High Wind in Washington, December 6 to 7, 2015

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE PORTLAND OR
501 PM PST SUN DEC  6 2015

.SYNOPSIS...A SERIES OF STRONG AND MOIST PACIFIC FRONTAL SYSTEMS WILL
CONTINUE TO LASH SOUTHWEST WASHINGTON AND NORTHWEST OREGON WITH
PERIODS OF HEAVY RAIN...STRONG WINDS...AND HEAVY SURF FOR MUCH OF THE
UPCOMING WEEK. RAIN AND COASTAL WIND ARE ALREADY DEVELOPING WITH THE
ARRIVAL OF OUR LATEST FRONTAL SYSTEM...BOTH ARE EXPECTED TO INCREASE
TONIGHT AND MONDAY AS THE FRONT PUSHES SLOWLY SOUTH THROUGH THE
FORECAST AREA. THE FRONTAL ZONE IS THEN EXPECTED TO STALL AND LIFT
BACK NORTHWARD MONDAY NIGHT...BEFORE THE NEXT LOW PRESSURE SYSTEM
FORCES THE FRONT BACK SOUTHWARD FOR MORE HEAVY RAIN AND STRONG WIND
TUESDAY OR TUESDAY NIGHT. ADDITIONAL STORM SYSTEMS WILL LIKELY BRING
MORE WET AND WINDY WEATHER AS THE WEEK PROGRESSES. HIGH SURF CAN BE
EXPECTED AT TIMES ALONG THE COAST...WITH MINOR COASTAL FLOODING
POSSIBLE. IT IS ALSO APPEARING INCREASINGLY LIKELY THAT THERE WILL
BE ENOUGH RAIN TO CAUSE SOME FLOODING...ALTHOUGH THE DETAILS ON
EXACTLY WHERE AND WHEN REMAIN A BIT UNCERTAIN.

&&

.SHORT TERM...TONIGHT THROUGH MONDAY...THE LATEST IN A SERIES OF
FRONTAL SYSTEMS IS ALREADY BEGINNING TO AFFECT SW WASHINGTON AND NW
OREGON WITH LIGHT RAIN AND SOME GUSTY COASTAL WINDS...WITH KRTX/KLGX
RADAR SHOWING WEAK ECHOES SPREADING ACROSS MUCH OF THE FORECAST AREA.
THOSE NWS DOPPLER RADARS ARE ALSO INDICATING SOME STRONG WINDS JUST
ABOVE THE SURFACE...WITH KLGX INDICATING 60-70 KT WINDS SOME 2000 TO
3000 FT ABOVE THE SURFACE. ESRL PROFILER AT ASTORIA PAINTS A VERY
SIMILAR PICTURE WITH 45-55 KT WINDS AS LOW AS 500M OFF THE
SURFACE...AND CAPE MEARES IS ALREADY GUSTING TO 64 MPH. OVERALL THIS
COASTAL HIGH WIND WARNING LOOKS TO BE IN GOOD SHAPE...A BIT BETTER
THAN THE ONE WHICH STRUGGLED TO VERIFY YESTERDAY.

SYSTEMS ARE MOVING FAST AND FURIOUS ACROSS THE PACIFIC...BEING
CARRIED ALONG BY A GOES-ESTIMATED 185 KT JET WHICH TRAVERSES NEARLY
THE WHOLE BASIN BACK TO THE PHILIPPINES. THESE SYSTEMS HAVE PLENTY OF
BAROCLINICITY AVAILABLE TO THEM...WHICH COMBINED WITH THE POWERFUL
JET IS CREATING A POWDER KEG OF POTENTIAL FOR CYCLOGENESIS THE NEXT
FEW DAYS OFFSHORE. ALL THESE FEATURES WILL ALSO MAKE FORECASTING
ANYTHING BEYOND 24-36 HOURS VERY CHALLENGING WHILE THIS PATTERN IS IN
PLACE...AS SMALL ERRORS IN INITIALIZATION CAN LEAD TO VERY LARGE
ERRORS IN A SHORT PERIOD OF TIME.

