FXUS66 KPQR 240435
AFDPQR

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE PORTLAND OR
834 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...FOG AND LOW CLOUDS CONTINUE TO PERSIST THIS EVENING
THROUGHOUT THE LOWER ELEVATIONS OF THE WILLAMETTE VALLEY AS WELL AS
ALONG THE COLUMBIA RIVER FROM JUST WEST OF THE BONNEVILLE DAM TO
ROUGHLY KALAMA. THE COAST AND EVERYWHERE INLAND ABOVE THE INVERSION
HAD AN EXTREMELY NICE DAY WITH SUNSHINE AND HIGH TEMPS IN THE 40S
WHILE UNDER THE LOW CLOUDS TEMPERATURES REMAINED IN THE 30S.  THE
OFFSHORE PRESSURE GRADIENT HOWEVER IS FINALLY STARTING TO BUILD WHICH
WILL PUSH THE FOG OUT OF THE WESTERN GORGE LATE THIS EVENING AND WEST
OF TROUTDALE BY AROUND MIDNIGHT.

THE RIDGE ALOFT WILL CONTINUE TO STRENGTHEN AND SHARPEN A BIT 
TONIGHT...THEN SHIFT EAST SO THAT ITS AXIS ALONG THE COAST BY THU 
MORNING. IN RESPONSE OFFSHORE FLOW WILL INCREASE WITH EAST WINDS 
STRENGTHENING THROUGH THE COLUMBIA RIVER GORGE AND OTHER GAPS AND 
PASSES IN THE CASCADES. EAST WINDS WILL BUILD 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.  DUE TO INVERSIONS
AND LIGHTER WINDS...WILL HAVE SOME PROBLEM MIXING OUT AIR MASS IN
LOWER ELEVATIONS TO NORTH OF VANCOUVER AND SOUTH OF SALEM FOR NEXT
SEVERAL DAYS. IN COORDINATION WITH SEATTLE AND OTHER GOVT AGENCIES
AIR STAGNATION ADVISORIES HAVE BEEN ISSUED FOR NORTHERN CLARK COUNTY
AND COWLITZ VALLEY AS WELL AS THE CENTRAL AND SOUTHERN WILLAMETTE
VALLEY THROUGH SAT. RUTHFORD

.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...LIFR AT ALL VALLEY TAF SITES. KTTD-KDLS GRADIENT AT
04Z IS -2.4 MB. 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. 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. 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. WOLFE/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...AIR STAGNATION ADVISORY FOR THE CENTRAL AND SOUTHERN WILLAMETTE 
VALLEY THROUGH SAT.
PZ...SMALL CRAFT ADVISORY FOR HAZARDOUS SEAS FROM 10 AM THURSDAY TO 
10 PM PST FRIDAY FOR COASTAL WATERS FROM CAPE SHOALWATER WA 
TO FLORENCE OR OUT 60 NM.
     SMALL CRAFT ADVISORY FOR ROUGH COLUMBIA RIVER BAR FROM 10 AM 
THURSDAY TO 4 AM PST FRIDAY.

&&

$$

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.