Area Forecast Discussion
Issued by NWS Portland, OR

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FXUS66 KPQR 301630
AFDPQR

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE PORTLAND OR
929 AM PDT SAT AUG 30 2014

.SYNOPSIS...COOLER WESTERLY FLOW ALOFT PREVAILS THROUGH THIS
WEEKEND..WITH A SERIES OF WEAK SURFACE FRONTS. THIS WILL BRING
PLENTY OF CLOUDS AND COOLER AIR TO THE REGION...ALONG WITH PERIODIC
RAIN SHOWERS. THE BEST CHANCES OF SHOWERS WILL BE THIS AFTERNOON AND
EVENING. WEAK RIDGING TRIES TO BUILD BACK INTO THE PACIFIC
MONDAY...BEFORE A DEEPER TROUGH MOVES OVER THE AREA TUESDAY THROUGH
THE END OF THE WEEK.

&&

.UPDATE...RADAR THIS MORNING SHOWS FAIRLY WIDESPREAD SHOWERS AT LEAST
NORTH OF LANE COUNTY WITH RAIN RATES OF GENERALLY A COUPLE OF
HUNDREDTHS PER HOUR WITH CLOSER TO A TENTH OF AN INCH PER HOUR IN
MORE MODERATE SHOWERS. ALL OF THIS SHOWER ACTIVITY IS AHEAD OF A WEAK
COLD FRONT WHICH CURRENTLY SITS JUST OFFSHORE. THE FRONT WILL MAKE
ITS WAY THROUGH THE FORECAST AREA THIS AFTERNOON WITH MUCH DRIER
CONDITIONS BEHIND THE FRONT AND AS SUCH...PRECIP CHANCES WILL DROP
FROM WEST TO EAST THROUGH THIS EVENING. RAISED NEAR-TERM POPS ACROSS
SW WASHINGTON AND MUCH OF THE SOUTH VALLEY TO REFLECT RECENT RADAR
TRENDS. ALSO INCREASED WINDS A BIT IN THE VALLEY BEHIND THE FRONT.
PREVIOUS DISCUSSION FOLLOWS.

.SHORT TERM...TODAY THROUGH MONDAY NIGHT...RADAR AND SURFACE
OBSERVATIONS HAVE DETECTED LIGHT RAIN SHOWERS ALONG THE NORTHERN
OREGON COAST EARLY THIS MORNING...AS AN UPPER LEVEL SHORTWAVE
TROUGH...CURRENTLY AROUND 50 MILES OFFSHORE...APPROACHES. AT THE
SURFACE...A WEAK FRONT IS APPROACHING THE WASHINGTON AND OREGON COAST
AND WILL MOVE ACROSS THE PORTLAND FORECAST AREA THIS
AFTERNOON...SPREADING LIGHT RAIN WITH IT. SATELLITE DERIVED TROPICAL
PRECIPITABLE WATER SHOWS TPW GREATER THAN AN INCH. THIS MOISTURE
COMBINED WITH A 122KT UPPER LEVEL JET NOSING INTO SW
OREGON...PROVIDES A GREAT CHANCE FOR MEASURABLE RAIN ACROSS NW OREGON
AND SW WASHINGTON TODAY...AND HAVE INCREASED POPS.

RAIN SHOWERS ALONG THE COAST WILL SHIFT INLAND THROUGH THE DAY AND
HANG UP OVER THE CASCADES IN THE EVENING. LINGERING MOISTURE AND CALM
WINDS WILL LIKELY RESULT IN FOG DEVELOPING OVERNIGHT TONIGHT INTO
SATURDAY MORNING.  THINK THE BEST CHANCE FOR FOG WILL BE ALONG THE
COAST...BUT CAN NOT RULE OUT THE POSSIBILITY FOR FOG IN PARTS OF THE
NORTHERN AND CENTRAL WILLAMETTE VALLEY.

ANOTHER WEAK FRONT WILL MOVE ACROSS THE AREA SUNDAY. THE CHANCE FOR
RAIN IS WEAKER WITH THIS SYSTEM AS THE UPPER JET SHIFTS
NORTHWARD...AND REDUCED ATMOSPHERIC LIFT. THE PRECIPITATION ON
SUNDAY WILL BE VERY LIGHT...POSSIBLY MORE DRIZZLE THAN RAIN AND BE
RESTRICTED TO AREAS NORTH OF SALEM.

AN UPPER RIDGE WILL BUILD MONDAY...BUT THE MODELS HAVE BEEN BACKING
OFF ON THE STRENGTH OF THE RIDGE AND EXPECT ANOTHER WEAK FRONT TO
CLIP THE NORTHERN AREAS MONDAY AFTERNOON AND EVENING. TJ

.LONG TERM...A FLAT UPPER LEVEL RIDGE WILL DEVELOP OVER THE PACIFIC
NW TUESDAY...BEFORE A DEEPER TROUGH OVER WESTERN CANADA SLIDES
SOUTHWARD ALONG THE COAST....PUTTING ANOTHER UPPER TROUGH OVER THE
REGION TUESDAY NIGHT. SHORTWAVES MOVING AROUND THE TROUGH WILL KEEP
GENERAL TROUGHINESS OVER THE AREA THROUGH NEXT WEEKEND. TEMPERATURES
WILL GENERALLY BE NEAR SEASONAL NORMALS.

&&

.AVIATION...LIGHT SHOWERS ARE EXPECTED THROUGH THE DAY...THEN
DECREASE THIS EVENING. MOSTLY MVFR AND IFR CONDITIONS WILL
CONTINUE ALONG THE COAST...WITH THE LOWER CONDITIONS IN SHOWERS...
THEN TREND MORE TOWARDS MVFR THIS EVENING INTO SUNDAY. INLAND
AREAS...MAINLY VFR TODAY WITH OCCASIONAL MVFR CIGS AROUND
1500-2500 FT MAINLY AROUND THE LOWER COLUMBIA RIVER TO NEAR KPDX
THIS MORNING.

KPDX AND APPROACHES...VFR CONDITIONS WITH CIGS IN THE 4000-6000
FT RANGE ALONG WITH SOME LIGHT SHOWERS ESPECIALLY IN THE AFTERNOON
HOURS. A FEW 2000 FT CIGS WILL LINGER IN THE VICINITY THROUGH 17Z
THIS MORNING. /27

&&

.MARINE...ANOTHER WEAK FRONT WILL MOVE ACROSS THE WATERS TODAY AND
A THIRD...POTENTIALLY STRONGER FRONT SUNDAY AFTERNOON AND NIGHT.
THE SEAS WILL COMPRISE OF A SMALL SW SWELL OF 1 TO 2 FEET AT
AROUND 15 SECONDS AND A NORTHWEST FRESH SWELL FROM THE GULF OF
ALASKA AROUND 9 TO 10 SECONDS. LIGHT WIND WAVES THE NEXT COUPLE OF
DAYS. A NW SWELL WILL BUILD TONIGHT AND PEAK AROUND 6 FEET ON
SUNDAY. HIGH PRESSURE WILL REBUILD MONDAY NIGHT AND TUESDAY AND
PERSISTENT NORTHERLY WINDS WILL RETURN TO THE WATERS.
MH/WRIGHT/SCHNEIDER

&&

.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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