Area Forecast Discussion
Issued by NWS Portland, OR

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FXUS66 KPQR 012155
AFDPQR

AREA FORECAST DISCUSSION...UPDATED
NATIONAL WEATHER SERVICE PORTLAND OR
155 PM PST SUN FEB  1 2015

.SYNOPSIS..SHOWERS WILL LINGER..MAINLY OVER THE CASCADES EARLY THIS
EVENING IN THE WAKE OF A WEAK COLD FRONT. A SERIES OF FRONTS WILL
BRING PERIODS OF RAIN AND HIGH MOUNTAIN SNOW MONDAY...TUESDAY...AND
WEDNESDAY. AN ATMOSPHERIC RIVER PATTERN LOOKS TO SET UP LATE IN THE
WEEK AND THERE IS POTENTIALLY FOR MUCH HIGHER RAINFALL ANOTHER SERIES
OF FRONTS THURSDAY THROUGH NEXT WEEKEND.
&&

.SHORT TERM...TONIGHT THROUGH TUESDAY NIGHT...THE COLD FRONT HAS
MOVED QUICKLY ACROSS NW OREGON AND SW WASHINGTON TODAY. RADAR IMAGERY
SHOWS SHOWERS ARE LINGERING OVER THE CASCADES THIS AFTERNOON...BUT
THINK THE EARLY EVENING WILL BE MOSTLY DRY. THE COAST RANGE AND
CASCADES MEASURED BETWEEN 0.25 AND 0.5 INCH OF RAIN SINCE EARLY THIS
MORNING...AND THE WILLAMETTE VALLEY AROUND 0.25 INCH.

LOWERING SURFACE TEMPERATURES INDICATE THAT SNOW LEVELS ARE BEGINNING
TO LOWER. EXPECT THE SNOW LEVELS TO BE AROUND 5500 FEET...BUT THE
AVAILABLE HIGHER ELEVATION WEB CAMS ARE NOT SHOWING ANY SNOW YET...SO
MY ESTIMATION MAY BE A COUPLE HUNDRED FEET TO HIGH. EXPECT THE SNOW
LEVELS TO LOWER TO AROUND 4500 FEET FOR THE SW WASHINGTON AND
NORTHERN OREGON CASCADES TONIGHT. THE RAIN WILL BE ENDING AS THIS
COOLER AIR MOVES IN...BUT IT MAY NOT RISE MUCH BEFORE THE NEXT SYSTEM
MOVES IN MONDAY MORNING.

WATER VAPOR IMAGERY SHOWS A BROAD UPPER LOW OVER THE NE PACIFIC WITH
A LOT OF SHORTWAVE TROUGH ROTATING AROUND IT. WATER VAPOR ALSO SHOWS A
STREAM OF MOISTURE FROM THE PACIFIC NW TO WEST OF HAWAII. THE
SHORTWAVES WILL CONTINUE TO FEED THIS MOISTURE TO OUR AREA...WITH A
SERIES OF SYSTEMS BRINGING PRECIPITATION.

THE NEXT FRONT IS CURRENTLY DEVELOPING OFFSHORE AND WILL BRING
ANOTHER ROUND OF RAIN AND POSSIBLY SOME MOUNTAIN SNOW TO THE AREA
MONDAY. THIS FRONT HAS A LITTLE MORE OOMPH TO IT THAN TODAYS...AND
EXPECT 0.75 TO 1 INCH OF RAIN FOR THE COAST RANGE AND THE CASCADES
MONDAY WITH 0.4 TO 0.75 INCHES FOR THE LOW LANDS. AREAS SOUTH OF
SALEM ARE MORE LIKELY TO HAVE HIGHER TOTALS THAN NORTHERN LOCATIONS.
THE SNOW LEVELS FOR THE WASHINGTON CASCADES MAY NOT RISE MUCH BEFORE
THE PRECIPITATION MOVES IN...AND AREAS AROUND 4500 TO 5000 FEET MAY
SEE 2 TO 6 INCHES OF NEW SNOW. IF THE AREA OF HIGHER MOISTURE SHIFTS
NORTHWARD THERE MAY EVEN BE HIGHER TOTALS THAN THAT...BUT THIS SEEMS
UNLIKELY FOR NOW.

THIS FRONT WILL ALSO MOVE RATHER QUICKLY WITH JUST SHOWERS REMAINING
FOR THE CASCADES LATE MONDAY AFTERNOON. SNOW LEVELS WILL AGAIN LOWER
BEHIND THIS FRONT BACK DOWN TO 4500 FEET FOR THE SW WASHINGTON AND
THE NORTHERN OREGON CASCADES. THESE SNOW LEVELS WILL REMAIN
RELATIVELY LOW AS THIS SYSTEM MOVES ACROSS THE AREA...BUT THE
PRECIPITATION TO THE NORTH WILL NOT BE VERY IMPRESSIVE AND DO NOT
ANTICIPATE SNOW IMPACTS. THE SNOW LEVELS TO THE SOUTH...OVER THE
CENTRAL OREGON CASCADES WILL REMAIN ABOVE 5500 FEET.  FOR THE CENTRAL
OREGON CASCADES. THERE WILL LIKELY BE A BRIEF DRY PERIOD MONDAY NIGHT
BEFORE ANOTHER SOUTHERLY FOCUSED RAIN SURGE ARRIVES TUESDAY MORNING.
PRECIPITATION WILL AGAIN TAPER OFF TUESDAY EVENING. TJ

