Flooding in Washington, November 17 to 18, 2015

AREA FORECAST DISCUSSION...UPDATED
NATIONAL WEATHER SERVICE PORTLAND OR
350 AM PST TUE NOV 17 2015

UPDATED AVIATION DISCUSSION

.SYNOPSIS...A SERIES OF MOIST FRONTAL SYSTEMS WILL BRING PERIODS OF
HEAVY RAIN...GUSTY WINDS...AND OCCASIONAL CASCADE SNOW TO SOUTHWEST
WASHINGTON AND NORTHWEST OREGON THE NEXT SEVERAL DAYS. THERE MAY BE A
BREAK IN PRECIPITATION FRIDAY THAT MAY CONTINUE INTO THE WEEKEND.

&&

.SHORT TERM...A WARM FRONT HAS BROUGHT PERSISTENT RAIN TO THE REGION
OVERNIGHT...WITH THE SNOW LEVELS ABOVE THE CASCADE PASSES. THE RAIN
HAS BEEN THE HEAVIEST OVER THE WILLAPA HILLS AND THE NORTH OREGON
COAST RANGE OVERNIGHT AND THERE HAS BEEN RISES IN SOME OF THE COASTAL
RIVERS. THE WARM FRONT IS LIFTING NORTH EARLY THIS MORNING...AND RAIN
RATES WILL DECREASE A BIT.

A COLD FRONT WILL THEN MOVE NORTH TO SOUTH AND INCREASE RAIN RATES
AGAIN THIS AFTERNOON AND EVENING. THE RAIN FROM THE COLD FRONT MAY BE
ENOUGH TO PUSH SOME OF THE COASTAL RIVERS JUST ABOVE FLOOD STAGE.
WE ARE CONSIDERING ISSUING A FLOOD WATCH FOR FAR SW WASHINGTON AND
FAR NW OREGON RIVERS AS ANOTHER 1 TO 3 INCHES OF RAIN CAN BE EXPECTED
FOR THE NORTHERN COAST RANGE AND CASCADES THROUGH THIS EVENING.
RAINFALL TOTALS OF 0.5 TO 1 INCH CAN BE EXPECTED FOR THE NORTHERN
INTERIOR LOW LANDS AND LESS THAN 0.5 INCH FOR THE SOUTHERN INTERIOR
LOW LANDS. THE RAIN MAY BE HEAVY AT TIMES AND RESULT IN PONDING IN
POOR DRAINING AREAS.

THE SURFACE PRESSURE GRADIENT WILL TIGHTEN TODAY AND EXPECT STRONG
GUSTY WINDS THROUGH THIS EVENING. THE STRONGEST GUSTS ARE EXPECTED
FOR THE COAST...COAST RANGE AND THE CASCADES MID TO LATE AFTERNOON
THROUGH THE EARLY EVENING...AND HAVE CONTINUED THE HIGH WIND
WARNING FOR THE S WA AND N OREGON COAST...THE WILLAPA HILLS AND N
OREGON COAST RANGE. THE CASCADES WILL HAVE LOCALIZED WINDS MEETING
WARNING CRITERIA AT THE HIGHEST ELEVATIONS BUT WILL NOT BE
WIDESPREAD.

BESIDES STRONG GUSTY WINDS...BEACHES WILL HAVE THE ADDITIONAL HAZARD
OF DANGEROUS BREAKING WAVES. THOSE PLANNING ON HEADING TO THE BEACH
DURING BREAKS IN THE RAIN MAY WANT TO KEEP THEIR DISTANCE FROM THE
WATERS EDGE.

THE RAIN WILL TURN TO SHOWERS BEHIND THE COLD FRONT LATE TONIGHT.
COLDER AIR MOVING IN BEHIND THE FRONT WILL LOWER SNOW LEVELS DOWN TO
3000 FEET FOR THE WASHINGTON CASCADES EARLY WEDNESDAY MORNING AND TO
AROUND 4000 FEET FOR THE LANE COUNTY CASCADES. EXPECT MAINLY ISOLATED
RAIN AND MOUNTAIN SNOW SHOWERS WEDNESDAY WITH LITTLE ACCUMULATIONS.

ANOTHER MOIST WARM FRONT WILL APPROACH WEDNESDAY AFTERNOON FOR
ADDITIONAL RAIN WEDNESDAY NIGHT AND THURSDAY. THE SNOW LEVELS WILL BE
SLOW TO RISE AHEAD OF THE FRONT AND EXPECT A QUICK BURST OF SNOW FOR
THE CASCADE PASSES AS THE MOISTURE FIRST REACHES THE CASCADES
WEDNESDAY NIGHT. THE SNOW LEVELS SHOULD RISE ABOVE 6000 FEET EARLY
THURSDAY MORNING...WITH A POSSIBLE DELAY FOR THE WASHINGTON CASCADES.