THAT SAID...MODELS HAVE HAD A RELATIVELY VERY GOOD HANDLE ON THE
PROGRESSION OF TONIGHT AND MONDAY...EVEN TUESDAY WITH THE PAST FEW
MODEL RUNS. THE MAIN STRUGGLE TODAY HAS BEEN DETERMINING THE LOCATION
OF THE MAIN INTEGRATED VAPOR TRANSPORT AXIS TONIGHT AND
MONDAY...WHICH WILL HAVE HUGE IMPLICATIONS ON WHICH RIVERS WILL FLOOD
BY MONDAY. EARLIER GUIDANCE HAD A FAIRLY HIGH CONFIDENCE FORECAST
THAT THE GRAYS WOULD FLOOD LATE TONIGHT...BUT 18Z MODELS TOOK THE
NORTHERN EXTENT OF THE IVT AXIS A LITTLE FURTHER SOUTH SO WE DECIDED
NOT TO ISSUE A FLOOD WARNING FOR THE GRAYS YET. HOWEVER THIS WOULD
PROBABLY PUT MORE EMPHASIS ON THE NORTH OREGON COASTAL DRAINAGES...
WITH THE POTENTIAL FOR 3-7 INCHES OF RAIN TONIGHT AND MONDAY.
SIMILAR TOTALS ARE LIKELY FOR THE S WA CASCADES AND PROBABLY THE N
OR CASCADES AS WELL.

IF THE FRONT STAYS NEAR OR A BIT SOUTH OF THE WA/OR BORDER AS THE 18Z
GFS/NAM AND EVEN SOMEWHAT THE 12Z ECMWF SUGGEST...IT COULD SET UP A
SITUATION WHERE A VIGOROUS UPPER LEVEL SHORTWAVE AND WEAK SURFACE
REFLECTION RIDE ALONG THE FRONT...DOING TWO IMPORTANT THINGS.
FIRST...IT WOULD ENHANCE THE SOUTH-NORTH PRESSURE GRADIENTS ALONG THE
COAST AND IN THE WILLAMETTE VALLEY SOUTH OF THE FRONT. SECOND...IT
COULD PROVIDE A ZONE OF VERY STRONG FRONTOGENESIS AND VERY HEAVY RAIN
EVEN FOR THE LOWLANDS MONDAY...WITH 1-2 INCHES OF RAIN POSSIBLE IN A
SHORT PERIOD...ALMOST SIMILAR TO WHAT HAPPENED HALLOWEEN AFTERNOON.
FOR NOW WE KEPT THE HEAVIEST RAIN IN THE HIGHER TERRAIN...BUT WILL
NEED TO WATCH THE POTENTIAL FOR A VERY WET AFTERNOON EVEN FOR THE
PORTLAND/VANCOUVER METRO. OUR FORECAST PRESENTLY KEEPS THIS FRONTAL
ZONE A LITTLE FURTHER TO THE NORTH... WHICH WOULD KEEP THE ENTIRE
WILLAMETTE VALLEY OPEN TO STRONG MIXING FOR THE 40-50 KT WINDS JUST
ABOVE THE SURFACE MONDAY. THIS WILL LIKELY BRING 40-50 MPH GUSTS TO
SALEM AND EUGENE...WITH A LITTLE LOWER CONFIDENCE OF THOSE GUSTS
REACHING THE PDX METRO. THERE MAY ALSO BE A CONVECTIVE ELEMENT TO THE
WIND GUSTS MON AFTERNOON AS A STRONG UPPER-LEVEL SHORTWAVE RIDES EAST
ALONG THE FRONT.

THERE ARE NUMEROUS WATCHES WARNINGS AND ADVISORIES POSTED...BUT THE
MOST WIDESPREAD IMPACT WILL LIKELY BE URBAN...SMALL STREAM...AND
RIVER FLOODING THE NEXT FEW DAYS. A CLOSE SECOND WILL BE WINDS...
WHICH WILL BE FAIRLY WIDESPREAD NOT JUST MONDAY BUT POTENTIALLY
TUE/TUE NIGHT. THIS STORMY PATTERN IS ALSO WHIPPING UP ANGRY SEAS
ACROSS MUCH OF THE NE PAC...WHICH WILL LEAD TO 25-35 FT SEAS AND
MINOR COASTAL FLOODING AT TIMES. STAY TUNED AS THIS IS A VERY DYNAMIC
FORECAST AND MANY CHANGES WILL LIKELY BE MADE OVER THE COMING DAYS.
WEAGLE

.MONDAY NIGHT THROUGH WEDNESDAY...MONDAYS STORM SYSTEM WILL SLOWLY
DISSIPATE ACROSS LANE COUNTY AND POINTS SOUTHWARD MONDAY EVENING
BEFORE LIFTING NORTHWARD MONDAY NIGHT AND BRINGING A ROUND OF LIGHT
RAIN TO THE REGION.

