Area Forecast Discussion
Issued by NWS Portland, OR

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FXUS66 KPQR 202314
AFDPQR

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE PORTLAND OR
315 PM PST THU NOV 20 2014

.SYNOPSIS...TWO AREAS OF LOW PRES ARE MOVING ONTO THE WEST COAST
TODAY. ONE IS PUSHING ONSHORE ALONG THE BRITISH COLUMBIA
COAST...WHILE THE OTHER LOW IS ALONG THE N CALIFORNIA AND S OREGON
COAST. IN BETWEEN THESE TWO SYSTEMS...WE WILL SEE ONLY SOME LIGHT
SHOWERS LINGERING INTO TONIGHT. A STRONG AND MOIST FRONT WILL BRING
HEAVIER RAIN AND STRONG WINDS LATER TOMORROW INTO EARLY SAT. SNOW
LEVELS WILL LIKELY LOWER BELOW THE CASCADE PASSES BY SATURDAY
MORNING...WITH ACCUMULATING SNOW CONTINUING FOR MUCH OF THE WEEKEND.
A WEAK RIDGE IS EXPECTED TO BUILD OVER THE NE PAC EARLY NEXT
WEEK...BUT MAY NOT BE STRONG ENOUGH TO KEEP CONDITIONS COMPLETELY DRY
OVER THE PAC NW. THE TREND IS THEN TOWARD DRIER WEATHER NEXT WEEK.

&&

.SHORT TERM...TONIGHT THROUGH SUNDAY...
TWO AREAS OF LOW PRES ASSOCIATED WITH A SPLIT UPPER LEVEL TROUGH ARE
MOVING ONSHORE TO THE NORTH AND SOUTH OF US THIS AFTERNOON. THE LOW
TO THE NORTH IS MOVING ONTO THE BRITISH COLUMBIA COAST...WHILE THE
OTHER SITS ALONG THE S OREGON AND N CALIFORNIA COAST AND WILL MOVE
ONSHORE TONIGHT. IN BETWEEN...WE ARE SEEING ONLY SOME LIGHT SHOWERS
OVER SW WASHINGTON AND NW OREGON AS THE HIGHLY STRETCHED UPPER LEVEL
TROF AXIS MOVES OVER THE REGION. ALSO...THE LATEST SURFACE
OBSERVATIONS SHOW THAT TEMPS THROUGH THE COLUMBIA RIVER GORGE AND
UPPER HOOD RIVER VALLEY HAVE WARMED ABOVE FREEZING JUST ABOUT
EVERYWHERE. SO THE THREAT OF FREEZING RAIN APPEARS TO BE OVER FOR
NOW. THE FCST MODELS INDICATE THAT A FEW WEAK SHOWERS WILL LINGER
INTO TONIGHT. BASED ON THE CLEARING SKIES OFFSHORE APPARENT ON
VISIBLE SATELLITE...THINK WE WILL SEE SOME SCATTERING OF THE CLOUD
COVER TONIGHT. THIS SHOULD ALLOW FOR SOME PATCHY FOG AND LOW STRATUS
TO FORM OVERNIGHT. OTHERWISE...EXPECT FAIRLY QUIET CONDITIONS
OVERNIGHT.

A STRONG 150+ KT JET STREAK WILL APPROACH THE PAC NW TOMORROW. THIS
WILL DRIVE A STRONG AND MOIST FRONTAL SYSTEM ONSHORE LATER TOMORROW
AND TOMORROW NIGHT. AMSU SATELLITE DERIVED IMAGERY SHOWS A REGION OF
SUBTROPICAL MOISTURE WELL OFFSHORE THAT WILL FEED INTO THIS SYSTEM.
THE FCST MODELS INDICATE THAT PWAT VALUES WILL BE AROUND 1.25 INCHES
ALONG THE COAST AS THE LEADING WARM FRONT MOVES ONSHORE. WE EXPECT A
BATCH OF HEAVY RAIN TO PUSH INLAND DURING THE LATE AFTERNOON AND
EVENING...WITH 1.5 TO 2 INCHES OF RAIN LIKELY FOR THE COAST...COAST
RANGE AND CASCADES OVER ABOUT A 12 HR PERIOD. THE INTERIOR LOWLANDS
WILL BE LOWER...CLOSER TO AROUND AN INCH. IT DOES NOT APPEAR THAT
RAINFALL TOTALS WILL BE ENOUGH TO CAUSE ANY FLOODING CONCERNS.

