High Surf Advisory 3, NWS Seattle, WA

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SEATTLE WA
400 PM PST MON NOV 16 2015

.SYNOPSIS...A WARM FRONT IS SPREADING PRECIPITATION ACROSS WESTERN
WASHINGTON THIS EVENING...WITH LOCALLY WINDY CONDITIONS. A DEEPENING
AREA OF LOW PRESSURE WILL PASS ACROSS SOUTHERN BRITISH COLUMBIA ON
TUESDAY...LEADING TO VERY WINDY CONDITIONS WITH HEAVY RAIN. A BREAK
IN THE WEATHER IS EXPECTED FOR MUCH OF WEDNESDAY. A LOW WILL TRACK
BY TO OUR SOUTH ON WEDNESDAY NIGHT OR THURSDAY...BRUSHING WESTERN
WASHINGTON WITH MORE RAIN.

&&

.SHORT TERM...A BUSY WEATHER PATTERN IS UNDERWAY. JUST IN THE
FIRST 48 HOURS...WE HAVE CONCERNS THAT INCLUDE ADDITIONAL RAIN
WITH RENEWED FLOODING...MOUNTAIN SNOW...AND STRONG WIND.

A STRONG WARM FRONT IS CURRENTLY SPREADING INTO WRN WA. THE FRONT IS
AT THE NOSE OF A 180 KT UPPER JET THAT IS CUTTING ACROSS THE SRN
GULF OF ALASKA. THIS SETUP HAS LED TO THE WINDY CONDITION OVER THE
NORTH INTERIOR AND ALONG THE COAST TODAY. THE WINDS SHOULD EASE
SIGNIFICANTLY OVER THE NEXT 4 HOURS.

REGARDING MOUNTAIN SNOW...RADAR SHOWS A SOLID SHIELD OF PRECIP
ACROSS THE AREA. THE AIR MASS AHEAD OF THE WARM FRONT IS FAIRLY
COOL...WITH MOUNTAIN PASS TEMPERATURES IN THE UPPER 20S RIGHT NOW.
SO PRECIP HAS START AS SNOW AT ALL OF THE MOUNTAIN HIGHWAY PASSES.
SNOW LEVELS WILL RISE TO BETWEEN 5000 AND 6000 FEET LATE THIS
EVENING AND OVERNIGHT. THIS WILL BRING A CHANGEOVER TO RAIN ALONG
THE MAJOR HIGHWAY CORRIDORS.

ON TUESDAY...THE CORE OF THE STRONG JET WILL HAVE MOVED FROM THE
SOUTHERN GULF OF ALASKA TO SRN B.C.. THIS WILL SUPPORT RAPID
DEEPENING OF A SURFACE LOW AS IT QUICKLY MOVES EASTWARD ACROSS SRN
B.C. ON TUE. IN ADDITION...A TRAILING COLD FRONT WILL THEN SLIP
SOUTHWARD THROUGH WRN WA IN THE AFTN AND EVNG. THIS WILL REALLY
TIGHTEN SOUTHERLY AND THEN SW-W PRESSURE GRADIENTS OVER WRN
WA...LEADING TO A HIGH WIND EVENT IN PARTS OF THE AREA. STRONGEST
WINDS OF THE DAY WILL COME IN THE EARLY AFTERNOON WITH THE SW-W
WINDS THAT DEVELOP ALONG THE COLD FRONT. LOCATIONS MOST PRONE TO
WESTERLY WINDS WILL BE AREAS OPEN TO THE STRAIT OF JUAN DE
FUCA...SUCH AS LAND AREAS ON THE U.S. SIDE OF THE STRAIT...THE
ADMIRALTY INLET AREA...AND PERHAPS THE EVERETT AREA. ANOTHER
CORRIDOR OF STRONGER WINDS THAT IS COMMON IN WESTERLY FLOW IS TO THE
SOUTH OF THE OLYMPIC MTNS...WITH HIGH WIND POSSIBLE ALONG A SWATH
FROM HOQUIAM TO SHELTON TO TACOMA AND SOUTHERN KING COUNTY.
OTHER LOCATIONS WILL BE WINDY FOR SURE...BUT THESE TWO SWATHS BEAR
THE MOST SCRUTINY.

RISING HEIGHTS WILL HELP CARVE OUT WEDNESDAY AS A LULL IN THE
WEATHER. JUST A FEW SHOWERS WILL BE AROUND IN A COOLER AIR MASS.
WINDS WILL BE MUCH LIGHTER.

