[ W WA | SW WA and W OR | SE WA and NE OR | NE WA and N ID ]

Western Washington


632 
FXUS66 KSEW 191726
AFDSEW

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SEATTLE WA
930 AM PST FRI DEC 19 2014

.SYNOPSIS...AN UPPER LEVEL TROUGH WILL BRING SCATTERED SHOWERS 
TODAY. A PAIR OF STRONG WARM FRONTS WILL BRING RAIN AND WIND 
TO WESTERN WASHINGTON TONIGHT THROUGH THIS WEEKEND. AN UPPER LEVEL 
RIDGE WILL MOVE BRIEFLY OVER THE REGION MONDAY FOR DRIER WEATHER. 
ADDITIONAL FRONTAL SYSTEMS WILL REACH THE REGION NEXT WEEK. 

&&

.SHORT TERM...AN UPPER LEVEL TROUGH IS PASSING THROUGH WESTERN WA 
THIS MORNING FOR SCATTERED SHOWERS ACROSS THE AREA. THERE WERE A FEW 
LIGHTNING STRIKES OVER THE COASTAL WATERS BUT THESE CELLS SHOULD 
DRIFT N/NE INTO B.C. THE TROUGH AXIS WILL EXIT THIS AFTERNOON WITH 
SHOWERS TAPERING OFF. EXPECT HIGHS IN THE LOWER 50S TODAY. 

ANOTHER ROUND OF WEST AND BLUSTERY WEATHER IS ANTICIPATED LATE 
TONIGHT THROUGH SATURDAY AS OUR NEXT SYSTEM ARRIVES. THIS SYSTEM MAY 
BRING HIGH WIND TO THE COAST AND NORTH INTERIOR AS THE OCCLUDED 
FRONT MOVES INLAND SATURDAY MORNING. A HIGH WIND WATCH IS IN EFFECT 
FOR THESE ZONES. A PLUME OF MOISTURE IS BEING TRANSPORTED EAST ALONG 
A STRONG 175 KT JET AIMED AT WASHINGTON...WHICH WILL LIKELY RESULT 
IN HEAVY PRECIP ALONG THE COAST AND IN THE MOUNTAINS. INITIALLY SNOW 
LEVELS WILL START AROUND 3000-4000 FT SATURDAY MORNING BUT WILL RISE 
TO 5000-7000 FT SATURDAY AFTERNOON AS WARMER AIR MOVES IN FROM 
ANOTHER WARM FRONT. PARADISE AND MT BAKER COULD SEE BRIEF HEAVY SNOW 
BEFORE CHANGING OVER TO RAIN AND MAY NEED A WINTER WEATHER ADVISORY 
TO COVER THIS PERIOD. THE SNOW LEVELS WILL REMAIN HIGH SAT NIGHT 
THROUGH SUN WITH MAINLY RAIN IN THE MOUNTAINS. THIS MAY RESULT IN 
RIVER FLOODING AND A HYDROLOGIC OUTLOOK HAS BEEN ISSUED. AN UPPER 
LEVEL RIDGE WILL BUILD OVER THE AREA SUN NIGHT WHICH SHOULD BRING AN 
END TO THE STEADY/HEAVY PRECIP IN THE MOUNTAINS. 33

.LONG TERM...PREVIOUS DISCUSSION...BOTH THE GFS AND ECMWF HAVE A 
MODERATE AMPLITUDE UPPER LEVEL RIDGE FORMING OFFSHORE MONDAY MORNING 
THEN SHIFTING E OVER W WA MONDAY AFTERNOON. BOTH MODELS ALSO SHOW A 
SURFACE RIDGE MOVING OVER W WA ON MONDAY...ALTHOUGH THE GFS IS 
STRONGER THAN THE ECMWF. THIS WILL END THE WEEKENDS WET WINDY 
PERIOD. ANOTHER WEAKER WARM SYSTEM MOVES OVER THE TOP OF THE RIDGE 
MONDAY NIGHT AND TUESDAY...BRINGING A QUICK END TO MONDAYS BRIEF DRY 
PERIOD. THE GFS AND ECMWF SEEM TO BE IN FAIR AGREEMENT WITH THE 
LARGER PATTERN PAST MID NEXT WEEK...BUT WITH THE MODELS CONTINUING 
TO EVOLVE FROM RUN-TO-RUN...CONFIDENCE REMAINS LOW. BOTTOM LINE IS 
THAT ACTIVE WEATHER WILL PROBABLY BE CONTINUING. KAM 

&&

.HYDROLOGY...HEAVY RAIN COULD CAUSE FLOODING BY LATE THIS WEEKEND. A 
PAIR OF STRONG WARM FRONTS WILL BRING HEAVY RAIN AT TIMES TO THE 
COAST AND OLYMPICS ON SATURDAY. HEAVY RAIN WILL SPREAD INTO THE 
CASCADES SATURDAY AFTERNOON BUT MAY NOT BE AS HEAVY AS INITIALLY 
EXPECTED.

