Area Forecast Discussion
Issued by NWS Portland, OR

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FXUS66 KPQR 231813
AFDPQR

AREA FORECAST DISCUSSION...UPDATED
NATIONAL WEATHER SERVICE PORTLAND OR
1012 AM PST SUN NOV 23 2014

.SYNOPSIS...CONVECTIVE SHOWERS WILL CONTINUE OVER SW WASHINGTON AND
NW OREGON THROUGH THIS MORNING. THESE SHOWERS ARE ASSOCIATED WITH A
SLOW MOVING FRONT THAT WILL STALL OVER NW WASHINGTON BEFORE FALLING
A PART OVER NW OREGON THIS AFTERNOON. RAIN AND MOUNTAIN SNOW IS
EXPECTED FOR WASHINGTON THIS MORNING WITH LESS ACCUMULATIONS FOR
OREGON THIS AFTERNOON. A FLAT UPPER RIDGE WILL BUILD
INTO CALIFORNIA AND OREGON MONDAY AND TUESDAY...BUT SHOULD REMAIN
WEAK ENOUGH FOR SYSTEMS TO CLIP OUR NORTHERN ZONES WITH OCCASIONAL
WET WEATHER. VALLEY INVERSIONS WILL LIKELY BUILD IN THE CENTRAL AND
SOUTH WILLAMETTE VALLEY...WITH FOG POSSIBLY BECOMING MORE PERSISTENT
BY THE MIDDLE OF NEXT WEEK. ANOTHER ORGANIZED FRONT IS EXPECTED FOR
THE THANKSGIVING WEEKEND.

&&

.UPDATE...THE LONE OF CONVECTIVE SHOWERS OVER THE NORTHERN EDGE OF
THE PORTLAND FORECAST AREA IS MOVING SLOWLY SOUTHWARD. A FEW CELLS
ARE SPROUTING UP AHEAD OF THIS LINE. ONE IN PARTICULAR...JUST OFF OF
LONG BEACH WA HAD STRONG ROTATION SIGNATURES INDICATIVE OF A TORNADO
AND A TORNADO WARNING WAS ISSUED AS THE STORM TRACKED INLAND. THE
STORM FINALLY WEAKENED OVER NASELLE WA. WE HAVE RECEIVED NO
OBSERVATIONS NEAR THIS STORM TO VERIFY OR DENY THE PRESENCE OF A
TORNADO. ONE SPOTTER JUST NORTH OF LONG BEACH HAD PEA-SIZE HAIL AND
LIGHTNING AND DID NOT SEE THE ROTATION. HOWEVER...THE BEST VIEWING OF
ANY ROTATION WOULD BE SOUTH OF THE STORM...AND SOUTH OF LONG BEACH.
VERTICAL SHEAR IN THE ATMOSPHERE WILL CONTINUE A THREAT FOR WEAKLY
ORGANIZED STORMS THROUGH NOON TODAY. MOST OF THESE STORMS WILL BE
OVER THE WATERS...BUT THEY MAY OCCASIONAL MOVE ONSHORE. WE WILL BE
MONITORING RADAR CLOSELY THIS MORNING.

THE FRONT HAS PRODUCED .3 TO .5 INCHES OF RAIN IN THE PAST 3 HOURS
NORTH OF OUR AREA. THE HIGHER AMOUNTS ARE MOST LIKELY ASSOCIATED WITH
THE CONVECTIVE BAND. HOWEVER STILL THINK THE SW WASHINGTON CASCADES
WILL SEE SOME SNOW ACCUMULATIONS ABOVE 4000 FEET AND HAVE NOT MADE
ANY CHANGES TO THE WINTER WEATHER ADVISORY WITH THE UPDATE.
ELSEWHERE...EXPECT COOL AND RAINY CONDITIONS THROUGH THIS EVENING.

HIGH PRESSURE BEGINS TO BUILD OVER THE EASTERN PACIFIC LATE TONIGHT
INTO MONDAY...WHICH SHOULD KEEP THE REGION FAIRLY DRY BUT CLOUDY. BUT
THE THREAT FOR VALLEY FOG INCREASES...ESPECIALLY FOR THE CENTRAL AND
SOUTH WILLAMETTE VALLEY AS WELL AS THE CENTRAL COAST. MODELS HAVE
BEEN CONSISTENT IN SHOWING A FEW DISTURBANCES RIDING OVER THE RIDGE
AND BRINGING SOME PRECIP MAINLY TO THE FAR NORTHERN FORECAST ZONES BY
MONDAY EVENING. EXPECT THIS PATTERN OF NORTHERN SHOWERS WITH SOUTHERN
VALLEY AND COASTAL FOG TO CONTINUE THROUGH WEDNESDAY. TJ/27

.LONG TERM...WEDNESDAY NIGHT THROUGH SUNDAY...OVERALL MODELS ARE
ATTEMPTING TO FLATTEN THE UPPER LEVEL RIDGE LATE WEDNESDAY. BUT ONCE
WE GET TO THANKSGIVING MORNING...MODEL SOLUTIONS VARY CONCERNING THE
NEXT PACIFIC FRONTAL SYSTEM APPROACHING THE REGION THANKSGIVING DAY.
THE 06Z GFS SHOWS A RATHER WELL-ORGANIZED FRONTAL BAND REACHING THE
SW WASHINGTON/NW OREGON COAST IN THE MORNING...WITH RAIN SPREADING
INLAND BY THE AFTERNOON...RIGHT IN TIME FOR THANKSGIVING DINNER. WILL
HAVE TO SEE WHAT THE 12Z ECMWF DOES WITH THIS SYSTEM...AND WHETHER OR
NOT IT MAINTAINS ITS LIGHTER RAIN/RIDGY SOLUTION. A MUCH
STRONGER AND WETTER SYSTEM LOOKS TO MOVE IN OVER THE WEEKEND WHICH
COULD POSE A THREAT TO TRAVELERS RETURNING AFTER THE THANKSGIVING
HOLIDAY. DETAILS AT THIS POINT ARE STILL UNKNOWN AND WILL BE REFINED
WITH FUTURE UPDATES. THE GOOD NEWS IS THAT TEMPERATURES IN THE
EXTENDED WILL BE AT OR ABOVE SEASONAL NORMALS. /64/27

