FXUS66 KPQR 251648
AFDPQR

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE PORTLAND OR
847 AM PST FRI DEC 25 2009

.SYNOPSIS...COOL DRY OFFSHORE FLOW FOR REST OF THE WEEK...AS STORMS 
HOLD UP OVER THE N PAC. FOG WILL LINGER IN THE INLAND VALLEYS EXCEPT
AREAS SURROUNDING THE WESTERN PART OF THE COLUMBIA GORGE AS EAST
WINDS WILL BE PERSISTENT THROUGH THE WEEKEND. GUSTY EAST WINDS WILL
BE THE STRONGEST TODAY ON THE WEST END OF THE GORGE WITH GUSTS
APPROACHING 60 MPH POSSIBLE IN EXPOSED AREAS. ON SUN A WEAKENING
PACIFIC FRONT APPROACHES AND MAY GIVE SOME LIGHT PRECIPITATION IF
ANY.

&&

.SHORT TERM...FOG HAS CLEARED THROUGHOUGHT MOST OF THE PORTLAND METRO
AREA DUE TO DRY EAST WINDS ERODING THE FOG LAYER. HOWEVER...LOCALLY 
DENSE FOG STILL PERSISTS IN THE LOWER COLUMBIA AND SOUTH OF AURORA 
TO EUGENE THIS MORNING. CHRISTMAS TRAVELERS SHOULD BE CAUTIOUS AS 
THEY MAKE THEIR WAY OUT THIS MORNING. THICK FOG COMBINED WITH 
SUB-FREEZING TEMPERATURES THIS MORNING COULD CAUSE ROADS TO BE SLICK 
AS FREEZING FOG DEPOSITS ICE ON VARIOUS SURFACES. THIS SHOULD 
PRIMARILY BE A MORNING HAZARD HOWEVER AS TEMPS SHOULD MAKE IT ABOVE 
FREEZING BY MIDDAY OR EARLY AFTERNOON AT THE LATEST.

THE LOWER COLUMBIA AND AREAS IN THE WILLAMETTE VALLEY THAT ARE NORTH
OF SALEM WILL LIKELY SEE THE FOG LIFT AND BREAK UP ENOUGH FOR SOME
SUN BREAKS LATER TODAY. HOWEVER...THE SOUTH WILLAMETTE VALLEY LIKELY
REMAIN IN THE SOUP NEXT DAY OR TWO. STRATUS DEEPENING EAST OF THE
CASCADES IS PUSHING ACROSS EASTERN PARTS OF SOUTH WASHINGTON CASCADES
AND TO NEAR MOUNT HOOD. DUE TO INVERSIONS AND LIGHTER WINDS BENEATH
THEM...WILL HAVE SOME PROBLEM MIXING OUT AIR MASS IN LOWER ELEVATIONS
TO THE N OF VANCOUVER AND S OF SALEM THROUGH SATURDAY. WILL CONTINUE
AIR STAGNATION ADVISORIES IN THOSE AREAS...FOR ELEVATIONS BELOW ABOUT
1500 FEET. 

THE STRONG SURFACE HIGH PRES E OF THE CASCADES COUPLED WITH THE LOW 
LEVEL INVERSION HAS CREATED A STRONG E TO W PRESSURE GRADIENT 
THROUGH THE GORGE. PRES GRADIENT FROM TTD TO DLS IS UP TO 9.1 MB AS
OF 8 AM THIS CHRISTMAS MORNING. MODELS SUGGEST THE GRADIENT WILL PEAK
AROUND 10 MB TODAY. REMNANT FOG LAYER IN/AROUND THE PORTLAND METRO
AREA HAS CREATED A SMALL MESOSCALE HIGH BETWEEN BASICALLY SPB AND
TTD. THIS HAS KEPT STRONGEST WINDS TROUTDALE EAST SO FAR...BUT WITH
FOG CLEARING A LITTLE MORE TODAY THAN YESTERDAY...EXPECT SOME GUSTY
EAST WINDS TO SPILL WESTWARD AS FAR AS DOWNTOWN PORTLAND. DESPITE
STRONG GRADIENTS...WILL NOT GO WITH ANY KIND OF WIND HEADLINES FOR
THE GORGE OR NRN WILLAMETTE VALLEY OR CLARK COUNTY AREAS. WILL NEED
TO MONITOR THESE AREAS HOWEVER AS HI-RES MODEL CROSS SECTIONS SHOW
45-50KT EASTERLY WINDS DEVELOPING OVERHEAD LATER THIS EVENING.

SATURDAY BEGINS TRANSITION PERIOD...AS A FRONT NOW ABOUT 600 MILES
OFFSHORE APPROACHES THE WEST COAST. CHANCES FOR PRECIPITATION
INCREASE SAT NIGHT INTO SUN. CONFIDENCE IS NOT VERY HIGH AT THIS TIME
IF MEASURABLE PRECIPITATION WILL FALL.NAM...ECMWF...AND CANADIAN
SPLIT THE INCOMING FRONT WITH PRECIPITATION HEADED TO THE SOUTH WHERE
MORE OF THE JET ENERGY GOES. GFS BRINGS A WEAKENING FRONT INLAND WITH
SOME LIGHT PRECIPITATION. PRECIPITATION TYPE IS ANOTHER
CONCERN...CURRENT CONDITIONS ARE MARGINAL FOR FREEZING RAIN
INLAND...BUT THE COLUMBIA GORGE WOULD BE THE BEST CANDIDATE FOR
FREEZING RAIN AND SNOW...IF...THE GFS SOLUTION WORKS OUT.  MAY HAVE
BETTER FEEL FOR THIS SCENARIO LATER TODAY AND SATURDAY SHOULD MODELS
NARROW ON POSSIBLE OUTCOMES.

