High Wind in Washington, December 6, 2015

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SEATTLE WA
310 PM PST SUN DEC 6 2015

.SYNOPSIS...A SERIES OF STRONG PACIFIC FRONTAL SYSTEMS WILL MOVE
THROUGH WESTERN WASHINGTON INTO TUESDAY NIGHT. THESE SYSTEMS WILL
CONTINUE TO BRING COPIOUS AMOUNTS OF RAINFALL ACROSS WESTERN
WASHINGTON AND PERIODS OF WINDY WEATHER PRIMARILY FOR THE COAST AND
NORTH INTERIOR ALONG WITH ACTIVE SURF ON THE BEACHES. A COOLER YET
STILL ACTIVE WEATHER PATTERN IS LIKELY THE REST OF THE WEEK AND
INTO THE WEEKEND.

&&

.SHORT TERM...THE STRONG ZONAL FLOW WITH A WESTERLY JETSTREAM IN
EXCESS OF 180 KNOTS CONTINUES ACROSS THE NORTHERN PACIFIC. EMBEDDED
SHORTWAVES ARE JUST FLYING ALONG IN THE STRONG FLOW. THE NEXT
SHORTWAVE WAS SPREADING RENEWED RAIN INTO THE COASTAL REGION EARLY
THIS AFTERNOON AND SHOULD BE INTO THE INTERIOR BY THIS EVENING. THE
STAMPEDE OF SHORTWAVES WILL CONTINUE INTO MONDAY AND TUESDAY WITH
PERIODS OF RAIN AND WINDY CONDITIONS FOR PRIMARILY THE COAST AND
NORTH INTERIOR.

EACH INCOMING SYSTEM IS BRINGING MORE MILD AIR ONSHORE. TEMPERATURES
TO REMAIN QUITE MILD FOR EARLY DECEMBER MONDAY AND TUESDAY. IN
COLLABORATION WITH THE NW AVALANCHE CENTER...SNOW LEVELS TO ALSO
CONTINUE TO CREEP UP...CLIMBING TO 5000 TO 7000 FT MONDAY AND
PERHAPS AS HIGH AS 8000 FT TUESDAY.

LETS BREAK THIS DOWN SITUATION DOWN FURTHER...GRAB YOUR SCORECARD.
NEXT - WIND. THE INCOMING SYSTEM THIS EVENING IS TIGHTENING UP
PRESSURE GRADIENTS ALONG THE COAST AND NORTH INTERIOR IN A CLASSIC
SOUTHEAST SUCKER PATTERN. THE ISOBAR ORIENTATION IS SUCH THAT MUCH
LIGHTER WINDS TO OCCUR FROM ABOUT EVERETT SOUTHWARD WHILE THE COAST
AND NORTH INTERIOR BLOW. WINDS WERE PICKING THIS AFTERNOON. A HIGH
WIND WARNING REMAINS IN PLACE WITH THE STRONGEST WINDS LIKELY THIS
EVENING. THE FOLLOWING SYSTEMS SHOULD MAINTAIN SIMILAR ISOBAR
ORIENTATION AND WINDY CONDITIONS AS THEY SWING ONSHORE YET AT THIS
POINT...NOT QUITE BLOWING AS STRONG.

FOR THE RIVERS AND LANDSLIDE THREAT...SEE THE HYDRO SECTION BELOW.
BUEHNER

.LONG TERM...THE ANTICIPATED TRANSITION TO A COOLER PATTERN STARTING
WEDNESDAY STILL LOOKS ON TRACK AS THE FLOW PATTERN ACROSS THE
PACIFIC BEGINS TO AMPLIFY. THE HEIGHTS LOWER WITH THE JET AXIS
SAGGING SOUTHWARD...LEAVING WESTERN WA ON THE COOLER SIDE FOR A MORE
SHOWERY WEATHER PATTERN. TEMPS TO DROP CLOSER TO SEASONAL AVERAGES
AND SNOW LEVELS TO SAG LOWER CLOSER TO INCLUDE ALL THE PASSES. THE
LONGER RANGE GUIDANCE OFFERS SOME DIFFERING SOLUTIONS ON INCOMING
SYSTEMS...YET THE TREND IS FOR COOLER CONDITIONS WITH LIGHTER
PRECIPITATION AMOUNTS INTO THE WEEKEND. BUEHNER

&&

.AVIATION...STRONG W FLOW ALOFT OVER THE NE PACIFIC WILL DRIVE THE
NEXT STRONG OCCLUDED FRONT OVER W WA LATE THIS AFTERNOON AND THIS
EVENING. STEADY RAIN IS ALREADY SPREADING INLAND AND WILL REACH THE
PUGET SOUND REGION BEFORE SUNSET.

