Small Craft Advisory 56, NWS Seattle, WA

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SEATTLE WA
1013 PM PDT SAT MAR 15 2014

.SYNOPSIS...A VERY MOIST SYSTEM WILL CONTINUE IMPACTING THE AREA
THROUGH SUNDAY MORNING FOR LOCALLY HEAVY RAINFALL. LOOK FOR A COLD
FRONT TO SWEEP ACROSS THE REGION SUNDAY AFTERNOON...RESULTING IN
PLUMMETING SNOW LEVELS AND LOCALLY HEAVY SNOW IN THE CASCADES.
SHOWERY WEATHER WILL PREVAIL MONDAY NIGHT IN THE WAKE OF THE COLD
FRONT. HIGH PRESSURE ALOFT WILL MOVE OVER THE AREA ON MONDAY BUT
THE AIR MASS WILL REMAIN UNSTABLE ENOUGH FOR A THREAT OF SHOWERS.

&&

.SHORT TERM...
THE SATELLITE-DERIVED PERCENT OF NORMAL TOTAL PRECIPITABLE WATER
/TPW/ INDICATED VALUES OF 150 PERCENT TO OVER 200 PERCENT OVER THE
CWA THIS AFTERNOON. THE VERY MOIST SYSTEM PRESENTLY IMPACTING OUR
AREA HAS TAPPED INTO A MOISTURE FEED EXTENDING WELL INTO THE
SUBTROPICS. TPW VALUES EXCEEDED AN INCH IN PLACES ALONG THIS
MOISTURE FETCH. THESE ANOMALOUSLY HIGH VALUES ARE BEING DIRECTED
AT THE CWA.

THE BAROCLINIC BAND WAS CURRENTLY DRAPED ACROSS MUCH OF THE CWA AT
THIS TIME. ALTHOUGH...THERE WAS SOME SHADOWING /OFF THE OLYMPICS/
OCCURRING OVER PARTS OF THE CENTRAL AND NORTH PUGET SOUND REGION.
THE FAR SOUTHEAST CORNER OF LEWIS COUNTY HAS NOT SEEN MUCH IF ANY
RAIN SO FAR. ANTICIPATE PRECIP RATES TO DROP DROP OFF OVERNIGHT
BEFORE PICKING UP AGAIN SUNDAY MORNING. IN THE PAST 6 HOURS ENDING
AT 915 PM PDT...SOME PLACES IN THE NORTH CASCADES RECEIVED ABOUT
AN INCH OR SLIGHTLY OVER AN INCH OF RAIN. SOME PLACES ON THE
OLYMPIC PENINSULA HAS RECEIVED 1.5 TO 2.5 INCHES DURING THE SAME
TIME FRAME. THIS MERITS KEEPING THE FLOOD WATCH UP. MINOR FLOODING
IS FORECAST ON A COUPLE OF RIVERS.

LOOK FOR THE BAROCLINIC BAND TO SAG SOUTHEAST DURING THE DAY
SUNDAY WITH THE MAIN COLD FRONT SWEEPING ACROSS THE AREA SUNDAY
AFTERNOON. SNOW LEVELS WILL PLUMMET SUNDAY AFTERNOON AND BY SUNDAY
EVENING...THE SNOW LEVEL SHOULD BE NEAR 2500 FEET ACROSS THE
NORTHWEST PART OF THE CWA AND NEAR 5K FT ACROSS THE FAR SOUTHEAST.
CURRENTLY...THERE IS A WINTER STORM WATCH FOR THE NORTH CASCADES
BUT AMOUNTS IN THE CENTRAL CASCADES COULD COME CLOSE TO WARNING
CRITERION OR END UP END WARNING CRITERION AMOUNTS...ESPECIALLY IF
A PUGET SOUND CONVERGENCE ZONE DEVELOPS...WHICH IS LIKELY.

SHOWERY WEATHER WILL PREVAIL SUNDAY NIGHT IN THE WAKE OF THE COLD
FRONT. AN UPPER RIDGE WILL BUILD OVER THE REGION FROM THE WEST ON
MON BUT THE AIR MASS WILL BE UNSTABLE ENOUGH TO SUPPORT SOME
SHOWERS...ESPECIALLY OVER THE MOUNTAINS. THE MODELS WERE HINTING
THAT A WARM FRONT OR THE REMNANTS OF A WARM FRONT WILL BRING SOME
LIGHT PRECIP TO THE AREA MON NIGHT.

THE LATEST GFS SOLUTION INDICATED THAT A PACIFIC STORM EMANATING
OUT OF THE GULF OF AK WILL BRING A CHANCE OF PRECIP TO THE AREA
TUE AFTERNOON. THE 1200 UTC SATURDAY RUN OF THE ECMWF WAS ALSO
INDICATING THE POSSIBILITY OF PRECIP OVER PARTS OF THE CWA TUE
AFTERNOON. IN OTHER WORDS...OUR CURRENT DRY FORECAST FOR TUE WAS
LOOKING DOUBTFUL.