MODELS CURRENTLY TAPER RAIN OVER THE OLYMPICS SATURDAY NIGHT AND 
SUNDAY...BUT THE STRONGER W FLOW ALOFT SATURDAY NIGHT WILL BRING 
HEAVY RAIN TO THE CASCADES...ESPECIALLY OVER THE CASCADES FROM ABOUT 
KING COUNTY SOUTH. THE CURRENT RAINFALL FORECAST IN THE 36 HOUR 
PERIOD FROM 12Z SATURDAY THROUGH 00Z MONDAY HAS 3-5 INCHES OVER THE 
OLYMPICS AND ROUGHLY 3 TO 5 INCHES OVER THE CENTRAL CASCADES WITH 
ABOUT 7 INCH BULLSEYE OVER MT RAINIER. THIS IS LESS THAN THE 
PREVIOUS FORECAST. THE SNOW LEVEL WILL RISE TO 5000 TO 7000 FEET BY 
LATE SATURDAY AFTERNOON AND NIGHT...THEN LOWER BACK TO AROUND 5000 
FEET ON SUNDAY. 

THESE RAINFALL AMOUNTS MAY BE ENOUGH TO CAUSE FLOODING. AT THIS TIME 
THE RIVERS MOST LIKELY TO FLOOD ARE THE ONES FLOWING OFF THE 
CASCADES OF KING...PIERCE...AND LEWIS COUNTIES...AS WELL AS THE 
UNUSUALLY FLOOD-PRONE SKOKOMISH RIVER IN MASON COUNTY. ANY FLOODING 
WOULD LIKELY BEGIN AS EARLY AS SATURDAY NIGHT ON THE SKOKOMISH 
RIVER. THE CASCADE RIVERS COULD FLOOD SUNDAY WITH CRESTS SUNDAY 
NIGHT OR MONDAY. 

&&

.AVIATION...A FRONT MOVED INTO THE CASCADES EARLY THIS MORNING. 
SCATTERED SHOWERS REMAIN OVER WESTERN WASHINGTON. A STRONGER FRONTAL 
SYSTEM WILL REACH THE AREA LATER TONIGHT AND SATURDAY WITH WESTERLY 
FLOW ALOFT. THE AIR MASS WILL REMAIN MOIST BUT THERE MAY BE SOME SUN 
BREAKS TODAY. INCREASING MOISTURE AGAIN TONIGHT AND SATURDAY WITH 
STRONG WESTERLY FLOW ALOFT. AT THE SURFACE STRONG SOUTHEAST WINDS 
WILL DEVELOP TONIGHT. THE FLOW WILL TURN ONSHORE SATURDAY NIGHT.

CEILINGS ARE GENERALLY VFR WITH SOME HIGH END MVFR. SHOWERS AND SUN 
BREAKS WILL DEVELOP TODAY WITH VFR CEILINGS EXCEPT MVFR IN SHOWERS. 
CLOUDS WILL THICKEN AND LOWER TONIGHT WITH SATURDAY BEING MOSTLY 
MVFR WITH RAIN. 

KSEA...DISCUSSION ABOVE APPLIES. WIND TODAY WILL BE SOUTHERLY 8-12 
KT BECOMING SOUTHEAST TONIGHT AND INCREASING SATURDAY. CHB

&&

.MARINE...SMALL CRAFT ADVISORY WINDS ARE LIKELY OVER MOST WATERS 
TODAY IN THE WAKE OF A FRONT THAT PASSED LAST NIGHT. A STRONGER 
SYSTEM WILL APPROACH TONIGHT WITH GALES LIKELY OVER MOST WATERS. 
BOTH THE ADVISORIES AND WARNINGS ARE ALREADY UP FOR THESE WINDS. 
AFTER A BRIEF LULL IN WINDS SATURDAY AFTERNOON...MODELS SHOW A 
PERIOD OF STRONG ONSHORE FLOW SATURDAY NIGHT THAT WILL ALSO HAVE 
GALE SOUTHWEST WINDS OVER MOST WATERS.

A WEAKER SYSTEM ARRIVES MONDAY NIGHT OR TUESDAY.

SWELL ON THE COAST WILL REACH 20 FEET OR SO TONIGHT AND SATURDAY. 
COUPLED WITH HIGH TIDES AROUND NOON SATURDAY THERE COULD BE SOME 
MINOR TIDAL OVERFLOW AT SPOTS. SO FAR BUOY 5...ABOUT 300 MILES OFF 
THE COAST...SHOWS ONLY 20 FOOT SWELLS. THESE WILL DECAY A BIT BEFORE 
ARRIVING AT THE COAST. WILL DECIDE WHAT TO DO WITH THE COASTAL FLOOD 
WATCH THIS AFTERNOON. CHB

&&

.SEW WATCHES/WARNINGS/ADVISORIES...

WA...WINTER WEATHER ADVISORY THROUGH 6 AM FOR THE OLYMPICS AND       
     CASCADES.
     HIGH WIND WATCH FOR THE COAST AND NORTH INTERIOR LATE TONIGHT
      THROUGH SATURDAY EVENING.
     HIGH SURF ADVISORY FOR THE NORTH AND CENTRAL COAST FROM LATE
      THIS MORNING THROUGH EARLY SATURDAY MORNING.
     COASTAL FLOOD WATCH FOR THE NORTH AND CENTRAL COAST FROM
      SATURDAY MORNING THROUGH SATURDAY AFTERNOON.

