Area Forecast Discussion
Issued by NWS Portland, OR

Home | Current Version | Previous Version | Text Only | Print | Product List | Glossary On
Versions: 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50
000
FXUS66 KPQR 211108
AFDPQR

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE PORTLAND OR
308 AM PST SUN DEC 21 2014

.SYNOPSIS...MILD AND VERY WET WEATHER IS EXPECTED TO CONTINUE OVER
SOUTHWEST WASHINGTON AND NORTHWEST OREGON MUCH OF TODAY. RAINFALL
RATES WILL GRADUALLY EASE THROUGH THE DAY...THEN DECREASE MORE
SUBSTANTIALLY TONIGHT AND MONDAY AS AN UPPER RIDGE BUILDS OVER THE
NORTHEAST PACIFIC AND SQUEEZES OFF THE FLOW OF MOISTURE. SEVERAL
RIVERS HAVE REACHED FLOOD STAGE...AND THE THREAT OF FLOODING WILL
CONTINUE THROUGH TODAY AND POSSIBLY INTO TONIGHT BEFORE EASING.
LONGER RANGE MODEL OUTPUT IS SUGGESTING A COLDER AIR MASS WILL SETTLE
OVER THE PACIFIC NORTHWEST LATE NEXT WEEK WITH SNOW DOWN INTO AT
LEAST THE CASCADE FOOTHILLS AND COAST RANGE AS A COOLER SYSTEM FROM
THE NORTHWEST MOVES THROUGH WEDNESDAY.
&&

.SHORT TERM...WARM FRONTAL OVERRUNNING SATURDAY BROUGHT VERY HEAVY
RAIN TO SOUTHWEST WASHINGTON AND NORTHWEST OREGON...AND CAUSED
SEVERAL RIVERS TO REACH FLOOD STAGE. THE WARM FRONT MOVED THROUGH
LATE IN THE DAY SATURDAY...AND TEMPERATURES WARMED DRAMATICALLY IN
MANY AREAS LATE SATURDAY AND OVERNIGHT SATURDAY NIGHT. THE MILD AIR
MASS CONTINUES EARLY THIS MORNING. WESTERLY FLOW CONTINUES TO
TRANSPORT MOISTURE AND PRECIPITATION INTO OUR FORECAST AREA EARLY
THIS MORNING...BUT THE LOW LEVEL FLOW HAS TURNED MORE WESTERLY AND
NATIONAL WEATHER SERVICE DOPPLER RADAR IS SHOWING SOME RAIN SHADOWING
IN THE LEE OF THE COAST RANGE AS A RESULT.

RAINFALL CONTINUES TO BE OROGRAPHICALLY ENHANCED OVER THE COAST RANGE
AND CASCADES...BUT INTENSITIES ARE LESS THAN WHAT WAS SEEN SATURDAY.
THE MODELS ARE SHOWING THAT THE WESTERLY FLOW WILL START TO BUCKLE
TODAY...THEN AMPLIFY INTO A BUILDING UPPER RIDGE IN THE NORTHEAST
PACIFIC TONIGHT AND MONDAY...EASING THE ONSHORE FLOW AND DECREASING
THE PRECIPITATION DRAMATICALLY. THERE WILL PROBABLY BE ENOUGH
PRECIPITATION TODAY TO KEEP A THREAT OF FLOODING ON AREA RIVERS...BUT
SOME WILL BEGIN TO LOSE STEAM AND MAY EVEN CREST. FOR MORE
DETAILS...SEE THE VARIOUS FLOOD BULLETINS IN EFFECT.

HIGH TIDES THIS MORNING IN COMBINATION WITH HIGH FLOW IN COASTAL
RIVERS WILL LIKELY LEAD TO AREAS OF COASTAL FLOODING DUE TO TIDAL
OVERFLOW. WILL CONTINUE THE PREVIOUSLY ISSUED COASTAL FLOOD ADVISORY
FOR THAT TODAY.

EVEN THOUGH THE PRECIPITATION DECREASES CONSIDERABLY MONDAY...THE
ECMWF MODEL DOES HANG ONTO A LITTLE MORE PRECIPITATION THAN THE
GFS...AND HAVE KEPT SOME LOW POPS AS A RESULT ON MONDAY.

