Area Forecast Discussion
Issued by NWS Seattle/Tacoma, WA

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000
FXUS66 KSEW 021658
AFDSEW

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SEATTLE WA
858 AM PST TUE FEB 2 2016

.SYNOPSIS...NORTHWEST FLOW ALOFT OVER WESTERN WASHINGTON WILL
RESULT IN PARTLY TO MOSTLY SUNNY SKIES TODAY. A FRONTAL SYSTEM
WILL MOVE THROUGH THE FORECAST AREA WEDNESDAY FOR RAIN IN THE
LOWLANDS AND MOUNTAIN SNOW. A STRONGER SYSTEM WILL MOVE THROUGH
THE AREA FRIDAY...AND SHOWERS WILL TAPER OFF SATURDAY. A STRONG
UPPER RIDGE SHOULD BRING DRY WEATHER SUNDAY AND MONDAY.

&&

.SHORT TERM...NORTHWEST FLOW ALOFT CONTINUES OVER WESTERN
WASHINGTON THIS MORNING AHEAD OF AN UPPER RIDGE OFFSHORE NEAR
135W. A WEAK SYSTEM EMBEDDED IN THE NORTHWEST FLOW AHEAD OF THE
RIDGE IS MORE OR LESS DISSIPATING AS IT MOVES INTO WESTERN OREGON
AND NORTHERN CALIFORNIA. THERE IS A MIX OF CLOUD COVER OVER THE
FORECAST AREA AT 8 AM...WITH PATCHY FOG FROM THE SOUTH PUGET SOUND
AREA SOUTHWARD TO AROUND CHEHALIS...AND LOWLAND TEMPERATURES
RANGING FROM 28 AT OLYMPIA TO 41 AT FRIDAY HARBOR.

NORTHWEST FLOW ALOFT WILL CONTINUE TODAY AS THE UPPER RIDGE MOVES
SLOWLY EASTWARD TOWARD 130W. ANOTHER WEAK SHORTWAVE EMBEDDED IN
THE NORTHWEST FLOW WILL MOVE INTO THE OFFSHORE WATERS...BUT
WESTERN WASHINGTON SHOULD REMAIN ESSENTIALLY DRY. IT SHOULD BE A
PARTLY SUNNY DAY WITH HIGHS IN THE MID TO UPPER 40S.

THE UPPER RIDGE WILL MOVE TO THE COAST TONIGHT AND INLAND EARLY
WEDNESDAY. THE NEXT FRONTAL SYSTEM WILL FOLLOW JUST BEHIND THE
RIDGE...WITH PRECIPITATION PROBABLY SPREADING INLAND ACROSS THE
FORECAST AREA WEDNESDAY AFTERNOON. A WEAK POST-FRONTAL UPPER
TROUGH WILL MOVE THROUGH WEDNESDAY NIGHT. THE FRONT AND UPPER
TROUGH SHOULD BRING UP TO 0.5 INCH RAIN TO THE INTERIOR LOWLANDS.
FOR THE MOUNTAINS AMOUNTS OF 0.5 TOP 1.3 INCHES SHOULD BE COMMON
WITH THE SNOW LEVEL RANGING FROM 1500 TO 3000 FT...SO MOST LIKELY
IT WILL BE A LOW-END ADVISORY EVENT. THE SYSTEM WILL PRODUCE
BREEZY TO LOCALLY WINDY CONDITIONS IN THE NORTH INTERIOR AND AT
THE COAST.

AN UPPER RIDGE WILL BUILD AS IT PROGRESSES INTO THE PACIFIC
NORTHWEST ON THURSDAY. THERE WILL BE SOME POST-FRONTAL SHOWERS
LINGERING THAT MORNING THOUGH...ESPECIALLY ALONG THE WEST SLOPES
OF THE CASCADES. AND A WEAK WARM FRONT IMMEDIATELY UPSTREAM OF THE
RIDGE AXIS COULD BRING STRATIFORM PRECIPITATION BACK TO THE
FORECAST AREA IN THE AFTERNOON. MCDONNAL

