Area Forecast Discussion
Issued by NWS Portland, OR

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FXUS66 KPQR 030444
AFDPQR

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE PORTLAND OR
944 PM PDT TUE SEP  2 2014

.SYNOPSIS...THE STRONGEST PACIFIC COLD FRONT IN QUITE SOME TIME HAS
MOVED THROUGH MOST OF SOUTHWEST WASHINGTON AND NORTHWEST OREGON THIS
EVENING...AND WILL FINISH MOVING EAST OF THE CASCADES OVERNIGHT.
ONSHORE FLOW IN THE COOLER AIR BEHIND THE FRONT WILL SPREAD IN SOME
BROKEN UP CLOUDS OVERNIGHT. AN UPPER LEVEL RIDGE WILL BEGIN TO BUILD
IN OVER THE FORECAST AREA WEDNESDAY FOR CLEARING LATER IN THE
AFTERNOON...THEN BUILD IN OVER THE AREA IN A MORE EARNEST FASHION FOR
THURSDAY THROUGH SATURDAY...PRODUCING THE FIRST OFFSHORE LOW LEVEL
FLOW EVENT FOR THE LATE SUMMER OR EARLY FALL. THE STRENGTHENING
OFFSHORE WINDS WILL ALLOW TEMPERATURES TO RISE INTO THE UPPER 80S AND
LOWER 90S FOR MANY INLAND LOCATIONS LATE IN THE WORK WEEK. THERE IS A
CHANCE ANOTHER STORM SYSTEM COULD BRING A CHANCE FOR LIGHT RAIN
SHOWERS TO THE AREA EARLY NEXT WEEK.
&&

.SHORT TERM...TONIGHT THROUGH FRIDAY...THE STRONGEST PACIFIC COLD
FRONT IN QUITE SOME TIME SWUNG INTO SOUTHWEST WASHINGTON AND
NORTHWEST OREGON LATE THIS AFTERNOON AND EVENING...AND WAS IN THE
SOUTHERN SECTIONS OF THE FORECAST AREA THIS EVENING. IT BROUGHT
SPOTTY LIGHT PRECIPITATION...A FEW HUNDREDTHS NEAR THE COAST AND OVER
THE NORTHERN COAST RANGE AND CASCADES...AND A TRACE TO OUR OFFICE IN
A FEW SPRINKLES. IT ALSO USHERED IN A FAIRLY SIGNIFICANT MARINE PUSH
WITH GUSTY WEST WINDS...WINDS THAT GUSTED TO 20 OR EVEN 30 MPH IN
SOME AREAS...WITH AROUND 40 MPH AT THE DALLES.

THE TRAILING ONSHORE FLOW BEHIND THE FRONT WILL CONTINUE TONIGHT INTO
WEDNESDAY. THE LOW CLOUDS ARE BROKEN UP OFF THE COAST DUE TO THE
COOLER AIR ASSOCIATED WITH THIS SYSTEM AND THE LACK OF A SIGNIFICANT
MARINE INVERSION...SO EXPECT CLOUDS OVERNIGHT THAT SPREAD IN WILL
HAVE A LOT OF HOLES. THIS SHOULD ALLOW TEMPS OVERNIGHT TO BE
RELATIVELY COOL AS WELL...PERHAPS A FEW OF OUR COOLER VALLEY
LOCATIONS MAY DROP INTO THE UPPER 40S.

THE BACK SIDE OF THE ASSOCIATED UPPER TROUGH WILL LINGER OVER THE
PACIFIC NORTHWEST THROUGH TONIGHT AND THROUGH MUCH OF WEDNESDAY. THE
EXPECTED BROKEN UP LOW CLOUDS THAT SPREAD IN OVERNIGHT WILL TEND TO
STAY BROKEN UP ON WEDNESDAY...BUT OVERTURNING ONCE THE SUN COMES OUT
MAY MAKE THEM THE MOST SOLID THEY WILL BE ON WEDNESDAY MORNING. THE
LINGERING TROUGH WILL SLOW THE CLEARING PROCESS ON WEDNESDAY...AND
EXPECT THEM TO LINGER ESPECIALLY IN THE NORTHERN FORECAST ZONES INTO
THE EARLY OR MID AFTERNOON.

