGS/ADVISORIES...
WA...WIND ADVISORY THROUGH TONIGHT FOR THE SAN JUAN ISLANDS...
      WESTERN WHATCOM COUNTY...AND THE ADMIRALTY INLET AREA.
     WINTER WEATHER ADVISORY THROUGH TONIGHT FOR THE OLYMPICS.
     WINTER WEATHER ADVISORY FOR THE WEST SLOPES OF THE CASCADES
      4 PM PST THIS AFTERNOON THROUGH TONIGHT.
PZ...GALE WARNING THROUGH TONIGHT COASTAL WATERS AND EAST ENTRANCE.
     SMALL CRAFT ADVISORY ALL REMAINING WATERS.
     SMALL CRAFT ADVISORY FOR ROUGH GRAYS HARBOR BAR TONIGHT THROUGH
      FRIDAY.

&&

$$

YOU CAN SEE AN ILLUSTRATED VERSION OF THIS FORECAST DISCUSSION AT
WWW.WEATHER.GOV/SEATTLE/GAFD/LATEST_WEBAFD.HTML
















000
FXUS66 KSEW 181739 AAA
AFDSEW

AREA FORECAST DISCUSSION...UPDATED
NATIONAL WEATHER SERVICE SEATTLE WA
935 AM PST THU DEC 18 2014

UPDATED ADVISORIES.

.SYNOPSIS...AN APPROACHING FRONTAL SYSTEM WILL BRING A CHANCE OF
RAIN TODAY...FOLLOWED BY MORE CONTINUOUS RAIN TONIGHT AS THE COLD
FRONT MOVES INLAND. AN UPPER LEVEL TROUGH WILL BRING SCATTERED
SHOWERS ON FRIDAY. STRONG MOIST WEST FLOW ALOFT OVER THE NORTHEAST
PACIFIC WILL BRING A WINDY AND RAINY PATTERN THIS WEEKEND. A BROAD
UPPER LEVEL RIDGE WILL REMAIN OVER THE REGION EARLY NEXT WEEK FOR
NOT QUITE AS WET WEATHER.

&&

.SHORT TERM...RADAR AND OBS INDICATE SHOWERS ACROSS MUCH OF WRN WA
THIS MORNING. ALTHOUGH A WEAK UPPER RIDGE IS TRAVERSING THE AREA
TODAY...THE FLOW REMAINS MOIST AND SLY. BUFFER SOUNDS SHOW THE AIR
MASS BELOW 750 MB TO BE WEAKLY UNSTABLE THROUGH MIDDAY SO SHOWERS
WILL CONTINUE THROUGH THE MORNING AND PROBABLY UP THE POINT WHEN
WARM ADVECTION RAIN BEGINS.

IR SATELLITE IMAGERY AND THE COASTAL RADAR SHOW MORE STEADY RAIN
APPROACHING THE COAST. THIS WILL SPREAD INLAND LATE IN THE DAY.
BRIGHTER CLOUD TOPS APPEAR TO INDICATE SOME SPLITTING ALREADY
OCCURING WITH THE FRONT. A STRONGER PORTION IS MOVING E-NE INTO
B.C./WA AND ANOTHER PORTION PUSHING DUE E INTO OREGON. MODELS
INDICATE THE FRONT HOLDS TOGETHER ENOUGH TO PRODUCE MORE WIDESPREAD
RAINFALL THAN PAST SYSTEMS THIS WEEK BUT IT WILL BE IN A WEAKENING
STATE AS IT ARRIVES LATER TODAY/EARLY THIS EVENING.

QPF AMOUNTS ON VARIOUS MESO MODELS GENERALLY AVERAGE A HALF TO ONE
INCH LIQUID IN 12 HOURS FROM 00Z-12Z TONIGHT OVER THE MOUNTAINS.
AREAS THAT PREDOMINATELY REMAIN AS SNOW THROUGH THE EVENT COULD SEE
UP TO A FOOT OF SNOW. SNOW LEVELS ARE THE TRICKY PART OF THE
FORECAST AS CURRENT PASS TEMPERATURES ARE IN THE UPPER 20S WITH ELY
GRADIENT WHICH MAY KEEP SOME PASSES COLD FOR SOME TIME THIS EVENING.
THE MAIN SNOW LEVEL IS CURRENTLY NEAR 3500 FEET BASED ON THE KUIL
FREEZING LEVELS MINUS 1K FT. THIS WILL CLIMB AS WARM ADVECTION
PRECIPITATION OVERSPREADS THE AREA BY LATE TODAY OR THIS EVENING.
WILL GO AHEAD AND ISSUE A SNOW ADVISORY FOR 5 TO 10 INCH SNOW
AMOUNTS BUT STRESSING THE LOWER END AMOUNTS WILL FALL AT HIGHER
PASSES SUCH AS WHITE PASS AND STEVENS PASS ASSUMING SOME CHANGE OVER
TO RAIN OR FREEZING RAIN AS THE FRONT PUSHES ACROSS LATER TONIGHT.
SNOQUALMIE PASS WILL LIKELY SEE SNOW CHANGE OVER TO RAIN PRETTY
QUICKLY WITH LESS THAN A COUPLE INCHES THERE. THE FRONT WILL
ACTUALLY HELP TO MIX THE COLDER AIR OUT OF THE PASSES AND RAISE SNOW
LEVELS THERE. HOWEVER...THE MAIN FREE AIR SNOW LEVELS WILL FALL BACK
TO AROUND 3000 FEET FRIDAY MORNING AFTER LIFTING TO 4500-5000 FEET
TONIGHT. SKI RESORTS EXPOSED TO S/SW FLOW SUCH AS MOUNT BAKER AND
PARADISE SHOULD DO BEST IN THIS FLOW PATTERN IF THEY REMAIN AS ALL
SNOW WITH UP TO 10 INCHES IN THESE AREAS.

LASTLY...WINDY CONDITIONS ARE EXPECTED TO DEVELOP UP N LATER THIS
AFTERNOON THROUGH THIS EVENING. SE GRADIENTS TIGHTEN AND A MESO LOW
WILL LIKELY FORM AROUND PORT ANGELES/SEQUIM.  THIS SHOULD INDUCE
LOCALLY STRONGER SE WINDS W/ GUSTS TO 45 MPH ACROSS ADMIRALTY
INLET...THE SAN JUANS...AND EXPOSED LOCATIONS ALONG THE SHORES OF
WRN WHATCOM COUNTY. BOTH THE HRRR/NAM12 SHOW LOW END ADVISORY WINDS
AND WILL PLAN TO ISSUE AN ADVISORY THIS MORNING FOR THE LATE
AFTERNOON AND EVENING HOURS.