PZ...SMALL CRAFT ADVISORY ALL WATERS EXCEPT PUGET SOUND AND
      THE CENTRAL STRAIT OF JUAN DE FUCA THROUGH THIS EVENING.
     GALE WARNING ALL WATERS EXCEPT THE CENTRAL STRAIT AND PUGET
      SOUND LATER TONIGHT THROUGH SAT.
     SMALL CRAFT ADVISORY GRAYS HARBOR BAR.

&&

$$

YOU CAN SEE AN ILLUSTRATED VERSION OF THIS FORECAST DISCUSSION AT 
WWW.WEATHER.GOV/SEATTLE/GAFD/LATEST_WEBAFD.HTML



[ W WA | SW WA and W OR | SE WA and NE OR | NE WA and N ID ]

Southwestern Washington and Western Oregon


422 
FXUS66 KPQR 191225
AFDPQR

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE PORTLAND OR 
424 AM PST FRI DEC 19 2014

.SYNOPSIS...AN UPPER LEVEL TROUGH WILL MOVE ACROSS THE FORECAST AREA
TODAY...WHICH WILL LOWER SNOW LEVELS BELOW THE CASCADE PASSES. THERE
MAY BE ENOUGH INSTABILITY TODAY OVER THE COASTAL AREAS FOR A THREAT
OF THUNDERSTORMS. MILD AND VERY WET WEATHER IS EXPECTED THIS WEEKEND
WITH AN ATMOSPHERIC RIVER PATTERN RESULTING IN HEAVY RAIN ACROSS MUCH
OF THE REGION...ESPECIALLY MOUNTAINOUS TERRAIN. THE EXACT LOCATION OF
THE JET STREAM AND ASSOCIATED MOISTURE PLUME IS STILL IN
QUESTION...BUT THERE IS INCREASING CONFIDENCE THAT IT WILL TAKE AIM
AT SW WASHINGTON AND NW OREGON. THERE IS THE POTENTIAL FOR SOME
FLOODING LATE THIS WEEKEND INTO EARLY NEXT WEEK. LONGER RANGE MODEL
OUTPUT IS SUGGESTING A COLDER AIR MASS WILL SETTLE OVER THE PACIFIC
NORTHWEST LATE NEXT WEEK. 

&&

.SHORT TERM....TODAY THROUGH SUNDAY...NWS KRTX DUAL-POL DOPPLER RADAR
AS OF 10Z SHOWS THE BACK EDGE OF THE FRONT MOVING ACROSS THE
CASCADES. SIX-HOUR RAINFALL AMOUNTS THROUGH 10Z WERE NOT ALL THAT
IMPRESSIVE...GENERALLY A QUARTER TO TWO-THIRDS OF AN INCH IN MOST
AREAS. RADAR AND INFRA-RED SATELLITE IMAGERY SHOW SHOWERS WITHIN THE
POST-FRONTAL COLDER AIR MASS ALREADY MOVING ONSHORE AND INTO THE
OREGON COAST RANGE AND SW WA WILLAPA HILLS. LIGHTNING DETECTION JUST
BEFORE 10Z INDICATED A POSITIVE STRIKE ALONG THE CENTRAL WA COAST.
JUST BEFORE 11Z A COUPLE STRIKES WERE NOTED NEAR FLORENCE. 

THE MAIN WEATHER FEATURE TODAY WILL BE THE COLD UPPER TROUGH. LATEST
MODEL GUIDANCE SHOWS THE BULK OF THE TROUGH THROUGH THE AREA BY
MIDDAY. SNOW LEVELS DROP TO BELOW THE CASCADES PASSES TODAY...BUT THE
MAJORITY OF THE QPF HAS ALREADY OCCURRED. OROGRAPHIC ENHANCEMENT WILL
GIVE SOME SNOW TO THE CASCADES BUT UNDER ADVISORY CRITERIA. NAM MODEL
SOUNDING FOR KAST WOULD INDICATE THE BEST POTENTIAL FOR THUNDERSTORMS
TO BE THROUGH THE MORNING HOURS. NAM SOUNDING VALID 17Z TODAY SHOWS
AN LI OF 0 WITH A PRETTY HEFTY SWEAT INDEX OF 335...WELL ABOVE THE
GENERALIZED 250 SWEAT INDEX BENCHMARK USED FOR ELEVATED CONVECTIVE
CONFIDENCE. THE CONVECTIVE POTENTIAL THEN DIMINISHES IN THE AFTERNOON
AS THE AIR MASS ALOFT STARTS TO STABILIZE. 

