FXUS66 KPQR 252230
AFDPQR

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE PORTLAND OR
227 PM PST FRI DEC 25 2009

.SYNOPSIS...COOL AND DRY OFFSHORE FLOW WILL CONTINUE LATE INTO THE
WEEKEND. WIDESPREAD FREEZING FOG WILL DEVELOP IN THE CENTRAL AND
SOUTHERN WILLAMETTE VALLEY TONIGHT...THEN GRADUALLY BURN AWAY ON
SATURDAY. 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 OF THE WILLAMETTE VALLEY.

&&

.SHORT TERM...VISIBLE SATELLITE IMAGERY SHOWS FAR MORE CLEARING OF 
VALLEY FOG AND LOW CLOUDS VERSUS YESTERDAY AFTERNOON. IN THE CENTRAL 
AND SOUTHERN WILLAMETTE VALLEY...STILL HAVE SOME CLOUDS CLINGING TO 
THE CASCADE FOOTHILLS SOUTH OF MOLALLA...THEN COVERING MOST OF THE 
VALLEY AS FAR SOUTH AS EUGENE. FOG AND LOW CLOUDS WILL SPREAD BACK 
ACROSS THE CENTRAL AND SOUTHERN VALLEYS TONIGHT...AND WITH TEMPS 
BELOW FREEZING...WILL SEE WIDESPREAD FREEZING FOG DEVELOP SHORTLY 
AFTER DARK TONIGHT FOR AREAS SOUTH OF SALEM. DRIVERS ARE ENCOURAGED 
TO EXERCISE CAUTION WHILE DRIVING HOME FROM SOCIAL GATHERINGS 
TONIGHT AS THESE CONDITIONS COULD MAKE SECONDARY ROADS AND POSSIBLY 
BRIDGES AND OVERPASSES SLIPPERY. OFFSHORE FLOW WILL CONTINUE THROUGH 
SAT FOR CLEAR SKIES MOST PLACES. WILL ALSO BE QUITE BREEZY IN THE 
VICINITY OF THE GORGE...WITH GUSTS TO 40-45MPH POSSIBLE NEAR 
TROUTDALE THROUGH TONIGHT. WILL NOT ISSUE WIND ADVISORY HOWEVER AS 
GUSTS OVER 40 MPH SHOULD BE CONFINED TO THE WEST ENTRANCE OF THE 
GORGE.

UPPER RIDGE AXIS WILL SHIFT EAST TO IDAHO ON SAT AND ALLOW FOR EVEN
MORE CLEARING OF INLAND FOG/LOW CLOUDS SAT AFTERNOON. WILL LEAVE
CURRENT AIR STAGNATION ADVISORIES UP THROUGH SAT MORNING AS LOW LEVEL
INVERSION STILL QUITE STRONG THROUGH THAT TIME AND WILL NOT SEE MUCH
MIXING OF LOW LEVELS.

NEXT FORECAST CONCERN IS POTENTIAL FOR SOME TYPE OF FROZEN PRECIP
INLAND ON SUN. PAC NW CURRENTLY UNDER HIGH AMPLITUDE RIDGE THAT IS
PART OF AN OMEGA BLOCK...WITH STRONG UPPER LOWS OVER THE GULF OF
ALASKA AND THE CENTRAL/EASTERN CONUS. AS RIDGE AXIS SHIFTS EAST
TOMORROW...DISTURBANCES WILL BEGIN TO ROTATE NWRD AROUND THE EASTERN
PERIPHERY OF THE GOA UPPER LOW. THE FIRST ONE WILL MOVE INTO THE
EUGENE AREA AROUND DAYBREAK SUN MORNING...AND TO THE NORTHERN ZONES
BY THAT EVENING. WITH OFFSHORE FLOW IN PLACE AS THIS HAPPENS...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. AT THIS
POINT...HAVE KEPT -FZRA OUT OF THE CENTRAL AND SOUTHERN VALLEYS...BUT
HAVE ADDED SOME IN THE NRN WILLAMETTE VALLEY WHERE GORGE OUTFLOW WILL
AID IN KEEPING SURFACE TEMPS COOLER FOR LONGER ON SUN MORNING.
LIKEWISE...IF THE FOG AND LOW CLOUDS DO NOT ERODE IN THE SRN VALLEY
TOMORROW...TEMPS COULD VERY WELL BE SUB-FREEZING SAT NIGHT AND SUN
FOR GOOD CHANCE OF -FZRA THERE TOO.

