Area Forecast Discussion
Issued by NWS Portland, OR

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FXUS66 KPQR 030943
AFDPQR

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE PORTLAND OR
243 AM PDT TUE MAY  3 2016

.SYNOPSIS...SLOW MOVING COLD FRONT INCHING TOWARD THE COAST WILL
CONTINUE TO BRING THE THREAT OF SHOWERS TO THE REGION THROUGH
WEDNESDAY...WITH A STRAY THUNDERSTORM POSSIBLE EACH DAY IN THE
CASCADES. AS LOW-LEVEL FLOW TURNS INCREASINGLY ONSHORE...EXPECT
COOLER TEMPERATURES TO SPREAD INLAND TODAY AND WEDNESDAY. DRYING
TREND IS EXPECTED LATER IN THE WEEK AS THE REMNANTS OF THE FRONT
REORGANIZE INTO A CUTOFF LOW OVER CALIFORNIA. THIS WILL BRING A
RETURN TO OFFSHORE FLOW...WITH WARM AND DRY WEATHER THIS WEEKEND AS
HIGH PRESSURE BUILDS INTO THE PACIFIC NORTHWEST.

&&

.SHORT TERM...TODAY THROUGH THURSDAY...AFTER YET ANOTHER DAY OF
RECORD BREAKING WARMTH FOR SOME...TODAY SHOULD BE A BIT COOLER ACROSS
SW WA/NW OR AS LOW-LEVEL FLOW TURNS INCREASINGLY ONSHORE. PRESSURE
GRADIENTS HAVE FLIPPED AROUND TO ONSHORE OVER THE PAST FEW HOURS...
BOTH ON THE SYNOPTIC AND MESO SCALES. KTTD-KDLS WAS AT ABOUT +3 MB AS
OF 2 AM...WITH KOTH-KGEG GRADIENTS TURNING ONSHORE AS WELL. THIS
WILL USHER IN A COOLER AIR MASS FROM THE PACIFIC AND HIGHS TODAY
SHOULD BE A GOOD 10-20 DEGREES COOLER THAN MONDAY FOR INLAND
AREAS...AROUND 70 IN THE VALLEYS. STRENGTHENING HIGH PRESSURE OVER
THE NE PACIFIC WILL KEEP ONSHORE FLOW GOING THROUGH AT LEAST
THURSDAY...BRINGING TEMPERATURES DOWN CLOSER TO NORMAL WED/THU.

SHOWERS CONTINUE TO DEVELOP IN THE SHALLOW/WEAK INSTABILITY BETWEEN
700-500 MB THIS MORNING...BUT DESPITE BEING ELEVATED CONVECTION THE
TOPS ARE STILL GENERALLY NOT HIGH/COLD ENOUGH TO CAUSE THE REQUISITE
CHARGE SEPARATION FOR LIGHTNING. DECIDED TO LEAVE THUNDER OUT OF THE
FORECAST THIS MORNING...THOUGH A STRAY STRIKE OR TWO LIKE THE ONES
RECENTLY OBSERVED OVER THE STRAIT OF JUAN DE FUCA ARE NOT OUT OF THE
QUESTION ANYWHERE. MODEL SOUNDINGS GENERALLY SHOW LITTLE CHANGE OVER
THE NEXT 48 HOURS...WITH LIMITED INSTABILITY AT BEST ABOVE 500 MB.
SURFACE-BASED CONVECTION WILL BRING MAINLY AFTERNOON/EVENING SHOWERS
THROUGH WEDNESDAY...BUT ALSO APPEARS TOO SHALLOW FOR LIGHTNING WEST
OF THE CASCADES EITHER DAY.

THE REMNANTS OF OUR DYING COLD FRONT/UPPER TROUGH ARE PROGGED TO
REORGANIZE INTO A CUTOFF UPPER LOW OVER CALIFORNIA BY THE END OF THE
WEEK...WHILE MOST MODELS BUILD AN UPPER RIDGE ACROSS SOUTHERN BC AND
WASHINGTON. THIS WILL GRADUALLY BRING A RETURN TO DRIER OFFSHORE FLOW
ALOFT BY THE WEEKEND...WITH THURSDAY APPEARING TO BE THE BEGINNING OF
THAT TRANSITION. SHOULD SEE SHOWERS DIMINISH AND BECOME INCREASINGLY
CONFINED TO THE CASCADES THU/FRI AS A RESULT.  WEAGLE