THE BIGGER STORY CONTINUES TO BE THE ATMOSPHERIC RIVER EVENT OVER THE
WEEKEND. LATEST MODEL RUNS ARE GENERALLY CONSISTENT WITH THEIR
RESPECTIVE PAST RUNS WITH FAIRLY DECENT CONTINUITY AMONGST THE
INDIVIDUAL MODELS. THE MAIN FORECAST ISSUES WILL BE THE FOCUS OF THE
HEAVIEST PRECIP AND THE DURATION. GFS HAS BEEN PERSISTENT IN
DIRECTING THE BAROCLINIC BAND OVER EXTREME SW WA AND NRN OREGON. THE
NAM AND ECMWF ARE FAIRLY SIMILAR...BUT THE ECMWF SEEMS TO FOCUS THE
HEAVIEST QPF OVER THE CENTRAL PART OF THE FORECAST AREA 12Z SUN
THROUGH 00Z MON. THE 00Z WRF-GFS 48-HR QPF TOTALS VALID 12Z SAT
THROUGH 12Z MON SHOW AT LEAST 3-6 INCHES FOR THE OREGON CASCADES AND
2-4 INCHES FOR THE OREGON COAST RANGE. IT HAS LOWER AMOUNTS IN THE S
WA CASCADES AND WILLAPA HILLS. GFS AND NAM HAVE STRONG ISENTROPIC
LIFT ALONG THE 290K SURFACE STARTING 12Z SAT AND CONTINUING THROUGH
SUN. 850 MB WLY FLOW OF 40-50 KT INTO THE OREGON COAST RANGE AND
CASCADES SAT THROUGH SUN WILL RESULT IN A HIGHLY EFFECIENT OROGRAPHIC
RAINFALL COMPONENT. LOOKING AT THE ENSEMBLE SITUATIONAL AWARENESS
TABLE...SPECIFICALLY THE ENSEMBLE MODEL CLIMATE QPF (OR M CLIMATE
QPF)...IT INDICATES A 99TH PERCENTILE OR MAX QPF EVENT FOR A GOOD
PORTION OF THE OREGON CASCADES SAT AFTERNOON THROUGH SUN MORNING.
THIS MEANS THAT THE GEFS ENSEMBLE IS FORECASTING AN INORDINATE AMOUNT
OF PRECIP COMPARED TO THE 1985-2012 WINTER ENSEMBLE MODEL CLIMATE. 
WOULD NOT BE SURPRISED TO SEE 1.5 TO 2.0 INCHES PER SIX HOURS IN THE
CASCADES FOR A 12-18 PERIOD. FORTUNATELY...THERE IS NO LOW-ELEVATION
SNOW AND MINIMAL SNOW AT PASS LEVELS. HOWEVER...LATEST HYDRO GUIDANCE
SUGGESTS A FEW RIVERS WILL REACH FLOOD STAGE BY SUN OR MON. REFER TO
THE HYDROLOGY SECTION FOR MORE DETAILS.

DO NOT ANTICIPATE HIGH WIND HIGHLIGHTS FOR THE COASTAL AREAS BUT IT
WILL BE RATHER BLUSTERY. THE NAM INDICATES A KAST-KOTH GRADIENT OF
AROUND 10 MB BY LATE SAT AFTERNOON AND IN THE EVENING. THE BENCHMARK
GRADIENT IS AROUND 12 MB. EXPECT 45-55 MPH GUSTS ALONG THE BEACHES
AND HEADLANDS SAT THROUGH SAT NIGHT. 

IN ADDITION...THOSE PLANNING TO BE ALONG THE COAST AT AREA BEACHES
SHOULD CLOSELY MONITOR THE CONDITIONS THIS WEEKEND. RAPIDLY BUILDING
SEAS WILL BRING THE POTENTIAL FOR DANGEROUS HIGH SURF ALONG THE
BEACHES AS EARLY AS TODAY. LONG PERIOD SWELLS MAY REACH SHORE AND
SURPRISE INDIVIDUALS WHO ARE UNAWARE. ANYONE ON THE BEACHES SHOULD
EXERCISE EXTREME CAUTION AND AVOID THE SURF ZONE AS LARGE WAVES MAY
WASH OVER BEACHES AND JETTIES WITH LITTLE WARNING. SOME POTENTIAL FOR
MINOR TIDAL OVERFLOW IS POSSIBLE FOR SATURDAY AND SUNDAY...ESPECIALLY
AROUND HIGH TIDES. THIS THREAT COULD BE ENHANCED BY HIGH FLOWS ON
RIVERS IN RESPONSE TO THE RAINFALL THIS WEEKEND.  WEISHAAR 

&&

.LONG TERM...SUNDAY NIGHT THROUGH FRIDAY...MODELS AGREE THE WEEKEND
ATMOSPHERIC RIVER EVENT WILL WIND DOWN SUNDAY NIGHT INTO MONDAY.
UPPER RIDGING AMPLIFIES MON...BUT THIS WILL LIKELY BE A DIRTY RIDGE
AS THE GFS AND ECMWF HOLD ON TO SOME QPF...ESPECIALLY ACROSS THE NRN
HALF OF THE FORCAST AREA. HAVE ADJUSTED POPS TO REFLECT THIS
THINKING. A WEAK WARM FRONT MAY BRUSH THE NRN ZONES MON NIGHT AND TUE
FOR SOME ADDITIONAL PRECIP. THE GFS AND ECMWF THEN BRING A COLDER
UPPER LEVEL TROUGH ACROSS THE AREA WED. THE ECMWF DROPS 1000-500 MB
THICKNESS VALUES TO NEAR 530 DM 00Z THU WITH A DECENT AMOUNT OF QPF.
THUS...THE CASCADES AND SKI AREAS MAY FINALLY GET A DECENT SHOT OF
SNOW. COLDER NORTH FLOW WILL FOLLOW AND ALLOW TEMPERATURES TO COOL
WELL BELOW NORMAL AS CONDITIONS DRY OUT LATE WEEK. WEISHAAR