THE NEXT SYSTEM STARTS TO DROP INTO THE PACIFIC NORTHWEST ON
TUESDAY...BUT ITS MAIN EFFECTS OF MORE RAIN AND SIGNIFICANTLY
LOWERING SNOW LEVELS WILL OCCUR MAINLY ON WEDNESDAY. TOLLESON
&&

.LONG TERM...NO CHANGES. PREVIOUS DISCUSSION FOLLOWS...
TUESDAY NIGHT THROUGH SATURDAY...MODELS REMAIN CONSISTENT IN
FLATTENING AN UPPER LEVEL RIDGE LATE TUESDAY INTO WEDNESDAY. THERE
ARE SOME MODEL DISCREPANCIES CONCERNING HOW FAR SOUTH THE NEXT
SHORTWAVE WILL MOVE INTO THE PACIFIC NORTHWEST...BUT OVERALL AN UPPER
LEVEL TROUGH WILL SAG SOUTH AND MOVE INLAND EARLY WEDNESDAY. THIS
WILL USHER IN ANOTHER BATCH OF COOL AND RAINY CONDITIONS...WITH SNOW
LEVELS DROPPING TO NEAR 2000 FT SO EXPECT SNOW SHOWERS OVER CASCADE
PASSES RIGHT IN TIME FOR HOLIDAY TRAVEL. AGAIN...HOLIDAY TRAVELERS
HEADED OVER THE CASCADE PASSES WILL CERTAINLY NEED TO MONITOR THE
FORECAST. LINGERING MOISTURE CONTINUES INTO CHRISTMAS DAY...BUT WILL
LIKELY BE OCCASIONAL SHOWERS WITH PARTLY CLOUDY SKIES FOR THE MOST
PART. COLDER NORTHERLY FLOW PERSISTS INTO EARLY NEXT WEEKEND...WITH
DRIER CONDITIONS EXPECTED FOR FRIDAY. A NEW DEVELOPMENT IN THE 12Z
MODEL RUNS HAS BEEN ANOTHER SHORTWAVE DISTURBANCE DROPPING SOUTH OVER
THE FORECAST AREA LATE FRIDAY... BRINGING A THREAT FOR RAIN AND SNOW
ON THE MOUNTAINS. /27
&&

.HYDROLOGY...NUMEROUS FLOOD WARNINGS ALREADY IN EFFECT...INCLUDING
MAJOR FLOODS FOR THE MARYS AND CLACKAMAS RIVERS. FLOODING ALONG THE
MAINSTEM WILLAMETTE LOOKS UNLIKELY AT THIS POINT. SEE THE LATEST
WARNINGS AND FLOOD STATEMENTS FOR DETAILS. A SLOW DECREASE IN RAIN
RATES EARLY THIS MORNING IS EXPECTED TO CONTINUE TODAY. THE RAIN WILL
DECREASE MORE TONIGHT AND MONDAY. EXPECT FLOODING CONCERNS TO START
TO EASE LATER TODAY AND ESPECIALLY TONIGHT AND MONDAY.
&&

.AVIATION...MODERATE ONSHORE FLOW...WITH PLENTY OF MID AND HIGH
CLOUDS OVER REGION. STILL HAVE WIDESPREAD MVFR ON COASTAL AREAS WITH
POCKETS OF MVFR CIGS INLAND. NOT MUCH CHANGE TODAY INTO THIS EVENING.
HIGHER TERRAIN...ESPECIALLY CASCADES...WILL CONTINUE TO BE OBSCURED
IN CLOUDS AND PRECIP THROUGH TONIGHT.

KPDX AND APPROACHES...MOSTLY VFR THROUGH THIS EVENING...WITH SHOWERS.
EXPECT OCCASIONAL BUT BRIEF PERIODS THROUGH 18Z FOR CIGS DROPPING
THROUGH 18Z TODAY.   ROCKEY.
&&

.MARINE...W TO SW WINDS 15 TO 20 KT TODAY...BUT WILL GRADUALLY EASE
TONIGHT AND BECOME MORE W TO NW. SEAS RUNNING 14 TO 16 FT THIS
AM...BUT THESE TOO WILL BE SLOWLY SUBSIDING. LIKELY TO HOLD NEAR 10
TO 11 FT THROUGH MIDWEEK.

ANOTHER QUICKLY MOVING FRONT WILL ARRIVE LATER TUE AND WED...WITH
SOME POTENTIAL FOR BRIEF PERIOD OF WINDS GUSTING 25 KT.
OTHERWISE...SECOND HALF OF THIS WEEK WILL BE MUCH MORE BENIGN.
&&

.PQR WATCHES/WARNINGS/ADVISORIES...
OR...FLOOD WATCH THROUGH MONDAY AFTERNOON FOR ALL OF NW OREGON.
     COASTAL FLOOD ADVISORY FROM 9 AM TO 3 PM FOR THE NORTH
AND CENTRAL OREGON COAST.

WA...FLOOD WATCH THROUGH MONDAY AFTERNOON EXTREME SW WASHINGTON.
     COASTAL FLOOD ADVISORY FROM 9 AM TO 3 PM TO FOR S WA COAST.

PZ...SMALL CRAFT ADVISORY FOR WINDS TODAY ON ALL COASTAL WATERS.
     SMALL CRAFT ADVISORY FOR HAZARDOUS SEAS THROUGH MON
AFTERNOON ON ALL COASTAL WATERS.
     SMALL CRAFT ADVISORY FOR ROUGH COLUMBIA BAR CONDITIONS
THROUGH TONIGHT.

&&

$$

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.



USA.gov is the U.S. government's official web portal to all federal, state and local government web resources and services.