Area Forecast Discussion
Issued by NWS Seattle/Tacoma, WA

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FXUS66 KSEW 192150
AFDSEW

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SEATTLE WA
250 PM PDT SAT APR 19 2014

.SYNOPSIS...POST FRONTAL ONSHORE FLOW WILL GIVE SHOWERS TO THE AREA
THIS EVENING. SHOWERS AND ONSHORE FLOW WILL DIMINISH OVERNIGHT AS
HIGH PRESSURE MOVES INTO THE AREA. THE NEXT APPROACHING FRONT WILL
STALL OFFSHORE ON SUNDAY WITH JUST A CHANCE OF RAIN ALONG THE COAST.
THE FRONT WILL CONTINUE TO HAVE A HARD TIME MOVING EAST SUNDAY NIGHT
INTO MONDAY BEFORE MOVING THROUGH THE AREA MONDAY NIGHT. A SERIES OF
SYSTEMS WILL GIVE COOL AND UNSETTLED CONDITIONS TO THE AREA TUESDAY
THROUGH EARLY NEXT WEEKEND.

&&

.SHORT TERM...THE COLD FRONT THAT WAS ALONG THE COAST THIS MORNING
HAS PUSHED RAPIDLY EAST ACROSS THE AREA TODAY AND IS NOW MOVING EAST
OF THE CASCADES. THE REMAINS OF A BENT BACK OCCLUSION IS NOW MOVING
INLAND ACROSS THE AREA BRINGING NUMEROUS SHOWERS AND LOCALLY BREEZY
CONDITIONS TO THE AREA. BEHIND THE BENT BACK OCCLUSION...A WEAK
SHORT WAVE RIDGE NOW SEEN NEAR 140W WILL AMPLIFY AS IT MOVES
EASTWARD. SHOWERS WILL DIMINISH AFTER MIDNIGHT AS THIS RIDGE
APPROACHES THE AREA. GALE TO NEAR GALE FORCE WESTERLY WINDS OVER THE
OFFSHORE WATERS HAS REALLY DEVELOPED A GOOD WAVE TRAIN THIS
AFTERNOON. BUOY 46036 AT 48.4N 134.9W IS REPORTING SEAS AROUND 30 FT
AT 17 SECONDS. THIS WAVES WILL DECAY TO A SWELL TRAIN OF 18 TO 20
FEET OVERNIGHT TONIGHT INTO SUNDAY AS IT PUSHES ONSHORE...AND A HIGH
SURF ADVISORY REMAINS IN EFFECT FOR THE WASHINGTON COAST. POST
FRONTAL SHOWERS WITH THE REMNANTS OF THE BENT BACK OCCLUSION AND
CONVERGENT FLOW AROUND THE OLYMPICS WILL GIVE RATHER HEAVY
PRECIPITATION AMOUNTS UNTIL ABOUT MIDNIGHT TONIGHT OVER THE NORTH
CASCADES. AREAS AROUND THE SR 530 LANDSLIDE EAST OF OSO WILL LIKELY
SEE 0.75 TO 1.25 INCHES OF RAIN THIS EVENING...AND SOME AREAS OVER
THE NORTH CASCADES COULD SEE AROUND 1.5 INCHES THROUGH MIDNIGHT
TONIGHT.

A TRANSITORY UPPER LEVEL RIDGE WILL MOVE ONSHORE EARLY SUNDAY
MORNING AND AMPLIFY AS IT MOVES EAST OF THE CASCADES SUNDAY AND
SUNDAY NIGHT. THE RIDGE WILL CONTINUE TO AMPLIFY AS IT MOVES INTO
WESTERN MONTANA EARLY MONDAY MORNING. THE AMPLIFICATION OF THE FLOW
WILL RESULT IN THE NEXT INCOMING FRONTAL SYSTEM SUNDAY INTO MONDAY
MORNING STALLING OFFSHORE AND BECOMING MORE NORTH-SOUTH ORIENTED
WITH TIME. THIS WILL LIMIT PRECIPITATION CHANCES SUNDAY THROUGH
EARLY MONDAY MORNING TO THE COASTAL ZONES. IT WILL STILL REMAIN
RATHER CLOUDY IN THE INTERIOR DURING THE PERIOD THOUGH.

