Area Forecast Discussion
Issued by NWS Seattle/Tacoma, WA

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521
FXUS66 KSEW 051718
AFDSEW

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SEATTLE WA
930 AM PST FRI FEB 5 2016

.SYNOPSIS...A FRONTAL SYSTEM WILL MOVE THROUGH LATER THIS
AFTERNOON AND EARLY THIS EVENING FOR RAINY AND WINDY WEATHER.
SHOWERS WILL LINGER SATURDAY. A STRONG UPPER RIDGE SHOULD BRING
DRY MILD WEATHER SUNDAY THROUGH WEDNESDAY. THE NEXT FRONT WILL
PROBABLY MOVE INTO THE REGION WEDNESDAY NIGHT OR THURSDAY.

&&

.SHORT TERM...A STRONG PAC FRONTAL SYSTEM WILL MOVE INLAND TODAY FOR
RAIN AND WINDY WEATHER. THE WARM FRONT IS CLIPPING THE COAST AND
NORTH INTERIOR THIS MORNING. RAIN WILL SPREAD INLAND THIS AFTERNOON
AND EVENING WITH THE COLD FRONT. FROPA IS BETWEEN 00-03Z IN THE
INTERIOR. STRONG ONSHORE FLOW WILL DEVELOP BEHIND THE FRONT TONIGHT
AND THE TRAILING UPPER TROUGH WILL MAINTAIN SHOWERS. THE SHOWERS
WILL DECREASE EARLY SATURDAY MORNING AS THE TROUGH MOVES EAST OF THE
CREST AND ONSHORE FLOW WEAKENS. MODELS SHOW UP TO 1 INCH OF RAIN ON
THE COAST WITH 1-3 INCHES IN THE OLYMPICS AND NORTH CASCADES. THE
INTERIOR WILL SEE AROUND 0.25-0.50 INCHES. SNOW LEVELS ARE STARTING
HIGH...AROUND 6000 FT...BUT WILL DROP TO AROUND 3000 FT BEHIND THE
COLD FRONT TONIGHT. A WINTER WEATHER ADVISORY REMAINS IN EFFECT FOR
THE WEST SLOPES OF THE CASCADES WITH SNOW SHOWERS AT THE PASSES TONIGHT.

HIGH WIND IS STILL A POSSIBILITY IN THE SAN JUANS AND WESTERN
WHATCOM AHEAD AND RIGHT BEHIND THE COLD FRONT TODAY. THE HIGH WIND
WARNING REMAINS IN EFFECT.

SATURDAY WILL BE A QUIETER DAY. THERE WILL BE A FEW LINGERING
SHOWERS IN THE CASCADES DURING THE MORNING...AS MENTIONED
ABOVE...OTHERWISE A RIDGE WILL START TO MOVE INLAND AND THE FLOW
WILL TURN OFFSHORE. EXPECT HIGHS NEAR 50 DEGREES.

THE RIDGE WILL FLATTEN A BIT ON SUNDAY WHILE A WARM FRONT MOVES INTO
SOUTHERN BRITISH COLUMBIA. THE NORTH COAST AND NORTH CASCADES MAY
SEE LIGHT RAIN BUT THE REST OF THE CWA LOOKS DRY. THE AIR MASS
WILL REMAIN MILD WITH HIGHS IN THE 50S. 33

.LONG TERM...PREVIOUS DISCUSSION...EXTENDED MODELS IN GOOD AGREEMENT
WITH THE UPPER LEVEL RIDGE OVER WESTERN WASHINGTON MONDAY AND
TUESDAY WITH 500 MB HEIGHTS 580 DM PLUS THROUGH TUESDAY MORNING
BEFORE THE RIDGE STARTS TO SHIFT EAST. LOW LEVEL OFFSHORE FLOW
REMAIN INTACT RESULTING IN VERY WARM TEMPERATURES FOR THIS TIME OF
YEAR. THE WARMEST LOCATIONS...IN THIS PATTERN ALONG THE COAST...WILL
PUSH 60 DEGREES BOTH DAYS WITH MANY OTHER LOCATIONS IN THE INTERIOR
GETTING CLOSE TO 60. 60 DEGREES IS THE NORMAL HIGH FOR SEATTLE IN
THE MIDDLE OF APRIL. UPPER LEVEL RIDGE SLOWLY DRIFTING EAST TUESDAY
NIGHT AND WEDNESDAY FOR A LITTLE BIT OF COOLING IN THE HIGHS ON
WEDNESDAY. BY LATE WEDNESDAY NIGHT AND THURSDAY THE RIDGE IS FAR
ENOUGH TO THE EAST TO ALLOW A FRONT TO MOVE INTO THE AREA. BOTH THE
GFS AND ECMWF ARE A LITTLE FASTER WITH THE FRONT THAN PREVIOUS MODEL
RUNS. ADDED A CHANCE OF RAIN TO THE WEDNESDAY NIGHT TO GO ALONG WITH
THE CHANCE OF RAIN ON THURSDAY. FELTON

