Area Forecast Discussion
Issued by NWS Portland, OR

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FXUS66 KPQR 161613
AFDPQR

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE PORTLAND OR
900 AM PDT TUE SEP 16 2014

.SYNOPSIS...A LOW PRESSURE SYSTEM CURRENTLY WELL OFF THE OREGON COAST
WILL MOVE TOWARDS SOUTHERN OREGON AND BRING A CHANCE FOR SHOWERS LATE
WEDNESDAY INTO THURSDAY ACROSS NORTHWEST OREGON AND SOUTHWEST
WASHINGTON. ONSHORE FLOW SHOULD KEEP MOST OF THE SMOKE FROM THE 36
PIT FIRE OVER THE CASCADES AND POINTS EAST. HOWEVER...HIGH PRESSURE
LOOKS INCREASINGLY LIKELY TO BUILD OVER THE REGION TOWARDS THE
WEEKEND SO EXPECT TEMPERATURES TO POSSIBLY APPROACH 90F AGAIN FOR
INTERIOR VALLEYS.

&&

.UPDATE...SATELLITE IMAGERY AND RADAR SHOWS A BAND OF HIGH BASED
SHOWERS LIFTING NORTHWARD ACROSS THE PUGET SOUND. THIN HIGH LEVEL
CLOUDS CONTINUE TO STREAM NORTHEASTWARD ACROSS THE AREA. UNDERNEATH
THESE CLOUDS...IT IS APPARENT THAT MARINE STRATUS HAS PUSHED INTO THE
COASTAL GAPS...MAKING IT INTO KELSO/LONGVIEW AND SCAPPOOSE...WHERE
IT APPEARS THEY WILL STALL OUT. ALTHOUGH...A FEW CLOUDS MAY SNEAK
INTO THE PORTLAND METRO FOR AN HOUR OR TWO THIS MORNING.

BACKING LOW LEVEL FLOW AHEAD OF THE NEXT STORM SYSTEM HAS RESULTED
IN MARINE CLOUDS ALREADY THINNING ALONG THE CENTRAL OREGON COAST.
EVEN THOUGH MARINE STRATUS BRIEFLY MADE IT INTO EUGENE...CORVALLIS
AND SALEM EARLIER THIS MORNING...THE MOISTURE SOURCE FOR THESE
CLOUDS HAS BEEN PINCHED OFF...AND ANY REMAINING LOW CLOUDS IN THE
SOUTHERN WILLAMETTE VALLEY WILL DISSIPATE QUICKLY. THE NET RESULT IS
THAT SKY COVER WAS LOWERED CONSIDERABLY FOR MUCH OF THE
WILLAMETTE VALLEY AND CASCADES TODAY.

AS THE EAST SIDE HEATS UP THIS AFTERNOON...MODEST SOUTHWEST TO
WESTERLY WINDS SHOULD KICK UP. THIS SHOULD CONTINUE TO BLOW MOST OF
THE SMOKE AND HAZE FROM THE 36 PIT FIRE INTO THE CASCADES AND
CENTRAL COLUMBIA RIVER GORGE AND POINTS EAST...AND PROVIDE SOME
RELIEF FOR THE WILLAMETTE VALLEY.

A SPLITTY TROUGH IS STILL ON TRACK TO MOVE THROUGH THE REGION LATE
WEDNESDAY INTO THURSDAY. MODELS CONTINUE TO SUGGEST A GOOD PORTION OF
THE FORECAST AREA WILL SEE SOME RAIN DURING THIS PERIOD. CONTINUE TO
THINK THAT MUCH OF THE HEAVIER PRECIPITATION IS OVERDONE...BUT WILL
EVALUATE FURTHER WITH THE AFTERNOON FORECAST PACKAGE. /NEUMAN


