FXUS66 KPQR 051049
AFDPQR

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE PORTLAND OR
248 AM PST SAT DEC  5 2009

.SYNOPSIS...A COLD UPPER TROUGH WILL DROP SOUTH THROUGH THE PACIFIC
NORTHWEST TONIGHT AND SUNDAY...BRINGING COLDER ARCTIC AIR AND
INCREASING NORTHEAST WINDS 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 THE
FIRST PART OF NEXT WEEK. 

&&

.SHORT TERM...WEAK ONSHORE FLOW FRI MOISTENED THE LOW LEVEL AIR MASS
WHICH IS ALLOWING PATCHY TO AREAS OF FREEZING FOG TO FORM OVERNIGHT.
ONE UPPER TROUGH WILL DROP THROUGH MAINLY EASTERN OREGON THIS MORNING
BUT WILL TURN GRADIENTS WEAKLY OFFSHORE AGAIN. THIS SHOULD HELP TO
CLEAR OUT THE FREEZING FOG BY LATE MORNING...BUT WITH A COLD START
EXPECT VALLEY MAXIMUMS TO ONLY RISE TO AROUND 40 TODAY. THE COAST 
WILL BE WARMER WITH SOME OFFSHORE DOWNSLOPE FLOW WARMING TEMPS TO
NEAR 50 SOUTHERN AREAS. 

THE MORE IMPRESSIVE COLD ARCTIC AIR MASS WILL ARRIVE ON SUN WITH A
DEEPER UPPER LEVEL LOW DIGGING S THROUGH THE PAC NW...THEN DOWN INTO
NORTHERN CA SUN NIGHT. 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 SNOW
SHOWERS ARE A POSSIBILITY ON SUN. HOWEVER MODELS CONTINUE TO LIMIT
THE AVAILABLE MOISTURE WHICH SHOULD KEEP ANY SNOW ACCUMULATIONS
MINIMAL. INCREASING NE WINDS ON SUN WILL BE QUITE CHILLY AS THEY
COINCIDE WITH TEMPERATURES IN THE TEENS AND 20S. THE HIGHER
RESOLUTION NAM12 AND WRKGFS SHOW THE STRONGEST E WINDS FROM SUN
MORNING INTO MON MORNING...ALTHOUGH W WINDS WILL LIKELY PERSIST IN
THE WESTERN GORGE THROUGH MIDWEEK. NAM12 CROSS SECTIONS NEAR THE
GORGE SHOW 40-50 KT WINDS DESCENDING FROM 900-950MB...SUGGESTING A
WIND ADVISORY MAY BE NEEDED IN THE PORTLAND/VANCOUVER METRO AREA
DURING THE WINDIER PERIOD. RW

.LONG TERM...NO CHANGES. PREVIOUS DISCUSSION FOLLOWS...
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...PREDOMINANT VFR CONDITIONS THIS MORNING. HOWEVER... 
PATCHY FREEZING FOG AND LOW STRATUS WILL CONTINUE TO PLAGUE AREAS 
NEAR THE COLUMBIA RIVER GORGE UNTIL 12Z-14Z AS WELL AS THE SOUTH 
WILLAMETTE VALLEY UNTIL 16Z. DRIER OFFSHORE FLOW WILL DEVELOP NEAR 
THE GORGE BY 14Z AND THEN FAN OUT ACROSS THE REST OF THE FORECAST 
AREA THROUGH THE DAY.

KPDX AND APPROACHES...A MIX OF IFR AND MVFR CEILINGS ARE EXPECTED 
THROUGH 14Z. OFFSHORE FLOW WILL DEVELOP JUST ABOVE THE SURFACE AFTER 
14Z WHICH WILL HELP BREAK UP THE LOW LEVEL MOISTURE AND RETURN THE 
TERMINAL TO VFR CONDITIONS. SS

&&

.MARINE...SEAS AROUND 10 FT EARLY THIS MORNING WILL DROP BELOW 10 FT 
BY MIDDAY. SEAS MAY NEAR 10 FT AGAIN SUNDAY AND MONDAY AS OFFSHORE 
FLOW INCREASES. MARGINAL SMALL CRAFT WINDS ARE EXPECTED AT TIMES 
THROUGH THE WEEKEND...ESPECIALLY SUNDAY AND MONDAY AS ARCTIC AIR 
MOVES ACROSS THE WATERS INCREASING THE OFFSHORE FLOW.

&&

.PQR WATCHES/WARNINGS/ADVISORIES...
OR/WA...SMALL CRAFT ADVISORY FOR WINDS CAPE SHOALWATER TO FLORENCE
  10 TO 60 NM OFFSHORE THROUGH THIS EVENING.
SMALL CRAFT ADVISORY FOR HAZARDOUS SEAS CAPE SHOALWATER TO  
  FLORENCE OUT 60 NM THROUGH 10 AM THIS MORNING.

&&

$$

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.