CIGS ACROSS W WA HAVE IMPROVED TO FAIRLY GOOD VFR THIS AFTERNOON BUT
WILL LOWER TO OVC040-050 IN RAIN THIS EVENING. CIGS WILL LIKELY DROP
TO MVFR LEVELS SOMETIME AFTER 06Z TONIGHT.

STRONG PRESSURE GRADIENTS ACROSS W WA WILL PRODUCE STRONG GUSTY
WINDS OVER PARTICULARLY THE N INTERIOR TONIGHT. WINDS WILL GRADUALLY
INCREASE THROUGH LATE AFTERNOON AND EARLY EVENING...AND WILL PEAK
LATE THIS EVENING. LOW LEVEL WINDS AROUND 2500 FEET THROUGH THE
INTERIOR WILL BE 30-40 KT WHICH COULD CREATE SOME WIND SHEAR AT
TIMES FOR LANDING AIRCRAFT.

KSEA...GOOD VFR CONDITIONS AT 23Z WILL LOWER QUICKLY TO OVC050 IN
LIGHT RAIN BY 01Z. CIGS SHOULD LOWER TO MVFR 020-030 AFTER 06Z.
SURFACE WINDS WILL REMAIN SOUTHERLY 10-20 KT WITH GUSTS TO 25 KT.
LOW LEVEL WINDS ALOFT AT 5000 FEET WILL BE SW 35 KT BECOMING S 50-60
KT 23Z-08Z. KAM

&&

.MARINE...A STRONG OCCLUDED FRONT OFFSHORE APPROACHING W WA WILL
RAISE STORM FORCE WINDS ON THE COAST AND INLAND GALES TONIGHT. THE
ASSOCIATED 987 MB LOW WILL CROSS N VANCOUVER ISLAND THIS EVENING
ABOUT THE SAME TIME AS THE FRONT CROSSES THE WA COAST.

STORM WARNINGS ARE UP FOR THE COAST AND GALES FOR MOST OF THE INLAND
WATERS. THE CENTRAL STRAIT WILL HAVE SCA WINDS OVER THE EAST PART OF
THE ZONE. MODELS SHOW PRESSURE GRADIENTS INCREASING THROUGH PUGET
SOUND THIS EVENING. WITH FERRY WINDS ALREADY REACHING 30 KT OVER N
PUGET SOUND WINDS SHOULD REACH GALE FORCE THIS EVENING PARTICULARLY
OVER THE NORTH PART OF PUGET SOUND. WINDS IN ALL AREAS WILL BEGIN
EASING BY LATE TONIGHT BEHIND THE FRONT...BUT IT MAY TAKE A WHILE
FOR WINDS TO DROP BELOW ADVISORY LEVELS.

A LARGE WESTERLY SWELL WILL ARRIVE ON THE COAST LATE THIS AFTERNOON
AND EVENING THEN CONTINUE INTO MONDAY MORNING. THE W SWELL WILL
BUILD TO 18 TO 20 FEET AT 16-17 SECONDS...PEAKING LATE THIS EVENING.
TOTAL SEAS OVER THE COASTAL WATERS WILL BE LARGER THAN THIS...AS A
16 FOOT 11 SECOND SOUTHERLY SWELL WILL BE MOVING NORTH OVER THE
COASTAL WATERS AT THE SAME TIME. COMBINED SEAS OFFSHORE WILL BE 26
TO 29 FEET...BUT THE WESTERLY SWELL WILL CONTRIBUTE TO SIGNIFICANT
SURF ALONG THE COAST. A HIGH SURF ADVISORY FOR THE COAST REMAINS IN
EFFECT FROM LATE THIS AFTERNOON THROUGH EARLY MONDAY.

