Area Forecast Discussion
Issued by NWS Portland, OR

Home | Current Version | Previous Version | Text Only | Print | Product List | Glossary On
Versions: 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50
000
FXUS66 KPQR 300403
AFDPQR

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE PORTLAND OR
903 PM PDT FRI AUG 29 2014

.SYNOPSIS...COOLER WESTERLY FLOW ALOFT PREVAILS THROUGH THIS WEEKEND.
THIS WILL BRING PLENTY OF CLOUDS AND COOLER AIR TO THE REGION...ALONG
WITH A PERIODIC THREAT OF SHOWERS. THE BEST CHANCES OF SHOWERS WILL
BE DURING THE DAY SATURDAY AND LATE SUNDAY. DRY AND SEASONAL WEATHER
RETURNS EARLY NEXT WEEK AS WEAK RIDGING TRIES TO BUILD BACK INTO THE
PAC. ANOTHER UPPER TROUGH WILL LIKELY MOVE IN BY THE MIDDLE OF NEXT
WEEK.

&&

.SHORT TERM...EXPECT A COOL AND PRIMARILY CLOUDY WEEKEND AS A BROAD
UPPER LEVEL TROUGH MOVES THROUGH THE PACIFIC NORTHWEST. THERE WILL BE
PERIODIC CHANCES FOR SHOWERS AS PIECES OF SHORTWAVE ENERGY ROTATE
THROUGH THE TROUGH. ONE WEAK SHORTWAVE CURRENTLY VISIBLE ON WATER
VAPOR SATELLITE NEAR 130W WILL APPROACH THE COAST TONIGHT. SOME
ENHANCEMENT IN THE CLOUDS IS APPARENT ON SATELLITE AND THERE ARE ALSO
SOME ECHOES SHOWING UP ON RADAR OFFSHORE THIS EVENING. IT IS POSSIBLE
THAT SOME OF THIS LIGHT PRECIPITATION WILL REACH THE GROUND LATER
THIS EVENING AND OVERNIGHT.

SHOWER CHANCES LOOK MORE IMPRESSIVE FOR TOMORROW. A MORE WELL DEFINED
SHORTWAVE AND UPPER LEVEL SUPPORT FROM THE LEFT EXIT REGION OF A 110+
KT JET WILL PROVIDE BETTER DYNAMICS. ALSO...THE FCST MODELS INDICATE
A SURFACE BOUNDARY OR WEAK FRONT WILL MOVE ONSHORE BEGINNING AROUND
MIDDAY. GIVEN THAT THE MAJORITY OF THE FCST MODELS ARE INDICATING
MEASURABLE PRECIPITATION ACROSS THE ENTIRE CWA...DECIDED TO NUDGE
POPS UP A BIT WITH THE EVENING UPDATE.

THE MAIN UPPER LEVEL TROUGH AXIS WILL BE EAST OF THE CASCADES BY
SUNDAY MORNING...BUT EXPECT CLOUDY AND COOL CONDITIONS TO PERSIST AS
WE REMAIN IN CYCLONIC FLOW ON THE BACK SIDE OF THE TROUGH. AN
ADDITIONAL WEAK SHORTWAVE IS BEING MODELED TO MOVE ONSHORE LATE IN
THE DAY...AND MAY PROVIDE ENOUGH FORCING TO WRING OUT A FEW MORE
LIGHT SHOWERS THROUGH SUNDAY NIGHT.

500 MB HEIGHTS INCREASE SOME ON MONDAY AS WEAK RIDGING ATTEMPTS TO
REBUILD OVER THE PACIFIC NORTHWEST. THIS SHOULD NUDGE TEMPERATURES
BACK UP TOWARD SEASONAL NORMALS AND PUT AN END TO THE SHOWER CHANCES.
PYLE

.LONG TERM...THE MODELS CONTINUE TO CARVE OUT A TROUGH OVER WESTERN
CANADA THAT EVENTUALLY MOVES INTO THE PACIFIC NORTHWEST ON TUESDAY.
THIS TROUGH STICKS AROUND FOR A WHILE BEFORE BEING SHEARED OFF TO
THE EAST ON THURSDAY. STILL KEEPING A SLIGHT CHANCE OF SHOWERS OVER
THE EXTREME NORTHERN PORTIONS OF THE CWA ON TUESDAY AND WEDNESDAY
DESPITE THE DRY AIR MASS ASSOCIATED WITH THE SYSTEM. TEMPERATURES
WILL GENERALLY BE NEAR SEASONAL NORMALS. LATE NEXT WEEK THE MODELS
TRY TO DEVELOP A CUTOFF LOW. THIS HAS ADDED A LOT OF UNCERTAINTY TO
THE FORECAST. AS OF NOW...LEANING TOWARDS IT BEING CLEARER AND DRIER
FOR THE END OF NEXT WEEK WITH TEMPERATURES SLIGHTLY ABOVE SEASONAL
NORMALS.

&&

.AVIATION...CONDITIONS ARE VFR OVER AREAS INLAND FROM THE COAST
THIS EVENING AND WILL REMAIN SO MUCH OF TONIGHT. HOWEVER...STRATUS
WITH MVFR CIGS IS EXPECTED TO MOVE INLAND AND REACH INTERIOR
TERMINALS AROUND 30/10Z SIMILAR TO LAST NIGHT. STRATUS WILL THEN
LIFT TO VFR AND BEGIN TO BREAK UP MID TO LATE MORNING SATURDAY.

AT THE COAST...STRATUS AND FOG WITH LIFR CIGS AND VIS ALREADY
ENCOMPASSES MUCH OF THE COASTAL STRIP (INCLUDING KONP) AND IS
EXPECTED TO FILL IN OVER THE REST OF THE COAST WITHIN THE NEXT FEW
HOURS AND THEN EDGE FURTHER INLAND OVERNIGHT. STRATUS AND FOG IS
EXPECTED TO BACK OFF SHORE LATE MORNING SATURDAY WITH IFR TO MVFR
CONDITIONS RETURNING.

THERE WILL BE A CHANCE FOR LIGHT SHOWERS SATURDAY AFTERNOON
...PRIMARILY AT THE COAST AND NORTH OF KSLE.

KPDX AND APPROACHES...VFR CONDITIONS EXPECTED THIS EVENING AND
EARLY TONIGHT WITH SCT-BKN DECKS AT OR ABOVE 7 KFT. STRATUS WITH
MVFR CIGS IS EXPECTED TO MOVE IN AROUND 30/10Z AND REMAIN THROUGH
MID MORNING. CIGS WILL LIFT TO VFR LATE MORNING SATURDAY. THERE IS
A CHANCE FOR SOME LIGHT SHOWERS SAT AFTERNOON...HOWEVER CONDITIONS
ARE EXPECTED TO REMAIN VFR. -WRIGHT

&&

.MARINE...LIGHT WINDS AND SEAS WILL CONTINUE OVER THE WATERS
TONIGHT AS A WEAK FRONT MOVES INLAND. ANOTHER WEAK FRONT WILL
MOVE ACROSS THE WATERS SATURDAY AND A THIRD...POTENTIALLY STRONGER
FRONT SUNDAY AFTERNOON AND NIGHT. 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 SATURDAY
NIGHT AND PEAK AROUND 6 FEET ON SUNDAY. HIGH PRESSURE WILL REBUILD
MONDAY NIGHT AND TUESDAY AND PERSISTENT NORTHERLY WINDS WILL
RETURN TO THE WATERS. WRIGHT/SCHNEIDER

&&

.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.


USA.gov is the U.S. government's official web portal to all federal, state and local government web resources and services.