&&

.HYDROLOGY...SITUATION SETTING UP FOR A MEMORABLE HYDROLOGIC EVENT 
MAINLY FOR LATER THIS WEEKEND AND HEADING INTO NEXT WEEK. STRONG AND 
DEEP MOIST WESTERLY FLOW WILL BEGIN CROSSING THE PACNW COAST COME 
SATURDAY MORNING. A VERY LONG FETCH OF MOISTURE IS STRETCHING ACROSS 
THE PACIFIC WITH ORIGINS WEST TO THE SOUTH CHINA SEA. THIS MOIST AIR 
MASS WILL BE PUSHED EAST BY A 150 TO 170 KT JET AND WESTERLY 25 TO 
50 KT LOWER LEVEL WINDS. AS SUCH...THIS CONTINUES TO GIVE THE 
APPEARANCE OF A CLASSIC HIGH PRECIPITATION ATMOSPHERIC RIVER EVENT 
WHERE THE DEEP MOIST FLOW WILL SPEND A SIGNIFICANT AMOUNT OF TIME  
ON A NEARLY PERPENDICULAR COURSE AGAINST THE COAST RANGE WITH THE 
CASCADES TAKING A BIT HIGHER OF THE IMPACT. AS OF THE MORNING MODEL 
RUNS AND RECENT NWRFC UPDATES...IT APPEARS MULTIPLE COAST RANGE 
RIVERS HAVE A MODERATE POTENTIAL OF EXCEEDING FLOOD STAGE. 
ADDITIONALLY...THIS EVENT HAS SUFFICIENT DEPTH TO BRING SIGNIFICANT 
RAINS TO THE NORTH OREGON AND SOUTH WASHINGTON CASCADES WHERE RIVERS 
WILL ALSO SEE POTENTIAL FOR NOTABLE FLOODING. WILL CONTINUE THE 
HYDROLOGIC OUTLOOK (PDXESFPQR) PRODUCT HIGHLIGHTING CONCERNS. KEEP 
IN MIND THAT DETAILS WILL ALWAYS BE IN FLUX UNDER THESE SCENARIOS AS 
SUBTLE NORTH/SOUTH SHIFTS COLD MAKE DRAMATIC DIFFERENCES IN WHICH 
BASINS RECEIVE EXTENDED PERIODS OF MODERATE TO HEAVY RAIN. PLEASE 
CONTINUE TO FOLLOW THE LATEST FORECASTS AND IMPACTS AS CONDITIONS 
WARRANT. RIVER FORECASTS ARE AVAILABLE ON OUR WEB PAGE AT: 
HTTP://WATER.WEATHER.GOV/AHPS2/INDEX.PHP?WFO=PQR (ALL LOWER CASE)

/JBONK

&&
&&


.AVIATION...VFR CONDITIONS WILL PERSIST AT MOST TAF SITES
THROUGH THIS EVENING. HOWEVER...BRIEF PERIODS OF MVFR CIGS AND
VIS ARE POSSIBLE UNDER SHOWERY CONDITIONS. DUE TO AN UNSTABLE AIR
MASS OVER THE WATERS THERE REMAINS A CHANCE OF VCTS THROUGH AROUND
18Z TODAY FOR THE COASTAL TAF SITES. CONDITIONS WILL LIKELY BE A
MIX OF IFR TO VFR TONIGHT AND SAT AS A MUCH STRONGER FRONT PUSHES
ACROSS THE REGION. EXPECT THE FRONT TO APPROACH THE COAST AROUND
02Z...AND INLAND AFTER 05Z.

KPDX AND APPROACHES...VFR CONDITIONS TODAY AND TONIGHT.
HOWEVER...BRIEF PERIODS OF MVFR CIGS ARE POSSIBLE AS A FRONT
APPROACHES THE TERMINAL AFTER 05Z. /64

&&

.MARINE...THE SMALL CRAFT ADVISORY FOR WINDS AND HAZARDOUS SEAS
WAS EXTENDED TO LATE TONIGHT. EXPECT TO SEE CONTINUED GUSTS OF 25
KT OVER THE WATERS. SEAS ARE CURRENTLY RUNNING AROUND 12 FT AND
IS EXPECTED TO BUILD INTO THE MID TEENS THIS AFTERNOON. A STRONG
FRONT WILL MOVE ACROSS THE WATERS THIS EVENING AND TONIGHT. AS THE
FRONT APPROACHES THE WATERS WE CAN EXPECT THE SEAS TO CLIMB ABOVE
20 FT THIS EVENING WITH SOLID GALE GUSTS TO 45 KT EXPECTED AFTER
MIDNIGHT. AS SUCH...ISSUED A GALE WATCH STARTING LATE TONIGHT
THROUGH SATURDAY AFTERNOON. SEAS WILL SLOWLY SUBSIDE ON SATURDAY
AFTERNOON AND EVENING WITH WINDS RELAXING TO AROUND 25 KT
OVERNIGHT. THE ACTIVE WEATHER PATTERN CONTINUES INTO MONDAY.
HOWEVER...CONDITIONS WILL NOT BE AS INTENSE. /64

&&

.PQR WATCHES/WARNINGS/ADVISORIES...
OR...HIGH SURF ADVISORY FROM 10 AM THIS MORNING TO 4 PM PST SATURDAY 
     FOR CENTRAL OREGON COAST-NORTH OREGON COAST.

WA...HIGH SURF ADVISORY FROM 10 AM THIS MORNING TO 4 PM PST SATURDAY 
     FOR SOUTH WASHINGTON COAST.