.LONG TERM...THE NEXT FRONTAL SYSTEM WILL MOVE THROUGH WESTERN
WASHINGTON FRIDAY AND FRIDAY NIGHT. IT LOOKS LIKE A SOMEWHAT
STRONGER...WETTER...AND WARMER. BUT IT IS NOT A SYSTEM LIKELY TO
PRODUCE STRONG WINDS OR FLOODING...EVEN ON THE SKOKOMISH RIVER.
THE SNOW LEVEL WILL PROBABLY RISE TO 4000 TO 5500 FT AS THE SYSTEM
MOVES THROUGH...THEN FALL TO AROUND 3000 FT SATURDAY AS POST-
FRONTAL SHOWERS TAPER OFF. MODELS ARE STILL IN GOOD AGREEMENT THAT
A STRONG UPPER RIDGE WILL BUILD OVER THE AREA SUNDAY AND MONDAY.
MCDONNAL

&&

.AVIATION...A WEAK FRONTAL SYSTEM AND ASSOCIATED UPPER
TROUGH IS DISSIPATING OVER THE COASTAL WATERS TODAY. LIGHT NW FLOW
ALOFT. THE AIR MASS IS STABLE WITH MAINLY MID AND HIGH LEVEL
MOISTURE. A STRONGER FRONTAL SYSTEM NOW WELL OFFSHORE WILL APPROACH
THE REGION LATE TONIGHT AND MOVE THROUGH THE AREA WED
AFTERNOON.

EARLY VISIBLE SATELLITE IMAGES AND OBSERVATIONS SHOW AN AREA OF FOG
AND LOW STRATUS FROM AROUND SEATTLE SOUTHWARD IN THE INTERIOR AND
THROUGH THE CHEHALIS RIVER VALLEY TO AROUND KHQM. TOPS ARE SHALLOW
AND THE FOG AND STRATUS IS EXPECTED TO BREAK OUT BY 20Z. THE
REMAINDER OF THE AFTERNOON WILL FEATURE GOOD VFR CONDITIONS WITH
ONLY MID AND HIGH LEVEL MOISTURE.

A SCT-BKN050 LAYER WILL MOVE INLAND FROM ABOUT KSEA SOUTHWARD AFTER
03Z AS THE REMNANTS OF THE DISSIPATING FRONTAL SYSTEM ALONG THE
COAST MOVE INLAND. MID AND HIGH LEVEL MOISTURE WILL LOWER AND
THICKEN STARTING 12Z WED AS THE NEXT STRONGER FRONTAL SYSTEM
APPROACHES THE COAST. ALBRECHT

KSEA...STRATUS WITH BASES AROUND 003 AND TOPS 004 HAVE FORMED IN THE
VALLEYS AROUND THE TERMINAL AND AT KBFI. THESE WILL SCATTER OUT
AROUND 20Z...BUT THERE IS A 30 PERCENT CHANCE THAT THERE COULD BE
SOME BRIEF VISIBILITY RESTRICTIONS AT THE TERMINAL UNTIL 20Z AS THE
STRATUS LIFTS AND SCATTERS. FROM 20Z THROUGH TONIGHT EXPECT P6SM
WITH SCT-BKN LAYERS ABOVE 120. A SCT-BKN050 LAYER WILL BE AROUND THE
TERMINAL AFTER 04Z TONIGHT. SE WIND 3-5 KT WILL INCREASE TO 5 TO 9
KT TONIGHT AND WED MORNING. ALBRECHT

&&

.MARINE...A WEAK FRONTAL SYSTEM OVER THE COASTAL WATERS WILL
DISSIPATE BEFORE IT MOVES ONSHORE TONIGHT. A STRONGER FRONTAL SYSTEM
NOW OVER THE EASTERN PACIFIC AROUND 140W WILL MOVE THROUGH THE
COASTAL WATERS WED AFTERNOON AND THROUGH THE INLAND WATERS EARLY WED
EVENING. LOW END SMALL CRAFT ADVISORIES ARE IN EFFECT FOR THE OUTER
COASTAL WATERS THIS AFTERNOON AND FOR THE INNER COASTAL WATERS AND
WEST ENTRANCE TO THE STRAIT FOR TONIGHT. THESE ADVISORIES ARE FOR
THE COMBINATION OF THE DISSIPATING FIRST FRONT AND THE INCREASE IN
SELY PRES GRADIENTS EXPECTED TONIGHT AS THE OFFSHORE FRONT
APPROACHES.

