High Wind in Oregon, December 12, 2015

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE PORTLAND OR
913 AM PST SAT DEC 12 2015

.SYNOPSIS...ANOTHER POTENT FRONTAL SYSTEM IS APPROACHING THE COAST
SAT MORNING...AND WILL SPREAD RAIN ACROSS THE REGION TODAY AS IT
MOVES INLAND...WITH HEAVY SNOW IN THE CASCADES. SNOW LEVELS MAY
BRIEFLY RISE ABOVE PASS LEVEL LATE TODAY...BUT THE SKI RESORT
ELEVATIONS SHOULD MOSTLY SEE SNOW. THIS SYSTEM WILL BRING A BRIEF
PERIOD OF STRONG WINDS TO THE COAST TODAY...WITH BREEZY CONDITIONS
INLAND THIS AFTERNOON. LOCALLY HEAVY RAINFALL WILL BE POSSIBLE YET
AGAIN...BUT THE HEAVIEST RAIN WILL LIKELY BE ACROSS SW OREGON THIS
TIME AROUND. COOL AND SHOWERY WEATHER WILL PERSIST INTO SUNDAY AND
MONDAY AS THE ASSOCIATED UPPER TROUGH MOVES ACROSS THE PAC NW...WITH
PERHAPS A THUNDERSTORM OR TWO DUE TO THE UNSTABLE AIR MASS. DRIER
WEATHER IS EXPECTED TUESDAY AND POSSIBLY WEDNESDAY AS A WEAK UPPER
RIDGE MOVES THROUGH...BUT ANOTHER ATMOSPHERIC RIVER TYPE SYSTEM MAY
BE ON TAP FOR THE SECOND HALF OF NEXT WEEK.

&&

.SHORT TERM...RAIN WAS SEEN ON RADAR SPREADING INLAND OVER WA AND OR
SAT MORNING AS A FRONT APPROACHED THE COAST. DEEP MOIST ISENTOPIC
LIFT WILL MOVE ACROSS THE REGION TODAY...SEEN FROM THE 300K
ISENTROPE IN THE MID LEVEL DOWN BELOW THE 290K ISENTROPE IN LOW
LEVELS. NORTHERN PERIPHERY OF A TROPICAL MOISTURE PLUME WILL ARRIVE
ON THE OREGON COAST TODAY...WHICH COUPLED WITH A STRONG ONSHORE LOW
LEVEL WIND FIELD WILL ENHANCE PRECIPITATION RATES THIS AFTERNOON AND
EVENING...WITH THE FOCUS OF HEAVIER RAINFALL ACROSS THE SOUTHERN
PART OF THE FORECAST AREA. FOCUS FOR HEAVY RAIN THEN SHIFTS S
TONIGHT AS A BAROCLINIC ZONE CONTINUES TO SAG S AND THE STRONGER LOW
LEVEL WINDS ALSO SHIFT S. SURFACE PRES GRADIENTS AROUND 12 MB DOWN
THE OREGON COAST TODAY SUGGEST SOME THREAT FOR HIGH WINDS ALONG THE
COAST...MAINLY FOR A SHORT PERIOD OF TIME THIS AFTERNOON AS THE WARM
FRONT/OCCLUDING FRONT MOVES INLAND. OVERALL WIND FIELD LOOKS RATHER
MARGINAL THOUGH...WITH MODEL BOUNDARY LAYER WINDS PEAKING AROUND 50
KT. WILL KEEP THE WARNING UP...BUT FOCUS MAIN WIND THREAT ON
HEADLANDS AND BEACHES. SNOW LEVELS BEGINNING THE DAY DOWN AROUND 3K
FT...WILL LIKELY COME UP SOME TODAY AS THE OCCLUDING FRONT MOVES
INLAND LATE IN THE DAY INTO THIS EVENING. LANE COUNTY CASCADES SEES
THE BIGGEST THREAT OF RISING SNOW LEVELS...BUT LATEST MODEL RUNS
SUGGEST SNBOW LEVELS TOPPPING OUT AROUND 5500 FT THIS EVENING AS THE
WARMER AIR MASS PUSHES INLAND WITH THE OCCLUDING FRONT...BUT IS ALSO
QUICKLY PUSHED S AS THE BAROCLINIC ZONE SINKS S. LOOKS LIKE HEAVIEST
SNOW POTENTIAL WILL BE ACROSS THE S PART OF THE CASCADES WHERE BOTH
OROGRAPHICS AND PRECPITABLE WATER CONTENT REMAIN MOST FAVORABLE
LONGEST.

