FXUS66 KPQR 261048
AFDPQR

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE PORTLAND OR
232 AM PST SAT DEC 26 2009

.SYNOPSIS...COOL AND DRY OFFSHORE FLOW WILL CONTINUE LATE INTO 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 WILL APPROACH FROM THE SOUTH.
IT MAY GIVE SOME LIGHT PRECIPITATION TO THE AREA...THOUGH CHANCES ARE
JUST AS LIKELY THAT IT WILL NOT. IF IT DOES BRING
PRECIPITATION...THERE IS A POSSIBILITY IT COULD BE OF THE FROZEN
NATURE INITIALLY IN SOME SPOTS INTERIOR LOWLANDS.

&&

.SHORT TERM...LARGE SCALE WATER VAPOR IMAGES SHOWING BLOCKING UPPER
RIDGE INLAND OVER THE WESTERN U.S IN THE PROCESS OF BEING UNDERCUT OR
PINCHED OFF FROM BOTH EAST AND WEST. TO THE WEST...A PACIFIC FRONT
HAS BEEN SLOWLY BULGING TOWARD CALIFORNIA BUT STALLED IN THE NORTH AS
IT PRESSES INTO THE STRONG RIDGE INLAND.  
IN THE MEANTIME...STABLE CONDITIONS OVER THE AREA. MUCH OF THE INLAND
AREAS HAVE BE STUCK IN A PERSISTENT TEMPERATURE INVERSION NOT MORE
THAN A 1000 FEET. FRI AFTERNOON SLE SOUNDING SHOWED INVERSION AT
AROUND 600 FEET...AND MODELS KEEP THIS PROFILE THROUGH AT LEAST
MONDAY...WITH THE INVERSION WEAKENING ON TUE. 
HOWEVER...AREAS EXPOSED TO THE EAST WIND GUSHING FROM THE GORGE ARE
GETTING A LOT OF MIXING. KTTD-KDLS PRES GRADIENT AROUND -11 MB. PEAK
GUST REPORTS IN THE GORGE ARE MOSTLY IN THE 50 MPH RANGE THOUGH 60
MPH LIKELY SUPPORTED GIVEN THE GRADIENT.  FORTUNATELY IT APPEARS THIS
STRENGTH OF WIND WILL REMAIN IN THE GORGE. NAM SUGGESTING PEAK
GRADIENTS OCCURRING AROUND THIS MORNING...THEN SLOWLY RELAXING THROUGH
SUN.

NEXT FORECAST CONCERN IS POTENTIAL FOR SOME TYPE OF FREEZING OR
FROZEN PRECIP INLAND ON SUN AS A WEAKENING DEFORMATION BAND SWINGS IN
FROM THE SOUTHWEST.  THERE WILL BE A POTENTIAL FOR SLEET OR FREEZING
RAIN TO OCCUR. SNOW APPEARS UNLIKELY OUTSIDE OF THE GORGE AND UPPER
HOOD RIVER VALLEYS. THE UNCERTAINTY LIES IN OUR CHANCES OF ACTUALLY
SEEING MEASURABLE RAIN FROM THIS EVENT AS MODELS SHOW THIS
DEFORMATION BAND FALLING APART AS IT MOVES INTO OUR CWA FROM THE
SOUTH ON SUN MORNING. THE SOUTHERN WILLAMETTE VALLEY SHOULD BE BELOW
FREEZING SUN MORNING GIVEN THE CURRENT STRONG INVERSION OVER THE PAST
FEW DAYS AND STAND THE BEST CHANCE TO RECEIVE -FZRA BEFORE MODERATING
LATER IN THE MORNING. AREAS TO THE NORTH...MAY ALSO SEE SOME -FZRA
SUN MORNING BUT CHANCES ARE SLIGHT. IT MAY TAKE TOO LONG OR IF AT
ALL...FOR THE PRECIPITATION TO ARRIVE...BY THEN IT WILL WARM UP. WILL
HOLD OFF ON ANY KIND OF ADVISORIES...BUT WILL ISSUE A SPECIAL WEATHER
STATEMENT ADDRESSING THE POSSIBILITY AND UNCERTAINTY OF FREEZING
PRECIPITATION IN THE INTERIOR LOWLANDS. 
MH

.LONG TERM...NO CHANGES. PREVIOUS DISCUSSION UNCHANGED.
THE FIRST OF SEVERAL SYSTEMS BEGINS SOMETIME MON AFTERNOON. LIGHT 
PRECIP MAY BE POSSIBLE EARLY TUE MORNING...BUT THE MAIN THREAT FOR 
MODERATE PRECIP IS TUE NIGHT. MODELS ARE IN GOOD AGREEMENT ON BOTH 
THE TIMING AND STRENGTH OF THIS NEXT SYSTEM. SHOWERS SEEM TO LINGER 
THROUGH THU MORNING...BUT AN UPPER RIDGE AMPLIFIES BEHIND THE FRONT. 
MODELS REMAIN INCONSISTENT FOR THE END OF THE WEEK. 
NEVERTHELESS...EXPECT WET WEATHER FOR THE LATTER PORTION OF NEXT 
WEEK. 500MB TEMPS BY FRI LOOK A FEW DEGREES WARMER THAN THE PREVIOUS 
WEEK. RIGHT NOW...MAINLY EXPECTING RAIN. RAMIREZ
&&