A MOIST ONSHORE POST-FRONTAL PATTERN DEVELOPS FRIDAY WITH WEAK
INSTABILITY IN THE LOWER LEVELS. THIS SHOULD TRANSLATE TO SHOWERS
FOR OUR AREA UNTIL THE NEXT SYSTEM ARRIVES. LATEST 06Z/12Z MODELS
BRING WARM ADVECTION RAIN TO THE COAST LATE FRIDAY NIGHT...THEN
OVERSPREADING THE ENTIRE AREA BY THE MID MORNING HOURS ON SATURDAY.
MODELS CONTINUE TO SHOW A LOT OF FLOW SO RAINFALL RATES WILL BE
HEAVY ALONG THE S/SW FACING SLOPES OF THE MOUNTAINS...ESPECIALLY THE
OLYMPICS. A TRAILING MOISTURE PLUM WILL BECOME DIRECTED AT WRN WA BY
SATURDAY EVENING AS THE FLOW TURNS MORE WLY. THIS WILL GENERATE
ADDITIONAL OROGRAPHICALLY ENHANCED RAIN ALONG THE W/SW SLOPES OF THE
OLYMPICS/CASCADES SATURDAY NIGHT INTO EARLY SUNDAY. THIS COULD CAUSE
SOME MINOR FLOODING ON PRONE RIVERS...SEE THE LATEST HYDRO
DISCUSSION BELOW FOR DETAILS. SE GRADIENTS WILL ALSO BE QUITE STRONG
WITH THE WARM FRONT. AREAS FROM ADMIRALTY INLET NWD WILL LIKELY NEED
A WIND ADVISORY AND POSSIBLY THE COAST. MERCER

.LONG TERM...NO UPDATE FROM PREVIOUS DISCUSSION...ECMWF AND GFS SHOW
STRONG ZONAL FLOW CONTINUING INTO EARLY NEXT WEEK WITH A BROAD FLAT
UPPER LEVEL RIDGE OVER THE REGION. LOTS OF FLOW THROUGH THE RIDGE
WILL KEEP THIS A GENERALLY WET AND BREEZY PERIOD THROUGH SUNDAY. THE
MAIN PROBLEM WILL REMAIN HEAVY RAIN SATURDAY NIGHT. FAIRLY STRONG
WESTERLY 850 MB FLOW WILL REMAIN 30-45KT SATURDAY NIGHT INTO SUNDAY
MORNING...THEN GRADUALLY DIMINISH OVER THE NORTH AND CENTRAL PART OF
W WA SUNDAY AFTERNOON. STRONGER W FLOW WILL CONTINUE OVER NW OREGON
AND THE SOUTHERN WA CASCADES. THERE COULD BE ANOTHER 2-3 INCHES OF
QPF OVER THE CENTRAL CASCADES 12Z SUNDAY THROUGH 12Z MONDAY WHICH
COULD BRING SOME CASCADE RIVERS CLOSE TO FLOOD STAGE.

THE BROAD FLAT RIDGE MAINTAINS STRONG SOMEWHAT MOIST W FLOW ALOFT
OVER THE AREA MONDAY AND TUESDAY...BUT THE AIR MASS IS DRIER FOR
MUCH LESS RAIN. GFS/ECMWF BOTH BRING AN UPPER LEVEL SHORTWAVE TROUGH
ACROSS THE AREA ON WEDNESDAY...THEN DEVELOP COOL DRY N FLOW ALOFT
BEHIND IT FOR THURSDAY. WE WILL SEE IF THIS MODEL AGREEMENT HOLDS.
KAM

&&

.HYDROLOGY...NO UPDATE FROM PREVIOUS DISCUSSION...RIVER FLOODING IS
NOT EXPECTED THROUGH FRIDAY NIGHT. A MOIST WESTERLY FLOW PATTERN
WILL DEVELOP SATURDAY AND CONTINUE THROUGH SUNDAY NIGHT WITH HEAVY
RAIN AT TIMES IN THE MOUNTAINS. A STRONG WARM FRONT WILL CROSS THE
AREA SATURDAY WITH STRONG S FLOW OVER THE OLYMPICS BECOMING W BY
LATE AFTERNOON. THE STRONG W FLOW WILL REACH THE CASCADES SATURDAY
NIGHT. 2-3 INCHES OF RAIN ARE EXPECTED OVER THE OLYMPICS AND PARTS
OF THE CASCADES DURING THE 24 HOUR PERIOD FROM 12Z SATURDAY THROUGH
12Z SUNDAY. THIS COULD CAUSE ANOTHER ROUND OF FLOODING ON THE
SKOKOMISH RIVER AND PRIME SOME OF THE CASCADE RIVERS.

LOW LEVEL W FLOW ALOFT OVER W WA WILL DIMINISH SUNDAY AND SUNDAY
NIGHT AS THE CORE OF STRONGEST WINDS SLIDES DOWN OVER NW OREGON AND
THE SOUTHERN WA CASCADES. STILL...ANOTHER 2-3 INCHES OF RAIN COULD
FALL OVER THE CENTRAL CASCADES BETWEEN 12Z SUNDAY AND 12Z MONDAY.
THIS ADDED RAINFALL COULD PUSH SOME OF THE MORE FLOOD PRONE CASCADE
RIVERS CLOSE TO FLOOD STAGE. KAM

&&

.AVIATION...A STRONG PACIFIC FRONTAL SYSTEM OVER THE OFFSHORE WATERS
WILL MOVE ACROSS THE AREA TONIGHT. SOUTHWESTERLY FLOW ALOFT WILL
INCREASE AND BECOMING STRONG THIS EVENING THEN BECOMING MODERATE ON
FRIDAY. THE AIR MASS IS MOIST AND STABLE...IT WILL BECOME SOMEWHAT
UNSTABLE LATE TONIGHT AND FRIDAY.

AT 1630Z A STRONG FRONT AROUND 130W IS MOVING EAST. IT WILL PUSH
ACROSS THE AREA REACHING THE INTERIOR VALLEYS JUST AFTER 08Z FRIDAY
THEN EAST OF THE CASCADES BY 12Z. PRESSURE GRADIENTS ARE
INCREASINGLY SOUTHEASTERLY IN ADVANCE OF THE FRONT...SO DESPITE RAIN
BANDS OFFSHORE MOVING INLAND...CEILINGS WILL BECOME PREDOMINATELY
VFR. EXPECT CEILINGS AND VISIBILITIES TO DETERIORATE TO MVFR ALONG
THE COAST MIDDAY AND IN THE INTERIOR SHORTLY AFTER 00Z THIS EVENING
AS PRECIPITATION DEVELOPS AND GRADUALLY INCREASES WITH THE APPROACH
OF THE FRONT.

