Area Forecast Discussion
Issued by NWS Portland, OR

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FXUS66 KPQR 020421
AFDPQR

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE PORTLAND OR
921 PM PDT MON SEP  1 2014

.SYNOPSIS...MARINE STRATUS IS FORMING IN NW FLOW ALONG THE COAST THIS
EVENING SHOULD SOLIDIFY OVER THE NEXT FEW HOURS AND PUSH PARTIALLY
INLAND OVERNIGHT. AN UPPER LEVEL TROUGH WILL MOVE ACROSS THE REGION
TUESDAY INTO EARLY WEDNESDAY BRINING COOLER AND CLOUDY WEATHER. THIS
SYSTEM MAY ALSO BRING SOME LIGHT RAIN TO SOUTHWEST WASHINGTON AND THE
FAR NORTHERN PART OF NORTHWEST OREGON TUESDAY AFTERNOON AND TUESDAY
NIGHT. AN UPPER LEVEL RIDGE COMBINED WITH LOW-LEVEL EASTERLY WINDS
WILL RESULT IN SUNNIER AND WARMER WEATHER FOR THE LATTER PART OF THE
WEEK. ONSHORE FLOW WILL RETURN NEXT SUNDAY.

&&

.SHORT TERM...TONIGHT THROUGH THURSDAY...CLOUDS CLEARED FOR MOST
EVERYONE DURING THE LATE AFTERNOON AND EARLY EVENING HOURS.
HOWEVER...THE LATEST OBSERVATIONS AND SATELLITE FOG PRODUCT ARE
SHOWING MARINE STRATUS BEGINNING TO REFORM ALONG THE COAST IN NW
FLOW. EXPECT THE MARINE CLOUDS TO CONTINUE TO SOLIDIFY OVER THE NEXT
FEW HOURS...THEN PUSH AT LEAST PARTIALLY INLAND OVERNIGHT INTO
TOMORROW MORNING. THERE IS BETTER ONSHORE GRADIENT AT CURRENT THAN WE
SAW 24 HRS AGO...SO THINK THE CLOUDS WILL AT LEAST FILL IN THE LOWER
COLUMBIA BASIN UP TO THE PORTLAND/VANCOUVER METRO AREA. LESS CLEAR IS
WHETHER CLOUDS WILL FILL THE ENTIRE WILLAMETTE VALLEY. IT IS POSSIBLE
THAT THE CLOUDS WILL GET ENOUGH EXTRA PUSH FROM AN INCOMING UPPER
LEVEL TROUGH AFTER SUNRISE TOMORROW.

THE AFOREMENTIONED UPPER TROUGH WILL DIVE SOUTH FROM BRITISH COLUMBIA
INTO WASHINGTON DURING THE DAY TOMORROW. A WEAK ASSOCIATED FRONT WILL
MOVE ACROSS THE NORTHERN PART OF THE REGION IN THE AFTERNOON AND
EVENING.  THE FRONT MAY PRODUCE SOME LIGHT RAIN ALONG THE NORTH
COAST/COAST RANGE AND PART OF THE INLAND AREA. BEST CHANCES OF
MEASURABLE RAIN WILL BE IN SOUTHWEST WA...BUT THE NORTHERN WILLAMETTE
VALLEY AND ADJACENT FOOTHILLS AND NORTH CASCADES WILL BE ON THE
SOUTHERN END OF THE FRONT AND COULD GET A LITTLE RAIN AS WELL.THERE
WILL BE ANOTHER DEEP MARINE PUSH TOMORROW NIGHT WITH A CLOUDY START
TO THE DAY ON WEDNESDAY. THE UPPER TROUGH AND INCREASE IN CLOUDS WILL
KEEP THE TEMPERATURES BELOW NORMAL TUESDAY AND WEDNESDAY.

HIGH PRESSURE WILL REBUILD OVER THE REGION THURSDAY. A FAIRLY STRONG
THERMAL TROUGH WILL ALSO BUILD NORTHWARD ALONG THE COAST. THIS WILL
RESULT IN OFFSHORE FLOW...CLEAR SKIES...AND WARMER TEMPERATURES
THE LATTER PART OF THE WORK WEEK. PYLE/TW