AN UPPER TROUGH WILL APPROACH THE COAST MONDAY AND PUSH INLAND
MONDAY NIGHT INTO TUESDAY. DIFFLUENT SSW FLOW ALOFT AHEAD OF THIS
TROUGH AND THE OLD STATIONARY FRONTAL SYSTEM OVER THE COASTAL WATERS
WILL GIVE A CHANCE OF SHOWERS ON MONDAY...MAINLY DURING THE
AFTERNOON HOURS. THE SHOWER CHANCES WILL INCREASE INLAND MONDAY
NIGHT INTO TUESDAY WITH THE REMAINS OF THE OLD FRONT THEN THE UPPER
TROUGH. ALBRECHT

.LONG TERM...MODELS DIVERGE SOMEWHAT CONCERNING THE WEATHER ON
WEDNESDAY. THE GFS FAMILY OF SOLUTIONS GENERALLY SHOWS DIRTY RIDGING
ON WEDNESDAY FOR POSSIBLY SOME PEEKS OF SUNSHINE AND ONLY A CHANCE
OF SHOWERS...MAINLY IN THE MOUNTAINS...IN WESTERLY FLOW ALOFT. THE
PREFERRED ECMWF AND CANADIAN SOLUTIONS SHOW A WARM FRONT BRINGING
RATHER WET CONDITIONS TO THE AREA...ESPECIALLY LATER IN THE DAY ON
WEDNESDAY. MODELS ARE FAIRLY CONSISTENT IN BRINGING A SLOW MOVING
COLD FRONT THROUGH THE AREA WEDNESDAY NIGHT THROUGH THURSDAY NIGHT
OR FRIDAY FOR PERIODS OF RAIN. A TROUGHY PATTERN WILL GIVE AT LEAST
A CHANCE OF SHOWERS TO THE AREA NEXT WEEKEND. POPS THROUGH THE
EXTENDED FORECAST ARE ABOVE CLIMATOLOGICAL AVERAGE AND TEMPERATURES
WITH ALL THE CLOUDS AND PRECIPITATION WILL AVERAGE A FEW DEGREES
BELOW NORMAL FOR LATE APRIL. ALBRECHT

&&

.HYDROLOGY...RIVER FLOODING IS UNLIKELY FOR THE NEXT 7 DAYS.

THE EXCEPTION IS THE NORTH FORK OF THE STILLAGUAMISH RIVER EAST OF
THE SR 530 LANDSLIDE NEAR OSO WHERE A FLOOD WARNING REMAINS IN
EFFECT UNTIL FURTHER NOTICE. FLOODING CONTINUES FOR THIS RIVER AS A
RESULT OF WATER POOLED BEHIND THE DEBRIS DAM THAT PARTIALLY BLOCKS
THE RIVER.

AT 230 PM...THE NORTH FORK OF THE STILLAGUAMISH NEAR ARLINGTON IS AT
4.6 FT...OR 2740 CFS. THE RIVER IS EXPECTED TO RISE TO 6.5 FEET OR
6050 CFS EARLY SUNDAY MORNING BEFORE FALLING BACK TO AROUND 4.5 FEET
MONDAY AFTERNOON. THE NORTH FORK OF THE STILLAGUAMISH RIVER NEAR OSO
IS AT 216.5 FEET OR 1900 CFS THIS AFTERNOON AND IS EXPECTED TO RISE
TO 218.3 FEET OR 3500 CFS EARLY SUNDAY MORNING BEFORE FALLING LATE
SUNDAY INTO MONDAY. THE SLIDE POOL EAST OF THE LANDSLIDE IS EXPECTED
TO RISE TO AROUND 285.3 FT MIDDAY SUNDAY BEFORE FALLING BACK TO
284.3 FT MONDAY NIGHT. ALBRECHT