THERE COULD BE A SHORT PERIOD OF LOW LEVEL WIND SHEAR IN THE
INTERIOR FROM ABOUT KPAE SOUTHWARD FOR A FEW HOURS AHEAD OF THE
FRONT AS WINDS AT 2000 FT INCREASE TO SSW 40KT AND SURFACE WINDS
REMAIN SELY.

POST FRONTAL ONSHORE FLOW WITH SCATTERED SHOWERS ARE EXPECTED BEHIND
THE FRONT LATE TONIGHT AND FRIDAY WITH MVFR CONDITIONS AND SOME
CLEARING AT TIMES IN THE LEE OF THE OLYMPICS. ISOLATED THUNDERSTORMS
ARE NOT OUT OF THE QUESTION ALONG THE COAST ON FRIDAY AS COLD AIR
ALOFT ARRIVES WITH AN UPPER LEVEL TROUGH. ALBRECHT

KSEA...EXPECT BKN-OVC040-050 TODAY. PERIODS OF -RA WILL DEVELOP THIS
AFTERNOON. CEILINGS WILL GRADUALLY LOWER TO MVFR THIS EVENING WITH
CIGS BOTTOMING OUT AROUND 015 A COUPLE HOURS AHEAD OF FRONTAL
PASSAGE 08Z-10Z FRIDAY. EXPECT SE WIND 5 KT TO INCREASE TO 9-11 KT
THIS EVENING THEN SHIFT TO S 10-14 KT BEHIND THE FRONT 08Z-10Z.
THERE WILL BE A COUPLE HOURS OF WIND 18035-40KT AT FL020 AHEAD OF
THE INCOMING FRONT ABOUT 06Z-08Z TIME PERIOD. ALBRECHT

&&

.MARINE...A FRONT ASSOCIATED WITH A 968 MB LOW WELL WEST OF HAIDA
GWAII WILL MOVE THROUGH THE OFFSHORE WATERS TODAY...THEN INLAND
TONIGHT. A PERIOD OF GALE FORCE WINDS CAN BE EXPECTED OVER THE
COASTAL WATERS BEGINNING MIDDAY TODAY THROUGH THIS EVENING WITH
SMALL CRAFT ADVISORY CONDITIONS FOR THE STRAIT...NORTHERN INLAND
WATERS...AND ADMIRALTY INLET. GALE FORCE WINDS ARE NOW EXPECTED AT
THE EAST ENTRANCE TO THE STRAIT OF JUAN DE FUCA THIS AFTERNOON AND
TONIGHT AS A MESOSCALE LOW DEVELOPS TO THE NORTHEAST OF THE
OLYMPICS.

EXPECT MODERATE TO STRONG ONSHORE FLOW BEHIND THE FRONT AND WITH A
SURFACE TROUGH AS IT MOVES ACROSS THE AREA ON FRIDAY. SMALL CRAFT
ADVISORY CONDITIONS WILL CONTINUE OVER THE COASTAL WATERS AND
POSSIBLY SOME OF THE INTERIOR ZONES. ISOLATED THUNDERSTORMS CANNOT
BE RULED OUT OVER THE COASTAL WATERS ON FRIDAY IN A RATHER UNSTABLE
AIR MASS.

30-45 FOOT WAVES OVER A LARGE AREA OF THE NORTH CENTRAL PACIFIC WILL
DECAY TO A LONG PERIOD 22-23 FT SWELL THAT WILL REACH THE COAST
FRIDAY AFTERNOON AND CONTINUE TO PUSH ONSHORE THROUGH SATURDAY.
TIDAL ANOMALIES ALONG THE COAST ARE JUST OVER 1 FOOT ABOVE NORMAL
AND HIGH TIDE OCCURS SATURDAY MORNING. IF SWELL REMAINS HIGH INTO
SATURDAY MORNING AS CURRENTLY EXPECTED...SOME COASTAL FLOODING IS
POSSIBLE. A COASTAL FLOOD WATCH MAY BE REQUIRED FOR PORTIONS OF THE
COAST FOR THE SATURDAY MORNING HIGH TIDE.

ANOTHER STRONG FRONT WILL ARRIVE ON SATURDAY WITH GALE
FORCE WINDS ONCE AGAIN LIKELY OVER THE COASTAL WATERS...THE NORTHERN
INLAND WATERS...AND THE STRAIT ENTRANCES. ALBRECHT

&&

.SEW WATCHES/WARNINGS/ADVISORIES...
WA...WIND ADVISORY THROUGH TONIGHT FOR THE SAN JUAN ISLANDS...
      WESTERN WHATCOM COUNTY...AND THE ADMIRALTY INLET AREA.
     WINTER WEATHER ADVISORY THROUGH TONIGHT FOR THE OLYMPICS.
     WINTER WEATHER ADVISORY FOR THE WEST SLOPES OF THE CASCADES
      4 PM PST THIS AFTERNOON THROUGH TONIGHT.
PZ...GALE WARNING THROUGH TONIGHT COASTAL WATERS AND EAST ENTRANCE.
     SMALL CRAFT ADVISORY ALL REMAINING WATERS.
     SMALL CRAFT ADVISORY FOR ROUGH GRAYS HARBOR BAR TONIGHT THROUGH
      FRIDAY.

&&

$$

YOU CAN SEE AN ILLUSTRATED VERSION OF THIS FORECAST DISCUSSION AT
WWW.WEATHER.GOV/SEATTLE/GAFD/LATEST_WEBAFD.HTML















000
FXUS66 KSEW 181712
AFDSEW

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SEATTLE WA
900 AM PST THU DEC 18 2014

.SYNOPSIS...AN APPROACHING FRONTAL SYSTEM WILL BRING A CHANCE OF
RAIN TODAY...FOLLOWED BY MORE CONTINUOUS RAIN TONIGHT AS THE COLD
FRONT MOVES INLAND. AN UPPER LEVEL TROUGH WILL BRING SCATTERED
SHOWERS ON FRIDAY. STRONG MOIST WEST FLOW ALOFT OVER THE NORTHEAST
PACIFIC WILL BRING A WINDY AND RAINY PATTERN THIS WEEKEND. A BROAD
UPPER LEVEL RIDGE WILL REMAIN OVER THE REGION EARLY NEXT WEEK FOR
NOT QUITE AS WET WEATHER.

