Area Forecast Discussion
Issued by NWS Portland, OR

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FXUS66 KPQR 032139
AFDPQR

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE PORTLAND OR
239 PM PDT MON AUG  3 2015

.SYNOPSIS...THE WEATHER DISTURBANCE THAT MOVED NORTH INTO OREGON AND
WASHINGTON SUNDAY WAS MOVING EAST THIS AFTERNOON...AND WILL BE EAST
OF THE AREA THIS EVENING. AN UPPER TROUGH ALONG THE B.C. COAST WILL
CONTINUE TO SAG SOUTH INTO THE PACIFIC NORTHWEST TONIGHT THROUGH
TUESDAY AND WEDNESDAY. THIS WILL INCREASE THE ONSHORE FLOW FROM THE
NORTHWEST FOR MORE NIGHT AND MORNING LOW CLOUDS AND COOLER TEMPS...
AS WELL AS PRODUCE WESTERLY FLOW ALOFT THAT WILL KEEP CONVECTION EAST
OF THE AREA. AFTER A BRIEF WARMUP LATE IN THE WEEK...ANOTHER UPPER
TROUGH IS FORECAST TO DEVELOP ALONG THE COAST NEXT WEEKEND INTO EARLY
THE FOLLOWING WEEK.
&&

.SHORT TERM...AN UPPER LOW CONTINUES OFF THE CALIFORNIA COAST... AND
HAS BEEN STEERING MOISTURE NORTHWARD INTO OREGON AND WASHINGTON OVER
THE LAST 24 HOURS. THE MAIN SHORT WAVE ASSOCIATED WITH THIS AREA OF
MOISTURE WAS MOVING EAST OF THE CASCADES THIS AFTERNOON...AND SHOULD
BE EAST OF THE AREA THIS EVENING WITH DECREASING CLOUDS...MORE LIKE
THE SLOWER NAM12 MODEL AND NOT LIKE THE FASTER GFS AND ECMWF MODELS.

WE DID GET A FEW THUNDERSTORMS THIS MORNING IN THE CENTRAL OREGON
CASCADE FOOTHILLS. THERE ARE STILL A FEW SHOWERS IN THE CASCADES THIS
AFTERNOON...AS WELL AS ONE OTHER AREA MOVING OFF THE COAST RANGE INTO
THE CENTRAL WILLAMETTE VALLEY. THESE AREAS SHOULD DECREASE THROUGH
THE AFTERNOON. WE MAY STILL SEE A FEW STORMS IN THE HIGHER CASCADES
THIS AFTERNOON AND EARLY EVENING...BUT THINGS SHOULD SETTLE DOWN
FAIRLY QUICKLY AS LIGHT SOUTHWEST FLOW TAKES HOLD. CLOUDS ARE
STARTING TO THIN A BIT THIS AFTERNOON FOR BETTER HEATING...SO WE
STILL HAVE A DECENT CHANCE TO REACH THE FORECAST AFTERNOON HIGHS.

THERE IS AN UPPER TROUGH ALONG THE B.C. COAST THAT IS ALREADY SAGGING
SOUTH TOWARD THE PACIFIC NORTHWEST...AND WILL BEGIN AFFECTING THE
PACIFIC NORTHWEST MORE TONIGHT AND TUESDAY. THIS WILL INCREASE THE
ONSHORE FLOW FROM THE NORTHWEST TONIGHT AND TUESDAY AS 500 MB HEIGHTS
FALL INTO THE UPPER 570S. LOOK FOR MORE MORNING LOW CLOUDS INLAND IN
THE NORTH ALONG THE COLUMBIA RIVER THAN WE HAVE SEEN IN A WEEK OR SO.
TEMPS WILL COOL INLAND AS WELL ON TUESDAY... WITH NEAR 80 NORTH BUT
STILL PROBABLY MID TO UPPER 80S NEAR EUGENE.

THE UPPER TROUGH TO OUR NORTH WILL LINGER THROUGH WEDNESDAY WITH MORE
NORTHWEST ONSHORE FLOW AND MORE MORNING LOW CLOUDS ESPECIALLY
NORTH...POSSIBLY EVEN WORKING THEIR WAY MORE SOUTHWARD IN THE
WILLAMETTE VALLEY THAN ON TUESDAY. THE MODELS SHOW A WEAK PIECE OF
ENERGY ROTATING AROUND THE BASE OF THE UPPER TROUGH AND THROUGH
WESTERN WASHINGTON LATE TUESDAY NIGHT AND WEDNESDAY. THE MODELS
SUPPORT OUR CURRENT FORECAST OF SOME DRIZZLE ON THE NORTH COAST.
THERE IS A SMALL POSSIBILITY OF SOME LIGHT PRECIPITATION REACHING THE
NORTH INTERIOR ZONES WEDNESDAY MORNING...BUT THIS IS NOT CERTAIN YET.
TEMPS INLAND IN THE NORTH WEDNESDAY WILL LIKELY BE 75 TO 80 WITH 80
TO 85 NEAR EUGENE. THIS WILL BE THE COOLEST DAY OF THE WORK WEEK.

