Area Forecast Discussion
Issued by NWS Portland, OR

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000
FXUS66 KPQR 311608 CCA
AFDPQR

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE PORTLAND OR
906 AM PDT MON AUG 31 2015

.SYNOPSIS...A WARM FRONT WILL BRING LIGHT RAIN TO AREAS NORTH OF A
TILLAMOOK TO MT HOOD LINE TODAY. ANOTHER FRONT WILL ARRIVE ON TUE...
THEN A SHOWERY AIR MASS FOR WED THROUGH FRI AS AN UPPER LEVEL TROUGH
MOVES ACROSS. DRIER AND WARMER WEATHER RETURNS NEXT WEEKEND.
&&

.SHORT TERM...RADAR AND SURFACE OBSERVATIONS HAVE SHOWN RAIN OVER
WESTERN WA THIS MORNING EXTENDING S INTO EXTREME NW OREGON...WHERE
THE RAIN HAS BEEN ON THE LIGHTER SIDE. RAIN WAS OCCURRING IN AN AREA
OF MOIST ONSHORE FLOW...TO THE N OF A SURFACE RIDGE THAT EXTENDED
WSW TO ENE ACROSS OREGON. MODELS SHOWED THIS PATTERN UNLIKELY TO
CHANGE MUCH TODAY...SO WILL KEEP POPS HIGH IN THE NW CORNER OF THE
FORECAST AREA...AND TAPER POPS OFF QUICKLY TO THE SE.

REMAINDER OF SHORT TERM DISCUSSION UNCHANGED...FRONT WILL STALL OVER
THE REGION TONIGHT...THEN LIFT BACK INTO WASHINGTON STATE. AS
SUCH...RAIN THREAT WILL ALSO LIFT NORTHWARD. BUT WILL KEEP QUITE A
BIT OF CLOUDS OVER REGION TONIGHT.

THE NEXT FRONT WILL MOVE INTO THE REGION LATER TUE. ONCE AGAIN...
WILL CLOUDS INCREASE TUE AM...WITH RAIN THREAT INCREASING OVER REGION
FROM NW TO SE DURING THE DAY. THIS FRONT WILL BRING BETTER THREAT OF
RAIN...BUT AGAIN MAIN AREA OF RAIN WILL BE ON THE COAST AND INLAND
AREAS TO NORTH OF SALEM. ONCE THAT FRONT PASSES LATE TUE
AFTERNOON...AIR MASS WILL COOL...WITH SHOWERY WEATHER ON TAP FOR TUE
NIGHT AND WED. SNOW LEVELS ALSO DROP DOWN TO NEAR 6000 FT...BUT ONLY
EXPECTING MINOR ACCUMULATIONS.

MODELS ALL AGREE ON COOL SHOWERY WEATHER CONTINUE ON WED. MANY AREAS
WILL LIKELY REMAIN IN THE 60S FOR HIGH TEMPERATURES ON WED...EVEN
INLAND. TO EARLY TO TELL YET...BUT WITH COOL AIR MASS OVER THE REGION
AND DECENT INSTABILITY...COULD SEE A FEW THUNDERSTORMS OVER THE
REGION. WILL LET LATER SHIFTS LOOK AT THE POTENTIAL. SEEMS FIRST FEW
DAYS OF SEPTEMBER WILL FEEL LIKELY EARLY OCTOBER.   /QUINTON

.LONG TERM...NO CHANGES. PREVIOUS DISCUSSION FOLLOWS. WEDNESDAY
NIGHT THROUGH SUNDAY. THE UPPER LEVEL TROUGH AXIS WILL REMAIN NEAR
THE COAST LATE WEDNESDAY INTO THURSDAY AND TRIES TO SLIDE
EASTWARD...THOUGH MODELS SUGGEST THIS WILL BE SLOW TO OCCUR AS A FEW
SHORTWAVES ON THE BACK SIDE OF THE TROUGH MAY SLOW THE PROGRESS AS
THE TROUGH SLIDES A BIT SOUTH. THIS WILL BRING CONTINUED COOL...AND
AT TIMES SHOWERY...CONDITIONS TO THE REGION FOR THURSDAY AND
FRIDAY...WITH THE BASE OF THE TROUGH OVERHEAD FRIDAY BEFORE SHIFTING
EAST OF THE CASCADES. HEIGHTS LOOK TO RISE A BIT FOR THE WEEKEND FOR
DRY AND WARMER WEATHER...PERHAPS BACK TO NEAR SEASONAL NORMALS FOR
SUNDAY.   CULLEN
&&

