FXUS66 KPQR 300427
AFDPQR

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE PORTLAND OR
830 PM PST SUN NOV 29 2009

.SYNOPSIS...AN UPPER LEVEL RIDGE WILL REMAIN OVER THE AREA TONIGHT 
RESULTING IN VALLEY INVERSIONS AND AREAS OF FOG. A WEAK WEATHER 
SYSTEM WILL RIDE OVER THE RIDGE LATE MONDAY AND MONDAY NIGHT...BUT 
AT MOST WILL BRUSH THE FAR NORTH PART OF OUR FORECAST AREA. 
OTHERWISE...THE UPPER RIDGE IS EXPECTED TO CONTINUE THROUGH MOST OF 
THE WEEK AS PACIFIC SYSTEMS DISSIPATE OFFSHORE. 

&&

.SHORT TERM...SATELLITE IMAGERY AND SURFACE OBSERVATIONS SHOW FOG AND
STRATUS FORMING IN MANY VALLEY LOCATIONS THIS EVENING. ALONG WITH
VALLEY FOG...WILL ALSO SEE SOME COOL MINIMUM TEMPERATURES TONIGHT 
WITH MANY READINGS IN THE LOW 30S BY MONDAY MORNING. 

THE UPPER RIDGE WILL REMAIN OVER THE AREA TONIGHT ALLOWING VERY 
LIGHT OFFSHORE SURFACE GRADIENTS TO SET UP WITH SURFACE HIGH 
PRESSURE CENTERED OVER THE COOLER TERRAIN EAST OF THE CASCADES. THE 
OFFSHORE GRADIENTS SHOULD PEAK NEAR 3-4 MB FROM KDLS-KTTD BY 12Z MON 
FOR SOME GUSTS UP TO 30 MPH IN THE W GORGE. 

A WEAK SYSTEM WILL MOVE OVER THE TOP OF THE RIDGE AND SWEEP ACROSS 
WA MON AFTERNOON/EVE...WITH THE SOUTHERN PART OF THIS SYSTEM FALLING
APART AS IT ENCROACHES ON OUR FORECAST AREA. MAIN AFFECT WILL BE A
SWITCH TO LOW-LEVEL ONSHORE FLOW MON AFTERNOON. MINIMAL...IF ANY POPS
WITH THIS SYSTEM EXCEPT FOR SOUTH WA CASCADES WHERE NAM AND GFS
MODELS HINT AT SOME POPS MON NIGHT...POSSIBLY DROPPING INTO THE FAR
NORTH OREGON CASCADES. THE UPPER RIDGE REBOUNDS TUE AS SURFACE HIGH
PRES OVER EASTERN BC DROPS SE...WHICH WILL TURN THE LOW LEVEL FLOW
BACK TO OFFSHORE. THIS DRY PATTERN CONTINUES TUE NIGHT AND WED. TW

.LONG TERM...NO CHANGES. PREVIOUS DISCUSSION FOLLOWS...MODELS
MAINTAIN THEIR STRUGGLE FROM THU ONWARD AS THEY CONTINUE WITH
VARIATIONS IN POSSIBLE SOLUTIONS WITH THE UPPER RIDGE RETROGRADING
INTO THE NE PAC. GFS ENSEMBLES NOW HINTING AT HIGHER POPS CENTERED
AROUND THU NIGHT...AND AGAIN BY SUN. WILL CONTINUE WITH POPS WELL
BELOW CLIMO UNTIL THERE IS BETTER CONSISTENCY IN MODEL
SOLUTIONS. RW

&&

.AVIATION...A MIXED BAG OF FLIGHT CONDITIONS TONIGHT WITH IFR 
CEILINGS ALONG THE NORTH COAST...VFR ALONG THE CENTRAL COAST...MVFR 
CEILINGS ALONG THE COLUMBIA RIVER FROM KPDX TO KKLS...AND LIFR FOG 
SOUTH OF KSLE. THE ONLY SIGNIFICANT CHANGE FOR THE REST OF THE NIGHT 
MAY BE A LOWERING OF CEILINGS TO IFR ALONG THE COLUMBIA RIVER FROM 
KPDX TO KKLS. CONDITIONS WILL LIKELY STAY IFR IN THE WILLAMETTE 
VALLEY SOUTH OF KSLE THROUGH MON AFTERNOON. OTHER AREAS WILL LIKELY 
RETURN TO VFR BY THE AFTERNOON AS A BIT OF ONSHORE FLOW MIXES THE 
BOUNDARY LAYER UP.

KPDX AND APPROACHES...MVFR CEILINGS WILL LIKELY LOWER TO IFR BY 09Z 
AND CONTINUE UNTIL 18Z. VFR CONDITIONS ARE EXPECTED THEREAFTER.
&&

.MARINE...WINDS WILL REMAIN BELOW SMALL CRAFT LEVELS FOR THE NEXT 
SEVERAL DAYS. SEAS WILL REMAIN HIGH...GENERALLY BETWEEN 12 AND 16 FT 
THROUGH MON NIGHT. APPEARS THAT SEAS WILL SUBSIDE BELOW 10 FT EARLY 
TUE. &&

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