High Wind in Washington, December 22 to 23, 2015

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE PORTLAND OR
250 PM PST TUE DEC 22 2015

.SYNOPSIS...RAIN WILL INCREASE THIS AFTERNOON AND TONIGHT AS ANOTHER
FRONTAL SYSTEM MOVES INTO THE PACIFIC NORTHWEST FROM THE NORTHWEST.
SNOW LEVELS WILL REMAIN WELL BELOW THE CASCADE PASSES...WITH
SIGNIFICANT SNOWFALL IN THE CASCADES...FOOTHILLS...AND COASTAL
MOUNTAINS FROM PERSISTENT WEST TO NORTHWEST ONSHORE OROGRAPHIC FLOW.
A LOW ANCHORED ALONG THE B.C. COAST WILL DIRECT ANOTHER FRONT INTO
THE AREA WEDNESDAY FOR MORE VALLEY RAIN AND MOUNTAIN AND FOOTHILL AND
COAST RANGE SNOW. A COLDER UPPER TROUGH WILL DIG SOUTH ALONG THE
COAST ON CHRISTMAS EVE DAY FOR MORE SHOWERS SPREADING ONSHORE. THE
ONSHORE FLOW WILL FINALLY WEAKEN CHRISTMAS DAY WITH DECREASING
SHOWERS. THE NEXT FRONT IS EXPECTED LATE IN THE WEEKEND OR EARLY NEXT
WEEK.
&&

.SHORT TERM...TONIGHT THROUGH CHRISTMAS DAY...OVERRUNNING
PRECIPITATION WAS SPREADING INTO SOUTHWEST WASHINGTON AND NORTHWEST
OREGON WITH AN INCOMING WARM FRONT THIS AFTERNOON AND EVENING. THIS
FRONT WILL MOVE THROUGH TONIGHT WITH VALLEY RAIN AND SNOW IN THE
CASCADES...FOOTHILLS...AND COASTAL MOUNTAINS AS SNOW LEVELS LOWER TO
2000 TO 2500 FEET. THE ANCHORING SURFACE LOW ALONG THE B.C. COAST
WILL DIRECT ANOTHER FRONT INTO THE AREA ON WEDNESDAY FOR MORE VALLEY
RAIN AND CASCADE...FOOTHILL...AND COASTAL MOUNTAIN SNOW. BOTH OF
THESE SYSTEMS HAVE A LOT OF ONSHORE WEST TO NORTHWEST LOW LEVEL
OROGRAPHIC FLOW WITH THEM...WHICH IS GREAT FOR PILING UP SNOW IN THE
MOUNTAINS...AND WHICH HAS NOT HAPPENED MUCH IN THE LAST FEW YEARS.

THE PARENT COOL UPPER TROUGH BEGINS TO DIG SOUTH ALONG THE COAST
WEDNESDAY NIGHT INTO THURSDAY. ONSHORE FLOW STARTS TO WEAKEN LATER
THURSDAY. STILL SHOULD SEE SOME SNOW ACCUMULATIONS IN THE CASCADES
AND FOOTHILLS AND COASTAL MOUNTAINS WEDNESDAY NIGHT AND THURSDAY...
THOUGH THEY START TO LESSEN LATER THURSDAY. AN UPPER RIDGE STARTS TO
BUILD IN CHRISTMAS DAY WITH JUST A FEW REMAINING RAIN AND SNOW
SHOWERS AS DECREASING CLOUDS WILL LEAD TO COOLER TEMPERATURES AND
LOWER SNOW LEVELS.

THE CURRENT WINTER STORM WARNINGS LOOK GOOD FOR A LONG DURATION SNOW
EVENT FOR THE TERRAIN ABOVE THE VALLEYS...DESPITE THE FACT ANY 12
HOUR PERIOD MIGHT NOT REACH CRITERIA. HAVE ISSUED A SNOW ADVISORY FOR
THE UPPER HOOD RIVER VALLEY FOR THE NEXT 24 HOURS AS SNOW LEVELS LOOK
TO HOVER BETWEEN 1000 AND 2000 FEET AND THEY WILL GET SOME
ACCUMULATING SNOW AT TIMES. OTHER THAN A BRIEF TIME THIS EVENING WITH
LIGHT POSSIBLY WEAK EAST WINDS THIS EVENING...WINDS STAY MOSTLY
WESTERLY THROUGH THE GORGE SO THINK THE GORGE WILL HAVE TROUBLE
GETTING MUCH ACCUMULATION NEAR THE RIVER EXCEPT FOR A BRIEF TIME
TONIGHT.

