FXUS66 KPQR 232158
AFDPQR

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE PORTLAND OR
200 PM PST WED DEC 23 2009

.SYNOPSIS...COOL DRY OFFSHORE FLOW FOR REST OF THE WEEK...AS STORMS 
HOLD UP OVER THE N PAC. WILL SEE FOGGY WEATHER IN THE CENTRAL AND 
SOUTH WILLAMETTE VALLEY NEXT SEVERAL DAYS...BUT EAST WINDS WILL KEEP 
OTHER AREAS PARTLY TO MOSTLY SUNNY. 
&&

.SHORT TERM...PLEASANT SUNNY DAY ACROSS MUCH OF THE REGION...EXCEPT 
FOR THE WILLAMETTE VALLEY AND CLARK COUNTY WHERE LOW CLOUDS AND FOG 
PERSIST. WILL SEE LITTLE CHANGE THIS EVENING...AS THE LOW CLOUDS AND 
FOG WILL PERSIST. MAY SEE AREAS OF DENSE FOG AGAIN TONIGHT...MAINLY 
FROM HILLSBORO TO AURORA AND SOUTHWARD. ONCE EAST WINDS DEVELOP 
LATER TONIGHT...WILL SEE SOME CLEARING AROUND TROUTDALE AND EAST 
PARTS OF PORTLAND/VANCOUVER. 

THE RIDGE ALOFT WILL CONTINUE TO STRENGTHEN AND SHARPEN A BIT 
TOMORROW...THEN SHIFT EAST SO THAT ITS AXIS ALONG THE COAST BY THU 
AM. IN RESPONSE OFFSHORE FLOW WILL DEVELOP WITH EAST WINDS 
STRENGTHENING THROUGH THE COLUMBIA RIVER GORGE AND OTHER GAPS AND 
PASSES IN THE CASCADES. EAST WINDS WILL INCREASE GRADUALLY 
TONIGHT...REACHING THE 15 TO 20 KT RANGE IN THE W GORGE. WINDS WILL 
PICK UP MORE RAPIDLY THU AS A STRONG OFFSHORE PRES GRADIENT SETS UP 
ALONG THE CASCADES. SUSTAINED WINDS WILL LIKELY PEAK OUT AROUND 40 
OR 45 KNOTS WITH GUSTS TO 50 OR 60 KNOTS IN THE WINDIEST LOCATIONS 
SUCH AS ROOSTER ROCK. EAST WINDS WILL DIMINISH THIS WEEKEND.

ASIDE FROM THE INCREASING GAP WINDS...FOG IN THE WIND SHELTERED
VALLEYS INCLUDING MUCH OF THE WILLAMETTE VALLEY WILL BE THE MAIN 
FORECAST CHALLENGE FOR THE REMAINDER OF THE WEEK. HAVE ADJUSTED 
TEMPS FOR A BIT WARMER ON THE HIGHER TERRAIN ABOVE THE LOWLAND 
INVERSION...AND BIT COOLER THROUGH THE COLUMBIA GORGE AND INTERIOR 
VALLEYS. PLENTY OF COOL AIR ON EAST SIDE...WHICH WILL SPILL 
WESTWARD. WILL PUSH NIGHT TEMPS DOWN INTO THE 20S FOR MOST AREAS OF 
LOWLANDS...BUT IN WIND SHELTERED AREAS MAY BE A BIT COLDER. 

DUE TO INVERSIONS AND LIGHTER WINDS...WILL HAVE SOME PROBLEM MIXING 
OUT AIR MASS IN LOWER ELEVATIONS TO NORTH OF VANCOUVER AND TO SOUTH 
OF SALEM FOR NEXT SEVERAL DAYS. IN COORDINATION WITH SEATTLE AND 
OTHER GOVT AGENCIES...HAVE ISSUED AIR STAGNATION ADVISORY FOR 
NORTHERN CLARK COUNTY AND COWLITZ VALLEY FOR THU THROUGH SAT. MAY 
NEED SIMILAR ADVISORY FOR CENTRAL AND SOUTH WILLAMETTE VALLEY...BUT 
WILL WAIT UNTIL THU AM BEFORE MAKING THAT CALL.            ROCKEY

