Area Forecast Discussion
Issued by NWS Portland, OR

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FXUS66 KPQR 070950
AFDPQR

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE PORTLAND OR
250 AM PDT TUE JUL 7 2015

.SYNOPSIS...THE PERSISTENT RIDGE OF HIGH PRESSURE RESPONSIBLE FOR
THE EARLY JULY HEAT WAVE WILL GRADUALLY WEAKEN THIS WEEK AS ONSHORE
FLOW STRENGTHENS A BIT. AN UPPER LOW OFF CALIFORNIA MAY DRIFT FAR
ENOUGH NORTH THIS WEEK TO BRING THUNDERSTORMS TO THE CASCADE CREST
IN LANE COUNTY TUE AND WED...AND TO THE REST OF THE CASCADES BY THU.
TEMPERATURES WILL COOL DOWN CLOSER TO SEASONAL NORMALS BY THE END OF
THE WEEK AS A TROUGH OF LOW PRES APPROACHES THE COAST.
&&

.SHORT TERM...MODELS APPEAR IN GOOD AGREEMENT IN WEAKENING THE UPPER
RIDGE TODAY AND WED AS THE UPPER LOW OFF THE CA COAST PUSHES CLOSER
TO THE CENTRAL CA COAST. A SHORTWAVE ROTATING AROUND THE LARGE
CANADIAN UPPER LOW WILL BRUSH THE PACIFIC NW STATES TODAY. SURFACE
PRES GRADIENTS EARLY THIS MORNING ARE STRONGER THAN PREVIOUS 24
HOURS UP AND DOWN THE COAST AS EVIDENCED BY THE CONTINUING ONSHORE
BREEZES AT 08Z STILL BLOWING THROUGH THE COAST RANGE GAPS INTO THE
WILLAMETTE VALLEY. HIGH CLOUDS ON SATELLITE ARE PARTIALLY MASKING TH
MARINE CLOUDS THIS MORNING...BUT IT APPEARS THAT CLOUDS ARE POSIED
TO PUSH INTO THE S VALLEY THIS MORNING...AND MAY REACH UP THE LOWER
COLUMBIA AS FAR AS PDX. THE STRENGTHENED ONSHORE FLOW THIS
MORNING...MORE FROM THE NW THAN THE SW DIRECTION SEEN MON...IS
LIKELY TO BRING A FEW DEGREES COOLING TO THOSE PARTS OF THE INLAND
VALLEYS THAT REMAINED ON THE HOT SIDE MON. THERE APPEARS TO STILL BE
A DECENT CHANCE AT CONTINUING THE STRING OF 90 DEGREE HIGHS IN THE N
AND CENTRAL WILLAMETTE VALLEY TODAY...BUT A FEW DEGREES COOLING
PROBABLY WILL NOT JUSTIFY MAINTAINING THE HEAT ADVISORY SO WILL DROP
THAT. H8 TEMPS REMAIN IN THE 18 TO 20 DEG RANGE WED AND THU WITH
CONTINUED ONSHORE FLOW...SO EXPECT INLAND HIGHS TO REMAIN IN THE
UPPER 80S TO LOWER 90S RANGE. AT THE COAST THE STRENGTHENED ONSHORE
FLOW MAY MAKE IT DIFFICULT FOR CLOUDS TO CLEAR OFF IN THE AFTERNOONS
FOR THE NEXT FEW DAYS...LLIKELY LEAVING HIGH TEMPS IN THE 60S TO
LOWER 70S.