THE TRAILING UPPER RIDGE MOVES IN MORE SIGNIFICANTLY WEDNESDAY NIGHT
AND THURSDAY...BUT NORTH TO NORTHWEST FLOW ALOFT STILL LINGERS OVER
THE AREA THURSDAY. WEDNESDAY NIGHT INTO THURSDAY WILL BE ANOTHER COOL
NIGHT/MORNING.. BUT THE OFFSHORE GRADIENTS SLOWLY BEGIN TO PICK UP
ESPECIALLY THROUGH THE GORGE AND OVER THE HIGHER TERRAIN. THE MODELS
SUGGEST SOME PATCHY FOG OR LOW CLOUDS WILL HAVE A CHANCE TO FORM
AGAIN ALONG THE COAST AND LOCALLY INLAND LATER WEDNESDAY NIGHT AND
THURSDAY MORNING BEFORE THE OFFSHORE GRADIENTS KICK IN ON THURSDAY.

THIS FIRST LATE SUMMER/EARLY FALL OFFSHORE WIND EVENT WILL CONTINUE
TO INCREASE THURSDAY NIGHT AND FRIDAY. WIND SHELTERED AREAS WILL HAVE
ANOTHER COOL NIGHT THURSDAY NIGHT...THOUGH WINDS IN MANY AREAS WILL
KEEP THOSE AREAS MILD.

850 MB TEMPS SUGGEST THE WARMING WILL BE IN TWO STEPS...WITH MID TO
UPPER 80S ON THURSDAY...AND LOWER TO MID 90S ON FRIDAY. THE COAST HAS
A CHANCE OF SOME 80S ON FRIDAY AS WELL. TOLLESON

.LONG TERM...SATURDAY THROUGH TUESDAY...THERE IS AT LEAST ONE MORE
VERY WARM DAY ON SATURDAY...WITH THE OFFSHORE FLOW EVENT CONTINUING.
THE THERMAL TROUGH IS OFF THE COAST SATURDAY MORNING...SO EVEN THE
COAST LOOKS QUITE WARM STILL ON SATURDAY. OTHERWISE...A REX-LIKE
WEATHER PATTERN WITH A RIDGE POSITIONED NORTH OF A TROUGH IS FORECAST
TO MOVE ONSHORE AS THE RIDGE STARTS TO BREAK DOWN SATURDAY NIGHT AND
SUNDAY. THE LONG WAVE TROUGH WILL BE OUR NEXT WEATHER-MAKER WHEN THE
RIDGE WEAKENS ENOUGH TO ALLOW THE LOW-PRESSURE SYSTEM ONSHORE...WHICH
THE ECMWF...GFS... AND DGEX AGREE SHOULD BE SOMETIME LATE SUNDAY
NIGHT OR EARLY MONDAY MORNING. RAINFALL WITH THIS SYSTEM WILL START
AT THIS TIME...AND THE UNSTABLE NORTHWESTERLY FLOW PATTERN THAT SETS
UP BEHIND THIS SYSTEM BRING CONTINUED CHANCES OF RAIN THROUGH TUESDAY
WITH A LOT OF UNCERTAINTY ON TIMING AND LOCATION. -MCCOY/TOLLESON
&&

.FIRE WEATHER...ON THE FIRE WEATHER FRONT...POOR NIGHT TIME RELATIVE
HUMIDITY RECOVERIES AND MODEST EAST WINDS ACROSS THE CASCADES AND
COAST RANGE WILL ENHANCE FIRE WX CONCERNS THE LATTER PART OF THE
WEEK. TW
&&

.AVIATION...MOSTLY VFR CONDITIONS THIS EVENING IN THE WAKE OF THE
COLD FRONT THAT PASSES ACROSS THE AREA. WINDS PICKED UP BEHIND THE
FRONT BUT WITH SUNSET THE WINDS ALOFT HAVE BECOME DECOUPLED FROM
THE SURFACE WINDS AND THE SURFACE WINDS ARE DIMINISHING. EXPECT
STRATOCU CLOUDS TO CONTINUE ALONG THE WINDWARD SLOPES OF THE COAST
RANGE AND THE CASCADES AND FOOTHILLS TONIGHT WITH MOSTLY SCATTERED
OR CLEAR OVER THE INTERIOR VALLEYS. THESE CLOUDS MAY FILL IN SOME
10Z-15Z BUT GENERALLY EXPECT VFR CONDITIONS AT MOST OF THE
TERMINALS UNTIL ABOUT 14Z AND THEN SOME MVFR CIGS OVER THE VALLEY
THROUGH ABOUT 19-20Z WHEN THE CLOUDS SHOULD BREAK UP. ALONG THE
COAST EXPECT SOME MVFR CIGS TO REDEVELOP 12-15Z AND THEN VFR
CONDITIONS AFTER 18Z. SCHNEIDER

