Area Forecast Discussion
Issued by NWS Portland, OR

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FXUS66 KPQR 290937
AFDPQR

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE PORTLAND OR
236 AM PDT FRI APR 29 2016

.SYNOPSIS...A WEAKENING FRONT WILL BRING LIGHT RAIN TO MOST AREAS
TODAY. THERE WILL BE A RETURN TO DRY AND WARM WEATHER OVER THE
WEEKEND AND EARLY NEXT WEEK AS UPPER LEVEL HIGH PRESSURE BUILDS OVER
THE PAC NW. OFFSHORE WINDS WILL DEVELOP LATE IN THE WEEKEND. AN UPPER
LEVEL TROUGH WILL APPROACH THE COAST TOWARD THE MIDDLE OF NEXT
WEEK...BRINGING WARM SOUTHERLY FLOW ALONG WITH THE POTENTIAL FOR
SHOWERS AND POSSIBLY EVEN SOME THUNDERSTORMS.

&&

.SHORT TERM....TONIGHT THROUGH SUNDAY...MID AND HIGH LEVEL CLOUDS
HAVE FILLED IN LAST EVENING AS THE NEXT UPPER TROUGH APPROACHES.
INFRARED SATELLITE LOOP SHOWS THE UPPER TROUGH RUNNING INTO SPLIT
FLOW AS IT APPROACHES THE PACNW. THE SURFACE FRONT APPEARS TO BE
ALONG A LINE FROM NORTHERN VANCOUVER ISLAND AND PASSING ABOUT 300
MILES WEST OF ASTORIA. THE FRONT PASSED BY BUOY 46005 (ABOUT 400
MILES OFFSHORE) AROUND 5 PM THU.  MOISTURE DEPTH IS FAIRLY DEEP WITH
THIS SYSTEM BUT OVERALL WATER CONTENT IS JUST NEAR AVERAGE FOR THIS
TIME OF YEAR...0.7 INCH.  EXPECT 0.1-0.2 INCH RAIN WITH THIS SYSTEM.
AS FAR RAIN TIMING...STARTS AT THE COAST NEAR SUNRISE AND
AROUND MIDDAY FOR INTERIOR LOWLANDS AND CASCADES. RAIN IN THE
SOUTHERN ZONES SHOULD START A LITTLE LATER AND RECEIVE LESS.
THE SNOW LEVEL WILL DROP TO AROUND 4500-5000 FEET SO CASCADE PASSES
SHOULD SEE SOME LIGHT SNOW ACCUMULATION THIS AFTERNOON AND EVENING.
PRECIPITATION DROPS OFF QUICKLY EARLY THIS EVENING BUT SHOWERS
CONTINUE OVER THE CASCADES TONIGHT AND SAT MORNING.

A STRONG UPPER LEVEL RIDGE WILL BEGIN TO NOSE TOWARD THE PAC NW ON
SAT...BEGINNING A TREND TOWARD SUNNY AND MUCH WARMER WEATHER THAT
WILL CONTINUE INTO NEXT WEEK. THINK THAT THERE WILL BE QUITE A FEW
CLOUDS AROUND TO START THE DAY SAT...WITH GRADUAL CLEARING DURING THE
AFTERNOON AS LOW LEVEL FLOW TURNS NORTHERLY. AFTERNOON HIGHS SHOULD
REACH INTO THE UPPER 60S TO NEAR 70 OVER THE INTERIOR...WHILE THE
COAST REMAINS COOLER WITH AN ONSHORE FLOW COMPONENT.

A SURFACE THERMAL TROUGH OVER N CALIF AND S OREGON IS MODELED TO
BUILD NORTHWARD JUST OFF THE COAST SAT NIGHT INTO SUNDAY. THIS SHOULD
ALLOW OFFSHORE FLOW TO DEVELOP...EVEN AT THE COAST...BRINGING CLEAR
SKIES ACROSS THE REGION. THE UPPER LEVEL RIDGE WILL ALSO BE SHIFTING
MORE DIRECTLY OVERHEAD...RESULTING IN A WARMING AIR MASS. TEMPS ON
SUNDAY ARE FCST TO BE WELL ABOVE AVERAGE...REACHING INTO THE LOW 80S
OVER THE INTERIOR AND MID 70S TO NEAR 80 AT THE COAST. /MH PYLE

