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[Printable]
787
FXUS66 KPQR 220415 AAA
AFDPQR

AREA FORECAST DISCUSSION...UPDATED
NATIONAL WEATHER SERVICE PORTLAND OR
915 PM PDT MON JUL 21 2014

.SYNOPSIS...A LOW PRESSURE SYSTEM WILL BRING AN INCREASING THREAT
OF SHOWERS TO THE AREA TUESDAY AND ESPECIALLY WEDNESDAY. A FEW
THUNDERSTORMS WILL BE POSSIBLE NEAR THE CASCADE CREST TUESDAY
EVENING. EVEN THOUGH WEDNESDAY WILL LIKELY BE THE COOLEST DAY OF THE
WEEK...THUNDER WILL BE POSSIBLE WITH ANY OF THE HEAVIER SHOWERS.
DRIER AND MORE SUMMERLIKE TEMPERATURES ARE EXPECTED TO ARRIVE LATE IN
THE WORK WEEK AND CONTINUE INTO THE WEEKEND.

&&
.UPDATE...DID NOT MAKE ANY CHANGES WITH THE EVENING UPDATE AS THE
FORECAST IS ON TRACK. WATER VAPOR IMAGERY SHOWS A SEMI SPLITTING
UPPER TROUGH OVER THE NE PACIFIC WITH AN UPPER LOW OFFSHORE THE
BRITISH COLUMBIA COAST AND ANOTHER ONE OFF OF SOUTHERN CALIFORNIA.
THERE IS ALSO AN UPPER SHORTWAVE BETWEEN THESE TWO LOWS DIGGING OFF
OF NORTHEN CALIFORNIA. THESE SYSEMS ARE STEERING A BAND OF MID LEVEL
MOISTURE ACROSS OREGON.  A WEAK FRONT THAT WAS STALLED SOUTH OF LANE
COUNTY THIS AFTERNOON HAS SHIFTED NORTH THIS EVENING AND IS
GENERATING SOME LIGHT SHOWERS OVER LANE COUNTY. A BAND OF CONVECDTION
SOUTH OF THIS FRONT IS APPROACHING LANE COUNTY...BUT SHOULD REMAIN
SOUTH AND EAST OF LANE COUNTY.

PREVIOUS DISCUSSION FOLLOWS...TONIGHT THROUGH THURSDAY...A LOOP OF
WATER VAPOR SATELLITE SHOWS A SHORTWAVE DIGGING SOUTHWARD NEAR 135W
AND 40N. VISIBLE SATELLITE IMAGERY SHOWS PLENTY OF MID LEVEL CLOUDS
STREAMING NORTHEASTWARD INTO SOUTHWEST OREGON ALONG AN OLD MID LEVEL
BAROCLINIC ZONE. WHILE DOPPLER RADAR HAS LOOKED RATHER OMINOUS
UNDERNEATH THIS BAND...MOST OF THE PRECIPITATION HAS BEEN FALLING IN
THE FORM OF VIRGA. HOWEVER...THE LOWER ATMOSPHERE IS BEGINNING TO
MOISTEN FROM THE TOP DOWN NEAR ROSEBURG WHERE A COUPLE OF RAWS
STATIONS HAVE RECENTLY MEASURED A HUNDREDTH. WHILE MODELS PRODUCE
LITTLE QPF ACROSS OUR CWA TONIGHT...MOST MODELS AGREE THIS BAND WILL
HOLD TOGETHER...IF NOT STRENGTHEN SLIGHTLY...AS IT BECOMES
INCREASINGLY WARM FRONTAL AND SHIFTS EVER SO SLOWLY NORTHWARD
TONIGHT. AS A RESULT...SLIGHT CHANCE POPS WERE INTRODUCED FOR TONIGHT
TO THE SOUTH AND EAST OF PORTLAND DUE TO THIS BAND OF PRECIPITATION.

AS A MORE POWERFUL SHORTWAVE TROUGH CURRENTLY DIGGING SOUTHWARD NEAR
THE QUEEN CHARLOTTE ISLANDS...CONTINUES SOUTHWARD TUESDAY...THE MID
LEVEL FLOW WILL BUCKLE AND TURN MORE SOUTHERLY ACROSS THE AREA LATER
TUESDAY. WITH INCREASING MID TO UPPER LEVEL SUPPORT...THE
AFOREMENTIONED BAND OF MID LEVEL MOISTURE WILL STRENGTHEN FURTHER AND
BRING AN INCREASING THREAT OF PRECIPITATION TO OUR NORTHWESTERN ZONES
TUESDAY AFTERNOON. MEANWHILE...THE CASCADES WILL BEGIN TO
DESTABILIZE AS SKIES CLEAR A BIT. A CAP MAY INHIBIT SURFACE BASED
CONVECTION FROM DEVELOPING LATE TUESDAY AFTERNOON...BUT
THUNDERSTORMS DEVELOPING FURTHER SOUTH OF THE CWA...MAY CLIP OUR
CASCADES AS THEY MOVE NORTHEASTWARD TUESDAY EVENING...PARTICULARLY
ACROSS EASTERN LANE AND LINN COUNTIES.

