FXUS66 KPQR 042256
AFDPQR

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE PORTLAND OR
255 PM PST FRI DEC  4 2009

.SYNOPSIS...AN UPPER TROUGH DROPPING DOWN FROM BRITISH COLUMBIA WILL
SLIDE SOUTH INTO THE PACIFIC NORTHWEST TODAY. ANY MOISTURE WITH THIS
SYSTEM WILL BE QUITE SPARSE BUT COULD FALL IN THE FORM OF A FEW SNOW
FLURRIES NEAR THE MOUNTAINS TONIGHT. A SECOND STRONGER SYSTEM
DROPPING SOUTH ON SUNDAY WILL BRING COLDER ARCTIC AIR AND INCREASING
NORTHEASTERLY WIND INTO THE AREA SUNDAY AND SUNDAY NIGHT. ISOLATED
SNOW SHOWERS ARE POSSIBLE AS WELL BUT ANY ACCUMULATIONS ARE EXPECTED
TO BE MINIMAL. COLD WEATHER WILL LIKELY PERSIST THROUGH EARLY NEXT
WEEK. 

&&

.SHORT TERM...2 TO 3 MB OF ONSHORE FLOW WILL DIMINISH QUICKLY THIS
EVENING AS WINDS WILL SHIFT MORE NORTHERLY THEN TURN TO THE NORTHEAST
BY SATURDAY MORNING AS A COOLER MODIFIED ARCTIC AIR MASS
FILTERS INTO EASTERN WASHINGTON AND OREGON.  WEST OF THE MOUNTAINS
TEMPERATURE DROPS WILL BE MORE SUBTLE BUT SLOWLY TREND DOWNWARD
TONIGHT THROUGH SATURDAY NIGHT.  THE COAST WILL BE THE EXCEPT TO THIS
DURING THE DAY SATURDAY WITH AN INVERTED SURFACE TROUGH ALONG THE
COAST AND OFFSHORE DOWNSLOPE FLOW WARMING TEMPERATURES TO THE UPPER
40S TO AROUND 50 AT THE BEACHES...FURTHER INLAND HIGH TEMPERATURES
WILL DO WELL TO BREAK 40 AT THE LOWER ELEVATIONS AND REMAIN IN THE
20S AND 30S IN THE MOUNTAINS.

THE MORE IMPRESSIVELY COLD ARCTIC AIR MASS WILL ARRIVE ON SUNDAY WITH
A DEEPER UPPER LEVEL LOW DIGGING SOUTH OVER OREGON.  MODELS SUGGEST A
BRIEF OVERWATER TRAJECTORY FOR THE COLD AIR AND SHOW THE UPPER LOW
PARTIALLY CUTTING OFF. GIVEN THESE FACTORS AND THE STRENGTH OF THE
UPPER LOW...ISOLATED TO SCATTERED SNOW SHOWERS ARE A POSSIBILITY ON
SUNDAY.  AT THE MOMENT MOISTURE LOOKS TO BE THE LIMITING FACTOR WHICH
SHOULD KEEP ANY SNOW ACCUMULATIONS MINIMAL.  MY ONE CONCERN ABOUT
THIS ASSUMPTION HOWEVER WOULD BE IF EXTRA FRONTAL DEVELOPMENT OCCURS
ALONG THE ARCTIC FRONT JUST OFFSHORE FUELED BY THE CONTRAST BETWEEN
THE VERY COLD AIR MASS AND THE WARMER MARINE AIR TO TE SOUTH. THE
DEGREE TO WHICH THE UPPER LOW STARTS TO CUT OFF COULD ALSO SUPPORT
THIS WITH THE ARCTIC FRONT STALLING 100 OR 150 MILES FURTHER NORTH
WHICH WOULD PUT IT OVER OUR CWA.

