753 
FXUS66 KPQR 161120
AFDPQR

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE PORTLAND OR
300 AM PST THU DEC 16 2010

.SYNOPSIS...WEAK RIDGING ALOFT DEVELOPING OFFSHORE BEHIND TROUGH OF
LOW PRESSURE MOVING OVER THE PACNW. THE RIDGE OF HIGH PRES WILL MOVE
SLOWLY ACROSS THE REGION THURSDAY. THIS SHOULD CONFINE PRECIPITATION
TO THE COAST ON THU. AN OFFSHORE SURFACE FLOW WILL DEVELOP THU AND 
CONTINUE INTO EARLY SAT AS HIGH PRES DEVELOPS E OF THE CASCADES. A 
DEEP UPPER LEVEL LOW PRESSURE SYSTEM WILL FORM OVER THE E PACIFIC 
AT...SENDING THE FIRST IN A SERIES OF TROUGHS ACROSS THE REGION FRI 
NIGHT AND SAT.

&&

.SHORT TERM...MAIN CHANGES DURING THIS FORECAST PERIOD WAS TO BACK 
OFF ON POPS...ESPECIALLY IN THE VALLEY...AND POINTS NORTH AND EAST 
THU NIGHT AND THROUGH THE DAY FRI. WE ALSO ADDED SLIGHT CHC OF 
T-STORMS FOR THE COASTAL WATERS AND ADJACENT COASTAL AREAS SAT INTO 
SUN. FOCUS THEN WILL TURN TO THE STRONGER SYSTEM MOVING IN FRI NIGHT 
INTO SATURDAY WITH MOUNTAIN SNOW...GORGE AND UPPER HOOD RIVER VALLEY 
SNOW...AND ALSO ACCUMULATING SNOW IN THE COAST RANGE. HAVE KEPT A 
WET SNOW MENTION FOR THE N VALLEY FOR NOW. 

UPPER LEVEL RIDGE AXIS...WHICH WAS CENTERED OVER THE CWA THIS
MORNING...IS SLOWLY SHIFTING OFF TO THE EAST. THE RIDGE IS ALLOWING
FOR CLEAR SKIES SOUTH...WHILE CLOUDY CONDITIONS RULE THE NORTH. THE
BIG WEATHER MAKER REALLY LIES WELL OFFSHORE...AN UPPER LEVEL LOW IN
THE VICINITY OF 50N 149W. THIS FEATURE WILL CONTINUE TO SPREAD PIECES
OF ENERGY TOWARD THE PAC NW. THE FIRST WEAK AREA IS OFFSHORE NEAR
130W. ALOT OF SHOWERS IN THIS AREA...BUT  EXPECT THESE SHOWERS TO BE
JUST A LIMITED THREAT OF MOVING INLAND THOUGH LATER TONIGHT AND THU
DUE TO THE SLOWLY MOVING...AMPLIFYING...UPPER LEVEL RIDGE... AND A
DEVELOPING OFFSHORE FLOW AT THE SURFACE.  INITIAL SHORTWAVES PUSHING
IN FROM THE DEEPENING UPPER LOW OFFSHORE THU NIGHT AND FRI SIMILARLY
SHOULD BE OF LIMITED THREAT FOR  PRECIPITATION INLAND AS THE
SHORTWAVES WILL BE PUSHING INTO THE SLOWLY RETREATING UPPER RIDGE AND
DRY OFFSHORE SURFACE FLOW. MODELS HAVE BACKED OFF ON QPF AND RH
INLAND ON FRI...AND POPS HAVE BEEN TWEAKED DOWN ACCORDINGLY...AND MAY
LIKELY STILL BE TOO HIGH IN THE 6Z-12Z TIME PERIOD...BUT KEPT A SMALL
POP IN AT THE TIME OF THIS AFD...THEN KEPT MOST AREAS AWAY FROM THE
COAST/COAST RANGE DRY FOR THE REST OF THE DAY FRIDAY.  LATEST 6Z
FURTHER BACKS OFF ON PRECIP CHANCES IN THE VALLEY...SO EXPECT A DRY 
DAY FRIDAY FOR MOST LOCATIONS EXCEPT IN THE SOUTH AS PRECIP SPREADS 
NORTH. 

