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 300423
AFDPQR

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE PORTLAND OR
900 PM PDT SAT AUG 29 2015


.SYNOPSIS...A BAND OF RAIN OVER SOUTHWEST WASHINGTON AND NORTHWEST
OREGON WILL GRADUALLY SHIFT SOUTHEASTWARD ACROSS THE AREA TONIGHT AND
EARLY SUNDAY. EXPECT A MIX OF SUNSHINE AND AN OCCASIONAL SHOWER ON
SUNDAY. ANOTHER FRONT WILL STALL OVER WASHINGTON AND BRING A THREAT
FOR ADDITIONAL SHOWERS TO MAINLY OUR FAR NORTHERN ZONES MONDAY. THE
SHOWERY WEATHER SHOULD THEN SPREAD SOUTHWARD MIDWEEK AND MAINTAIN
NEAR AVERAGE TO SLIGHTLY BELOW AVERAGE TEMPERATURES.


&&


.EVENING UPDATE...WATER VAPOR SATELLITE IMAGERY REVEALS A HIGHLY
AMPLIFIED PATTERN ACROSS THE PACIFIC OCEAN WITH A MEAN LONGWAVE
TROUGH CENTERED OVER THE WEST COAST. THE NEXT SHORTWAVE TROUGH IS
PUSHING SOUTHEASTWARD OUT OF THE GULF OF ALASKA AND CURRENTLY RESIDES
NEAR 130W OFF THE WASHINGTON COAST. A LOW LEVEL FRONT AHEAD OF THIS
SYSTEM IS CURRENTLY PUSHING ONTO THE OREGON COAST WITH FRONTAL
PASSAGE OCCURRING EARLIER THIS EVENING AT ASTORIA AND TILLAMOOK. THIS
FEATURE WILL BE THE PRIMARY FOCUS FOR PRECIPITATION OVERNIGHT AS IT
SLOWLY DROPS SOUTHEASTWARD ACROSS THE AREA...GENERALLY BRINGING
ANOTHER QUARTER TO THREE QUARTERS OF AN INCH OF RAIN...LOCALLY MORE
IN THE HIGHER TERRAIN AND ALONG THE COAST. LESSER AMOUNTS ARE MOST
LIKELY TOWARDS EASTERN LANE AND LINN COUNTIES WHERE THE FRONT WILL
STRUGGLE TO REACH BEFORE FALLING APART SUNDAY MORNING.

SURFACE OBSERVATIONS INDICATE 35 TO 45 MPH GUSTS CONTINUE ALONG THE
BEACHES AND HEADLANDS OF THE CENTRAL OREGON COAST AHEAD OF THE
AFOREMENTIONED FRONT. THESE WINDS WILL EASE CONSIDERABLY UPON FRONTAL
PASSAGE...WHICH SHOULD OCCUR BETWEEN 10 PM AND MIDNIGHT.
ELSEWHERE...WINDS SHOULD HOLD RELATIVELY STEADY OVERNIGHT...PERHAPS
BRIEFLY INCREASING RIGHT AHEAD OF FRONTAL PASSAGE IN THE WILLAMETTE
VALLEY...BUT OVERALL WIND GUSTS SHOULD STAY WELL BELOW 30 MPH GOING
FORWARD TONIGHT AND SUNDAY.

AN EXAMINATION OF INFRARED SATELLITE IMAGERY REVEALS PLENTY OF COLD
AIR CUMULUS WITH CLOUD TOPS REACHING -35C CURRENTLY NEAR 130W. THE
DEEPEST CONVECTION IS TIED TO THE -21C TO -23C 500MB ISOTHERMS. WHILE
THE COLDEST 500MB AIR WILL MOVE NORTH OF OUR CWA LATE TONIGHT AND
SUNDAY MORNING...IT APPEARS WE WILL BE CLIPPED BY ENOUGH -21C TO -22C
500MB TEMPERATURES ALOFT TO AT LEAST MENTION THUNDER AS A POSSIBILITY
NORTH OF A LINE EXTENDING BETWEEN SEASIDE AND SCAPPOOSE SUNDAY
MORNING. A LOWERING SUBSIDENCE INVERSION ON SUNDAY AFTERNOON SHOULD
LIMIT THE DEPTH OF INSTABILITY AND GRADUALLY RESULT IN DECREASING
SHOWER COVERAGE AND INTENSITY LATE SUNDAY AFTERNOON AND EVENING
ACROSS THE AREA.

ANOTHER SHORTWAVE TROUGH CURRENTLY RESIDING OVER THE ALEUTIAN ISLANDS
WILL PUSH INTO WESTERN BRITISH COLUMBIA MONDAY AND PUSH ANOTHER FRONT
INTO THE PACIFIC NORTHWEST. GIVEN THE UPPER LEVEL DYANMICS WITH THIS
SYSTEM STAY IN BRITISH COLUMBIA...THIS SYSTEM WILL QUICKLY LOSE STEAM
AND STALL OVER NORTHWESTERN WASHINGTON ON MONDAY. NONETHELESS...IT
WILL LIKELY BRING A FEW SHOWERS AND CERTAINLY MORE CLOUD COVER ACROSS
OUR FAR NORTHERN ZONES ON MONDAY.

