Area Forecast Discussion
Issued by NWS Portland, OR

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FXUS66 KPQR 301051
AFDPQR

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE PORTLAND OR
236 AM PST FRI JAN 30 2015

.SYNOPSIS..BUILDING HIGH PRESSURE AND OFFSHORE FLOW SHOULD PRODUCE
RELATIVELY MILD TEMPERATURES...AREAS OF VALLEY FOG AND EAST WINDS
NEAR THE MOUTH OF THE COLUMBIA RIVER GORGE THROUGH SATURDAY NIGHT. A
WEAKENING STORM SYSTEM WILL LIKELY BRING A SHOT OF RAIN TO THE AREA
SUNDAY AFTERNOON AND EVENING. ANOTHER SHOT OF RAIN APPEARS LIKELY ON
MONDAY. ADDITIONAL ROUNDS OF RAIN APPEAR POSSIBLE DURING THE
MIDDLE OF NEXT WEEK...BUT CONFIDENCE IN THE DETAILS IS LOW. A WETTER
STORM SYSTEM APPEARS POSSIBLE LATE NEXT WEEK. SIGNIFICANT SNOWS AT
CASCADE PASS LEVEL APPEAR UNLIKELY DURING THE NEXT WEEK.

&&

.SHORT TERM...TODAY THROUGH MONDAY...FOG PRODUCT AND SURFACE
OBSERVATIONS INDICATE FOG HAS DEVELOPED ALONG THE EASTERN PORTIONS OF
THE CENTRAL AND SOUTHERN WILLAMETTE VALLEY AND ALONG THE LOWER
COLUMBIA RIVER VALLEY BETWEEN SCAPPOOSE AND LONGVIEW/CASTLE ROCK. A
WEAK NORTHERLY PRESSURE GRADIENT APPEARS TO BE GENERATING JUST ENOUGH
MIXING IN THE LOWER ATMOSPHERE TO PREVENT WIDESPREAD FOG FROM
DEVELOPING ACROSS THE WESTERN PORTION OF THE WILLAMETTE
VALLEY...ASIDE FROM THE HILLSBORO AREA. DO NOT EXPECT A LOT OF CHANGE
GOING FORWARD SO THE FOG COVERAGE WORDING WAS TRIMMED TO MATCH
OBSERVATIONS AND TRENDS.

A RELATIVELY DEEP COLD POOL AND ACCOMPANYING STRATUS DECK LIE EAST OF
THE CASCADES. THIS HAS RESULTED IN A 6 TO 7MB CROSS CASCADE PRESSURE
GRADIENT AND ALLOWED EAST WINDS TO BLOW NEAR THE MOUTH OF THE
COLUMBIA RIVER GORGE. EXPECT THESE WINDS TO CONTINUE THROUGH THE
WEEKEND...AND PERHAPS INCREASE A BIT SATURDAY NIGHT.

THE GFS AND EC GENERALLY AGREE THE UPPER LEVEL RIDGE OVER THE REGION
WILL FLATTEN ON SUNDAY...AND ALLOW A WEAKENING FRONT TO BRING A SHOT
OF RAIN TO THE AREA. CONTINUED THE UPWARD TREND IN POPS AND QPF AS A
RESULT. MODELS ALSO FINALLY SEEM TO BE AGREEING THAT AN ADDITIONAL
SHORTWAVE TROUGH RIDING EASTWARD IN THE WESTERLY FLOW WILL LIKELY
BRING A MORE SUBSTANTIAL ROUND OF RAIN MONDAY. SNOW LEVELS GENERALLY
LOOK TO REMAIN WELL ABOVE CASCADE PASS LEVELS DURING THIS TIME
THOUGH. /NEUMAN


.LONG TERM...MONDAY NIGHT THROUGH THURSDAY...MODELS HAVE BACKED OFF
ON THE IDEA THAT SHORTWAVE RIDGING WOULD BUILD INTO THE AREA QUICKLY
ON TUESDAY. INSTEAD...ADDITIONAL SHORTWAVE TROUGHS RIDING EASTWARD
IN THE ZONAL PATTERN MAY BRING ANOTHER ROUND OR TWO OF RAIN
MIDWEEK...BUT CONSIDERABLE DIFFERENCES IN THE EVOLUTION AND TIMING
OF THESE SYSTEMS REMAIN. AS A RESULT...POPS WERE GENERALLY KEPT IN
THE CHANCE RANGE MIDWEEK. EITHER WAY...THESE SYSTEMS LOOK TO BE
RELATIVELY WARM SO SUBSTANTIAL CASCADE SNOWS APPEAR UNLIKELY.
HOWEVER...SNOW LEVELS MAY END UP BEING A TOUCH LOWER ACROSS THE
SOUTH WASHINGTON CASCADES WHERE COLD AIR DAMMING COULD ALLOW HIGHER
SNOW TOTALS TO FALL DEPENDING ON HOW THESE SYSTEMS PLAY OUT. A MORE
SUBSTANTIAL FRONTAL STORM SYSTEM APPEARS AS THOUGH IT WILL ARRIVE
LATER IN THE WEEK. SNOW LEVELS WILL ONCE AGAIN BE RELATIVELY HIGH
WITH THIS SYSTEM AND IT APPEARS UNLIKELY TO HELP OUR PITIFUL
MOUNTAIN SNOWPACK. /NEUMAN

