FXUS66 KPQR 100419
AFDPQR

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE PORTLAND OR
818 PM PST WED DEC  9 2009

.SYNOPSIS...AN ARCTIC AIR MASS WILL CONTINUE THROUGH THE END OF THE
WEEK. THE BRUNT OF A PACIFIC SYSTEM IS EXPECTED TO MOVE INTO
CALIFORNIA LATE FRIDAY...WITH SOME PRECIPITATION LIKELY MOVING UP
INTO THE REGION FRIDAY NIGHT AND SATURDAY. THIS PRECIPITATION MAY
START OUT AS A LIGHT WINTRY MIX OF RAIN...SNOW OR FREEZING RAIN OVER
INLAND AREAS...WITH A WINTRY MIX POSSIBLY LINGERING INTO SATURDAY
NIGHT NEAR THE COLUMBIA GORGE. A LARGER WARMER SYSTEM IS EXPECTED FOR
EARLY NEXT WEEK.

&&

.SHORT TERM...GENERALLY A CLEAR AND COLD FORECAST FOR THIS WEEK. EAST
WINDS SHOULD BE CONFINED TO THE WESTERN GORGE AND WILL BE FAIRLY
LIGHT BY GORGE STANDARDS. THE LACK OF WIND WILL ALLOW FOR SOME GOOD
COOLING AGAIN TONIGHT. MAXIMUM TEMPS WILL BE COLD ON THU WITH ONLY
BRIEF WARMING NEAR OR SLIGHTLY ABOVE FREEZING INLAND AREAS.

THE COLD N-NW FLOW ALOFT OVER THE NW US WILL MOVE NE THU NIGHT AND
FRI ALLOWING THE AIR MASS ALOFT TO BEGIN SOME WARMING. HOWEVER THE
VALLEYS WILL BE SLOW TO SCOUR OUT. THE SOUTHERN JET STREAM PUSHING
SYSTEMS INTO CA WILL BEGIN TO LIFT N A BIT ON FRI FOR THE POSSIBILITY
OF SOME MOISTURE WITH A WARMER AIR MASS LIFTING INTO OREGON. WITH
COLD AIR IN PLACE THE ONSET OF ANY PRECIPITATION WILL MOST LIKELY BE
IN THE FORM OF FREEZING RAIN AND OR SNOW THOUGH AT THE MOMENT ANY
ACCUMULATION WILL BE ON THE LIGHT SIDE. 

THE ECMWF TAKES THE LOW INTO CALIFORNIA AND LEAVES THE PAC NW HIGH
AND DRY BUT KEEPS US COOL. THIS IS BEGINNING TO BECOME THE FAVORED
SOLUTION ESPECIALLY SINCE THE JET IS DRIVING INTO SOUTHERN CALIFORNIA
AND THERE DOES NOT SEEM TO BE MUCH SUPPORT  TO MOVE A LOW UP THE
COAST AS THE GFS SUGGESTS. FURTHER GFSENSEMBLES DO NOT INDICATE
MUCH OF A NORTHWARD PROGRESSION OF THEPRECIP...WITH ONLY A FEW
MEMBERS PULLING THE PRECIP AS FAR NORTH AS  OUR FORECAST AREA.
REGARDLESS THERE IS STILL A LOT OF UNCERTAINTYESPECIALLY
CONSIDERING THE WIDE ARRAY OF SYSTEM TRACKS...BUT THE  PROGRESSION OF
EVENTS WILL BE INTERESTING. KEEP AN EYE OUT ON THE  LOCAL FORECASTS
AS THE SITUATION COULD TURN SOUR IF THE GFS ISACCURATE. LIKENS

.LONG TERM...NO CHANGES. PREVIOUS DISCUSSION FOLLOWS...MODELS IN
DECENT AGREEMENT INTO SUN...AS SURFACE LOW PASSES INLAND TO THE S OF
FORECAST AREA. SOME MIXED PRECIPITATION INTO MAY CONTINUE IN THE N
INTO SAT NIGHT OR SUN MORNING BEFORE FLOW TURNS ONSHORE. A BIT OF A
BREAK IS POSSIBLE SUN INTO SUN NIGHT...BUT THEN MODELS DIVERGE
SIGNIFICANTLY AFTER THAT. FOR NOW WILL LEAN TOWARDS THE ECMWF 12Z
OPERATIONAL RUN WHICH HAS BEEN A LITTLE MORE CONSISTENT WITH PREVIOUS
RUNS...AND IS SUPPORTED BY THE GFS ENSEMBLE RUN. THIS INFERS HIGHER
THAN CLIMATOLOGICAL POPS WITH SOMETHING APPROACHING NORMAL TEMPS. THE
COLDER SOLUTION OF THE GFS OPERATIONAL RUN LOOKS INTERESTING...BUT
FOR NOW APPEARS TO BE SOMETHING OF AN OUTLIER.

&&

.AVIATION...GENERALLY VFR CONDITIONS THROUGH THURSDAY AS OFFSHORE 
FLOW CONTINUES FOR THE DISTRICT. THE ONLY EXCEPTION MAY BE SOME 
PATCHY BRIEF AND VERY SHALLOW FREEZING FOG IN WIND SHELTERED VALLEYS 
OF THE CENTRAL OREGON COAST RANGE AND POSSIBLY THE SOUTH WILLAMETTE 
VALLEY AS WELL. 

KPDX AND APPROACHES...VFR CONDITIONS AND LIGHT TO MODERATE EAST 
WINDS EXPECTED THROUGH THURSDAY.  WEAGLE

&&

.MARINE...THE WEST SWELL HAS COME DOWN QUITE A BIT ALREADY THIS 
EVENING...WITH ALL COASTAL BUOYS REPORTING SEAS AROUND 5 FT. EXPECT 
SEAS GENERALLY 5 FT OR LESS THROUGH AT LEAST FRIDAY...POSSIBLY 
THROUGH THE WEEKEND IF THE STORM TRACK REMAINS SOUTH OF THE AREA AS 
EXPECTED. IF THE NEXT LOW MOVES INTO NORTHERN CALIFORNIA AS 
EXPECTED...LIGHT TO MODERATE E-NE WINDS WOULD PREVAIL THROUGH SAT 
THEN BACK MORE N-NW AS THE LOW MOVES INLAND SUN. MUCH OF THE SWELL 
ENERGY FROM THIS SYSTEM WOULD STAY SOUTH OF THE OREGON WATERS AND 
IMPACT MAINLY CALIFORNIA...AND CURRENT FORECAST REFLECTS THIS WELL.  
WEAGLE

&&

.PQR WATCHES/WARNINGS/ADVISORIES...
OR/WA...NONE.

&&

$$

MORE WEATHER INFORMATION ONLINE AT...
HTTP://WEATHER.GOV/PORTLAND

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.