FXUS66 KPQR 281017
AFDPQR

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE PORTLAND OR
216 AM PST SAT NOV 28 2009

.SYNOPSIS...AN UPPER LEVEL RIDGE WILL BUILD OVER THE FORECAST AREA
TODAY. HOWEVER...THE TAIL END OF A WARM FRONT WILL DRIFT ACROSS THE
NORTH ZONES TODAY AND THIS EVENING...AND THEN LIFT TO THE NORTH BY
SUNDAYHIGH 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 CONTINUES TO BUILD OVER THE
FORECAST AREA THIS MORNING. SATELLITE IMAGERY AND SURFACE
OBSERVATIONS SHOW WIDESPREAD STRATOCUMULUS CLOUDS OVER THE REGION
WITH BASES BETWEEN 3500 AND 4500 FEET. THE EXTENSIVE STRATOCUMULUS
CLOUDS WILL LIMIT FOG FORMATION THIS MORNING...HOWEVER HAVE ALREADY
SEEN FOG DEVELOPING IN THE KEUG AREA. CURRENT MODEL RUNS INDICATE
VERY WEAK SURFACE GRADIENTS THIS MORNING...MAKING ANY FOG OR LOW
CLOUDS SLOW TO DISSIPATE. 

MODELS STILL SHOW A WARM-FRONTAL FEATURE SLIDING ACROSS WRN WA AND
EXTREME NW OREGON TODAY. SATELLITE IMAGERY SHOWS SOME OVERRUNNING
WARM FRONTAL CLOUDS CURRENTLY BRUSHING THE EXTREME NORTHERN ZONES. 
WILL KEEP CHANCE TO SLIGHT CHANCE POPS ONLY IN THE VERY NORTHERN
ZONES TODAY AND THIS EVENING.

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. LIKENS

.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...BKN TO OVC VFR CLOUDS IN THE WILLAMETTE VALLEY WITH LOW 
LEVEL ONSHORE FLOW THIS MORNING. VFR DECK IS SUPPRESSING THE 
POTENTIAL FOR FOG. IF SKIES CLEAR A BIT COULD SEE AREAS OF FOG 
DEVELOP THIS MORNING THOUGH THIS IS APPEARING LESS LIKELY AS A WEAK 
FRONT SAGS TOWARDS THE AREA INCREASING CLOUDS. 

KPDX AND APPROACHES...VFR CONDITIONS THIS EVENING WITH LIGHT 
NORTHWESTERLY ONSHORE FLOW. EXPECT AREAS OF FOG/IFR STRATUS TO FORM 
AROUND KPDX IF OVC VFR CIGS BREAK...OTHERWISE VFR. WOLFE

&&

.MARINE...FAIRLY RELAXED GRADIENT OVER WATERS. SEAS BRIEFLY BELOW 10 
FT THIS MORNING...BUT WILL RISE ABOVE 10 FT AGAIN LATER TODAY. 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 THIS MORNING. 
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.