Area Forecast Discussion
Issued by NWS Portland, OR

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000
FXUS66 KPQR 050911 CCA
AFDPQR

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE PORTLAND OR
208 AM PDT THU MAY 5 2016

.SYNOPSIS...THE COOL AND SHOWERY PATTERN ACROSS THE REGION WILL GIVE
WAY TO DECREASING CLOUDS...WARMING TEMPERATURES AND SHOWERS BECOMING
INCREASINGLY CONFINED TO THE CASCADES THURSDAY AND FRIDAY. HIGH
PRESSURE BUILDING OVER THE REGION FRIDAY AND SATURDAY WILL BRING A
RETURN TO WELL ABOVE AVERAGE TEMPERATURES. A WEAK FRONT WILL LIKELY
INCREASE MARINE CLOUDS AND COOL TEMPERATURS CLOSER TO SEASONAL NORMS
FOR SUNDAY AND MONDAY.
&&

.SHORT TERM...AN UPPER LEVEL LOW WAS OFF THE CENTRAL CA COAST EARLY
THIS MORNING...WITH A TROUGH EXTENDING N JUST OFF THE PACIFIC NW
COAST. S FLOW ALOFT AHEAD OF THE TROUGH AXIS BROUGHT SOME SHOWERS
AND THUNDERSTORMS TO THE INTERIOR PACIFIC NW WED...BUT BY THIS
MORNING MOST OF THE ACTIVITY WAS WELL E OF THE CASCADES AND DOWN IN
NORTHERN CA. MODELS IN GOOD AGREEMENT IN SHOWING THE UPPER LOW
FURTHER CUTTING OFF AND MOVING TO THE DESERT SW OVER THE NEXT FEW
DAYS AS UPPER LEVEL RIDGING BUILDS IN FROM THE W TO THE N OF THE
LOW...ACROSS WA. THIS BACKS THE MID AND UPPER FLOW TO THE SE THIS
AFTERNOON...TO THE E BY FRI AND NE BY SUN. MODEL SOUNDINGS INDICATE
BEST INSTABILITY OVER THE FORECAST AREA TODAY OVER THE CASCADES...
WHILE FURTHER W WARMING IN THE MID LEVELS APPEARS LIKELY TO LIMIT
CONVECTIVE PROSPECTS TODAY. WILL CONTINUE TO INDICATE CHANCE TO
LIKELY POPS FOR SHOWERS AND THUNDERSTORMS MAINLY THIS AFTERNOOON AND
EVENING OVER THE CASCADES.

AIR MASS IN GENERAL EXPECTED TO STABILIZE FRI AND SAT AS THE UPPER
RIDGE BUILDS IN OVER WA. CHANCES FOR SHOWERS AND THUNDERSTORMS WILL
BE DIMINISHED FRI...AND LIMITED MAINLY TO THE LANE COUNTY CASCADES
AND FOOTHILLS. WILL CONTINUE WITH A DRY FORECAST FOR SAT AS THE
RIDGE CONTINUES TO STRENGTHEN. LOW LEVEL FLOW FOR THE NEXT FEW DAYS
EXPECTED TO REMAIN ONSHORE FROM THE NW...BUT AFTER THE EXTENSIVE
MARINE CLOUDS THIS MORNING SUBSIDENCE IS EXPECTED TO GREATLY LIMIT
THE EXTENT AND COVERAGE OF MARINE CLOUDS FRI AND SAT. SUBSIDENCE
WILL ALSO RESULT IN A PROGRESSIVELY WARMER AIR MASS DURING THE NEXT
FEW DAYS...WITH MODEL H8 TEMPS WAMRING TO AROUND 14 DEG C INLAND BY
FRI AND SAT. THE ONSHORE FLOW WILL KEEP THE WARMEST WEATHER INLAND
WHERE HIGHS SHOULD ONCE AGAIN BE AROUND 80 IN THE LOWEST VALLEYS.

.LONG TERM...00Z GFS AND EC MODEL RUNS BOTH INDICATE A FAIRLY STRONG
NW MARINE PUSH SAT NIGHT INTO SUN AS THE UPPER FLOW TURNS TO THE NW
AND A SHORTWAVE DIGS ACROSS SUN. WITH THE INFLUX OF COOLER MARINE AIR
AND THE SHORTWAVE...WILL ALSO ADD IN A CHANCE OF SOME DRIZZLE ACROSS
THE N LOWER ELEVATIONS LATE SAT NIGHT INTO SUN.