.LONG TERM...NO CHANGES. PREVIOUS DISCUSSION FOLLOWS...SUNDAY NIGHT
THROUGH THURSDAY. STRONG RIDGING OVER THE PACIFIC NORTHWEST WILL
REMAIN IN PLACE SUNDAY NIGHT THROUGH MONDAY BRINGING DRY SUNNY
WEATHER FOR MOST OF THE AREA. MODEL SOLUTIONS SHOW A SOUTHERLY SURGE
UP THE COAST ON MONDAY MORNING WHICH WOULD BRING LOW CLOUDS AND MAYBE
SOME DRIZZLE ALONG OREGON`S CENTRAL COAST. MODELS SUGGEST SOME SORT
OF CONVECTIVE SHOWERS DEVELOPING IN THE LANE COUNTY CASCADES ON
MONDAY EVENING...BUT WITH NO TRIGGER IT IS HARD TO HAVE CONFIDENCE IN
A FORECAST FOR SHOWERS OR THUNDERSTORMS IN THIS AREA MONDAY
AFTERNOON/EVENING. HAVE INTRODUCED A SLIGHT CHANCE OF SHOWERS IN THE
LANE COUNTY HIGH CASCADES...BUT MORE LIKELY THAN NOT THIS AREA WILL
STAY DRY. TUESDAY THERE IS A BETTER CHANCE FOR SHOWERS DEVELOPING
ACROSS THE AREA IN THE AFTERNOON AS THE TROUGH OFFSHORE GETS CLOSER
TO THE COAST. MODELS SHOW GOOD INSTABILITY WITH THESE SHOWERS MAINLY
IN THE CASCADES DUE TO COOLER ONSHORE FLOW LIMITING INSTABILITY
ELSEWHERE. THEREFORE HAVE INTRODUCED A SLIGHT CHANCE OF THUNDERSTORMS
FOR THE CASCADES TUESDAY AFTERNOON AND EVENING...LIKELY ENDING AROUND
SUNSET TUESDAY NIGHT. WEDNESDAY INTO THURSDAY THE TROUGH OFFSHORE
MOVES ONTO THE WEST COAST BRINGING COOLER SHOWERY WEATHER THROUGH THE
END OF THE WEEK. -MCCOY

&&

.AVIATION...ONSHORE FLOW CONTINUES...WITH MOIST WESTERLY FLOW
ALOFT. A WEAK FRONT WILL PUSH ACROSS THE REGION THIS AM INTO EARLY
THIS AFTERNOON...WITH AREAS OF LIGHT RAIN. OTHERWISE...VFR TODAY
INTO TONIGHT...BUT WILL HAVE AREAS OF MVFR CIGS ON THE COASTAL
STRIP INTO THE COAST RANGE UNTIL 22Z. PRECIPITATION WILL END
LATER THIS EVENING OVER MOST ALL AREAS...WITH CLOUDS BREAKING UP
A BIT.

KPDX AND APPROACHES...VFR TODAY...THOUGH CIGS LOWERING TO LOW VFR
WITH OCCASIONAL LIGHT RAIN AFTER 17Z AS A WEAK FRONT PUSHES INTO
REGION. PRECIP THREAT ENDS LATER THIS EVENING...BUT ONSHORE FLOW
WILL MAINTAIN BROKEN CIGS THROUGH MOST OF TONIGHT.ROCKEY.
&&

.MARINE...COLD FRONT WILL PUSH ACROSS THE COASTAL WATERS THIS AM
AND INLAND BY LATE MORNING. ONCE THE FRONT MOVES ONSHORE... WEST
TO NORTHWESTERLY WINDS WILL INCREASE OVER THE COASTAL WATERS...
ESPECIALLY OVER THE OUTER WATERS. SHOULD SEE WINDS GUST AROUND 25
KT THIS AFTERNOON...WITH SAID GUSTY WINDS SPREADING CLOSER TO
SHORE BY THIS EVENING. WINDS WILL STAY UP THROUGH GOOD PART OF
TONIGHT...THEN GRADUALLY EASE LATE TONIGHT. SEAS WILL HOVER AROUND
10 FT OVER THE OUTER WATERS TONIGHT. WILL EXPAND SMALL CRAFT ADVISORY
FOR WINDS TO ALL COASTAL MARINE ZONES THROUGH TONIGHT...AND FOR
HAZARDOUS SEAS ON THE OUTER WATERS TONIGHT.

WILL SEE BETTER N TO NW WINDS PATTERN FOR SAT AS HIGH PRES RIDGE
OFFSHORE BUILDS AND THERMAL LOW PRES OVER SW OREGON/NW CALIF
STRENGTHENS. THIS WILL BRING A MORE TYPICAL N TO NW WINDS PATTERN
WITH 15 TO 25 KT WINDS...THOUGH STRONGEST WINDS WILL BE S OF
CASCADE HEAD DURING THE AFTERNOON AND EVENING HOURS. AS THE WINDS
PICK UP...SO WILL THE CHOPPY WIND DRIVEN SEAS...REACHING ABOUT 8
TO 10 FT S OF NEWPORT AT TIMES IN THE AFTERNOON/EVENINGS. WILL
LIKELY NEED SMALL CRAFT ADVISORIES FOR GUSTY WINDS AND/OR SEAS
THIS WEEKEND...BUT WILL NOT ISSUE AT THIS POINT.     ROCKEY.

&&

.PQR WATCHES/WARNINGS/ADVISORIES...
OR...NONE.

WA...NONE.

PZ...SMALL CRAFT ADVISORY FOR WINDS THIS AFTERNOON THROUGH TONIGHT
  ON ALL COASTAL WATERS.

     SMALL CRAFT ADVISORY FOR HAZARDOUS SEAS TONIGHT ON THE OUTER
  COASTAL WATERS...OR FROM 10 TO 60 NM OFFSHORE.

&&

$$

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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