THE MAIN SHOW WILL ARRIVE ON TUESDAY AS A STORM SYSTEM CURRENTLY OUT
NEAR THE DATELINE IN THE CENTRAL PACIFIC BRINGS ANOTHER ROUND OF
SIGNIFICANT RAIN...AND SOME BREEZY TO LOCALLY WINDY CONDITIONS TO
NORTHWEST OREGON AND SOUTHWEST WASHINGTON. A FRONT WILL SLOWLY
TRAVERSE SOUTHEASTWARD ACROSS THE AREA BETWEEN TUESDAY AFTERNOON
THROUGH WEDNESDAY MORNING. IVT VALUES IN EXCESS OF 750 KG/MS WILL BE
ORIENTED MORE PERPENDICULAR THAN PARALLEL TO THE COASTLINE...WHICH
SHOULD AID IN PLENTY OF OROGRAPHIC RAIN ENHANCEMENT IN THE COAST
RANGE AND CASCADES. NAEFS RETURN INTERVALS SUGGESTS THESE IVT VALUES
OCCUR ONCE EVERY 5 TO 10 YEARS THIS TIME OF YEAR IN OUR REGION.
GIVEN THESE VALUES WILL PERSIST FOR A 9 TO 15 HOUR PERIOD...
CONFIDENCE IS GROWING THAT THIS WILL BE A SIGNIFICANT RAIN EVENT AND
POSSIBLY A SIGNIFICANT FLOOD EVENT...ESPECIALLY CONSIDERING IT WILL
BE ON THE HEELS OF TONIGHTS/MONDAYS WET WEATHER.

GLOBAL MODELS APPEAR TO BE COMING INTO AGREEMENT THE REGION MAY
TEMPORARILY DRY OUT WEDNESDAY AS SHORTWAVE RIDGING BUILDS OVER THE
PACIFIC NORTHWEST AHEAD OF A DEVELOPING LOW PRESSURE SYSTEM
OFFSHORE. POPS AND QPF WERE TRENDED DOWNWARD...BUT ARE ADMITTEDLY
STILL NEAR TO ABOVE CLIMO FOR THIS PERIOD...WITH ADDITIONAL
DECREASES LIKELY IF MODEL CONSISTENCY CONTINUES. /NEUMAN

.LONG TERM...WEDNESDAY NIGHT THROUGH SUNDAY...MODELS ARE IN GOOD
AGREEMENT THAT AN ACTIVE WEATHER PATTERN WILL CONTINUE INTO NEXT
WEEKEND. AS A RESULT...POPS WERE GENERALLY PLACED NEAR TO ABOVE
CLIMO FOR MOST OF THE EXTENDED PERIOD. THE EC AND GFS HAVE COME INTO
BETTER AGREEMENT EARLY IN THE EXTENDED PERIOD...BOTH DEPICTING A
DEEP LOW PRESSURE...APPROXIMATELY 970MB...MOVING NORTHEASTWARD
TOWARDS THE NORTHERN TIP OF VANCOUVER ISLAND. THE ATTENDANT
OCCLUSION WILL MOVE EASTWARD INTO THE REGION AND BRING ANOTHER ROUND
OF RAIN...AND POSSIBLY SOME WINDY CONDITIONS TO THE REGION WEDNESDAY
NIGHT AND THURSDAY. MODELS HAVE FLUCTUATED SOMEWHAT WILDLY ON HOW
THEY HANDLE THIS SYSTEM OVER THE PAST SEVERAL MODEL RUNS SO
CONFIDENCE IS STILL FAIRLY LOW IN HOW THIS SYSTEM WILL IMPACT THE
REGION.

