Area Forecast Discussion
Issued by NWS Portland, OR

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FXUS66 KPQR 272209
AFDPQR

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE PORTLAND OR
209 PM PST TUE JAN 27 2015

.SYNOPSIS...A WEAK FRONTAL SYSTEM ALONG THE COAST WILL SLOWLY MOVE
INLAND MAINLY OVER THE NORTH PART OF THE FORECAST AREA TONIGHT AND
WEDNESDAY...LINGER INTO WEDNESDAY NIGHT...THEN MOSTLY DISSIPATE AND
MOVE OUT OF THE AREA THURSDAY. ANOTHER UPPER RIDGE IS EXPECTED TO
DEVELOP OVER THE PACIFIC NORTHWEST LATER IN THE WEEK AND CONTINUE
INTO THE WEEKEND FOR MORE DRY WEATHER. THE NEXT CHANCE FOR RAIN IS
PROBABLY NOT UNTIL NEXT SUNDAY AND MONDAY.
&&

.SHORT TERM...TONIGHT THROUGH FRIDAY...A WEAK SYSTEM HAS SPREAD A
LITTLE LIGHT PRECIPITATION TO THE COAST TODAY. THE SALEM SOUNDING
THIS MORNING SHOWS THAT THE MARINE LAYER AND INVERSION HAS RISEN DUE
TO THE CHANGE TO A LIGHT ONSHORE FLOW. THERE IS STILL A LOT OF LOW
STRATUS AROUND WITH CEILINGS AROUND 500 TO 1000 FEET AND ANOTHER DECK
ABOVE WITH CEILINGS BETWEEN 2000 AND 3000 FEET.

THE SOUTHWESTERLY UPPER FLOW ASSOCIATED WITH THE WEAK SYSTEM ALONG
OUR COAST HAS SPREAD SOME CLOUDS NORTH ACROSS OREGON FROM AN UPPER
LOW IN CALIFORNIA AND THE GREAT BASIN. THIS STREAM OF DIFFUSE LESS
ORGANIZED MOISTURE WILL CONTINUE TO RIDE ACROSS THE AREA TODAY AND
TONIGHT. THIS COULD FEED A BIT OF MOISTURE INTO OUR WEAK FRONTAL BAND
ALONG THE COAST THAT IS FORECAST TO SLOWLY SPREAD INLAND MAINLY IN
THE NORTH THROUGH TONIGHT. THE MODELS CONTINUE TO SHOW SOME LIGHT
PRECIPITATION FOCUSED ALONG THIS FRONTAL BAND INTO WEDNESDAY NIGHT
BEFORE DRYING OUT AND LIFTING NORTH THURSDAY. THE WEAK ASSOCIATED
UPPER TROUGH TAKES UNTIL THURSDAY AND THURSDAY NIGHT BEFORE IT MOVES
OUT OF THE AREA...SO THIS STILL SEEMS REASONABLE. SO OVERALL WE
SHOULD SEE PLENTY OF CLOUDS THE NEXT COUPLE OF DAYS WITH LESS FOG
COVERAGE...EXCEPT PERHAPS IN THE SOUTH WILLAMETTE VALLEY.

THE GRADIENTS ARE PRETTY WEAK FROM THE NORTH THURSDAY...SO THEY MAY
NOT BE ENOUGH TO BREAK UP THE LOW CLOUDS MUCH THURSDAY AFTERNOON. THE
ONE EXCEPTION MIGHT BE NEAR TROUTDALE...AS WE START TO GET ABOUT A 4
MB EASTERLY GRADIENT THROUGH THE GORGE BY THURSDAY AFTERNOON.

AN UPPER RIDGE BUILDS IN THURSDAY NIGHT AND FRIDAY...BUT THE MAIN
IMPACT WILL BE TO MAINTAIN OR SLIGHTLY STRENGTHEN OUR TEMPERATURE
INVERSION SOME...THOUGH NOT NEARLY AS STRONG WHAT WE SAW LAST
WEEKEND. SHOULD SEE MORE FOG COVERAGE FRIDAY MORNING. THE LIGHT
EASTERLY GRADIENT THROUGH THE GORGE CONTINUES...AND WE DO GET A LIGHT
NORTHERLY GRADIENT SOUTHWARD ALONG THE WILLAMETTE VALLEY...SO WE WILL
HAVE TO SEE IF THIS IS ENOUGH TO BREAK UP THE LOW CLOUDS AND FOG SOME
FRIDAY AFTERNOON. TOLLESON