.AVIATION...OFFSHORE GRADIENTS ARE VERY STRONG THROUGH THE GORGE...
AROUND 10 MB FROM KTTD TO KDLS. THIS SUPPORTS GUSTS ABOVE 55 KT IN
THE WEST END OF THE GORGE AND LIKELY UP NEAR 40 KT OR SO NEAR
KTTD. THE GRADIENT EASES A BIT LATE TODAY AND TONIGHT BUT WILL
STILL BE AROUND 7 MB OR SO. GAP WINDS NEAR THE COAST OF 25 TO 30
MPH WILL CONTINUE TODAY AS WELL. THIS WILL KEEP THE COAST AND THE
NORTH END OF THE WILLAMETTE VALLEY AND AREAS ADJACENT TO THE
COLUMBIA RIVER VFR TODAY AND TONIGHT. STILL HAVE IFR AND LIFR IN
THE SOUTH VALLEY INCLUDING KEUG AND ALSO EXTENDING NORTH ALONG THE
CASCADE FOOTHILLS TO NEAR KUAO. WEST SIDE OF THE WILLAMETTE VALLEY
IS DRIER...BEING AFFECTED BY THE EAST WINDS FANNING OUT FROM THE
GORGE. THE SOUTH VALLEY MAY BE TOUGH AGAIN TO CLEAR OUT...BUT
FARTHER NORTH MAY ERODE FROM THE DRIER AIR. NORTH OF KKLS MAY ALSO 
SEE SOME FOG THIS MORNING AS WELL. EXPECT SOME RECURRENCE OF FOG 
TONIGHT BUT MAINLY SOUTH AND AWAY FROM THE GORGE. WILL HAVE TO WATCH 
FOR A BIT OF FREEZING RAIN OR SLEET SOUTH VALLEY LATE TONIGHT AS A 
WEAKENING DEFORMATION BAND LIFTS NORTH. TOLLESON

KPDX AND APPROACHES...VFR CONDITIONS WITH BRISK WINDS NEXT 24
HOURS. EVEN KHIO HAS DRIED OUT WITH DEWPOINTS IN THE LOWER 20S.
MAIN PROBLEM WILL BE STRENGTH OF EAST WINDS MUCH OF TODAY. TOLLESON
&&

.MARINE...OFFSHORE WIND PATTERN TO CONTINUE THROUGH SATURDAY
NIGHT...THEN CONTINUE SUNDAY AS WEAKENING DEFORMATION ZONE LIFTS
NORTH. WINDS MAY GUST TO 20 KT NEAR COASTAL GAPS IN THE NORTH
TODAY AND MORE LIKE 25 KT IN THE SOUTH...THEN MORE LIKE 25 KT
TONIGHT AND SUNDAY. SEAS ARE RUNNING BELOW THE GWW/ENP WAVE MODELS
BUT THE LONG PERIODS BEING FORECAST ARE CLOSE...AROUND 17 SECONDS.
STILL THINK WE HAVE A SHOT AT REACHING THE MID TEENS THIS WEEKEND
BUT POSSIBLY A BIT BELOW MODEL GUIDANCE. THE WAVE MODELS SHOW A
SECOND SURGE COMING IN LATER SATURDAY BACK UP CLOSE TO 18 SECONDS.
SEAS LOOK TO REMAIN ABOVE 10 FT THROUGH ABOUT MONDAY. NOT A LOT
OF CONFIDENCE IN THE LONGER RANGE...WITH ANOTHER SYSTEM TUE OR WED
AND ANOTHER LATE IN THE WEEK BOTH OF WHICH COULD INCREASE THE
WINDS. TOLLESON
&&

.PQR WATCHES/WARNINGS/ADVISORIES...
OR...AIR STAGNATION ADVISORY UNTIL 6 PM PST THIS EVENING FOR CENTRAL 
     WILLAMETTE VALLEY-SOUTH WILLAMETTE VALLEY.

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

PZ...SMALL CRAFT ADVISORY FOR WINDS UNTIL 4 PM PST SUNDAY FOR COASTAL
     WATERS FROM CAPE SHOALWATER WA TO FLORENCE OR.

     SMALL CRAFT ADVISORY FOR HAZARDOUS SEAS UNTIL 10 PM PST MONDAY 
     FOR COASTAL WATERS FROM CAPE SHOALWATER WA TO FLORENCE OR.

     SMALL CRAFT ADVISORY FOR ROUGH COLUMBIA RIVER BAR UNTIL 6 AM PST
     SUNDAY.

&&

$$

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.