Area Forecast Discussion
Issued by NWS Portland, OR

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000
FXUS66 KPQR 291557
AFDPQR

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE PORTLAND
857 AM PDT SUN MAR 29 2015

.SYNOPSIS...MILD AND MOSTLY DRY WEATHER THROUGH MON AS A FLAT UPPER
LEVEL RIDGE REMAINS OVER THE PAC NW. A COLD FRONT WILL PUSH ACROSS
THE REGION LATE MONDAY USHERING IN A MUCH COOLER AND MORE SEASONABLE
AIR MASS ALONG WITH SHOWERS AND LOWER SNOW LEVELS THAT WILL LAST
THROUGH THE END OF THE WORKWEEK.

&&

.SHORT TERM...WATER VAPOR PICTURES AND UPPER AIR PLOTS SHOWED THE
REGION UNDER A FLAT UPPER RIDGE WITH W FLOW ALOFT. A BAROCLINIC ZONE
TO THE N BROUGHT SOME LIGHT RAIN AS FAR S AS THE OLYMPIC PENINSULA
THIS MORNING. AN EXPECTED WSW FLOW ALOFT TODAY IS NOT LIKELY TO
ALLOW THE BAROCLINIC ZONE TO SPREAD S TODAY...ALTHOUGH VISIBLE
PICTURES DID SHOW SOME LAYERED CLOUDS OFF THE S WA AND FAR N OREGN
COAST THIS MORNING, AS SUCH WILL LEAVE IN A SLIGHT CHANCE FOR SOME
SHOWERS OVER THE SW CORNER OF WA TODAY...WITH THE REST OF THE AREA
EXPECTED TO REMAIN DRY AND MILD TODAY...AND THROUGH MOST OF THE DAY
MON.

AN UPPER LEVEL TROUGH WILL DIVE DOWN FROM THE GULF OF ALASKA ON
MON...FINALLY DRIVING A STALLED FRONTAL BOUNDARY OFF VANCOUVER
ISLAND ONSHORE AS A COLD FRONT. EXPECT RAIN TO PUSH ONTO THE COAST
MON EVENING...THEN INLAND OVERNIGHT ALTHOUGH MODELS CONTINUE TO
TREND SLIGHTLY LATER WITH TIMING OF THE FRONT. THE UPPER LEVEL
TROUGH WILL MOVE THROUGH ON TUE...USHERING IN A SIGNIFICANTLY COOLER
AIR MASS. THE FCST MODELS ARE INDICATING THAT THERE WILL BE PLENTY
OF POSTFRONTAL SHOWERS ACROSS THE REGION ON TUE. FORECAST MODEL
SOUNDINGS SHOW SOME INSTABILITY AND FORCING WITH THE FRONT MONDAY
NIGHT AND A BIT INTO TUESDAY MORNING...BUT IT LOOKS LIKE THERE MAY
BE TOO MUCH OF A CAP TO REALLY PRODUCE ANY THUNDER SO HAVE LEFT IT
OUT FOR NOW. HOWEVER IT MAY BE ONE OF THOSE DAYS WITH PERIODIC HEAVY
SHOWERS...SOME CONTAINING SMALL HAIL. THE COLDER AIR SHOULD ALSO
DROP SNOW LEVELS DOWN TO CASCADE PASSES WHERE SEVERAL INCHES OF
ACCUMULATING SNOW MAY FALL. BOWEN/PYLE

.LONG TERM...NO CHANGES. PREVIOUS DISCUSSION FOLLOWS. TUESDAY NIGHT
THROUGH FRIDAY...A PROGRESSIVE PATTERN IS EXPECTED FOR THE EXTENDED
FCST PERIOD. BEHIND THE UPPER LEVEL TROUGH ON TUE...FCST CONFIDENCE
IS FAIRLY HIGH THAT ANOTHER SHORTWAVE WILL MOVE ONSHORE
WED...BRINGING CONTINUED SHOWERS AND MOUNTAIN SNOW INTO THU MORNING.
THERE IS THEN A SHORTWAVE UPPER LEVEL RIDGE THAT IS MODELED TO MOVE
INTO THE REGION ON THU. THIS MAY END UP PROVIDING A BRIEF BREAK FROM
THE SHOWER ACTIVITY LATER THU INTO FRI BEFORE A DEEP UPPER TROUGH
MOVES TOWARD THE COAST ON FRI INTO NEXT WEEKEND. FCST CONFIDENCE
BECOMES LOWER TOWARD THE END OF THE WEEK. FRI COULD END UP BEING
MOSTLY DRY...BUT THE FCST MODELS SEEM TO BE TRENDING TOWARD SPEEDING
UP THE ARRIVAL OF THE DEEP TROUGH...WHICH WOULD BRING MORE RAIN
ONSHORE FRI. PYLE