MAIN FOCUS FOR THE SHORT TERM THEN SHIFTS TO A STRONGER SHORTWAVE 
PUSHING IN LATE FRI NIGHT AND SAT. THE MAIN VORT MAX APPEARS TO 
SPLIT OFF TO THE NE SAT OFFSHORE...SO THE STRENGTH OF THE SYSTEM 
EXPECTED TO BE ON THE WEAK SIDE...ALTHOUGH DECENT MOISTURE 
ASSOCIATED WITH THE SYSTEM AND THE LOW LEVEL FLOW EVENTUALLY TURNING 
BACK ONSHORE SAT SUGGESTS RELATIVELY HIGH POPS ARE IN ORDER FROM 
LATE FRI NIGHT THROUGH SAT. THE LOW LEVEL OFFSHORE FLOW SUGGESTS 
USING CONTINENTAL RULES OF THUMB FOR FINDING A RAIN SNOW LINE. FAVOR 
USING THE NAM FOR THERMAL PROFILES WITH THE OFFSHORE FLOW...AND 
THESE SUPPORT A SNOW EVENT IN THE GORGE LATE FRI NIGHT AND THROUGH
MUCH OF SAT BEFORE THE OFFSHORE FLOW CEASES. IN THE ADJOINING N 
WILLAMETTE VALLEY THERMAL PROFILE OF WET BULB TEMPS IS GENERALLY 
NEAR TO A LITTLE ABOVE FREEZING LATE FRI NIGHT AND SAT MORNING BELOW 
850 MB. AS THE DEPICTED DEPTH OF THE NEAR FREEZING TEMPS IS FAIRLY 
DEEP...ODDS SEEM TO FAVOR A RAIN EVENT FOR MOST OF THE N VALLEY... 
BUT CANNOT RULE OUT SOME WET SNOW AT THIS POINT EITHER.  

REGRADING THE GORGE AND THE MOUNTAINS...STARTING TO GET SNOW TOTALS
INTO THE ADVISORY LEVEL AT THIS TIME THROUGH THE
MOUNTAINS...ESPECIALLY IN THE LANE COUNTY CASCADES WHERE BEST
OROGRAPHICS AND SHORTER DURATION OF OFFSHORE FLOW WILL ALLOW FOR
HIGHER ACCUMS...BUT STILL BEYOND THE 4TH PERIOD...SO NO HEADLINES
NEEDED YET. WE WILL NEED TO WATCH THE GORGE AND AREAS EAST...WITH
SNOW TOTALS EASILY INTO THE ADVISORY LEVEL SATURDAY NEAR HOOD RIVER
AND OTHER LOCALES IN THE VICINITY...APPROACHING WARNING LEVELS IF YOU
BELIEVE THE 0Z/6Z NAM BUFR/COBB OUTPUT PARAMETERS. 

A NOTE ABOUT WINDS...CROSS SECTIONS INDICATING A DECENT OFFSHORE 
WIND EVENT FOR THE GORGE...WITH SOME GUSTS GETTING INTO THE VALLEY 
WITH ENOUGH COLD AIR EAST OF THE BASIN DEEP ENOUGH FOR DOWNSLOPE 
FLOW. THIS WILL BRING GUSTS INTO THE VALLEY SAT MORNING...WHICH MAY 
ALSO MITIGATE THE CHANCE OF WET SNOW WITH ANY DOWNSLOPE 
WARMING...THOUGH STILL A BIT TO BE IRONED OUT WITH THE THERMAL 
PROFILES AT THIS TIME. KMD

.LONG TERM...MODELS IN AGREEMENT KEEPING STRONG UPPER LOW OVER THE 
NE PACIFIC THROUGH EARLY NEXT WEEK. MANY COLD FRONTS WILL MOVE 
ONSHORE IN OREGON AND WASHINGTON...KEEPING THE AREA UNDER A 
PARTICULARLY ACTIVE WET PATTERN THROUGH THE PERIOD. DETAILS ON 
SPECIFIC SYSTEMS ARE NOT AGREED UPON BY THE VARIOUS MODELS SO HAVE 
KEPT A GENERALLY WET FORECAST IN THROUGH EARLY NEXT WEEK. BROWN 
&&

.AVIATION...MOSTLY VFR CONDITIONS ACROSS THE REGION TODAY BUT
STILL A THREAT OF MVFR CEILINGS IN SHOWERS THIS MORNING ESPECIALLY
NEAR THE COAST. LIGHT WINDS AND WEAK SUBSIDENCE SOUTHERN INLAND
VALLEYS BRING A STRONG LIKELIHOOD FOR AREAS OF FOG DEVELOPMENT
THROUGH 19Z.