ON WEDNESDAY NIGHT AND THURSDAY...MODELS AGREE IN CRUISING A LOW
CENTER EASTWARD ACROSS NORTHERN OREGON...WHICH SHOULD SPREAD A
PRECIPITATION SHIELD UP OVER WRN WA TO THE NORTH OF THE LOW TRACK.
THE MOST UNCERTAIN ASPECT IS WITH TIMING. THE 12Z AND 18Z GFS SPREAD
PRECIP INTO WRN WA LATE WED AFTN...WHILE THE ECMWF AND NAM ARE ABOUT
12 HOURS LATER...WAITING UNTIL THE OVERNIGHT HOURS ON WED NGT TO
SPREAD PRECIP ACROSS THE AREA. THE OTHER POINT OF UNCERTAINTY IS
WITH HOW FAR NORTH PRECIP SPREADS...WITH SOLUTIONS RANGING FROM THE
EVERETT AREA TO THE CANADIAN BORDER.

SEE THE HYDROLOGY SECTION FOR RAIN DETAILS AND HYDRO IMPACTS.
HANER

.LONG TERM...THERE IS VERY LITTLE AGREEMENT BETWEEN THE GFS AND
ECMWF FROM FRI THROUGH NEXT MON. THE GFS DRIES OUT THE WEATHER
BEHIND WEDNESDAY NIGHT/THURSDAY'S SYSTEM...AND KEEPS THE WEATHER DRY
UNTIL MON. THE ECMWF SHOWS QUITE A BIT OF SOUTHERN STREAM ENERGY
SPREADING INTO ORE THROUGH SAT...WITH PRECIP SHIELDS EXPANDING UP
INTO WRN WA AT TIMES. THE ECMWF DOES SHOW A DRY PERIOD LATE
SAT...BUT CONFIDENCE IS TOO LOW TO ANYTHING BUT CARRY BROAD-BRUSH
CHANCE POPS FROM THU NGT THROUGH NEXT MON.		HANER

&&

.AVIATION...A STRONG WARM FRONT WILL CONTINUE TO MOVE EASTWARD
THROUGH WESTERN WA TODAY...WITH COLD FRONT EXPECTED TO PASS THROUGH
TOMORROW. NORTHWESTERLY FLOW TURNING MORE WESTERLY BY LATE
AFTERNOON. AIR MASS STABLE WITH AMPLE MOISTURE THROUGHOUT. CIGS WILL
CONTINUE TO LOWER...WITH MOST LOCATIONS BECOMING MVFR BY THIS
EVENING. WINDS ARE EXPECTED TO STEADILY INCREASE THROUGHOUT THE DAY
AND DURING THE OVERNIGHT HOURS. GUSTY WINDS ARE EXPECTED TO BE OVER
MUCH OF THE AREA BY THIS EVENING.

KSEA...CEILINGS WILL CONTINUE TO DROP THIS AFTERNOON...DIPPING INTO
MVFR CONDITIONS BY 00Z AND BECOMING LOW END MVFR TOMORROW MORNING.
SOUTH TO SOUTHWESTERLY WINDS 7-14 KNOTS WITH GUSTS BETWEEN 20-25
KTS...INCREASING TO 20-30 KTS WITH GUSTS UP TO 40 KTS POSSIBLE
TUESDAY MORNING AND AFTERNOON. SMR

&&

.MARINE...A STRONG WARM FRONT PASSING THROUGH THE AREA CONTINUES TO
BRING WINDS REACHING SMALL CRAFT ADVISORY OR GALE SPEEDS...DEPENDING
ON LOCATION. A DEEP SURFACE LOW WILL TRACK INLAND OVER SOUTHERN
BRITISH COLUMBIA ON TUESDAY...BRINGING ANOTHER ROUND OF GALES TO
MOST WATERS WITH STORM FORCE WINDS POSSIBLE FOR SOME WATERS.
THUS...INHERITED GALE WATCHES HAVE BEEN UPGRADED TO WARNINGS SAVE
FOR WATERS OF THE STRAIT. THOSE HAVE BEEN UPGRADED TO STORM WARNINGS
AS WINDS LOOK TO BE STRONGEST THERE. A TRAILING COLD FRONT WILL MOVE
THROUGH THE AREA LATER TUESDAY WITH EASING ONSHORE FLOW AND MUCH
LIGHTER WINDS BY WEDNESDAY. WEST SWELL 18-22 FEET WILL REACH THE
COASTAL WATERS TUESDAY AFTERNOON...SO HAVE ISSUED A HIGH SURF
ADVISORY ALONG THE COAST. THESE SWELLS WILL SUBSIDE ON WEDNESDAY.