INCREASING NORTH WINDS ON SUNDAY SHIFTING TO THE NORTHEAST SUNDAY
NIGHT WILL BE QUITE CHILLY AS THEY COINCIDE WITH TEMPERATURES IN THE
TEENS. EAST WINDS WILL LIKELY PERSIST IN THE WESTERN GORGE THROUGH
MIDWEEK. THE STRONG EAST WINDS COMBINED WITH TEMPERATURES WELL BELOW
FREEZING WILL MAKE FREEZING SPRAY A DEFINITE CONCERN FOR GORGE
MARINERS. RUTHFORD

.LONG TERM...BELOW NORMAL TEMPERATURES SHOULD CONTINUE INTO MID WEEK 
AS A DEEP ARCTIC TROUGH MOVES OFF TO THE EAST. QUESTIONS REMAIN IN 
THE LONG TERM REGARDING THE NEXT SYSTEM TO AFFECT THE AREA. THE 
TRACK OF THE LOW WILL DETERMINE THE AMOUNT OF PRECIPITATION OVER THE 
AREA. THE GFS TAKES THE LOW FURTHER SOUTH INTO CALIFORNIA WHILE THE 
ECMWF BRINGS THE LOW INTO SOUTHERN OREGON. FOR NOW WENT WITH A BLEND 
OF CONSISTENCY WITH THE LATEST RUN OF THE WETTER ECMWF. WITH THE 
COLD AIR IN PLACE...THE POSSIBILITY REMAINS OF SEEING A WINTERY MIX 
OF PRECIPITATION OVER THE FORECAST AREA AS THIS SYSTEM MOVES THROUGH 
LATE NEXT WEEK. BROWN

&&

.AVIATION...ONSHORE FLOW CONTINUES THIS AFTERNOON. A SCATTERED TO 
BROKEN VFR STRATUS DECK ON THE COAST AND NORTH INLAND WILL SLOWLY 
DISSIPATE. HOWEVER TONIGHT AS COLDER NORTHERLY FLOW DEVELOP MAINLY 
VFR CIGS WILL RETURN.  THE KEUG AREA WILL LIKELY RETURN TO FREEZING 
FOG LATER TONIGHT BUT BREAK UP EARLIER SATURDAY MORNING AS NORTHERLY 
FLOW INCREASES.

KPDX AND APPROACHES...CURRENT VFR CIGS WILL LIKELY CONTINUE TO THIN 
THROUGH THE EVENING...THEN THE NEXT BATCH OF MAINLY VFR CIGS ARRIVE 
LATER IN THE EVENING AROUND 06Z. 

&&

.MARINE...SMALL CRAFT WINDS ACROSS THE NORTHERN OUTER WATERS THIS 
AFTERNOON AND IS EXPECTED TO SPREAD TO THE SOUTH. WINDS SHOULD EASE 
IN THE NORTH IN THE EVENING BUT CONTINUE THROUGH SAT IN THE SOUTH. 
10 TO 12 FOOT SEAS RUNNING NORTH TO SOUTH ACROSS THE OUTER WATER 
THIS EVENING.  AN ARCTIC FRONT WILL SWEEP IN FROM THE NORTHEAST 
SUNDAY AND SHOULD SEE SOLID SMALL CRAFT WINDS THEN...WHICH LOOK TO 
LAST INTO MONDAY. SEAS HAVE DROPPED BELOW 10 FT EARLY THIS 
MORNING...BUT SHOULD RISE TO NEAR 10 FT IN THE OUTER WATERS MAINLY 
THIS AFTERNOON AND EVENING. WILL NEED TO WATCH IF SEAS WILL APPROACH 
10 FT SUNDAY AND MONDAY BUT FOR NOW IT MAY STAY JUST BELOW. 

&&

.PQR WATCHES/WARNINGS/ADVISORIES...
OR...NONE.
WA...NONE.
PZ...SMALL CRAFT ADVISORY FOR ROUGH COLUMBIA BAR AROUND EBB
      LATE THIS AFTERNOON.
     SMALL CRAFT ADVISORY FOR WINDS CAPE SHOALWATER TO
      CASCADE HEAD 10 TO 60 NM OFFSHORE THROUGH ABOUT MIDNIGHT.
     SMALL CRAFT ADVISORY FOR WINDS CASCADE HEAD TO FLORENCE 
      THROUGH SAT.
     SMALL CRAFT ADVISORY FOR WINDS CAPE SHOALWATER TO FLORENCE
      OUT 10 NM THIS AFTERNOON AND EVENING.
     SMALL CRAFT ADVISORY FOR HAZARDOUS SEAS CAPE SHOALWATER
      TO FLORENCE 10 TO 60 NM OFFSHORE THROUGH THIS EVENING.

&&

$$

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.