.LONG TERM...THURSDAY NIGHT THROUGH MONDAY. AN UPPER RIDGE BEGINS TO
BUILD AGAIN OVER THE NORTHEAST PACIFIC AND CAUSES THE NEXT SYSTEM TO
MOSTLY FALL APART AS IT APPROACHES THE PACIFIC NORTHWEST FRIDAY...
ALLOWING TEMPS TO BEGIN TO RECOVER FROM THE EXPECTED VALUES
THURSDAY. THE MODELS ARE IN EXCELLENT AGREEMENT THAT THE UPPER RIDGE
WILL THEN MOVE INTO THE PACIFIC NORTHWEST IN EARNEST OVER THE
WEEKEND...WITH ANOTHER THERMAL TROUGH BUILDING UP THE COAST FOR MORE
SUBSTANTIAL WARMING. TEMPS INLAND WILL HAVE ANOTHER CHANCE OF
APPROACHING 90 AGAIN INLAND. WE MAY SEE SOME MODERATION AGAIN EARLY
NEXT WEEK AS THE FLOW ALOFT TURNS SOUTHWESTERLY AND ALLOWS ONSHORE
FLOW TO DEVELOP...BUT ANY CHANCE OF PRECIPITATION MAY HOLD OFF UNTIL
THE MIDDLE OR LATTER PART OF NEXT WEEK AT THE EARLIEST. TOLLESON

&&

.AVIATION...AN UPPER LEVEL TROUGH OFFSHORE IS SENDING HIGH CLOUDS
OVER THE REGION TODAY. THESE CLOUDS ARE MAKING IT DIFFICULT TO
EVALUATE THE EXTENT OF THE LOWER CLOUDS IN SATELLITE IMAGERY.
SURFACE OBSERVATIONS SUGGEST THAT THERE IS MARINE STRATUS ALONG
THE NORTH COAST WITH MVFR CIGS KTMK AND NORTHWARD. THERE WERE MVFR
CIGS BRIEFLY IN THE SOUTHERN WILLAMETTE VALLEY...BUT THEY ARE
ALREADY CLEARING. BREAKS IN THE HIGH CLOUDS SHOWS THAT STRATUS
ALONG THE COLUMBIA RIVER VALLEY HAS MADE IT KSPB...BUT IS STARTING
TO RETREAT BACK TO THE COAST. MVFR CIGS SHOULD CLEAR LATER THIS
MORNING WITH WIDESPREAD VFR CONDITIONS THIS AFTERNOON AND EVENING.

MARINE STRATUS WITH MVFR CIGS ARE EXPECTED ALONG THE IMMEDIATE
COAST LATE THIS AFTERNOON AROUND 0Z. ONSHORE WINDS ACROSS CENTRAL
OREGON COAST WILL BRING SOME CLOUDS THROUGH THE COASTAL GAPS NEAR
KONP...OTHERWISE LIGHT SOUTH TO SOUTHEAST WINDS SHOULD PREVENT THE
CLOUDS TO MOVE MUCH INLAND. WOULD NOT BE SURPRISED IF THE MARINE
CLOUDS ACTUALLY PUSH AWAY FROM THE COAST EARLY WED MORNING. THERE
MAY BE A BRIEF PERIOD OF LOW MVFR FOR THE SOUTHERN WILLAMETTE
VALLEY INCLUDING KEUG AROUND 09Z...BUT FORECAST CONFIDENCE IS LOW
FOR KEUG CIGS.

KPDX AND APPROACHES...VFR TODAY AND TONIGHT WITH A MIX OF HIGH
CLOUDS. LIGHT WEST WINDS SHOULD DEVELOP BY 20Z...THEN VERY LIGHT
SOUTHEAST WINDS EXPECTED AFTER 8Z. TJ

&&

.MARINE...FAIRLY BENIGN CONDITIONS PERSIST OVER THE WATERS FOR THE
NEXT FEW DAYS. WEAK LOW PRES OVER THE NE PAC WILL MAINTAIN A S TO
SW WIND FOR NEXT SEVERAL DAYS...BUT GENERALLY 15 KT OR LESS. THERE
WILL BE A MIX OF WAVE TRAINS WITH VARYING PERIODS...OUT OF THE NW
W AND SW. EXPECT OVERALL WAVE HEIGHTS TO GRADUALLY BUILD
TODAY AND REMAIN IN THE 5 TO 7 FT RANGE TONIGHT THROUGH THU.

HIGH PRES WILL REBUILD OVER THE WATERS FRI AND SAT...WITH ANOTHER
THERMAL LOW PRES OVER NW CALIF. THIS WILL BRING ANOTHER ROUND OF
N WINDS TO THE WATERS...POSSIBLY REACHING NEAR SMALL CRAFT
ADVISORY LEVELS AT TIMES. PYLE/TJ

&&

.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 AS THE FORECAST AREA.



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