Small Craft Advisory 682, NWS Seattle, WA

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SEATTLE WA
845 AM PDT SAT APR 9 2011

.SYNOPSIS...A WEAKENING WEATHER DISTURBANCE WILL MOVE OVER WESTERN
WASHINGTON THROUGH TONIGHT AND REMAIN OVER WESTERN WASHINGTON ON
SUNDAY. A STRONGER COLD FRONT WILL MOVE THROUGH THE AREA LATE SUNDAY
NIGHT. A COOL BLUSTERY AND SHOWERY DAY IS ON TAP IN THE WAKE OF THE
COLD FRONT MONDAY. A WET WEATHER PATTERN IS LIKELY TO DEVELOP
STARTING AROUND THE MIDDLE OF NEXT WEEK.

&&

.SHORT TERM...A WEAK UPPER RIDGE WILL SHIFT THROUGH THE REGION TODAY
BETWEEN THE DEEP UPPER TROUGH MOVING INTO THE FOUR CORNERS AND A NEW
UPPER TROF ARND 150W. A LOT OF CLOUDS MOVING THRU THE RIDGE
TODAY...THE 500MB HEIGHT ONLY RISES TO ABOUT 555DM SO THAT IS NOT
MUCH OF A RIDGE...AND THERE IS ALSO A WEAKENING SFC LOW PRES TROF
MOVG TO THE COASTAL WATERS TODAY. THIS SYSTEM IS ESSENTIALLY A
WEAKENING WARM FRONT AND IT MOVES OVER WRN WA TONIGHT AND
SUNDAY...WITH AREAS OF LIGHT RAIN DVLPG. SUNDAY LOOKS LIKE A DRIPPY
DAY FOR MOST OF WRN WA. A SFC LOW PRES SYSTEM DEEPENS ON SUNDAY AND
THE NAM HAS IT DOWN TO 1000MB AS IT REACHES VANCOUVER ISLAND LATER
SUN NIGHT...WITH THE COLD FRONT AT THE WA AND ORE COAST...THEN
SWEEPING THRU THE INTERIOR OF WRN WA BY DAYBREAK MON. MONDAY MORNING
LOOKS BLUSTERY...THE PDX-BLI GRADIENT ON THE NAM IS ARND +10MB AT
7AM MONDAY...SO THAT IS SOMETHING TO KEEP AN EYE ON. 19

.LONG TERM...BY MONDAY NIGHT SHOWERS AND GRADIENTS ARE BACKING OFF
OVER WRN WA...THE NAM HAS THE HINT OF A PSCZ PERSISTING INTO MONDAY
EVENING...BUT BY 12Z TUE WRN WA IS MOSTLY DRY. TUE OUGHT TO BE A DRY
DAY BUT ONCE AGAIN WE CAN'T GET A DECENT UPPER RIDGE BETWEEN
SYSTEMS...THE 06Z GFS ONLY HAD A VERY SHORT PERIOD OF RISING HEIGHTS
MONDAY NIGHT AND BY LATE TUE AFTERNOON HEIGHTS HAVE FALLEN OFF AGAIN
TO 546DM WITH ANOTHER WEATHER SYSTEM AT 130W. MAYBE THE 12Z GFS WILL
BUILD A BETTER TRANSITORY UPPER RIDGE FOR TUE AHEAD OF WHAT LOOKS AT
FIRST GLANCE LIKE A WET ZONAL WEATHER PATTERN SETTING FOR THE MIDDLE
OF NEXT WEEK AND BEYOND. IT IS INTERESTING THAT THE 5-WAVE CHART
ACTUALLY HAS A MORE ZONAL WEATHER PATTERN ACROSS THE NORTH PACIFIC
THIS WEEKEND THAN IT DOES AFTER THE MIDDLE OF NEXT WEEK WHEN A RIDGE
BUILDS AT THE DATELINE AND AN UPPER TROF IS IN THE NE PAC...AND WITH
TIME THE TROF RETROGRADES A LITTLE ALLOWING HEIGHTS TO RISE OVER THE
WEST COAST...CREATING A MILDER WET PATTERN FOR NEXT WEEKEND. 19

&&

.HYDROLOGY...A WARM FRONT WILL BREAK UP OVER WRN WA TONIGHT AND
SUNDAY WITH ONLY LIGHT RAIN. A STRONGER COLD FRONT WILL ARRIVE
SUNDAY NIGHT WITH THE FROPA AROUND DAYBREAK MON. LOOKS LIKE THIS
SYSTEM WILL GIVE THE OLYMPICS ON THE ORDER OF AN INCH OF RAIN...WITH
SNOW ABOVE ABOUT 4000FT. GUIDANCE BRINGS THE RIVER TO ADVISORY
LEVELS AND THE TREND FOR QPS HAS NOT BEEN TO MAKE THE SYSTEM ANY
WETTER. IF THE WRFGFS CONFIRMS DPROG/DT IS NOT ANY WETTER WILL
PROBABLY BE ABLE TO LET THE OUTLOOK EXPIRE LATER THIS AFTERNOON. 19

