Area Forecast Discussion
Issued by NWS Portland, OR

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FXUS66 KPQR 130501
AFDPQR

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE PORTLAND OR
900 PM PST FRI FEB 12 2016

.SYNOPSIS...COOLER AIR SPILLING IN BEHIND A COLD FRONT WILL
EVENTUALLY ALLOW SNOW LEVELS TO LOWER BELOW CASCADE PASSES TONIGHT
AND SATURDAY. A STRONG WARM FRONT WILL THEN SPREAD STEADY RAIN INTO
NORTHWEST OREGON AND SOUTHWEST WASHINGTON SATURDAY AFTERNOON AND
EVENING WITH A PERIOD OF HEAVY SNOW FOR THE CASCADES. HOWEVER...SNOW
LEVELS WILL RISE TO WELL ABOVE THE CASCADE PASSES AS PERIODS OF
LIGHTER RAIN FALL ON SUNDAY. ADDITIONAL UNSETTLED WEATHER WILL
PRODUCE MORE VALLEY RAIN AND MOUNTAIN SNOW NEXT WEEK.

&&

.SHORT TERM...BY LATE EVENING COLD FRONT HAD PUSHED E ACROSS THE
CASCADES. STILL SOME SHOWERS SHOWING UP ON RADAR...MAINLY
OROGRAPHICALLY DRIVEN ON THE CASCADES...THE N COAST RANGE AND
WILLAPA HILLS. THE MAIN SHORTWAVE WAVE TROUGH AXIS WAS STILL JUS OFF
THE WA AND N OREGON COAST...ADDING SOME DYNAMIC LIFT TONIGHT AS IT
MOVES ACROSS MAINLY THE N PART OF THE FORECAST AREA...SO WILL NEED
TO KEEP SOME MENTION OF SHOWERS OVERNIGHT IN THE N INTERIOR IN
ADDITION TO COAST AND MOUNTAIN LOCATIONS.

REMAINDER OF SHORT TERM DISCUSSION UNCHANGED...A STRONG WARM FRONT
WILL SPREAD INTO THE REGION LATE SATURDAY AFTERNOON AND PRODUCE AN
EXTENDED PERIOD OF WET WEATHER SATURDAY NIGHT AND SUNDAY. RAINFALL
AMOUNTS OF AT LEAST 1 TO 3 INCHES APPEAR LIKELY IN THE COAST RANGE
AND CASCADES WITH A QUARTER TO ONE INCH OF RAIN IN THE LOWER
COLUMBIA RIVER AND WILLAMETTE VALLEYS. THE HIGHEST RAINFALL AMOUNTS
SHOULD BE FOCUSED OVER OUR MORE NORTHERN ZONES. SNOW LEVELS WILL
LIKELY START OFF AROUND 4000 FT SATURDAY AFTERNOON AND
EVENING...PARTICULARLY ACROSS THE SOUTH WASHINGTON CASCADES AND NEAR
MOUNT HOOD BEFORE RISING ABRUPTLY TO 7000 FT OR MORE FOR SUNDAY.
NONETHELESS...4 TO 8 INCHES OF SNOW APPEAR LIKELY...AND PERHAPS EVEN
MORE IN THE SOUTH WASHINGTON CASCADES...BEFORE THE SNOW TURNS TO
RAIN.

THIS WEEKENDS RAIN SHOULD COME IN TWO DISTINCT SURGES. THE FIRST WILL
ARRIVE LATE SATURDAY AFTERNOON/EARLY EVENING AND WILL LIKELY BE THE
STRONGEST AS 50 KT WESTERLY 850MB WINDS ENHANCE IVT VALUES TO
SOMETHING WE TYPICALLY SEE ABOUT ONCE A YEAR TO ONCE EVERY OTHER YEAR
IN FEBRUARY. THIS SURGE OF RAIN SHOULD RESULT IN MANY OF OUR FASTER
RESPONDING RIVERS TO RISE RAPIDLY...PARTICULARLY THE GRAYS
RIVER...BUT MAIN STEM RIVER FLOODING IS NOT ANTICIPATED. A SECONDARY
SURGE OF RAIN SHOULD ARRIVE SUNDAY MORNING AS A WEAKER WARM FRONT
PUSHES NORTHEASTWARD ACROSS THE REGION. AS ISENTROPIC LIFT WEAKENS
AND WESTERLY 850MB STRENGTHENS MIDDAY SUNDAY...EXPECT PRECIPITATION
TO LIGHTEN...IF NOT STOP...IN THE WILLAMETTE VALLEY AS A COAST RANGE
RAIN SHADOW DEVELOPS.