&&

.SHORT TERM...RADAR AND OBS INDICATE SHOWERS ACROSS MUCH OF WRN WA
THIS MORNING. ALTHOUGH A WEAK UPPER RIDGE IS TRAVERSING THE AREA
TODAY...THE FLOW REMAINS MOIST AND SLY. BUFFER SOUNDS SHOW THE AIR
MASS BELOW 750 MB TO BE WEAKLY UNSTABLE THROUGH MIDDAY SO SHOWERS
WILL CONTINUE THROUGH THE MORNING AND PROBABLY UP THE POINT WHEN
WARM ADVECTION RAIN BEGINS.

IR SATELLITE IMAGERY AND THE COASTAL RADAR SHOW MORE STEADY RAIN
APPROACHING THE COAST. THIS WILL SPREAD INLAND LATE IN THE DAY.
BRIGHTER CLOUD TOPS APPEAR TO INDICATE SOME SPLITTING ALREADY
OCCURING WITH THE FRONT. A STRONGER PORTION IS MOVING E-NE INTO
B.C./WA AND ANOTHER PORTION PUSHING DUE E INTO OREGON. MODELS
INDICATE THE FRONT HOLDS TOGETHER ENOUGH TO PRODUCE MORE WIDESPREAD
RAINFALL THAN PAST SYSTEMS THIS WEEK BUT IT WILL BE IN A WEAKENING
STATE AS IT ARRIVES LATER TODAY/EARLY THIS EVENING.

QPF AMOUNTS ON VARIOUS MESO MODELS GENERALLY AVERAGE A HALF TO ONE
INCH LIQUID IN 12 HOURS FROM 00Z-12Z TONIGHT OVER THE MOUNTAINS.
AREAS THAT PREDOMINATELY REMAIN AS SNOW THROUGH THE EVENT COULD SEE
UP TO A FOOT OF SNOW. SNOW LEVELS ARE THE TRICKY PART OF THE
FORECAST AS CURRENT PASS TEMPERATURES ARE IN THE UPPER 20S WITH ELY
GRADIENT WHICH MAY KEEP SOME PASSES COLD FOR SOME TIME THIS EVENING.
THE MAIN SNOW LEVEL IS CURRENTLY NEAR 3500 FEET BASED ON THE KUIL
FREEZING LEVELS MINUS 1K FT. THIS WILL CLIMB AS WARM ADVECTION
PRECIPITATION OVERSPREADS THE AREA BY LATE TODAY OR THIS EVENING.
WILL GO AHEAD AND ISSUE A SNOW ADVISORY FOR 5 TO 10 INCH SNOW
AMOUNTS BUT STRESSING THE LOWER END AMOUNTS WILL FALL AT HIGHER
PASSES SUCH AS WHITE PASS AND STEVENS PASS ASSUMING SOME CHANGE OVER
TO RAIN OR FREEZING RAIN AS THE FRONT PUSHES ACROSS LATER TONIGHT.
SNOQUALMIE PASS WILL LIKELY SEE SNOW CHANGE OVER TO RAIN PRETTY
QUICKLY WITH LESS THAN A COUPLE INCHES THERE. THE FRONT WILL
ACTUALLY HELP TO MIX THE COLDER AIR OUT OF THE PASSES AND RAISE SNOW
LEVELS THERE. HOWEVER...THE MAIN FREE AIR SNOW LEVELS WILL FALL BACK
TO AROUND 3000 FEET FRIDAY MORNING AFTER LIFTING TO 4500-5000 FEET
TONIGHT. SKI RESORTS EXPOSED TO S/SW FLOW SUCH AS MOUNT BAKER AND
PARADISE SHOULD DO BEST IN THIS FLOW PATTERN IF THEY REMAIN AS ALL
SNOW WITH UP TO 10 INCHES IN THESE AREAS.

LASTLY...WINDY CONDITIONS ARE EXPECTED TO DEVELOP UP N LATER THIS
AFTERNOON THROUGH THIS EVENING. SE GRADIENTS TIGHTEN AND A MESO LOW
WILL LIKELY FORM AROUND PORT ANGELES/SEQUIM.  THIS SHOULD INDUCE
LOCALLY STRONGER SE WINDS W/ GUSTS TO 45 MPH ACROSS ADMIRALTY
INLET...THE SAN JUANS...AND EXPOSED LOCATIONS ALONG THE SHORES OF
WRN WHATCOM COUNTY. BOTH THE HRRR/NAM12 SHOW LOW END ADVISORY WINDS
AND WILL PLAN TO ISSUE AN ADVISORY THIS MORNING FOR THE LATE
AFTERNOON AND EVENING HOURS.

A MOIST ONSHORE POST-FRONTAL PATTERN DEVELOPS FRIDAY WITH WEAK
INSTABILITY IN THE LOWER LEVELS. THIS SHOULD TRANSLATE TO SHOWERS
FOR OUR AREA UNTIL THE NEXT SYSTEM ARRIVES. LATEST 06Z/12Z MODELS
BRING WARM ADVECTION RAIN TO THE COAST LATE FRIDAY NIGHT...THEN
OVERSPREADING THE ENTIRE AREA BY THE MID MORNING HOURS ON SATURDAY.
MODELS CONTINUE TO SHOW A LOT OF FLOW SO RAINFALL RATES WILL BE
HEAVY ALONG THE S/SW FACING SLOPES OF THE MOUNTAINS...ESPECIALLY THE
OLYMPICS. A TRAILING MOISTURE PLUM WILL BECOME DIRECTED AT WRN WA BY
SATURDAY EVENING AS THE FLOW TURNS MORE WLY. THIS WILL GENERATE
ADDITIONAL OROGRAPHICALLY ENHANCED RAIN ALONG THE W/SW SLOPES OF THE
OLYMPICS/CASCADES SATURDAY NIGHT INTO EARLY SUNDAY. THIS COULD CAUSE
SOME MINOR FLOODING ON PRONE RIVERS...SEE THE LATEST HYDRO
DISCUSSION BELOW FOR DETAILS. SE GRADIENTS WILL ALSO BE QUITE STRONG
WITH THE WARM FRONT. AREAS FROM ADMIRALTY INLET NWD WILL LIKELY NEED
A WIND ADVISORY AND POSSIBLY THE COAST. MERCER

.LONG TERM...NO UPDATE FROM PREVIOUS DISCUSSION...ECMWF AND GFS SHOW
STRONG ZONAL FLOW CONTINUING INTO EARLY NEXT WEEK WITH A BROAD FLAT
UPPER LEVEL RIDGE OVER THE REGION. LOTS OF FLOW THROUGH THE RIDGE
WILL KEEP THIS A GENERALLY WET AND BREEZY PERIOD THROUGH SUNDAY. THE
MAIN PROBLEM WILL REMAIN HEAVY RAIN SATURDAY NIGHT. FAIRLY STRONG
WESTERLY 850 MB FLOW WILL REMAIN 30-45KT SATURDAY NIGHT INTO SUNDAY
MORNING...THEN GRADUALLY DIMINISH OVER THE NORTH AND CENTRAL PART OF
W WA SUNDAY AFTERNOON. STRONGER W FLOW WILL CONTINUE OVER NW OREGON
AND THE SOUTHERN WA CASCADES. THERE COULD BE ANOTHER 2-3 INCHES OF
QPF OVER THE CENTRAL CASCADES 12Z SUNDAY THROUGH 12Z MONDAY WHICH
COULD BRING SOME CASCADE RIVERS CLOSE TO FLOOD STAGE.