&&

.AVIATION...VFR CONDITIONS EXPECTED TO CONTINUE THROUGH TODAY AND
TONIGHT WITH VARIABLE HIGH CLOUDS. FEW PATCHY AREAS OF GROUND FOG
IN THE CENTRAL OREGON COAST AND COAST RANGE MAY PERSIST UNTIL 17Z.
OTHERWISE...MAY SEE VFR CIGS ALONG THE COAST AT TIMES THIS
AFTERNOON WITH THE POTENTIAL FOR MVFR CIGS DEVELOPING AFT 03Z MON
NORTH COAST NEAR KAST AND A LITTLE LATER FOR KONP AND THE CENTRAL
COAST. MAY AGAIN SEE SOME SHALLOW FOG OR STRATUS LATE
TONIGHT/EARLY MON...PARTICULARLY IN THE SOUTH VALLEY AND CENTRAL
COAST. INCREASING MID/HIGH CLOUDS AFT 12Z MON WITH APPROACHING
FRONTAL SYSTEM.

KPDX AND APPROACHES...VFR CONDITIONS CONTINUE TODAY AND TONIGHT
WITH VARIABLE HIGH CLOUDS. INCREASING MID/HIGH CLOUDS LATE
TONIGHT/EARLY MONDAY AHEAD OF APPROACHING FRONTAL SYSTEM. CULLEN

&&

.MARINE...WINDS HAVE BEGUN TO TURN SOUTHERLY NEAR 15 KT TODAY AND
WILL MAINTAIN INTO THIS EVENING. WINDS WILL AGAIN BE GUSTY OVER
THE NORTHERN OUTER WATERS WHERE THE SURFACE PRESSURE GRADIENT
REMAINS A BIT STRONGER. MEANWHILE...SEAS CONTINUE IN THE 10 TO 12
FT RANGE AND HIGHEST OVER THE OUTER AND NORTHERN PORTIONS OF THE
COASTAL WATERS. SEAS WILL REMAIN NEAR 10 FT OVERNIGHT...SO THE
SMALL CRAFT ADVISORY FOR HAZARDOUS SEAS CONTINUES THROUGH EARLY
MONDAY

SOUTH WINDS INCREASE FURTHER ON MONDAY AHEAD OF THE NEXT FRONTAL
SYSTEM THAT WILL TRANSIT THE WATERS TOMORROW. EXPECT ADVISORY
LEVEL WINDS WITH GUSTS TO 30 KT IN THE AFTERNOON AND EVENING
HOURS. MEANWHILE...SEAS WILL AGAIN PUSH INTO THE 11 TO 12 FT RANGE
BEHIND THE FRONT MONDAY EVENING AND STAY ELEVATED INTO EARLY
TUESDAY. CULLEN

&&

.PQR WATCHES/WARNINGS/ADVISORIES...
OR...NONE.
WA...NONE.
PZ...SMALL CRAFT ADVISORY FOR HAZARDOUS SEAS UNTIL 5 AM PDT MONDAY
     FOR COASTAL WATERS FROM CAPE SHOALWATER WA TO FLORENCE OR OUT
     60 NM.

     SMALL CRAFT ADVISORY FOR ROUGH COLUMBIA RIVER BAR UNTIL
     5 PM PDT THIS AFTERNOON.

     SMALL CRAFT ADVISORY FOR ROUGH COLUMBIA RIVER BAR FROM 11 PM
     THIS EVENING TO 4 AM PDT MONDAY.

&&

$$

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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