FXUS66 KPQR 251700
AFDPQR

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE PORTLAND OR
900 AM PST WED NOV 25 2009

.SYNOPSIS...AN UPPER LEVEL RIDGE OF HIGH PRESSURE WILL REMAIN OVER 
THE REGION THROUGH MOST OF TODAY. A SLOW MOVING FRONT OFFSHORE WILL 
EASE INTO THE FAR NORTHWEST PART OF THE REGION LATER TODAY AND BEGIN 
MOVING INLAND ON THANKSGIVING DAY. AN UPPER LEVEL TROUGH WILL DIG 
INTO THE BACK SIDE OF THE FRONT THURSDAY AND SLOW THE EASTWARD 
PROGRESSION OF THE FRONT.  THE UPPER LEVEL TROUGH WILL MOVE ACROSS 
THE REGION ON FRIDAY WITH A RIDGE OF HIGH PRESSURE BUILDING INTO THE 
REGION LATE IN THE WEEKEND. 

&&

.SHORT TERM...SURFACE OBSERVATIONS SHOW QUITE A FEW AREAS OF FOG IN 
THE INTERIOR VALLEYS THIS MORNING. A FEW OCCASIONAL AIRPORT
OBSERVATIONS AND SPOTTER REPORTS FROM THIS AREA INDICATE THE FOG IS
LOCALLY DENSE...LOCALLY REDUCING VISIBILITY TO ONE QUARTER MILE OR 
LESS.  THE FOG MAY TAKE A WHILE TO DISSIPATE TODAY AS IT BECOMES 
MORE DIFFICULT FOR THE SOLAR HEATING FROM THE LOW SUN ANGLE THIS 
TIME OF YEAR TO OVERCOME VALLEY INVERSIONS. AS A RESULT OF 
THIS...SOME OF THE INTERIOR VALLEYS MAY REMAIN TRAPPED IN COOL 
INVERSIONS MUCH OF THE DAY...AND STRUGGLE TO REACH 50 DEGREES THIS 
AFTERNOON. ON THE OTHER HAND...INCREASED TODAYS HIGH TEMPERATURE 
FORECAST A BIT IN THE HIGHER ELEVATIONS...AS THE WARM AIR MASS ALOFT 
(+8 TO +10 DEG C AT 850 MB) SHOULD ALLOW MOST OF THE FOOTHILLS... 
ABOVE THE VALLEY INVERSIONS...TO REACH THE 50S OR EVEN LOWER 
60S...MUCH LIKE YESTERDAY.

TO OUR WEST...A SLOW MOVING COLD FRONT REMAINS POISED TO MOVE ONSHORE
FOR THE UPCOMING HOLIDAY. MODELS REMAIN IN GOOD AGREEMENT SHOWING 
THE OFFSHORE COLD FRONT SAGGING TO NEAR THE S WA/N OREGON COAST LATE 
TODAY...THEN PUSHING A LITTLE FURTHER INTO SW WA TONIGHT. ELSEWHERE 
MOISTURE AND POPS WILL REMAIN RATHER LOW THROUGH TONIGHT.  

INCREASED THE QPF ASSOCIATED WITH THE FRONTAL SYSTEM AS IT MOVES 
ONSHORE...TO BRING IT MORE IN LINE WITH RFC GUIDANCE. IT APPEARS 
SOME AREAS IN THE COAST RANGE COULD RECEIVE AS MUCH AS 2-4 INCHES OF 
RAIN LOCALLY...WITH INLAND LOCATIONS RECEIVING A BIT LESS...CLOSER 
TO ONE HALF TO ONE INCH. FOR NOW...IT APPEARS THIS WILL NOT BE 
ENOUGH TO CREATE ANY MAJOR HYDROLOGIC PROBLEMS IN OUR AREA...BUT 
WILL CONTINUE TO MONITOR AS IT APPEARS THIS FRONTAL SYSTEM DOES HAVE 
ACCESS TO SOME SUBTROPICAL MOISTURE.  

