Area Forecast Discussion
Issued by NWS Seattle/Tacoma, WA

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000
FXUS66 KSEW 210449
AFDSEW

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SEATTLE WA
900 PM PST THU NOV 20 2014

.SYNOPSIS...A PACIFIC STORM WILL IMPACT THE REGION ON FRIDAY AND
FRIDAY NIGHT WITH LOCALLY HEAVY RAIN AND GUSTY WINDS...ALONG WITH
DECENT SNOWFALL IN THE CASCADES FROM STEVENS PASS NORTHWARD. THE
WEATHER PATTERN WILL REMAIN WET AND UNSETTLED THIS WEEKEND WITH
ANOTHER WEATHER SYSTEM IMPACTING THE AREA ON SUNDAY. MUCH
UNCERTAINTY EXISTS IN THE FORECAST FROM MONDAY ONWARD.

&&

.SHORT TERM...SHOWERS ARE WINDING DOWN ACROSS WESTERN WA THIS
EVENING...MAINLY AFFECTING THE NORTH CASCADES. SKIES WILL REMAIN
CLOUDY OVERNIGHT WITH LOWS IN THE 40S. CURRENT FORECAST IS ON TRACK.

A STRONG PACIFIC FRONTAL SYSTEM WILL BRING RAIN...MOUNTAIN SNOW AND
LOCALLY WINDY CONDITIONS AS IT MOVE INLAND FRI AND FRI NIGHT. WIND
ADVISORIES ARE IN EFFECT FOR THE COAST...SAN JUANS AND WESTERN
WHATCOM. RAIN WILL REACH THE COAST FRI MORNING...THEN SPREAD INLAND
BY THE AFTERNOON. THE COAST MAY SEE 1-2 INCHES OF RAIN...WITH 0.5 TO
1 INCH IN THE INTERIOR. SNOW LEVELS WILL HOVER AROUND 4000 FT WITH
SNOW EXPECTED AT STEVENS PASS AND WASHINGTON PASS...WITH UP TO 6
INCHES OF SNOW POSSIBLE THROUGH FRI NIGHT. SNOQUALMIE PASS SHOULD
SEE RAIN. A WINTER WEATHER ADVISORY IS IN EFFECT FOR THE CASCADES
FROM KING COUNTY NORTH OVER 4000 FT. SHOWERS WILL TAPER DOWN LATE
FRI NIGHT AS THIS SYSTEM EXITS.

MOIST ONSHORE FLOW CONTINUES ON SAT FOR ADDITIONAL SHOWERS ACROSS
THE AREA...WITH MORE SNOW IN THE MOUNTAINS. MAY SEE A PUGET SOUND
CONVERGENCE ZONE DEVELOP SAT AFTERNOON.

ANOTHER STRONG PACIFIC FRONT WILL BRING MORE RAIN AND MOUNTAIN SNOW
ON SUNDAY. 33

.LONG TERM...PREVIOUS DISCUSSION...MONDAY THROUGH WEDNESDAY...BOTH
THE GFS AND ECMWF SHOW MOISTURE BEING TRANSPORTED TO THE PACIFIC NW
VIA THE JET STREAM...HOWEVER THE GFS HAS THE MOISTURE HITTING SW BC
FOR THE MOST PART AND US STAYING DRY...WHEREAS THE ECMWF HAS A
WETTER SOLUTION FOR US WITH THE MOISTURE HITTING US DIRECTLY.
THEREFORE MUCH UNCERTAINTY EXISTS IN THE FORECAST. THURSDAY LOOKS
DRY WITH A RIDGE BUILDING IN ON BOTH MODELS...BUT IT IS TOO EARLY TO
TELL WITH MUCH CERTAINTY. JSMITH

&&

.HYDROLOGY...RIVER FLOODING IS NOT EXPECTED THE NEXT 7 DAYS.

&&

.AVIATION...WESTERLY FLOW ALOFT WILL INCREASE TONIGHT AS A STRONG
FRONTAL SYSTEM APPROACHES THE COAST. THE AIR MASS IS MOIST AND
STABLE EXCEPT FOR ISOLATED SHOWERS NORTH PART. RAIN FROM THE
APPROACHING FRONT WILL SPREAD INLAND AROUND 15Z. FROPA ON THE COAST
SHOULD BE AROUND 00Z...AND OVER PUGET SOUND AROUND 04Z. AT THE
SURFACE STRONG GUSTY SOUTHEAST WINDS WILL DEVELOP ALONG THE COAST
AND OVER PARTS OF THE NORTH INTERIOR ON FRIDAY.

CEILINGS THIS EVENING ARE GENERALLY VFR 4K-6K FT. LOCAL FOG WITH
VISIBILITIES 1/2SM ARE POSSIBLE TONIGHT. BY FRIDAY MORNING MOST
CEILINGS WILL FALL TO MVFR 2K-3K FT IN RAIN.

KSEA...DISCUSSION ABOVE APPLIES EXCEPT FOG IS UNLIKELY TONIGHT.
WINDS SOUTHEAST 4-8 KT. RAIN AND MVFR CONDITIONS WILL PREDOMINATE ON
FRIDAY. WINDS WILL RISE TO SOUTHERLY 8-12 KT IN THE AFTERNOON. CHB

&&

.MARINE...A STRONG FRONTAL SYSTEM WILL MOVE THROUGH THE AREA FRIDAY.
MODELS SHOW GALES OVER THE COASTAL WATERS STARTING FRIDAY AFTERNOON
AND OVER THE EAST ENTRANCE AND NORTH INLAND WATERS FRIDAY AFTERNOON
AND EVENING. SMALL CRAFT ADVISORY WINDS ARE EXPECTED OVER THE REST
OF THE WATERS. FROPA ALONG THE COAST SHOULD BE AROUND 00Z...THEN
AROUND 04Z OVER PUGET SOUND. A WESTERLY PUSH BEHIND THE FRONT SHOULD
PRODUCE SMALL CRAFT ADVISORY WEST WINDS THROUGH THE STRAIT AND OVER
THE NORTHERN INLAND WATERS.

WESTERLY FLOW ALOFT OVER THE NORTHEAST PACIFIC SATURDAY THROUGH
MONDAY WILL BRING SEVERAL WEAKER SURFACE TROUGHS ACROSS THE AREA.
CONFIDENCE IN THE TIMING AND STRENGTH OF EACH OF THESE TROUGHS IS
LOW...BUT THEY COULD PRODUCE SOLID ADVISORY LEVEL WINDS AND PERHAPS
SPOTTY GALES. SWELLS IN THE 15-20 FOOT RANGE ARE FORECAST TO REACH
THE COAST SUNDAY. CHB

&&

.SEW WATCHES/WARNINGS/ADVISORIES...
WA...WINTER WEATHER ADVISORY NORTH AND NORTH CENTRAL CASCADES.
     WIND ADVISORY NORTH AND CENTRAL COAST...THE SAN JUAN
     ISLANDS...AND WESTERN WHATCOM COUNTY.
PZ...GALE WARNING COAST...EAST ENTRANCE...NORTH INLAND WATERS.
     SMALL CRAFT ADVISORY ALL REMAINING WATERS.
     SMALL CRAFT ADVISORY FOR ROUGH GRAYS HARBOR BAR.

&&

$$

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