FXUS66 KPQR 280423
AFDPQR

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE PORTLAND OR
820 PM PST FRI NOV 27 2009

.SYNOPSIS...AN UPPER LEVEL RIDGE WILL SPREAD OVER THE FORECAST AREA
TONIGHT AND SATURDAY. HOWEVER...THE TAIL END OF A WARM FRONT WILL
DRIFT ACROSS THE NORTH ZONES SATURDAY AND SATURDAY EVENING...AND THEN
LIFT TO THE NORTH BY SUNDAY  HIGH PRESSURE STRENGTHENS SUNDAY AND
SHOULD PERSIST THROUGH MONDAY...WHICH WILL RESULT IN VALLEY
INVERSIONS. ANOTHER SYSTEM WILL RIDE OVER THE RIDGE 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 AN INVERSION AND VALLEY FOG PERSISTING.
&&

.SHORT TERM...HIGH PRESSURE ALOFT BUILDING OVER THE FORECAST AREA
TONIGHT. INFRA-RED SATELLITE IMAGERY THIS EVENING SHOWS PLENTY OF
STRATOCUMULUS CLOUDS OVER MUCH OF THE REGION. BREAKS IN THE CLOUDS
MORE PREVALENT ON THE LEE SIDE OF THE COAST RANGE AND PORTIONS OF THE
WILLAMETTE VALLEY. CLOUD TOPS APPEAR TO BE AROUND 040 NORTH TO 050
SOUTH. CLOUDS WILL MAKE MIN TEMPS TRICKY. THE EXTENSIVE STRATOCUMULUS
CLOUDS COULD ALSO LIMIT FOG FORMATION. 

LATEST NAM AND 18Z GFS CONTINUE TO INDICATE VERY WEAK SURFACE
GRADIENTS SAT MORNING. THUS...ANY FOG OR LOW CLOUDS THAT FORM MAY
TAKE AWHILE TO DISSIPATE. 00Z NAM SHOWS THE WARM-FRONTAL FEATURE
SLIDING ACROSS WRN WA AND EXTREME NW OREGON SAT. TRIMMED BACK POPS
JUST A BIT SAT MORNING...AND MADE SOME MINOR TWEAKS TO SAT AFTERNOON.
BASICALLY KEPT CHANCE POPS IN THE NORTH BUT SCALED BACK IN THE SOUTH.

HIGH PRESSURE ALOFT STRENGTHENS SUN. LIGHT OFFSHORE SURFACE GRADIENTS
SET UP SUN AFTERNOON WITH SURFACE HIGH PRES CENTERED NEAR THE OREGON
AND IDAHO BORDER. THE OFFSHORE GRADIENTS PICK UP A BIT MORE SUN
NIGHT. THE MODELS STILL LOOK RATHER DRY ON MONDAY...WITH THE
PREVIOUSLY ADVERTISED SYSTEM SPLITTING. WEISHAAR

.LONG TERM...NO CHANGES. PREVIOUS DISCUSSION FOLLOWS...A BRIEF
SHORTWAVE PASSES TO THE NORTH OF THE PAC NW MON AFTERNOON. NEWEST
MODEL RUNS HAVE AMPLIFIED A RIDGE OVER THE REGION...LOWERING THE
IMPACT THIS DISTURBANCE HAS FOR THE FORECAST AREA. THIS DISTURBANCE
DOES LEVEL THE UPPER RIDGE AT THIS TIME...BUT ANTICIPATE DRY AND
MOSTLY CLEAR CONDITIONS. A SYSTEM APPROACHES AND CAUSES DISAGREEMENT
AMONG THE MODELS AROUND WED. PREVIOUS RUNS OF ECMWF/CANADIAN WERE
MORE CONSERVATIVE...KEEPING THE SYSTEM STALLED OFFSHORE UNTIL THE
WEEKEND. HOWEVER...THE 12Z ECMWF RUN SHOWS A DISTURBANCE BRINGING
PRECIP OVER THE REGION BY EARLY THU. GFS BRINGS PLENTY OF PRECIP IN
BY THU NIGHT...WHILE THE ECMWF HAS WEAK HIGH PRES HOLD BACK THE BULK
OF THE SYSTEM. STILL AGREED MORE WITH THE 00Z ECMWF/CANADIAN RUNS AND
KEPT THE AREA DRY AFTER TUE AFTERNOON. WILL HAVE TO WATCH THE MODELS
CONSISTENCY FOR THE TIMING AND STRENGTH OF THIS NEXT SYSTEM. LRAMIREZ
&&

.AVIATION...SCATTERED VFR CLOUDS IN THE WILLAMETTE VALLEY THIS 
EVENING WITH A BROKEN DECK OVER THE CASCADES AND COAST RANGE. THE 
VFR CLOUDS SHOULD DECREASE OVERNIGHT AS HIGH PRESSURE MOVES IN. 
HOWEVER...LOW LEVEL ONSHORE FLOW WILL BRING SOME CHALLENGE TO 
THE TAFS TONIGHT. NOT IDEAL FLOW FOR WIDESPREAD FOG...BUT WITH
CLEARING SKIES AND LIGHT WINDS AREAS OF FOG SHOULD FORM AFTER 08Z
WITH THE BEST THREAT OVER THE INTERIOR...ESPECIALLY S OF A KHIO TO
KUAO LINE. FOG MAY BE LIMITED ALONG THE COAST AND INTO THE KKLS TO
KPDX CORRIDOR WITH AREAS OF IFR STRATUS. ANY FOG THAT DOES FORM WILL 
PERSIST WELL INTO SAT AM...POSSIBLY LATER.

KPDX AND APPROACHES...VFR CONDITIONS THIS EVENING WITH LIGHT 
NORTHWESTERLY ONSHORE FLOW. EXPECT AREAS OF FOG TO FORM AROUND KPDX 
NEAR 09Z. LOOKS AS THOUGH WE MAY WIND UP WITH MORE IFR STATUS AFTER 
11Z RATHER THAN IFR FOG...BUT THESE LOW CIGS WILL BE PERSISTENT 
THROUGH 18Z.

&&

.MARINE...GRADIENTS WILL CONTINUE TO RELAX THIS EVENING AS NORTHWEST 
WINDS EASE. SEAS A BIT SLOWER TO SUBSIDE. SEAS WILL BRIEFLY DROP 
BELOW 10 FT LATE TONIGHT...BUT WILL RISE ABOVE 10 FT AGAIN LATER 
SAT. EVEN THOUGH NO SIGNIFICANT WINDS ARE EXPECTED THIS WEEKEND AND 
EARLY NEXT WEEK...SEAS WILL REMAIN IN THE 12 TO 15 FT RANGE FOR SUN 
THROUGH TUE. 
&&

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