&&

.HYDROLOGY...FLOODING IS STILL POSSIBLE ON THE EXCEPTIONALLY FLOOD-
PRONE SKOKOMISH RIVER TONIGHT. OTHERWISE RIVER FLOODING IS NOT
EXPECTED THE NEXT 7 DAYS.

THE LATEST MODEL RUNS STILL SHOW 1 TO 3 INCHES OF PRECIPITATION OVER
THE OLYMPIC MOUNTAINS BETWEEN 18Z TODAY AND 06Z SATURDAY. SNOW
LEVELS COULD GET AS HIGH AS 7000 FEET AHEAD OF THE FRONT LATER
TODAY IN THE OLYMPICS. THE COMBINATION OF HIGH SNOW LEVELS AND A
QUICK BURST OF HEAVY RAIN COULD DRIVE THE SKOKOMISH RIVER ABOVE
FLOOD STAGE...ESPECIALLY CONSIDERING THE SATURATED GROUND
CONDITIONS AND THE FACT THAT THE RIVER CONTINUES TO HOLD STEADY JUST
A LITTLE OVER A FOOT BELOW FLOOD STAGE. THE FLOOD WATCH WILL
CONTINUE THIS MORNING FOR THE RIVER.

IN ADDITION...THE USGS LANDSLIDE HAZARDS DATA SUGGEST THAT THE
RAINFALL TODAY COULD BE ENOUGH TO TRIGGER LANDSLIDES. A SPECIAL
WEATHER STATEMENT HAS BEEN ISSUED TO ADDRESS THIS POSSIBILITY THIS
AFTERNOON. FELTON

&&

.AVIATION...STRONG SOUTHWEST FLOW ALOFT OVER WESTERN WASHINGTON THIS
MORNING AHEAD OF A VIGOROUS FRONTAL SYSTEM OVER THE OFFSHORE WATERS
OF THE PACIFIC NORTHWEST. THE FRONT WILL MOVE THROUGH THE FORECAST
AREA LATE THIS AFTERNOON AND THIS EVENING...BRINGING WIDESPREAD
MODERATE TO LOCALLY HEAVY PRECIPITATION AND STRONGER SOUTHERLY
WINDS. MODERATELY STRONG MOIST WESTERLY FLOW WILL FOLLOW THE FRONT
TONIGHT AND SATURDAY MORNING.

KSEA...SOUTHEAST WIND 4-12 KT...BECOMING SOUTH THIS AFTERNOON AND
RISING TO 12-20 KT GUSTING 30 KT. COLD FRONT PASSAGE WILL PROBABLY
OCCUR AROUND 7 PM. RAIN SHOULD BEGIN AROUND 4 PM WITH CONDITIONS
DETERIORATING QUICKLY TO MVFR. MCDONNAL

&&

.MARINE...A VIGOROUS COLD FRONT WILL MOVE THROUGH THE COASTAL WATERS
THIS AFTERNOON AND INLAND EARLY THIS EVENING. IT SHOULD BRING SOUTH
TO SOUTHEAST GALES TO THE COASTAL WATERS... ENTRANCES TO THE STRAIT
OF JUAN DE FUCA...AND NORTHERN INLAND WATERS WITH SMALL CRAFT
ADVISORY WINDS ELSEWHERE. STRONG ONSHORE FLOW WILL FOLLOW THE FRONT
TONIGHT...AND GALES ARE LIKELY IN THE CENTRAL STRAIT OF JUAN DE FUCA
AND EAST ENTRANCE STRAIT.

A RIDGE OF HIGH PRESSURE WILL BUILD OVER THE WATERS ON
SATURDAY...AND WINDS WILL EASE. THE UPPER RIDGE WILL SHIFT EAST OF
THE CASCADES SUNDAY...RESULTING IN OFFSHORE FLOW THAT WILL CONTINUE
THROUGH TUESDAY.