&&

.AVIATION...COASTAL SITES REMAIN UNDER VFR CONDITIONS DUE TO
LIGHT EASTERLY WINDS. THIS SHOULD CONTINUE THROUGH TODAY. FOG HAS
DEVELOPED OVER THE SOUTH WILLAMETTE VALLEY AND HAS LOCKED KEUG IN
WITH IFR/LIFR CIGS AND VIS FOR THE MORNING. DENSE FOG BANK IS
SETTLING IN ALONG THE EAST SIDE OF THE SOUTH AND CENTRAL
WILLAMETTE VALLEY...KEEPING KSLE VFR. IF FOG DOES FILL IN
WESTWARD...IT WILL LIKELY BE MORE PATCHY ON THIS SIDE OF THE
VALLEY. THIS MEANS IF FOG DOES DEVELOP AT KSLE...CIGS AND VIS WILL
LIKELY BOUNCE BETWEEN IFR AND MVFR BEFORE IT BURNS OFF BY 18-20Z.
FOG OVER THE NORTH WILLAMETTE VALLEY WILL AGAIN BE PATCHY AS EAST
WIND OUT OF THE GORGE KEEPS SOME AREAS CLEAR...MAINLY ON THE EAST
SITE SUCH AS KTTD...WHILE AREAS MORE PROTECTED FROM EASTERLY
WINDS DEVELOP FOG BRINGING CIGS AND VIS DOWN TO IFR/LIFR. EAST WINDS
ARE WEAKER THAN LAST NIGHT...THOUGH...AND DON`T APPEAR TO BE
MAKING TO TO KPDX. IR SATELLITE IS SHOWING SOME FOG CREEPING
EASTWARD UP THE COLUMBIA RIVER FROM KELSO...WHICH COULD BRING CIGS
AND VIS DOWN AT KPDX TO IFR/LIFR BY 12-14Z IF WINDS REMAIN CALM.

KPDX AND APPROACHES...VFR CONDITIONS CURRENTLY. IR SATELLITE IS
SHOWING SOME FOG CREEPING EASTWARD UP THE COLUMBIA RIVER FROM
KELSO...WHICH COULD BRING FOG INTO PDX AROUND 13Z. EAST WINDS
FROM THE GORGE DON`T APPEAR LIKELY TO MAKE IT TO PDX THIS
MORNING...SO CALM CONDITIONS WILL ALLOW THIS FOG TO MAKE IT TO
PDX. THIS WOULD LOWER CIGS AND VIS TO IFR/LIFR AROUND 13Z. FOG
SHOULD LIFT BY 18Z. -MCCOY

&&

.MARINE...HIGH PRESSURE OVER THE WATERS WILL PERSIST THROUGH EARLY
SATURDAY. THOUGH NORTHERLY WINDS ARE GUSTING TO 20 TO 25 KTS OVER
THE WATERS TO OUR SOUTH...NORTHERLY WINDS ACROSS OUR WATERS ARE
STAYING AROUND 10 TO 15 KTS THIS MORNING...OCCASIONALLY GUSTING
NEAR 20 MAINLY IN OUR SOUTHERN WATERS. NORTHERLY WINDS WILL
CONTINUE THROUGH SATURDAY UNTIL THE APPROACHING WEAK FRONTAL
SYSTEM VEERS WINDS TO THE EAST WITH ITS APPROACH SATURDAY
AFTERNOON. WINDS CONTINUE TO VEER TO SOUTHERLY BY SUNDAY
MORNING AND INCREASE THROUGH THE DAY. SOUTHERLY WINDS WITH THIS
WEAK FRONTAL SYSTEM ON SUNDAY LOOK TO PEAK AROUND 15 KTS WITH
GUSTS JUST BELOW 20 KTS. THE STRONGEST WINDS WILL BE OVER THE
NORTHERN WATERS. WINDS WEAKEN BEHIND THE FRONT SUNDAY NIGHT BEFORE
ANOTHER FRONT APPROACHES LATE SUNDAY NIGHT/EARLY MONDAY. WINDS
LOOK TO INCREASE TO JUST BELOW SMALL CRAFT ADVISORY CRITERIA
AS THIS SECOND FRONT MOVES THROUGH MONDAY MORNING. POST-FRONT
WESTERLIES WILL STAY UP AROUND 10 TO 15 KTS GUSTING NEAR 20 KTS
THROUGH MONDAY AFTERNOON...STARTING TO DROP BACK DOWN TO 5 TO 10
KTS BY TUESDAY MORNING.

SEAS ARE CURRENTLY AROUND 6 TO 7 FT AND FALLING. SEAS COULD DROP
AS LOW AS 4 FT BEFORE THE FIRST FRONTAL SYSTEM BRINGS SEAS BACK
UP TO AROUND 6-7 FT EARLY SUNDAY. SEAS REMAIN AROUND 6-7 FT
THROUGH SUNDAY AFTERNOON...BUT BUILD TO NEAR 10 FT BY EARLY
MONDAY. SEAS LOOK TO STAY AROUND 10 FT WITH THE SECOND FRONTAL
PASSAGE THROUGH MONDAY AFTERNOON...FINALLY DROPPING BACK BELOW 10
FT BY TUESDAY. -MCCOY

&&

.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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