Area Forecast Discussion
Issued by NWS Portland, OR

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FXUS66 KPQR 180433
AFDPQR

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE PORTLAND OR
933 PM PDT THU APR 17 2014

.SYNOPSIS...A FAIRLY VIGOROUS COLD FRONT MOVED THROUGH SOUTHWEST
WASHINGTON AND NORTHWEST OREGON THIS EVENING AND WAS NOW EAST OF THE
CASCADES. THE ASSOCIATED UPPER TROUGH WILL MOVE THROUGH OVERNIGHT
WITH SHOWERS DECREASING. WEAK HIGHER PRESSURE WILL BUILD IN FRIDAY
WITH A DRY DAY MOST AREAS...EXCEPT PERHAPS A FEW LINGERING SHOWERS IN
OUR NORTHERN CASCADE FORECAST ZONES. THE NEXT COLD FRONT WILL SPREAD
ONSHORE SATURDAY MORNING AND EARLY AFTERNOON...MOVING EAST OF THE
CASCADES BY SATURDAY EVENING. WEAK HIGHER PRESSURE WILL TRY TO BUILD
IN SATURDAY NIGHT AND ON EASTERN SUNDAY. A WAVE ALONG THE NEXT
FRONTAL SYSTEM MAY BRUSH THE FAR NORTH COAST ZONES LATER SUNDAY INTO
EARLY MONDAY...BUT THEN THE MAIN COLD FRONT WILL STALL OFF THE COAST
AS A LARGE CHUNK OF ENERGY DIGS SOUTH TOWARD CALIFORNIA...FINALLY
MOVING ONSHORE LATE MONDAY INTO TUESDAY. THE PATTERN WILL REMAIN
FAIRLY UNSETTLED NEXT WEEK.
&&

.SHORT TERM...TONIGHT THROUGH SATURDAY...A COLD FRONT HAS MOVED
THROUGH SOUTHWEST WASHINGTON AND NORTHWEST OREGON THIS EVENING...AND
WAS NOW EAST OF THE CASCADES. THERE ARE SOME SHOWER OVER THE COAST
RANGE AND THE CASCADES...BUT AS THE LOW LEVEL FLOW TURNS MORE
NORTHWEST AND AN ASSOCIATED UPPER TROUGH MOVES EAST...THESE WILL
DECREASE OVERNIGHT. CLOUDS ARE NOT VERY SOLID OFFSHORE...AND EXPECT
SOME CLOUD BREAKS OVERNIGHT ESPECIALLY SOUTH OF THE COLUMBIA
RIVER...AND THOSE WILL BE THE BEST AREAS FOR SOME LOCAL FOG FORMING
LATER TONIGHT AND EARLY FRIDAY.

WEAK HIGHER PRESSURE BUILDS IN FRIDAY...BUT SOME NORTHWEST ONSHORE
FLOW REMAINS FOR AWHILE MAINLY NORTH OF THE COLUMBIA RIVER...AND A
FEW SHOWERS MAY LINGER FOR A WHILE FRIDAY IN THE SOUTH WASHINGTON
CASCADES. THERE IS ALSO AN UPPER DISTURBANCE MOVING THROUGH THE WEAK
UPPER RIDGE ON FRIDAY THAT MAY GIVE SOME MID AND HIGH CLOUDS AS
WELL...AND MAY ALSO AFFECT THE LINGERING SOUTH WASHINGTON CASCADE
SHOWERS.

LOOK FOR CLEARING FRIDAY NIGHT AS WE ARE BRIEFLY IN BETWEEN
SYSTEMS...WITH SOME CLOUDS INCREASING LATE FRIDAY NIGHT AHEAD OF THE
NEXT SYSTEM.

THE MODELS ARE LOOKING PRETTY CONSISTENT WITH THE NEXT FRONT FOR
SATURDAY. TIMING LOOKS CONSISTENT AS WELL. IT LOOKS AS THOUGH THE
RAIN WILL DEVELOP PRETTY EARLY SATURDAY ON THE COAST...AND REACH THE
INLAND VALLEYS IN THE MID TO LATE MORNING ON SATURDAY. THE FRONT
MOVES THROUGH AT A DECENT PACE ON SATURDAY...AND APPEARS TO BE EAST
OF THE CASCADES BY SATURDAY EVENING AS THE PARENT UPPER SHORT WAVE IS
ALREADY MOVING INTO CENTRAL OREGON BY 00Z SUNDAY. HAVE THEREFORE MADE
SOME ADJUSTMENTS TO THE FORECAST GRIDS FOR SATURDAY TO ACCOUNT FOR
THE CONFIDENCE IN MORE DETAILED TIMING. TOLLESON

.LONG TERM...NO CHANGES. PREVIOUS DISCUSSION FOLLOWS...
SATURDAY NIGHT THROUGH WEDNESDAY...TOPSY-TURVY WEATHER CONTINUES SAT
NIGHT AS WEAK 500 MB RIDGING TRIES TO FORM OVER THE PAC NW AND
SURFACE HIGH PRESSURE AGAIN TAKES CONTROL. A DEEPENING GULF OF ALASKA
TROUGH WILL HELP AMPLIFY THE RIDGE A BIT MORE SUN. SW WA ZONES STILL
VULNERABLE TO SOME LIGHT PRECIP SUNDAY...BUT THE MORE SOUTH ONE
TRAVELS THE MORE SUNSHINE THERE SHOULD BE AND TEMPS AGAIN WARM BACK
TO THE LOWER 60S. AS THE FLOW AMPLIFIED MORE MONDAY...WE COULD HAVE
ANOTHER DRY MORNING...WITH A WEAK COLD FRONT WHICH LOOKS TO TRIGGER
SOME SHOWERS IN THE AFTERNOON...ESPECIALLY FOR THE CASCADES...WITH A
BETTER THREAT INLAND ELSEWHERE IN THE EVENING.

