Area Forecast Discussion
Issued by NWS Portland, OR

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FXUS66 KPQR 231828 CCA
AFDPQR

AREA FORECAST DISCUSSION...CORRECTED SYNOPSIS
NATIONAL WEATHER SERVICE PORTLAND OR
1127 AM PDT SAT AUG 23 2014

.SYNOPSIS...HIGH PRESSURE WITH PLENTY OF SUNSHINE TODAY. AN UPPER
TROUGH NORTH OF THE AREA WILL DROP SOUTH OVER THE PACIFIC NORTHWEST
LATE TONIGHT INTO SUNDAY...RESULTING IN SLIGHT COOLING...DRIZZLE OR
FOG ALONG THE COAST...AND AFTERNOON CASCADE SHOWERS. HIGH PRESSURE
WILL REBUILD MONDAY FOR DRY AND WARMER WEATHER NEXT WEEK.

&&

.UPDATE...WATER VAPOR IMAGERY SHOWS HIGH PRESSURE OVER THE NE PACIFIC
AND A BROAD TROUGH OVER THE WESTERN CONTINENTAL. HAVE MADE MINOR
CHANGES TO THE SKY COVER TODAY AS VISIBLE IMAGERY SHOWS CLEAR SKIES
INLAND. ALSO REMOVED SHOWERS OVER THE SW WASHINGTON CASCADES FOR THIS
AFTERNOON. EXPECT SHALLOW CUMULUS OVER THE NORTHERN CASCADES THIS
AFTERNOON...BUT THINK MOISTURE IS TOO LIMITED TO GENERATE ANY
MEASURABLE RAINFALL.

THE PORTLAND FORECAST AREA IS MOSTLY UNDER THE INFLUENCE OF THE HIGH
TODAY...BUT AN UPPER LEVEL TROUGH CURRENTLY OVER WESTERN CANADA WILL
DROP SOUTHWARD TONIGHT...AND MOVE OVER THE PACIFIC NW SUNDAY. THIS
WILL RESULT IN AN INCREASE OF ONSHORE FLOW...SOME PATCHY FOG AND
DRIZZLE ALONG THE COAST SUNDAY MORNING AND SHOWERS OR THUNDERSTORMS
ALONG THE WASHINGTON AND NORTHERN OREGON CASCADES IN THE AFTERNOON.
TJ

PREVIOUS DISCUSSION FOLLOWS...SKIES WERE MOSTLY CLEAR OVER MUCH OF
SOUTHWEST WASHINGTON AND NORTHWEST OREGON THIS MORNING EXCEPT FOR
AREAS OF LOW CLOUDS OR FOG SPREADING SOUTH ALONG THE COAST. THE LOW
CLOUDS WERE APPROACHING KELSO EARLY THIS MORNING...BUT MAY HAVE
TROUBLE REACHING PORTLAND OR VANCOUVER. THE UPPER LOW THAT HAD BEEN
OVER CENTRAL AND EASTERN WASHINGTON AND OREGON HAD MOVED INTO IDAHO
THIS MORNING AND WILL CONTINUE MOVING EAST. THERE IS SOME WEAK ENERGY
OR VORTICITY MOVING THROUGH THE PACIFIC NORTHWEST ON THE BACK SIDE OF
THE LOW THAT MAY TRIGGER AN ISOLATED SHOWER NEAR THE CASCADE CREST
AND EAST SLOPES THIS AFTERNOON AND EVENING. WITH THE LOW MOVING AWAY
AND WITH RISING 500 MB HEIGHTS...TEMPS INLAND SHOULD CLIMB SOME TODAY
AND APPROACH THE MID 80S.

A SYSTEM ALONG THE CENTRAL B.C. COAST THIS MORNING IS FORECAST TO
APPROACH OUR FORECAST AREA LATE TONIGHT AND MOVE THROUGH ON SUNDAY
INTO SUNDAY EVENING. THE CORE OF THE ENERGY WILL MOVE THROUGH
CENTRAL AND EASTERN WASHINGTON AND OREGON...BUT ENOUGH WILL MOVE
THROUGH OUR FORECAST AREA TO LOWER 500 MB HEIGHTS INTO THE MID 570S.
THIS WILL INCREASE THE ONSHORE FLOW AND LOWER TEMPS ON SUNDAY. THE
MODELS SUGGEST SOME DRIZZLE OR SPRINKLES ARE POSSIBLE ON THE COAST
SUNDAY MORNING...WITH A SLIGHT CHANCE OF A SHOWER OR THUNDERSTORM
OVER THE HIGHER CASCADES. THE VALLEYS WILL SEE SOME MIXTURE OF
CLOUDS BUT PRECIPITATION IS LOOKING DOUBTFUL. 850 MB TEMPS SUGGEST
VALLEY HIGHS WILL BE IN THE UPPER 70S TO AROUND 80 ON SUNDAY.

