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AREA FORECAST DISCUSSION

 
 FXUS66 KPQR 251101
 AFDPQR
 
 AREA FORECAST DISCUSSION
 NATIONAL WEATHER SERVICE PORTLAND OR
 300 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 VALLEY AND THE NORTH COAST THIS MORNING. THE FOG MAY TAKE A 
 WHILE TO DISSIPATE TODAY AS IT BECOMES MORE DIFFICULT FOR THE SOLAR 
 HEATING THIS TIME OF YEAR TO OVERCOME VALLEY INVERSIONS. 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. 
 
 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. 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...IFR FOG LIKELY IN SOUTH AND CENTRAL VALLEY THROUGH LATE 
 MORNING. AREAS FAVORING EAST WIND ARE LESS LIKELY TO STAY 
 IFR...MAINLY ALONG THE COAST AND NORTH VALLEY WHERE IN AND OUT OF 
 IFR IS MORE POSSIBLE. 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 AFTER MORNING FOG BURNS OFF.
 
 KPDX AND APPROACHES...VFR CONDITIONS COULD GIVE WAY TO IFR FOG EARLY 
 THIS MORNING. GOOD EASTERLY GRADIENTS EAST OF KPDX...BUT BETWEEN 
 KPDX AND KTTD GRADIENT IS WEAKLY POSITIVE. EAST WIND AT TERMINAL MAY 
 NOT DEVELOP UNTIL AFTER 18Z. 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 10 FT LATE THIS MORNING AS THE NEXT FRONTAL 
 SYSTEM APPROACHES. WIND 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  AFTER 12Z THU IN THE SOUTH WATERS...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.
 
 
 
 

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