WEDNESDAYS FRONT IS STRONGER AND WILL GIVE GALE FORCE WINDS TO THE
OUTER COASTAL WATERS. IT APPEARS THAT WINDS OVER THE INNER WATERS
WILL REMAIN JUST BELOW GALE FORCE AS THE FRONT SPLITS AND WEAKENS AS
IT MOVES TOWARD THE COASTLINE. SMALL CRAFT ADVISORIES WERE ISSUED
FOR THE EAST ENTRANCE TO THE STRAIT...ADMIRALTY INLET...AND THE
NORTHERN INLAND WATERS FOR WEDNESDAY AND A GALE WATCH REMAINS IN
EFFECT FOR THE EAST ENTRANCE TO THE STRAIT AND CENTRAL STRAIT OF
JUAN DE FUCA WEDNESDAY AFTERNOON. THE WINDS IN THESE INLAND WATERS
WILL BE THE RESULT OF THE INTERACTIONS OF WINDS ALOFT INTERACTING
WITH THE OLYMPIC MOUNTAINS AND PRODUCING A MESOSCALE LOW PRESSURE
SYSTEM AROUND THE NORTHEASTERN OLYMPIC PENINSULA. GALE FORCE WINDS
ARE POSSIBLE WED AFTERNOON AROUND THE EASTERN PORTIONS OF THE
STRAIT...BUT ARE NOT A CERTAINTY.

LIGHTER WINDS ARE EXPECTED THURSDAY AS A WEAK RIDGE OF HIGH PRES
MOVES ACROSS THE AREA. THE A STRONGER FRONTAL SYSTEM WILL MOVE INTO
THE COASTAL WATERS LATE THU NIGHT OR FRI. GALES ARE EXPECTED AHEAD
OF FRIDAYS FRONT OVER THE COASTAL WATERS AND MAY OCCUR AT THE
ENTRANCES TO THE STRAIT AND IN THE NORTHERN INLAND WATERS. OTHER
WATERS WILL LIKELY SEE SMALL CRAFT ADVISORY CONDITIONS.  ALBRECHT

&&

.HYDROLOGY...RIVER FLOODING IS NOT EXPECTED THE NEXT 7 DAYS.

&&

.SEW WATCHES/WARNINGS/ADVISORIES...
WA...HIGH SURF ADVISORY FROM MIDNIGHT WEDNESDAY NIGHT TO 6 PM PST
     THURSDAY FOR CENTRAL COAST.

PZ...SMALL CRAFT ADVISORY UNTIL 1 AM PST WEDNESDAY 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-
     COASTAL WATERS FROM POINT GRENVILLE TO CAPE SHOALWATER 10
     TO 60 NM.

     GALE WARNING FROM 1 AM TO 4 PM PST WEDNESDAY 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-
     COASTAL WATERS FROM POINT GRENVILLE TO CAPE SHOALWATER 10
     TO 60 NM.

     SMALL CRAFT ADVISORY UNTIL 4 PM PST WEDNESDAY FOR COASTAL WATERS
     FROM CAPE FLATTERY TO JAMES ISLAND OUT 10 NM.

     SMALL CRAFT ADVISORY FROM 1 AM TO 4 PM PST WEDNESDAY FOR COASTAL
     WATERS FROM JAMES ISLAND TO POINT GRENVILLE OUT 10 NM-
     COASTAL WATERS FROM POINT GRENVILLE TO CAPE SHOALWATER OUT
     10 NM.

     GALE WATCH WEDNESDAY AFTERNOON FOR CENTRAL U.S. WATERS STRAIT OF
     JUAN DE FUCA-EAST ENTRANCE U.S. WATERS STRAIT OF JUAN DE
     FUCA.

     SMALL CRAFT ADVISORY FROM MIDNIGHT TONIGHT TO NOON PST WEDNESDAY
     FOR EAST ENTRANCE U.S. WATERS STRAIT OF JUAN DE FUCA.

     SMALL CRAFT ADVISORY FROM 3 AM TO 4 PM PST WEDNESDAY FOR
     NORTHERN INLAND WATERS INCLUDING THE SAN JUAN ISLANDS.

     SMALL CRAFT ADVISORY FROM MIDNIGHT TONIGHT TO 4 PM PST WEDNESDAY
     FOR ADMIRALTY INLET.

&&

$$

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