MODELS SHOW THE THE UPPER TROUGH DIGGING INTO THE BACK SIDE OF THE
OFFSHORE FRONT ON THURSDAY CAUSING SOME BACKING OF THE STEERING FLOW
AS THE SYSTEM INTENSIFIES. THIS SLOWS THE INLAND PROGRESSION OF THE
FRONT UNTIL LATE THURSDAY AFTERNOON OR THURSDAY NIGHT. MODELS
CONTINUE TO HAVE SOME DIFFERING SOLUTIONS REGARDING THE TRACK AND
INTENSITY OF THE ASSOCIATED SURFACE LOW THAT LIFTS NNE BEHIND THE 
FRONT.CURRENT MODELS SUGGEST BREEZY/WINDY CONDITIONS BUT PROBABLY 
NO HIGH WINDS. INCREASING OROGRAPHICS AND LOWERING SNOW LEVELS 
SHOULD CAUSE SOME DECENT SNOW ACCUMULATIONS IN THE CASCADES LATER 
THU NIGHT INTO FRI...POSSIBLY ENOUGH TO CONSIDER WINTER WEATHER 
ADVISORY FOR SEVERAL INCHES OF SNOW.  WEAGLE/TW

.LONG TERM...NO CHANGES. PREVIOUS DISCUSSION FOLLOWS...ALL THE MODELS
SHOW A SHORT WAVE MOVING THROUGH FRIDAY NIGHT FOR SOME PRECIPITATION 
WITH SNOW LEVEL NEAR OR BELOW THE CASCADE PASSES. AFTER THAT...THE 
MODELS SHOW RIDGING OVER THE PACIFIC NORTHWEST THE RESULT OF ENERGY 
OUT AROUND 140W OR 150W. THIS CAUSES THE MAIN JET TO LIFT NORTH OF 
OUR AREA EARLY NEXT WEEK...WITH PERHAPS SOME PRECIPITATION BRUSHING 
THE NORTH COAST AT TIMES. ANOTHER SYSTEM BRUSHES THE AREA MONDAY AND 
MONDAY NIGHT WITH THE BEST CHANCES OF ANY PRECIPITATION IN THE NORTH 
PART OF OUR FORECAST AREA. THE RIDGE APPEARS TO REBOUND AGAIN FOR 
THE MIDDLE OF NEXT WEEK. ENSEMBLE SPREADS STARTING TO INCREASE EARLY 
NEXT WEEK BUT NOT AS MUCH AS SEEN YESTERDAY. EXPECT TO SEE SOME 
PERIODS OF VALLEY FOG DURING THE DRIER PERIODS. TOLLESON

&&

.AVIATION...NORTH COAST WILL HAVE PRECIPITATION AND A DEFINITE 
RETURN TO LOW MVFR OR IFR CLOUDS THIS AFTERNOON AS NEXT FRONT 
ARRIVES  AND REMAINS THROUGH THU. CENTRAL COAST NOT AFFECTED MUCH BY 
CLOUDS UNTIL THU MORNING...PERHAPS A BRIEF PERIOD OF MVFR THIS 
AFTERNOON. INLAND SITES UNHINDERED BY FRONTAL SYSTEM TODAY...VFR 
THROUGH THE AFTERNOON AND TONIGHT.

KPDX AND APPROACHES...EXPECT VFR CONDITIONS AFTER 18Z. MID AND HIGH 
LEVEL CLOUDS WILL INCREASE IN THE AFTERNOON. VFR CONDITIONS THROUGH 
THU AM. 

&&

.MARINE... LATEST MODEL GUIDANCE CONTINUES TO SHOW SMALL CRAFT WIND 
OVER THE OUTER WATERS OF ZONE 270...BUT PRIMARILY THE NORTHWEST 
THIRD. SEAS RISE ABOVE 11 FT THIS AFTERNOON AS THE NEXT FRONTAL 
SYSTEM ARRIVES. WINDS EXPECTED TO EASE A BIT THIS AFTERNOON AS THE 
FRONTAL BOUNDARY STALLS OFFSHORE. A SECONDARY LOW PRES CENTER FORMS 
ON THE FRONT OFF THE COAST BRINGING IN NEXT ROUND OF SMALL CRAFT 
WINDS  BY 18Z THU...THEN SPREADING NORTH THANKSGIVING DAY. GALES 
POSSIBLE AS LOW PRES MOVES INLAND BUT TIMING STILL SOMEWHAT 
UNCERTAIN. SEAS BUILD TO MID AND UPPER TEENS THU AND FRI. SEAS NOT 
LIKELY TO DROP BELOW 10 FT UNTIL LATE WEEKEND OR EARLY NEXT WEEK.

&&

.PQR WATCHES/WARNINGS/ADVISORIES...
WA/OR...SMALL CRAFT ADVISORY FOR WIND CAPE SHOALWATER TO 
  CASCADE HEAD THROUGH 7 PM THIS EVENING.  
SMALL CRAFT ADVISORY FOR HAZARDOUS SEAS CAPE 
  SHOALWATER TO FLORENCE LATE THIS MORNING THROUGH 
  THU NIGHT.   
SMALL CRAFT ADVISORY FOR ROUGH COLUMBIA RIVER BAR 
  CONDITIONS THIS MORNING THROUGH LATE THU NIGHT. 



&&

$$

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.