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 291051
AFDPQR

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE PORTLAND OR
334 AM PDT FRI AUG 29 2014

.SYNOPSIS...COOLER WESTERLY FLOW ALOFT IS INCREASING. THIS WILL BRING
CLOUDS AND COOLER AIR TO THE REGION...ALONG WITH A THREAT OF SHOWERS
FOR THIS WEEKEND. BEST CHANCES OF SHOWERS WILL BE ON SATURDAY AND
LATE SUNDAY. DRY AND MILD WEATHER RESUMES NEXT WEEK.
&&

.SHORT TERM...THROUGH SUNDAY...UPPER LOW TROUGH OVER THE GULF OF
ALASKA IS MOVING EAST TO SE AK/WESTERN B.C.  ASSOCIATED SURFACE LOW
NEAR SE ALASKA WITH A FRONT EXTENDING TO THE SOUTH AND SOUTHWEST TO
OFF THE WASHINGTON AND NORTHERN OREGON COAST NEAR 130W. THE SURFACE
FRONT SHOULD STALL NEAR THE COAST THIS AFTERNOON...BUT THE UPPER
PORTION OF THE FRONT SHEARS OFF AND MOVES INLAND IN THE AFTERNOON.
THIS WILL BRING LOW CHANCES FOR PCPN MAINLY AT THE COAST AND SW
WASHINGTON INTERIOR ZONES. LOWER MARINE CLOUDS WILL FILL MUCH OF THE
INTERIOR LOW LANDS DURING THE MORNING...WITH HIGHER LAYERS CONTINUING
THROUGH THE AFTERNOON. COOLER TEMPS TODAY WITH MORE CLOUD COVER AND
LOWERING 500 MB HEIGHTS AS THE UPPER TROUGH MOVES INTO THE REGION. A
SHORTWAVE TROUGH ARRIVES SAT AFTERNOON FOR A LITTLE MORE COOLING AND
A CHANCE OF SHOWERS...AGAIN MAINLY FOR THE COAST AND NORTHERN
INTERIOR ZONES. NO CHANGE IN TRENDS FOR SUN...AS MORE LIKELY TO SEE
DRY CONDITIONS WITH MIX OF SUNSHINE AND CLOUDS. WITH LOW POPS FOR THE
SW WA ZONES.

.LONG TERM...MODELS ARE TRENDING TOWARD ANOTHER SYSTEM ARRIVING SUN
NIGHT AND MON.SURFACE FEATURES WEAKEN AS THE FRONT APPROACHES THE
COAST...BUT 850MB AND 700MB ONSHORE WINDS WILL ADVECT MOISTURE INTO
THE AREA. THIS COMBINED WITH TOTAL PRECIPITABLE WATER AROUND 1.25
INCH WILL INTRODUCE CHANCE POPS TO THE FAR NORTHERN ZONES.  FURTHER
ON IN THE WEEK...THE UPPER RIDGE IS NOT BUILDING QUITE SO STRONGLY AS
BEFORE. THERE IS MORE ENERGY BEING PUT INTO CARVING OUT A TROUGH OVER
WESTERN CANADA THE EVENTUALLY SAGS INTO THE WESTERN U.S LATE IN THE
WEEK. THE AIR MASS WILL BE GENERALLY DRY SO THREAT OF SHOWERS REMAIN
LOW AT THIS POINT. HIGH TEMPERATURES LIKELY AT OR BELOW SEASONAL
NORMALS. THE TIMING AND LOCATION OF THESE SHOWERS ARE
STILL UNCERTAIN AS BOTH THE GFS AND ECMWF HAVE SLIGHTLY DIFFERENT
FORECAST. THESE WILL BE FURTHER REFINED WITH FUTURE UPDATES. /64/26
&&

.AVIATION...LOW MARINE CLOUDS AND FOG ARE RESULTING IN IFR
CONDITIONS FOR THE COAST THIS MORNING. EXPECT MVFR CIGS TO FILL
IN MOST OF THE WILLAMETTE VALLEY THIS MORNING...BETWEEN 12Z AND
15Z. A WEAK FRONT WILL MOVE BRUSH BY THE REGION LATE THIS
MORNING...AND POSSIBLY GENERATE SOME LIGHT RAIN OR DRIZZLE NORTH
OF KSLE. AREAS SOUTH OF KSLE WILL HAVE VFR CONDITIONS THIS
AFTERNOON. ONSHORE FLOW COMBINED WITH FRONTAL PASSAGE MAY KEEP
SOME MVFR CIGS AROUND IN NORTHERN AREAS THROUGH THE LATE
AFTERNOON. MVFR TO VFR CONDITIONS FOR THE COAST AFT 21Z. STRATUS
AND MVFR CIGS WILL RETURN INLAND TONIGHT...AS WILL IFR CONDITIONS
FOR THE COAST.

KPDX AND APPROACHES...SATELLITE IMAGERY SHOWS A PATCH OF STRATUS
JUST EAST OF THE TERMINAL AND ANOTHER BAND OF STRATUS APPROACHING
FROM THE WEST ALONG THE COLUMBIA RIVER. AM CONFIDENT IN MVFR CIGS
FOR THE AIRPORT THIS MORNING...BY 12Z. VFR CONDITIONS EXPECTED AFT
20Z...BUT ONSHORE FLOW AND A WEAK FRONT WILL KEEP CLOUDS WITH
BASES AROUND 5 KFT AGL THROUGH THE AFTERNOON. WINDS GENERALLY
LIGHT AND VARIABLE THIS MORNING WITH A BRIEF PERIOD OF GUSTY NE
WINDS WITH THE FRONTAL PASSAGE AROUND 22Z. TJ

&&

.MARINE...MADE NO CHANGES TO THE PREVIOUS MARINE FORECAST AND THE
PREVIOUS DISCUSSION FOLLOWS...A SERIES OF WEAK FRONTS WILL MOVE
ACROSS THE WATERS THROUGH THE WEEKEND...AND MAINTAIN A WEAK
SURFACE PRESSURE GRADIENT. WINDS WILL REMAIN AROUND 10 KT OUT OF
THE NW...BRIEFLY SHIFTING W AND SW WITH EACH FRONTAL PASSAGE. THE
SEAS WILL COMPRISE OF A SMALL SW SWELL AND STEEP WIND WAVES THE
NEXT COUPLE OF DAYS. A NW SWELL WILL BUILD SATURDAY NIGHT AND PEAK
AROUND 7 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.


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