.LONG TERM...THURSDAY NIGHT THROUGH MONDAY.  MODELS REMAIN IN FAIR
AGREEMENT THROUGH THE EXTENDED PERIOD AS THE UPPER LEVEL LOW
CONTINUES TO ADVANCE INTO THE GREAT BASIN WHILE AN UPPER RIDGE
BEGINS TO NOSE INTO THE PACIFIC NORTHWEST FROM THE NORTHEAST
PACIFIC. THIS WILL BRING AN END TO THE SHOWER CHANCES FOR MUCH OF
THE AREA ON FRIDAY...THOUGH WILL MAINTAIN A SLIGHT CHANCE FOR
SHOWERS OVER THE SOUTHERN PORTIONS OF THE CASCADE ZONES.
TEMPERATURES WILL WARM INTO THE WEEKEND BACK ABOVE SEASONAL NORMS
AS HEIGHTS RISE AND THE AIR MASS WARMS.   CULLEN

&&

.AVIATION...MVFR ALONG THE COAST AT 10Z AS A SOUTH WIND REVERSAL
CONTINUES. LIKELY SEEING SOME OF THE MVFR CIGS PUSHING UP THE
MAJOR COASTAL RIVER DRAINAGES. VFR ELSEWHERE. COASTAL AREAS
EXPECTED TO REMAIN MVFR THROUGH AT LEAST EARLY AFTERNOON...THEN GO
TO A MIX OF MVFR TO LOW-END VFR. INLAND AREAS WILL CONTINUE WITH
VFR BUT WITH PLENTY OF MID-LEVEL CLOUDS IN SOUTH FLOW ALOFT.
AFTERNOON HEATING TUE WILL LEAD TO A THREAT OF SHOWERS...PRIMARILY
ALONG THE CASCADES. MODELS SUGGEST MUCH DEEPER MARINE CLOUD
PENETRATION INLAND AFTER 06Z WED.

KPDX AND APPROACHES...VFR CONDITIONS THROUGH AT LEAST 07Z WED.
PLENTY OF MID AND HIGH LEVEL CLOUDS THROUGH TUE EVENING WITH A
SLIM THREAT OF SHOWERS TUE AFTERNOON AND EVENING IN THE VICINITY.
MVFR CIGS COULD UP THE COLUMBIA RIVER TO NEAR KPDX 07Z TO 12Z WED.
WEISHAAR

&&

.MARINE...SOUTH WIND REVERSAL ALONG THE COAST EARLY THIS
MORNING...BUT MAX GUSTS HAVE BEEN UNDER 20 KT. NW TO N WIND
PATTERN RETURNS THIS AFTERNOON AND WILL BE THE DOMINANT FEATURE
OVER THE NEXT SEVERAL DAYS. LATEST MODELS IN GOOD AGREEMENT
SHOWING 20 TO 25 KT SUSTAINED SPEEDS DEVELOPING OVER THE OUTER
WATERS BY LATE THIS AFTERNOON AND CONTINUING THROUGH AT LEAST THU.
WILL GO WITH A SMALL CRAFT ADVISORY FOR WIND IN THE OUTER WATERS
BEGINNING 00Z WED. INNER WATERS WILL SEE 25 KT WIND GUSTS BEGIN A
LITTLE LATER. THUS...STARTED THE SMALL CRAFT ADVISORY THERE AT 06Z
WED. OUTER WATERS COULD SEE SMALL CRAFT ADVISORY WIND GUSTS
THROUGH THE WEEKEND.

SEAS HAVE NUDGED DOWN A BIT SINCE EARLIER THIS EVENING...GENERALLY
6 TO 7 FT. LATEST SPECTRAL GUIDANCE SUGGEST SEAS TO BECOME WIND-
WAVE DOMINATED EARLY TUE EVENING AND CONTINUE FOR THE NEXT FEW
DAYS. OUTER WATERS LIKELY TO SEE WIND WAVES UP TO 6 FT...WITH A
LONGER-PERIOD SWELL COMPONENT OF 2-4 FT. SEAS WILL BECOME QUITE
CHOPPY AND THERE IS THE POTENTIAL FOR SQUARE SEAS LATE THIS WEEK.
WEISHAAR

&&

.PQR WATCHES/WARNINGS/ADVISORIES...
OR...NONE.
WA...NONE.
PZ...SMALL CRAFT ADVISORY FOR WINDS FROM 5 PM THIS AFTERNOON TO 7 PM
     PDT WEDNESDAY FOR WATERS FROM CAPE SHOALWATER WA TO
     FLORENCE OR FROM 10 TO 60 NM.

     SMALL CRAFT ADVISORY FOR WINDS FROM 11 PM THIS EVENING TO 7 PM
     PDT WEDNESDAY FOR COASTAL WATERS FROM CAPE SHOALWATER WA
     TO FLORENCE OR OUT 10 NM.

     SMALL CRAFT ADVISORY FOR ROUGH COLUMBIA RIVER BAR UNTIL 4 AM
     PDT EARLY THIS MORNING.

&&

$$

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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