THIS SYSTEM IS VERY MOIST AS SATELLITE DERIVED PRECIPITABLE WATERS
NEAR THE ORIGIN POINT ARE AROUND 2 INCHES...WHICH IS THE HIGHEST WE
HAVE SEEN FROM THE RECENT ATMOSPHERIC RIVER EVENTS. THE PRECIPITABLE
WATER WILL DECREASE AS THE FRONT NEARS THE COAST...BUT THERE IS GREAT
POTENTIAL FOR ANOTHER ROUND OF HEAVY RAIN. EXPECT 1 TO 3 INCHES OF
RAIN FOR THE COAST...COAST RANGE AND THE CASCADES WEDNESDAY EVENING
THROUGH THURSDAY EVENING...AND 0.75 TO 1.25 INCH FOR THE INTERIOR LOW
LANDS.

MODELS FORECAST THAT THE BAROCLINIC ZONE WILL MOVE RATHER QUICKLY
ACROSS THE AREA...WITH RAIN ENDING THURSDAY EVENING. THIS WILL HELP
LIMIT THE RAINFALL TOTALS AND FLOODING POTENTIAL. IT ALSO LOOKS LIKE
THE AREA OF HEAVIEST RAIN WILL BE ACROSS NW OREGON RATHER THAN SW
WASHINGTON. THE RIVERS TO THE SOUTH HAVE TAKEN LESS OF A BEATING THE
PAST WEEK THAN WASHINGTON...IN REGARDS TO RAIN TOTALS...AND THIS MAY
ALSO HELP REDUCE FLOODING CONCERNS. RAIN WILL DECREASE THURSDAY NIGHT
 WITH DRY WEATHER LIKELY FRIDAY.

.LONG TERM...NO CHANGES. PREVIOUS DISCUSSION FOLLOWS...THURSDAY NIGHT
THROUGH MONDAY...A SHORTWAVE MOVES QUICKLY ACROSS THE AREA FRIDAY
BRINGING ANOTHER CHANCE FOR RAIN...THOUGH LIKELY NOT VERY MUCH. SNOW
LEVELS WILL BE DOWN AROUND 4000 TO 6000 FT...SO THE PASSES MAY SEE
ANOTHER INCH OR TWO OF SNOW. BEYOND FRIDAY...THE GFS BUILDS HIGH
PRESSURE OVER THE AREA KEEPING US DRY THROUGH THE WEEKEND...WHILE THE
ECMWF IS A LITTLE SLOWER MOVING THE SHOWERS OUT OF OUR AREA AND KEEPS
A CHANCE OF RAIN THROUGH SATURDAY. BY SUNDAY AT THE LATEST...WE
SHOULD BE DRY WITH HIGH PRESSURE OVER THE AREA. TEMPERATURES WILL
COOL DOWN AS WELL ...ESPECIALLY BY MONDAY. BOTH THE ECMWF AND GFS
SUGGEST ANOTHER WEATHER SYSTEM BRINGING MORE RAIN EARLY NEXT
WEEK...BUT DETAILS ARE VERY UNCERTAIN AT THIS TIME. -MCCOY
&&

.AVIATION...WARM FRONT HAS PUSHED NORTH OF THE AREA AND STALLED IN
THE VCTY OF PUGET SOUND. CONDITIONS ARE GRADUALLY IMPROVING TODAY.
WILL STILL SEE POCKETS OF LOW END MVFR CIGS AND OCCASIONAL VSBYS
ACROSS THE NORTH AS WEAK IMPULSES MOVE EAST ALONG THE STALLED FRONT
AND DRAG OCCASIONAL SHOWERS OVERHEAD. THE FRONT WILL THEN RETURN
SOUTH AS A COLD FRONT. FROPA TIMING FOR THE 12Z PACKAGE IS A FEW
HOURS LATER WITH THE PRIMARY STEADY RAINS AND DETERIORATING
CONDITIONS APPEARING ACROSS THE NORTH NEAR 22Z AND CLOSER TO 02Z FOR
THE SOUTH. SHOULD SEE A RETURN TO LOW END MVFR CIGS AND POSSIBLE IFR
VSBYS/CIGS. CONDITIONS WILL IMPROVE ACROSS THE BOARD UNDER SHOWERS
APPROXIMATELY 3 TO 4 HOURS OF POOR FLYING CONDS.

KPDX AND APPROACHES...TERMINAL AREA MAY HAVE A HARD TIME BREAKING
OUT OF CIGS 015 TO 025 TODAY AS THE STALLED FRONTAL BOUNDARY REMAINS
JUST NORTH OF THE REGION. EXPECT THE FRONT WILL DRIFT SOUTH LATE
TODAY WITH AN OCCASIONAL IFR DROP IN VSBYS AS RAIN SHOWER INTENSITY
INCREASES. EXPECT TO SEE A MODESTLY RAPID IMPROVEMENT IN CIGS WITH
THE BACK EDGE OF THE FRONT FOLLOWED BY MINIMAL IMPACTS TO VISUAL
APPROACHES BY LATE EVENING.