THE OTHER ISSUE WILL BE WEST TO NORTHWEST WINDS ALONG THE COAST
TONIGHT INTO THURSDAY. THERE IS QUITE A FETCH OF WIND PUSHING ONTO
THE COAST...AND MAY SEE SOME GUSTS 30 TO 40 OR EVEN 45 MPH ON
OCCASION ALONG THE COAST AND IN THE MOUNTAINS THROUGH WEDNESDAY INTO
WEDNESDAY NIGHT. TOLLESON

.LONG TERM...NO CHANGES. PREVIOUS DISCUSSION FOLLOWS...FRIDAY NIGHT
THROUGH TUESDAY...AN UPPER RIDGE BUILDING IN FRIDAY NIGHT AND
CONTINUING SATURDAY WILL RESULT IN CLEARING SKIES...COLDER NIGHTTIME
TEMPS...AND AREAS OF VALLEY NIGHT AND MORNING VALLEY FOG. MODEL
TIMING VARIES SOME...BUT THE NEXT FRONT LOOKS TO MOVE IN SUNDAY AND
SUNDAY NIGHT WITH SNOW LEVELS RISING A BIT...BUT STILL SNOW IN THE
CASCADES. THIS WILL BE FOLLOWED BY DECREASING SHOWERS FOR THE EARLY
PART OF NEXT WEEK. TOLLESON
&&

.AVIATION...A WEAK WARM FRONT MOVING ONSHORE THIS AFTERNOON WILL
BRING A PERIOD OF LIGHT RAIN AND MVFR/HIGH IFR CONDITIONS THROUGH
AROUND 03Z THIS EVENING. THE COASTAL TAF SITES WILL ALSO SEE WESTERLY
WINDS  EXPECT CONDITIONS TO IMPROVE BEHIND THE FRONTAL PASSAGE AFTER
03Z AND REMAIN PREDOMINANTLY VFR IN A SHOWERY ONSHORE FLOW PATTERN
TONIGHT THROUGH WED MORNING. EXPECT RAIN COVERAGE TO INCREASE AGAIN
WED AFTERNOON...WITH CONDITIONS LIKELY BECOMING PREDOMINANTLY MVFR.

KPDX AND APPROACHES...EXPECT LIGHT RAIN AND MAINLY MVFR
CONDITIONS...WITH POTENTIAL FOR HIGH END IFR...THROUGH 03Z THIS
EVENING AS A WARM FRONT MOVES ONSHORE. CONDITIONS SHOULD IMPROVE TO
MAINLY VFR LATER THIS EVENING BEHIND THE WARM FRONT...AND REMAIN
MOSTLY VFR THROUGH WED MORNING IN SHOWERY ONSHORE FLOW. CONDITIONS
LIKELY TO DETERIORATE AGAIN WED AFTERNOON. PYLE
&&

.MARINE...WINDS TO SWITCH FROM S-SW TO W-NW AND INCREASE
SIGNIFICANTLY LATER THIS AFTERNOON AND THIS EVENING AS AN OCCLUDING
WARM FRONT PUSHES ONTO THE COAST. A GALE WARNING IS NOW IN
EFFECT...AND EXPECT WINDS OF 30 TO 35 KT WITH GUSTS 40 TO 45 KT. THE
FCST MODELS HAVE BEEN INDICATING THE POTENTIAL FOR A FEW LOW END
STORM FORCE GUSTS RIGHT BEHIND THE FRONT DURING THE LATE AFTERNOON OR
EARLY EVENING...BUT SO FAR HAVE NOT SEEN ANY INDICATION THAT THE
WINDS ARE QUITE THIS STRONG. THE PERIOD OF HIGHEST WINDS WILL BE
THROUGH THE EVENING HOURS...WITH WINDS SUBSIDING JUST A BIT
OVERNIGHT. THE WINDS ARE EXPECTED TO INCREASE AGAIN WED MID-MORNING
AND AFTERNOON AS A SURFACE LOW DROPS SOUTH TOWARD THE REGION ALONG
THE B.C. COAST. WILL KEEP A GALE WARNING ALL THE WAY THROUGH WED
EVENING...ALTHOUGH WINDS MAY DROP JUST A BIT BELOW WARNING CRITERIA
LATE TONIGHT INTO EARLY WED.