&&

.AVIATION...AN UPPER LEVEL TROUGH WILL CONTINUE TO MOVE THROUGH WRN
WA THIS AFTERNOON AND EVENING. THE ASSOCIATED SURFACE FRONT IS
CURRENTLY MOVING THROUGH WESTERN WA AT THE TIME OF THIS WRITING.
WEST TO SOUTHWEST FLOW ALOFT TONIGHT...BECOMING MORE SOUTHWESTERLY
SUNDAY MORNING. GENERALLY STABLE CONDITIONS. RAIN EXPECTED TO
CONTINUE BEHIND THE FRONT AS AREAS OF SHOWERS MOVE OVER WESTERN
WASHINGTON IN ITS WAKE. CIGS RANGING 2K TO 4K FT THIS
AFTERNOON...DOWN TO 500 FT IN SOME LOCATIONS UNDER SHOWERS. CIGS
EXPECTED TO LINGER IN THIS RANGE BEFORE STARTING TO SEE SOME
IMPROVEMENT STARTING SUNDAY MORNING. UPPER LEVEL RIDGING SUNDAY INTO
MONDAY WILL ALLOW CIGS TO IMPROVE THROUGHOUT THE DAY SUNDAY.

KSEA...CIGS 2-4K FT THIS AFTERNOON AND THIS EVENING...DROPPING DOWN
TO 500-1500 FT DURING SHOWERS. SOUTHERLY WINDS 10-15 W/ GUSTS UP TO
22 EXPECTED TO BECOME MORE SOUTHWESTERLY BY 6 PM PDT THIS EVENING.
RAIN CONTINUING INTO THE LATE EVENING BEFORE STARTING TO TAPER OFF.
CIGS IMPROVING TO 5-7K FT BY SUNDAY MORNING. SMR

&&

.MARINE...THE COLD FRONT HAS MOVED OUT OF COASTAL WATERS...CROSSING
WESTERN WASHINGTON. SMALL CRAFT ADVISORY WINDS REMAIN OVER ALL
WATERS BEHIND THE FRONT...TAPERING OFF BY LATE TONIGHT. HIGH
PRESSURE WILL REBUILD ON SUNDAY. A WEAKER SYSTEM WILL ARRIVE LATER
MONDAY OR MONDAY NIGHT.

A LARGE SWELL TRAIN WILL ARRIVE ALONG THE WASHINGTON COAST THIS
EVENING AND CONTINUE INTO SUNDAY. LARGE WAVES UP TO 15 FEET WILL
IMPACT THIS COAST BY THIS EVENING...BUILDING TO 16 TO 19 FEET LATER
TONIGHT INTO SUNDAY MORNING. A HIGH SURF ADVISORY REMAINS IN EFFECT
FOR THE COAST FROM THIS EVENING THROUGH SUNDAY. THIS IS A RAZOR CLAM
DIG WEEKEND FOR TWIN HARBORS...COPALIS AND MOCLIPS/MOCROCKS BEACHES.
EXTREME CAUTION SHOULD BE EXERCISED AS WAVES WILL LIKELY RACE
FURTHER UP THE BEACH THAN NORMAL.

&&

.SEW WATCHES/WARNINGS/ADVISORIES...
WA...FLOOD WARNING REMAINS IN EFFECT FOR THE NORTH FORK OF THE
      STILLAGUAMISH RIVER EAST OF THE SR 530 LANDSLIDE.
     HIGH SURF ADVISORY NORTH AND CENTRAL COAST THIS EVENING
      THROUGH SUNDAY AFTERNOON.

PZ...SMALL CRAFT ADVISORY ALL WATERS THROUGH THIS EVENING.
     SMALL CRAFT ADVISORY FOR ROUGH GRAYS HARBOR BAR TONIGHT.

&&

$$

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