FXUS66 KPQR 262253
AFDPQR

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE PORTLAND OR
253 PM PST THU NOV 26 2009

.SYNOPSIS...A MOIST FRONTAL SYSTEM IS SLOWLY MOVING ACROSS THE
DISTRICT THIS AFTERNOON...BRINGING WIDESPREAD AND PERSISTENT MODERATE
RAINFALL. LOW PRESSURE HAS DEVELOPED ALONG THE FRONT OFFSHORE FROM
FLORENCE...AND HAS SLOWED DOWN THE FRONT EVEN FURTHER THIS AFTERNOON.
THIS LOW WILL TRAVEL NORTHEAST ACROSS THE FORECAST AREA LATER THIS
AFTERNOON AND EVENING...WITH RAIN GRADUALLY TAPERING TO SHOWERS LATER
TONIGHT AND FRIDAY AS THE FRONT FINALLY MOVES EAST OF THE CASCADES.
COOLER AIR WILL CAUSE SNOW LEVELS TO FALL ONCE AGAIN DOWN TO THE
CASCADE PASSES...WITH MINOR ACCUMULATIONS EXPECTED BEFORE SNOW TAPERS
OFF FRIDAY. A STALLED FRONT MAY BRING MORE PRECIPITATION MAINLY TO
NORTHERN AREAS FOR THE WEEKEND...THEN A DRIER WEATHER PATTERN LOOKS
POSSIBLE FOR MUCH OF NEXT WEEK. 

&&

.SHORT TERM...THE RAIN HAS BEEN STEADY FOR MUCH OF THIS THANKSGIVING
DAY ACROSS THE MAJORITY OF THE FORECAST AREA. OUR SOUTHERN INTERIOR
SECTIONS WERE THE LAST TO GET IN ON THE RAINFALL...BUT RAIN FINALLY
APPEARS TO BE MOVING SOUTHEAST INTO THE OAKRIDGE AND WILLAMETTE
NATIONAL FOREST AREA THIS AFTERNOON. THE RAIN HAS HELD TEMPERATURES
DOWN IN THE 40S FOR MOST OF THE INTERIOR VALLEYS...WITH LOW CEILINGS
AND REDUCED VISIBILITY PROVIDING QUITE A DREARY LATE NOVEMBER DAY.

THIS RAIN IS IN ASSOCIATION WITH A VERY SLOW MOVING AND MOIST FRONTAL
BOUNDARY WHICH EXTENDS FROM AROUND KELSO SOUTHWESTWARD INTO THE
SUBTROPICAL PACIFIC. THE FRONT IS STILL GRABBING A HOLD OF A DECENT
MOISTURE PLUME FROM THE SUBTROPICS...WITH AMSU PRECIPITABLE WATER
VALUES GENERALLY AROUND 1.25 INCHES WITHIN THE PLUME. NOT
EXCESSIVE...BUT STILL ENOUGH TO GENERATE SOME PRETTY DECENT RAIN
RATES THROUGHOUT MUCH OF THE DISTRICT TODAY. A WEAK SFC LOW
DEVELOPING ALONG THE FRONT JUST OFFSHORE OF FLORENCE IS PROVIDING A
FOCUSING MECHANISM FOR PRECIPITATION THIS AFTERNOON...WITH RAIN RATES
UPWARDS OF A QUARTER INCH PER HOUR IN THE OREGON COAST RANGE.
RAINFALL RATES IN THE INTERIOR VALLEYS HAVE GENERALLY BEEN 0.1-0.2
INCH PER HOUR...BUT SOME HEAVIER RATES HAVE BEEN NOTED NEAR EUGENE IN
THE PAST COUPLE HOURS. OVERALL...EXPECT THE COAST RANGE TO RECEIVE
ABOUT 2 INCHES OF RAIN FROM THIS EVENT...NOT QUITE ENOUGH TO CAUSE
ANY MAJOR HYDROLOGIC ISSUES. ACROSS THE INLAND VALLEYS... RAINFALL
TOTALS WILL PROBABLY REACH 0.50-1.00 INCH BY LATER TONIGHT IN MOST
AREAS.

SNOW LEVELS WILL BE FALLING AS THE FRONT MOVES ONSHORE. THIS MORNINGS
KSLE SOUNDING SHOWS FREEZING LEVELS AROUND 10000 FT...BUT THIS WILL
DROP QUICKLY THROUGH TONIGHT...WITH SNOW LEVELS DOWN BELOW THE
CASCADE PASSES BY FRI MORNING. A COUPLE INCHES OF ACCUMULATION ARE
POSSIBLE IN LINGERING SHOWERS BEHIND THE FRONT...BUT MODELS HAVE
CONTINUED THEIR TREND TOWARD LESS IMPRESSIVE OROGRAPHIC FLOW BEHIND
THE FRONT FRIDAY. ACCUMULATIONS AT THIS POINT APPEAR WILL BE WELL
BELOW ANY ADVISORY THRESHOLDS.

FRIDAY NIGHT THROUGH THE WEEKEND LOOK 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. GFS/ECMWF ALSO ARE HANGING ONTO
THE IDEA OF LINGERING WARM FRONTAL PRECIPITATION PORTLAND METRO AREA
NORTHWARD FOR THE WEEKEND...WILL HAVE TO SEE ABOUT THIS AS BOTH
MODELS BUILD THE UPPER RIDGE STRONG AND FAST ACROSS THE PACIFIC
NORTHWEST.  WEAGLE  

.LONG TERM...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...THE RAIN BAND CONTINUES TO PUSH INLAND THIS AFTERNOON 
WITH A MIX OF MVFR AND IFR CONDITIONS. CONDITIONS ARE BEGINNING TO 
IMPROVE BEHIND THE RAIN BAND ALONG THE COAST. HOWEVER...VFR 
CONDITIONS ARE NOT EXPECTED THERE AS WRAP-AROUND RAIN KEEPS THINGS 
MURKY. THE SURFACE FRONT WILL LIKELY NOT MOVE ONSHORE UNTIL 02Z FOR 
THE NORTH COAST AND 05Z FOR THE CENTRAL COAST. IT MAY TAKE UNTIL 
06Z-08Z BEFORE THE FRONT CLEARS THE INTERIOR WITH MARKED CEILING AND 
VISIBILITY IMPROVEMENT

KPDX AND APPROACHES...RAIN WILL CONTINUE THROUGH THE EVENING WITH A 
MIX OF IFR AND MVFR CONDITIONS. THE SURFACE FRONT WILL MOVE ACROSS 
THE TERMINAL BETWEEN 07Z AND 09Z USHERING IN SHOWERS AND A MIX OF 
VFR AND MVFR CONDITIONS. 

&&

.MARINE...A LOW END SMALL CRAFT ADVISORY FOR WINDS LOOKS REASONABLE 
THROUGH MIDDAY FRIDAY AS A FRONT SLOWLY MOVES ACROSS THE WATERS AND 
HIGH PRESSURE BUILDS IN ACROSS THE EASTERN PACIFIC. THE FRONT WILL 
MOVE INLAND EARLY THIS EVENING UP NORTH AND LATER IN THE EVENING 
DOWN SOUTH. SEAS WILL CONTINUE TO SLOWLY SUBSIDE FOR THE NEXT FEW 
DAYS. HOWEVER...SEAS ARE NOT LIKELY TO DROP BELOW 10 FT UNTIL LATE 
FRIDAY EVENING.

&&

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

$$

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.