SHORTWAVE RIDGING SHOULD THEN SLOWLY PUSH INTO THE REGION SUNDAY
NIGHT AND MONDAY SO EXPECT A GENERAL DRYING TREND FROM SOUTHWEST TO
NORTHEAST DURING THIS PERIOD WITH MILD TEMPERATURES...IE HIGH
TEMPERATURES FLIRTING WITH 60F...RETURNING MONDAY. /NEUMAN

.LONG TERM...NO CHANGES. PREVIOUS DISCUSSION FOLLOWS. MONDAY NIGHT
THROUGH FRIDAY...SHORTWAVE RIDGING EARLY IN THE WEEK WILL ONCE AGAIN
GIVE WAY TO A MORE ACTIVE WEATHER PATTERN DURING THE MIDDLE TO
LATTER HALF OF NEXT WEEK. THE REMNANTS OF AN ATMOSPHERIC RIVER EVENT
MAY DIP FAR ENOUGH SOUTH TO BRING SOME LIGHT RAIN TO THE REGION
TUESDAY...BUT CONFIDENCE IS LOW. MODELS HAVE BEEN IN MUCH BETTER
AGREEMENT THAT A SHORTWAVE TROUGH WILL SWING INTO THE WESTERN UNITED
STATES AND BRING WET AND COOLER WEATHER WEDNESDAY INTO THURSDAY. AN
ADDITIONAL STORM SYSTEM APPEARS POSSIBLE TOWARDS THE END OF NEXT
WEEK. TEMPERATURES FOR THE MOST PART SHOULD REMAIN NEAR TO ABOVE
NORMAL WITH ANY BOUTS OF PRECIPITATION LOOKING TO REMAIN LIGHT
ENOUGH THAT WE DO NOT FORESEE ANY MAJOR HYDROLOGIC ISSUES IN THE
NEXT WEEK. AB/NEUMAN

&&

.AVIATION...UPPER LEVEL LOW PRES MOVING ONSHORE WILL BRING A ROUND
OF SHOWERS OVERNIGHT INTO SAT AM...MAINLY FOR THE COAST AND
HIGHER TERRAIN. EXPECT A MIX OF VFR AND MVFR CIGS AT THE COAST. RAIN
SHADOWING MAY KEEP THE VALLEY MOSTLY DRY WITH VFR CONDITIONS FOR
MUCH OF THE NIGHT. THEN EXPECT SOME MVFR CIGS TO DEVELOP EARLY SAT
AM...BETWEEN 12Z AND 15Z. EXPECT CONDITIONS TO IMPROVE TO VFR FOR
THE LATE MORNING AND AFTERNOON INLAND FROM ROUGHLY KSLE SOUTHWARD.
ELSEWHERE...MVFR MAY LINGER THROUGH THE DAY. EXPECT CONDITIONS TO
DETERIORATE FURTHER WITH INCREASING RAIN FROM NW TO SE SAT
AFTERNOON AND EVENING AS A WARM FRONT APPROACHES.

KPDX AND APPROACHES...MOSTLY VFR WITH THE POTENTIAL FOR A PASSING
SHOWER OVERNIGHT. EXPECT MVFR CIGS TO DEVELOP BY AROUND 12Z TO 15Z
SAT...WITH MVFR POTENTIALLY LINGERING THROUGH THE DAY. CIGS LOWER
FURTHER AND RAIN INCREASES SAT AFTERNOON AND EVENING. PYLE

&&

.MARINE...A LONG PERIOD NW SWELL WILL MAINTAIN 11 TO 13 FT SEAS
THROUGH SATURDAY NIGHT. THE SEAS WILL SUBSIDE TO AROUND 10 FT ON
SUNDAY. A SURFACE TROUGH MOVING THROUGH THE WATERS WILL INCREASE
WINDS A BIT OVERNIGHT. THE MODELS SUGGEST THAT GUSTS COULD REACH
25 KT BEYOND 10 NM...MAINLY NORTH OF CASCADE HEAD. HAVE DECIDED TO
ISSUE A SHORT SMALL CRAFT ADVISORY FOR WINDS FOR THE NORTHERN
OUTER WATERS.

WINDS WILL COME UP FURTHER WITH THE NEXT SYSTEM WITH AT LEAST
SMALL CRAFT WINDS SATURDAY AFTERNOON THROUGH LATE SATURDAY NIGHT.
GALE FORCE GUSTS ARE POSSIBLE...AND A GALE WATCH IS IN EFFECT FOR
THIS TIME PERIOD. THERE IS GREATER FORECAST CONFIDENCE FOR GALES
NORTH OF CASCADE HEAD. TJ/PYLE

&&

.PQR WATCHES/WARNINGS/ADVISORIES...
OR...NONE.
WA...NONE.
PZ...GALE WATCH FROM SATURDAY AFTERNOON THROUGH SATURDAY EVENING FOR
     COASTAL WATERS FROM CAPE SHOALWATER WA TO FLORENCE OR OUT 60 NM.

     SMALL CRAFT ADVISORY FOR WINDS UNTIL 4 AM PST SATURDAY FOR
     WATERS FROM CAPE SHOALWATER WA TO CASCADE HEAD OR FROM 10
     TO 60 NM.

     SMALL CRAFT ADVISORY FOR HAZARDOUS SEAS UNTIL 2 PM PST SATURDAY
     FOR COASTAL WATERS FROM CAPE SHOALWATER WA TO FLORENCE OR OUT 60 NM.

     SMALL CRAFT ADVISORY FOR ROUGH COLUMBIA RIVER BAR UNTIL 10 PM PST SATURDAY.

&&


$$

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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