405 
FXUS66 KPQR 211718
AFDPQR

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE PORTLAND OR
917 AM PST SAT NOV 21 2009

...UPDATED FOR HIGH WIND WATCH AND POSSIBLE WIND ADVISORY IN THE
WILLAMETTE  VALLEY TONIGHT...

.SYNOPSIS...A WARM FRONT WILL APPROACH THE OREGON COAST THIS
AFTERNOON THEN PUSH INLAND THIS EVENING. A COLD FRONT WILL QUICKLY
FOLLOW TONIGHT AS A SURFACE LOW PRESSURE SYSTEM MOVES INLAND NEAR THE
WA OREGON BORDER. A WEAK RIDGE OF HIGH PRESSURE WILL FOLLOW SUN
AFTERNOON AND NIGHT...BEFORE THE NEXT FRONTAL SYSTEM ARRIVES MON.
&&

.SHORT TERM...LATEST MODEL RUNS CONTINUE TO EXHIBIT DIFFERENCES IN
TRACK OF THE SURFACE LOW COMING IN TONIGHT. UPPER FEATURES APPEAR
PRETTY WELL AGREED ON...WITH A STRONG SHORTWAVE MOVING ACROSS THE
FORECAST AREA TONIGHT...DIGGING TO THE ESE. GIVEN THE TRACT OF THE
UPPER VORT MAX AND THE NEGATIVE TILT OF THE UPPER TROUGH...CONTINUE
TO PREFER A MORE SOUTHERLY TRACK OF THE SURFACE LOW...AS SUCH PREFER
THE 00Z RUN OF THE ECMWF WHICH TAKES A SURFACE LOW E ROUGHLY ACROSS
KKLS AT 12Z SUN. TIMING OF THE COLD FRONT IN ALL MODELS INDICATES
FRONTAL PASSAGE ON THE COAST NOT UNTIL SOMETIME TONIGHT. GIVEN THE
CONTINUED UNCERTAINTIES IN THE MODELS...WILL EXTEND THE HIGH WIND
WATCH FOR THE N AND CENTRAL OREGON COAST TO INCLUDE THE SOUTHERN 
WASHINGTON COAST...AND EXTEND IT TILL 6AM. WINDS INLAND LOOK GUSTY
WITH AND BEHIND THE FRONT AS THERE ARE STRONG PRESSURE RISES BEHIND
THE FRONT...EXPECT AN ADVISORY FOR SOME PORTION OF THE WILLAMETTE
VALLEY FOR LATE TONIGHT WILL BE NEEDED...WILL PROBABLY ISSUE WITH
AFTERNOON PACKAGE.

DOPPLER RADAR CONTINUES TO SHOW SHOWERS SPREADING OVER MOST OF THE
FORECAST AREA THIS MORNING AS WESTERLY FLOW ALOFT FOLLOWS THE UPPER
TROUGH. WITH UPPER RIDGING LATER TODAY...AND LOW LEVEL FLOW BACKING
MORE TO THE S...SHOULD SEE SHOWERS DROP OFF TODAY. OVERNIGHT SNOWFALL
AMOUNTS IN THE CASCADES SINCE LAST EVENING HAVE RANGED FROM ROUGHLY 4
TO 9 INCHES. FOR NOW WILL HANG ONTO THE SNOW ADVISORY FOR THE N 
OREGON AND S WA CASCADES TODAY...ALTHOUGH WILL LIKELY SEE A 
SIGNIFICANT DROPOFF IN SNOWFALL LATER THIS MORNING. WILL CONTINUE 
THE WINTER STORM WARNING FOR THE CASCADES AS MOISTURE...STRENGTH OF 
THE FRONT AND THE POST FRONTAL FLOW ALL FAVOR SIGNIFICANT SNOWFALL 
LATER TONIGHT AND SUN.

