FXUS66 KPQR 101704
AFDPQR

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE PORTLAND OR
904 AM PST THU DEC 10 2009

.SYNOPSIS...AN ARCTIC AIR MASS WILL CONTINUE THROUGH THE THE EARLY
PART OF THE WEEKEND. THE BRUNT OF A PACIFIC SYSTEM IS EXPECTED TO
MOVE INTO CALIFORNIA LATE FRIDAY AND SLOWLY TRANSITION SOME
PRECIPITATION BANDS NORTH OVER THE COLD AIR AND PRECIPITATION WILL
LIKELY FALL AS A COMBINATION OF FREEZING RAIN...SNOW AND RAIN
DEPENDING ON WHERE YOU LIVE. A LARGER WARMER SYSTEM IS EXPECTED FOR
EARLY NEXT WEEK.

&&

.SHORT TERM...ANOTHER COLD NIGHT LAST NIGHT...WITH MULTIPLE 
LOCATIONS RUNNING UP TO 4 DEGREES COOLER THAN THIS TIME YESTERDAY 
MORNING. AFTERNOON HIGHS TODAY MAY ALSO BE 1-2 DEGREES LOWER SO I
ADJUSTED THOSE AS WELL. THOUGH IT SHOULD BE A FEW DEGREES WARMER
TONIGHT...NO AIR MASS CHANGE TAKES PLACE SO EXPECT WE WILL ONCE AGAIN
DROP INTO THE TEENS TONIGHT AND FRI MORNING.

ONTO THE REAL CONCERN IN THE NEXT FEW DAYS. NEXT SYSTEM PUSHES INTO
CALIFORNIA ON FRI...MODELS AGREE IN WANTING TO BRING ENERGY WITH THAT
SYSTEM NORTHWARD ACROSS THE FORECAST AREA. TIMING AND PRECIP TYPE
REMAIN ISSUES WITH THIS FEATURE...WITH THE ECMWF...NAM AND CANADIAN
FAVORING A SLOWER AND MORE SOUTHERN SOLUTION WITH SYSTEM AND THUS A
SLOWER NORTHWARD PROGRESSION OF THE PRECIP INTO OUR AREA. ONCE AGAIN
THE GFS IS THE OUTLIER BUT HAS BEEN EXTREMELY CONSISTENT WITH REGARD
TO TIMING THUS WILL NOT COMPLETELY RULE IT OUT. SHOULD SEE PRECIP
BEGIN TO MOVE INTO THE SOUTHERN CWA BY FRI AFTERNOON OR EVENING IN
THE SOUTH VALLEY. OVERALL SURFACE FLOW WILL BE WEAK AND WILL LIKELY
NOT SCOUR OUT THE COLD AIR IN THE VALLEY THUS A POTENTIAL FOR A
EVERYTHING FROM FREEZING RAIN TO SNOW. AMOUNTS OF EACH ARE ALSO IN
QUESTION AS THE BULLISH GFS BRINGS UP TO 0.40 INCHES OVER THE NORTH
VALLEY AND IF FALLING IN THE FORM OF SNOW OR FZRA WILL CAUSE GREAT
CONCERN ON THE OTHER HAND MOST MODELS ONLY BRING ABOUT A TENTH OF AN
INCH OF QPF OVER THE AREA WHICH WOULD STILL CAUSE PROBLEMS. THE
WRFGFS DUMPS NEARLY 4 INCHES OF SNOW ON THE EASTERN COAST RANGE
FOOTHILLS AGAIN ANOTHER POSSIBILITY THAT IS NOT OUT OF THE QUESTION.
IT WILL BE EXTREMELY INTERESTING TO SEE HOW THIS PLAYS OUT AND
THEREFORE GIVEN THE UNCERTAINTY THAT STILL EXISTS. FOR NOW FORECAST
WILL TREND TO A BRIEF PERIOD OF FZRA FOR SOUTH VALLEY...CENTRAL
VALLEY GETS A GOOD DOSE OF FZRA...NORTH VALLEY GETS SOME SNOW AND
FZRA...GORGE GETS SNOW THEN FZRA...AND FOOTHILLS GENERALLY GET FZRA
WITH THE EASTERN ASPECT WEST OF HILLSBORO GETTING SOME
SNOW...WASHINGTON COUNTY AREA. PLEASE PAY CLOSE ATTENTION TO THE
PROGRESSION OF THIS SCENARIO AS THEIR STILL IS QUITE A BIT OF
UNCERTAINTY IN TIMING...PRECIP TYPE...AND PRECIP AMOUNTS.