ANOTHER ROUND OF SWELL IS EXPECTED TODAY...BUT THE HIGHEST WAVES
COINCIDE WITH LOW TIDE THIS AFTERNOON...SO WILL NOT ISSUE HIGHLIGHTS
FOR THE BEACH EROSION ISSUES AT OCEAN SHORES AND WESTPORT. BEYOND
TODAY...LOOKS LIKE A TAMER WEEKEND AND EARLY WEEK AHEAD IN TERMS OF
OCEAN SWELL. MCDONNAL

&&

.SEW WATCHES/WARNINGS/ADVISORIES...
WA...WINTER WEATHER ADVISORY FROM 6 PM THIS EVENING TO 4 AM PST
     SATURDAY FOR CASCADES OF PIERCE AND LEWIS COUNTIES-CASCADES
     OF SNOHOMISH AND KING COUNTIES-CASCADES OF WHATCOM AND
     SKAGIT COUNTIES.

     FLOOD WATCH FROM 4 PM PST THIS AFTERNOON THROUGH SUNDAY
     AFTERNOON FOR HOOD CANAL AREA-LOWER CHEHALIS VALLEY AREA-
     OLYMPICS.

     HIGH WIND WARNING UNTIL 7 PM PST THIS EVENING FOR SAN JUAN
     COUNTY-WESTERN WHATCOM COUNTY.

     WIND ADVISORY UNTIL 7 PM PST THIS EVENING FOR ADMIRALTY INLET
     AREA-EASTERN STRAIT OF JUAN DE FUCA-WESTERN SKAGIT COUNTY.

     WIND ADVISORY UNTIL 6 PM PST THIS EVENING FOR CENTRAL COAST-
     NORTH COAST.

PZ...SMALL CRAFT ADVISORY FOR ROUGH BAR UNTIL 4 PM PST SATURDAY FOR
     GRAYS HARBOR BAR.

     SMALL CRAFT ADVISORY FROM 4 PM THIS AFTERNOON TO 6 PM PST
     SATURDAY FOR COASTAL WATERS FROM CAPE FLATTERY TO JAMES
     ISLAND 10 TO 60 NM-COASTAL WATERS FROM CAPE FLATTERY TO
     JAMES ISLAND OUT 10 NM-COASTAL WATERS FROM JAMES ISLAND TO
     POINT GRENVILLE 10 TO 60 NM-COASTAL WATERS FROM JAMES
     ISLAND TO POINT GRENVILLE OUT 10 NM-COASTAL WATERS FROM
     POINT GRENVILLE TO CAPE SHOALWATER 10 TO 60 NM-COASTAL
     WATERS FROM POINT GRENVILLE TO CAPE SHOALWATER OUT 10 NM-
     WEST ENTRANCE U.S. WATERS STRAIT OF JUAN DE FUCA.

     GALE WARNING UNTIL 4 PM PST THIS AFTERNOON FOR COASTAL WATERS
     FROM CAPE FLATTERY TO JAMES ISLAND 10 TO 60 NM-COASTAL
     WATERS FROM CAPE FLATTERY TO JAMES ISLAND OUT 10 NM-COASTAL
     WATERS FROM JAMES ISLAND TO POINT GRENVILLE 10 TO 60 NM-
     COASTAL WATERS FROM JAMES ISLAND TO POINT GRENVILLE OUT 10
     NM-COASTAL WATERS FROM POINT GRENVILLE TO CAPE SHOALWATER
     10 TO 60 NM-COASTAL WATERS FROM POINT GRENVILLE TO CAPE
     SHOALWATER OUT 10 NM-WEST ENTRANCE U.S. WATERS STRAIT OF
     JUAN DE FUCA.

     GALE WARNING UNTIL 4 AM PST SATURDAY FOR EAST ENTRANCE U.S.
     WATERS STRAIT OF JUAN DE FUCA.

     SMALL CRAFT ADVISORY FROM 6 PM THIS EVENING TO 4 AM PST SATURDAY
     FOR NORTHERN INLAND WATERS INCLUDING THE SAN JUAN ISLANDS.

     GALE WARNING UNTIL 6 PM PST THIS EVENING FOR NORTHERN INLAND
     WATERS INCLUDING THE SAN JUAN ISLANDS.

     SMALL CRAFT ADVISORY UNTIL 6 PM PST THIS EVENING FOR CENTRAL
     U.S. WATERS STRAIT OF JUAN DE FUCA.

     GALE WARNING FROM 6 PM THIS EVENING TO 4 AM PST SATURDAY FOR
     CENTRAL U.S. WATERS STRAIT OF JUAN DE FUCA.

     SMALL CRAFT ADVISORY UNTIL 4 AM PST SATURDAY FOR ADMIRALTY INLET.

     SMALL CRAFT ADVISORY FROM 4 PM THIS AFTERNOON TO 4 AM PST
     SATURDAY FOR PUGET SOUND AND HOOD CANAL.

&&

$$

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