KPDX AND APPROACHES...MOSTLY VFR CONDITIONS TODAY BUT MODERATE
CONFIDENCE OF TEMPORARY MVFR CLOUD DECK 13Z-18Z. 

&&

.MARINE...SEAS SHOULD DROP A BIT BELOW 10 FT TODAY THEN HOVER IN A
9 TO 10 FT RANGE THROUGH FRI. WINDS WILL BE RISING BACK ABOVE
ADVISORY CRITERIA TODAY AS THE NEXT FRONT SLOWLY APPROACHES THE
WATERS. THIS FRONT FINALLY MOVES THROUGH THE AREA SAT MORNING
WITH SOME GALES POSSIBLE FRI NIGHT.

&&

.PQR WATCHES/WARNINGS/ADVISORIES...
OR...NONE.
WA...NONE.
PZ...SMALL CRAFT ADVISORY FOR WINDS FROM 10 AM THIS MORNING TO 4 PM 
     PST FRIDAY FOR COASTAL WATERS FROM CAPE SHOALWATER WA TO 
     CASCADE HEAD OR OUT TO 60 NM.

     SMALL CRAFT ADVISORY FOR HAZARDOUS SEAS UNTIL NOON PST TODAY
     FOR COASTAL WATERS FROM CAPE SHOALWATER WA TO FLORENCE OR OUT 
     TO 60 NM.

     SMALL CRAFT ADVISORY FOR WINDS FROM 6 PM THIS EVENING TO 4 PM 
     PST FRIDAY FOR COASTAL WATERS FROM CASCADE HEAD TO FLORENCE 
     OR OUT TO 60 NM.

     SMALL CRAFT ADVISORY FOR ROUGH COLUMBIA RIVER BAR UNTIL 3 PM 
     PST THIS 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.

999
FXUS66 KPQR 161120
AFDPQR

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE PORTLAND OR
300 AM PST THU DEC 16 2010

.SYNOPSIS...WEAK RIDGING ALOFT DEVELOPING OFFSHORE BEHIND TROUGH OF
LOW PRESSURE MOVING OVER THE PACNW. THE RIDGE OF HIGH PRES WILL MOVE
SLOWLY ACROSS THE REGION THURSDAY. THIS SHOULD CONFINE PRECIPITATION
TO THE COAST ON THU. AN OFFSHORE SURFACE FLOW WILL DEVELOP THU AND 
CONTINUE INTO EARLY SAT AS HIGH PRES DEVELOPS E OF THE CASCADES. A 
DEEP UPPER LEVEL LOW PRESSURE SYSTEM WILL FORM OVER THE E PACIFIC 
AT...SENDING THE FIRST IN A SERIES OF TROUGHS ACROSS THE REGION FRI 
NIGHT AND SAT.

&&

.SHORT TERM...MAIN CHANGES DURING THIS FORECAST PERIOD WAS TO BACK 
OFF ON POPS...ESPECIALLY IN THE VALLEY...AND POINTS NORTH AND EAST 
THU NIGHT AND THROUGH THE DAY FRI. WE ALSO ADDED SLIGHT CHC OF 
T-STORMS FOR THE COASTAL WATERS AND ADJACENT COASTAL AREAS SAT INTO 
SUN. FOCUS THEN WILL TURN TO THE STRONGER SYSTEM MOVING IN FRI NIGHT 
INTO SATURDAY WITH MOUNTAIN SNOW...GORGE AND UPPER HOOD RIVER VALLEY 
SNOW...AND ALSO ACCUMULATING SNOW IN THE COAST RANGE. HAVE KEPT A 
WET SNOW MENTION FOR THE N VALLEY FOR NOW. 