THIS SYSTEM WILL ALSO BRING A BURST OF STRONG WINDS ALONG THE COAST
DURING THE AFTERNOON AND EVENING. WILL CONTINUE WITH A HIGH WIND
WATCH FOR THE ENTIRE COAST FOR THE AFTERNOON AND EVENING. A CORE OF
60 KT WINDS AT 925 MB ARE BEING ADVERTISED BY THE 12Z NAM...GFS...AND
ECMWF RUNS. WILL CONFINE THE HIGHEST WINDS TO THE
BEACHES AND COASTAL HEADLANDS...WHERE GUSTS TO 65 MPH ARE CURRENTLY
EXPECTED. THE COASTAL COMMUNITIES SHOULD ALSO BE GUSTY...BUT WILL
LIMIT WIND GUSTS TO 50-55 MPH FOR NOW.

IT IS LOOKING LESS LIKELY THAT FREEZING RAIN IN THE COLUMBIA RIVER
GORGE AND UPPER HOOD RIVER VALLEY WILL BE A CONCERN WITH THIS SYSTEM
BASED ON THE WARMING TEMPS SEEN TODAY. TEMPS SHOULD FALL BACK TO JUST
BELOW FREEZING TONIGHT EAST OF THE CASCADES...AND THE FCST MODELS
CONTINUE TO INDICATE THAT LIGHT EASTERLY FLOW WILL CONTINUE THROUGH
THE INITIAL ONSET OF PRECIP TOMORROW. SO WILL KEEP A SLIGHT CHC OF
FREEZING RAIN AROUND HOOD RIVER AND IN THE HOOD RIVER VALLEY THROUGH
TOMORROW AFTERNOON. DO NOT THINK THERE WILL BE WIDESPREAD
ACCUMULATIONS...BUT SOME PATCHY SPOTS OF ICE ARE DEFINITELY POSSIBLE.
WINDS WILL SWITCH TO WESTERLY DURING THE EVENING...WHICH WILL WARM
THINGS UP CONSIDERABLY AND PUT AN END TO ANY ICE CONCERNS.

THE COLD FRONT WILL MOVE THROUGH THE REGION TOMORROW NIGHT WITH SNOW
LEVELS FALLING RAPIDLY OVERNIGHT INTO SAT MORNING. EXPECT SNOW LEVELS
TO REMAIN BELOW THE CASCADE PASSES THROUGH THE WEEKEND...WITH SHOWERS
CONTINUING IN DECENT OROGRAPHIC FLOW. SNOW WILL BE HEAVIER AT TIMES
AS WEAK IMPULSES MOVE THROUGH ALOFT. AT THIS TIME...IT APPEARS THE
PERIOD OF BEST SNOWFALL ACCUMULATION WILL BE OVERNIGHT SAT INTO EARLY
SUN. THIS PERIOD MAY END UP NEEDING A WINTER WEATHER ADVISORY AS WE
GET CLOSER IN TIME. PYLE


.LONG TERM...SUNDAY NIGHT THROUGH THURSDAY. THE MORE WESTERLY OR
ZONAL FLOW THAT SETS UP OVER THE WEEKEND DURING THE LATTER PART OF
THE SHORT TERM PERIOD BEGINS TO BUCKLE A BIT IN THE EARLY PART OF
THE LONG TERM PERIOD WITH SOME FLAT RIDGING DEVELOPING OVER THE
NORTHEAST PACIFIC. HAVE DECIDED TO CONTINUE TO STICK MORE WITH A
DIRTY RIDGE SCENARIO OF THE ECMWF VS THE HIGHER AMPLITUDE RIDGING OF
THE OPERATIONAL GFS MODEL. CONFIDENCE DECREASES THROUGHOUT THE LONG
TERM PERIOD AS MODEL VARIABILITY INCREASES...THOUGH THE TREND IS
TOWARD DRIER DURING THE MIDDLE TO LATTER PARTS OF NEXT WEEK. TOLLESON
&&

