Small Craft Advisory 1137, NWS Seattle, WA

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SEATTLE WA
915 AM PST SAT DEC 15 2012

.SYNOPSIS...A STRONG PACIFIC STORM WILL BRING GUSTY WINDS TO THE
AREA TODAY AS WELL AS RAIN AND MOUNTAIN SNOW. AN EVEN STRONGER
SYSTEM WILL IMPACT THE REGION SUNDAY NIGHT AND MONDAY FOR THE
POSSIBILITY OF HIGH WINDS OVER THE COAST AND NORTH INTERIOR AS WELL
AS HEAVY SNOW IN THE MOUNTAINS. A COLDER AIR MASS WILL FOLLOW THIS
SYSTEM MONDAY NIGHT...WITH SNOW LEVELS PREDICTED TO PLUMMET TO NEAR
SEA LEVEL BY TUESDAY MORNING.

&&

.SHORT TERM...LATEST SATELLITE IMAGE SHOWS THE NEXT FRONT NOW INSIDE
130 W MOVING TOWARD THE AREA. RADAR INDICATES LIGHT RAIN IS FILLING
IN ACROSS THE INTERIOR WITH PRECIPITATION STARTING ALSO PUSHING INTO
THE CASCADES. THE WINTER WEATHER ADVISORY STATEMENT WAS UPDATED
EARLIER TO INDICATE THE FASTER ONSET OF SNOW WHICH LOOKS GOOD. SNOW
LEVELS ARE STARTING OFF RATHER LOW...500 TO 1500 FEET DEPENDING ON
LOCATION. HIGHER HILLTOPS AND COULD SEE SOME BRIEF MIXED RAIN/SNOW
BUT NO ACCUMULATION. SHELTERED PORTIONS OF HOOD CANAL/KITSAP WILL
ALSO HAVE SOME MIXED RAIN/SNOW OR WET SNOW BUT NOT MUCH MORE THAN A
SLOPPY INCH OF ACCUMULATION IS EXPECTED THERE. THE MOUNTAINS WILL
GET SNOW...HEAVY AT TIMES THROUGH TUESDAY MORNING. COLD AIR...DOWN
TO -6C AT 850 MB AND -34 C AT 500 MB...ALONG WITH STRONGER FLOW
BEHIND THE FRONT WILL INCREASE SNOW RATIOS AND OROGRAPHICS ALONG THE
W SLOPES OF THE CASCADES AND OLYMPICS. SNOW TOTALS WITH THIS SYSTEM
OF 8 TO 16 INCHES LOOK REASONABLE...WITH MUCH MORE SNOW EXPECTED
WITH THE NEXT SYSTEM.

SE WINDS ARE ALREADY PICKING UP OVER THE USUAL AREAS FROM ADMIRALTY
INLET NWD. MESO MODELS AND MOS GUIDANCE SUGGEST BORDERLINE WIND
ADVISORY CRITERIA IS POSSIBLE FOR THIS AREA. WILL MONITOR WIND
SPEEDS CLOSELY TODAY WITH STRONGEST WINDS JUST AHEAD OF THE FRONT
EXPECTED FROM MIDDAY THROUGH EARLY AFTERNOON. ELSEWHERE...JUST A BIT
BREEZY TODAY WITH RAIN AT TIMES. THE LOWLANDS WILL SEE A CHANGE OVER
TO SHOWERS TONIGHT AND EARLY SUNDAY MORNING BUT THE MOUNTAINS WILL
GENERALLY HAVE CONTINUOUS SNOW. SO NO REAL BREAK BETWEEN SYSTEMS.

THE NEXT MAJOR STORM SYSTEM APPEARS ON TRACK LOOKING AT THE NEW 12Z
GFS/NAM THIS MORNING. ALL THE FORECAST MODELS REMAIN IN GOOD
AGREEMENT OF RAPID SURFACE LOW DEVELOPMENT SUNDAY AND SUNDAY
NIGHT...DEEPENING DOWN TO 970-980 MB HEADING ON AN EWD COURSE TOWARD
WRN WA. THE LOW CENTER IS EXPECTED TO MOVE ONSHORE SOMEWHERE BETWEEN
THE CENTRAL WA COAST OR DOWN THE STRAIT. THIS TRAJECTORY PUTS ALL OF
WRN WA UNDER THE THREAT OF HIGH WINDS. AT THIS POINT...HIGH WINDS
APPEAR MOST LIKELY ALONG THE COAST...AND N INTERIOR. STRONGER MODEL
SOLUTIONS ALSO PUT THE STRAIT...PUGET SOUND REGION...SW INTERIOR
AND REMAINING AREAS AT RISK OF HIGH WIND AS WELL. I HAVE NOT SEEN
ALL THE MORNING MODEL DATA YET BUT GIVEN THE KBLI-KPDX GRADIENTS
OVER +15 MB ON MOST MODELS...A WATCH WILL PROBABLY BE NEEDED FOR ALL
THE LOWLANDS INCLUDING PUGET SOUND/SW INTERIOR.

