AREA FORECAST DISCUSSION

 
 FXUS66 KPQR 250432
 AFDPQR
 
 AREA FORECAST DISCUSSION
 NATIONAL WEATHER SERVICE PORTLAND OR
 832 PM PST TUE NOV 24 2009
 
 .SYNOPSIS...AN UPPER RIDGE WILL REMAIN OVER THE REGION THROUGH
 WEDNESDAY. A QUASISTATIONARY FRONT OFFSHORE WILL SAG INTO THE FAR
 NORTHWEST PART OF THE REGION LATE WEDNESDAY. AN UPPER TROUGH WILL DIG
 INTO THE BACK SIDE OF THE FRONT THURSDAY...BRINGING THE POTENTIAL FOR
 A GOOD DOSE OF RAIN TO COASTAL AREAS. THE FRONT WILL SHIFT INLAND
 THURSDAY NIGHT AND FRIDAY. HIGH PRESSURE WILL BUILD IN AGAIN OVER THE
 WEEKEND FOR A DRYING TREND.
 
 &&
 
 .SHORT TERM...THE N COASTAL WARM FRONT LIFTED N OF THE REGION THIS
 AFTERNOON...WITH MOSTLY CLEAR SKIES NOW ACROSS MOST AREAS. THIS WILL
 ALLOW AT LEAST PATCHY FOG TO FORM OVERNIGHT. AN UPPER RIDGE OVER THE
 REGION TONIGHT WILL PERSIST THROUGH WED...FOR THE POTENTIAL OF MILD
 TEMPS AGAIN. HOWEVER...IF THE FOG TAKES HOLD OVERNIGHT IT WILL BE
 DIFFICULT FOR THE NOV SUN TO OVERCOME THE OVERNIGHT VALLEY
 INVERSIONS. 
 
 MODELS IN GOOD AGREEMENT SHOWING THE OFFSHORE COLD FRONT SAGGING TO
 NEAR THE S WA/N OREGON COAST LATE WED...THEN PUSHING A LITTLE INTO SW
 WA WED NIGHT. ELSEWHERE MOISTURE AND POPS WILL REMAIN RATHER LOW
 THROUGH WED NIGHT. 
 
 00Z NAM AND GFS SIMILAR SHOWING AN UPPER TROUGH DIGGING INTO THE BACK
 SIDE OF THE OFFSHORE FRONT ON THU...CAUSING SOME BACKING OF THE FLOW
 AS THE SYSTEM INTENSIFIES. THIS MAY SLOW THE INLAND PROGRESSION OF
 THE FRONT UNTIL LATE THU AFTERNOON OR THU NIGHT. THERE APPARENTLY
 WILL BE AN ASSOCIATED SURFACE LOW LIFTING NNE JUST BEHIND THE FRONT
 THU NIGHT...WITH MODELS OFFERING DIFFERING SOLUTIONS SO FAR ON TRACK
 AND INTENSITY. CURRENT MODELS SUGGEST BREEZY/WINDY CONDITIONS BUT
 PROBABLY NO HIGH WINDS. RW  
 
 .LONG TERM...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...WARM FRONT CONTINUES TO LIFT NORTH THIS EVENING. 
 BASICALLY JUST HIGH LEVEL CLOUDS OVER THE TAF SITES. MOIST BOUNDARY 
 LAYER WILL ALLOW FOR VALLEY FOG FORMATION. ALREADY DOWN TO IFR AT 
 KTMK AND KAST. EXPECT AN INCREASE IN IFR OVERNIGHT...ESPECIALLY IN 
 THE WILLAMETTE VALLEY. COAST MAY BE MORE PATCHY IF LIGHT EAST DRIFT 
 DEVELOPS. MVFR CONDITIONS AND AREAS OF LIGHT RAIN WILL RETURN TO THE 
 SOUTH WA AND NORTH OREGON COAST LATE WED AFTERNOON. 00Z MODEL RUN 
 KEEPS RAIN OUT OF THE INLAND AREAS UNTIL AFTER 00Z THU. 
 
 KPDX AND APPROACHES...VFR CONDITIONS EXPECTED TO REMAIN THROUGH 12Z. 
 PATCHY FOG SHOULD DEVELOP AFTERWARD. POTENTIAL IS THERE FOR IFR 
 CONDITIONS AT THE TERMINAL. HOWEVER...SURFACE PATTERN SUGGESTS THERE 
 COULD BE A LITTLE EAST WIND...BUT IT MAY NOT DEVELOP AT THE TERMINAL 
 UNTIL AFTER 18Z. EXPECT VFR CONDITIONS AFTER 18Z. MID AND HIGH LEVEL 
 CLOUDS WILL INCREASE IN THE AFTERNOON. RAIN SHOULD HOLD OFF UNTIL 
 AFTER 06Z THU. WEISHAAR
 
 &&
 
 .MARINE...DROPPED THE SMALL CRAFT FOR HAZARDOUS SEAS EARLIER THIS 
 EVENING BASED ON LATEST BUOY OBS. REPORTING BUOYS RUNNING 7 TO 8 FT 
 AS OF 03Z. LATEST MODEL GUIDANCE CONTINUES TO SHOW SMALL CRAFT WIND 
 OVER THE OUTER WATERS OF ZONE 270...BUT PRIMARILY THE NORTHWEST 
 THIRD. SCALED BACK THE WIND TONIGHT AND WED MORNING...BUT MAINTAINED 
 THE SMALL CRAFT IN ZONE 270. SEAS GO ABOVE 10 FT LATE WED MORNING AS 
 THE NEXT FRONTAL SYSTEM APPROACHES. WIND EXPECTED TO EASE A BIT WED 
 AFTERNOON AS THE FRONTAL BOUNDARY STALLS OFFSHORE. MODELS IMPLY A 
 SECONDARY LOW PRES CENTER FORMING ON THE FRONT NEAR 42N 135W 12Z 
 THU. NEXT ROUND OF SMALL CRAFT WIND CONDITIONS TO START AFTER 12Z 
 THU IN THE SOUTH WATERS AND THEN SPREAD NORTH THANKSGIVING DAY. MAY 
 NEED GALES BY THAT TIME. WEISHAAR
 
 &&
 
 .PQR WATCHES/WARNINGS/ADVISORIES...
 WA/OR...SMALL CRAFT ADVISORY FOR WIND 10-60 NM CAPE SHOALWATER TO
   CASCADE HEAD THROUGH EARLY WED AFTERNOON.
 SMALL CRAFT ADVISORY FOR HAZARDOUS SEAS CAPE SHOALWATER
   TO FLORENCE LATE WED MORNING THROUGH THU AFTERNOON.
 SMALL CRAFT ADVISORY FOR ROUGH COLUMBIA RIVER BAR 
   CONDITIONS THROUGH MIDNIGHT.
 SMALL CRAFT ADVISORY FOR ROUGH COLUMBIA RIVER BAR CONDITIONS
   LATE WED MORNING THROUGH MID-AFTERNOON. 
 
 &&
 
 

 
 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.