KPDX AND APPROACHES...VFR CONDITIONS WITH SOME MVFR CIGS EXPECTED
14Z TO 18Z...IMPROVING TO MVFR CIGS FOR A FEW HOURS THEN CLEARING
IN THE AFTERNOON. SCHNEIDER
&&

.MARINE...BRISK NORTHWEST WINDS DEVELOPED AS HIGH PRESSURE BUILT
IN BEHIND THE COLD FRONT WHICH MOVED ACROSS THE WATERS THIS
AFTERNOON AND EVENING. SMALL CRAFT ADVISORY WAS ISSUED FOR THE
WATERS NORTH OF CASCADE HEAD AS A RESULT. THE GRADIENT SHOULD
RELAX SOME TOMORROW AND WINDS WILL EASE DURING THE LATE MORNING
AND EARLY AFTERNOON. THESE WINDS GENERATED A FRESH SWELL WITH
STEEP SEAS OVER THE NORTHERN WATERS AND HAVE ISSUED A SMALL CRAFT
ADVISORY FOR HAZARDOUS SEAS. THESE LOCALLY GENERATED SEAS ARE
BEING ENHANCED BY SOME NORTHWEST SWELL COMING OUT OF THE GULF OF
ALASKA. A TRICKY FORECAST FOR THE COLUMBIA RIVER BAR TONIGHT AS
THE FRESH SWELL OF THIS SHORT PERIODS...6-7 SECONDS DOES NOT
NORMALLY LEND ITSELF TO BUILDING ROUGH CONDITIONS ON THE BAR BUT
THERE IS ALSO INCREASING NORTHWEST SWELL AROUND 9 TO 10 SECONDS
SHOWN IN THE ENP MODEL TO CONSIDER. AS A RESULT HAVE DECIDED TO
ISSUE A SMALL CRAFT FOR ROUGH BAR CONDITIONS. SCHNEIDER

FROM WED THROUGH THE SECOND HALF OF THE WEEK...N-NW WINDS CONTINUE
AS HIGH PRES REBUILDS IN OFFSHORE AND A THERMAL LOW PRES OVER
CALIFORNIA EXTENDS N INTO OREGON. GUSTS UP TO 20-25 KT ARE
POSSIBLE OVER THE CENTRAL OREGON WATERS WED...AND APPEAR LIKELY
OVER ALL WATERS THU AND FRI. MEANWHILE...SEAS WILL BUILD TO 7 TO
9 FT...DOMINATED BY A COMBINATION OF WIND WAVE AND FRESH SWELL.
FORECAST MODELS KEEP SEAS BELOW 10 FT...BUT WILL NEED TO MONITOR
TRENDS AS STRONGEST WINDS MAY BUILD SEAS INTO THE 9 TO 11 FT
RANGE. WINDS LOOK TO EASE BY SUN AS HIGH PRES IN NE PAC WEAKENS
AND THERMAL LOW PRES SHIFTS INLAND. CULLEN
&&

.PQR WATCHES/WARNINGS/ADVISORIES...
OR...NONE.
WA...NONE.
PZ...SMALL CRAFT ADVISORY FOR WINDS UNTIL 11 AM PDT WEDNESDAY FOR
     WATERS FROM CAPE SHOALWATER WA TO CASCADE HEAD OR FROM 10
     TO 60 NM.

     SMALL CRAFT ADVISORY FOR HAZARDOUS SEAS UNTIL 11 AM PDT
     WEDNESDAY FOR COASTAL WATERS FROM CAPE SHOALWATER WA TO CASCADE
     HEAD OR OUT 60 NM.

     SMALL CRAFT ADVISORY FOR WINDS UNTIL 5 AM PDT WEDNESDAY FOR
     COASTAL WATERS FROM CAPE SHOALWATER WA TO CASCADE HEAD OR
     OUT 10 NM.

     SMALL CRAFT ADVISORY FOR ROUGH COLUMBIA RIVER BAR UNTIL 2 PM
     PDT WEDNESDAY.

&&

$$

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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