EITHER WAY...SNOW LEVELS SHOULD DROP FAIRLY QUICKLY INTO THE 3500-
4000 FT RANGE BEHIND THE FRONT ON THURSDAY AND FRIDAY. DEPENDING ON
THE TRACK OF THE LOW PRESSURE...THE CASCADES MAY END UP WITH SOME
DECENT SNOW DURING THIS PERIOD. MODELS SEEM TO BE TRENDING TOWARDS
THE IDEA THAT THE AREA MAY TEMPORARILY DRY OUT LATE FRIDAY BEFORE
ANOTHER STORM SYSTEM HITS THE PACIFIC NORTHWEST SATURDAY-ISH.
/NEUMAN

&&

.AVIATION...A WARM FRONT MOVING EASTWARD INTO THE REGION THIS
AFTERNOON AND EVENING WILL RESULT IN THE PREDOMINANTLY VFR
CONDITIONS CURRENTLY FOUND ACROSS MOST OF THE REGION TO TREND
TOWARDS PREDOMINANTLY MVFR CONDITIONS BETWEEN 06Z TO 12Z MONDAY.
COASTAL LOCATIONS WILL LIKELY SEE OFF AN ON IFR CONDITIONS BETWEEN
09Z TO 18Z MONDAY...ESPECIALLY AT KONP. STRONG SOUTH WIND GUSTS OF
45 TO 50 KT APPEAR PROBABLE AT COASTAL TAF SITES...ESPECIALLY
KONP...BETWEEN APPROXIMATELY 03Z TO 12Z MONDAY. GUSTY SOUTH WINDS
THIS EVENING MAY NUDGE DOWNWARD A TOUCH OVERNIGHT BEFORE INCREASING
AGAIN MONDAY AFTERNOON. THESE BREEZIER CONDITIONS SHOULD HELP KEEP
TAF SITES WITH A MIX OF MVFR AND VFR CONDITIONS IN THE WILLAMETTE
VALLEY. WITH THAT SAID...THERE IS SOME CONCERN THAT IFR CONDITIONS
COULD DEVELOP FOR A SEVERAL HOUR PERIOD AROUND 09Z AND THEN AGAIN
AROUND 18Z MONDAY FOR THE PORTLAND METRO TAF SITES. KHIO WILL BE
MOST SUSCEPTIBLE.

KPDX AND APPROACHES...A WARM FRONT MOVING EASTWARD INTO THE REGION
WILL RESULT IN GRADUALLY LOWERING CIGS THIS EVENING WITH STEADIER
RAIN ARRIVING BETWEEN 00Z AND 02Z MONDAY. CONDITIONS SHOULD
EVENTUALLY DETERIORATE INTO MVFR CONDITIONS OVERNIGHT...LIKELY
AROUND 06Z MONDAY. SOUTH TO SOUTHEAST WINDS SHOULD BE STRONG ENOUGH
TO KEEP CONDITIONS FROM DETERIORATING FURTHER INTO IFR CONDITIONS
BETWEEN 09Z AND 18Z MONDAY...BUT CONFIDENCE IS NOT TERRIBLY HIGH
THAT THE TERMINAL WILL NOT SEE A PERIOD OF IFR CONDITIONS EITHER.
THE MOST LIKELY PERIODS TO EXPERIENCE IFR CONDITIONS WILL BE AROUND
09Z AND THEN AGAIN AROUND 18Z MONDAY. /NEUMAN

&&

.MARINE...A SERIES OF STRONG FRONTAL SYSTEMS WILL CONTINUE TO
IMPACT THE COASTAL WATERS THROUGH THIS WEEKEND FOR A VERY STORMY
PERIOD WITH ONLY BRIEF BREAKS BETWEEN SYSTEMS.