MODELS GENERALLY AGREE A THIRD SHORTWAVE TROUGH CURRENTLY OVER VERY
NORTHERN ALASKA AND THE ARCTIC OCEAN WILL SLIDE SOUTHWARD AND PUSH
INTO THE PACIFIC NORTHWEST MIDWEEK. THIS SHOULD BRING ANOTHER GOOD
THREAT OF SHOWERS AND KEEP TEMPERATURES BELOW SEASONAL THROUGH AT
LEAST MIDWEEK. /NEUMAN


.LONG TERM...TUESDAY NIGHT THROUGH SATURDAY...PREVIOUS DISCUSSION
BELOW...AN UPPER TROUGH WILL REMAIN ALONG THE PACIFIC NORTHWEST COAST
THROUGH MUCH OF THE EXTENDED PERIOD. THE MODELS SHOW ANOTHER DECENT
PIECE OF ENERGY SWINGING THROUGH AROUND WEDNESDAY OR THURSDAY FOR A
BETTER CHANCE OF SHOWERS...BUT THE TIMING VARIES A BIT. THE MODELS
ARE INDICATING IT MAY DRY OUT AND START TO WARM UP SOME NEXT WEEKEND.
TOLLESON


&&


.AVIATION...A WEAK FRONT MOVING ONSHORE CURRENTLY BRINGING
PERIODS OF REDUCED CIGS AND VSBY TO THE COAST UNDER MODERATE TO
HEAVY RAIN BANDS. EXPECT CIGS TO LOWER TOWARDS MVFR OVERNIGHT AND
PERSIST THROUGH SUNDAY MORNING. WILL ALSO CONTINUE TO SEE PERIODS
OF GUSTY SOUTHERLY WINDS THROUGH LATE TONIGHT. COASTAL CONDITIONS
LOOK TO IMPROVE TOWARDS VFR BY SUNDAY AFTERNOON.

CONDITIONS CURRENTLY VFR ACROSS THE INTERIOR. MAY SEE BRIEF
PERIODS OF REDUCED CIGS AND VSBY AT INTERIOR TAF SITES UNDER
HEAVIER RAIN BANDS...BUT CONDITIONS LOOK TO REMAIN GENERALLY VFR
THE NEXT 24 HOURS.

WILL ALSO SEE A SLIGHT CHANCE OF THUNDERSTORMS AS THE FRONT MOVES
ACROSS THE AREA. HOWEVER...CONFIDENCE REMAINS TOO LOW TO INCLUDE
IN THE UPCOMING TAF PACKAGE.


KPDX AND APPROACHES...CONDITIONS GENERALLY VFR THE NEXT 24 HOURS.
HOWEVER...BRIEF PERIODS OF REDUCED CIGS AND VSBY POSSIBLE UNDER
HEAVIER RAIN BANDS AS THE FRONT MOVES ACROSS THE AREA. WILL ALSO
SEE A SLIGHT CHANCE OF THUNDERSTORMS WITH THE FRONT. /64


&&


.MARINE...THE LOW PRESSURE SYSTEM THAT BROUGHT STORM AND GALE
FORCE WINDS TO OUR WATERS TODAY HAS MOVED NORTH OF OUR AREA
ALLOWING WINDS TO SUBSIDE THIS EVENING. A WEAK FRONT WILL MOVE
ACROSS THE WATERS TONIGHT AND COULD BRING A CHANCE FOR ISOLATED
THUNDERSTORMS. SOUTHWESTERLY WINDS WILL CONTINUE TO GUST TO AROUND
25 KT SO WILL LET THE GALE WARNING EXPIRE AND ISSUE A SMALL CRAFT
ADVISORY FOR WINDS FOR THE INNER WATERS THROUGH TONIGHT...AND THE
OUTER WATERS THROUGH SUNDAY MORNING. WINDS EASE FURTHER SUNDAY
AFTERNOON...BUT WILL FLIRT WITH ADVISORY CRITERIA THROUGH MUCH OF
NEXT WEEK DUE TO AN UNSETTLED WEATHER PATTERN.

SEAS ARE CURRENTLY AROUND 11 TO 13 FT SO HAVE ALSO ISSUED A SMALL
CRAFT ADVISORY FOR HAZARDOUS SEAS THROUGH TONIGHT. SEAS FALL TO
AROUND 8 TO 9 FT LATE TONIGHT AND REMAIN IN THIS RANGE THROUGH
MUCH OF NEXT WEEK DUE TO A SWELL BEING GENERATED IN THE GULF OF
ALASKA. /64


&&


.PQR WATCHES/WARNINGS/ADVISORIES...
OR...NONE.
WA...NONE.
PZ...SMALL CRAFT ADVISORY FOR WINDS UNTIL 9 AM PDT SUNDAY FOR
     WATERS FROM CAPE SHOALWATER WA TO FLORENCE OR FROM 10 TO
     60 NM.

     SMALL CRAFT ADVISORY FOR HAZARDOUS SEAS UNTIL 1 AM PDT
     SUNDAY FOR COASTAL WATERS FROM CAPE SHOALWATER WA TO
     FLORENCE OR OUT 60 NM.

     SMALL CRAFT ADVISORY FOR WINDS UNTIL 1 AM PDT SUNDAY FOR
     COASTAL WATERS FROM CAPE SHOALWATER WA TO FLORENCE OR
     OUT 10 NM.

     SMALL CRAFT ADVISORY FOR ROUGH COLUMBIA RIVER BAR UNTIL 9 AM
     PDT SUNDAY...AND FROM 3 PM TO 10 PM PDT SUNDAY.

&&


$$

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.