THE BROAD FLAT RIDGE MAINTAINS STRONG SOMEWHAT MOIST W FLOW ALOFT
OVER THE AREA MONDAY AND TUESDAY...BUT THE AIR MASS IS DRIER FOR
MUCH LESS RAIN. GFS/ECMWF BOTH BRING AN UPPER LEVEL SHORTWAVE TROUGH
ACROSS THE AREA ON WEDNESDAY...THEN DEVELOP COOL DRY N FLOW ALOFT
BEHIND IT FOR THURSDAY. WE WILL SEE IF THIS MODEL AGREEMENT HOLDS.
KAM

&&

.HYDROLOGY...NO UPDATE FROM PREVIOUS DISCUSSION...RIVER FLOODING IS
NOT EXPECTED THROUGH FRIDAY NIGHT. A MOIST WESTERLY FLOW PATTERN
WILL DEVELOP SATURDAY AND CONTINUE THROUGH SUNDAY NIGHT WITH HEAVY
RAIN AT TIMES IN THE MOUNTAINS. A STRONG WARM FRONT WILL CROSS THE
AREA SATURDAY WITH STRONG S FLOW OVER THE OLYMPICS BECOMING W BY
LATE AFTERNOON. THE STRONG W FLOW WILL REACH THE CASCADES SATURDAY
NIGHT. 2-3 INCHES OF RAIN ARE EXPECTED OVER THE OLYMPICS AND PARTS
OF THE CASCADES DURING THE 24 HOUR PERIOD FROM 12Z SATURDAY THROUGH
12Z SUNDAY. THIS COULD CAUSE ANOTHER ROUND OF FLOODING ON THE
SKOKOMISH RIVER AND PRIME SOME OF THE CASCADE RIVERS.

LOW LEVEL W FLOW ALOFT OVER W WA WILL DIMINISH SUNDAY AND SUNDAY
NIGHT AS THE CORE OF STRONGEST WINDS SLIDES DOWN OVER NW OREGON AND
THE SOUTHERN WA CASCADES. STILL...ANOTHER 2-3 INCHES OF RAIN COULD
FALL OVER THE CENTRAL CASCADES BETWEEN 12Z SUNDAY AND 12Z MONDAY.
THIS ADDED RAINFALL COULD PUSH SOME OF THE MORE FLOOD PRONE CASCADE
RIVERS CLOSE TO FLOOD STAGE. KAM

&&

.AVIATION...A STRONG PACIFIC FRONTAL SYSTEM OVER THE OFFSHORE WATERS
WILL MOVE ACROSS THE AREA TONIGHT. SOUTHWESTERLY FLOW ALOFT WILL
INCREASE AND BECOMING STRONG THIS EVENING THEN BECOMING MODERATE ON
FRIDAY. THE AIR MASS IS MOIST AND STABLE...IT WILL BECOME SOMEWHAT
UNSTABLE LATE TONIGHT AND FRIDAY.

AT 1630Z A STRONG FRONT AROUND 130W IS MOVING EAST. IT WILL PUSH
ACROSS THE AREA REACHING THE INTERIOR VALLEYS JUST AFTER 08Z FRIDAY
THEN EAST OF THE CASCADES BY 12Z. PRESSURE GRADIENTS ARE
INCREASINGLY SOUTHEASTERLY IN ADVANCE OF THE FRONT...SO DESPITE RAIN
BANDS OFFSHORE MOVING INLAND...CEILINGS WILL BECOME PREDOMINATELY
VFR. EXPECT CEILINGS AND VISIBILITIES TO DETERIORATE TO MVFR ALONG
THE COAST MIDDAY AND IN THE INTERIOR SHORTLY AFTER 00Z THIS EVENING
AS PRECIPITATION DEVELOPS AND GRADUALLY INCREASES WITH THE APPROACH
OF THE FRONT.

THERE COULD BE A SHORT PERIOD OF LOW LEVEL WIND SHEAR IN THE
INTERIOR FROM ABOUT KPAE SOUTHWARD FOR A FEW HOURS AHEAD OF THE
FRONT AS WINDS AT 2000 FT INCREASE TO SSW 40KT AND SURFACE WINDS
REMAIN SELY.

POST FRONTAL ONSHORE FLOW WITH SCATTERED SHOWERS ARE EXPECTED BEHIND
THE FRONT LATE TONIGHT AND FRIDAY WITH MVFR CONDITIONS AND SOME
CLEARING AT TIMES IN THE LEE OF THE OLYMPICS. ISOLATED THUNDERSTORMS
ARE NOT OUT OF THE QUESTION ALONG THE COAST ON FRIDAY AS COLD AIR
ALOFT ARRIVES WITH AN UPPER LEVEL TROUGH. ALBRECHT

KSEA...EXPECT BKN-OVC040-050 TODAY. PERIODS OF -RA WILL DEVELOP THIS
AFTERNOON. CEILINGS WILL GRADUALLY LOWER TO MVFR THIS EVENING WITH
CIGS BOTTOMING OUT AROUND 015 A COUPLE HOURS AHEAD OF FRONTAL
PASSAGE 08Z-10Z FRIDAY. EXPECT SE WIND 5 KT TO INCREASE TO 9-11 KT
THIS EVENING THEN SHIFT TO S 10-14 KT BEHIND THE FRONT 08Z-10Z.
THERE WILL BE A COUPLE HOURS OF WIND 18035-40KT AT FL020 AHEAD OF
THE INCOMING FRONT ABOUT 06Z-08Z TIME PERIOD. ALBRECHT

&&

.MARINE...A FRONT ASSOCIATED WITH A 968 MB LOW WELL WEST OF HAIDA
GWAII WILL MOVE THROUGH THE OFFSHORE WATERS TODAY...THEN INLAND
TONIGHT. A PERIOD OF GALE FORCE WINDS CAN BE EXPECTED OVER THE
COASTAL WATERS BEGINNING MIDDAY TODAY THROUGH THIS EVENING WITH
SMALL CRAFT ADVISORY CONDITIONS FOR THE STRAIT...NORTHERN INLAND
WATERS...AND ADMIRALTY INLET. GALE FORCE WINDS ARE NOW EXPECTED AT
THE EAST ENTRANCE TO THE STRAIT OF JUAN DE FUCA THIS AFTERNOON AND
TONIGHT AS A MESOSCALE LOW DEVELOPS TO THE NORTHEAST OF THE
OLYMPICS.

