FXUS66 KPQR 291653
AFDPQR

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE PORTLAND OR
852 AM PST SUN NOV 29 2009

.SYNOPSIS...QUIET TODAY THROUGH MONDAY AS AN UPPER LEVEL RIDGE
STRENGTHENS OVER THE AREA. THIS WILL RESULT IN VALLEY INVERSIONS WITH
AREAS OF FOG. ANOTHER WEAK SYSTEM WILL RIDE OVER THE RIDGE LATE
MONDAY AND MONDAY NIGHT...BUT AT MOST BRUSH THE FAR NORTH PART OF OUR
FORECAST AREA. OTHERWISE...THE UPPER RIDGE IS EXPECTED TO CONTINUE
THROUGH MOST OF THE WEEK AS PACIFIC SYSTEMS DISSIPATE OFFSHORE. 

&&

.SHORT TERM...INITIAL VISIBLE SATELLITE IMAGERY SHOWING CONSIDERABLE
CLEARING OVER THE COAST...COAST RANGE AND CASCADES...EXCEPT IN THE N
WHERE RESIDUAL MOISTURE CONTINUES BELOW 850MB. FOG AND LOW CLOUDS
COVER THE CENTRAL AND S WILLAMETTE VALLEY. EXPECT THE NORTHERN CLOUDS
WILL CONTINUE TO DECREASE TODAY WHILE THE SOUTHERN VALLEY FOG
DISSIPATES. 

THE UPPER RIDGE WILL STRENGTHEN TODAY INTO TONIGHT. VERY LIGHT
OFFSHORE SURFACE GRADIENTS WILL SET UP LATE THIS AFTERNOON WITH
SURFACE HIGH PRES CENTERED NEAR THE OREGON AND IDAHO BORDER...AND
INVERTED SURFACE TROUGH ALONG THE S OREGON COAST. THE OFFSHORE
GRADIENTS PICK UP A BIT TONIGHT INTO MON MORNING AND MIGHT SEE 3-4 MB
OFFSHORE FROM KDLS-KTTD BY 12Z MON FOR SOME GUSTS TO 30 MPH OR SO IN
THE W GORGE. EXPECT MORE VALLEY FOG TONIGHT AS INVERSIONS SET UP
UNDER THE RIDGE. MOST FOG PRONE PLACES WILL BE S PARTS OF THE
WILLAMETTE VALLEY. 

THE NEXT SYSTEM IS LIKELY TO FALL APART AS A PORTION OF IT PUSHES
ACROSS WA MON AFTERNOON. MAIN AFFECT WILL BE A SWITCH TO LOW-LEVEL
ONSHORE FLOW MON AFTERNOON. MINIMAL...IF ANY...POPS WITH THIS
SYSTEM...WITH GFS ABOUT THE ONLY MODEL SHOWING ANY QPF AND THIS
CONFINED TO THE FAR NORTHERN ZONES MON AFTERNOON AND EVENING. 
SURFACE HIGH BUILDS OVER EASTERN BC MON NIGHT...WHICH WILL START TO
TURN THE LOW-LEVEL FLOW BACK TO OFFSHORE ON TUE. RW

.LONG TERM...NO CHANGES. PREVIOUS DISCUSSION FOLLOWS...THE UPPER
RIDGE IS LIKELY TO HOLD THROUGH MIDWEEK...ALTHOUGH THE ECMWF HAS A
WEAK UPPER LOW CUTTING UNDERNEATH THE RIDGE ON WED. THAT SOLUTION IS
NOT SUPPORTED BY GFS ENSEMBLES OR THE CANADIAN MODEL. BEGINNING ABOUT
THU THE VARIOUS MODEL ARE SHOWING LARGE VARIATIONS IN POSSIBLE
SOLUTIONS AS THE UPPER RIDGE POTENTIALLY RETROGRADES INTO THE PAC.
GFS ENSEMBLES HINT AT HIGHER POPS CENTERED AROUND FRI. WE HAVE ADDED
POPS IN THE THU THROUGH SAT PERIOD BUT KEPT THEM WELL BELOW CLIMO
UNTIL THERE IS BETTER CONSISTENCY IN MODEL SOLUTIONS. RW

&&

.AVIATION...VFR ACROSS THE REGION...EXCEPT ALONG THE I5 CORRIDOR 
WHERE IFR FOG AND STRATUS PERSIST IN THE CENTRAL AND S WILLAMETTE 
VALLEY. STILL EXPECTING THAT FOG TO LIFT BETWEEN 19Z AND 
21Z...GIVING WAY TO VFR CONDITIONS. IN THE N WILLAMETTE...MOSTLY VFR 
BUT WILL SEE AREAS OF MVFR CIGS THROUGH 19Z. SHOULD SEE REPEAT OF 
CONDITIONS AGAIN TONIGHT...WITH MORE EXTENSIVE FOG LIKELY. 

KPDX AND APPROACHES...WILL CONTINUE TO SEE MIX OF MVFR AND LOW VFR 
THROUGH 19Z...THEN JUST VFR EXPECTED. LIKELY TO SEE FOG AND/OR LOW 
STRATUS FORM AFTER 09Z TONIGHT.     4CSTR...ROCKEY

&&

.MARINE...WINDS REMAIN UNDER 15 KT FOR THE NEXT SEVERAL DAYS.  SEAS 
REMAIN HIGH...GENERALLY REMAINING IN THE 12 TO 15 FT RANGE THRU MON 
NIGHT. APPEARS THAT SWELL WILL SUBSIDE BELOW 10 FT EARLY TUE. 

&&

.PQR WATCHES/WARNINGS/ADVISORIES...
WA/OR...SMALL CRAFT ADVISORY FOR HAZARDOUS SEAS FOR COASTAL WATERS   
  FROM CAPE SHOALWATER TO FLORENCE THROUGH MON. 
SMALL CRAFT ADVISORY FOR ROUGH COLUMBIA RIVER BAR     
  CONDITIONS THROUGH 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.