.LONG TERM...MODELS AGREE THAT A PERSISTENT UPPER LEVEL RIDGE WILL 
BREAK DOWN SOMETIME SUN AS A SYSTEM APPROACHES THE REGION. 
HOWEVER...MODELS DO DISAGREE ON THE STRENGTH OF THIS SYSTEM. GFS 
QUICKLY PUSHES THE SYSTEM ACROSS THE PAC NW FOLLOWED BY SEVERAL 
SYSTEMS NEXT WEEK. ECMWF SHOWS THIS PARTICULAR SYSTEM IMPACTING THE 
AREA THROUGH MON NIGHT. EITHER WAY...HAVE KEPT POPS SLIGHTLY BELOW 
CLIMATOLOGY GIVEN MODEL INCONSISTENCIES. EXPECT PRECIP THROUGH THE 
REMAINDER OF NEXT WEEK.                                  LRAMIREZ
&&

.AVIATION...OBVIOUSLY WAS TOO OPTIMISTIC IN THE 18Z TAFS REGARDING 
IMPROVEMENT. VISIBLE IMAGERY AT 22Z CLEARLY SHOWS FOG AND LOW CLOUDS 
HANGING TOUGH THROUGHOUT THE WILLAMETTE VALLEY. EXPECT A RETURN TO 
LIFR AT ALL VALLEY TAF SITES BY 03Z. KTTD-KDLS GRADIENT AT 22Z WAS 
FLAT...NEAR ZERO...BUT BUT WILL START GOING OFFSHORE THIS EVENING. 
EXPECT EAST WIND 15G25KT AT KTTD BETWEEN 10Z AND 12Z...THEN 
INCREASING EVEN MORE THU. OFFSHORE GRADIENT THU SHOULD BE ENOUGH TO 
REACH WEST PORTIONS OF THE NORTH WILLAMETTE VALLEY...LIKE KHIO. IN 
THE 00Z TAFS WILL MAINTAIN LIFR AT KHIO THROUGH THU MORNING THEN 
CLEAR IT OUT RATHER QUICKLY AS NE TO E WIND DEVELOPS.  

KPDX AND APPROACHES...TOUGH FORECAST. MAIN FORECAST PROBLEM WILL BE 
ONSET OF EAST DRIFT. SLIGHT ONSHORE COMPONENT AS OF 22Z AS KPDX-KTTD 
SHOWED 0.3 MB. NOT LOOKING PROMISING AT ALL FOR MAJOR IMPROVMENT. 
VIS MAY GET IN TO MVFR AT 00Z...BUT CIGS WILL BE IFR. THE IFR TO 
LIFR CONDITIONS SHOULD PERSIST TO 06Z...AND POSSIBLY EVEN A LITTLE 
LONGER. WILL GO WITH AN EAST DRIFT BEGINNING AT 09Z. WIND PICKS UP 
THU MORNING. WILL NOT HAVE TO WORRY ABOUT FOG DEVELOPMENT THU NIGHT 
AS THE OFFSHORE LOW-LEVEL FLOW CONTINUES.               WEISHAAR
&&

.MARINE...OFFSHORE PATTERN WILL PERSIST THE REST OF THE WEEK. WILL 
NEED TO WATCH FOR SMALL CRAFT WIND NEAR THE COASTAL GAPS THU AND THU 
NIGHT AND HAVE INDICATED A FEW GUSTS TO 25 KT...BUT NOT WIDESPREAD 
ENOUGH TO WARRANT SMALL CRAFT. HAVE ISSUED A SMALL CRAFT FOR 
HAZARDOUS SEAS BEGINNING 18Z THU. MODEL GUIDANCE SEEMS TO BE A FOOT 
OR SO TOO HIGH AND HAVE ADJUSTED ACCORDINGLY. APPROACHING SYSTEM SAT 
MAY BE ENOUGH TO GENERATE SMALL CRAFT WIND OVER THE OUTER WATERS 
WITH SEAS PEAKING NEAR 15 FT SAT NIGHT AND SUN. WEISHAAR 
&&

.PQR WATCHES/WARNINGS/ADVISORIES...
WA...AIR STAGNATION ADVISORY FOR NORTHERN CLARK COUNTY AND THE
      I-5 CORRIDOR OF SW WASHINGTON FOR THU THROUGH SAT.

OR...NONE.

PZ...SMALL CRAFT ADVISORY FOR HAZARDOUS SEAS CAPE SHOALWATER TO
      FLORENCE LATE THU MORNING THROUGH FRI EVENING.
&&

$$

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.