.LONG TERM...NO CHANGES. PREVIOUS DISCUSSION FOLLOWS.
MODELS CONTINUE TO BREAK DOWN A PERSISTENT UPPER LEVEL RIDGE THROUGH 
SUN AFTERNOON. PREVIOUSLY THOUGHT TO TRAVEL DIRECTLY TOWARDS THE PAC 
NW...A SYSTEM TRACKS TOWARDS NORTHERN CALIF. NOT LIKELY THE CWA WILL 
SEE ANY PRECIP WITH THIS PARTICULAR SYSTEM. GFS AND ECMWF DISAGREE 
ON A SECOND SYSTEM BY TUE. ECMWF IS FASTER...HAVING THE ASSOCIATED 
COLD FRONT ARRIVE EARLY TUE. GFS HAS A RIDGE RETURN...PUSHING THIS 
UPPER LOW INTO THE REGION BY LATE WED. NEVERTHELESS...EXPECT WET 
WEATHER FOR THE REMAINDER OF NEXT WEEK. 500MB TEMPS BY FRI LOOK A 
FEW DEGREES WARMER THAN THE PREVIOUS WEEK. RIGHT NOW...ANY PRECIP 
FOR LATE NEXT WEEK WILL PROBABLY BE RAIN. RAMIREZ
&&

.AVIATION...OFFSHORE LOW-LEVEL FLOW CONTINUING TO STRENGTHEN. AT 16Z 
THE KTTD-KDLS GRADIENT WAS -9.2 MB. WIND GUSTS 40-45 KT NOT OUT OF 
THE QUESTION FOR KTTD. CENTRAL AND SOUTH WILLAMETTE VALLEY WILL BE 
IFR TO LIFR. KSLE MAY HAVE A BETTER CHANCE OF SEEING SOME 
SHORT-LIVED VFR LATE IN THE DAY. NOT MUCH CHANGE IN THE OVERALL 
PATTERN FOR THE NEXT 24 HOURS. 

KPDX AND APPROACHES...KEEP TRYING TO FORECAST EAST WIND AT THE 
TERMINAL BUT IT JUST DOES NOT WANT TO SURFACE. MAIN PROBLEM IS THE 
POSITIVE KPDX-KTTD GRADIENT. TYPICALLY...IF THAT GRADIENT IS ABOVE 
0.5 MB THE EAST WIND DOES NOT SURFACE. AT 16Z IT WAS 0.7 MB. THIS IS 
ALSO A FAIRLY SHALLOW EVENT...NOT GETTING ANY HELP FROM ALOFT. IN 
ANY EVENT...STILL EXPECT EAST WIND TO KICK IN AROUND 18Z. NOT SURE 
ABOUT KHIO BUT WILL GO FOR SOME E-NE WIND THERE IN THE AFTERNOON. 
WILL KEEP VFR CONDITIONS AT KPDX THROUGHOUT THE 24-HOUR PERIOD IN 
THE 18Z TAFS. MAY SEE EAST WIND DROP OFF A LITTLE TONIGHT 
WEISHAAR 
&&

.MARINE...OFFSHORE PATTERN TO CONTINUE THROUGH SATURDAY. CURRENT 
SMALL CRAFT FOR WIND LOOKS GOOD. BUOYS AND NEAR-SHORE STATIONS 
REPORTING GUSTS IN THE 20 TO 25 KT RANGE THIS MORNING. THIS WILL 
MAINLY BE A GAP WIND EVENT. SEAS JUST UNDER 10 FT TODAY AND 
TONIGHT...BUT NEXT LONG-PERIOD SWELL TRAIN ARRIVES EARLY SATURDAY. 
THE GFS MODEL IS STILL TRYING TO BRING UP SMALL CRAFT WINDS SATURDAY 
FROM A STRETCHING FRONT...WHILE THE ECMWF WEAKENS THE FRONT MORE DUE 
TO THE SPLITTING. HAVE GONE WITH AN AVERAGE OF THE WINDS...BUT THE 
ECMWF MAY END UP BEING BETTER. THE NEXT BETTER SHOT AT WIND WILL BE 
WITH A FRONT IN THE TUESDAY TO WEDNESDAY TIME FRAME. WEISHAAR
&&

.PQR WATCHES/WARNINGS/ADVISORIES...
OR...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.

PZ...SMALL CRAFT ADVISORY FOR WINDS UNTIL 10 PM PST SATURDAY
     FOR COASTAL COASTAL WATERS FROM CAPE SHOALWATER WA TO
     FLORENCE OR.

     SMALL CRAFT ADVISORY FOR HAZARDOUS SEAS FROM THIS EVENING
     THROUGH SUNDAY EVENING FOR COASTAL COASTAL WATERS FROM
     CAPE SHOALWATER WA TO FLORENCE OR.

     SMALL CRAFT ADVISORY FOR ROUGH COLUMBIA RIVER BAR TODAY
     AND TONIGHT.

&&

$$

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.