UPPER LEVEL RIDGE AXIS...WHICH WAS CENTERED OVER THE CWA THIS
MORNING...IS SLOWLY SHIFTING OFF TO THE EAST. THE RIDGE IS ALLOWING
FOR CLEAR SKIES SOUTH...WHILE CLOUDY CONDITIONS RULE THE NORTH. THE
BIG WEATHER MAKER REALLY LIES WELL OFFSHORE...AN UPPER LEVEL LOW IN
THE VICINITY OF 50N 149W. THIS FEATURE WILL CONTINUE TO SPREAD PIECES
OF ENERGY TOWARD THE PAC NW. THE FIRST WEAK AREA IS OFFSHORE NEAR
130W. ALOT OF SHOWERS IN THIS AREA...BUT  EXPECT THESE SHOWERS TO BE
JUST A LIMITED THREAT OF MOVING INLAND THOUGH LATER TONIGHT AND THU
DUE TO THE SLOWLY MOVING...AMPLIFYING...UPPER LEVEL RIDGE... AND A
DEVELOPING OFFSHORE FLOW AT THE SURFACE.  INITIAL SHORTWAVES PUSHING
IN FROM THE DEEPENING UPPER LOW OFFSHORE THU NIGHT AND FRI SIMILARLY
SHOULD BE OF LIMITED THREAT FOR  PRECIPITATION INLAND AS THE
SHORTWAVES WILL BE PUSHING INTO THE SLOWLY RETREATING UPPER RIDGE AND
DRY OFFSHORE SURFACE FLOW. MODELS HAVE BACKED OFF ON QPF AND RH
INLAND ON FRI...AND POPS HAVE BEEN TWEAKED DOWN ACCORDINGLY...AND MAY
LIKELY STILL BE TOO HIGH IN THE 6Z-12Z TIME PERIOD...BUT KEPT A SMALL
POP IN AT THE TIME OF THIS AFD...THEN KEPT MOST AREAS AWAY FROM THE
COAST/COAST RANGE DRY FOR THE REST OF THE DAY FRIDAY.  LATEST 6Z
FURTHER BACKS OFF ON PRECIP CHANCES IN THE VALLEY...SO EXPECT A DRY 
DAY FRIDAY FOR MOST LOCATIONS EXCEPT IN THE SOUTH AS PRECIP SPREADS 
NORTH. 

MAIN FOCUS FOR THE SHORT TERM THEN SHIFTS TO A STRONGER SHORTWAVE 
PUSHING IN LATE FRI NIGHT AND SAT. THE MAIN VORT MAX APPEARS TO 
SPLIT OFF TO THE NE SAT OFFSHORE...SO THE STRENGTH OF THE SYSTEM 
EXPECTED TO BE ON THE WEAK SIDE...ALTHOUGH DECENT MOISTURE 
ASSOCIATED WITH THE SYSTEM AND THE LOW LEVEL FLOW EVENTUALLY TURNING 
BACK ONSHORE SAT SUGGESTS RELATIVELY HIGH POPS ARE IN ORDER FROM 
LATE FRI NIGHT THROUGH SAT. THE LOW LEVEL OFFSHORE FLOW SUGGESTS 
USING CONTINENTAL RULES OF THUMB FOR FINDING A RAIN SNOW LINE. FAVOR 
USING THE NAM FOR THERMAL PROFILES WITH THE OFFSHORE FLOW...AND 
THESE SUPPORT A SNOW EVENT IN THE GORGE LATE FRI NIGHT AND THROUGH
MUCH OF SAT BEFORE THE OFFSHORE FLOW CEASES. IN THE ADJOINING N 
WILLAMETTE VALLEY THERMAL PROFILE OF WET BULB TEMPS IS GENERALLY 
NEAR TO A LITTLE ABOVE FREEZING LATE FRI NIGHT AND SAT MORNING BELOW 
850 MB. AS THE DEPICTED DEPTH OF THE NEAR FREEZING TEMPS IS FAIRLY 
DEEP...ODDS SEEM TO FAVOR A RAIN EVENT FOR MOST OF THE N VALLEY... 
BUT CANNOT RULE OUT SOME WET SNOW AT THIS POINT EITHER.  

REGRADING THE GORGE AND THE MOUNTAINS...STARTING TO GET SNOW TOTALS
INTO THE ADVISORY LEVEL AT THIS TIME THROUGH THE
MOUNTAINS...ESPECIALLY IN THE LANE COUNTY CASCADES WHERE BEST
OROGRAPHICS AND SHORTER DURATION OF OFFSHORE FLOW WILL ALLOW FOR
HIGHER ACCUMS...BUT STILL BEYOND THE 4TH PERIOD...SO NO HEADLINES
NEEDED YET. WE WILL NEED TO WATCH THE GORGE AND AREAS EAST...WITH
SNOW TOTALS EASILY INTO THE ADVISORY LEVEL SATURDAY NEAR HOOD RIVER
AND OTHER LOCALES IN THE VICINITY...APPROACHING WARNING LEVELS IF YOU
BELIEVE THE 0Z/6Z NAM BUFR/COBB OUTPUT PARAMETERS. 

