Area Forecast Discussion
Issued by NWS Portland, OR

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FXUS66 KPQR 050935
AFDPQR

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE PORTLAND OR
235 AM PDT SAT SEP  5 2015

.SYNOPSIS...AN UPPER LEVEL TROUGH WILL MOVE EAST OF THE CASCADES
TODAY WITH SHOWERS OVER THE CASCADES GRADUALLY ENDING. A WEAK FRONT
WILL BRING SOME LIGHT RAIN TO THE COAST OVERNIGHT SATURDAY...AND
POSSIBLY NORTHERN INLAND AREAS SUNDAY AFTERNOON. DRY WEATHER IS
EXPECTED FOR LABOR DAY. ANOTHER WEAK FRONT MAY BRING LIGHT RAIN TO
AREAS NORTH OF THE OREGON/WASHINGTON BORDER TUESDAY MORNING. AN UPPER
LEVEL RIDGE SHOULD KEEP THE NEXT APPROACHING FRONTS NORTH OF THE AREA
AND EXPECT DRY WEATHER WITH WARMING TEMPERATURES THROUGH THE REST OF
THE WEEK.

&&

.SHORT TERM...TODAY THROUGH TUESDAY...AN UPPER LEVEL TROUGH IS OVER
NW OREGON GENERATING ISOLATED SHOWERS FOR THE OREGON CASCADES EARLY
THIS MORNING...AND COOL TEMPERATURES FOR THE PORTLAND FORECAST AREA.
THE UPPER TROUGH WILL SHIFT EAST OF THE CASCADES LATER THIS MORNING
ENDING THE THREAT FOR SHOWERS. TEMPERATURES FOR THE INTERIOR LOW
LANDS SHOULD WARM INTO THE LOW 70S THIS AFTERNOON WITH TEMPS PEAKING
IN THE MID 60S FOR THE COAST. HIGH CLOUDS AHEAD OF AN APPROACHING
FRONT WILL BEGIN TO MOVE OVER THE AREA LATE TONIGHT. THESE CLOUDS
SHOULD REDUCE RADIATION COOLING AND THE TEMPERATURES FOR THE COASTAL
VALLEYS AND THE WILLAMETTE VALLEY EARLY SUNDAY MORNING SHOULD NOT BE
AS COOL AS THEY ARE THIS MORNING.

AN UPPER LEVEL SHORTWAVE TROUGH CURRENTLY OVER THE GULF OF ALASKA
WILL DROP SOUTH ALONG THE ALASKAN COAST TONIGHT BEFORE MOVING INLAND
ACROSS SOUTHERN WASHINGTON SUNDAY. THIS TROUGH IS PAIRED WITH A
SURFACE FRONT THAT WILL BRING LIGHT RAIN TO THE SW WASHINGTON AND NW
COAST SUNDAY MORNING...AND LIKELY DOWN TO THE CENTRAL OREGON COAST.
THE FRONT WILL MOVE INLAND SUNDAY AFTERNOON...BUT DROP MOST OF ITS
RAIN NEAR THE COAST...WITH HARDLY ANY RAIN EXPECTED EAST OF THE COAST
RANGE.

 PRECIPITABLE WATER WILL BE OVER AN INCH WITH THIS FRONT AND A 90KT
500MB JET SHOULD PROVIDE ENOUGH LIFT FOR MEASURABLE RAIN.
HOWEVER...THE MODELS ARE FORECASTING THAT THE FRONT WILL RELEASE MOST
OF ITS MOISTURE OFFSHORE...AND WEAKEN QUITE A BIT BEFORE IT REACHES
THE COAST...AND ONLY EXPECT LIGHT QPF...LESS THAN 0.10 INCH FOR THE
COAST AND COAST RANGE. THE FRONT WILL FALL APART AS IT MOVES INLAND
SUNDAY AFTERNOON AND ONLY EXPECT A FEW HUNDREDTHS OF AN INCH OF RAIN
FOR THE INTERIOR LOW LANDS NORTH OF SALEM.

CLOUDS ACROSS THE NORTH ASSOCIATED WITH THE FRONT SHOULD KEEP DAYTIME
HIGHS FOR THE INTERIOR LOWLANDS FROM REACHING MUCH ABOVE 70 DEGREES
NORTH OF SALEM SUNDAY AFTERNOON. LESS CLOUD COVER SOUTH OF SALEM
COULD RESULT IN DAYTIME HIGHS CLOSER TO 75.

