Area Forecast Discussion
Issued by NWS Portland, OR

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FXUS66 KPQR 261120
AFDPQR

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE PORTLAND OR
320 AM PST WED NOV 26 2014

.SYNOPSIS...A WARM FRONTAL BOUNDARY HAS MOSTLY LIFTED NORTH OF OUR
FORECAST AREA EARLY THIS MORNING...WITH JUST A LITTLE LIGHT
PRECIPITATION BRUSHING SOUTHWEST WASHINGTON...AND MILD AND DRY
WEATHER FOR THE REST OF THE AREA EXCEPT SOME LOCAL MORNING FOG. THE
ASSOCIATED COLD FRONT WILL REACH THE COAST AND START TO MOVE ONSHORE
TONIGHT...SPREADING ACROSS ALL OF THE AREA ON THANKSGIVING. LOOK FOR
RAIN AND COASTAL WIND. A SECONDARY COLDER COLD FRONT WILL DROP SOUTH
ACROSS SOUTHWEST WASHINGTON AND NORTHWEST OREGON FOR MORE RAIN ON
FRIDAY. MUCH COOLER AIR ASSOCIATED WITH THE NORTHERN BRANCH OF THE
JET STREAM IS FORECAST TO SPREAD OVER THE AREA THIS WEEKEND...FOR
ANOTHER ROUND OF EAST WIND IN THE COLUMBIA RIVER GORGE. SNOW LEVELS
WILL LOWER DRAMATICALLY THIS WEEKEND...BUT SLOWLY RISE EARLY NEXT
WEEK.
&&

.SHORT TERM...TODAY THROUGH FRIDAY...THE NATIONAL WEATHER SERVICE
DOPPLER RADAR IS RATHER QUIET EARLY THIS MORNING...WITH JUST SOME
RESIDUAL LIGHT PRECIPITATION OVER PARTS OF SOUTHWEST WASHINGTON. THE
MAIN WARM FRONT HAS LIFTED WELL NORTH OF THE AREA...LEAVING SOUTHWEST
WASHINGTON AND NORTHWEST OREGON IN THE VERY MILD WARM SECTOR. MOST OF
THE AREA WILL BE DRY TODAY AND AGAIN QUITE MILD... AND A FEW RECORDS
MAINLY IN THE NORTH WILL BE IN REACH AGAIN TODAY. WE MAY ALSO SEE
LOCAL FOG THIS MORNING AS DEWPOINTS ARE MOSTLY IN THE LOWER 50S.

THE ASSOCIATED COLD FRONT APPROACHING 130W EARLY THIS MORNING WILL
REACH THE COAST AND BEGIN SPREADING ONSHORE TONIGHT FOR MORE RAIN AND
SOME BRISK COASTAL WINDS...BUT LIKELY STAYING BELOW HIGH WIND
CRITERIA. THE FRONT WILL CONTINUE MOVING THROUGH THE FORECAST AREA ON
THANKSGIVING FOR MORE RAIN AND LOCALLY BREEZY CONDITIONS. SNOW LEVELS
WILL REMAIN QUITE HIGH IN THE CASCADES.

THE FRONTAL BOUNDARY WILL STALL OVER THE AREA THURSDAY NIGHT BENEATH
CONFLUENT FLOW ALOFT AS THE SOUTHERN BRANCH OF THE JET MERGES WITH AN
INCREASING NORTHERN BRANCH OF THE JET. THIS WILL KEEP SOME RAIN GOING
OVER MUCH OF THE AREA THURSDAY NIGHT.

A SECONDARY COLDER COLD FRONT WILL BEGIN SAGGING INTO OUR AREA FROM
THE NORTH ON FRIDAY...MERGING WITH THE STALLED SOUTHERN COLD
FRONT...AND KEEPING THE RAIN GOING...PERHAPS A LITTLE HEAVIER THAN ON
PREVIOUS DAYS. SNOW LEVELS IN THE SOUTH WASHINGTON CASCADES MAY BEGIN
TO FALL LATE IN THE DAY AS THIS SECONDARY COLD FRONT MOVES SOUTH BUT
SNOW LEVELS WILL GENERALLY STAY ABOVE THE PASS LEVELS THROUGH FRIDAY.
TOLLESON

.LONG TERM...NO CHANGES. PREVIOUS DISCUSSION FOLLOWS...
FRIDAY NIGHT THROUGH TUESDAY...COMPLICATED PATTERN EVOLVES FRIDAY
NIGHT AND SAT WITH THE COLDER AIR CONTINUING TO SLIDE S THROUGH WA
AND INTO NRN OREGON. 12Z GFS MORE IN LINE WITH THE PREVIOUS COUPLE OF
ECMWF RUNS...DEPICTING A COLD AIR WEDGE IN THE CENTRAL COLUMBIA GORGE
BY 00Z SUN. LOOK FOR THE EAST WIND TO RETURN AS WELL...BEGINNING SAT
MORNING AND CONTINUING THROUGH THE WEEKEND. BY 00Z SUN THE GFS HAS -8
TO -10C 850 MB AIR IN THE CENTRAL COLUMBIA GORGE...WHILE THE ECMWF IS
JUST A TOUCH WARMER. FORTUNATELY...THE DRIER NLY FLOW WILL SHUNT
PRECIP FURTHER TO THE S. A CLOSED LOW WELL OF THE NRN CA COAST SAT
STARTS TO DRIFT NE SAT NIGHT AND SUN. THERE IS THE POTENTIAL FOR A
DEFORMATION BAND OVER NRN CA TO DRIFT NWD LATE SUN INTO MON. THIS
COULD BE PROBLEMATIC AS THE MOISTURE OVERRUNS THE COLD
AIR....ESPECIALLY FOR THE COLUMBIA GORGE AND UPPER HOOD RIVER VALLEY.
WEISHAAR
&&