.AVIATION...VFR CONDITIONS INLAND THIS MORNING WITH LOCALIZED MVFR
CIGS FOR THE COAST. EXPECT MORE WIDESPREAD MVFR CIGS FOR THE COAST
EARLY THIS AFTERNOON AS A WEAK WARM FRONT BEGINS TO MOVE INLAND.
EXPECT LOCALIZED AND BRIEF MVFR CIGS INLAND LATE THIS
AFTERNOON...MANLY N OF KHIO. THE FRONT WILL RESULT IN SOUTH WINDS
GUSTING TO AROUND 25 KT ALONG THE N OR AND S WA COASTS BETWEEN 16Z
AND 20Z. S WINDS IN GENERAL WILL BECOME SW THIS EVENING.

A WEAK COLD FRONT WILL APPROACH FROM THE NORTH LATE TONIGHT. S
WINDS WILL GUST TO AROUND 25 KT ALONG THE COAST TUE 9 TO 15Z.S
WINDS WILL RETURN INLAND AROUND 9 Z TO THE NORTH AND 13 TO 14Z
FOR SOUTHERN AREAS. EXPECT MVFR CIGS AS THE FRONT DROPS FROM
NORTH TO SOUTH TUE.

KPDX AND APPROACHES...CLOUDY WITH VFR CONDITIONS THROUGH TUE
MORNING. OCCASIONAL LIGHT RAIN LATE THIS AFTERNOON AND EVENING.
THERE IS A BETTER CHANCE FOR MVFR CIGS WITH A WEAK COLD FRONT TUE
NIGHT. TJ

&&

.MARINE...A WEAK WARM FRONT IS MOVING ACROSS THE WATERS TODAY AND
WILL GENERATE LOW END SMALL CRAFT ADVISORY SOUTHERLY WINDS FOR
NORTH OF CASCADE HEAD THROUGH LATE THIS AFTERNOON. THERE MAY BE
SOME LOCALIZED SMALL CRAFT GUSTS AHEAD OF AN WITH THE NEXT FRONTAL
PASSAGE LATE TONIGHT THROUGH TUESDAY AFTERNOON...BUT DO NOT
ANTICIPATE THE HIGHER GUSTS WILL BE WIDESPREAD OR CONSISTENT
ENOUGH TO WARRANT AN ADVISORY.

SEAS WILL REMAIN RELATIVELY STEEP TODAY AND TONIGHT WITH 7 TO 8 FT
HEIGHTS AND 10 TO 11 SECOND PERIODS. A SURFACE LOW OVER THE GULF
OF ALASKA...JUST OFFSHORE OF YAKUTAT IS GENERATING A NORTHERLY
FETCH THAT WILL BRING A BRIEF PERIOD OF 10 FT SWELL TO THE OREGON
WATERS WEDNESDAY.

SURFACE HIGH PRESSURE WILL BUILD OVER THE NE PACIFIC WED NIGHT
AND THU AS A THERMAL LOW DEVELOPS OVER NORTHERN CALIFORNIA. THIS
WILL BRING A RETURN OF NORTHERLY WINDS TO THE WATERS THURSDAY AND
FRIDAY. A LOW TO THE NORTH WILL PREVENT A TIGHT GRADIENT AND
EXPECT BELOW ADVISORY WINDS THU AND FRI. TJ

&&

.PQR WATCHES/WARNINGS/ADVISORIES...
OR...NONE.
WA...NONE.
PZ...SMALL CRAFT ADVISORY FOR WINDS UNTIL 6 PM PDT THIS EVENING FOR
     COASTAL WATERS FROM CAPE SHOALWATER WA TO CASCADE HEAD OR OUT
     60 NM.

     SMALL CRAFT ADVISORY FOR ROUGH COLUMBIA RIVER BAR UNTIL 9 AM PDT
     THIS MORNING.

     SMALL CRAFT ADVISORY FOR ROUGH COLUMBIA RIVER BAR FROM 5 PM THIS
     AFTERNOON TO 10 PM PDT THIS EVENING.

     SMALL CRAFT ADVISORY FOR ROUGH COLUMBIA RIVER BAR FROM 4 AM TO
     9 AM PDT 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.


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