EXPECT MODERATE TO STRONG ONSHORE FLOW BEHIND THE FRONT AND WITH A
SURFACE TROUGH AS IT MOVES ACROSS THE AREA ON FRIDAY. SMALL CRAFT
ADVISORY CONDITIONS WILL CONTINUE OVER THE COASTAL WATERS AND
POSSIBLY SOME OF THE INTERIOR ZONES. ISOLATED THUNDERSTORMS CANNOT
BE RULED OUT OVER THE COASTAL WATERS ON FRIDAY IN A RATHER UNSTABLE
AIR MASS.

30-45 FOOT WAVES OVER A LARGE AREA OF THE NORTH CENTRAL PACIFIC WILL
DECAY TO A LONG PERIOD 22-23 FT SWELL THAT WILL REACH THE COAST
FRIDAY AFTERNOON AND CONTINUE TO PUSH ONSHORE THROUGH SATURDAY.
TIDAL ANOMALIES ALONG THE COAST ARE JUST OVER 1 FOOT ABOVE NORMAL
AND HIGH TIDE OCCURS SATURDAY MORNING. IF SWELL REMAINS HIGH INTO
SATURDAY MORNING AS CURRENTLY EXPECTED...SOME COASTAL FLOODING IS
POSSIBLE. A COASTAL FLOOD WATCH MAY BE REQUIRED FOR PORTIONS OF THE
COAST FOR THE SATURDAY MORNING HIGH TIDE.

ANOTHER STRONG FRONT WILL ARRIVE ON SATURDAY WITH GALE
FORCE WINDS ONCE AGAIN LIKELY OVER THE COASTAL WATERS...THE NORTHERN
INLAND WATERS...AND THE STRAIT ENTRANCES. ALBRECHT

&&

.SEW WATCHES/WARNINGS/ADVISORIES...
WA...DELAYED
PZ...GALE WARNING THROUGH TONIGHT COASTAL WATERS AND EAST ENTRANCE.
     SMALL CRAFT ADVISORY ALL REMAINING WATERS.
     SMALL CRAFT ADVISORY FOR ROUGH GRAYS HARBOR BAR TONIGHT THROUGH
     FRIDAY.

&&

$$

YOU CAN SEE AN ILLUSTRATED VERSION OF THIS FORECAST DISCUSSION AT
WWW.WEATHER.GOV/SEATTLE/GAFD/LATEST_WEBAFD.HTML












000
FXUS66 KSEW 181712
AFDSEW

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SEATTLE WA
900 AM PST THU DEC 18 2014

.SYNOPSIS...AN APPROACHING FRONTAL SYSTEM WILL BRING A CHANCE OF
RAIN TODAY...FOLLOWED BY MORE CONTINUOUS RAIN TONIGHT AS THE COLD
FRONT MOVES INLAND. AN UPPER LEVEL TROUGH WILL BRING SCATTERED
SHOWERS ON FRIDAY. STRONG MOIST WEST FLOW ALOFT OVER THE NORTHEAST
PACIFIC WILL BRING A WINDY AND RAINY PATTERN THIS WEEKEND. A BROAD
UPPER LEVEL RIDGE WILL REMAIN OVER THE REGION EARLY NEXT WEEK FOR
NOT QUITE AS WET WEATHER.

&&

.SHORT TERM...RADAR AND OBS INDICATE SHOWERS ACROSS MUCH OF WRN WA
THIS MORNING. ALTHOUGH A WEAK UPPER RIDGE IS TRAVERSING THE AREA
TODAY...THE FLOW REMAINS MOIST AND SLY. BUFFER SOUNDS SHOW THE AIR
MASS BELOW 750 MB TO BE WEAKLY UNSTABLE THROUGH MIDDAY SO SHOWERS
WILL CONTINUE THROUGH THE MORNING AND PROBABLY UP THE POINT WHEN
WARM ADVECTION RAIN BEGINS.

IR SATELLITE IMAGERY AND THE COASTAL RADAR SHOW MORE STEADY RAIN
APPROACHING THE COAST. THIS WILL SPREAD INLAND LATE IN THE DAY.
BRIGHTER CLOUD TOPS APPEAR TO INDICATE SOME SPLITTING ALREADY
OCCURING WITH THE FRONT. A STRONGER PORTION IS MOVING E-NE INTO
B.C./WA AND ANOTHER PORTION PUSHING DUE E INTO OREGON. MODELS
INDICATE THE FRONT HOLDS TOGETHER ENOUGH TO PRODUCE MORE WIDESPREAD
RAINFALL THAN PAST SYSTEMS THIS WEEK BUT IT WILL BE IN A WEAKENING
STATE AS IT ARRIVES LATER TODAY/EARLY THIS EVENING.

QPF AMOUNTS ON VARIOUS MESO MODELS GENERALLY AVERAGE A HALF TO ONE
INCH LIQUID IN 12 HOURS FROM 00Z-12Z TONIGHT OVER THE MOUNTAINS.
AREAS THAT PREDOMINATELY REMAIN AS SNOW THROUGH THE EVENT COULD SEE
UP TO A FOOT OF SNOW. SNOW LEVELS ARE THE TRICKY PART OF THE
FORECAST AS CURRENT PASS TEMPERATURES ARE IN THE UPPER 20S WITH ELY
GRADIENT WHICH MAY KEEP SOME PASSES COLD FOR SOME TIME THIS EVENING.
THE MAIN SNOW LEVEL IS CURRENTLY NEAR 3500 FEET BASED ON THE KUIL
FREEZING LEVELS MINUS 1K FT. THIS WILL CLIMB AS WARM ADVECTION
PRECIPITATION OVERSPREADS THE AREA BY LATE TODAY OR THIS EVENING.
WILL GO AHEAD AND ISSUE A SNOW ADVISORY FOR 5 TO 10 INCH SNOW
AMOUNTS BUT STRESSING THE LOWER END AMOUNTS WILL FALL AT HIGHER
PASSES SUCH AS WHITE PASS AND STEVENS PASS ASSUMING SOME CHANGE OVER
TO RAIN OR FREEZING RAIN AS THE FRONT PUSHES ACROSS LATER TONIGHT.
SNOQUALMIE PASS WILL LIKELY SEE SNOW CHANGE OVER TO RAIN PRETTY
QUICKLY WITH LESS THAN A COUPLE INCHES THERE. THE FRONT WILL
ACTUALLY HELP TO MIX THE COLDER AIR OUT OF THE PASSES AND RAISE SNOW
LEVELS THERE. HOWEVER...THE MAIN FREE AIR SNOW LEVELS WILL FALL BACK
TO AROUND 3000 FEET FRIDAY MORNING AFTER LIFTING TO 4500-5000 FEET
TONIGHT. SKI RESORTS EXPOSED TO S/SW FLOW SUCH AS MOUNT BAKER AND
PARADISE SHOULD DO BEST IN THIS FLOW PATTERN IF THEY REMAIN AS ALL
SNOW WITH UP TO 10 INCHES IN THESE AREAS.