A WEAKER WARM FRONT WILL MOVE THROUGH THE AREA WEDNESDAY NIGHT OR
THURSDAY. NORTH TO NORTHEAST LOW LEVEL FLOW WILL DEVELOP THURSDAY AS
HIGH PRESSURE MOVES OVER SOUTHERN BRITISH COLUMBIA WITH LOW PRESSURE
OVER THE COASTAL WATERS. SCHNEIDER/SMR

&&

.HYDROLOGY...PRECIP INENSITIES REALLY PICK UP OVER THE MTNS THIS
EVNG...JUST IN TIME FOR SNOW LEVELS TO RISE INTO THE 5500-6500 FT
RANGE. WITH SUCH STRONG ONSHORE FLOW TOMORROW...PRECIP WILL BE
INTENSE AND FOCUSED OVER MTN HEADWATERS. THE 12Z GFS SHOWS 24-HOUR
PRECIP AMOUNTS OF 5-8 INCHES OVER THE OLYMPICS AND CASCADES FOR THE
PERIOD ENDING LATE TUE EVNG.

RIVERS HAVE BARELY HAD TIME TO RECOVER AND RECEDE FROM THIS LAST
ROUND OF FLOODING. IN ADDITION THE SOILS ARE SATURATED LEADING TO
PRIME RUN OFF CONDITIONS. MANY RIVERS HAVE THE POTENTIAL TO FLOOD
AGAIN WITH THE RIVERS POSSIBLY CRESTING HIGHER THAN THE FLOOD OVER
THE WEEKEND. 	HANER

&&

.SEW WATCHES/WARNINGS/ADVISORIES...
WA...FLOOD WATCHES AND/OR WARNINGS OVER MUCH OF WESTERN WASHINGTON.
     WIND ADVISORY UNTIL 10 PM COAST AND NORTH INTERIOR.
     WIND ADVISORY ON TUESDAY SOUTHWEST INTERIOR...SAN JUANS...
      WESTERN WHATCOM AND WESTERN SKAGIT COUNTIES.
     HIGH WIND WARNING ON TUESDAY FOR THE COAST...STRAIT OF JUAN
      DE FUCA...ADMIRALTY INLET...LOWER CHEHALIS VALLEY...AND THE
      PUGET SOUND LOWLANDS FROM TACOMA NORTH TO EVERETT.
     WINTER STORM WARNING UNTIL 4 AM PST FOR THE CASCADES.

PZ...SMALL CRAFT ADVISORY FOR ROUGH BAR UNTIL 9 PM PST THIS EVENING
     FOR GRAYS HARBOR BAR.

     GALE WARNING UNTIL 6 PM PST TUESDAY FOR COASTAL WATERS FROM CAPE
     FLATTERY TO JAMES ISLAND 10 TO 60 NM-COASTAL WATERS FROM
     CAPE FLATTERY TO JAMES ISLAND OUT 10 NM-COASTAL WATERS FROM
     JAMES ISLAND TO POINT GRENVILLE 10 TO 60 NM-COASTAL WATERS
     FROM JAMES ISLAND TO POINT GRENVILLE OUT 10 NM-COASTAL
     WATERS FROM POINT GRENVILLE TO CAPE SHOALWATER 10 TO 60 NM-
     COASTAL WATERS FROM POINT GRENVILLE TO CAPE SHOALWATER OUT
     10 NM.

     GALE WARNING UNTIL 10 PM PST THIS EVENING FOR ADMIRALTY INLET-
     EAST ENTRANCE U.S. WATERS STRAIT OF JUAN DE FUCA-NORTHERN
     INLAND WATERS INCLUDING THE SAN JUAN ISLANDS-WEST ENTRANCE
     U.S. WATERS STRAIT OF JUAN DE FUCA.

     GALE WATCH FROM LATE TONIGHT THROUGH TUESDAY EVENING FOR WEST
     ENTRANCE U.S. WATERS STRAIT OF JUAN DE FUCA.

     GALE WATCH FROM LATE TONIGHT THROUGH TUESDAY EVENING FOR CENTRAL
     U.S. WATERS STRAIT OF JUAN DE FUCA.

     SMALL CRAFT ADVISORY UNTIL 4 AM PST TUESDAY FOR CENTRAL U.S.
     WATERS STRAIT OF JUAN DE FUCA-PUGET SOUND AND HOOD CANAL.

     GALE WATCH FROM LATE TONIGHT THROUGH TUESDAY EVENING FOR PUGET
     SOUND AND HOOD CANAL.

&&

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