MODELS KEEP THE WEAKENING UPPER RIDGE AXIS NEAR THE S BORDER TO THE
FORECAST AREA BOTH TUE AND WED...WHICH LEAVES THE S PART OF THE
CASCADES MOST PRONE TO SEEING MOISTURE AND INSTABILITY SPREAD UP
AHEAD OF THE LOW OFF THE CA COAST. AT THIS POINT APPEARS BEST
CHANCES FOR CONVECTION TO REMAIN TO THE S...SO WILL KEEP THE SLIGHT
CHANCE FOR THUNDERSTORMS LIMITED TO THE LANE COUNTY CASCADES BOTH
DAYS. MODELS SHOW THE CIRCULATION AROUND THE CA LOW OPENING UP SOME
BY THU...DEVELOPING A MORE EASTERLY MID AND UPPER LEVEL FLOW THAT
WILL SPREAD INCREASED INSTABILITY INTO THE CASCADES FOR A CHANCE OF
THUNDERSTORMS.

.LONG TERM...NO CHANGES. PREVIOUS DISCUSSION FOLLOWS...THURSDAY
NIGHT THROUGH SUNDAY...A MUCH NEEDED CHANGE IN THE WEATHER PATTERN
WILL OCCUR THURSDAY NIGHT AND FRIDAY AS THE UPPER LOW OVER ALASKA
STARTS TO EXTEND SOUTH ACROSS THE NE PACIFIC...AS THE UPPER LOW TO
THE SOUTH MOVES INLAND. THIS WILL RESULT IN A DEEPER MARINE PUSH
THURSDAY NIGHT AND MUCH COOLER TEMPERATURES FRIDAY. INLAND
TEMPERATURES WILL STILL BE ABOVE NORMAL...BUT AROUND 5 DEGREES ABOVE
NORMAL RATHER THAN THE 15 DEGREES THAT WE HAVE BEEN HAVING THE LAST
COUPLE OF WEEKS. THE UPPER TROUGH WILL REPLACE THE UPPER RIDGE
SATURDAY FOR COOLER WEATHER AND POSSIBLY SOME SHOWERS FOR THE
WEEKEND. TJ
&&

.AVIATION...DEEPENING MARINE STRATUS ON THE COAST AND PUSHING
INLAND THROUGH GAPS IN THE COAST RANGE AND LOWER COLUMBIA RIVER.
CIGS AROUND 1500 FEET AT THE COASTAL LOCATIONS. EXPECT CLOUDS TO
BURN BACK TO THE BEACHES AROUND MIDDAY BUT RETURN LATER IN THE
AFTERNOON. FOR INLAND AREAS THE KPDX AND KEUG AREAS STAND THE BEST
CHANCES FOR CIGS AROUND 1500-2000 FT TO FORM 13Z THRU 18Z...THEN
RETURNING TO VFR. HIGHER CLOUDS ARE MAKING IS SOME WHAT DIFFICULT
TO ACCURATELY LOCATE STRATUS. HOWEVER MODEL DEPICTIONS ARE FAIRLY
CLOSE TO WHAT CAN BE SEEN ON SATELLITE SO CONFIDENCE IS GOOD.

INSTABILITY OVER THE LANE COUNTY CASCADES WILL LIKELY
ALLOW ISOLATED THUNDERSTORMS TO DEVELOP THIS AFTERNOON/EVENING
BETWEEN 21-04Z.

KPDX AND APPROACHES...VFR CONDITIONS WITH TEMPORARILY MVFR CIGS
AROUND 1500-2000 FT BETWEEN 13Z AND 16Z.  /MH

&&

.MARINE...SURFACE GRADIENTS ARE NOT TOO STRONG SO WINDS ARE
GENERALLY 10 KTS OR LESS. AS THE OFFSHORE HIGH BUILDS IN TOMORROW
WINDS WILL SHIFT FROM SOUTHWEST TO NORTHWEST REMAINING FAIRLY
LIGHT. SHORT PERIOD WIND DRIVEN SWELL OF AROUND 2 FT IS COMBINED
WITH A 2 TO 3 FT SOUTHWEST SWELL OVER THE WATERS OVER THE NEXT FEW
DAYS. FRESH SWELL WEAKENS AND IT LOOKS LIKE THE DOMINANT SWELL
WILL BECOME THE SOUTHWEST SWELL ON TUESDAY. SCHNEIDER /MH

&&

.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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