LASTLY...WINDY CONDITIONS ARE EXPECTED TO DEVELOP UP N LATER THIS
AFTERNOON THROUGH THIS EVENING. SE GRADIENTS TIGHTEN AND A MESO LOW
WILL LIKELY FORM AROUND PORT ANGELES/SEQUIM.  THIS SHOULD INDUCE
LOCALLY STRONGER SE WINDS W/ GUSTS TO 45 MPH ACROSS ADMIRALTY
INLET...THE SAN JUANS...AND EXPOSED LOCATIONS ALONG THE SHORES OF
WRN WHATCOM COUNTY. BOTH THE HRRR/NAM12 SHOW LOW END ADVISORY WINDS
AND WILL PLAN TO ISSUE AN ADVISORY THIS MORNING FOR THE LATE
AFTERNOON AND EVENING HOURS.

A MOIST ONSHORE POST-FRONTAL PATTERN DEVELOPS FRIDAY WITH WEAK
INSTABILITY IN THE LOWER LEVELS. THIS SHOULD TRANSLATE TO SHOWERS
FOR OUR AREA UNTIL THE NEXT SYSTEM ARRIVES. LATEST 06Z/12Z MODELS
BRING WARM ADVECTION RAIN TO THE COAST LATE FRIDAY NIGHT...THEN
OVERSPREADING THE ENTIRE AREA BY THE MID MORNING HOURS ON SATURDAY.
MODELS CONTINUE TO SHOW A LOT OF FLOW SO RAINFALL RATES WILL BE
HEAVY ALONG THE S/SW FACING SLOPES OF THE MOUNTAINS...ESPECIALLY THE
OLYMPICS. A TRAILING MOISTURE PLUM WILL BECOME DIRECTED AT WRN WA BY
SATURDAY EVENING AS THE FLOW TURNS MORE WLY. THIS WILL GENERATE
ADDITIONAL OROGRAPHICALLY ENHANCED RAIN ALONG THE W/SW SLOPES OF THE
OLYMPICS/CASCADES SATURDAY NIGHT INTO EARLY SUNDAY. THIS COULD CAUSE
SOME MINOR FLOODING ON PRONE RIVERS...SEE THE LATEST HYDRO
DISCUSSION BELOW FOR DETAILS. SE GRADIENTS WILL ALSO BE QUITE STRONG
WITH THE WARM FRONT. AREAS FROM ADMIRALTY INLET NWD WILL LIKELY NEED
A WIND ADVISORY AND POSSIBLY THE COAST. MERCER

.LONG TERM...NO UPDATE FROM PREVIOUS DISCUSSION...ECMWF AND GFS SHOW
STRONG ZONAL FLOW CONTINUING INTO EARLY NEXT WEEK WITH A BROAD FLAT
UPPER LEVEL RIDGE OVER THE REGION. LOTS OF FLOW THROUGH THE RIDGE
WILL KEEP THIS A GENERALLY WET AND BREEZY PERIOD THROUGH SUNDAY. THE
MAIN PROBLEM WILL REMAIN HEAVY RAIN SATURDAY NIGHT. FAIRLY STRONG
WESTERLY 850 MB FLOW WILL REMAIN 30-45KT SATURDAY NIGHT INTO SUNDAY
MORNING...THEN GRADUALLY DIMINISH OVER THE NORTH AND CENTRAL PART OF
W WA SUNDAY AFTERNOON. STRONGER W FLOW WILL CONTINUE OVER NW OREGON
AND THE SOUTHERN WA CASCADES. THERE COULD BE ANOTHER 2-3 INCHES OF
QPF OVER THE CENTRAL CASCADES 12Z SUNDAY THROUGH 12Z MONDAY WHICH
COULD BRING SOME CASCADE RIVERS CLOSE TO FLOOD STAGE.

THE BROAD FLAT RIDGE MAINTAINS STRONG SOMEWHAT MOIST W FLOW ALOFT
OVER THE AREA MONDAY AND TUESDAY...BUT THE AIR MASS IS DRIER FOR
MUCH LESS RAIN. GFS/ECMWF BOTH BRING AN UPPER LEVEL SHORTWAVE TROUGH
ACROSS THE AREA ON WEDNESDAY...THEN DEVELOP COOL DRY N FLOW ALOFT
BEHIND IT FOR THURSDAY. WE WILL SEE IF THIS MODEL AGREEMENT HOLDS.
KAM

&&

.HYDROLOGY...NO UPDATE FROM PREVIOUS DISCUSSION...RIVER FLOODING IS
NOT EXPECTED THROUGH FRIDAY NIGHT. A MOIST WESTERLY FLOW PATTERN
WILL DEVELOP SATURDAY AND CONTINUE THROUGH SUNDAY NIGHT WITH HEAVY
RAIN AT TIMES IN THE MOUNTAINS. A STRONG WARM FRONT WILL CROSS THE
AREA SATURDAY WITH STRONG S FLOW OVER THE OLYMPICS BECOMING W BY
LATE AFTERNOON. THE STRONG W FLOW WILL REACH THE CASCADES SATURDAY
NIGHT. 2-3 INCHES OF RAIN ARE EXPECTED OVER THE OLYMPICS AND PARTS
OF THE CASCADES DURING THE 24 HOUR PERIOD FROM 12Z SATURDAY THROUGH
12Z SUNDAY. THIS COULD CAUSE ANOTHER ROUND OF FLOODING ON THE
SKOKOMISH RIVER AND PRIME SOME OF THE CASCADE RIVERS.

