Area Forecast Discussion
Issued by NWS Portland, OR

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FXUS66 KPQR 180344
AFDPQR

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE PORTLAND
844 PM PDT FRI APR 17 2015

.SYNOPSIS...WARM DAYS AND PLEASANT NIGHTS WILL CONTINUE FOR THE NEXT
FEW DAYS AS HIGH PRESSURE DOMINATES THE PACIFIC NORTHWEST. REMNANTS
OF A WEAK COLD FRONT WILL SLIDE SOUTH OF THE AREA TONIGHT LEAVING
SOME LOW CLOUDS OVER THE COAST AND LOCALLY INLAND THROUGH EARLY
SATURDAY. THIS WILL BE FOLLOWED BY MORE HIGH PRESSURE AND AN EVEN
WARMER AIR MASS...POTENTIALLY BRINGING THE WARMEST DAYS SO FAR THIS
YEAR SUNDAY AND MONDAY AS INLAND TEMPERATURES EXCEED 80 DEGREES. THE
EARLIEST CHANCE OF RAIN APPEARS TO BE TUESDAY AS HIGH PRESSURE
WEAKENS AND A COOLER UPPER TROUGH MOVES IN FOR THE MIDDLE OF NEXT
WEEK.

&&

.UPDATE...QUIET NIGHT ACROSS THE DISTRICT WITH ONLY WEAK REMNANTS OF
THE FRONT LEAVING A BIT OF STRATUS AFFECTING THE CENTRAL COAST. WILL
PROBABLY SEE SOME RADIATION FOG/STRATUS DEVELOP OVER THE COASTAL
VALLEYS TONIGHT AND LAST THROUGH THE EARLY MORNING. TEMPERATURES
TODAY OVERACHIEVED THE FORECAST BY A FEW DEGREES NEARLY ACROSS THE
BOARD. AS SUCH...HAVE TAKEN THE CURRENTLY FORECASTED DAY TO DAY
TEMPERATURE TRENDS AND APPLIED THEM TO TODAYS OBSERVED VALUES. HAVE
CONFIDENCE IN THIS METHOD GIVEN FLOW TURNS SLIGHTLY OFFSHORE THROUGH
THE WEEKEND. THE RESULT IS AN EXPECTATION OF TEMPERATURES AROUND 80
A DAY EARLIER ON SUNDAY INSTEAD OF ON MONDAY. MONDAY MAY REACH IN TO
THE LOWER 80S BUT STILL AM NOT SURE ABOUT THE MOVEMENT TIMING OF THE
EXPECTED THERMAL TROUGH OVER THE AREA. IF IT SLIDES OVER THE
CASCADES BY MONDAY AFTERNOON THEN EXPECT A MINOR MARINE PUSH TO KEEP
MONDAYS HIGHS STAYING CLOSE TO SUNDAY EXCEPT ALONG THE COAST. IF IT
MOVES SLOWER THEN MODELS INDICATE...COMMONLY SEEN...THEN MONDAY
COULD BE THE WARMEST DAY WITH WIDESPREAD INLAND TEMPS IN THE LOWER
80S. DECIDED ON A BLEND BETWEEN THE TWO SCENARIOS AS A HEDGE FOR
NOW. WILL BE SHIPPING THE UPDATED PACKAGE SHORTLY. /JBONK

&&

.AVIATION...WIDESPREAD VFR CONDITIONS WILL CONTINUE THROUGH SAT. LOW
END MVFR CIGS ALONG PARTS OF THE COAST FRI EVENING WILL BECOME LESS
LIKELY TO CONTINUE OVERNIGHT. EXPECT ABOUT A 20 PERCENT CHANCE OF
LOW MVFR CIGS TO REFORM OVERNIGHT...BUT AS WINDS TURN OFFSHORE EARLY
SAT MORNING ANY THREAT OF MVFR CIGS COMES TO END AFTER 14Z.

KPDX AND APPROACHES...VFR CONDITIONS WILL PERSIST OVER THE NEXT 24
HOURS. A FEW CLOUDS BETWEEN 2K AND 3K FT MAY FORM BETWEEN 11Z AND
16Z...BUT THE CHANCES FOR A CIG TO FORM ARE LESS THAN 10 PERCENT.
&&

.MARINE...GUSTY N WINDS ARE EXPECTED TO CONTINUE THROUGH THE WEEKEND
AND INTO MON AS HIGH PRES REMAINS OFFSHORE WITH A TROUGH OF LOW PRES
ALONG THE S OREGON COAST. THE WINDS WILL BE STRONGEST DURING THE
LATE AFTERNOON AND EVENING HOURS...SLACKENING SOMEWHAT LATE AT NIGHT
AND DURING THE MORNING HOURS EACH DAY.

A NW SWELL AROUND 14 SECONDS TONIGHT IS EXPECTED TO SUBSIDE A BIT
LATER TONIGHT AND SAT...BRINGING THE TOTAL WAVE HEIGHT BELOW 10 FT.
SEAS ARE THEN EXPECTED TO REMAIN IN THE 6 TO 9 FT RANGE THROUGH MON.
&&

.PREV DISC... /ISSUED 243 PM PDT FRI APR 17 2015/

SHORT TERM...TONIGHT THROUGH MONDAY...SATELLITE IMAGERY BARELY SHOWS
AN UPPER LEVEL TROUGH MOVING ACROSS WASHINGTON THIS AFTERNOON. MID TO
HIGH LEVEL CLOUDS ARE RACING OUT WELL AHEAD OF THE SURFACE FRONT...
WHICH LAGS BEHIND AND IS FALLING APART JUST OFF THE PAC NW COAST.
HIGH PRESSURE IS ALREADY STRENGTHENING OVER THE NE PACIFIC...WITH
ONSHORE FLOW INCREASING DUE TO THE HIGH OFFSHORE AND THERMAL LOW
PRESSURE OVER THE COLUMBIA BASIN.

