FXUS66 KPQR 241619
AFDPQR

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE PORTLAND OR
820 AM PST THU DEC 24 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 SHROUDING MOST OF THE INTERIOR
LOWLANDS THIS MORNING. A DENSE FOG ADVISORY WAS ISSUED FOR THE SAME 
AREA. WITH TEMPERATURES NEAR OR JUST BELOW FREEZING...THE FOG IS 
HEAVY ENOUGH THAT THE DROPLETS ARE FREEZING...THEN FALLING AS ICE 
CRYSTALS. IN OTHER AREAS...FROST THAT FORMED OVERNIGHT REMAINS. 
OVERALL...THIS WILL MAKE FOR SLIPPERY BRIDGES AND LESS TRAVELS 
STREETS ACROSS THE PORTLAND/VANCOUVER METRO AREA THROUGH 10 AM. 

FOR THE REMAINDER OF THE AREA...SHALLOW INVERSION KEEPING 
CLOUDS IN THE VALLEYS WITH SLIGHTLY WARMER TEMPERATURES IN THE 
MOUNTAINS. 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 ARE IN EFFECT FOR NORTHERN CLARK COUNTY AND COWLITZ 
VALLEY AS WELL AS THE CENTRAL AND S WILLAMETTE VALLEY THROUGH SAT.

FOR AREAS NEAR AND THROUGH THE COLUMBIA GORGE EASTERLY WIND WILL BE
ON THE INCREASE TODAY. SURFACE HIGH PRES SLIDING INTO EASTERN OREGON
AND WASHINGTON FROM B.C. EAST TO WEST GRADIENT INCREASING WITH THE 
KPDX-KDLS GRADIENT AT 4 MB AND STEADILY INCREASING. SHOULD SEE ABOUT 
DOUBLE THAT GRADIENT LATE THIS AFTERNOON.  WINDS WILL PICK UP MORE 
RAPIDLY THIS AFTERNOON AS A STRONG OFFSHORE PRES GRADIENT SETS UP 
ALONG THE CASCADES. SUSTAINED WINDS WILL LIKELY PEAK OUT AROUND 35 
MPH WITH GUSTS TO 45 TO 50 MPH IN THE WINDIEST LOCATIONS SUCH AS 
ROOSTER ROCK. EAST WINDS WILL DIMINISH THIS WEEKEND.

.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...IFR TO LIFR THIS MORNING AT ALL INLAND VALLEY TAF SITES. 
DESPITE ALMOST -5.0 MB KTTD-DLS GRADIENT...THE EAST WIND HAS NOT 
GOTTEN TO KTTD YET. EAST WIND SHOULD GET TO KTTD BY 17Z AND TO KPDX 
19Z TO 20Z. OFFSHORE GRADIENT TODAY SHOULD BE ENOUGH TO REACH WEST 
PORTIONS OF THE NORTH WILLAMETTE VALLEY...LIKE KHIO...THIS 
AFTERNOON. WILL MAINTAIN LIFR AT KHIO THROUGH THE MORNING THEN CLEAR 
IT OUT RATHER QUICKLY AS NE TO E WIND DEVELOPS. THE CENTRAL AND 
SOUTH VALLEY WILL BE SLOW TO CLEAR OUT. EXPECT SOME REDEVELOPMENT OF 
LIFR CONDITIONS TONIGHT...ESPECIALLY SOUTH WILLAMETTE VALLEY. 
EXCELLENT CONDITIONS ALONG THE COAST. 

KPDX AND APPROACHES...PIREP SHORTLY BEFORE 1425Z INDICATED TOPS OVER 
KPDX AT 800 FEET. ACARS SOUNDING FROM KPDX AT 1415Z SHOWED EAST WIND 
OF 15 KT AT AROUND 1500 FT. LOOKING FOR EAST WIND TO SURFACE AT KPDX 
19Z TO 20Z AND THEN GRADUALLY INCREASE LATE THIS AFTERNOON. WILL NOT 
HAVE TO WORRY ABOUT FOG DEVELOPMENT TONIGHT AS THE OFFSHORE LOW 
LEVEL FLOW CONTINUES. WEISHAAR
&&

.MARINE...SEAS HOVERING CLOSE TO 10 FT THISM MORNING...MAINLY OVER 
THE OUTER WATERS. WILL MAINTAIN CURRENT SMALL CRAFT ADVISORY FOR 
HAZARDOUS SEAS. WILL LIKELY SEE A SHORT TIME PERIOD WHEN SEAS DROP 
BELOW 10 FT TONIGHT AND FRI...BUT THE LEADING EDGE OF ANOTHER SWELL 
TRAIN ARRIVES LATE FRI. OFFSHORE WIND PATTERN IS KICKING IN THIS 
MORNING...AND WILL HAVE SOME BREEZY CONDITIONS NEAR COASTAL GAPS 
TODAY. WINDS LOOK TO REACH SMALL CRAFT ADVISORY LEVELS TONIGHT INTO 
THE WEEKEND. NOT MUCH TO CHANGE IN THE FORECAST THIS MORNING. 
WEISHAAR
&&

.PQR WATCHES/WARNINGS/ADVISORIES...
OR...DENSE FOG ADVISORY UNTIL 10 AM PST THIS MORNING FOR CENTRAL 
     WILLAMETTE VALLEY-GREATER PORTLAND METRO AREA-LOWER 
     COLUMBIA-SOUTH WILLAMETTE VALLEY.

     AIR STAGNATION ADVISORY UNTIL 6 PM PST SATURDAY FOR CENTRAL 
     WILLAMETTE VALLEY-SOUTH WILLAMETTE VALLEY.

WA...AIR STAGNATION ADVISORY UNTIL 6 PM PST SATURDAY FOR GREATER 
     VANCOUVER AREA-I-5 CORRIDOR IN COWLITZ COUNTY.

     DENSE FOG ADVISORY UNTIL 10 AM PST THIS MORNING FOR GREATER 
     VANCOUVER AREA-I-5 CORRIDOR IN COWLITZ COUNTY.

PZ...SMALL CRAFT ADVISORY FOR WINDS FROM 7 PM THIS EVENING TO 10 PM 
     PST SATURDAY FOR COASTAL COASTAL WATERS FROM CAPE SHOALWATER WA
     TO CASCADE HEAD OR

     SMALL CRAFT ADVISORY FOR HAZARDOUS SEAS UNTIL 10 PM PST FRIDAY
     FOR COASTAL WATERS FROM CAPE SHOALWATER WA TO FLORENCE OR FROM
     10 NM TO 60 NM OFFSHORE

     SMALL CRAFT ADVISORY FOR WINDS FROM 4 AM FRIDAY TO 10 PM PST
     SATURDAY FOR COASTAL WATERS FROM FROM CASCADE HEAD OR TO
     FLORENCE OR FROM 10 NM TO 60 NM OFFSHORE.

     SMALL CRAFT ADVISORY FOR HAZARDOUS SEAS FROM 7 AM THIS MORNING 
     TO 10 PM PST FRIDAY FOR COASTAL WATERS FROM CAPE SHOALWATER WA
     TO FLORENCE OR OUT 10 NM.

     SMALL CRAFT ADVISORY FOR ROUGH COLUMBIA RIVER BAR FROM 7 AM
     THIS MORNING 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.