Gale Warning 66, NWS Seattle, WA

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SEATTLE WA
900 AM PST MON NOV 23 2015

.SYNOPSIS...A COLD FRONT WILL BRING RAIN THIS AFTERNOON AND
EVENING. AN UPPER TROUGH WILL MOVE OVER THE REGION TONIGHT AND
TUESDAY. FRASER OUTFLOW WILL DEVELOP AROUND DAYBREAK TUESDAY. THE
MAIN SNOW LEVEL WILL DROP TO AROUND 1000 FEET BUT A MIX OF RAIN AND
SNOW SHOWERS IS POSSIBLE DOWN TO 500 FEET. ANY SNOW ACCUMULATION
WILL LIKELY REMAIN OVER THE CASCADES THROUGH TUESDAY MORNING. HIGH
PRESSURE WILL KEEP THE WEATHER DRY WEDNESDAY THROUGH NEXT WEEKEND.

&&

.SHORT TERM...WATER VAPOR SATELLITE IMAGERY SHOWS THE APPROACHING
POSITIVE TILT TROUGH ALONG THE SOUTH/CENTRAL B.C. COAST MOVING
TOWARD THE PAC NW. COASTAL RADAR IS PICKING  UP THE LEADING EDGE
OF SOME LIGHT RAIN OR SPRINKLES JUST SKIRTING THE NORTH
COAST AND FAR NORTH INTERIOR THIS MORNING. STEADIER RAIN WILL PUSH
INTO WESTERN WASHINGTON DURING THE AFTERNOON AND EARLY EVENING. RAIN
WILL TAPER TO SHOWERS AFTER MIDNIGHT AND CONTINUE THROUGH TUESDAY
MORNING BEFORE ENDING. THERE WAS SOME CONCERN FOR LOWLAND SNOW AS
PREVIOUS MODELS WERE COLDER BY TUESDAY MORNING. 12Z MODEL RUN TRENDS
CONTINUE TO SHOW THE COLDEST AIR REMAINING BOTTLED UP OVER B.C. WITH
SOME LOWER DEW POINT AIR FILTERING INTO MAINLY THE NORTH INTERIOR.
MODELS SHOW MOISTURE SHIFTING SOUTH OF THE PUGET SOUND
REGION BY 18Z TUESDAY SO THE LAG DOES NOT BODE WELL FOR LOWLAND
SNOW. WILL KEEP SNOW LEVELS AT AROUND 1000 FEET BUT KEEP A
MENTION OF RAIN/SNOW SHOWERS MIXED DOWN TO 500 FEET INLAND FROM
THE WATER AND NORTH OF SEATTLE WITH LITTLE OR NO ACCUMULATION EXPECTED.
WILL NEED TO MONITOR ANY CONVERGENCE ZONE ACTIVITY ALONG THE
OUTFLOW FRONT TUESDAY WHICH COULD ARTIFICIALLY DRAG THE SNOW LEVEL
LOWER BUT THAT THREAT IS MINIMAL AT THIS POINT.

MOUNTAINS WILL GET SNOW OVERNIGHT TONIGHT INTO TUESDAY MORNING.
MODELS ARE IN GOOD AGREEMENT OF ABOUT 2 TO 5 INCHES IN THE CASCADES WITH
HIGHEST AMOUNTS AT SPOTS LIKE PARADISE AND MOUNT BAKER. THE PASSES
COULD HAVE A FEW INCHES BUT THE SYSTEM LOOKS TO BE SUB-ADVISORY AT
THIS TIME. SNOW SHOULD TAPER OFF OVER THE MOUNTAINS BY MIDDAY
TUESDAY.

FRASER OUTFLOW IS STILL ANTICIPATED TO BEGIN TUESDAY MORNING OVER
THE NORTH INTERIOR. THE WRFGFS4KM SHOWS THE STRONGEST WINDS AFTER
DAYBREAK TUESDAY THROUGH THE EVENING...THEN EASING. WITH BLI-YWL
PRESSURE GRADIENT PEAKING AROUND +16 TO 18 MB...A WIND ADVISORY WILL
PROBABLY SUFFICE FOR THE NORTH INTERIOR. WILL MAKE THE FINAL
DECISION ON THAT WITH THE AFTERNOON FORECAST PACKAGE. EXPECT
NORTHEASTERLY WINDS OF 20-35 MPH WITH GUSTS TO 50 MPH ACROSS WESTERN
WHATCOM COUNTY AND THE SAN JUANS TUESDAY MORNING THROUGH TUESDAY
EVENING.