.LONG TERM...FRIDAY THROUGH MONDAY...A WEAK...POSITIVELY-TILTED
TROUGH WILL MOVE THROUGH OUR AREA LATE THIS WEEK.  NOT ONLY IS
MOISTURE LIMITED FOR THE PASSAGE OF THIS SYSTEM...BUT ANY
PRECIPITATION THAT DOES DEVELOP SHOULD BE EAST OF THE CASCADE
RIDGE...OUTSIDE OF OUR AREA.  LATE THIS WEEKEND THE
GFS...ECMWF...AND DGEX ALL ARE SUGGESTING A LONGWAVE TROUGH WILL
MOVE ONSHORE BRINGING A CHANCE FOR SOME RAINFALL SUNDAY NIGHT OR
MONDAY. DISAGREEMENT BETWEEN MODELS ON TIMING AND BECAUSE OF HOW FAR
OUT THIS SYSTEM IS IN THE FORECAST PERIOD...THERE IS A LOT OF
UNCERTAINTY WITH THIS SYSTEM. KEPT POPS THE SAME AS THEY CAPTURE
THIS UNCERTAINTY WELL. -MCCOY
&&

.AVIATION...HIGH PRESSURE WILL BUILD IN OVERNIGHT ALLOWING THE
MARINE INVERSION TO LOWER SOME ACROSS THE AREA. CLOUDS CLEARED ALL
BUT THE NORTH COAST THIS AFTERNOON AND EXPECT STRATUS TO DEVELOP
ALONG THE SOUTH WASHINGTON AND NORTH OREGON COAST BEFORE MIDNIGHT
WITH MOSTLY MVFR CIGS BUT THIS DECK COULD LOWER TO IFR 11Z-16Z.
FROM FLORENCE TO KONP EXPECT MORE IFR LOW CIGS AND VIS TO DEVELOP
AFT 06Z...CAN ALREADY SEE SOME FOG OR LOW CLOUDS OFF THE COAST IN
THE SATELLITE IMAGERY. MODELS INDICATE THAT MVFR STRATUS WILL
MOVE DOWN THE COLUMBIA RIVER GAP INTO KSPB-KTTD AFTER 10Z OR SO
AND PROBABLY TO KSLE 13-19Z. MODELS INDICATE THAT A WEEK FRONT
WILL PUSH DOWN THE COAST LATE TUE AFTERNOON AND SPREAD SOME LIGHT
RAIN TO THE NORTH COAST AND NORTH INLAND TUESDAY EVENING WITH SOME
MVFR CIGS MAINLY ALONG THE COAST. SCHNEIDER


KPDX AND APPROACHES...VFR CONDITIONS THIS EVENING. STRATUS
DEVELOPING AFTER AROUND 10Z WITH MVFR CIGS LIKELY THROUGH 19-20Z.
. SOME VFR CIGS AND POSSIBLY A SHOWER ARE 01-06Z WEDNESDAY.
SCHNEIDER

&&

.MARINE...MARINE WINDS HAVE BEEN A LITTLE LIGHTER THAN PREVIOUSLY
ANTICIPATED AND HAVE LOWERED THE SMALL CRAFT ADVISORY FOR THE
CENTRAL COASTAL WATERS OF OREGON. HIGH PRESSURE WILL REBUILD
OVERNIGHT AND TOMORROW MORNING BUT A WEAK FRONT WILL APPROACH THE
NORTHERN WATERS TUE AFTERNOON RESULTING IN MORE WESTERLY WINDS
BRIEFLY UNTIL THE FRONT PASSES TUESDAY EVENING AND HIGH PRESSURE
BEGINS TO BUILD...WITH THE MAIN EFFECT BEING SOME MODERATE NW
WINDS BEHIND THE FRONT THAT MAY GIVE SOME GUSTS ABOVE 20 KT
ESPECIALLY
IN THE OUTER WATERS. THE THERMAL TROUGH BEGINS REDEVELOPING IN
NORTHERN CALIFORNIA WEDNESDAY...WITH SMALL CRAFT ADVISORY
THRESHOLD NORTHERLY WINDS BEGINNING TO SPREAD NORTH ALONG THE
CENTRAL OREGON COAST LATE WEDNESDAY. THE WINDS WILL THEN SPREAD
NORTHWARD THROUGH ALL THE WATERS THURSDAY AND FRIDAY AS THE
THERMAL TROUGH CONTINUES TO BUILDS FARTHER NORTH ALONG THE COAST.
WINDS THURSDAY AFTERNOON AND EVENING WILL BE ON THE HIGH SIDE OF
THE SMALL CRAFT ADVISORY RANGE.

SEAS REMAIN FAIRLY LOW...3 TO 5FT TONIGHT AND TUESDAY... BUT SEAS
MAY GET CLOSE TO 10 FT IN THE NORTHERN WATERS FROM THE
NORTHWESTERLIES WEDNESDAY...AND POSSIBLY AGAIN AROUND 8 TO 10 FT
LATE THURSDAY AND THURSDAY NIGHT FROM THE NORTHERLIES DUE TO THE
NORTHWARD BUILDING THERMAL TROUGH. PT

&&

.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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