OTHERWISE...HIGH PRES WILL BUILD OVER THE REGION...WITH MILD
TEMPERATURES AND STABLE NW FLOW ALOFT. THIS WILL KEEP A MORE JUNE
LIKE PATTERN...WITH LATE NIGHT/AM CLOUDS THEN MOSTLY
CLEAR SKIES. MAIN EFFECT WILL BE INCREASED ONSHORE FLOW FOR COOLER
TEMPS SUN AND MON. COASTAL AREAS MAY NOT SEE MUCH CLEARING
UNTIL LATER IN THE AFTERNOONS. TUE AND WED WILL SEE WEAKENING
ONSHORE FLOW WITH WARMING AND DRY WEATHER.
&&


.AVIATION...SATELLITE AND MODEL CROSS-SECTIONS SUGGEST MULTIPLE
CLOUD LAYERS EXTENDING TO AROUND FL100. AT 09Z CIGS PRIMARILY 025
TO 035. DO NOT EXPECT MUCH CHANGE THROUGH 16Z. GENERAL IMPROVEMENT
AFTER 16Z WITH PREDOMINANT VFR ACROSS THE REGION BY 19Z. THERE
WILL BE A THREAT OF -SHRA THIS MORNING SOUTH OF A KONP-KCVO LINE.
ANY AFTERNOON -SHRA SHOULD BE CONFINED TO THE HIGHER CASCADES.
EXPECT AREAS OF MVFR CIGS TO RETURN TO THE COAST AFTER 04Z FRI.

KPDX AND APPROACHES...HIGH-END MVFR AT THE TERMINAL AS OF
09Z...BUT THERE ARE AREAS OF LOW-END VFR IN THE VICINITY. EXPECT
MAINLY MVFR CONDITIONS THROUGH ABOUT 18Z THEN IMPROVEMENT TO VFR.
WEISHAAR

&&

.MARINE...LITTLE CHANGE IN THE OVERALL MARINE PATTERN FOR THE NEXT
COUPLE OF DAYS. SMALL CRAFT ADVISORY FOR WIND CONTINUES FOR THE
OUTER MARINE ZONES. EXTENDED THE ADVISORY THROUGH 12Z FRI AS
LATEST MODEL GUIDANCE SUGGESTS 20 TO 25 KT BOUNDARY LAYER WIND
SPEEDS WITH 975 MB SPEEDS AROUND 30 KT. IT APPEARS WIND SPEEDS
OVER THE OUTER WATERS EASE JUST A BIT THIS AFTERNOON...BUT RAMP UP
AGAIN THU EVENING INTO FRI MORNING.

THE INNER ZONES ARE A LITTLE MORE TRICKY. OPTED TO EXTEND THE
SMALL CRAFT ADVISORY FOR WIND IN PZZ255 UNTIL 08Z FRI WHERE GUSTS
TO 25 KT WILL PERSIST. WIND SPEEDS OVER THE INNER WATERS EASE A
LITTLE LATE THIS MORNING INTO THE EARLY AFTERNOON...ENOUGH SO THAT
SMALL CRAFT ADVISORY WIND SPEEDS ARE NOT EXPECTED FOR PZZ250.
HOWEVER...MODELS SHOW SPEEDS PICKING UP AGAIN LATE THU AFTERNOON
TO WARRANT ANOTHER SMALL CRAFT ADVISORY FOR PZZ250. ALL THE SMALL
CRAFT WIND ADVISORIES WILL LIKELY NEED EXTENDED THROUGH SAT.

OVERALL...WIND SPEEDS DECREASE SAT NIGHT AND SUN AS AN UPPER LEVEL
TROUGH APPROACHES THE WATERS FROM THE NW. THIS TROUGH WILL INDUCE
A FAIRLY STRONG MARINE SURGE...RESULTING IN 15 TO 20 KT WIND
SPEEDS.

THE GENERAL SEA STATE CONTINUES TO BE DOMINATED BY A LARGE WIND-
WAVE COMPONENT. SHORT PERIODS FROM THE FRESH SWELL ARE LEADING TO
CHOPPY SEAS. EXTENDED THE SMALL CRAFT FOR HAZARDOUS SEAS THROUGH
06Z FRI. WEISHAAR

&&

.PQR WATCHES/WARNINGS/ADVISORIES...
OR...NONE.
WA...NONE.
PZ...SMALL CRAFT ADVISORY FOR WINDS UNTIL 5 AM PDT FRIDAY FOR WATERS
     FROM CAPE SHOALWATER WA TO FLORENCE OR FROM 10 TO 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 WINDS UNTIL 5 AM PDT EARLY THIS
     MORNING FOR COASTAL WATERS FROM CAPE SHOALWATER WA TO
     CASCADE HEAD OR OUT 10 NM.

     SMALL CRAFT ADVISORY FOR WINDS FROM 3 PM THIS AFTERNOON TO 11
     PM PDT THIS EVENING FOR COASTAL WATERS FROM CAPE
     SHOALWATER WA TO CASCADE HEAD OR OUT 10 NM.

     SMALL CRAFT ADVISORY FOR WINDS UNTIL 1 AM PDT FRIDAY FOR
     COASTAL WATERS FROM CASCADE HEAD TO FLORENCE OR OUT 10 NM.

     SMALL CRAFT ADVISORY FOR ROUGH COLUMBIA RIVER BAR UNTIL 6 AM
     PDT EARLY THIS MORNING.

     SMALL CRAFT ADVISORY FOR ROUGH COLUMBIA RIVER BAR FROM 2 PM
     THIS AFTERNOON TO 6 PM PDT THIS EVENING.

&&

$$

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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