.LONG TERM...FRIDAY NIGHT THROUGH TUESDAY...THE UPPER RIDGE CONTINUES
THROUGH SATURDAY OFF THE PACNW COAST AS A HIGH AMPLITUDE PATTERN IN
THE NORTH PACIFIC CONTINUES. THIS WILL MEAN DRY WEATHER WITH FOG IN
THE INTERIOR VALLEYS WHILE THE MOUNTAINS WILL BE MILD NEARLY CLOUD
FREE.  MODELS ARE CONTINUE TO SHOW THE RIDGE SHIFTING INLAND AS A
MORE CONSOLIDATED JETSTREAM APPROACHES THE WEST COAST. ECMWF...GFS
AND GFS ENSEMBLE MEAN ARE IN GOOD AGREEMENT IN BRINGING A WARM FRONT
THROUGH THE AREA LATE SUNDAY INTO MONDAY. THE ECMWF FLATTENS THE
RIDGE MORE SO SNOW LEVELS WILL BE LOWER BUT STILL ABOVE MOST CASCADE
PASSES. WITH THE WEAKER RIDGE AND STRONGER JET STREAM POINTED INTO
THE REGION WE CAN EXPECT MORE CLOUDS AND HIGHER CHANCES FOR RAIN FOR
THE REMAINDER OF THE LONG TERM.  OVERALL HAVE INCREASED POPS SUN
NIGHT THROUGH TUE WITH EMPHASIS ON SUN NIGHT AND MONDAY.  THERE MAY
BE ANOTHER FRONT TUE BUT MODEL SOLUTIONS DIVERGE REGARDING THIS
FEATURE. /26
&&

.AVIATION...WIDE RANGE OF FLIGHT CONDITIONS ACROSS THE REGION TODAY
AS A WEAK FRONTAL BOUNDARY HAS STALLED ALONG LINE FROM EAST OF KAST
TO THE SW OFFSHORE. S FLOW HAS LIFTED KONP AND KEUG TO VFR WITH CIGS
AROUND 3500 FT...WHILE LIGHT E WINDS MAINTAIN MVFR CIGS AT KTTD AND
KPDX. MEANWHILE...IFR/LIFR FOG REMAINS AT KHIO AND KSLE...AND KAST
WHICH IS BEHIND THE BOUNDARY. EXPECT THINGS TO GENERALLY PERSIST INTO
TONIGHT...WITH PERHAPS SLIGHT IMPROVEMENT IN SOME SPOTS FOR THE NEXT
FEW HOURS. THE LOWER ATMOSPHERE WILL STABILIZE A BIT TONIGHT... AND
WEAK FLOW COUPLED WITH CONTINUED MOISTURE FROM LIGHT DRIZZLE SHOULD
PROVIDE FOR SOME LOWERING TO LOWER MVFR OR IFR ACROSS THE INTERIOR.
THE CENTRAL AND SOUTH VALLEY...ALONG WITH KHIO...MAY SEE SOME
LOCALIZED AREAS OF FOG FORM AGAIN...BUT EXPECT THIS TO BE LESS
PREVALENT IN THE NORTH WITH INCREASED MIXING FROM AN UPPER LEVEL
BOUNDARY. GENERAL TREND OF IMPROVING CIGS TO 3000 FT OR ABOVE
EXPECTED ON WEDNESDAY FROM 20Z ONWARD.

KPDX AND APPROACHES...CIGS HAVE LIFTED TO NEAR 3000 FT THIS
AFTERNOON. EXPECT OVC SKIES TO REMAIN WITH A BRIEF TRANSITION TO VFR
CIGS POSSIBLE. SOME LOWERING AGAIN AFT 03Z TO AROUND 1500 FT...WITH A
SMALL POTENTIAL FOR IFR CONDITIONS TO DEVELOP AND SOME LIGHT DRIZZLE
THROUGH THE OVERNIGHT. GIVEN LOWER CONFIDENCE IN IFR
DEVELOPING...WITH HANDLE WITH A TEMPO GROUP. GUIDANCE SUGGESTS CIGS
MAY SETTLE IN MVFR RANGE 15Z-18Z WED BEFORE LIFTING TOWARDS AND INTO
VFR THEREAFTER. CULLEN
&&

.MARINE...WINDS REMAIN 15 KT OR LESS OVER THE WATERS TODAY AND
TONIGHT. A WEAK LOW PRES DRIFTS NORTHEAST NEAR THE OUTER WATERS ON
WED AND WILL SHIFT WINDS BUT THEY REMAIN LIGHT. THEN...HIGH PRES
REBUILDS OVER THE WATERS THU AND HOLDS THROUGH THE END OF THE WEEK. N
WINDS MAY INCREASE LATE THU AND FRI AS LOW PRES BUILDS UP THE S
OREGON COAST...WITH A CHANCE OF GUSTS APPROACHING SMALL CRAFT
ADVISORY CRITERIA OVER THE CENTRAL OREGON WATERS. OTHERWISE...N WINDS
CONTINUE OVER THE WATERS THROUGH SUNDAY WHEN WINDS TURN S AHEAD OF A
STRONGER FRONTAL SYSTEM.

SEAS REMAIN NEAR 6 FT THIS EVENING AND WILL HOLD BETWEEN 5 FT AND 7
FT THROUGH THE END OF THE WEEK. A MIX OF TWO W SWELLS...ONE AROUND 18
SECONDS AND ANOTHER AROUND 11 SECONDS...WILL ENTER THE WATERS WED
NIGHT THROUGH THU NIGHT. OTHERWISE...NO CONCERNS ON THE WATERS UNTIL
SUN WHEN SEAS MAY BUILD TO NEAR 9 OR 10 FT WITH THE FRONTAL SYSTEM.
CULLEN
&&

.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.



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