SOME STRATUS CAN BE SEEN ON VISIBLE SATELLITE IN THE REMNANTS OF THE
SURFACE FRONT...ALONG AND JUST OFF THE WA/N OR COAST. LOW CLOUDS ARE
EXPECTED TO FILL IN ALONG THE COAST TONIGHT...POTENTIALLY PUSHING UP
THE COLUMBIA INTO THE PDX METRO SAT MORNING. DEPENDING ON HOW
PROLIFIC THE LOW CLOUDS GET...THEY COULD PUSH THROUGH SOME OF THE
COASTAL VALLEYS AS WELL. HOWEVER 500 MB HEIGHTS ARE FORECAST TO START
RISING ALREADY BY SAT MORNING...AND THE RESULTING SUBSIDENCE MAY
LIMIT THE DEPTH AND EXTENT OF LOW CLOUDINESS.

FLOW WILL TURN MORE NORTHERLY SATURDAY AS HIGH PRESSURE STRENGTHENS
ACROSS WASHINGTON AND THERMAL LOW PRESSURE BEGINS TO EXTEND NORTHWARD
FROM CALIFORNIA. THE RESULT SHOULD BE A QUICK BURNOFF OF LOW CLOUDS
SAT MORNING...WITH A MOSTLY SUNNY AND WARM AFTERNOON. 850 MB TEMPS
WILL ALREADY BE ON THE INCREASE BY MIDDAY SATURDAY...REACHING +10 TO
+12 DEG C BY AFTERNOON PER THE 18Z NAM. AS A RESULT TEMPS SATURDAY
SHOULD ONCE AGAIN CLIMB INTO THE LOWER TO MID 70S INLAND...WITH 60S
ALONG THE COAST.

STRONG HIGH PRESSURE ALOFT WILL PERSIST SUNDAY AND MONDAY...CAUSING
THE AIR MASS TO CONTINUE TO WARM OVER THE PAC NW. 850 MB TEMPS TICK
UP 1-2 DEG C EACH DAY SUNDAY AND MONDAY...SUPPORTING HIGH TEMPS A
COUPLE DEGREES WARMER EACH AFTERNOON. 18Z NAM/12Z ECMWF SHOW 850 MB
TEMPS UP TO +14 DEG C BY MONDAY...WHICH WITH FULL SUNSHINE MAY BE
ABLE TO SUPPORT OUR FIRST 80 DEGREE DAY OF THE YEAR INLAND. THERMAL
LOW PRESSURE PUSHES EAST ACROSS THE CASCADES MONDAY...POTENTIALLY
BRINGING ENOUGH ONSHORE FLOW TO COOL OFF THE COAST...BUT ANY MARINE
PUSH WILL LIKELY HOLD OFF UNTIL MON NIGHT/TUE MORNING FOR INLAND
AREAS.WEAGLE

LONG TERM...MONDAY NIGHT THROUGH FRIDAY...CLOUDS EXPECTED TO
INCREASE MONDAY NIGHT AS WESTERLY FLOW WILL PUSH MARINE STRATUS
INLAND. CLOUDY CONDITIONS WITH MAYBE A COUPLE SHOWERS EXPECTED
TUESDAY AHEAD OF THE FRONT FORECAST TO MOVE THROUGH TUESDAY NIGHT OR
EARLY WEDNESDAY. THE ECMWF BRINGS THE FRONT IN EARLIER THAN THE GFS.
A BETTER CHANCE FOR SHOWERS AND POSSIBLY EVEN THUNDERSTORMS WILL BE
TUESDAY NIGHT INTO WEDNESDAY AS THE FRONT MOVES THROUGH. GFS MODEL
SOUNDINGS INDICATE SOME INSTABILITY...BUT CONFIDENCE IS NOT HIGH
ENOUGH FOR ME TO PUT A CHANCE OF THUNDER IN THE FORECAST QUITE YET.
COOLER...MORE SEASONAL TEMPERATURES EXPECTED TO STICK AROUND THROUGH
LATE NEXT WEEK...WITH UNSETTLED NORTHWESTERLY FLOW BRINGING
SHORTWAVES THROUGH THE AREA WITH ASSOCIATED RAIN. -MCCOY

&&

.PQR WATCHES/WARNINGS/ADVISORIES...
OR...NONE.
WA...NONE.
PZ...SMALL CRAFT ADVISORY FOR WINDS UNTIL 11 PM PDT SATURDAY FOR
     COASTAL WATERS FROM CAPE SHOALWATER WA TO FLORENCE OR OUT
     60 NM.

     SMALL CRAFT ADVISORY FOR HAZARDOUS SEAS UNTIL 11 PM PDT THIS
     EVENING FOR COASTAL WATERS FROM CAPE SHOALWATER WA TO
     FLORENCE OR OUT 60 NM.

     SMALL CRAFT ADVISORY FOR ROUGH COLUMBIA RIVER BAR FROM 1 AM
     TO 7 AM PDT 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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