UPPER LEVEL HEIGHTS WILL RISE BEHIND THE DEPARTING TROUGH SUNDAY
NIGHT RESULTING IN A DRY LABOR DAY WITH TEMPERATURES WARMING INTO THE
MID 70S FOR THE INTERIOR LOW LANDS. CLOUDS WILL INCREASE NORTH OF
SALEM LATE MONDAY AFTERNOON AS A FRONT APPROACHES NW WASHINGTON. THE
UPPER RIDGE SHOULD KEEP RAIN ASSOCIATED WITH THIS FRONT NORTH OF THE
PORTLAND FORECAST AREA. HOWEVER...THINK LIGHT RAIN IS POSSIBLE JUST
NORTH OF THE OR/WA BORDER TUESDAY AFTERNOON. TJ

.LONG TERM...TUESDAY NIGHT THROUGH FRIDAY NIGHT. AN UPPER LEVEL RIDGE
SHOULD KEEP THE STORM TRACK NORTH OF OREGON THROUGH THE END OF THE
WORK WEEK. INTERIOR TEMPERATURES WILL WARM INTO THE 80S...AND COASTAL
TEMPERATURES INTO THE 70S BY WEDNESDAY...AND REMAIN ABOVE SEASONAL
NORMAL THROUGH THE WEEK. TJ

&&

.AVIATION...HIGH PRESSURE OVER THE NORTHEAST PACIFIC AND AN UPPER
LEVEL LOW PRESSURE MOVING EASTWARD ACROSS OREGON HAS LEFT MOST
LOWLAND LOCATIONS CLEAR EARLY THIS MORNING WITH CLOUDS HUGGING
THE CASCADES. PATCHY IFR AND MVFR CONDITIONS APPEAR LIKELY TO
DEVELOP ALONG THE COAST THROUGH APPROXIMATELY 18Z SATURDAY.
HOWEVER...ACROSS THE WILLAMETTE VALLEY...SLIGHTLY LOWER DEWPOINTS
AND HIGHER WIND SPEEDS IN THE LOWER ATMOSPHERE MAY MAKE IFR
CONDITIONS HARDER TO COME BY THIS MORNING THAN YESTERDAY. IN
ADDITION...SATELLITE TRENDS SUGGEST CLOUDS OVER THE CASCADES THAT
ARE CURRENTLY BETWEEN 4KFT AND 8KFT ARE TRYING TO BACK BUILD INTO
THE WILLAMETTE VALLEY...WHICH MAY KEEP MOST INTERIOR LOCATIONS
VFR THIS MORNING. THE BOTTOM LINE IS THAT CONFIDENCE IN THE FORECAST
IS LOW THROUGH 18Z SATURDAY...BUT SUSPECT MORE LOCATIONS MAY
REMAIN VFR THAN PREVIOUSLY THOUGHT. KEUG AND KHIO WILL BE MOST
SUSCEPTIBLE TO FLIGHT RESTRICTIONS THIS MORNING. OTHERWISE...EXPECT
MAINLY VFR CONDITIONS THROUGH 12Z SUNDAY...EXCEPT AT KAST WHERE AN
INCOMING FRONT SHOULD CAUSE CONDITIONS TO DETERIORATE INTO AT
LEAST MVFR AND POSSIBLY IFR TOWARDS 12Z SUNDAY.

KPDX AND APPROACHES...IT APPEARS INCREASINGLY LIKELY THAT CONDITIONS
WILL REMAIN PREDOMINANTLY VFR THROUGH 12Z SUNDAY AS CIGS BETWEEN
4KFT AND 8KFT BUILD WESTWARD OFF THE CASCADES AND OVER THE TERMINAL
EARLY THIS MORNING. NONETHELESS...THERE IS STILL A CHANCE CONDITIONS
COULD DETERIORATE INTO IFR THROUGH APPROXIMATELY 18Z SATURDAY...BUT
CONFIDENCE IS LOW. /NEUMAN

&&

.MARINE...EXPECT RELATIVELY BENIGN WINDS AND SEAS THROUGH EARLY
NEXT WEEK. A WEAK FRONT WILL MOVE ACROSS THE WATERS ON SUNDAY
MORNING AND LIKELY BRING A FEW HOURS OF SOUTHERLY WINDS...BUT
WIND SPEEDS SHOULD STAY UNDER 20 KT. THERMAL LOW PRESSURE THEN
LOOKS TO REDEVELOP OVER NORTHERN CALIFORNIA...BRINGING A RETURN TO
GUSTY NORTHERLY WINDS...ESPECIALLY ACROSS THE CENTRAL OREGON
WATERS NEXT WEEK. WITH THAT SAID...WINDS WILL LIKELY ONLY FLIRT
WITH SMALL CRAFT ADVISORY LEVEL GUSTS OF 20 TO 25 KT THROUGH THE
MIDDLE OF NEXT WEEK. IT APPEARS THE STRONGER AND MORE SOLID SMALL
CRAFT ADVISORY LEVEL NORTHERLY WIND GUSTS OF 25 TO 30 KT WILL
HOLD OFF UNTIL LATE IN THE WORK WEEK. /NEUMAN

&&

.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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