AREA FORECAST DISCUSSION

 
 FXUS66 KPQR 220442
 AFDPQR
 
 AREA FORECAST DISCUSSION
 NATIONAL WEATHER SERVICE PORTLAND OR
 841 PM PST SAT NOV 21 2009
 
 
 .SYNOPSIS...A STRONG PACIFIC COLD FRONT WILL MOVE INLAND OVERNIGHT AS
 A DEEP SURFACE LOW OFF THE COAST MOVES NORTHEAST INTO WASHINGTON. 
 A WEAK RIDGE OF HIGH PRESSURE WILL FOLLOW SUNDAY AFTERNOON AND
 NIGHT...BEFORE THE NEXT FRONTAL SYSTEM ARRIVES LATER ON MONDAY. 
 
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 .SHORT TERM...MODELS ARE IN REASONABLY GOOD AGREEMENT SHOWING THE
 DEEP SURFACE LOW MOVING ONTO THE CENTRAL WA COAST OR POSSIBLY A BIT S
 AROUND 09Z. HOWEVER AT 00Z MODELS WERE ABOUT 4 MB TOO HIGH COMPARED
 WITH SHIP REPORTS W OF 130W NEAR THE LOW. MODELS ARE IN GOOD
 AGREEMENT ON THE UPPER FEATURES...WITH A STRONG SHORTWAVE MOVING
 ACROSS THE FORECAST AREA TONIGHT...DIGGING SLIGHTLY TO THE ESE.
 TIMING OF THE COLD FRONT IN ALL MODELS INDICATES FRONTAL PASSAGE ON
 THE COAST AROUND MIDNIGHT. HAVE ISSUED A HIGH WIND WARNING FOR THE
 WILLAPA HILLS TO GO ALONG WITH THE COASTAL WARNING AND INLAND VALLEY
 WIND ADVISORIES. WINDS INLAND LOOK GUSTY WITH THE FRONT BUT
 ESPECIALLY AFTER THE FRONT AND LOW MOVE INLAND AS THERE WILL BE 
 STRONG PRES RISES IN THE OVERNIGHT HOURS.
 
 DOPPLER RADAR SHOWS THE PRECIP FIELD HAS FINALLY SPREAD TO THE
 CASCADES THIS EVENING. WILL CONTINUE THE WINTER STORM WARNING FOR THE
 CASCADES AS MOISTURE...STRENGTH OF THE FRONT AND THE POST FRONTAL
 WESTERLY OROGRAPHIC FLOW ALL FAVOR SIGNIFICANT SNOWFALL FOR LATER
 TONIGHT AND SUN.
 
 A WEAK UPPER RIDGE WILL BUILD OVER THE FORECAST AREA SUN NIGHT AND
 MON FOLLOWING THE FRONT. BEST CHANCES FOR PRECIP MON AND TUE WILL
 SHIFT N INTO WA WITH WARM FRONT OVERRUNNING. THE UPPER RIDGE HOLDS
 COLD FRONT AT BAY UNTIL AFTER TUE NIGHT. RW
 
 .LONG TERM...NO CHANGES. PREVIOUS DISCUSSION FOLLOWS...WEAK HIGH PRES
 RIDGE OVER THE FORECAST AREA CONTINUES TO
 PUSH ENERGY NORTH OF FORECAST AREA MID WEEK. IT MANAGES TO DELAY THE
 ARRIVAL OF A SECOND SYSTEM THROUGH THUR. MODEL SOLUTIONS DIVERGE
 TOWARD THE END OF THE WEEK AND HAVE LITTLE CONFIDENCE IN THEM. AT
 THIS TIME WILL GO WITH CLIMATOLOGY UNTIL THERE IS SOME CONSISTENCY
 BETWEEN THE MODELS..
 
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 .AVIATION...AREAS OF MVFR CONDITIONS ALONG THE COAST THIS EVENING 
 WILL EXPAND INLAND TONIGHT AS THE RAIN SHIELD FROM THE NEXT STRONG 
 SYSTEM APPROACHES. SOUTH WINDS WILL INCREASE THROUGH 09Z AND THEN 
 TURN WESTERLY FROM WEST TO EAST AS THE ASSOCIATED STRONG COLD FRONT 
 SWINGS ACROSS THE AREA. A MIX OF VFR AND MVFR CONDITIONS ARE 
 EXPECTED SUNDAY MORNING IN STRONG UNSTABLE ONSHORE FLOW. 
 
 KPDX AND APPROACHES...VFR CONDITIONS ARE EXPECTED THROUGH 06Z...THEN 
 MVFR CONDITIONS WILL DEVELOP AS A COLD FRONT APPROACHES. SOUTH TO 
 SOUTHWEST WINDS MAY BECOME QUITE STRONG AROUND 12Z AS A STRONG 
 GRADIENT DEVELOPS OVER THE NORTH VALLEY AS THE LOW MOVES INLAND. 
 WIND GUSTS NEAR 50 MPH ARE POSSIBLE. A MIX OF VFR AND MVFR 
 CONDITIONS ARE EXPECTED SUNDAY MORNING IN STRONG UNSTABLE ONSHORE 
 FLOW. 
 
 &&
 
 .MARINE...GALE FORCE SOUTH WINDS WILL STRENGTHEN TO STORM FORCE 
 LATER THIS EVENING AS A POTENT LOW MOVES NORTH OF THE COASTAL WATERS 
 AND INLAND ALONG THE WASHINGTON COAST. WINDS WILL TURN W TO NW ON 
 SUNDAY AND BEGIN EASING. SEAS TONIGHT WILL LIKELY PEAK AROUND 20 FT 
 ...BUT WILL DROP QUICKLY TO THE MID TEENS ON SUN. 
 
 &&
 
 .PQR WATCHES/WARNINGS/ADVISORIES...
 WA/OR...STORM WARNING FOR THE COASTAL WATERS FROM CAPE SHOALWATER TO 
      FLORENCE THROUGH 3 AM SUNDAY MORNING. 
 SMALL CRAFT ADVISORY FOR ROUGH COLUMBIA RIVER BAR CONDITIONS 
      THROUGH SUN EVENING.
 WINTER STORM WARNING FOR THE S WA AND N AND CENTRAL OREGON
      CASCADES TONIGHT AND SUNDAY.
 HIGH WIND WARNING FOR THE S WA/N AND CENTRAL OREGON COAST...
      AND WILLAPA HILLS TONIGHT.
 WIND ADVISORY FOR THE WILLAMETTE VALLEY...THE LOWER 
      COLUMBIA...AND THE I-5 CORRIDOR FOR THIS EVENING
      THROUGH SUNDAY MORNING.
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 $$
 
 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.