.AVIATION...MAINLY VFR CIGS THIS AFTERNOON...EXCEPT NEAR SALEM IN
CENTRAL WILLAMETTE VALLEY IS LIKELY TO KEEP LOW MVFR THROUGH THIS
EVENING. MVFR AND IFR LIKELY TO RETURN TONIGHT ACROSS THE AREA.
KTTD STILL GUSTING TO 25 KTS...KEEPING VFR CONDITIONS OVER KTTD.
THESE WINDS SHOULD WEAKEN TO 10 KT AFTER 06Z TONIGHT...BUT WEAK
AND DRY EASTERLIES MAY INHIBIT MVFR OR IFR.

SHOWERS MOVE THROUGH THE REGION AHEAD OF OUR NEXT COLD FRONT FRIDAY.
THIS WILL BRING SHOWERS AND OCCASIONAL MVFR ACROSS THE AREA EARLY
FRIDAY. WINDS INCREASE ACROSS THE AREA AROUND 18Z FRIDAY FROM THE
SOUTH. COLD FRONT LOOKS TO MOVE THROUGH LATE FRIDAY.


KPDX AND APPROACHES...MAINLY VFR THIS EVENING...DROPPING TO MVFR
AROUND 08Z TONIGHT. MVFR SHOULD PERSIST THROUGH FRIDAY
MORNING WITH SCATTERED SHOWERS...BEFORE LIFTING AROUND 18Z AS
WIND INCREASES FROM THE SOUTH.

&&

.MARINE...15 TO 20 KT WINDS WITH GUSTS NEAR 25 KTS TONIGHT WILL
INCREASE TO 20 TO 25 KT WITH GUSTS TO 30 BY FRIDAY MORNING. WINDS
CONTINUE TO INCREASE THROUGH THE DAY FRIDAY AHEAD OF A STRONG COLD
FRONT. WINDS INCREASE TO 35 TO 40 KTS FRIDAY AFTERNOON...WITH
GUSTS TO 50 KTS...MAINLY IN THE INNER WATERS. WINDS SUBSIDE TO 20
TO 25 KTS BEHIND THE FRONT LATE FRIDAY.

SEAS ARE BETWEEN 8 TO 10 FT RIGHT NOW...BUT WILL BUILD OVERNIGHT
TONIGHT
TO 10 TO 12 FT. SEAS CONTINUE TO RISE DURING THE DAY ON FRIDAY
AHEAD OF OUR NEXT COLD FRONT...BUILDING TO AROUND 20 FT FRIDAY
AFTERNOON. SEA SEAS DROP FAIRLY QUICKLY BEHIND THE COLD FRONT AS
WINDS WEAKEN...BUT SEAS LOOK TO REMAIN ABOVE 10 FT THROUGH THIS
WEEKEND.

-MCCOY

&&

.PQR WATCHES/WARNINGS/ADVISORIES...
OR...HIGH WIND WATCH FROM FRIDAY MORNING THROUGH FRIDAY EVENING FOR
     CENTRAL OREGON COAST-NORTH OREGON COAST.

WA...HIGH WIND WATCH FROM FRIDAY MORNING THROUGH FRIDAY EVENING FOR
     SOUTH WASHINGTON COAST.

PZ...SMALL CRAFT ADVISORY FOR WINDS UNTIL 4 AM PST FRIDAY FOR
    COASTAL WATERS FROM CAPE SHOALWATER WA TO FLORENCE OR OUT 60 NM.

     GALE WARNING FROM 10 AM TO 10 PM PST FRIDAY FOR COASTAL WATERS
    FROM CAPE SHOALWATER WA TO FLORENCE OR OUT 60 NM.

     SMALL CRAFT ADVISORY FOR HAZARDOUS SEAS UNTIL 3 PM PST THIS
     AFTERNOON FOR COASTAL WATERS FROM CAPE SHOALWATER WA TO
    FLORENCE OR OUT 60 NM.

     SMALL CRAFT ADVISORY FOR ROUGH COLUMBIA RIVER BAR UNTIL 6 PM
    PST THIS EVENING.

&&

$$

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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