REMAINDER OF PREVIOUS SHORT TERM DISCUSSION FOLLOWS...AS FOR HYDRO
CONCERNS...AS MENTIONED ABOVE IT APPEARS THE HEAVIEST QPF WILL BE
OVER SW OREGON THIS TIME AROUND. EXPECT A DECENT SHOT OF RAIN MIDDAY
TODAY...BUT THIS SHOULD TAPER OFF WITHIN A FEW HOURS AS THIS FRONT
IS RATHER FAST-MOVING UNTIL THE NEXT WAVE DEVELOPS AND STALLS THE
FRONT NEAR THE OR/CA BORDER. IF THE FRONT STALLS A LITTLE FURTHER
NORTH THAN PRESENTLY EXPECTED WE WILL NEED TO CLOSELY MONITOR OUR
SOUTHERN RIVERS FOR FLOODING AS MANY OF THEM ARE ALREADY NEAR
BANKFULL. OF PARTICULAR CONCERN IS THE LUCKIAMUTE AT SUVER. OTHER
SLOWER RESPONDING RIVERS SUCH AS THE TUALATIN AND PUDDING WILL
REMAIN ABOVE FLOOD STAGE FOR A WHILE AS WATER FROM THE PAST WEEK OF
HEAVY RAIN MOVES THROUGH THE SYSTEM. SIGNIFICANT RISES ARE EXPECTED
ON THE WILLAMETTE THE NEXT COUPLE OF DAYS...REACHING BANKFULL AT
SOME GAGES...BUT NO FLOODING IS EXPECTED ON THE WILLAMETTE.

COLDER AIR WILL PUSH IN QUICKLY WITH THE FRONT...AND 00Z/06Z NAM
SOUNDINGS SHOW A CLOSE CALL IN UNDERCUTTING LANE COUNTY WITH COLD AIR
WHILE PRECIPITATION IS STILL OCCURRING. TAKING THE 06Z NAM SOUNDINGS
AT FACE VALUE THERE COULD BE SOME MIXED RAIN/SNOW NEAR EUGENE SUNDAY
MORNING...BUT SUSPECT THIS IS A BIT OVERDONE. OTHERWISE OUR FORECAST
AREA WILL TRANSITION TO A COOL/SHOWERY REGIME FOR SUNDAY AND MONDAY.
A COUPLE THUNDERSTORMS ARE POSSIBLE AS THE COLD POOL ALOFT MOVES
ACROSS THE PAC NW...ESPECIALLY SUN AFTERNOON AS THE UPPER TROUGH AXIS
AND/OR SECONDARY UPPER LOW MOVE THROUGH. EITHER WAY...EXPECT NUMEROUS
SHOWERS WITH FAIRLY LOW SNOW LEVELS... AROUND 2000 FEET. WITH
FREEZING LEVELS SO LOW THERE COULD EASILY BE HAIL IN HEAVIER SHOWERS
SUN/MON.  WEAGLE

.LONG TERM...MONDAY NIGHT THROUGH FRIDAY...A RELATIVE LULL IN THE
ACTIVE PATTERN CONTINUES TO BE FORECAST BY MOST MODELS MON NIGHT AND
TUE AS OUR COLD UPPER TROUGH MIGRATES INTO THE GREAT BASIN AND UPPER
LEVEL RIDGING MOVES IN. ANY LINGERING SHOWERS MON NIGHT SHOULD TAPER
OFF QUICKLY AND/OR BE LIMITED TO THE HIGHER TERRAIN. THE COOL AIR
MASS LEFT BEHIND BY THE UPPER TROUGH MAY BE IMPORTANT FOR THE NEXT
WELL-ORGANIZED SYSTEM FORECAST BY MOST MODELS TO ARRIVE WED NIGHT OR
THU. IF COOL HIGH PRESSURE CAN GET ESTABLISHED EAST OF THE
CASCADES...THERE MAY BE SOME WINTRY PRECIP ISSUES IN THE COLUMBIA
GORGE AND HOOD RIVER VALLEY AS ANY APPROACHING SYSTEM WOULD LIKELY
PULL IN EASTERLY FLOW AHEAD OF IT.