&&

.AVIATION...AN UPPER LEVEL RIDGE EXTENDING FROM SOUTH CENTRAL
BRITISH COLUMBIA SOUTHWESTWARD TO 35N 145W WILL SLOWLY SHIFT EAST
THROUGH TONIGHT. IN THE MEAN TIME...A WEAK FRONT FROM NORTH CENTRAL
VANCOUVER ISLAND SOUTHWARD THROUGH THE OFFSHORE WATERS WILL
DISSIPATE AS IT MOVES THROUGH THE COASTAL WATERS THIS EVENING.

WESTERN WASHINGTON IS SEEING MAINLY MID AND UPPER LEVEL CLOUDS WITH
LAYERS AROUND 070 AND 200 AS REMNANT MOISTURE FROM THE OFFSHORE
FRONT MOVES OVER THE TOP OF THE UPPER LEVEL RIDGE. A SMALL AREA OF
STRATUS WITH BASES 012-020 EXTENDS FROM SW OF KPAE THROUGH THE PUGET
SOUND AND KITSAP PENINSULA SWWD TO KTIW AND JUST N OF KTCM. THIS LOW
LEVEL MOISTURE WILL LIFT AND DISSIPATE BY 19Z BUT WILL LIKELY IMPACT
THE CENTRAL PUGET SOUND TERMINALS FOR A COUPLE HOURS UNTIL ABOUT
NOON.

THICKER LOW LEVEL MOISTURE WITH BASES 020-030 WILL MOVE ONTO THE
COAST THIS AFTERNOON AND TONIGHT AND WILL LIKELY GIVE SOME -RA AT
TIMES TONIGHT. THE NAM12 SHOWS THIS MOISTURE MAKING IT INTO THE
INTERIOR AROUND 10Z TONIGHT AND CONTINUING THROUGH MUCH OF THE DAY
SUN. THIS MOISTURE IS THE COMBINATION OF DIURNAL COOLING...REMNANTS
OF THE INCOMING FRONT...AND WARM ADVECTION AHEAD OF THE NEXT
STRONGER FRONTAL SYSTEM THAT WILL MOVE THROUGH THE AREA LATE SUN
NIGHT OR EARLY MON.

KSEA...EXPECT S TO SW WIND 7-11 KT THROUGH TONIGHT. STRATUS IN THE
VICINITY WITH BASES 012 WILL DISSIPATE BY 19Z. VFR CONDITIONS WILL
PREVAIL THROUGH TONIGHT. ALBRECHT

&&

.MARINE...A WEAK FRONT EXTENDING SOUTHWARD FROM NORTH CENTRAL
VANCOUVER ISLAND THROUGH THE OFFSHORE WATERS WILL DISSIPATE AS IT
MOVES INTO THE COASTAL WATERS THIS EVENING. A STRONGER
FRONT...ASSOCIATED WITH A DEVELOPING LOW THAT WILL DEEPEN TO 1000 MB
AS IT MOVES ONTO NORTHERN VANCOUVER ISLAND SUN NIGHT...WILL PUSH
EAST THROUGH THE COASTAL WATERS LATE SUN NIGHT AND THROUGH THE
INLAND WATERS BY EARLY MON MORNING. LATEST FORECASTS SHOW THIS FRONT
HAS THE POTENTIAL TO PRODUCE GALE FORCE WINDS IN THE COASTAL
WATERS BEGINNING SUN EVENING AND CONTINUING UNTIL THE FRONT PASSES.
THIS IS A BIT LATER THAN PREVIOUS FORECASTS INDICATED. SMALL CRAFT
ADVISORY CONDITIONS ARE EXPECTED IN MOST INLAND WATERS SUN NIGHT AND
EARLY MON AS THE FRONT PASSES. WILL TAKE A GOOD LOOK AT THE REST OF
THE ARRIVING GUIDANCE BEFORE DELAYING THE GALE WATCH FOR SUN INTO
SUN NIGHT FOR THE COAST AND WEST ENTRANCE.

MODERATE TO STRONG POST FRONTAL ONSHORE FLOW MON WILL GRADUALLY
SUBSIDE LATE MON AFTERNOON AND MON NIGHT.

ANOTHER FRONT WILL APPROACH THE COASTAL WATERS TUE NIGHT. ALBRECHT

&&

.SEW WATCHES/WARNINGS/ADVISORIES...
WA...NONE.

PZ...GALE WATCH COASTAL WATERS AND WEST ENTRANCE TO THE STRAIT
     SUN THROUGH SUN EVENING.

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