FXUS66 KPQR 291029
AFDPQR

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

.SYNOPSIS...AN UPPER LEVEL RIDGE OF HIGH PRESSURE WILL STRENGTHEN
OVER THE AREA TODAY AND SHOULD PERSIST THROUGH MONDAY...WHICH WILL
RESULT IN VALLEY INVERSIONS AND AREAS OF FOG. ANOTHER 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
WILL CONTINUE THROUGH MOST OF NEXT WEEK WITH INVERSIONS AND VALLEY
FOG PERSISTING.

&&

.SHORT TERM...SATELLITE IMAGERY AND SURFACE OBSERVATIONS SHOW MOSTLY
CLEAR SKIES OVER THE SOUTHERN HALF OF THE AREA WITH SOME PATCHY FOG
DEVELOPING. SOME LIGHT OFFSHORE FLOW ALONG THE COAST SOUTH OF NEWPORT
HELPING TO MAINTAIN GENERALLY CLEAR SKIES THERE.   STILL SEEING A LOW
LEVEL DECK IN THE NORTHERN ZONES WITH BASES 2500 - 3500 FT. THIS
SEEMS TO BE INHIBITING FOG DEVELOPMENT.

THE UPPER RIDGE WILL STRENGTHEN TODAY. 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 SOUTH OREGON COAST. THE OFFSHORE GRADIENTS PICK UP A
BIT TONIGHT INTO MON. MIGHT SEE 3-4 MB OFFSHORE FROM KDLS-KTTD BY 12Z
MON...SHOULD GIVE GUSTS TO 30 MPH OR SO IN THE WINDIEST SPOTS. EXPECT
MORE VALLEY FOG TONIGHT AS INVERSIONS SET UP UNDER THE RIDGE. MOST
PRONE PLACES WILL BE WEST AND SOUTH PARTS OF THE WILLAMETTE VALLEY. 

NEXT SYSTEM SCHEDULED TO FALL APART AS IT REACHES THE AREA LATE MON.
MAIN AFFECT WILL BE A SWITCH TO LOW-LEVEL ONSHORE FLOW MON AFTERNOON.
MINIMAL...IF ANY...POPS WITH THIS SYSTEM. SURFACE HIGH BUILDS OVER
ERN BC MON NIGHT...WHICH WILL START TO TURN THE LOW-LEVEL FLOW BACK
TO OFFSHORE. LIKENS

.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...ALL INGREDIENTS ARE PRESENT FOR FOG THOUGH AREAS OF MID 
LEVEL DECK ARE MITIGATING DEVELOPMENT. VERY DIFFICULT TO SPECIFY 
WHERE IT WILL FORM...SO WILL KEEP IT IN TAFS AT FOG PRONE SITES AND 
OMIT IT FROM OTHER SITES. 

KPDX AND APPROACHES...NEAR VFR CIGS. POSSIBLE 1-3 SM FOG FORMATION. 
IF IT DEVELOPS PROBABLY BETWEEN 14-17Z.
&&

.MARINE...WINDS REMAIN UNDER 20 KT FOR THE NEXT SEVERAL DAYS. SWELL 
GENERATED FROM AFAR HAS ARRIVED. THIS SWELL WILL VARY IN HEIGHT FROM 
TIME TO TIME...BUT GENERALLY REMAIN IN THE 13 TO 16 FT RANGE THRU 
TUE. LARGEST WAVES WILL BE ACROSS THE NORTHERN AND OUTER COASTAL 
WATERS. 

&&

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

&&

$$

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.