THE MAIN VORT MAX AND COLD POOL ASSOCIATED WITH THE AFOREMENTIONED
SHORTWAVE TROUGH SHOULD PIVOT EASTWARD...IF NOT SLIGHTLY
NORTHEASTWARD...ACROSS THE NORTHERN HALF OF THE FORECAST AREA
WEDNESDAY. CLOUD COVER MAY INITIALLY LIMIT CONVECTION...BUT WITH
DAYTIME HEATING...SUN BREAKS SHOULD ALLOW SHOWERS AND ISOLATED
THUNDERSTORMS TO BUBBLE UP DURING THE AFTERNOON...PARTICULARLY ACROSS
THE NORTHERN HALF OF THE CWA. MANY OF THE FOOTHILLS AND SOME VALLEY
LOCATIONS SHOULD SEE WETTING RAINS. SHOWERS ACTIVITY SHOULD DECREASE
WEDNESDAY NIGHT. A FEW SHOWERS MAY LINGER ACROSS OUR NORTHERN ZONES
ON THURSDAY...BUT IN GENERAL MOST LOCATIONS SHOULD SEE MUCH DRIER AND
PLEASANT WEATHER ON THURSDAY. /NEUMAN
&&

.LONG TERM...AN UPPER-LEVEL RIDGE IS FORECAST TO BUILD BACK IN OVER
THE PACIFIC NORTHWEST BRINGING HIGH PRESSURE OVER OUR AREA.
SOUTHWESTERLY WINDS AND GENERALLY SUNNY SKIES WILL CAUSE
TEMPERATURES TO INCREASE BY EARLY THIS WEEKEND. TEMPERATURES ARE
FORECAST TO GET BACK INTO THE MID 80S BY FRIDAY AND POSSIBLY REACH
THE LOW 90S IN SOME AREAS INLAND AS EARLY AS SATURDAY. -MCCOY
&&

.AVIATION...VFR CONDITIONS PREVAIL THIS EVENING...WITH CIGS
AROUND 10K-25K FT. BAND OF RAIN IS LIFTING NORTH ACROSS THE SOUTH
WILLAMETTE VALLEY THIS EVENING...BRINGING LIGHT RAIN TO THE AREA
AND WILL GRADUALLY SPREAD NORTH TOWARDS KSLE TONIGHT. EXPECT SOME
LOWERING CLOUDS ALONG THE COASTAL AREAS LATE TONIGHT/EARLY
TUE...WITH THE POTENTIAL FOR BRIEF PERIODS OF LOCAL MVFR THOUGH
CONFIDENCE REMAINS SOMEWHAT LOW THAT CIGS LOWER INTO MVFR.

KPDX AND APPROACHES...VFR CONDITIONS NEXT 24 HOURS WITH
INCREASING HIGH CLOUDS. CULLEN/27
&&

.MARINE...RELATIVELY QUIET CONDITIONS OVER THE WATERS CONTINUE
TONIGHT AS THE SURFACE GRADIENT REMAINS WEAK...KEEPING WINDS
GENERALLY 10 KT OR LESS. SEAS REMAIN NEAR 5 FT THROUGH TONIGHT
BEFORE DECREASING INTO THE 3 TO 5 FT RANGE THROUGH THU.

A WEAK LOW PRES SYSTEMS WILL PASS THROUGH THE WATERS TUE INTO
WED...BUT WITH LITTLE IMPACT AS WINDS SHOULD REMAIN 15-20 KT OR
LESS. LATER THIS WEEK...HIGH PRES REDEVELOPS OVER THE NE PAC AS
THERMAL LOW PRES BUILDS OVER N CALIFORNIA...BRINGING A RETURN TO
GUSTY N WINDS AND STEEP WIND DRIVEN SEAS FRI THROUGH THE WEEKEND.
CULLEN

&&

.PQR WATCHES/WARNINGS/ADVISORIES...
OR...WA...NONE.
PZ...NONE.

&&

$$


MORE WEATHER INFORMATION ONLINE AT...HTTP://WEATHER.GOV/PORTLAND


INTERACT WITH US VIA SOCIAL MEDIA
WWW.FACEBOOK.COM/US.NATIONALWEATHERSERVICE.PORTLAND.GOV
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.
COMMONLY REFERRED TO AS THE FORECAST AREA.




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