THE EXTRA-TROPICAL STORM SURGE SITE INDICATES THE HIGHEST TIDES
ALONG THE COAST...BASED ON TOKE POINT...WILL BE VERY CLOSE TO THE
HIGHEST ASTRONOMICAL TIDE LEVEL MIDDAY TUESDAY AND MIDDAY WEDNESDAY.
THIS IS BECAUSE OF LARGE EXPECTED ANOMALIES OVER THE NORMAL
PREDICTED TIDE LEVEL. COASTAL SWELL COULD BE W-SW 15-18 FT DURING
THESE TWO HIGH TIDE PERIODS...WHICH MAY BE ENOUGH TO PRODUCE SOME
MINOR TIDAL OVERFLOW. BEACH EROSION COULD ALSO BE A PROBLEM WITH
WAVES RUNNING HIGHER UP BEACHES. CONFIDENCE IS LOW TO MODERATE WITH
THIS AND CONDITIONS COULD TREND LOWER. KAM

&&

.HYDROLOGY...THIS ACTION PACKED WEATHER PATTERN WITH THE SEQUENCE
OF WET SYSTEMS IS EXPECTED TO PRODUCE MORE SIGNIFICANT PRECIPITATION
TOTALS. 6 TO 12 INCHES ARE LIKELY OVER MUCH OF THE OLYMPICS AND
CASCADES FOR THE PERIOD THROUGH 4 AM WEDNESDAY. AROUND 3 TO 7 INCHES
OF RAIN IS LIKELY AT THE COAST WITH 2 TO 5 INCHES OVER MOST OF
THE INTERIOR LOWLANDS.

THESE FAST-MOVING SYSTEMS OFFER BRIEF BREAKS IN THE RAINFALL. SO
DESPITE THE IMPRESSIVE RAIN TOTALS...THE RIVERS ARE RUNNING FULL BUT
NOT EXCEEDING FLOOD STAGE...YET. THE DOWNSIDE HERE IS THAT WARMERAIR
OVER TIME SHOULD NUDGE SNOW LEVELS HIGHER INTO TUESDAY...MEANING
MORE RAIN VS SNOW IN THE MOUNTAINS.

IN CONCERT WITH THE NW RIVER FORECAST CENTER...WILL ISSUE A FLOOD
POTENTIAL OUTLOOK THIS AFTERNOON FOR THE RISING THREAT OF A NUMBER
OF RIVERS POTENTIALLY REACHING FLOOD STAGE TUESDAY NIGHT OR
WEDNESDAY. AT THIS POINT...NO SIGNIFICANT WIDESPREAD FLOODING
IS ANTICIPATED.

AT THE MOMENT...THE ONLY FLOOD WARNING IN PLACE IS ON THE SKOKOMISH
AND WITH THIS SOGGY PATTERN...THAT WILL CONTINUE THROUGH AT LEAST
MID WEEK. EACH PASSING WEATHER SYSTEM AND ITS RAINFALL WILL LIKELY
FLUCTUATE THE FLOW ABOVE FLOOD STAGE. SEE THE RIVERS/LAKES LINK
(AHPS) VIA OUR WEB PAGE FOR THE LATEST.

TO TOP IT ALL OFF...THIS WET WEATHER IS IN THE PROCESS OF THOROUGHLY
SATURATING SOILS AND RAISING THE THREAT OF LANDSLIDES. WE ARE
MONITORING THAT SITUATION AS WELL. BUEHNER/MCDONNAL

.SEW WATCHES/WARNINGS/ADVISORIES...
WA...HIGH WIND WARNING NORTH/CENTRAL COAST AND NORTH INTERIOR.

     HIGH SURF ADVISORY 4 PM THIS AFTERNOON TO 9 AM MONDAY FOR
NORTH/CENTRAL COAST.

PZ... STORM WARNING IN EFFECT THIS AFTERNOON THROUGH THIS EVENING
FOR THE COASTAL WATERS.
      GALE WARNING ALL REMAINING WATERS EXCEPT THE CENTRAL STRAIT.
      SMALL CRAFT CENTRAL STRAIT.
      SMALL CRAFT ADVISORY FOR SEVERE BAR FOR GRAYS HARBOR BAR.
&&

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