LOW LEVEL W FLOW ALOFT OVER W WA WILL DIMINISH SUNDAY AND SUNDAY
NIGHT AS THE CORE OF STRONGEST WINDS SLIDES DOWN OVER NW OREGON AND
THE SOUTHERN WA CASCADES. STILL...ANOTHER 2-3 INCHES OF RAIN COULD
FALL OVER THE CENTRAL CASCADES BETWEEN 12Z SUNDAY AND 12Z MONDAY.
THIS ADDED RAINFALL COULD PUSH SOME OF THE MORE FLOOD PRONE CASCADE
RIVERS CLOSE TO FLOOD STAGE. KAM

&&

.AVIATION...A STRONG PACIFIC FRONTAL SYSTEM OVER THE OFFSHORE WATERS
WILL MOVE ACROSS THE AREA TONIGHT. SOUTHWESTERLY FLOW ALOFT WILL
INCREASE AND BECOMING STRONG THIS EVENING THEN BECOMING MODERATE ON
FRIDAY. THE AIR MASS IS MOIST AND STABLE...IT WILL BECOME SOMEWHAT
UNSTABLE LATE TONIGHT AND FRIDAY.

AT 1630Z A STRONG FRONT AROUND 130W IS MOVING EAST. IT WILL PUSH
ACROSS THE AREA REACHING THE INTERIOR VALLEYS JUST AFTER 08Z FRIDAY
THEN EAST OF THE CASCADES BY 12Z. PRESSURE GRADIENTS ARE
INCREASINGLY SOUTHEASTERLY IN ADVANCE OF THE FRONT...SO DESPITE RAIN
BANDS OFFSHORE MOVING INLAND...CEILINGS WILL BECOME PREDOMINATELY
VFR. EXPECT CEILINGS AND VISIBILITIES TO DETERIORATE TO MVFR ALONG
THE COAST MIDDAY AND IN THE INTERIOR SHORTLY AFTER 00Z THIS EVENING
AS PRECIPITATION DEVELOPS AND GRADUALLY INCREASES WITH THE APPROACH
OF THE FRONT.

THERE COULD BE A SHORT PERIOD OF LOW LEVEL WIND SHEAR IN THE
INTERIOR FROM ABOUT KPAE SOUTHWARD FOR A FEW HOURS AHEAD OF THE
FRONT AS WINDS AT 2000 FT INCREASE TO SSW 40KT AND SURFACE WINDS
REMAIN SELY.

POST FRONTAL ONSHORE FLOW WITH SCATTERED SHOWERS ARE EXPECTED BEHIND
THE FRONT LATE TONIGHT AND FRIDAY WITH MVFR CONDITIONS AND SOME
CLEARING AT TIMES IN THE LEE OF THE OLYMPICS. ISOLATED THUNDERSTORMS
ARE NOT OUT OF THE QUESTION ALONG THE COAST ON FRIDAY AS COLD AIR
ALOFT ARRIVES WITH AN UPPER LEVEL TROUGH. ALBRECHT

KSEA...EXPECT BKN-OVC040-050 TODAY. PERIODS OF -RA WILL DEVELOP THIS
AFTERNOON. CEILINGS WILL GRADUALLY LOWER TO MVFR THIS EVENING WITH
CIGS BOTTOMING OUT AROUND 015 A COUPLE HOURS AHEAD OF FRONTAL
PASSAGE 08Z-10Z FRIDAY. EXPECT SE WIND 5 KT TO INCREASE TO 9-11 KT
THIS EVENING THEN SHIFT TO S 10-14 KT BEHIND THE FRONT 08Z-10Z.
THERE WILL BE A COUPLE HOURS OF WIND 18035-40KT AT FL020 AHEAD OF
THE INCOMING FRONT ABOUT 06Z-08Z TIME PERIOD. ALBRECHT

&&

.MARINE...A FRONT ASSOCIATED WITH A 968 MB LOW WELL WEST OF HAIDA
GWAII WILL MOVE THROUGH THE OFFSHORE WATERS TODAY...THEN INLAND
TONIGHT. A PERIOD OF GALE FORCE WINDS CAN BE EXPECTED OVER THE
COASTAL WATERS BEGINNING MIDDAY TODAY THROUGH THIS EVENING WITH
SMALL CRAFT ADVISORY CONDITIONS FOR THE STRAIT...NORTHERN INLAND
WATERS...AND ADMIRALTY INLET. GALE FORCE WINDS ARE NOW EXPECTED AT
THE EAST ENTRANCE TO THE STRAIT OF JUAN DE FUCA THIS AFTERNOON AND
TONIGHT AS A MESOSCALE LOW DEVELOPS TO THE NORTHEAST OF THE
OLYMPICS.

EXPECT MODERATE TO STRONG ONSHORE FLOW BEHIND THE FRONT AND WITH A
SURFACE TROUGH AS IT MOVES ACROSS THE AREA ON FRIDAY. SMALL CRAFT
ADVISORY CONDITIONS WILL CONTINUE OVER THE COASTAL WATERS AND
POSSIBLY SOME OF THE INTERIOR ZONES. ISOLATED THUNDERSTORMS CANNOT
BE RULED OUT OVER THE COASTAL WATERS ON FRIDAY IN A RATHER UNSTABLE
AIR MASS.

30-45 FOOT WAVES OVER A LARGE AREA OF THE NORTH CENTRAL PACIFIC WILL
DECAY TO A LONG PERIOD 22-23 FT SWELL THAT WILL REACH THE COAST
FRIDAY AFTERNOON AND CONTINUE TO PUSH ONSHORE THROUGH SATURDAY.
TIDAL ANOMALIES ALONG THE COAST ARE JUST OVER 1 FOOT ABOVE NORMAL
AND HIGH TIDE OCCURS SATURDAY MORNING. IF SWELL REMAINS HIGH INTO
SATURDAY MORNING AS CURRENTLY EXPECTED...SOME COASTAL FLOODING IS
POSSIBLE. A COASTAL FLOOD WATCH MAY BE REQUIRED FOR PORTIONS OF THE
COAST FOR THE SATURDAY MORNING HIGH TIDE.

ANOTHER STRONG FRONT WILL ARRIVE ON SATURDAY WITH GALE
FORCE WINDS ONCE AGAIN LIKELY OVER THE COASTAL WATERS...THE NORTHERN
INLAND WATERS...AND THE STRAIT ENTRANCES. ALBRECHT

&&

.SEW WATCHES/WARNINGS/ADVISORIES...
WA...DELAYED
PZ...GALE WARNING THROUGH TONIGHT COASTAL WATERS AND EAST ENTRANCE.
     SMALL CRAFT ADVISORY ALL REMAINING WATERS.
     SMALL CRAFT ADVISORY FOR ROUGH GRAYS HARBOR BAR TONIGHT THROUGH
     FRIDAY.

&&

$$

YOU CAN SEE AN ILLUSTRATED VERSION OF THIS FORECAST DISCUSSION AT
WWW.WEATHER.GOV/SEATTLE/GAFD/LATEST_WEBAFD.HTML













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