WINDS AND SEAS ARE INCREASING LATE THIS AFTERNOON AHEAD OF THE
FRONT APPROACHING THE WATERS. THE 18Z NAM AND GFS MODEL RUN WAS
FASTER IN BRINGING THE FRONT TROUGH THE WATERS FORM THE NORTH SO I
HAVE MOVED UP THE TIMING A BIT. HOWEVER THE 12Z ECMWF HAD A
SLIGHTLY SLOWER TIMING. THIS WILL MAKE A BIG DIFFERENCE ALONG THE
SOUTH WASHINGTON COAST AND THE EXTREME NORTH OREGON COAST. THE
QUESTION IS WILL THE WINDS DROP OFF AFTER MIDNIGHT ALONG THE
COAST. I DO EXPECT THE WINDS TO SHIFT SLIGHTLY AND DROP BEHIND THE
FRONT OVER THE NORTHWEST PORTION OF THE OFFSHORE COASTAL WATERS
NORTH OF CAPE MEARS AFTER MIDNIGHT...WITH THE FRONT SLOWING AS
FRONTAL WAVES MOVE NORTH. THE GRADIENT SHIFTS TO MORE SOUTHERLY
AND THIS ALLOWS THE STRONGER WINDS TO REACH ALL THE WAY TO THE
BEACHES MONDAY MORNING. THE FRONT WILL SLOWLY SHIFT SOUTH MONDAY.

ANOTHER WARM FRONT IS EXPECTED LATE MONDAY NIGHT AND TUESDAY...BUT
NOT QUITE AS STRONG AS TONIGHTS SYSTEM. HOWEVER THE MODELS DO SHOW
STRONGER WINDS PROCEEDING THE SOLD FRONT TUESDAY NIGHT. THERE
SHOULD BE A BRIEF BREAK IN SYSTEMS WEDNESDAY AFTERNOON AND
EVENING...BEFORE A LOW MOVES OUT OF THE GULF OF ALASKA THURSDAY
NIGHT WITH ASSOCIATED FRONT MOVING OVER THE WATERS.

SEAS WILL CONTINUE TO INCREASE WITH A WESTERLY SWELL FRONT THE
GULF MOVING IN AND THE SOUTHERLY FRESH SWELL ASSOCIATED WITH THE
WINDS AHEAD OF THE FRONT TONIGHT. EXPECT PEAK SEAS AROUND 30 TO 33
FEET LATE TONIGHT AND WILL DIMINISH SOME...MONDAY MORNING ESPECIALLY
OVER THE OUTER THE NORTH OUTER WATERS WHEN THE WINDS DROP OFF
BEHIND THE FRONT.

AS THE WESTERLY SWELL INCREASES TONIGHT SEAS ON COLUMBIA RIVER
BAR WILL BE INCREASINGLY HAZARDOUS REACHING 25 FT AFTER MIDNIGHT
MONDAY MORNING. THERE WILL BE BREAKERS DURING THE EBBS WHICH WILL
ACTUALLY KEEP THE OVERALL WAVE HEIGHTS FROM INCREASING FURTHER
DURING THE EBBS...A VERY HAZARDOUS SITUATION.

THE WESTERLY SWELL WILL PROBABLY ARRIVE DURING THE LOWER PART OF
THE TIDAL CYCLE SO COASTAL FLOODING DOES NOT APPEAR TO BE AN
ISSUE MONDAY...BUT WE MAY HAVE MINOR TIDAL OVERFLOW IN THE
ESTUARIES WITH HIGHER RIVER FLOWS IMPEDING THE OUTFLOW. THE TIDAL
CYCLE WILL INCREASE EACH DAY THROUGH THURSDAY WITH MINOR OVERFLOW
EACH DAY AROUND 11 AM RESULTING IN FLOODING OVER TIDAL FLOOD PRONE
AREAS. HAVE ISSUED A COASTAL FLOOD ADVISORY FOR THIS CONDITION.

A LARGER SWELL WILL ARRIVE FROM THE GULF OF ALASKA ON
THURSDAY. WITH INCREASING TIDES AND AN INCREASING TIDAL ANOMALY
DUE TO THE LONG FETCH OF STORMS PUSHING THE WATER UP ALONG THE
NORTHWEST COAST...THERE IS AN INCREASING CHANCE OF COASTAL
FLOODING AND AT A MINIMUM HIGH SURF THURSDAY.