CURRENT MODEL RUNS INDICATE BEST CHANCES FOR PRECIPITATION MONDAY
WILL SHIFT N INTO WA WITH WARM FRONT OVERRUNNING. THE UPPER RIDGE
HOLDS COLD FRONT AT BAY UNTIL MON NIGHT. LIKENS

.LONG TERM...NO CHANGES. PREVIOUS DISCUSSION FOLLOWS...WEAK HIGH PRES
BUILDS OVER THE FORECAST AREA MON NIGHT. MODELS SHOW A WEAK SYSTEM
APPROACH THE COAST EARLY TUE...BUT IT TRACKS FURTHER NORTH AND
LIGHTLY BRUSHES THE FAR NORTHWEST CORNER OF THE CWA. THIS RIDGE IS
MORE PERSISTENT THAN PREVIOUS MODEL RUNS SUGGESTED. IT MANAGES TO
DELAY THE ARRIVAL OF A SECOND SYSTEM THROUGH THUR. BY MID NEXT
WEEK...MODELS DISAGREE ON THE SOLUTION FOR THE WEEKEND. GFS MODEL
RUNS ARE INCONSISTENT...THE 06Z RUN HELD BACK ON PRECIP THROUGH THURS
NIGHT BUT THE CURRENT RUN SHOWS RAIN EXTENDING TO THE CASCADES THURS
NIGHT. SO FAR...MODELS SUGGEST A FAIRLY NICE WEEKEND AS ANOTHER UPPER
HIGH PRES TEMPORARILY SETS UP OVER THE PAC NW. LRAMIREZ

&&

.AVIATION...LITTLE CHANGE IN OVERALL CONDITIONS THIS MORNING. 
PREDOMINATELY VFR WITH SCATTERED SHOWERS...WHICH MAY BRING VERY 
BRIEF MVFR CIGS. CONDITIONS REMAIN VFR THROUGH TODAY...THOUGH WILL 
SEE INCREASING MVFR ALONG THE COAST AFTER 20Z AS WARM FRONT SWINGS 
ACROSS THE REGION. COLD FRONT TONIGHT WILL BRING INCREASING MVFR 
AFTER 04Z...AND INCREASING SOUTHERLY WINDS. 

KPDX AND APPROACHES...VFR CONDITIONS THROUGH 05Z...THEN INCREASING 
MVFR CIGS AS COLD FRONT APPROACHES. WATCH FOR POTENTIAL OF LOW LEVEL 
WIND SHEAR BETWEEN 00Z AND 06Z TONIGHT AS WILL SEE INCREASING SOUTH 
WINDS ALOFT...BLOWING OVER THE LOW LEVEL EASTERLY FLOW COMING FROM 
GORGE.ROCKEY/WOLFE
&&

.MARINE...NOT MUCH CHANGE. CONDITIONS WILL DETERIORATE LATER TODAY 
AS WARM FRONT LIFTS ACROSS THE REGION. THIS WILL BRING GALE FORCE 
SOUTH WINDS. HOWEVER...STRONG WINDS ARRIVE TONIGHT AS RATHER STRONG 
LOW PRES PASSES ACROSS THE N OREGON COASTAL WATERS. STORM WARNING 
FOR THE COASTAL WATERS FOR TONIGHT. WINDS TURN MORE W TO NW ON 
SUNDAY AND BEGIN EASING. SEAS TONIGHT LIKELY TO PEAK IN THE 20 TO 25 
FT RANGE...BUT WILL DROP QUICKLY ON SUN. 
&&

.PQR WATCHES/WARNINGS/ADVISORIES...
WA/OR...GALE WARNING FOR COASTAL WATERS FROM CAPE SHOALWATER TO 
     FLORENCE FOR THIS AFTERNOON.
STORM WARNING FOR COASTAL WATERS FROM CAPE SHOALWATER TO 
     FLORENCE FOR TONIGHT. 
SMALL CRAFT ADVISORY FOR ROUGH COLUMBIA RIVER BAR CONDITIONS 
     THROUGH SUN.
SNOW ADVISORY FOR THE SOUTH WASHINGTON AND NORTH OREGON
     CASCADES THROUGH 4 PM.
WINTER STORM WARNING FOR THE S WA AND N AND CENTRAL OREGON
     CASCADES TONIGHT AND SUNDAY.
HIGH WIND WATCH FOR THE SOUTHERN WASHINGTON/NORTHERN AND     
    CENTRAL OREGON COAST TONIGHT.
&&

$$

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.