&&

.AVIATION...CONDITIONS ARE PRIMARILY VFR ACROSS THE REGION THIS
MORNING. A FRONT ALONG THE WASHINGTON COAST AND OVER THE COASTAL
WATERS IS PRODUCING SIGNIFICANT LIGHTNING AND GUSTY WINDS. THE
FRONT IS FCST TO WEAKEN AS IT PUSHES INTO NORTHWEST OREGON LATER
THIS MORNING...BUT IT MAY ALLOW FOR A PERIOD OF MVFR CONDITIONS
AT KAST LATER THIS MORNING AND THE KPDX METRO TAF SITES TOWARDS
MIDDAY. THERE IS A CHANCE MVFR CONDITIONS MAY PERSIST TOWARDS 12Z
MONDAY FOR THE PORTLAND METRO TAF SITES. FARTHER SOUTH WHERE
CLEARING THIS EVENING WILL BE MORE LIKELY TO OCCUR...IFR
CONDITIONS MAY DEVELOP AT KEUG...KSLE AND EVEN KHIO TOWARDS 12Z
MONDAY.

KPDX AND APPROACHES...A POST FRONTAL SHOWERY AIR MASS WILL LEAD
TO PREDOMINANTLY VFR CONDITIONS TODAY. A BAND OF RAIN ASSOCIATED
WITH A DYING FRONT MAY TEMPORARILY REDUCE CIGS INTO MVFR AROUND
MIDDAY. THERE IS A CHANCE THESE CONDITIONS COULD PERSIST WELL
INTO SUNDAY NIGHT...OR PERHAPS DETERIORATE INTO HIGH END IFR
CONDITIONS...BUT CONFIDENCE IN THESE DETAILS IS LOW AT THIS POINT.
PYLE/NEUMAN

&&

.MARINE...A SLOW MOVING FRONT BROUGHT A BAND OF STRONG
THUNDERSTORMS INTO THE W WASHINGTON COASTAL WATERS THIS MORNING.
BASED ON SEVERAL REPORTS OF WINDS IN EXCESS OF 40 MPH WITH SOME OF
THESE STORMS FURTHER NORTH ALONG THE WASHINGTON COAST...DECIDED TO
ISSUE A SPECIAL MARINE WARNING FOR THE WATERS AS FAR SOUTH AS THE
COLUMBIA RIVER BAR. EXPECT PERIODIC GUSTS IN EXCESS OF 34 KT ALONG
WITH FREQUENT LIGHTNING IN SOME OF THE STRONGER STORMS.
OTHERWISE...EXPECT GUSTY WINDS TO CONTINUE OVER THE NORTHERN
COASTAL WATERS INTO EARLY THIS AFTERNOON. THEN WINDS DROP OFF
CONSIDERABLY LATER THIS AFTERNOON AS THE FRONT WEAKENS. SEAS IN
THE 12 TO 13 FT RANGE AT CURRENT WILL LIKELY PEAK IN THE MID TEENS
LATER TODAY BEFORE DECREASING TONIGHT INTO MONDAY.

A WEAK FRONT WILL PUSH INTO THE WATERS LATE MONDAY...BUT ASIDE
FROM SOME SMALL CRAFT ADVISORY LEVEL WIND GUSTS OF 25 KT...NOT
EXPECTING MUCH IMPACT. WINDS MAY STAY A BIT GUSTIER ACROSS THE
NORTHERN WATERS EARLY TO MID WEEK BEFORE A SLOW MOVING LOW PRESSURE
SYSTEM IMPACTS THE WATERS MID TO LATE NEXT WEEK. LOW END GALE FORCE
WIND GUSTS MIGHT BE SQUEEZED OUT OF THIS SYSTEM AT SOME POINT...BUT
THE SCENARIO DOES NOT LOOK ALL THAT PROMISING FOR A SOLID GALE
FORCE OR HIGHER WIND EVENT FOR THE WATERS. PYLE/NEUMAN

&&

.PQR WATCHES/WARNINGS/ADVISORIES...
OR...NONE.
WA...WINTER WEATHER ADVISORY UNTIL 10 PM PST THIS EVENING FOR SOUTH
     WASHINGTON CASCADES.

PZ...SMALL CRAFT ADVISORY FOR WINDS UNTIL 3 PM PST THIS AFTERNOON FOR

     COASTAL WATERS FROM CAPE SHOALWATER WA TO CASCADE HEAD OR OUT
     60 NM.

     SMALL CRAFT ADVISORY FOR HAZARDOUS SEAS UNTIL 9 AM PST MONDAY
     FOR COASTAL WATERS FROM CAPE SHOALWATER WA TO FLORENCE OR OUT
     60 NM.

     SMALL CRAFT ADVISORY FOR ROUGH COLUMBIA RIVER BAR UNTIL 9 AM
     PST 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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