SNOW LEVELS WILL ALSO BE LOW WITH THIS NEXT SYSTEM MUCH LIKE THIS
MORNING. A QUICK LOOK AT THE NAM-12 INDICATES A PERIOD OF RAIN/SNOW
MIX OR PERHAPS A PERIOD OF WET SNOW POSSIBLE IN THE HOOD CANAL ZONE.
WILL NEED TO LOOK AT THIS CLOSER AS SOME BRIEF ACCUMULATION THERE
MIGHT BE POSSIBLE. SNOW WILL INCREASE IN THE CASCADES SUNDAY
AFTERNOON...EARLIER IN THE OLYMPICS. QPF AMOUNTS ARE IMPRESSIVE DUE
TO STRONG FLOW...COLD AIR...AND STRONG DYNAMIC LIFT RESULTING IN 2
TO 3+ FEET OF SNOW ACCUMULATION IN THE MOUNTAINS FROM SUNDAY
AFTERNOON THROUGH TUESDAY MORNING. IT WILL BE VERY WINDY WITH
EXTREMELY LOW VISIBILITY AT TIMES DUE TO BLOWING AND DRIFTING SNOW.
WESTERLY WINDS IN THE PASSES BEHIND THE LOW ON MONDAY COULD EASILY
EXCEED 40 MPH WITH HIGHER GUSTS. WILL LIKELY HOIST A WINTER STORM
WATCH LATER TODAY TO PICK UP WHERE THE CURRENT ADVISORY ENDS AT NOON
SUNDAY WHICH WILL RUN THROUGH AT LEAST TUESDAY MORNING. SNOW LEVELS
WILL BE QUITE LOW MONDAY NIGHT AND TUESDAY...BELOW 1000 FEET. HEAVY
SHOWERS OR ANY CONVERGENCE ZONE DEVELOPMENT COULD PUT DOWN SOME
LOCALIZED ACCUMULATIONS CLOSE TO SEA LEVEL. HIGHS TUESDAY MAY
STRUGGLE OUT OF THE 30S INCLUDING THE PUGET SOUND REGION. MERCER

.LONG TERM...A COLD UPPER TROUGH WILL BEGIN TO MOVE EAST OF THE
REGION TUESDAY NIGHT WITH DECREASING SHOWERS. LITTLE BREAK IS
EXPECTED AS A WARM FRONT ASSOCIATED WITH THE NEXT FRONTAL SYSTEM
WILL SPREAD RAIN BACK INTO THE AREA ON WEDNESDAY. THE FRONT OCCLUDES
AS IT MOVES INTO WRN WA WITH ONLY SLIGHT RISES IN SNOW LEVELS. THE
ASSOCIATED COLD FRONT WILL PUSH INTO THE AREA WEDNESDAY EVENING THEN
WEAKEN AND SPLIT WITH THE STRONGER PORTION HEADING SWD.

A LARGE UPPER LOW CENTERED BETWEEN 130-140 W WILL STALL THROUGH THE
REST OF THE WEEK. THIS WILL KEEP WRN WA UNDER MOIST SLY OR SW FLOW.
MODELS SHOW MOSTLY WEAK SYSTEMS TO BRING RAIN OR SHOWERS AT TIMES TO
THE AREA. NO CHANGES TO THE EXTENDED. MERCER

&&

.HYDROLOGY...
FLOODING IS NOT EXPECTED ON AREA RIVERS THROUGH THE END OF NEXT
WEEK. MERCER

&&

.AVIATION...A VIGOROUS COLD FRONT WILL MOVE THROUGH WESTERN WA
TODAY. THE FRONTAL PASSAGE WITH RAIN TURNING TO SCATTERED SHOWERS
WILL REACH THE COAST MIDDAY AND PUSH THROUGH THE INTERIOR OF WESTERN
WA IN THE AFTERNOON. BLUSTERY TODAY...AND THE AREAS WHICH ARE
TYPICALLY PRONE TO THE SSE WINDS AHEAD OF THE FRONT ARE ALREADY
WINDY. THE PUGET SOUND AREA WILL BECOME BLUSTERY AS THE FRONT MOVES
THROUGH THIS AFTERNOON AND THE WIND SHIFTS FROM SE TO SW. THE
MOUNTAINS WILL REMAIN OBSCURED. 19

