Area Forecast Discussion
Issued by NWS Portland, OR

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FXUS66 KPQR 302200
AFDPQR

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE PORTLAND OR
300 PM PDT SAT AUG 30 2014

.SYNOPSIS...COOLER WESTERLY FLOW ALOFT PREVAILS THROUGH THIS
WEEKEND..WITH A SERIES OF WEAK SURFACE FRONTS. THIS WILL BRING
PLENTY OF CLOUDS AND COOLER AIR TO THE REGION...ALONG WITH PERIODIC
RAIN SHOWERS. THE BEST CHANCES OF SHOWERS WILL BE THIS AFTERNOON AND
EVENING. WEAK RIDGING TRIES TO BUILD BACK INTO THE PACIFIC
MONDAY...BEFORE A DEEPER TROUGH MOVES OVER THE AREA TUESDAY THROUGH
THE END OF THE WEEK.

&&

.SHORT TERM...TODAY THROUGH TUESDAY NIGHT...

A DISCONNECTED LINE OF MODERATE SHOWERS HAS DEVELOPED ALONG A WEAK
FRONT CURRENTLY MOVING ACROSS THE VALLEY. CURRENT ORIENTATION OF THE
JET STREAM PUTS US IN THE AREA OF FAVORABLE FORCING IN THE LEFT EXIT
REGION WHICH HAS HELPED TO PRODUCE STRONGER SHOWERS THIS AFTERNOON
AND EVEN A LONE LIGHTNING STRIKE IN NORTHERN MARION COUNTY AROUND 145
PM. AS EXPECTED...RAIN HAS MOSTLY CLEARED OUT ON THE COAST BEHIND THE
FRONT WITH THE EXCEPTION OF A BAND OF LIGHT SHOWERS NEAR NEWPORT
WHICH MAY BE A SIDE EFFECT OF COLOCATION WITH THE JET STREAK. CLOUDS
WILL LINGER BEHIND THE FRONT BUT THERE SHOULD BE ENOUGH BREAKS
OVERNIGHT TO COOL DOWN A COUPLE OF DEGREES MORE THAN LAST NIGHT.

ANOTHER WEAK FRONT WILL MOVE ACROSS THE AREA SUNDAY. THE CHANCE FOR
RAIN IS WEAKER WITH THIS SYSTEM AS THE UPPER JET SHIFTS
NORTHWARD...REDUCING ATMOSPHERIC LIFT. THE PRECIPITATION ON
SUNDAY WILL BE VERY LIGHT AND BE RESTRICTED TO THE NORTHERNMOST PART
OF THE FORECAST AREA WITH MODELS CONTINUING TO TREND DOWNWARD WITH
POPS. AN UPPER RIDGE WILL BUILD MONDAY...BUT THE MODELS HAVE BEEN
BACKING OFF ON THE STRENGTH OF THE RIDGE AND EXPECT ANOTHER WEAK
FRONT TO CLIP THE NORTHERN AREAS MONDAY AFTERNOON AND EVENING.
RIDGING TRIES TO ESTABLISH ITSELF ON TUESDAY BUT AN UPPER LEVEL
TROUGH STARTS TO DIG INTO SE BRITISH COLUMBIA. ALTHOUGH WEAK...AN
ARGUMENT COULD BE MADE FOR SOME ENHANCED FORCING DUE TO A WEAK JET
STREAK MOVING INTO NW WASHINGTON SO OVERALL DECREASED POPS TUESDAY
BUT KEPT THEM MENTIONABLE ACROSS THE SW WASHINGTON PART OF THE
FORECAST AREA. BOWEN/TJ

.LONG TERM...THE MODELS CONTINUE TO HINT AT A TROUGH MOVING INTO THE
PACIFIC NORTHWEST ON TUESDAY. THIS TROUGH LOOKS TO STICK AROUND
THROUGH THE END OF NEXT WEEK. STILL KEEPING A SLIGHT CHANCE OF
SHOWERS IN THE FORECAST THROUGH THURSDAY FOR THE NORTHERN PORTIONS
OF THE CWA. TEMPERATURES WILL TREND TOWARDS SEASONAL NORMALS. LATE
NEXT WEEK THE MODELS CONTINUE TO TRY TO DEVELOP A CUTOFF
LOW...HOWEVER...DIFFERENCES BETWEEN THE VARIOUS MODELS AND MODEL
RUNS HAVE CREATED A LOT OF UNCERTAINTY. STILL LEANING TOWARDS IT
BEING DRIER AND SLIGHTLY WARMER FOR NEXT WEEKEND.

&&

.AVIATION...LIGHT SHOWERS WILL CONTINUE THROUGH THIS
EVENING...THEN GRADUALLY DECREASE FROM SOUTH TO NORTH. MOSTLY A
MIX OF MVFR AND VFR CONDITIONS INLAND...WITH IFR CONDITIONS
LIKELY IN SHOWERS. MOIST ONSHORE FLOW PERSISTS OVERNIGHT...LIKELY
BRINGING SOME 2000-2500 FT CIGS NEAR SUNRISE EARLY SUNDAY AM ALONG
THE LOWER COLUMBIA RIVER. OTHERWISE...MOST INLAND SITES WILL
REMAIN VFR WITH CIGS AROUND 5000 FT. COASTAL SITES WILL REMAIN
MVFR AND IFR THROUGH SUNDAY AM.

KPDX AND APPROACHES...MIX OF MVFR AND VFR CONDITIONS WITH CIGS
BETWEEN 2500-3500 FT. EXPECT LOWER CONDITIONS IN SHOWERS THROUGH
04-06Z SUNDAY. A FEW 2000 FT CIGS ARE EXPECTED AGAIN FROM 14-17Z
SUNDAY. /27

&&

.MARINE...AFTER A WEAK FRONTAL PASSAGE EARLIER TODAY...THE NEXT
STRONGER FRONT MOVES ACROSS THE COASTAL WATERS LATE SUNDAY. MODELS
SHOW LIGHT SW WINDS THROUGH SUNDAY...BEFORE BACKING TO THE NW BY
MONDAY. THE SEAS WILL COMPRISE OF A SMALL SW SWELL OF 1 TO 2
FEET AT AROUND 15 SECONDS AND A NORTHWEST FRESH SWELL FROM THE
GULF OF ALASKA AROUND 9 TO 10 SECONDS. LIGHT WIND WAVES THE NEXT
COUPLE OF DAYS. A NW SWELL WILL BUILD TONIGHT AND PEAK AROUND 6
FEET ON SUNDAY. HIGH PRESSURE WILL REBUILD MONDAY NIGHT AND
TUESDAY AND PERSISTENT NORTHERLY WINDS WILL RETURN TO THE WATERS.

&&

.PQR WATCHES/WARNINGS/ADVISORIES...
OR...NONE.
WA...NONE.
PZ...NONE.
&&

$$

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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