FXUS66 KPQR 271017 CCA
AFDPQR

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE PORTLAND OR
217 AM PST FRI NOV 27 2009

.SYNOPSIS...A MOIST FRONTAL SYSTEM NEAR THE SOUTH WASHINGTON/NORTH
OREGON CASCADES THIS MORNING WILL CONTINUE TO SLOWLY MOVE EAST. A
SPLITTING UPPER LEVEL TROUGH MOVES ACROSS THE FORECAST AREA FRIDAY
WITH SNOW LEVELS DROPPING TO WELL BELOW PASS LEVELS...BUT ONLY MINOR
SNOWFALL ACCUMULATIONS WILL OCCUR. WEAK HIGH PRESSURE ALOFT DEVELOPS
SATURDAY...BUT THE TAIL END OF A WARM FRONT IS EXPECTED TO CLIP THE
NORTH ZONES. HIGH PRESSURE STRENGTHENS SUNDAY. THE DRY REGIME COULD
LAST MUCH OF NEXT WEEK.  

&&

.SHORT TERM...SATELLITE IMAGERY SHOWS THE BACK EDGE OF THE BAROCLINIC
BAND STRETCHED FROM NORTH-CENTRAL WASHINGTON TO THE SOUTHWEST CORNER
OF OREGON AND SOUTHWEST OFFSHORE. SURFACE OBSERVATIONS INDICATE THE
SURFACE LOW MOVED ONSHORE NEAR KTMK AND HAS NOW MOVED JUST EAST OF
KTMK. NATIONAL WEATHER SERVICE DOPPLER RADAR SHOWED SHOWERS
CONTINUING OVER THE SOUTH WASHINGTON CASCADES AND FOOTHILLS TO THE
LANE COUNTY CASCADES. SNOW LEVELS THIS MORNING ARE ABOVE 5250-FOOT
SENSOR...BUT HAVE FALLEN BELOW THE 6000-FOOT SENSOR AT TIMBERLINE.
THE COLDER AIR WILL FILTER INTO THE REGION THIS MORNING...BUT WELL
AFTER THE MAIN PRECIPITATION BAND HAS EXITED THE AREA. 

THE UPPER TROUGH WILL MOVE ACROSS THE DISTRICT FRIDAY. THE 00Z NAM IS
SIMILAR TO THE 18Z GFS SHOWING AN UPPER LOW DEVELOPING NEAR KSFO 00Z
SAT. SHOWER ACTIVITY WILL DWINDLE FRI AFTERNOON AS HIGH PRESSURE
ALOFT STARTS TO NOSE INTO THE AREA AND THE MAIN ENERGY DIVES WELL TO
THE SOUTH. NOT EXPECTING MUCH SNOWFALL ACCUMULATION FOR THE CASCADES
FRI. 850 MB OROGRAPHIC COMPONENT NOT THAT STRONG...GENERALLY 10-15
KT...AND IT BECOMES MORE NLY IN THE AFTERNOON. 

FRIDAY NIGHT THROUGH THE WEEKEND LOOKS GENERALLY DRIER AS HIGH
PRESSURE BUILDS INTO THE PACIFIC NORTHWEST. COOL NIGHTS WILL LIKELY
LEAD TO VALLEY INVERSIONS AND AREAS OF FOG...PROBABLY AS EARLY AS
FRIDAY NIGHT DOWN IN THE EUGENE AREA. MODELS STILL HINTING AT THE
TAIL END OF A WARM-FRONTAL FEATURE DRAGGING ACROSS THE FAR NORTH LATE
FRI NIGHT AND SATURDAY. LIKENS

.LONG TERM...NO CHANGES. PREVIOUS DISCUSSION FOLLOWS...MODELS AGREE
THAT AN UPPER LEVEL RIDGE WILL AMPLIFY BEGINNING OF THE EXTENDED
PERIOD. THIS BRIEF POST FRONTAL RIDGE WILL BRING PARTLY CLOUDY
WEATHER TO THE REGION BY SUN AFTERNOON. A BRIEF SHORTWAVE PASSES TO
THE NORTH OF THE PAC NW MON AFTERNOON. THIS DISTURBANCE LEVELS THE
UPPER RIDGE AT THIS TIME...AND CAUSES DISAGREEMENT AMONG THE MODELS.
GFS AMPLIFIED THE RIDGE SO MUCH...THE SHORTWAVE IMPACTS ONLY THE FAR
NORTH BORDER OF WASHINGTON. AGREED MORE WITH THE ECMWF...WHERE THE
SHORTWAVE FLATTENS THE RIDGE ENOUGH TO BRING RAIN TO NW OREGON TUE.
BOTH GFS AND ECMWF SHOW THE RIDGE REBOUND AGAIN BY WED AND REMAINS
PERSISTENT FOR THE REMAINDER OF THE WEEK. THIS RIDGE BEGINS TO
DISSIPATE AS A SYSTEM APPROACHES THE COAST AROUND LATE FRI. LRAMIREZ

&&

.AVIATION...LOW PRES MOVING THROUGH THE VALLEY CONTINUES EAST AND 
DISSIPATES THIS MORNING. CHANGING WIND DIRECTIONS WILL BRING A 
VARIETY OF CONDITIONS TO THE TAF SITES. THE COAST MAY REMAIN VFR 
NORTH BUT THERE IS A CHANCE THAT LOW MVFR CIGS WILL SWING ONSHORE 
FOR A FEW HOURS. INLAND SLOW IMPROVEMENT WITH SOME IFR...BUT MAINLY 
MVFR CONDITIONS EARLY THIS MORNING THEN VFR DEVELOPING 18Z-20Z.  
STABLE CONDITIONS SETTING UP TONIGHT AND SAT WITH LIFR FOG 
CONDITIONS POSSIBLE.

KPDX AND APPROACHES...IFR KPDX SHOULD GIVE WAY TO MVFR BY 12Z AS 
WESTERLY WIND INCREASES WITH EASTWARD PROGRESSION LOW PRES. EXPECT 
MOSTLY MVFR THROUGH 18Z THEN TRENDING TO VFR. VFR THROUGH 03Z 
SAT...THEN LIFR DEVELOPING OVERNIGHT IN FOG.
&&

.MARINE...A SMALL CRAFT ADVISORY FOR WINDS CONTINUES THROUGH FRIDAY 
AS HIGH PRESSURE BUILDS IN ACROSS THE EASTERN PACIFIC. HAVE EXTENDED 
A FEW HOURS LONGER THAN PREVIOUS FORECAST. SEAS WILL CONTINUE TO 
SUBSIDE TODAY AND TONIGHT.  SEAS BRIEFLY DROP BELOW 10 FT FOR APPROX 
24 HOURS BEGINNING LATE THIS EVENING...BUT RISE ABOVE 10 FT AGAIN BY 
LATE SAT.

&&

.PQR WATCHES/WARNINGS/ADVISORIES...
WA/OR...SMALL CRAFT ADVISORY FOR WIND CAPE SHOALWATER TO FLORENCE 
 THROUGH FRIDAY AFTERNOON.
SMALL CRAFT ADVISORY FOR HAZARDOUS SEAS CAPE SHOALWATER TO 
 FLORENCE THROUGH FRIDAY EVENING.
SMALL CRAFT ADVISORY FOR ROUGH COLUMBIA RIVER BAR THROUGH 
 FRIDAY 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.