THIS SYSTEM DIGS INTO THE NORTHERN GREAT BASIN THEN SWINGS EAST
SUNDAY NIGHT AND MONDAY. THIS SHOULD MAINTAIN THE INCREASED ONSHORE
FLOW INTO MONDAY MORNING FOR AREAS OF LOW CLOUDS INLAND. AN UPPER
RIDGE STARTS TO NOSE IN MONDAY AFTERNOON FROM THE WEST...AND THIS
SHOULD BRING AFTERNOON CLEARING AND WARMING TEMPS...WITH HIGHS INLAND
PUSHING INTO THE MID 80S AGAIN. TOLLESON

.LONG TERM...NO CHANGES. PREVIOUS DISCUSSION FOLLOWS...
THE UPPER LEVEL RIDGE IS STILL FORECASTED TO MOVE ONSHORE ON TUESDAY
ALLOWING OUR TEMPERATURES TO INCREASE SLIGHTLY ABOVE SEASONAL NORMS
FOR THE BEGINNING PART OF NEXT WEEK. AS THIS RIDGE PROGRESSES
EASTWARD WE WILL LIKELY SEE SOME ZONAL UPPER LEVEL FLOWS DEVELOP OVER
THE FORECAST AREA ALLOWING LOW AND MID LEVEL MOISTURE TO MOVE IN AND
PROVIDE FOR AN INCREASE IN CLOUD COVER OVER MUCH OF THE CWA ON LATE
WEDNESDAY. BEYOND WEDNESDAY...BOTH THE GFS AND ECMWF ARE HINTING AT
A SHORTWAVE MOVING THROUGH OUR REGION AS THE MEAN LONG WAVE TROUGH
MOVES DOWN FROM THE GULF OF ALASKA. THIS COULD BRING A CHANCE OF
RAIN SHOWERS TO THE NORTHERN CASCADES FOR THE LATTER PART OF NEXT
WEEK. THE TIMING AND LOCATION ARE STILL UNCERTAIN AT THIS POINT AND
WILL BE NARROWED DOWN WITH FUTURE UPDATES. /64

&&

.AVIATION...MARINE STRATUS PRODUCING MAINLY LIFR TO IFR CONDITIONS
ALONG THE COAST SHOULD GIVE WAY TO VFR CONDITIONS THIS AFTERNOON.
EXPECT LIFR/IFR CONDITIONS TO PUSH BACK INTO THE COAST THIS
EVENING AND CONTINUE THROUGH SUNDAY MORNING. FURTHER
INLAND...PRESSURE GRADIENTS SHOULD REMAIN WEAK ENOUGH TO KEEP ALL
WILLAMETTE VALLEY TAF SITES VFR THROUGH 18Z SUNDAY. THERE IS A CHANCE
STRATUS MAY MAKE IT TO KPDX AND KTTD...BUT CONFIDENCE IS VERY LOW.

KPDX AND APPROACHES...HIGH PRESSURE WILL LEAD TO VFR CONDITIONS
THROUGH 18Z SUNDAY. THERE IS A CHANCE IFR CONDITIONS WILL PUSH
TEMPORARILY INTO THE TERMINAL AROUND 14Z SUNDAY...BUT CONFIDENCE
IS VERY LOW. /NEUMAN

&&

.MARINE...HIGH PRESSURE LOOKS TO REMAIN IN CONTROL OVER THE
NORTHEAST PACIFIC THROUGH AT LEAST EARLY NEXT WEEK. THERMAL LOW
PRESSURE OVER INTERIOR CALIFORNIA IS CURRENTLY SHIFTING SQUARELY
OVER THE CALIFORNIA COAST...AND WILL DO SO AGAIN LATE MONDAY INTO
TUESDAY. THIS SHOULD PRODUCE A STRONGER NORTH TO SOUTH PRESSURE
GRADIENT CONDUCIVE FOR GUSTY NORTHERLY WINDS TO SURFACE ACROSS THE
WATERS THIS EVENING...AND AGAIN EARLY NEXT WEEK DURING THE
EVENING HOURS. AS A RESULT...CONTINUED THE SMALL CRAFT ADVISORY
FOR WINDS FOR LATE THIS AFTERNOON AND EVENING. ALSO...DEPENDING ON
WIND TRENDS THIS AFTERNOON...MAY ALSO ISSUE A SMALL CRAFT FOR
HAZARDOUS SEAS FOR TONIGHT DUE TO SQUARE CHOPPY SEAS ACROSS THE
CENTRAL OREGON WATERS. IN THE LONGER TERM...WE MAY SEE A SOUTHERLY
WIND REVERSAL...USUALLY ACCOMPANIED BY FOG AND LOW CLOUDS...PUSH
NORTHWARD UP THE COAST EARLY THURSDAY...BEFORE A DYING FRONT TRIES
TO PUSH INTO THE WATERS TOWARDS FRIDAY. HOWEVER...MARINE IMPACTS
LOOK TO REMAIN RATHER MINIMAL. /NEUMAN

&&

.PQR WATCHES/WARNINGS/ADVISORIES...
OR...NONE.
WA...NONE.
PZ...SMALL CRAFT ADVISORY FOR WINDS FROM 2 PM THIS AFTERNOON TO 3 AM
     PDT SUNDAY FOR COASTAL WATERS FROM CASCADE HEAD OR TO FLORENCE
     OR OUT 60 NM.

&&

$$

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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