AFTER A LULL IN THE WINDS LATE WED INTO THU...YET ANOTHER LOW
DROPPING SOUTH DURING THE DAY THU MAY BRING AN ADDITIONAL UPTICK IN
WINDS...BUT CURRENT MODELS MOSTLY KEEP SPEEDS BELOW GALE CRITERIA.
THEN EXPECT A PERIOD OF MORE BENIGN CONDITIONS AS HIGH PRES MOVES IN
FOR FRI AND EARLY SAT.

A LONG WIND FETCH OVER THE NE PAC IS PRODUCING A SIGNIFICANT NW SWELL
TRAIN THAT WILL BUILD INTO THE WATERS STARTING TONIGHT...WITH SEAS
CONTINUING TO INCREASE THROUGH THE DAY WED. EXPECT SEAS TO BUILD
ABOVE 20 FT BY LATE THIS EVENING...THEN PEAK AROUND 25 TO 28 FT WED
AFTERNOON AND EVENING. HIGH SURF CONDITIONS WILL DEVELOP... AND A
HIGH SURF ADVISORY WAS ISSUED FOR THIS EVENING THROUGH DAYBREAK
WEDNESDAY. GIVEN THAT TIDES ARE RUNNING HIGH...COASTAL FLOODING
ISSUES APPEAR LIKELY WITH THE HIGH TIDE AROUND MIDDAY WEDNESDAY. HAVE
ISSUED A COASTAL FLOOD WARNING DURING THIS TIME. WHEN THE HIGH TIDE
SUBSIDES WEDNESDAY AFTERNOON...SEAS MAY STILL BE HIGH ENOUGH THAT A
HIGH SURF WARNING OR ADVISORY MAY BE NECESSARY FOR ANOTHER 12-18
HOURS. SEAS SHOULD SLOWLY SUBSIDE STARTING THU AND CONTINUE TO DROP
THROUGH FRI AND INTO THE WEEKEND. CURRENT GUIDANCE DROPS SEAS BELOW
20 FT BY THU MORNING AND INTO THE LOW TEENS BY LATE FRI. PYLE
&&

.PQR WATCHES/WARNINGS/ADVISORIES...
OR...WINTER WEATHER ADVISORY FROM 6 PM THIS EVENING TO 5 PM PST
     WEDNESDAY FOR UPPER HOOD RIVER VALLEY.

     WINTER STORM WARNING FROM 6 PM THIS EVENING TO 4 AM PST
     THURSDAY FOR CASCADE FOOTHILLS IN LANE COUNTY-CASCADES IN LANE
     COUNTY-CENTRAL COAST RANGE OF WESTERN OREGON-COAST RANGE OF
     NORTHWEST OREGON-NORTHERN OREGON CASCADE FOOTHILLS-NORTHERN
     OREGON CASCADES.

     COASTAL FLOOD WARNING FROM 8 AM TO 4 PM PST WEDNESDAY FOR
     CENTRAL OREGON COAST-NORTH OREGON COAST.

     HIGH SURF ADVISORY FROM 6 PM THIS EVENING TO 8 AM PST WEDNESDAY
     FOR CENTRAL OREGON COAST-NORTH OREGON COAST.

WA...WINTER STORM WARNING FROM 6 PM THIS EVENING TO 4 AM PST
     THURSDAY FOR SOUTH WASHINGTON CASCADE FOOTHILLS-SOUTH
     WASHINGTON CASCADES-WILLAPA HILLS.

     COASTAL FLOOD WARNING FROM 8 AM TO 4 PM PST WEDNESDAY FOR SOUTH
     WASHINGTON COAST.

     HIGH SURF ADVISORY FROM 6 PM THIS EVENING TO 8 AM PST WEDNESDAY
     FOR SOUTH WASHINGTON COAST.

PZ...GALE WARNING UNTIL 8 PM PST WEDNESDAY FOR COASTAL WATERS FROM
     CAPE SHOALWATER WA TO FLORENCE OR OUT 60 NM.

     SMALL CRAFT ADVISORY FOR ROUGH COLUMBIA RIVER BAR UNTIL 8 PM
     PST WEDNESDAY.

&&

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.