SCHNEIDER

&&

.PQR WATCHES/WARNINGS/ADVISORIES...
OR...FLOOD WATCH FROM 10 PM PST THIS EVENING THROUGH WEDNESDAY
     AFTERNOON FOR CENTRAL COAST RANGE OF WESTERN OREGON-CENTRAL
     COLUMBIA RIVER GORGE-CENTRAL OREGON COAST-CENTRAL
     WILLAMETTE VALLEY-COAST RANGE OF NORTHWEST OREGON-GREATER
     PORTLAND METRO AREA-LOWER COLUMBIA-NORTH OREGON COAST-
     NORTHERN OREGON CASCADE FOOTHILLS-NORTHERN OREGON CASCADES-
     SOUTH WILLAMETTE VALLEY-UPPER HOOD RIVER VALLEY-WESTERN
     COLUMBIA RIVER GORGE.

     WIND ADVISORY FROM 6 AM TO 6 PM PST MONDAY FOR CENTRAL
     WILLAMETTE VALLEY-GREATER PORTLAND METRO AREA-SOUTH
     WILLAMETTE VALLEY.

     HIGH WIND WARNING UNTIL 3 PM PST MONDAY FOR CENTRAL COAST RANGE
     OF WESTERN OREGON-CENTRAL OREGON COAST-COAST RANGE OF
     NORTHWEST OREGON-NORTH OREGON COAST.

     HIGH SURF ADVISORY FROM 7 PM THIS EVENING TO 9 AM PST MONDAY
     FOR CENTRAL OREGON COAST-NORTH OREGON COAST.

     COASTAL FLOOD ADVISORY FROM 8 AM TO 1 PM PST MONDAY FOR CENTRAL
     OREGON COAST-NORTH OREGON COAST.

     COASTAL FLOOD ADVISORY FROM 8 AM TO 1 PM PST TUESDAY FOR
     CENTRAL OREGON COAST-NORTH OREGON COAST.

     COASTAL FLOOD ADVISORY FROM 8 AM TO 1 PM PST WEDNESDAY FOR
     CENTRAL OREGON COAST-NORTH OREGON COAST.

WA...FLOOD WATCH FROM 10 PM PST THIS EVENING THROUGH WEDNESDAY
     AFTERNOON FOR CENTRAL COLUMBIA RIVER GORGE-GREATER
     VANCOUVER AREA-I-5 CORRIDOR IN COWLITZ COUNTY-SOUTH
     WASHINGTON CASCADE FOOTHILLS-SOUTH WASHINGTON CASCADES-
     SOUTH WASHINGTON COAST-WESTERN COLUMBIA RIVER GORGE-WILLAPA
     HILLS.

     WIND ADVISORY FROM 6 AM TO 6 PM PST MONDAY FOR GREATER
     VANCOUVER AREA.

     HIGH WIND WARNING UNTIL 3 PM PST MONDAY FOR SOUTH WASHINGTON
     COAST-WILLAPA HILLS.

     HIGH SURF ADVISORY FROM 7 PM THIS EVENING TO 9 AM PST MONDAY
     FOR SOUTH WASHINGTON COAST.

     COASTAL FLOOD ADVISORY FROM 8 AM TO 1 PM PST MONDAY FOR SOUTH
     WASHINGTON COAST.

     COASTAL FLOOD ADVISORY FROM 8 AM TO 1 PM PST TUESDAY FOR SOUTH
     WASHINGTON COAST.

     COASTAL FLOOD ADVISORY FROM 8 AM TO 1 PM PST WEDNESDAY FOR
     SOUTH WASHINGTON COAST.

PZ...STORM WARNING UNTIL 1 PM PST MONDAY FOR COASTAL WATERS FROM
     CAPE SHOALWATER WA TO FLORENCE OR OUT 60 NM.

     GALE WARNING UNTIL 5 PM PST THIS AFTERNOON FOR COASTAL WATERS
     FROM CAPE SHOALWATER WA TO FLORENCE OR OUT 60 NM.

     SMALL CRAFT ADVISORY FOR ROUGH COLUMBIA RIVER BAR UNTIL 4 PM
     PST MONDAY.

&&

INTERACT WITH US VIA SOCIAL MEDIA
WWW.FACEBOOK.COM/NWSPORTLAND
WWW.TWITTER.COM/NWSPORTLAND

THIS DISCUSSION IS FOR NORTHWEST OREGON AND SOUTHWEST WASHINGTON
FROM THE CASCADE CREST TO 60 NAUTICAL MILES OFFSHORE. THE AREA IS
COMMONLY REFERRED TO AS THE FORECAST AREA.