AREA FORECAST DISCUSSION

 
 FXUS66 KPQR 222217
 AFDPQR
 
 AREA FORECAST DISCUSSION
 NATIONAL WEATHER SERVICE PORTLAND OR
 216 PM PST SUN NOV 22 2009
 
 .SYNOPSIS...SHOWERS CONTINUE TO SPREAD OVER THE FORECAST AREA IN COLD
 UNSTABLE WESTERLY FLOW ALOFT. HIGH PRES WILL BUILD OVER WESTERN
 OREGON LATER TODAY AND TONIGHT. A WARM FRONT OFF THE COAST ON MON
 WILL LIFT NE TOWARDS NW OREGON AND WESTERN WA...THEN STALL ON TUE.
 WED THE FRONT WILL FINALLY LIFT N INTO WA...BEFORE A COLD FRONT
 PUSHES SE THROUGH THE REGION LATE THU.
 &&
 
 .SHORT TERM...SATELLITE IMAGERY SHOWS A LARGE AREA OF SHOWERS OVER
 THE PACIFIC SPREADING OVER THE FORECAST AREA IN COLD UNSTABLE
 WESTERLY FLOW ALOFT. DOPPLER RADAR SHOWS THE SHOWER ACTIVITY
 CONTINUING...WITHOUT A LOT OF CHANGES IN INTENSITY...HOWEVER THEY ARE
 BECOMING A LITTLE MORE SCATTERED. LIGHTNING DETECTION DATA HAS SHOWN
 A FEW LIGHTNING STRIKES AND HAVE HAD A FEW REPORTS OF SMALL HAIL THIS
 AFTERNOON. OROGRAPHICS WILL CONTINUE TO WEAKEN THIS AFTERNOON AS H8
 FLOW WEAKENS...SO EXPECT SNOW ACCUMULATIONS TO DROP OFF CONSIDERABLY
 AND WILL PROBABLY DROP THE WINTER STORM WARNING WITH THE AFTERNOON
 PACKAGE. POST FRONTAL SHOWERS DROP OFF QUICKLY TONIGHT...LAST ON THE
 N PART OF THE CASCADES. 
 
 AN AREA OF WARM AIR ADVECTION SETS UP OVER THE NW PART OF THE
 FORECAST AREA MON...AND CONTINUES INTO TUE. A WEAK SHORTWAVE MOVES
 ACROSS THE TOP OF THE DEVELOPING UPPER RIDGE TUE...BRINGING THE BEST
 CHANCE FOR OVERRUNNING PRECIPITATION TO THE NW PART OF THE AREA ON
 MON NIGHT WITH THE SHORT WAVE MOVING THROUGH THE FORECAST AREA
 WEDNESDAY.
 
 .LONG TERM...MODELS IN SOME AGREEMENT ON BRINGING A FRONTAL SYSTEM
 AND ITS ASSOCIATED UPPER LEVEL TROF THROUGH THE REGION THU/THU NIGHT
 FOR A RETURN TO WET WEATHER. AFTER THIS SYSTEM MOVES THROUGH...THE
 WEAK HIGH PRES RIDGE REASSERTS ITSELF OVER THE FORECAST
 AREA...KEEPING MOST ENERGY NORTH OF FORECAST AREA.
 &&
 
 .AVIATION...MOSTLY VFR CONDITIONS WITH PLENTY OF SHOWERS MOST VFR 
 THOUGH ISOLATED MVFR. SHOWERS SHOULD BEGIN TO TAPER OFF TONIGHT AS 
 HIGH PRESSURE BUILDS IN. PRESSURE GRADIENT STAYS STRONG ENOUGH TO 
 KEEP AREA MIXY TONIGHT DIMINISHING ANY CHANCES FOR FOG AND SOUTH 
 VALLEY MAY BE A LITTLE CLEARER BUT DRY AIR IS FILTERING INTO THE 
 REGION AND THIS WILL LIKELY KEEP THEM FOG FREE AS WELL. NEXT 
 SYSTEM BEGINS TO MOVE IN MONDAY AFTERNOON WITH RAIN STARTING AFTER 
 18Z ON THE COAST.
 
 KPDX AND APPROACHES...VFR FOR THROUGH 12Z EXCEPT FOR ISOLATED MVFR 
 SHOWERS THEN INCREASING CHANCE FOR MVFR STRATUS MON MORNING AND THEN 
 THE NEXT FRONT APPROACHES AND WILL LIKELY SEE MVFR CIGS MON 
 AFTERNOON. WOLFE
 
 &&
 
 .MARINE...SOLID SMALL CRAFT WINDS WILL LET UP TONIGHT AND THEN 
 INCREASE AGAIN TO NEAR GALE BY TOMORROW MIDDAY WITH GUSTS NEAR 40 KT 
 BY TOMORROW AFTERNOON. SEAS AT 18 FT AND WILL DROP TONIGHT TO NEAR 
 11 FT BEFORE BUILDING TO THE MID TEENS ON MONDAY EVENING. WOLFE
 
 &&
 
 .PQR WATCHES/WARNINGS/ADVISORIES...
 WA/OR...GALE WATCH MONDAY MORNING THROUGH MONDAY AFTERNOON CAPE      
   SHOALWATER TO CASCADE HEAD.
 SMALL CRAFT ADVISORY FOR HAZARDOUS SEAS CAPE SHOALWATER TO   
  FLORENCE THROUGH MONDAY MORNING.
 SMALL CRAFT ADVISORY FOR WINDS CAPE SHOALWATER TO   
  FLORENCE THROUGH MONDAY MORNING.
 SMALL CRAFT ADVISORY FOR ROUGH COLUMBIA 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.