&&

.MARINE...SOUTH TO SOUTHWESTERLY SMALL CRAFT GUSTS CONTINUE OVER
THE WATERS EARLY THIS MORNING. THESE WILL MAINTAIN FOR THE NEXT
SEVERAL HOURS. AVAILABLE OBSERVATIONS SUGGEST WIND GUSTS OVER THE
NORTHERN OUTER WATERS REMAIN A LITTLE SHORT OF GALE STRENGTH...BUT
WITH LATEST MODELS CONTINUING TO SUGGEST GALES WILL ARRIVE IN THE
NEXT FEW HOURS...WILL MAINTAIN CURRENT TIMING FOR THE GALE
WARNING. SEAS REMAIN IN THE 13 TO 16 FT RANGE THIS MORNING.

AS THE STRONG TRAILING COLD FRONT WILL MOVE THROUGH THE WATERS
TUE AND TUE EVENING...SOUTHERLY WINDS WILL PICK UP AGAIN AHEAD OF
THE FRONT...WITH GUSTS 35 TO 45 KT EXPECTED TO DEVELOP IN THE
MORNING FOR THE NORTHERN WATERS AND IN THE AFTERNOON AND EVENING
FURTHER SOUTH AS THE FRONT MOVES THROUGH THE WATERS FROM THE
NORTH. A GALE WARNING IS IN EFFECT FOR ALL OF THE WATERS DURING
THIS TIME. THERE WILL BE A SMALL WINDOW IN THE AFTERNOON AND
EARLY EVENING...BETWEEN ROUGHLY NOON AND 5 PM...FOR A FEW LOCAL
GUSTS TO 50 KT OVER THE NORTHERN WATERS.

SOUTHERLY WINDS WILL TURN SOUTHWESTERLY AGAIN LATE TUESDAY AND
THEN A RAPID SHIFT TO NORTHWESTERLY BEHIND THE FRONT TUESDAY
EVENING. ENHANCED WESTERLY SWELL ASSOCIATED WITH THIS SYSTEM
APPROACHING WILL BUILD IN DURING THE DAY TUE...WITH SEAS EXPECTED
TO REACH 20 TO 23 FT DURING THE AFTERNOON AND EVENING. HIGH SURF
CONDITIONS TO AFFECT TO THE SW WASHINGTON AND NW OREGON COAST.

ANOTHER FRONTAL SYSTEM IS EXPECTED FOR WED NIGHT INTO THURSDAY AND
LOOKS TO HAVE A SURFACE LOW HEADED STRAIGHT FOR NW OREGON...WHICH
WOULD BRING YET ANOTHER ROUND OF GUSTY WINDS TO THE
WATERS...PARTICULARLY OVER THE CENTRAL OREGON WATERS. MODELS THEN
AGREE ON HIGHER PRESSURE BUILDING OVER THE NE PAC FOR THE END OF
THE WEEK AND THE WEEKEND. CULLEN

&&

.PQR WATCHES/WARNINGS/ADVISORIES...
OR...HIGH WIND WARNING FROM 10 AM THIS MORNING TO 7 PM PST THIS
     EVENING FOR COAST RANGE OF NORTHWEST OREGON-NORTH OREGON
     COAST.

     HIGH SURF ADVISORY FROM NOON TODAY TO MIDNIGHT PST TONIGHT FOR
     NORTH OREGON COAST.

WA...HIGH WIND WARNING FROM 10 AM THIS MORNING TO 7 PM PST THIS
     EVENING FOR SOUTH WASHINGTON COAST-WILLAPA HILLS.

     HIGH SURF ADVISORY FROM NOON TODAY TO MIDNIGHT PST TONIGHT FOR
     SOUTH WASHINGTON COAST.

PZ...GALE WARNING UNTIL 9 PM PST THIS EVENING FOR WATERS FROM CAPE
     SHOALWATER WA TO CASCADE HEAD OR FROM 10 TO 60 NM.

     GALE WARNING FROM 11 AM THIS MORNING TO 9 PM PST THIS EVENING
     FOR COASTAL WATERS FROM CASCADE HEAD OR TO FLORENCE OR OUT 60
     NM.

     SMALL CRAFT ADVISORY FOR ROUGH COLUMBIA RIVER BAR UNTIL 4 AM PST
     WEDNESDAY.

     GALE WARNING FROM 7 AM THIS MORNING TO 9 PM PST THIS EVENING
     FOR COASTAL WATERS FROM CAPE SHOALWATER WA TO CASCADE HEAD OR
     OUT 10 NM.

&&

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.