FXUS66 KPQR 040423
AFDPQR

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE PORTLAND OR
820 PM PST THU DEC  3 2009

.SYNOPSIS...A SHARP UPPER RIDGE ALONG THE WEST COAST WILL PERSIST
OVER THE PACIFIC NORTHWEST WITH DRY WEATHER AND OFFSHORE FLOW THROUGH
EARLY FRIDAY. A WEATHER SYSTEM FROM THE GULF OF ALASKA WILL WEAKEN
THE RIDGE AS IT MOVES INTO BRITISH COLUMBIA...THEN SLIDES SOUTH INTO
THE PACIFIC NORTHWEST FRIDAY EVENING. ANY MOISTURE WITH THIS SYSTEM
WILL BE SPARSE BUT COULD FALL AS SNOW FLURRIES FRIDAY NIGHT AND EARLY
SATURDAY. A SECOND SYSTEM DROPPING SOUTH FROM BRITISH COLUMBIA ON
SUNDAY WILL BRING MODIFIED ARCTIC AIR INTO THE AREA WITH DRY AND COLD
WEATHER THROUGH EARLY NEXT WEEK. THE PACIFIC STORM TRACK IS EXPECTED
TO SHIFT NORTH TO OREGON BY MIDWEEK. WITH COLD AIR DEEPLY ENTRENCHED
OVER THE AREA...PRECIPITATION HAS THE POTENTIAL TO BEGIN AS A WINTERY
MIX AS IT RETURNS WEDNESDAY OR WEDNESDAY NIGHT.

&&

.SHORT TERM...NO CHANGES FOR THE EVENING UPDATE. SATELLITE IMAGERY
SHOWS A SURFACE FRONT MOVING SOUTHEASTWARD THROUGH THE FAR NORTHEAST
PAC OCEAN THIS EVENING...WITH THE UPPER LEVEL SUPPORT FOR THIS
FRONT MOVING INTO SOUTHERN BRITISH COLUMBIA. THIS SHORT WAVE WILL
EVENTUALLY DROP SOUTH OUT OF BRITISH COLUMBIA TO SOUTHERN WASHINGTON
BY FRI AFTERNOON...PUSHING THE COLD FRONT SOUTH THROUGH THE AREA AND
TURNING WINDS MORE NORTHERLY FOR COOLER TEMPERATURES. SHORTWAVE THEN
MOVES TO SOUTHERN OREGON BY SAT MORNING. PREVIOUS SHIFT HAD SOME
FLURRIES IN THE FORECAST FOR FRI NIGHT AS THIS SHORTWAVE MOVES
OVERHEAD. THIS WAS MAINLY IN THE CASCADES BUT ALSO HAD FLURRIES
MENTIONED IN THE FOOTHILLS AND IN THE WILLAMETTE VALLEY NORTH OF
SALEM. HAVE LEFT THIS IN THE FORECAST FOR THE EVENING UPDATE...BUT
NEWEST MODEL FIELDS AND BUFKIT SOUNDINGS SHOW NO PRECIP OF ANY KIND.
IN SPITE OF MODEL FIELDS WE COULD STILL SEE A FEW FLURRIES IN THE AIR
FRI NIGHT...ESPECIALLY IN THE CASCADES...BUT THAT WILL BE ABOUT
IT...A FEW FLURRIES WITH NO ACCUMULATIONS.

A SIGNIFICANTLY STRONGER SHORTWAVE TROUGH WILL DIG SOUTH ON SATURDAY
NIGHT AND SUNDAY BRINGING MUCH COLDER MODIFIED ARCTIC AIR INTO THE
PACIFIC NORTHWEST BEHIND IT. THE COLDEST AIR WILL ARRIVE IN EASTERN
WASHINGTON SUNDAY THEN FILTER SOUTH INTO OREGON SUNDAY NIGHT. WITH
THE EXTRA ENERGY ASSOCIATED WITH THIS SYSTEM A DUSTING OF SNOW IS A
BIT MORE LIKELY THAN WITH THE FRIDAY EVENING SHORTWAVE BUT LIMITED
MOISTURE WILL KEEP ANY ACCUMULATIONS MINIMAL. DRY AND VERY COLD
NORTHEAST TO EAST WINDS WILL REINTENSIFY SUNDAY AND MONDAY. 
DALTON/RUTHFORD

.LONG TERM...THE GFS AND ECMWF ARE IN AGREEMENT ON THE GENERAL 
PATTERN THROUGH MID NEXT WEEK WITH A WEAK RIDGE OVER THE AREA 
TUESDAY GIVING DRY AND VERY COLD WEATHER. THEN ON ABOUT WEDNESDAY 
THE SOUTHERN BRANCH OF THE JET...WHICH HAS BROKEN THROUGH UNDER THE 
OMEGA BLOCK LIFTS NORTH WITH PRECIPITATION SPREADING ACROSS THE 
FORECAST AREA FROM SOUTH TO NORTH. EASTERLY FLOW WILL LIKELY 
CONTINUE THE SUPPLY OF COLD LOW LEVEL AIR EVEN THOUGH WARMER AIR IS 
MOVING IN ALOFT. THIS COULD RESULT IN A VALLEY SNOW 
EVENT...ESPECIALLY NEAR THE GORGE. POSSIBLE FREEZING RAIN FOR THE 
GORGE LATER. SCHNEIDER/BROWN

&&

.AVIATION...VFR TONIGHT AND FRIDAY...EXCEPT FOR THE FAR SOUGH 
WILLAMETTE VALLEY WITH AREAS OF FOG LATER TONIGHT AND FRIDAY 
MORNING. IN FOG AREAS LOCAL 1/4 MILE VISIBILITY WITH FREEZING FOG. 
EAST WINDS THROUGH THE GORGE WILL WEAKEN OVER NIGHT.

KPDX AND APPROACHES...VFR NEXT 24 HOURS. SS

&&

.MARINE...WINDS WILL DECREASE TONIGHT AS GRADIENTS DECREASE. WINDS 
PICK UP FROM THE NORTH DURING THE DAY FRIDAY AS A COLD FRONT DROPS 
THROUGH...WITH GUSTS CLOSE TO 30 KT NOT OUT OF THE QUESTION. THESE 
WINDS CONTINUE INTO SAT. ALL THE MODELS SHOW AN ARCTIC FRONT COMING 
IN FROM THE NORTHEAST SATURDAY NIGHT AND SUNDAY...AND IF THEY ARE 
RIGHT...WINDS COULD GET CLOSE TO GALE FORCE. SEAS 10 TO 11 FEET WILL 
CONTINUE INTO FRIDAY.

&&

.PQR WATCHES/WARNINGS/ADVISORIES...
OR...NONE.
WA...NONE.
PZ...SMALL CRAFT ADVISORY FOR ROUGH COLUMBIA BAR AROUND EBBS THROUGH
      FRI.
     SMALL CRAFT ADVISORY FOR WINDS CAPE SHOALWATER TO FLORENCE
      OUT 10-60 NM FRI AFTERNOON THROUGH FRI NIGHT. 
     SMALL CRAFT ADVISORY FOR HAZARDOUS SEAS CAPE SHOALWATER TO
      FLORENCE OUT 10 NM FOR HAZARDOUS SEAS THIS EVENING THROUGH AND
      FRI MORNING.
     SMALL CRAFT ADVISORY FOR HAZARDOUS SEAS CAPE SHOALWATER TO
      FLORENCE 10-60 NM TONIGHT AND 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.