DRIER AIR WILL FILTER SOUTH THROUGH THE INTERIOR INCLUDING PUGET
SOUND LATER TUESDAY AS OUTFLOW INCREASES. THIS WILL CLEAR OUT CLOUDS
WITH DRY WEATHER EXPECTED ACROSS THE AREA TUESDAY NIGHT AND
WEDNESDAY. LOW TEMPERATURES WEDNESDAY MORNING WILL FALL BELOW
FREEZING A MANY AREAS...ESPECIALLY AWAY FROM THE WATER. SUB FREEZING
MORNING LOWS THROUGH THE END OF THE WEEK COULD CAUSE BLACK ICE TO
FORM...ESPECIALLY NEAR BRIDGES AND OVERPASSES. THAT WILL BE THE MAIN
WEATHER RELATED TRAVEL CONCERN FOR THE UPCOMING HOLIDAY PERIOD.
MERCER

.LONG TERM...FROM PREVIOUS DISCUSSION...STRONG HIGH PRESSURE ALOFT
OVER THE NORTHEAST PACIFIC WILL KEEP THE WEATHER DRY THROUGH NEXT
WEEKEND. DAYS WILL BE SUNNY AND NIGHTS CLEAR BUT TEMPERATURES WILL
BE A LITTLE BELOW NORMAL.
SCHNEIDER

&&

.AVIATION...AN UPPER LEVEL TROUGH WILL DIVE IN FROM THE NW THIS
AFTN. IN ADVANCE OF THE TROUGH...MOISTURE AND LIFT WILL INCREASE
TODAY. THERE ARE SOME PATCHES OF LOW CLOUDS AND FOG...MAINLY OVER
THE WATER...AND THERE WILL ALSO BE A THICKENING OF MID-LEVEL CLOUDS.
A COLD FRONT WILL ARRIVE OUT OF THE NW THIS AFTN...LEADING TO THE
DEVELOPMENT OF SHOWERS THIS AFTN AND EVNG. DURING THE HEAVIEST
PRECIP CIGS WILL LOWER INTO THE 010-020 RANGE FOR A TIME. THE
MOUNTAINS WILL BECOME OBSCURED IN PRECIP THIS AFTERNOON.

KSEA...INCREASING CLOUDS WITH RAIN DEVELOPING LATER TODAY THROUGH
THIS EVENING. AS THE WIND SHIFTS FROM SLY TO NLY TUESDAY MORNING
THERE WILL BE SOME SHOWERS AS THE SNOW LEVEL DROPS TO AROUND 500
FT...BUT NO ACCUMULATION IS EXPECTED EXCEPT MAYBE A LITTLE SLUSH ON
THE GRASS. KPAE PROBABLY HAS A BETTER CHANCE OF SEEING A LITTLE SNOW
THAN SEA TAC.

&&

.MARINE...A COLD FRONT WILL ARRIVE FROM THE NW THIS AFTN... BRINGING
GALES TO THE OUTER COASTAL WATERS THIS EVENING. FRASER OUTFLOW WINDS
WILL DEVELOP TUE MORNING FOR A PERIOD OF NELY GALES FROM THE
NORTHERN INLAND WATERS INTO THE EASTERN HALF OF THE STRAIT. FRASER
OUTFLOW WILL EASE ON WED...WITH LIGHT TO MODERATE OFFSHORE FLOW
EXPECTED FOR THE REST OF THE WEEK.

&&

.HYDROLOGY...FLOODING IS NOT EXPECTED FOR THE NEXT SEVEN DAYS.

&&

.SEW WATCHES/WARNINGS/ADVISORIES...
WA...HIGH WIND WATCH FROM LATE TONIGHT THROUGH LATE TUESDAY NIGHT FOR
     SAN JUAN COUNTY-WESTERN WHATCOM COUNTY.
PZ...SMALL CRAFT ADVISORY FROM 7 AM THIS MORNING TO 5 AM PST TUESDAY
     FOR COASTAL WATERS FROM POINT GRENVILLE TO CAPE SHOALWATER
     10 TO 60 NM.

     SMALL CRAFT ADVISORY FOR ROUGH BAR FROM 8 PM THIS EVENING TO 4
     PM PST TUESDAY FOR GRAYS HARBOR BAR.

     GALE WARNING FROM NOON TODAY TO 10 PM PST THIS EVENING FOR
     COASTAL WATERS FROM CAPE FLATTERY TO JAMES ISLAND 10 TO 60
     NM-COASTAL WATERS FROM JAMES ISLAND TO POINT GRENVILLE 10
     TO 60 NM.

     SMALL CRAFT ADVISORY FROM 1 PM THIS AFTERNOON TO 5 AM PST
     TUESDAY FOR COASTAL WATERS FROM CAPE FLATTERY TO JAMES
     ISLAND OUT 10 NM-COASTAL WATERS FROM JAMES ISLAND TO POINT
     GRENVILLE OUT 10 NM-COASTAL WATERS FROM POINT GRENVILLE TO
     CAPE SHOALWATER OUT 10 NM.

     GALE WATCH FROM TUESDAY MORNING THROUGH WEDNESDAY MORNING FOR
     CENTRAL U.S. WATERS STRAIT OF JUAN DE FUCA-EAST ENTRANCE
     U.S. WATERS STRAIT OF JUAN DE FUCA-NORTHERN INLAND WATERS
     INCLUDING THE SAN JUAN ISLANDS.

&&

WWW.WEATHER.GOV/SEATTLE

YOU CAN SEE AN ILLUSTRATED VERSION OF THIS DISCUSSION AT
WWW.WEATHER.GOV/SEATTLE/GAFD/LATEST_WEBAFD.HTML