PZ...GALE WATCH FROM LATE TONIGHT THROUGH SATURDAY AFTERNOON FOR 
     COASTAL WATERS FROM CAPE SHOALWATER WA TO FLORENCE OR OUT 60 NM.

     SMALL CRAFT ADVISORY FOR WINDS UNTIL 1 AM PST SATURDAY FOR 
     COASTAL WATERS FROM CAPE SHOALWATER WA TO FLORENCE OR OUT 60 NM.

     SMALL CRAFT ADVISORY FOR HAZARDOUS SEAS UNTIL 1 AM PST SATURDAY 
     FOR COASTAL WATERS FROM CAPE SHOALWATER WA TO FLORENCE OR OUT
     60 NM.

     SMALL CRAFT ADVISORY FOR ROUGH COLUMBIA RIVER BAR UNTIL 6 PM
     PST SATURDAY.

&&

$$

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.

[ W WA | SW WA and W OR | SE WA and NE OR | NE WA and N ID ]

Southeastern Washington and Northeastern Oregon


728 
FXUS66 KPDT 191803 AAA
AFDPDT

AREA FORECAST DISCUSSION...UPDATED
NATIONAL WEATHER SERVICE PENDLETON OR
1000 AM PST FRI DEC 19 2014

UPDATED AVIATION DISCUSSION

.SHORT TERM...MORNING UPDATE...THE LATEST PACIFIC SYSTEM CONTINUES 
TO MOVE THROUGH THE EASTERN END OF OUR AREA WITH THE STEADIEST 
PRECIP FROM THE EASTERN BLUE MOUNTAIN FOOTHILLS EASTWARD. ELSEWHERE 
PRECIP IS LIGHT AND SPOTTY. UPSLOPE FLOW WILL KEEP PRECIP CHANCES 
HIGH NEAR THE CASCADE CREST AND IN THE NORTHEASTERN MOUNTAINS INTO 
THE AFTERNOON. HAVE ADJUSTED POPS TO INDICATE A GRADUAL DECREASE 
THROUGH THE DAY BETWEEN THE CASCADE EAST SLOPES AND THE EASTERN 
MOUNTAINS. SNOW LEVELS REMAIN BETWEEN 2500 AND 2800 FEET OVER 
CENTRAL WASHINGTON, BUT SHOULD RISE TO NEAR 3000 FEET THIS 
AFTERNOON. ELSEWHERE EXPECT SNOW LEVELS TO RUN BETWEEN 4000 AND 5000 
FEET THROUGH THE DAY. AS SUCH HAVE ADJUSTED SNOW LEVELS WITH THIS 
UPDATE. SNOW AMOUNTS TODAY WILL BE 3 INCHES OR LESS WITH THE HIGHER 
AMOUNTS OVER THE NORTHERN BLUES ABOVE 5000 FEET. WINDS OVER THE 
BASIN WILL REMAIN LIGHT TODAY, BUT MIXING WILL GRADUALLY IMPROVE. 
MIXING WILL CONTINUE TO IMPROVE THROUGH THE WEEKEND WITH INCREASING 
WINDS. THUS WILL ALLOW THE AIR STAGNATION ADVISORY END AT 10 AM. 
PATCHES OF FOG, WITH VERY LIMITED DENSE FOG, WILL GRADUALLY 
DISSIPATE THROUGH THE MORNING AND EARLY AFTERNOON. 90 

&&

.AVIATION...18Z TAFS...A COLD FRONT IS MOVING ACROSS THE LOWER 
COLUMBIA BASIN THIS MORNING WITH KPDT RADAR SHOWING RAIN AHEAD OF 
THE FRONT ALONG THE FOOTHILLS OF THE NORTHERN BLUE MOUNTAINS AND -RA 
AT KPDT AND KALW, WHICH SHOULD END BY 20Z. AREAS OF MVFR/IFR 
CIGS/VSBY IN FOG AND LOW STRATUS ARE EXPECTED FOR REMAINDER OF THIS 
MORNING WITH SOME IMPROVEMENT AFTER 20Z TO VFR. HOWEVER, KYKM IS 
EXPECTED TO REMAIN MVFR/IFR THROUGH THIS AFTERNOON. AFTER 03Z/20TH 
EXPECT CIGS TO LOWER  TO MVFR/IFR WITH SOME FOG THROUGH OVERNIGHT. 
LIFR VSBYS ARE NOT EXPECTED SATURDAY MORNING.  POLAN

&&

.LONG TERM...PREVIOUS DISCUSSION...AN UPPER LEVEL RIDGE WILL BUILD 
OVER THE PACIFIC NORTHWEST SUNDAY THROUGH TUESDAY. THIS WILL RESULT 
IN MILD TEMPERATURES FOR THIS TIME OF YEAR AND HIGH SNOW LEVELS. 
THERE WILL STILL BE PLENTY OF MOISTURE AND RAINFALL ON SUNDAY AND 
SUNDAY NIGHT. HEAVY AMOUNTS OF RAIN ARE LIKELY IN THE MOUNTAINS. IT 
WILL ALSO BE WINDY SUNDAY MORNING WITH AT LEAST ADVISORY LEVEL WINDS 
POSSIBLE. A SLIGHT DRYING TREND WILL FOLLOW FOR MONDAY AND TUESDAY 
WITH JUST A CHANCE OF MAINLY MOUNTAIN SHOWERS. ON WEDNESDAY A 
MODERATELY STRONG SHORTWAVE TROUGH WILL MOVE ACROSS THE AREA 
USHERING IN MUCH COLDER AIR BY WEDNESDAY NIGHT WITH RAIN CHANGING TO 
SNOW AREAWIDE. THE SNOW WILL LINGER IN THE EAST ON CHRISTMAS DAY. AS 
OF NOW IT LOOKS LIKE SNOW ACCUMULATIONS WILL BE MOSTLY LIGHT. IT 
WILL BE COLD THURSDAY NIGHT AND FRIDAY WITH BELOW NORMAL 
TEMPERATURES AND MOSTLY DRY CONDITIONS. 