WILL ALSO NEED TO MONITOR THE LONGER TERM IMPACTS OF THE VERY LARGE
LOW PRESSURE SYSTEM DEVELOPING UPSTREAM IN THE WEST PACIFIC AND
MOVING TOWARD THE ALEUTIANS AND BERING SEA. THIS WILL LIKELY LEAD TO
AN AMPLIFIED PATTERN OF SOME SORT FOR THE WESTERN HEMISPHERE...WHICH
COULD LEAD TO RIDGING OFFSHORE AND A MORE SIGNIFICANT DRYING TREND BY
NEXT WEEKEND. THAT SAID...THE 00Z SUITE OF GUIDANCE DOES NOT OFFER
MUCH SUPPORT FOR A MAJOR DRYING TREND...IN FACT MODELS GENERALLY
FOLLOW THE WED NIGHT/THU SYSTEM WITH ANOTHER STRONG SYSTEM FRIDAY.
KEPT POPS GENERALLY NEAR OR ABOVE CLIMO IN THE EXTENDED ASIDE FROM
THE RELATIVELY DRY PERIOD TUE/EARLY WED.  WEAGLE

&&

.AVIATION...A WARM FRONT WILL SPREAD STEADY RAIN INTO THE REGION
THIS MORNING AND RESULT IN MOST AREAS LOWERING SOLIDLY INTO MVFR
CONDITIONS BETWEEN 18Z SATURDAY AND 03Z SUNDAY. COASTAL LOCATIONS
AND KHIO WILL LIKELY SEE PERIODS OF IFR CONDITIONS DURING THIS
TIME AS WELL...WHILE OTHER TAF SITES WILL LIKELY ONLY SEE A BRIEF
PERIOD OF IFR CONDITIONS AROUND 21Z SATURDAY TO 00Z SUNDAY. AN
UNSTABLE POST FRONTAL ATMOSPHERE SHOULD RESULT IN MOST LOCATIONS
TURNING GENERALLY VFR...EXCEPT ACROSS THE SOUTH WHERE STEADIER RAIN
WILL LIKELY LINGER WELL INTO TONIGHT...AND MAY PRODUCE AN EXTENDED
PERIOD OF IFR CONDITIONS AT KONP AND KEUG.

KPDX AND APPROACHES...A WARM FRONT WILL BRING STEADIER RAIN AND
AND RESULT IN CONDITIONS LOWERING FROM VFR TO MAINLY MVFR FOR AN
EXTENDED PERIOD BETWEEN 18Z SATURDAY AND 03Z SUNDAY. THERE MAY BE
BRIEF PERIOD OF IFR CONDITIONS AROUND 21Z SATURDAY TO 00Z SUNDAY.
OTHERWISE...CONDITIONS SHOULD IMPROVE TO MAINLY VFR CONDITIONS
WITH PERHAPS AN OCCASIONAL MVFR CONDITION AFTER 06Z SUNDAY.
/NEUMAN