KSEA...CURRENT TAF LOOKS GOOD...IT SHOULD BE RATHER BREEZY LATE THIS
AFTERNOON THROUGH THE EVENING HOURS WITH A SW WIND BEHIND THE FRONT.
19

&&

.MARINE...VIGOROUS COLD FRONT WILL SWEEP THROUGH THE WATERS TODAY
WITH SE GALES THIS MORNING AND A WIND SHIFT THROUGH THE COASTAL
WATERS BY MIDDAY AND THROUGH PUGET SOUND AND THE INLAND WATERS IN
THE AFTERNOON. BEHIND THE FRONT STRONG ONSHORE FLOW IS EXPECTED WITH
A BLUSTERY SW WIND MOST AREAS EXCEPT WEST WIND COASTAL WATERS AND
STRAIT.

A RATHER STRONG FRONTAL SYSTEM WILL REACH THE AREA SUNDAY EVENING.
SEVERAL FORECAST MODELS SHOW A SURFACE LOW AROUND 975 MILLIBARS
REACHING THE SOUTH END OF VANCOUVER ISLAND SUNDAY NIGHT OR EARLY
MONDAY MORNING. MONDAY WILL BE A WINDY DAY WITH FULL GALES MOST
WATERS AND STORM FORCE WINDS POSSIBLE COAST AND STRAIT. THERE COULD
BE A SIGNIFICANT WESTERLY PUSH DOWN THE STRAIT MONDAY MORNING AND
THE CURRENT 12Z NAM HAS A UIL-BLI GRADIENT OF +7 MB AT 4AM MONDAY
WITH A 980MB LOW CENTER JUST NORTH OF KBLI. THE INTERIOR WATERS AND
PUGET SOUND SHOULD BE QUITE WINDY AS WELL WITH THAT 12Z NAM GIVING A
+16MB GRADIENT AT 4AM MONDAY.

THE DEEP LOW MONDAY MORNING WILL LIKELY GIVE A STORM SURGE OF A
COUPLE FOOT TIDAL ANOMALY SO TIDAL OVERFLOW IS LIKELY DURING HIGH
TIDE MONDAY MORNING IN THE INTERIOR WATERS. ALSO...A COASTAL FLOOD
WATCH IS LIKELY TO BE ISSUED IF HIGH COASTAL SURF BIG ENOUGH TO
AFFECT THE BEACHES AT HIGH TIDE MONDAY...ALTHOUGH THE TIMING IS
DIFFERENT FOR THE COAST WHERE LOW TIDE MAY COINCIDE WITH THE
HIGHEST TIDAL ANOMALY WHICH MAY HELP QUITE A BIT. THE AFTERNOON HIGH
TIDE ON THE COAST HOWEVER SHOULD HAVE HIGH SURF CRASHING THE
BEACHES. SOME SORT OF A STATEMENT OR OUTLOOK WILL LIKELY BE ISSUED
WITH THE AFTERNOON FORECAST PACKAGE FOR SUN NITE AND MONDAY FOR THE
TIDES AND SURF. 19

&&

.SEW WATCHES/WARNINGS/ADVISORIES...
WA...WINTER WEATHER ADVISORY IN EFFECT FOR THE OLYMPICS AND CASCADES
     UNTIL NOON SUNDAY.

PZ...GALE WARNING COASTAL WATERS...ENTRANCES TO THE STRAIT OF JUAN
     DE FUCA AND NORTHERN INLAND WATERS. SMALL CRAFT ADVISORY
     CENTRAL STRAIT...ADMIRALTY INLET...PUGET SOUND. SMALL CRAFT
     ADVISORY GRAYS HARBOR BAR FOR ROUGH BAR CONDITIONS.

&&

WWW.WEATHER.GOV/SEATTLE

FOR THE GRAPHICAL AFD...VISIT
WWW.WEATHER.GOV/SEATTLE/GAFD/LATEST_WEBAFD.HTML

PRELIMINARY LOCAL STORM REPORT
NATIONAL WEATHER SERVICE SEATTLE WA
148 PM PST SAT DEC 15 2012

..TIME...   ...EVENT...      ...CITY LOCATION...     ...LAT.LON...
..DATE...   ....MAG....      ..COUNTY LOCATION..ST.. ...SOURCE....
            ..REMARKS..

0147 PM     SNOW             1 E BREMERTON           47.55N 122.68W
12/15/2012  M1.0 INCH        KITSAP             WA   PUBLIC

            AN INCH OF SNOW, ROADS BARE AND WET

&&

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