&&

.PRELIMINARY POINT TEMPS/POPS...
PDT  46  34  49  43 /  80  20  80  80 
ALW  48  36  48  43 /  80  20  80  80 
PSC  47  36  48  40 /  60  10  80  50 
YKM  43  32  42  33 /  30  20  80  40 
HRI  47  35  49  41 /  60  20  80  50 
ELN  41  31  39  31 /  30  20  80  70 
RDM  45  33  48  39 /  60  30  80  60 
LGD  45  34  42  38 /  80  20  90  90 
GCD  46  33  42  39 /  80  20  80  90 
DLS  47  36  46  41 /  50  30  90  70 

&&

.PDT WATCHES/WARNINGS/ADVISORIES...
OR...NONE.
WA...NONE.

&&

FOR ADDITIONAL WEATHER INFORMATION, CHECK OUR WEB SITE AT...
WWW.WEATHER.GOV/PENDLETON

$$

90/78/99




[ W WA | SW WA and W OR | SE WA and NE OR | NE WA and N ID ]

Northeastern Washington and Northern Idaho


104 
FXUS66 KOTX 191216
AFDOTX

Area Forecast Discussion
National Weather Service Spokane WA
414 AM PST FRI DEC 19 2014

.SYNOPSIS...
A more active weather pattern will continue into early next week.
Another weather system will bring snow to the mountains with
mainly rain for the valleys tonight into Friday. A stronger storm
Saturday into Sunday will bring mainly rain for the valleys...as
well as mountain snow with rising snow levels. Temperatures are
expected to remain above average through early next week...before
dropping down towards normal values by Christmas Day.

&&

.DISCUSSION...
Today through Saturday night...This will be an active and very wet
period as a pair of storm systems move through the forecast area.
The first today followed by the second Saturday. This will result
in measurable precipitation for all locations, with valley rain
and mountain snow.

For Today and Tonight a vigorous frontal system will move through
the forecast. The warm over-running precipitation moved into the
region last evening and satellite imagery shows the cold front
moving onto the Cascades early this morning. This front will cross
the Cascades around 12z and should be east into Montana by this
afternoon. So expect drying from the west beginning near sunrise
then traversing the forecast area through the day. Temperatures
will be on the warm side with highs around 10 degrees above normal

* Precipitation: Yes and for just about all locations. With an
  upper level jet paralleling the front and southerly low level
  flow early this morning even the normally shadowed out lower
  east slopes and deep basin will see measurable precipitation. As
  the cold front moves through the region later this morning the
  flow will shift the focus of the heaviest precipitation across
  the northern mountains and finally the Panhandle mountains this
  afternoon and this evening. Precipitation amounts will range
  from .10-.20 for the low lands with anywhere from .25-.50 for
  the mountains, and possibly as much as .75 near the crest of the
  Cascades. Some showers will linger across the Panhandle
  mountains this evening, otherwise there will be a brief break in
  the wet weather.

* Precipitation type: Warm air advection and southerly flow will
  result in snow levels at or above 3-4k feet for valley rain and
  mountain snow. The area of concern will be for the Methow valley
  where the cooler air remains trapped, but even there
  temperatures are around freezing or a little more and any snow
  that falls will be wet. So a couple of inches for the Methow
  valley this morning and 3-6 inches for the mountains above 3-4k
  feet.

...A strong winter storm expected to result in heavy rain and 
mountain snow across the Northwest this weekend...

Moving on to Saturday and Saturday night...this storm system is
shaping up to be much wetter as the westerly flow will tap into
an atmospheric river of very deep moisture. Model guidance has
been pretty consistent the past several runs showing this moisture
reaching the Cascades early Saturday morning and over-running the
remainder of the region during the day Saturday. Isentropic up-
glide will be quite impressive and combined with the deep moisture
means that everyone will get pretty wet.

* Precipitation: Yes and quite a bit. Through the entire event
  the Cascades can expect anywhere from 1-3 inches of liquid and
  perhaps more near the crest. The northern and Panhandle
  mountains .50-1.5 inches and for the low lands around a half
  inch from Saturday morning through Sunday morning.