&&

.MARINE...GALE FORCE WINDS ARE ALREADY BEGINNING TO SPREAD INTO
THE WATERS AS A COLD FRONT APPROACHES THE REGION. EXPECT SOLID
GALE FORCE WIND GUSTS OF 35 TO 45 KT THROUGH APPROXIMATELY MID
AFTERNOON. A COASTAL JET WILL LIKELY ENHANCE WIND SPEEDS WITHIN 20
NM OF THE COAST AND MAY PRODUCE A BRIEF BURST OF 50 KT WIND GUSTS
IN THIS REGION AROUND NOON. THIS SHOULD ALLOW SEAS TO RISE FROM THE
MID TEENS INTO THE UPPER TEENS BY LATE THIS AFTERNOON...AND PERHAPS
ABOVE 20 FT FOR A BRIEF PERIOD. WINDS SHOULD RELAX CONSIDERABLY
BEHIND THE COLD FRONT...BUT WILL THEN LIKELY PICK BACK UP ACROSS THE
NORTHERN WATERS AND REMAIN GUSTY...NEAR 30 TO 35 KT OVERNIGHT. A
WESTERLY SWELL SHOULD THEN PUSH SEAS INTO 18 TO 22 FT
RANGE...HIGHEST OVER THE NORTHERN WATERS LATE TONIGHT.

GUSTY NORTHWEST WINDS WILL LIKELY SPREAD ACROSS MOST OF THE
WATERS SUNDAY AND PRODUCE AN EXTENDED PERIOD OF WIND GUSTS OF 30
TO 35 KT. WILL EXAMINE THIS FURTHER AND DECIDE WHETHER OR NOT TO
EXTEND THE CURRENT GALE WARNING INTO SUNDAY/SUNDAY NIGHT OR
WHETHER A SMALL CRAFT ADVISORY WILL BE MORE APPROPRIATE.

HIGH PRESSURE IS THEN EXPECTED TO BUILD OVER THE NORTHEAST PACIFIC
EARLY NEXT WEEK. THIS SHOULD PRODUCE CONSIDERABLY LESS WIND AND MAY
EVEN ALLOW SEAS TO DROP 10 FT BY TUESDAY. MODELS SUGGEST A
DEVELOPING SURFACE LOW PRESSURE IN SOME SHAPE OR FORM MAY BRING MORE
ACTIVE WEATHER TO THE REGION TOWARDS THE MIDDLE OF NEXT WEEK.

A COASTAL FLOOD ADVISORY FOR TIDAL OVERFLOW REMAINS IN EFFECT FOR
THE SATURDAY AFTERNOON HIGH TIDE AS MINOR OVERFLOW FLOODING NEAR
THE SURF ZONE AND BAYS AND ESTUARIES WILL AGAIN BE PROBABLE.
IMPACTS MAY BE SIMILAR TO FRIDAY FOR THE S WA AND N OR COAST...BUT
PERHAPS ANY FLOODING LOOKS TO BE LESS ALONG THE CENTRAL OREGON
COAST. TIDES DO NOT CHANGE MUCH FOR SUNDAY SO WE WILL LIKELY ISSUE
ANOTHER ADVISORY FOR THE SUNDAY HIGH TIDE AS WELL. /NEUMAN

&&

.PQR WATCHES/WARNINGS/ADVISORIES...
OR...HIGH WIND WARNING UNTIL 5 PM PST THIS AFTERNOON FOR CENTRAL
     OREGON COAST-NORTH OREGON COAST.

     COASTAL FLOOD ADVISORY UNTIL 3 PM PST THIS AFTERNOON FOR CENTRAL
     OREGON COAST-NORTH OREGON COAST.

     WINTER STORM WARNING UNTIL 10 AM PST SUNDAY FOR CASCADES IN LANE
     COUNTY-NORTHERN OREGON CASCADES.

WA...HIGH WIND WARNING UNTIL 5 PM PST THIS AFTERNOON FOR SOUTH
     WASHINGTON COAST.

     COASTAL FLOOD ADVISORY UNTIL 3 PM PST THIS AFTERNOON FOR SOUTH
     WASHINGTON COAST.

     WINTER STORM WARNING UNTIL 10 AM PST SUNDAY FOR SOUTH WASHINGTON
     CASCADES.

PZ...GALE WARNING UNTIL 10 PM PST THIS EVENING FOR COASTAL WATERS FROM
     CAPE SHOALWATER WA TO FLORENCE OR OUT 60 NM.

     SMALL CRAFT ADVISORY FOR ROUGH COLUMBIA RIVER BAR UNTIL 10 PM PST
     THIS EVENING.

&&

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.