LONG TERM...WEDNESDAY THROUGH SATURDAY NIGHT...MODELS ARE IN BETTER
AGREEMENT FOR WEDNESDAY AND FORECAST AN UPPER RIDGE AMPLIFYING OVER
THE AREA AS A DEEPER SHORTWAVE TROUGH APPROACHES THE COAST. THERE
APPEARS THAT A WEAK WARM FRONT WILL SLIDE OVER THE AREA FOR LIGHT
RAIN DESPITE THE BUILDING RIDGE. THEN A  PERIOD OF MUCH WETTER
WEATHER IS EXPECTED THURSDAY THROUGH NEXT WEEKEND AS A SWATH OF
SUBTROPICAL MOISTURE COMBINED WITH A SERIES OF ATMOSPHERIC WAVES SETS
UP OVER THE NE PACIFIC. THIS WEATHER PATTERN WILL LIKELY BRING A
SUBSTANTIAL AMOUNT OF RAIN TO PARTS OF THE PACIFIC NORTHWEST.
HOWEVER...CONFIDENCE IN TIMING AND AREAS OF PRIMARY QPF FOCUS REMAIN
RATHER LOW AT THIS TIME. CURRENT MODELS SHOW THAT THE REALLY HIGH
RAINFALL TOTALS WILL SET UP OVER NORTHERN CALIFORNIA...BUT THEY DO
NOT ALWAYS FORECAST THESE SITUATIONS VERY WELL...AND WE WILL MONITOR
THIS SITUATION CLOSELY FOR THE POTENTIAL OF FLOODING IN THE PORTLAND
FORECAST AREA. TJ
&&

.AVIATION...CIGS HAVE LOWERED BEHIND THE COLD FRONT PASSAGE THIS
AFTERNOON WITH PREDOMINANTLY MVFR AND IFR CIGS AROUND 500-1500 FT.
EXPECT OCCASIONAL SHOWERS THROUGH 06Z-08Z TONIGHT BEFORE RAIN
INCREASES AGAIN WITH ANOTHER FRONTAL SYSTEM. EXPECT POSSIBLE SPOTS
OF IFR/LIFR FOG OR LOW STRATUS OVERNIGHT...ESPECIALLY IN THE
SOUTH WILLAMETTE VALLEY...BEFORE LIGHT RAIN SPREADS INLAND AFTER
14Z MON. EAST WINDS THROUGH THE GORGE WILL DIMINISH BY THIS
EVENING.

KPDX AND APPROACHES...MVFR AND IFR CIGS BETWEEN 500-1500 FT WILL
PERSIST THIS EVENING. COULD SEE CIGS LOWER BELOW 500 FT IN FOG/LOW
STRATUS OVERNIGHT FROM 06Z-12Z. GUSTY EAST WINDS NEAR KTTD WILL
DIMINISH BY 02Z-05Z. RAIN SPREADS INLAND AFTER 14Z MON. /27
&&

.MARINE...SOUTH WINDS HAVE BACKED TO THE SOUTHWEST-WEST BEHIND THE
COLD FRONT THIS AFTERNOON...WITH SEAS HOLDING BETWEEN 5-6 FT.
EXPECT QUIETER CONDITIONS THROUGH LATE THIS EVENING BEFORE THE
SECOND...STRONGER SYSTEM APPROACHES THE COASTAL WATERS LATE
TONIGHT/EARLY MONDAY MORNING. WILL SEE SEAS INCREASING TO 10-11 FT
MONDAY...ALONG WITH SOUTHWEST WINDS WITH GUSTS 25-30 KT LIKELY.
THE STRONGEST WINDS WILL OCCUR MIDDAY MONDAY. HAVE ISSUED SMALL
CRAFT ADVISORIES FOR BOTH WINDS AND SEAS FOR THE MONDAY SYSTEM.

WINDS AND SEAS START TO SUBSIDE LATE MONDAY...BRINGING SEAS BACK
DOWN TO AROUND 7 TO 8 FT BY MIDWEEK AS SHORT-LIVED HIGH PRESSURE
BUILDS BACK OVER THE REGION. MODELS ARE IN AGREEMENT THAT AN EVEN
STRONGER SYSTEM WILL MOVE THROUGH LATE THIS WEEK...WHICH COULD
GENERATE SOUTHERLY GALES AND BRING SEAS UP TO NEAR 20 FT THURSDAY
OR FRIDAY. THERE IS UNCERTAINTY IN THE TIMING AND TRACK OF THIS
SYSTEM...WHICH SHOULD GET IRONED OUT AS THE WEEK PROGRESSES.
-MCCOY/27
&&

.PQR WATCHES/WARNINGS/ADVISORIES...
OR...NONE.
WA...NONE.
PZ...SMALL CRAFT ADVISORY FOR WINDS UNTIL 4 PM PST THIS AFTERNOON
     FOR COASTAL WATERS FROM CAPE SHOALWATER TO CASCADE HEAD OUT
     60 NM.

     SMALL CRAFT ADVISORY FOR WINDS FROM 1 AM TO 4 PM PST MONDAY FOR
     COASTAL WATERS FROM CAPE SHOALWATER TO FLORENCE OUT 60 NM.

     SMALL CRAFT ADVISORY FOR HAZARDOUS SEAS FROM 1 AM TO 4 PM PST
     MONDAY FOR COASTAL WATERS FROM CAPE SHOALWATER TO FLORENCE
     OUT 60 NM.

     SMALL CRAFT ADVISORY FOR ROUGH COLUMBIA RIVER BAR FROM 1 AM
     TO 6 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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