LOOKS LIKE MUCH OF THE EXTENDED IS CHARACTERIZED BY COOL AND DAMP
CONDITIONS AS A DEEP UPPER LOW PARKS ITSELF IN THE GULF OF
ALASKA...AND SENDS WAVES OF SHOWERS THROUGH THE AREA. EXPECT NEAR TO
BELOW NORMAL TEMPERATURES THROUGH MUCH OF THE PERIOD..WITH THE
POTENTIAL FOR SOME ACCUMULATING SNOWS IN THE CASCADES AS SNOW LEVELS
WILL BE DOWN NEAR THE PASSES BEGINNING LATE MONDAY NIGHT INTO
TUESDAY. /KMD
&&

.AVIATION...A COLD FRONT AND ASSOCIATED WIND SHIFT TO THE W/NW HAS
MOVED THROUGH THE WILLAMETTE VALLEY THIS EVENING AND IS NOW PUSHING
INTO THE CASCADES. CONDITIONS HAVE IMPROVED TO VFR FOR MANY INLAND
SITES BEHIND THE FRONT...WHILE MAINLY MVFR IS BEING OBSERVED AT THE
COAST. EXPECT SCATTERED SHOWERS ALONG WITH A MIX OF VFR AND MVFR
CONDITIONS THROUGH THE REST OF THE EVENING...ESPECIALLY AT THE COAST
AND FOR THE NORTHERN VALLEY. PARTIAL CLEARING OVERNIGHT ALONG WITH
WEAKENING WINDS WILL LIKELY LEAD TO PATCHY FOG OR LOW STRATUS
DEVELOPMENT BETWEEN 09Z AND 12Z...WITH THE BEST CHANCE OVER THE
CENTRAL AND SOUTHERN WILLAMETTE VALLEY. EXPECT CONDITIONS TO IMPROVE
BY 16Z TO 18Z TOMORROW AND REMAIN VFR AS BRIEF HIGH PRES MOVES INTO
THE REGION.

KPDX AND APPROACHES...EXPECT VFR WITH A BRIEF PERIOD OF MVFR POSSIBLE
PASSING SHOWERS THROUGH ABOUT 06Z TO 09Z. PARTIAL CLEARING OVERNIGHT
WILL LIKELY BRING LOW STRATUS OR FOG BETWEEN 09Z AND 12Z. EXPECT VFR
TO REDEVELOP BETWEEN 16Z AND 18Z AND REMAIN THROUGH THE REST OF THE
DAY. PYLE
&&

.MARINE...A COLD FRONT PUSHED ONSHORE DURING THE LATE AFTERNOON AND
EVENING. WINDS OVER THE WATERS HAVE NOW SHIFTED TO THE NW AND HAVE
BEGUN TO SUBSIDE BEHIND THE FRONT. THERE ARE STILL A FEW LOCALIZED
GUSTS IN THE 20 TO 25 KT RANGE. SEAS ARE RUNNING JUST ABOUT AS FCST
AT 8 TO 10 FT...WITH THE HIGHEST SEAS OVER THE NORTHERN WATERS. WILL
ALLOW THE EXISTING SMALL CRAFT ADVISORIES FOR WINDS AND SEAS TO RUN
THROUGH THE EXPIRATION TIME OF 06Z. EXPECT WINDS AND SEAS WILL
GRADUALLY DROP OFF OVERNIGHT AS HIGH PRES BUILDS OVER THE WATERS.

THEN EXPECT A FAIRLY QUIET PERIOD FRI INTO EARLY SAT WITH THE HIGH
PRES IN PLACE. ANOTHER FRONT WILL PUSH ACROSS THE WATERS MIDDAY
SATURDAY. EXPECT MORE 25 TO 30 KT WINDS WITH THIS FRONT. A LARGE
WESTERLY SWELL WILL FOLLOW THE FRONT LATE SATURDAY INTO SUNDAY.
LATEST MODEL GUIDANCE BRINGS SEAS BETWEEN 17 AND 20 FT BETWEEN
APPROXIMATELY 2 AM AND 2 PM SUNDAY...BEFORE THEY BEGIN TO SLOWLY
DECREASE. SEAS LOOK TO REMAIN ABOVE 10 FT THROUGH THE FIRST HALF OF
NEXT WEEK THOUGH. PYLE/NEUMAN
&&

.PQR WATCHES/WARNINGS/ADVISORIES...
OR...NONE.
WA...NONE.
PZ...SMALL CRAFT ADVISORY FOR WINDS UNTIL 11 PM PDT THIS EVENING FOR
     COASTAL WATERS FROM CAPE SHOALWATER WA TO FLORENCE OR OUT 60 NM.

     SMALL CRAFT ADVISORY FOR HAZARDOUS SEAS UNTIL 11 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 11 PM
     PDT THIS EVENING.

     SMALL CRAFT ADVISORY FOR ROUGH COLUMBIA RIVER BAR FROM 5 AM TO
     9 AM PDT FRIDAY.

&&

$$

MORE WEATHER INFORMATION ONLINE AT...
    HTTP://WEATHER.GOV/PORTLAND

INTERACT WITH US VIA SOCIAL MEDIA
    WWW.FACEBOOK.COM/US.NATIONALWEATHERSERVICE.PORTLAND.GOV
    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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