Area Forecast Discussion
Issued by NWS Portland, OR

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FXUS66 KPQR 020411
AFDPQR

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE PORTLAND
910 PM PDT WED APR  1 2015

.SYNOPSIS...DRIER WEATHER ON THURSDAY WILL BE SHORT LIVED AS A QUICK
MOVING COLD FRONT BRINGS ANOTHER SHOT OF VALLEY RAIN AND MOUNTAIN
SNOW TO THE AREA ON FRIDAY. SATURDAY APPEARS IT WILL REMAIN GENERALLY
DRY...BUT COOL. HOWEVER...A COLDER AND MORE UNSTABLE AIRMASS WILL
BRING SHOWERS TO THE REGION ON SUNDAY. THIS SHOWERY PATTERN WILL
LIKELY CONTINUE THROUGH AT LEAST TUESDAY.

&&

.UPDATE...DOPPLER RADAR INDICATES SHOWERS ARE BEGINNING TO WEAKEN
THIS EVENING AS SURFACE BASED INSTABILITY WANES. FURTHERMORE...A VORT
MAX ON THE BACKSIDE OF THE UPPER LEVEL TROUGH RESPONSIBLE FOR THE
UNSTABLE AIR ALOFT IS BEGINNING TO PUSH EAST OF THE REGION AND WILL
ACT TO STABLIZE THE ATMOSPHERE FROM THE TOP DOWN OVERNIGHT AS WELL.
NONETHELESS...THERE MAY STILL BE A FEW SHOWERS LINGERING ALONG THE
COAST AND IN THE CASCADES THURSDAY MORNING...BUT MOST LOCATIONS
SHOULD REMAIN DRY ON THURSDAY. SOME WEAK INSTABILITY MAY LEAD SOME
WEAK SHOWERS BUBBLING UP OVER THE NORTH OREGON COAST RANGE THURSDAY
AFTERNOON...WHICH COULD DRIFT EASTWARD INTO WASHINGTON COUNTY AND THE
LOWER COLUMBIA RIVER VALLEY...BUT EXPECT THIS TO BE MORE THE
EXCEPTION THAN THE RULE.

OTHERWISE...A QUICK HITTING COLD FRONT WILL LIKELY BRING ANOTHER
SOLID SHOT OF RAIN AND CASCADE SNOW ON FRIDAY. THE QUICK MOVING
NATURE SHOULD LIMIT QPF THOUGH. THE UPPER LEVEL TROUGH AND COLD
UNSTABLE AIR ALOFT RESPONSIBLE FOR SENDING THIS FRONT INTO THE REGION
WILL BE SLOW TO ARRIVE HOWEVER. THIS MAY RESULT IN SATURDAY ENDING UP
MUCH MORE DRY THAN WET ACROSS THE AREA WITH BEST CHANCE OF A SHOWER
NEAR THE COAST OR COAST RANGE IN THE AFTERNOON. DID NOT ADJUST THIS
PART OF THE FORECAST SO MID SHIFT COULD INGEST ONE MORE SET OF MODEL
RUNS BEFORE DECREASING POPS. ANY BREAK IN THE WET WEATHER ON SATURDAY
WILL LIKELY BE SHORT LIVED AS COLDER AND MORE UNSTABLE AIR FINALLY
ARRIVE ON SUNDAY...LIKELY RESULTING IN SCATTERED SHOWERS AND PERHAPS
A FEW THUNDERSTORMS ACROSS THE AREA...ESPECIALLY DURING THE AFTERNOON
AND EVENING HOURS. /NEUMAN



.LONG TERM...SATURDAY NIGHT THROUGH WEDNESDAY...COOL AND UNSETTLED
WEATHER CONTINUES LATE THIS WEEKEND AS AN UPPER LEVEL TROUGH DIGS
SOUTH INTO THE PACIFIC NORTHWEST. BOTH THE 12Z GFS AND ECMWF BOTH
AGREE LOW PRESSURE SETTLES JUST OFF THE WASHINGTON/OREGON COASTLINE
BY SUNDAY...BRINGING A THREAT FOR AFTERNOON/EVENING THUNDERSTORMS.
AFTER THAT MODEL SOLUTIONS DIVERGE. EITHER WAY...SHOWERS...CASCADE
SNOW SHOWERS AND COOLER TEMPERATURES CONTINUE INTO MONDAY AND TUESDAY
AS THE OVERALL PATTERN IS FOR THE UPPER TROUGH TO DIG FURTHER SOUTH
INTO NORTHERN CALIFORNIA THEN MOVE INLAND BY TUESDAY NIGHT. WE SHOULD
SEE A BRIEF BREAK AS WEAK UPPER LEVEL RIDGING DEVELOPS BY NEXT
WEDNESDAY...WITH TEMPERATURES SLOWLY REBOUNDING BY MIDWEEK. /27
&&

.AVIATION...ISOLATED SHOWERS WILL CONTINUE TO IMPACT THE REGION
OVERNIGHT. EXPECT MOSTLY VFR CONDITIONS WITH BRIEF PERIODS OF
REDUCED FLIGHT RULES UNDER STRONGER SHOWERS. GUIDANCE CONTINUES
TO INDICATE AN MVFR DECK DEVELOPING AROUND 12Z. THIS SHOULD
RAPIDLY IMPROVE TO VFR BY LATE MORNING AS HIGH PRESSURE BUILDS
BRIEFLY OVER THE REGION. RAIN RETURNS LATE THURSDAY NIGHT WITH AN
APPROACHING FRONT.

KPDX AND APPROACHES...ISOLATED SHOWERS TO CONTINUE OVERNIGHT UNDER
MAINLY VFR CONDITIONS. GUIDANCE SHOWS A MVFR DECK DEVELOPING
AROUND 12Z THAT SHOULD BURN OFF BY 18Z ALLOWING CONDITIONS TO
RETURN TO VFR. /64

&&

.MARINE...LINGERING INSTABILITY WILL CONTINUE TO PRODUCE SHOWERS
OVER THE WATERS TONIGHT. HIGH PRESSURE BUILDING OVER THE
NORTHEAST PACIFIC SHOULD BRING A BRIEF BREAK IN THE WEATHER FOR
MUCH OF TOMORROW. EXPECT WINDS LESS THAN 20 KT AND SEAS AROUND 8
FT. A WEAKENING FRONT WILL MOVE ACROSS THE WATERS LATE TOMORROW
NIGHT AND INTO FRIDAY. DESPITE THE MODELS SHOWING THE FRONT
WEAKENING AS IT MOVES ONSHORE WE CAN EXPECT TO SEE SMALL CRAFT
ADVISORY WIND GUSTS OVER THE NORTHERN OUTER WATERS FROM LATE
THURSDAY NIGHT INTO FRIDAY MORNING. THE PROGRESSIVE WEATHER
PATTERN RETURNS OVER THE WEEKEND AS AN UPPER LEVEL LOW DROPS SOUTH
FROM THE GULF OF ALASKA. DETAILS REMAIN UNCERTAIN AT THE MOMENT
AND WILL BE REVISITED WITH FUTURE UPDATES. /64

&&

.PQR WATCHES/WARNINGS/ADVISORIES...
OR...NONE.
WA...NONE.
PZ...SMALL CRAFT ADVISORY FOR WINDS FROM 1 AM TO 11 AM PDT FRIDAY
     FOR WATERS FROM CAPE SHOALWATER WA TO CASCADE HEAD OR FROM
     10 TO 60 NM.

     SMALL CRAFT ADVISORY FOR ROUGH COLUMBIA RIVER BAR FROM 3 AM
     TO 7 AM PDT THURSDAY.

&&


$$

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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