* Precipitation type: Behind the first cold front temperatures
  will cool down with snow levels dropping down to 2.5-3.0K feet
  across the south and 1.5-2K feet across the north. Strong warm
  air advection will result in snow levels increasing through the
  day Saturday and finally rising above 6-7k feet across the
  south, but still only around 3.5-4k feet across the north. The
  challenge will again be the Methow valley where the cooler air
  will be tougher to scour out. The models continue to be a little
  too cold for the Methow and I chose to go above guidance in
  these areas, and secondly with this much precipitation and warm
  air advection I would think these areas should mix out pretty
  well. Still there should be an extended period of snow
  accumulation for the Methow valley with moderate snow
  accumulations possible. For the remainder of the mountain
  valleys it looks like they might start out with a snow/rain mix
  but quickly transition over the rain. Snow amounts in the
  Cascades could be in the 1-2 foot range above 4k feet and up to
  a foot or maybe slightly more for the northeast and panhandle
  mountains by Sunday morning. The Methow could see as much as 5-7
  inches.

* Winds: 850 mb winds will climb up to around 40-45kt. The
  question will be if these winds can mix to the surface. Without
  a robust cold front this will be tough. So winds Breezy to even
  windy in locations but likely not advisory speed.

* Temps: Very warm for the season with highs in the 40s on
  Saturday and 40-50 on Sunday. This will be 10-20 degrees above
  seasonal normals. Tobin
 

Sunday and Sunday night...A cold front plows across the Inland 
Northwest on Sunday, helping to shunt the bulk of the moisture 
from the atmospheric river south and east of the region. Gusty 
westerly winds will develop by Sunday afternoon and evening with 
gusts to 30 kts. Under the west to northwest flow, precipitation 
will still be confined to the orographic favored areas like the 
Cascades crest, the Blue mountains and the central Idaho Panhandle. 
Snow levels will be relatively high with mainly valley rain and
mountain snow. The only exception would be some high valley snow
in the far northern valleys Sunday morning, but it looks the
combination of the winds from the frontal passage and arrival of
the drier air, will help mix out that colder air and help shut off
the additional low elevation snow accumulations in the northern
valleys. Also temperatures look to be warmest of the week on
Sunday.

Monday and Monday night..Cooler and drier air to filter in from 
the north, giving the region a break from the precipitation. An 
upper level ridge will slowly migrate across the region. A few 
lingering showers are possible by early Monday morning across the 
northern mountains. Expect temperatures to cool late Monday
night.

Tuesday through the Christmas holiday...The ridge aloft flattens 
allowing for a more active period. One weather disturbance will 
drop down from the northwest with a frontal band pushing through 
the region on Tuesday, skipping across the Columbia Basin but 
targeting the mountains. Chances for snow look good for Tuesday
morning across the northern valleys and mountains, then snow
levels will jump giving way to valley rain and mountain snow again
for Tuesday afternoon and evening. This frontal band will slide
south and stall across the Blue mountains and southern Idaho
panhandle. Meanwhile the models show more energy dropping down
from the Gulf of Alaska and strengthening the northern jet stream,
but what they show happens to the frontal band are two differing
scenarios. The GFS continues the trend that this northern
disturbance will carve out a deeper trough which digs further
south and pushes the boundary further into Oregon, and leaving
much of the Inland Northwest drier. The 00Z ECMWF bounced back its
solution and shows the frontal band lifting northward and bringing
a return of precipitation, mostly in the form of snow, back into
the Inland Northwest. To avoid bouncing forecasts around, opted to
lean more toward climatology gives most areas a chance of snow for
Christmas eve day, then tapering off by Christmas eve night,
although confidence is marginally poor. A drier northwest flow
aloft will move into the region with cooler, more seasonal
temperatures into the end of the week. /rfox.

&&

.AVIATION...
12Z TAFS: A frontal system is moving through the eastern portions
of the area this morning. Light to moderate precipitation will
effect the eastern TAF sites for a few more hours...otherwise
expect drying from the west. Current VFR/MVFR conditions for the
eastern zones will begin to decrease MVFR/IFR after 15z as the
rain comes to an end and fog/stratus develops. Improvement to VFR is
expected after 22z. Stratus/fog will reform after 06z lowering
conditions back to IFR. Current IFR/LIFR conditions for KMWH/KEAT
may not see as much improvement. Cigs/vsby may increase to MVFR
at KEAT after 21z...but the fog/stratus is expected to reform
around 06z again tonight. Tobin

&&

.PRELIMINARY POINT TEMPS/POPS...
Spokane        41  33  40  38  46  36 / 100  10  90 100  50  20 
Coeur d'Alene  41  33  39  36  44  36 / 100  20  90 100  70  50 
Pullman        44  34  42  40  50  41 / 100  10  90 100  70  60 
Lewiston       46  33  45  42  54  43 /  90  10  80 100  70  70 
Colville       39  32  36  34  41  31 / 100  20 100  90  50  20 
Sandpoint      37  32  37  34  40  34 / 100  30  80 100  70  60 
Kellogg        38  31  38  34  41  36 / 100  40  80 100 100  90 
Moses Lake     44  34  41  39  47  36 /  50  10  90  50  30  20 
Wenatchee      42  32  37  37  45  36 /  30  20  90  60  40  20 
Omak           38  30  34  34  39  32 /  80  20  90  80  30  20 

&&

.OTX WATCHES/WARNINGS/ADVISORIES...
ID...None.
WA...Air Stagnation Advisory until Noon PST today for East Slopes 
     Northern Cascades-Moses Lake Area-Northeast Mountains-
     Okanogan Highlands-Okanogan Valley-Upper Columbia Basin-
     Waterville Plateau-Wenatchee Area.

&&

$$


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