Area Forecast Discussion
Issued by NWS Portland, OR

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FXUS66 KPQR 222250
AFDPQR

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE PORTLAND OR
249 PM PST MON DEC 22 2014

.SYNOPSIS...UPPER LEVEL HIGH PRESSURE IS BUILDING OVER THE NE PAC AND
PAC NW TODAY. THE STALLED FRONTAL BOUNDARY ASSOCIATED WITH THE HEAVY
RAINFALL EVENT THIS WEEKEND WILL LIFT NORTH AGAIN LATE TONIGHT AS A
WEAK FRONT AND MAY PRODUCE SOME AREAS OF LIGHT RAIN. THE NEXT COLD
FRONT WILL MOVE INTO WESTERN WASHINGTON ON TUESDAY AND BEGIN TO
AFFECT THE FAR NORTH PART OF OUR FORECAST AREA...SLOWLY SAG FARTHER
SOUTH INTO OUR AREA TUESDAY NIGHT...THEN SWEEP THROUGH SW WASHINGTON
AND NORTHWEST OREGON WITH A GOOD SHOT OF RAIN AND LOWERING SNOW
LEVELS ON WEDNESDAY AND EARLY WEDNESDAY NIGHT. ANOTHER DISTURBANCE
WILL BRING INCREASED SHOWERS TO THE AREA THURSDAY NIGHT AND FRIDAY.
THEN ANOTHER DECENT SYSTEM IS LIKELY TO MOVE THROUGH FRI NIGHT AND
SAT. SNOW LEVELS WILL BE LOWERING DURING THE SECOND HALF OF THE
WEEK...POSSIBLY AFFECTING THE CASCADE FOOTHILLS AND THE COAST RANGE.
OFFSHORE FLOW MAY DEVELOP LATE NEXT WEEKEND INTO EARLY NEXT
WEEK...BRINGING COLDER AND DRIER WEATHER WEST OF THE CASCADES.
&&

.SHORT TERM...TONIGHT THROUGH THURSDAY...
THE WEATHER HAS CALMED DOWN CONSIDERABLY TODAY AS UPPER LEVEL HIGH
PRES BUILDS OVER THE NE PAC AND PAC NW. THERE ARE PLENTY OF CLOUDS
AROUND...BUT SUN BREAKS HAVE DEVELOPED IN SOME AREAS AT TIMES TODAY.
IT HAS BEEN A FAIRLY DRY AND PLEASANT DAY OVERALL. TEMPS ARE STILL
RUNNING ON THE MILD SIDE...WITH HIGHS OVER THE INTERIOR LOWLANDS A
GOOD 10 DEG ABOVE NORMAL FOR THIS TIME OF YEAR. THE STALLED
BAROCLINIC ZONE TO OUR SOUTH THAT WAS ASSOCIATED WITH THE HEAVY RAIN
EVENT OVER THE WEEKEND WILL LIFT NORTHWARD AGAIN TONIGHT INTO TUE
MORNING AS A VERY WEAK WARM FRONT. THE FCST MODELS CONTINUE TO
SUGGEST THAT SOME AREAS OF VERY LIGHT RAIN OR DRIZZLE WILL
DEVELOP...WITH THE BEST CHANCES ALONG THE COAST. HOWEVER...FOR THE
AREAS THAT DO SEE PRECIP...TOTALS SHOULD ONLY BE ON THE ORDER OF A
FEW HUNDREDTHS OF AN INCH. VISIBLE SATELLITE SHOWS HIGH CLOUDS MOVING
OVER THE REGION THIS AFTERNOON...BUT STILL THINK AREAS OF LOW STRATUS
AND FOG WILL FORM OVER THE INTERIOR LOWLANDS AND COAST TONIGHT.
SURFACE DEW POINTS REMAIN IN THE MID TO UPPER 40S...SO IT WON/T TAKE
THAT MUCH COOLING TO SATURATE THE LOWER LEVELS.

THE NEXT SIGNIFICANT SYSTEM TO AFFECT THE REGION WILL ARRIVE LATE TUE
INTO WED. A SLOW-MOVING COLD FRONT WILL SAG SOUTH ONTO THE S
WASHINGTON COAST TUE AFTERNOON AND EVENING. THEN A FAIRLY SHARP UPPER
LEVEL SHORTWAVE WILL DRIVE THE FRONT THROUGH THE REGION ON WED.
EXPECT A FAIRLY BRIEF PERIOD OF HEAVY PRECIPITATION OVER THE REGION
DURING THE DAY. THE HEAVIEST PRECIPITATION APPEARS TO GO SOUTH OF US.
BUT A WIDESPREAD 0.5 TO 1 INCH OF PRECIPITATION OVER SW WASHINGTON
AND NW OREGON APPEARS TO BE A GOOD ESTIMATE AT THIS TIME. THEN
SHOWERS WILL REMAIN WED NIGHT INTO THU...ESPECIALLY OVER THE HIGHER
TERRAIN. SNOW LEVELS WILL DROP DOWN BELOW THE CASCADE PASSES BEHIND
THE FRONT...POTENTIALLY INTO THE HIGHER ELEVATIONS OF THE FOOTHILLS
AND COAST RANGE. EXPECT SEVERAL INCHES OF SNOW FOR THE CASCADE
PASSES THROUGH THU...BUT ACCUMULATIONS SHOULD STAY BELOW ADVISORY
THRESHHOLDS. PYLE

