Area Forecast Discussion
Issued by NWS Portland, OR

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FXUS66 KPQR 122117
AFDPQR

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

.SYNOPSIS...A COLD FRONT WILL BRING RAIN TO THE AREA TODAY AND
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...TONIGHT THROUGH MONDAY...PER RADAR AND SATELLITE
IMAGERY...A BAND OF RAIN IS CURRENTLY PUSHING EASTWARD ACROSS THE
WILLAMETTE VALLEY AND CASCADES. RAINFALL AMOUNTS IN THE WILLAMETTE
VALLEY HAVE GENERALLY BEEN BETWEEN A TENTH AND A QUARTER OF AN INCH.
EXPECT THIS BAND OF RAIN TO SLOWLY PUSH EAST OF THE CASCADES THIS
AFTERNOON.

SKIES HAVE CLEARED BEHIND THE FRONT ALONG THE NORTH OREGON AND SOUTH
WASHINGTON COASTS. THIS CLEARING SHOULD SLOWLY WORK ITS WAY INTO THE
WILLAMETTE VALLEY THIS AFTERNOON. THIS SHOULD HELP TO DESTABILIZE THE
LOWER ATMOSPHERE AND PRODUCE AT LEAST ISOLATED TO SCATTERED SHOWERS
DURING THE MID TO LATE AFTERNOON HOURS.

DEEPER SHOWER ACTIVITY IS APPARENT ON SATELLITE IMAGERY OFF THE
OREGON COAST NEAR 130W. THESE SHOWERS HAVE DEVELOPED IN RESPONSE TO
COLDER AIR ALOFT ASSOCIATED WITH THE MAIN UPPER LEVEL SHORTWAVE
TROUGH. THIS SHORTWAVE TROUGH WILL SKIRT OUR NORTHERN ZONES THIS
EVENING AND OVERNIGHT...WHICH SHOULD RESULT IN AN UPTICK IN SHOWER
ACTIVITY FOR OUR NORTHERN COASTAL ZONES AND THE NORTH OREGON AND
SOUTH WASHINGTON CASCADES. SNOW LEVELS WILL ALSO LOWER FROM 4500-5000
FT THIS AFTERNOON INTO THE 3500 FT RANGE OVERNIGHT WITH A COUPLE
INCHES OF SNOW LIKELY IN THE CASCADES.

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...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...SATELLITE IMAGERY SHOWS CLEAR SKIES THIS AFTERNOON BEHIND
A DEPARTING FRONT...AND MANY AREAS HAVE VFR CONDITIONS. THE FRONT
IS STILL OVER THE CASCADES WHERE MVFR CONDITIONS LIKELY DOMINATES
WITH ISOLATED IFR. EXPECT WIDESPREAD VFR CONDITIONS THIS EVENING
AS THE FRONT MOVES EAST OF THE CASCADES. A TROUGH WILL BRING A
ROUND OF SHOWERS AND MVFR CONDITIONS TONIGHT...AND THE COAST AND
LOCALIZED INLAND SITES LIKE KHIO AND KSPB WILL LIKELY HAVE IFR
CONDITIONS BEGINNING AROUND SUNRISE SATURDAY MORNING. SHOWERS WILL
LIFT NORTH SATURDAY AFTERNOON WITH SALEM AND SOUTHWARD IMPROVING
TO VFR.

KPDX AND APPROACHES...MOSTLY VFR CONDITIONS WITH OCCASIONAL RAIN
TONIGHT AND SATURDAY. THERE MAY BE BRIEF MVFR CONDITIONS WITH THE
HEAVIER SHOWERS SATURDAY AFTERNOON. TJ

&&

.MARINE...A LONG PERIOD NW SWELL WILL MAINTAIN 12 TO 14 FT SEAS
THROUGH SATURDAY NIGHT. THE SEAS WILL SUBSIDE TO AROUND 10 FT ON
SUNDAY. A SURFACE TROUGH MOVING THROUGH THE WATERS TONIGHT WILL
INCREASE WINDS A TAD AFTER 10 PM. THE MODELS SUGGEST THAT GUSTS
COULD REACH 25 KT BEYOND 10 NM...MAINLY NORTH OF CASCADE HEAD.
SINCE THE MODELS HAVE BEEN OVER FORECASTING GUSTS AS OF LATE HAVE
DECIDED TO NOT ISSUE A SMALL CRAFT ADVISORY FOR TONIGHT. CAN
EXPECT SOME GUSTS TO NEAR 25 KT BETWEEN 11PM AND 4 AM
TONIGHT...BUT THINK THEY WILL BE INFREQUENT AND LOCALIZED.

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

&&

.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 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 2 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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