THAT BEING SAID...HAVE ONLY GONE WITH SLIGHT CHANCE POPS WITH THIS
FEATURE AS FORCING IS WEAK TO BEGIN WITH...AND ONLY DECREASES AS SUN
WEARS ON. WILL HOLD OFF ON ANY KIND OF ADVISORIES OR STATEMENTS AND
SEE WHAT FUTURE MODEL RUNS BRING W/REGARD TO QPF...BUT I HAVE MY
DOUBTS THAT WE WILL SEE MUCH AT ALL...ESPECIALLY NORTH OF SALEM.
DALTON

.LONG TERM...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...MORE CLEARING TODAY IN THE WILLAMETTE VALLEY WITH DRIER 
NE TO E LOW-LEVEL FLOW. KTTD-KDLS GRADIENT CLOSE TO -10.0 MB AS OF 
21Z AND KOTH-KGEG OVER -13.0 MB. THESE GRADIENTS SHOULD STRENGTHEN A 
BIT MORE DURING THE NEXT 24 HOURS. THE END RESULT OF THIS WILL BE 
VFR OVER MUCH OF THE AREA. CENTRAL AND SOUTH PARTS OF THE WILLAMETTE 
VALLEY WILL HAVE CONSIDERABLE IFR TO LIFR AFTER 02Z...ESPECIALLY IN 
THE VICINITY OF KEUG. KTTD GUSTING TO NEARLY 40 KT AND WILL LIKELY 
SEE GUSTS UP TO 45 KT AT TIMES.  

KPDX AND APPROACHES...EAST WIND FINALLY KICKED IN AT KPDX ONCE THE 
KPDX-KTTD GRADIENT DROPPED BELOW 0.5 MB. AT 21Z THE GRADIENT WAS 
ACTUALLY SLIGHTLY NEGATIVE. EAST WIND MAY BACK OFF SOME TONIGHT... 
BUT PICK UP AGAIN SAT. WILL NEED TO WATCH FOR LOCALIZED IFR OR LIFR 
IN SHALLOW FREEZING FOG IN VALLEYS ON WESTERN APPROACHES AFTER 04Z. 
OTHER THAN THAT...EXCELLENT VFR FOR THE NEXT 24 HOURS. WEISHAAR 
&&

.MARINE...OFFSHORE PATTERN TO CONTINUE THROUGH SATURDAY NIGHT.
CURRENT SMALL CRAFT FOR WIND LOOKS GOOD. BUOYS AND NEAR-SHORE 
STATIONS REPORTING GUSTS IN THE 20 TO 25 KT RANGE. THIS WILL MAINLY 
BE A GAP WIND EVENT. SEAS WILL STAY JUST UNDER 10 FT THROUGH ABOUT 
06Z SAT...AND THEN BUILD AS A LONG-PERIOD SWELL TRAIN ARRIVES. SEAS 
TO PEAK NEAR 16 FEET OR SO SAT AND SUN. 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. NOT A LOT OF CONFIDENCE IN THE LONGER RANGE...BUT GFS 
HINTS AT A POTENTIAL GALE EVENT LATE NEXT THURSDAY OR THURSDAY 
NIGHT. 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 MONDAY AFTERNOON FOR COASTAL COASTAL WATERS FROM CAPE 
     SHOALWATER WA TO FLORENCE OR.

     SMALL CRAFT ADVISORY FOR ROUGH COLUMBIA RIVER BAR THROUGH
     SATURDAY AFTERNOON.

&&

$$

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.