AREA FORECAST DISCUSSION

 
 FXUS66 KPQR 241037
 AFDPQR
 
 AREA FORECAST DISCUSSION
 NATIONAL WEATHER SERVICE PORTLAND OR
 235 AM PST TUE NOV 24 2009
 
 .SYNOPSIS...A WEAK COLD FRONT DRAPED ACROSS SW WASHINGTON AND NW
 OREGON THIS MORNING WILL LIFT NORTHWARD LATER TODAY AS A RIDGE OF
 HIGH PRESSURE BUILDS INTO THE REGION. THE NEXT FRONTAL SYSTEM WILL 
 MOVE INTO THE AREA ON THURSDAY.
 
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 .SHORT TERM...SATELLITE IMAGERY THIS MORNING SHOWS A WEAK FRONT OVER 
 THE FORECAST AREA WITH SOME LIGHT RAIN REPORTED ON THE NORTH COAST  
 OVERNIGHT.  THE FRONT WILL REMAIN OVER THE FORECAST AREA THIS 
 MORNING...THEN LIFT BACK TO THE NORTH LATER TODAY AND TONIGHT AS AN 
 UPPER LEVEL RIDGE AMPLIFIES OVER THE REGION. MOISTURE AND POPS WILL 
 DECREASE TONIGHT WITH A DRY DAY EXPECTED ON WED...WHICH WILL SET THE 
 STAGE FOR SOME FOG IN THE VALLEYS WED MORNING.  
 
 THE NEXT FRONT HAS BEEN GIVING MODELS SOME PROBLEMS WITH TIMING AND
 STRENGTH OF FEATURES. CURRENT MODEL SUITE SHOWS A FAIRLY
 SHARP UPPER TROUGH DIGGING INTO THE EASTERN PAC THU...PUSHING A
 DECENT COLD FRONT INTO THE AREA DURING THE DAY. THUS...IT LOOKS LIKE 
 A WET THANKSGIVING DAY...PARTICULARLY IN THE AFTERNOON. REFINEMENTS 
 TO THE FORECAST WILL CONTINUE AS THIS SYSTEM EVOLVES. TW
 
 .LONG TERM...NO CHANGES. PREVIOUS DISCUSSION FOLLOWS...THE MODELS
 SHOW A SYSTEM MOVING THROUGH THURSDAY NIGHT AND FRIDAY THAT SHOWS
 SOME SIGNS OF SPLITTING WITH SOME OF THE ENERGY DIGGING INTO NORTHERN
 CALIFORNIA...SO AM NOT GOING QUITE AS CONSOLIDATED AS THE LATEST 12Z
 GFS MODEL. A TRAILING SHORT WAVE FROM THE NORTHWEST KEEPS A BIT OF
 PRECIPITATION GOING FRIDAY NIGHT INTO SATURDAY. THEN THE MODELS SHOW
 SOME RIDGING OVER THE PACIFIC NORTHWEST DUE TO A DIGGING/DEVELOPING
 SYSTEM OUT 140W. THIS SHOULD BRING DRYING WITH THE INCREASED
 POSSIBILITY OF VALLEY FOG. THE MODELS DIVERGE FOR EARLY NEXT WEEK
 WITH THE LAST COUPLE OF ECMWF RUNS WHILE THE GFS IS DRY STILL.
 HOWEVER...THE GFS ENSEMBLES HAVE A VERY LARGE SPREAD AT THAT POINT.
 FOR NOW HAVE GONE WITH SOME POP FOR MONDAY BUT BELOW CLIMO TO ACCOUNT
 FOR THE ECMWF AND THE ENSEMBLE SPREAD. TOLLESON
 
 &&
 
 .AVIATION...A SLOW MOVING WARM FRONT PUSHES NORTH THROUGH THE CWA 
 TODAY...WITH THE LARGEST AFFECT TO THE NORTH COAST AND NORTH 
 INTERIOR. MVFR CONDITIONS AND AREAS OF LIGHT RAIN WILL LIKELY 
 CONTINUE ON THE COAST TODAY. INLAND AREAS WILL REMAIN LARGELY VFR 
 THOUGH LOCAL MVFR CONDITIONS MAY DEVELOP DURING THE MORNING HOURS AS 
 LOW LEVEL MOISTURE LINGERS.
 
 KPDX AND APPROACHES...VFR CONDITIONS SOME LOCAL MVFR DEVELOPING 
 11Z-16Z AS AREAS OF LIGHT RAIN DEVELOP. AREAS MVFR MAY LINGER 
 THROUGH THE MORNING BUT BACK TO VFR BY AFTERNOON.
 
 &&
 
 .MARINE...LOW PRESSURE IS MOVING INTO BRITISH COLUMBIA TODAY... 
 PUSHING A WARM FRONT INTO WASHINGTON AND OREGON. ASSOCIATED COLD 
 FRONT EXTENDS SW FROM LOW AND WILL NOT DIRECTLY MOVE THROUGH WATERS 
 UNTIL MIDWEEK. SMALL CRAFT WINDS CONTINUE AS THE WARM FRONT MOVES 
 NORTH THROUGH THE WATERS TODAY.. WEST SWELL CONTINUES ABOVE 10 FT 
 THIS EVENING THROUGH TUE. GENERALLY TRANQUIL WEATHER EXPECTED INTO 
 WED...THEN THE COLD FRONT MOVES ACROSS THE COASTAL WATERS WED 
 NIGHT/THU. SOME MODELS SHOW THE POSSIBILITY OF A STRONG LOW 
 DEVELOPING ALONG THIS FRONT OFF THE OREGON COAST WED NIGHT OR EARLY 
 THU. THIS MAY PRODUCE GALES DURING THAT TIME PERIOD. 
 
 &&
 
 .PQR WATCHES/WARNINGS/ADVISORIES...
 WA/OR...SMALL CRAFT ADVISORY FOR HAZARDOUS SEAS CAPE SHOALWATER TO   
   FLORENCE OUT 0-60 NM THROUGH LATE TONIGHT.
 SMALL CRAFT ADVISORY FOR ROUGH COLUMBIA RIVER BAR 
   THROUGH THIS EVENING.
 SMALL CRAFT ADVISORY FOR WINDS 10-60 NM CAPE SHOALWATER
   TO CASCADE HEAD THROUGH THIS EVENING.
 SMALL CRAFT ADVISORY FOR WINDS 0-10 NM CAPE SHOALWATER
   TO CASCADE HEAD THROUGH THIS AFTERNOON.
 
 
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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.