.AVIATION...LIFR TO IFR CONDITIONS ON THE COAST SHOULD IMPROVE LATER
THIS MORNING AS PRESSURE GRADIENTS TURN SLIGHTLY MORE OFFSHORE.
INCREASING WINDS AND A NOSE OF DRIER AIR ALOFT MAY ALLOW CONDITIONS
TO EVEN TEMPORARILY IMPROVE TO VFR LATE THIS AFTERNOON AND EVENING
BEFORE CONDITIONS DETERIORATE AS A COLD FRONT...LOW CLOUDS AND RAIN
IMPACT THE COAST TOWARDS 12Z THURSDAY. FURTHER INLAND...MOST
LOCATIONS SHOULD REMAIN IN THE WARM SECTOR TODAY...WHICH SHOULD
PRODUCE VFR CONDITIONS THIS AFTERNOON THROUGH 12Z THURSDAY. IN THE
MEANTIME...A STRATUS DECK NEAR 5KFT IS CURRENTLY RESIDING ACROSS THE
WILLAMETTE VALLEY. MODELS SUGGEST IT WILL BEGIN TO CLEAR FROM
SOUTHWEST TO NORTHEAST THROUGH 18Z WEDNESDAY. GIVEN LOW DEWPOINT
DEPRESSIONS AND LITTLE WIND EARLY THIS MORNING...ANY LOCATIONS THAT
CLEAR WILL LIKELY DETERIORATE RAPIDLY. THIS APPEARS MOST LIKELY AT
KEUG AND KSLE...BUT THESE LOWER FLIGHT CONDITIONS COULD SNEAK INTO
THE PORTLAND METRO TOWARDS 15Z WEDNESDAY.

KPDX AND APPROACHES...VFR CONDITIONS EARLY THIS MORNING MAY GIVE WAY
TO MVFR OR LOWER CONDITIONS TOWARDS 15Z WEDNESDAY...BUT CONFIDENCE IS
DETERIORATING THESE LOWER FLIGHT CONDITIONS WILL MATERIALIZE.
REGARDLESS...VFR CONDITIONS SHOULD BE THE DOMINANT PLAYER THIS
AFTERNOON THROUGH 12Z THURSDAY. /NEUMAN
&&

.MARINE...AN INCOMING FRONTAL STORM SYSTEM WILL CAUSE WINDS TO
INCREASE TODAY. EXPECT PRIMARILY SMALL CRAFT ADVISORY LEVEL WIND
GUSTS TO 30 KT. HOWEVER...A WEAK COASTAL JET WILL LIKELY ENHANCE WIND
SPEEDS WITHIN 20 NM OF THE COAST BEGINNING LATE THIS AFTERNOON AND
LASTING THROUGH MUCH OF THE NIGHT. THIS SHOULD ALLOW GALE FORCE WIND
GUSTS OF 35 KT TO SURFACE ACROSS THE WATERS. THE HIGHEST WINDS APPEAR
ON TRACK FOR THE 7 PM WEDNESDAY TO 1 AM THURSDAY TIME FRAME. DUE TO
INHERENT UNCERTAINTY IN THESE SITUATIONS WILL KEEP THE TIMING OF THE
GALE WARNING AS IS.

PRESSURE GRADIENTS WILL REMAIN ELEVATED BEHIND THE FRONTAL STORM
SYSTEM SO EXPECT PERIODS OF SMALL CRAFT ADVISORY LEVEL WIND GUSTS OF
25 TO 30 KT THURSDAY AND THURSDAY NIGHT. A COUPLE WEAK LOW PRESSURES
TO OUR WEST MAY KEEP GUSTY WINDS AND HAZARDOUS SMALL CRAFT SEAS IN
THE LOWER TEENS GOING THROUGH MUCH OF FRIDAY. HOWEVER...A FRONT
SLIDING NORTH TO SOUTH ACROSS THE WATERS SHOULD ALLOW WINDS AND SEAS
TO RELAX FRIDAY OR SATURDAY...WITH THE EXACT TIMING OF WHEN THE FRONT
WILL MOVE ACROSS THE WATERS SOMEWHAT UNCERTAIN. NONETHELESS... WINDS
SHOULD TURN MORE OFFSHORE OVER THE WEEKEND...WITH GUSTY WINDS LIKELY
DEVELOPING NEAR COASTAL GAPS SUCH AS THE MOUTH OF THE COLUMBIA RIVER
AND NEAR TILLAMOOK. /NEUMAN
&&

.PQR WATCHES/WARNINGS/ADVISORIES...
OR...NONE.
WA...NONE.
PZ...SMALL CRAFT ADVISORY FOR WINDS FROM 4 AM EARLY THIS MORNING
     TO 4 PM PST THIS AFTERNOON FOR COASTAL WATERS FROM CAPE
     SHOALWATER WA TO FLORENCE OR OUT 60 NM.

     GALE WARNING FROM 4 PM THIS AFTERNOON TO 4 AM PST THURSDAY FOR
     COASTAL WATERS FROM CAPE SHOALWATER WA TO FLORENCE OR OUT
     60 NM.

     SMALL CRAFT ADVISORY FOR ROUGH COLUMBIA RIVER BAR FROM 5 AM TO
     9 AM PST THIS MORNING.

     SMALL CRAFT ADVISORY FOR ROUGH COLUMBIA RIVER BAR FROM 4 PM
     THIS AFTERNOON TO 10 AM PST THURSDAY.

&&

$$

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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