Area Forecast Discussion
Issued by NWS Portland, OR

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FXUS66 KPQR 281022
AFDPQR

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE PORTLAND OR
317 AM PDT THU AUG 28 2014

.SYNOPSIS...UPPER RIDGE THAT HAS BEEN RESPONSIBLE FOR THE WARM
WEATHER WILL WEAKEN AND SHIFT EASTWARD THU AND FRI. THIS WILL ALLOW
FOR WESTERLY FLOW OFF THE N PAC TO ARRIVE...BRINGING COOLER AIR AND
EVEN A THREAT OF SHOWERS FOR THIS WEEKEND. DRY WEATHER RESUMES NEXT
WEEK...WITH MORE SEASONABLE TEMPERATURES FOR EARLY SEPTEMBER.
&&

.SHORT TERM...THROUGH SATURDAY...A SLOW PATTERN CHANGE OCCURRING OVER
THE NEXT FEW DAYS. MAINLY BRINGING COOLER TEMPERATURES...MORE CLOUDS
AND PERHAPS SOME LIGHT PCPN.  THIS MORNING A SHALLOW MARINE LAYER
BRINGING EXTENSIVE STRATUS TO THE COAST AND GAPS LEADING INLAND.
THERE IS SOME FOG BUT NOT QUIET AS THICK AS WED MORNING. STRATUS HAS
WORK UP THE LOWER COLUMBIA RIVER TO KELSO. CURRENT KAST-KPDX GRADIENT
IS DECREASING BELOW 2 MB SO IT MAY JUST MAKE IT TO THE PDX AND
VICINITY FOR A FEW HOURS THIS MORNING.TEMPERATURES LOOK ON TRACK TO
REACH THE LOW TO MID 80S INLAND WHILE THE COAST TOPS OUT IN THE MID
60S.

WATERVAPOR LOOP SHOWS A DEEPENING TROUGH OVER THE GULF OF ALASKA THAT
MODELS TRACK INTO WESTERN B.C. ON FRIDAY. ONE SHORTWAVE AHEAD OF THIS
TROUGH WILL MOVE THROUGH TODAY...MAINLY TO INCREASE THE ONSHORE FLOW
AND BRING SOME LOWERING 500 MB HEIGHTS.  AS THE LARGE TROUGH MOVES TO
WESTERN B.C. THE TRAILING END BRUSHES THE PACNW BRINGING LOW CHANCES
FOR SHOWERS ON FRI...MAINLY TO THE NORTH COAST ZONES. THE TROUGH
FURTHER SAGS INTO THE PACNW ON SAT WITH A CHANCE FOR SOME SHOWERS
ALONG WITH COOLER WEATHER. AFTERNOON HIGHS ARE EXPECTED TO REMAIN IN
THE LOW TO MID 70S OVER THE INTERIOR. WITH THE DEEP MARINE LAYER IN
PLACE...AGAIN EXPECT A CHANCE FOR SOME SHOWERS OR
DRIZZLE...PARTICULARLY FOR THE COAST AND THE NORTHERNMOST PORTIONS OF
THE FORECAST AREA.  SIDE NOTE - OVER THE NEXT WEEK OR TWO THE AVERAGE
HIGH TEMPERATURES INLAND DROP BELOW 80.

.LONG TERM...ECMWF...GFS AND DGEX TODAY DRASTICALLY CUT BACK ON
MOISTURE OVER OUR CWA FOR THIS WEEKEND...AND REMOVED MOST OF THE
PRECIPITATION SOUTH OF THE COLUMBIA RIVER THROUGH MONDAY.  THIS GOES
WITH THE TREND AND CLIMATOLOGY OF TROUGHS FROM THE NORTHWEST THIS
TIME OF YEAR WHERE MOISTURE ISN`T SUFFICIENT FOR SIGNIFICANT
RAINFALL OVER MOST OF OUR AREA. I LEFT A CHANCE FOR RAIN OVER HIGHER
TERRAIN OVER THE OR COASTAL RANGE AND WA...BUT REDUCED POPS TO A
SLIGHT CHANCE ELSEWHERE OVER THE NORTHERN HALF AND DROPPED POPS
INLAND SOUTH. EARLY NEXT WEEK WEAK RIDGING LOOKS TO BUILD IN
INDICATING A WARMING TREND TOWARD CLIMATOLOGY. -MCCOY
&&

.AVIATION...LOW MARINE CLOUDS HAVE RESULTED IN IFR CONDITIONS FOR
THE COAST EARLY THIS MORNING. THE MARINE CLOUDS ARE PUSHING INLAND
WITH MVFR CIGS EXPECTED AT KSPB AND PARTS OF THE NORTHERN
WILLAMETTE VALLEY BETWEEN 13 AND 16Z. FLIGHT CONDITIONS SHOULD
IMPROVE TO VFR INLAND BY 18Z...BUT ONSHORE WINDS SHOULD MAINTAIN
CLOUDY SKIES FOR THE COAST MOST OF THE DAY. EXPECT A BRIEF PERIOD OF
MVFR CIGS FOR THE COAST THIS AFTERNOON BEFORE IFR CIGS RETURN THIS
EVENING. AREAS OF SMOKE ARE POSSIBLE IN EASTERN LANE COUNTY DUE
TO WILDFIRES. STRATUS IS MORE LIKELY TO PUSH FURTHER INTO THE
WILLAMETTE VALLEY TONIGHT.

KPDX AND APPROACHES...MOSTLY VFR CONDITIONS TODAY. THERE MAY BE A
BRIEF PERIOD OF LOW MVFR CIGS THIS MORNING AFT 13Z...BUT
CONFIDENCE IS NOT HIGH. ANY LOW CLOUDS THAT MAY FORM SHOULD CLEAR
BY 18Z. THERE IS ANOTHER CHANCE FOR MVFR CIGS LATE TONIGHT. TJ

&&

.MARINE...A SERIES OF WEAK FRONTS WILL MOVE ACROSS THE WATERS
THROUGH THE WEEKEND...AND MAINTAIN A WEAK SURFACE PRESSURE
GRADIENT. WINDS WILL REMAIN AROUND 10 KT OUT OF THE NW...BRIEFLY
SHIFTING W AND SW WITH EACH FRONTAL PASSAGE. THE SEAS WILL
COMPRISE OF A SMALL SW SWELL AND STEEP WIND WAVES THE NEXT COUPLE
OF DAYS. A NW SWELL WILL BUILD SATURDAY NIGHT AND PEAK AROUND 7
FEET ON SUNDAY. HIGH PRESSURE WILL REBUILD MONDAY NIGHT AND
TUESDAY AND PERSISTENT NORTHERLY WINDS WILL RETURN TO THE WATERS.
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.



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