.LONG TERM FROM THE PREV DISCUSSION...
THE ECMWF WAS NOW TRENDING TOWARD THE GFS SOLUTION ON WED WHICH
BRINGS A WEAK UPPER TROUGH THROUGH THE REGION. SO OUR DRY FORECAST
IS GONE AND REPLACED WITH A CHANCE OF SHOWERS. WE MAY SEE A BREAK
IN THE SHOWERS ON THU...THEN ANOTHER DISTURBANCE WILL ROLL THROUGH
ON FRIDAY. THE MODELS WERE ALSO COOLER THROUGH THE EXTENDED FORECAST
WITH SNOW LEVELS AROUND 2500 FT. 33

&&

.HYDROLOGY...
SIGNIFICANT RAINFALL /FOR MARCH/ HAS ALREADY FALLEN OVER PARTS OF
THE NORTH CASCADES AND OLYMPIC PENINSULA TODAY. THERE WAS A PERIOD
THIS AFTERNOON DURING WHICH QUILLAYUTE AIRPORT HAD RAIN RATES OF
ABOUT 0.4 PER HOUR. IT HAS BEEN RAINING ON MOUNT BAKER /NEAR THE
4K FOOT LEVEL/ AT A RATE OF ABOUT 0.25 INCH DURING THE PAST 5 OR 6
HOURS. RAIN RATES ARE EXPECTED TO DECREASE SOME OVERNIGHT BEFORE
PICKING UP AGAIN SUNDAY MORNING.

THE SATELLITE-DERIVED PERCENT OF NORMAL TOTAL PRECIPITABLE WATER
/TPW/ INDICATED VALUES OF 150 PERCENT TO OVER 200 PERCENT OVER THE
CWA THIS AFTERNOON. THE VERY MOIST SYSTEM PRESENTLY IMPACTING OUR
AREA HAS TAPPED INTO A MOISTURE FEED EXTENDING WELL INTO THE
SUBTROPICS. TPW VALUES EXCEEDED AN INCH IN PLACES ALONG THIS
MOISTURE FETCH. THESE ANOMALOUSLY HIGH VALUES ARE BEING DIRECTED
AT THE CWA.

AN ADDITIONAL 1 TO 2.5 INCHES OF PRECIP IS EXPECTED IN THE NORTH
CASCADES DURING THE 18-HOUR PERIOD ENDING AT 5 PM PDT SUNDAY...
WITH 1 TO 1.5 INCHES OF EXPECTED IN THE OLYMPIC RANGE DURING THIS
PERIOD. SNOW LEVELS WILL REMAIN ABOVE 5K FT IN THE MOUNTAINS
OVERNIGHT BUT WILL PLUMMET DURING THE DAY SUNDAY...ESPECIALLY
BEHIND THE COLD FRONT THAT WILL SWEEP ACROSS THE AREA IN THE
AFTERNOON. THUS...SOME OF THE PRECIP THAT FALLS SUNDAY AFTERNOON
IN THE MOUNTAINS WILL BE IN THE FORM OF SNOW.

MINOR FLOODING IS FORECAST FOR THE BOGACHIEL AND STILLAGUAMISH
RIVER NEAR ARLINGTON SUNDAY AFTERNOON. WILL NEED TO KEEP AN EYE ON
THE SKOKOMISH...NOOKSACK...SKAGIT...SNOHOMISH...AND SNOQUALMIE
RIVERS.

&&

.AVIATION...WEST TO SOUTHWEST FLOW ALOFT WILL PREVAIL TONIGHT AND
SUNDAY. A BAROCLINIC ZONE ACROSS THE FAR NORTHWEST PART OF WESTERN
WASHINGTON WILL SAG SLOWLY SOUTHEAST ACROSS THE AREA TONIGHT AND
SUNDAY. THE AIR MASS IS MOIST AND STABLE.

GENERALLY MVFR CEILINGS NORTH AND WEST OF SEATTLE THIS EVENING. ALL
AREAS WILL DEVELOP MVFR CEILINGS OR LOWER TONIGHT AS THE FRONTAL
BAND SLOWLY SHIFTS INLAND.

KSEA...3000-4000 FOOT CEILINGS THIS EVENING WILL LOWER TO 1000-2000
FEET TONIGHT AND REMAIN AROUND THERE THROUGH SUNDAY. SOUTHERLY WIND
8-12 KNOTS. SCHNEIDER

&&

.MARINE...A COLD FRONT WILL MOVE SLOWLY INLAND TONIGHT AND SUNDAY.
ALL WATERS WILL HAVE SMALL CRAFT ADVISORY WINDS FOR MUCH OF THIS
TIME.

STRONG ONSHORE FLOW WILL FOLLOW ON SUNDAY NIGHT AND MONDAY WITH GALE
WESTERLIES POSSIBLE OVER MUCH OF THE COASTAL WATERS AND DOWN THE
STRAIT OF JUAN DE FUCA. WEST SWELL IN THE 15-20 FOOT RANGE WILL ALSO
AFFECT THE COASTAL WATERS SUNDAY AND MONDAY.

AFTER A BRIEF RIDGE OF HIGH PRESSURE BUILDS ON TUESDAY...ANOTHER
FRONTAL SYSTEM WILL REACH THE AREA WEDNESDAY. SCHNEIDER

&&

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

     WINTER STORM WATCH IN EFFECT FROM 6 AM SUNDAY THROUGH LATE
     SUNDAY NIGHT FOR THE NORTH CASCADES ABOVE 3000 FEET.

PZ...SMALL CRAFT ADVISORIES ARE IN EFFECT FOR ALL WATERS.

     SMALL CRAFT ADVISORY IN EFFECT FOR ROUGH BAR CONDITIONS
     UNTIL 11 AM SUNDAY FOR THE GRAYS HARBOR BAR.

     GALE WATCHES ARE IN EFFECT IN EFFECT FROM SUNDAY EVENING
     THROUGH MONDAY AFTERNOON FOR THE COASTAL WATERS FROM CAPE
     FLATTERY TO POINT GRENVILLE OUT TO 60 NM AND THE CENTRAL/
     EASTERN STRAIT OF JUAN DE FUCA.

&&

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