THE UPPER TROUGH TO OUR NORTH MOVES EAST WEDNESDAY NIGHT AND
THURSDAY. THIS WILL ALLOW THURSDAY TO BE A WARMER DAY WITH MORE
SUNSHINE THAN THE PREVIOUS TWO DAYS...WITH THE MORNING LOW CLOUDS
MAINLY NORTH AND CLEARING EARLIER THAN ON TUESDAY OR WEDNESDAY.
TOLLESON

.LONG TERM...BROAD UPPER-LEVEL TROUGH AND CONTINUED ONSHORE FLOW
SHOULD KEEP TEMPERATURES OUT OF THE 90S LATE THIS WEEK INTO THE
WEEKEND...BUT WEAKENING ONSHORE FLOW AND WINDS BECOMING MORE
SOUTHERLY ON FRIDAY WILL ALLOW TEMPERATURES TO BE A BIT WARMER ON
FRIDAY THAN EARLIER IN THE WEEK. SOUTHERLY FLOW ALSO INTRODUCES A
CHANCE FOR THUNDERSTORMS IN THE OREGON CASCADES...MAINLY ALONG THE
CREST. THE SHIFT TO MORE SOUTHERLY WINDS OCCURS AHEAD OF A UPPER
LEVEL LOW DIGGING DOWN OUT OF ALASKA OVER THE WEEKEND... BRINGING A
CHANCE FOR SHOWERS SATURDAY AND SUNDAY. THERE IS SOME DISAGREEMENT
BETWEEN THE MODELS ON TIMING AND AMOUNT OF RAIN WITH OF THIS
SYSTEM...CREATING UNCERTAINTY WHICH SHOULD BECOME RESOLVED AS WE
APPROACH THIS WEEKEND. HAVE KEPT TEMPERATURES A BIT CLOSER TO
CLIMATOLOGY ON SATURDAY AND SUNDAY...BUT IF SYSTEM PLAYS OUT AS
FORECAST RIGHT NOW TEMPERATURES WILL LIKELY BE A BIT COOLER THAN
CURRENTLY FORECAST. -MCCOY
&&

.AVIATION...CONDITIONS EXPECTED TO REMAIN VFR ACROSS THE INTERIOR
THROUGH EARLY TUE MORNING WITH SCATTERED HIGH CLOUDS OVERHEAD. MARINE
STRATUS WILL FILTER UP THE COLUMBIA RIVER OVERNIGHT AND BRING SOME
MVFR CIGS TO THE METRO TERMINALS BETWEEN 10-18Z. MORNING CIGS WILL
SCATTER OUT AND TURN VFR TUE AFTERNOON.

MVFR STRATUS REMAINS ALONG THE NORTH COAST...WITH VFR CIGS OVER THE
CENTRAL COAST. CIGS OVER THE NORTH COAST LOOK TO SCATTER OUT BRIEFLY
THIS AFTERNOON...BUT EXPECT WIDESPREAD MVFR CIGS TO RETURN THIS
EVENING. IFR CIGS AND VSBY POSSIBLE AFTER 06Z OVER THE CENTRAL COAST.
A BRIEF PERIOD OF VFR CIGS POSSIBLE TUE AFTERNOON.

KPDX AND APPROACHES...VFR CONDITIONS WITH SCATTERED HIGH CLOUDS
THROUGH TUE MORNING. MVFR CIGS POSSIBLE BETWEEN 12-17Z. VFR
CONDITIONS RETURN TUE AFTERNOON. /64
&&

.MARINE...OUR TYPICAL SUMMERTIME PATTERN WILL CONTINUE THROUGH THE
WEEK WITH HIGH PRES OVER THE NE PAC AND LOWER PRES TO OUR S. THIS
WILL HELP MAINTAIN A PERSISTENT NORTHERLY FLOW OVER THE WATERS WITH
GUSTS GENERALLY TO 20 KT EACH AFTERNOON/EVENING. VARIATIONS IN THE
POSITION OF THE LOWER PRES COULD RESULT IN PERIODS OF GUSTY ADVISORY
LEVEL WINDS...ESPECIALLY OVER THE CENTRAL WATERS. HAVE ISSUED A SMALL
CRAFT ADVISORY FOR WIND FOR TOMORROW...WITH GUSTS TO 25 KT EXPECTED
OVER THE CENTRAL WATERS...AND FURTHER ADVISORIES MAY BE WARRANTED
THROUGHOUT THE WEEK. LOW PRES WILL APPROACH THE WATERS OVER THE
WEEKEND AND COULD BRING A BRIEF PERIOD OF WEAK SOUTHERLY WINDS.

SEAS WILL RANGE BETWEEN 4 TO 6 FT THROUGH THE FORECAST PERIOD.
HOWEVER...GUSTY AFTERNOON/EVENING WINDS COULD BRING PERIODS OF STEEP
AND CHOPPY CONDITIONS...ESPECIALLY TO THE CENTRAL WATERS. CONDITIONS
ARE EXPECTED TO REMAIN BELOW ADVISORY CRITERIA...BUT WILL NEED TO BE
MONITORED THROUGH THE WEEK AS SLIGHTLY STRONGER WINDS COULD PUSH SEAS
ABOVE 7 FT. /64
&&

.PQR WATCHES/WARNINGS/ADVISORIES...
OR...NONE.
WA...NONE.
PZ...SMALL CRAFT ADVISORY FOR WINDS FROM NOON TUESDAY TO MIDNIGHT
     PDT TUESDAY NIGHT FOR COASTAL WATERS FROM CASCADE HEAD 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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