CURRENTLY DRAFTING UP WINTER STORM WATCHES FOR MOST OF THE FORECAST
AREA INCLUDING THE WILLAMETTE VALLEY. 

WOLFE

.LONG TERM...TIMING OF FEATURES ARE DIFFERENT AMONGST VARIOUS MODELS
IN THE EXTENDED...AS IS USUAL...HOWEVER THE OVERALL TREND IS A MORE
PROGRESSIVE AND WET PATTERN BEGINNING EARLY NEXT WEEK. SHOULD SEE
TEMPS RETURN TO MORE NORMAL VALUES AND WILL LIKELY SEE A 2-3 FRONTS
MAKE THEIR WAY THROUGH THE AREA THROUGHOUT NEXT WEEK...WITH POSSIBLY
A BREAK IN THE RAIN CLOSER TO NEXT WEEKEND.  DALTON

&&

.AVIATION...OFFSHORE FLOW AND DRY AIR MASS WILL CONTINUE VFR 
CONDITIONS. VERY SHALLOW FREEZING GROUND FOG POSSIBLE IN WIND 
SHELTERED VALLEYS OF THE CENTRAL OREGON COAST RANGE AND THE SOUTH 
WILLAMETTE VALLEY THIS MORNING.

KPDX AND APPROACHES...VFR CONDITIONS FOR NEXT 24 HRS. LIGHT WINDS 
THROUGH MID MORNING THEN MODERATE EAST WINDS FROM THE GORGE WILL
REACH KPDX. RUTHFORD

&&

.MARINE...OFFSHORE FLOW IS KEEPING THINGS QUIET OVER THE WATERS WITH 
EAST WINDS AROUND 15 KT AND WEST SWELL 5 TO 6 FEET. SEAS WILL DROP 
TO 3 TO 4 FT AND REMAIN IN THAT RANGE THROUGH SAT. WITH THE NEXT LOW 
TRACKING SOUTH OF THE AREA AND INTO NORTHERN CALIFORNIA...LIGHT TO 
MODERATE E TO NE WINDS WILL PREVAIL THROUGH SAT THEN BACK MORE N TO 
NW AS THE LOW MOVES INLAND SUN. MUCH OF THE SWELL ENERGY FROM THIS 
SYSTEM WILL STAY SOUTH OF OREGON. SOUTHERLY WINDS OF 25 TO 30 KT 
WILL RETURN TO THE AREA MON OR TUE AS THE JET STREAM LIFTS NORTH. 
RUTHFORD

&&

.PQR WATCHES/WARNINGS/ADVISORIES...
OR...WINTER STORM WATCH FROM FRIDAY EVENING THROUGH SATURDAY 
     AFTERNOON FOR COAST RANGE OF NORTHWEST OREGON-GREATER 
     PORTLAND METRO AREA-LOWER COLUMBIA-NORTHERN OREGON CASCADE 
     FOOTHILLS-UPPER HOOD RIVER VALLEY-WESTERN COLUMBIA RIVER 
     GORGE.

     WINTER STORM WATCH FROM FRIDAY AFTERNOON THROUGH LATE FRIDAY 
     NIGHT FOR CASCADE FOOTHILLS IN LANE COUNTY-CENTRAL COAST 
     RANGE OF WESTERN OREGON-SOUTH WILLAMETTE VALLEY.

     WINTER STORM WATCH FROM FRIDAY AFTERNOON THROUGH SATURDAY 
     AFTERNOON FOR CENTRAL WILLAMETTE VALLEY.

WA...WINTER STORM WATCH FROM FRIDAY EVENING THROUGH SATURDAY 
     AFTERNOON FOR GREATER VANCOUVER AREA-I-5 CORRIDOR IN 
     COWLITZ COUNTY-SOUTH WASHINGTON CASCADE FOOTHILLS-WESTERN 
     COLUMBIA RIVER GORGE.

PZ...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.