&&

.LONG TERM...THU NIGHT THROUGH MONDAY...A WEAK SHORTWAVE DROPPING
DOWN OUT OF BRITISH COLUMBIA MAY BRING A PERIOD OF HEAVIER SHOWERS
THU NIGHT INTO FRI. SNOW LEVELS WILL REMAIN WELL BELOW THE CASCADE
PASSES. CONFIDENCE IS INCREASING THAT ANOTHER MORE ORGANIZED SYSTEM
WILL MOVE THROUGH FRI NIGHT INTO SAT. THIS SHOULD BRING ANOTHER SHOT
OF RAIN AND MOUNTAIN SNOW. AT THIS TIME...IT APPEARS THAT ADVISORY
LEVEL SNOWFALL ACCUMULATIONS WILL BE POSSIBLE FOR THE CASCADES. THE
FCST MODELS CONTINUE TO INDICATE HIGH PRES WILL BUILD OVER THE NE PAC
LATE NEXT WEEKEND OR EARLY NEXT WEEK...WITH A FAIRLY COLD AIR MASS
MOVING IN EAST OF THE CASCADES. CONTINUED TO TREND THE FCST TOWARD A
DRIER AND COOLER OFFSHORE FLOW PATTERN FOR THIS TIME PERIOD. PYLE
&&

.AVIATION...MAINLY VFR ACROSS THE FORECAST AREA THIS AFTERNOON...
THOUGH THERE ARE SOME AREAS OF SCT-BKN STRATOCUMULUS AROUND
015-020 AGL. WITH LOW-LEVEL AIR MASS REMAINING MOIST AND WINDS
REMAINING LIGHT...EXPECT IFR TO REDEVELOP MOST AREAS OVERNIGHT.
HOWEVER SOME -RA/-DZ FROM A WEAK WARM FRONT MAY CONTRIBUTE TO
LOWER CIGS/VSBYS LATER TONIGHT AND EARLY TUE MORNING AS THE FRONT
LIFTS NORTHWARD ACROSS THE DISTRICT.

KPDX AND APPROACHES...VFR PREVAILING WITH SCT-BKN CLOUDS AROUND
015-020 AGL POSSIBLY RESULTING IN BRIEF PERIODS OF MVFR.
CONDITIONS EXPECTED TO DETERIORATE TO IFR/LOW MVFR OVERNIGHT AS
FOG AND LOW CLOUDS RE-FORM ACROSS THE KPDX METRO. SOME -RA/-DZ MAY
CONTRIBUTE TO LOW CIGS/VSBYS BY 12Z TUE MORNING.  WEAGLE

&&

.MARINE...HIGH PRESSURE LEADING TO LIGHT WINDS OVER WATERS TODAY.
WARM FRONT WILL LIFT N ACROSS THE WATERS TONIGHT...WITH ANOTHER
RIDGE OF HIGH PRESSURE POKING NORTHWARD FROM THE CALIFORNIA
WATERS. APPROACHING COLD FRONT COULD PUSH S WINDS TO SCA CRITERIA
IN OUR NORTHERN WATERS TUE AFTERNOON AND EVENING...BUT IT WILL BE
MARGINAL SO LEFT THE DECISION TO LATER SHIFTS. SOME MODELS ARE
DEVELOPING LOW PRESSURE ALONG THE FRONT AS IT PUSHES ACROSS THE S
OR/N CA WATERS...WHILE STRONG HIGH PRESSURE BUILDS IN BEHIND THE
FRONT. THIS COULD RESULT IN GUSTY N-NW FLOW MIDWEEK. A BIT OF A
BREAK IN THE WEATHER IS EXPECTED THU INTO EARLY FRI...BUT MODELS
ARE STARTING TO AGREE THAT A STRONGER LOW PRES/FRONTAL SYSTEM MAY
PUSH THROUGH THE COASTAL WATERS LATER FRI INTO SAT.

RESIDUAL SWELL FROM THE STORM SYSTEMS IN THE GULF OF ALASKA LAST
FRI/SAT CONTINUES TO PRODUCE 10-13 FT SEAS WITH PERIODS AROUND 13
SECONDS. NEXT SWELL FRONT FROM A SYSTEM NEAR THE ALEUTIANS WILL
ARRIVE THIS EVENING...KEEPING W-NW SWELL 10-13 FT THROUGH TUE.
THEREFORE THE SCA FOR SEAS WILL CONTINUE THROUGH TUE...POSSIBLY
LONGER IF LOW PRES DEVELOPS NEAR HAIDA GWAII TUE AS THE 00Z/12Z
GFS AND NOW THE 12Z ECMWF HAVE BEEN SUGGESTING. BASED ON THE
LATEST 12Z ENP WAVE GUIDANCE...IT APPEARS W-NW SWELL WILL BUILD TO
AROUND 12-15 FT BY WED NIGHT. WITH 12Z ECMWF/GFS IN FAIRLY GOOD
AGREEMENT...WE HAVE NO GOOD REASON TO DOUBT THE 12Z ENP OUTPUT...
SO OUR FORECAST MIRRORS THE ENP FORECAST PRETTY CLOSELY.  WEAGLE

&&

.PQR WATCHES/WARNINGS/ADVISORIES...
OR...COASTAL FLOOD ADVISORY UNTIL 4 PM PST THIS AFTERNOON FOR
     CENTRAL OREGON COAST-NORTH OREGON COAST.

WA...COASTAL FLOOD ADVISORY UNTIL 4 PM PST THIS AFTERNOON FOR
     SOUTH WASHINGTON COAST.

PZ...SMALL CRAFT ADVISORY FOR HAZARDOUS SEAS UNTIL 6 PM PST
  TUESDAY 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 TUESDAY.

&&


$$

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.
COMMONLY REFERRED TO AS THE FORECAST AREA.


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