A NOTE ABOUT WINDS...CROSS SECTIONS INDICATING A DECENT OFFSHORE 
WIND EVENT FOR THE GORGE...WITH SOME GUSTS GETTING INTO THE VALLEY 
WITH ENOUGH COLD AIR EAST OF THE BASIN DEEP ENOUGH FOR DOWNSLOPE 
FLOW. THIS WILL BRING GUSTS INTO THE VALLEY SAT MORNING...WHICH MAY 
ALSO MITIGATE THE CHANCE OF WET SNOW WITH ANY DOWNSLOPE 
WARMING...THOUGH STILL A BIT TO BE IRONED OUT WITH THE THERMAL 
PROFILES AT THIS TIME. KMD

.LONG TERM...MODELS IN AGREEMENT KEEPING STRONG UPPER LOW OVER THE 
NE PACIFIC THROUGH EARLY NEXT WEEK. MANY COLD FRONTS WILL MOVE 
ONSHORE IN OREGON AND WASHINGTON...KEEPING THE AREA UNDER A 
PARTICULARLY ACTIVE WET PATTERN THROUGH THE PERIOD. DETAILS ON 
SPECIFIC SYSTEMS ARE NOT AGREED UPON BY THE VARIOUS MODELS SO HAVE 
KEPT A GENERALLY WET FORECAST IN THROUGH EARLY NEXT WEEK. BROWN 
&&

.AVIATION...MOSTLY VFR CONDITIONS ACROSS THE REGION TODAY BUT
STILL A THREAT OF MVFR CEILINGS IN SHOWERS THIS MORNING ESPECIALLY
NEAR THE COAST. LIGHT WINDS AND WEAK SUBSIDENCE SOUTHERN INLAND
VALLEYS BRING A STRONG LIKELIHOOD FOR AREAS OF FOG DEVELOPMENT
THROUGH 19Z.

KPDX AND APPROACHES...MOSTLY VFR CONDITIONS TODAY BUT MODERATE
CONFIDENCE OF TEMPORARY MVFR CLOUD DECK 13Z-18Z. 

&&

.MARINE...SEAS SHOULD DROP A BIT BELOW 10 FT TODAY THEN HOVER IN A
9 TO 10 FT RANGE THROUGH FRI. WINDS WILL BE RISING BACK ABOVE
ADVISORY CRITERIA TODAY AS THE NEXT FRONT SLOWLY APPROACHES THE
WATERS. THIS FRONT FINALLY MOVES THROUGH THE AREA SAT MORNING
WITH SOME GALES POSSIBLE FRI NIGHT.

&&

.PQR WATCHES/WARNINGS/ADVISORIES...
OR...NONE.
WA...NONE.
PZ...SMALL CRAFT ADVISORY FOR WINDS FROM 10 AM THIS MORNING TO 4 PM 
     PST FRIDAY FOR COASTAL WATERS FROM CAPE SHOALWATER WA TO 
     CASCADE HEAD OR OUT TO 60 NM.

     SMALL CRAFT ADVISORY FOR HAZARDOUS SEAS UNTIL NOON PST TODAY
     FOR COASTAL WATERS FROM CAPE SHOALWATER WA TO FLORENCE OR OUT 
     TO 60 NM.

     SMALL CRAFT ADVISORY FOR WINDS FROM 6 PM THIS EVENING TO 4 PM 
     PST FRIDAY FOR COASTAL WATERS FROM CASCADE HEAD TO FLORENCE 
     OR OUT TO 60 NM.

     SMALL CRAFT ADVISORY FOR ROUGH COLUMBIA RIVER BAR UNTIL 3 PM 
     PST THIS 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.

750 
FXUS66 KPQR 161115
AFDPQR

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE PORTLAND OR
300 AM PST THU DEC 16 2010

.SYNOPSIS...WEAK RIDGING ALOFT DEVELOPING OFFSHORE BEHIND TROUGH OF
LOW PRESSURE MOVING OVER THE PACNW. THE RIDGE OF HIGH PRES WILL MOVE
SLOWLY ACROSS THE REGION THURSDAY. THIS SHOULD CONFINE PRECIPITATION
TO THE COAST ON THU. AN OFFSHORE SURFACE FLOW WILL DEVELOP THU AND 
CONTINUE INTO EARLY SAT AS HIGH PRES DEVELOPS E OF THE CASCADES. A 
DEEP UPPER LEVEL LOW PRESSURE SYSTEM WILL FORM OVER THE E PACIFIC 
AT...SENDING THE FIRST IN A SERIES OF TROUGHS ACROSS THE REGION FRI 
NIGHT AND SAT.

&&

.SHORT TERM...MAIN CHANGES DURING THIS FORECAST PERIOD WAS TO BACK 
OFF ON POPS...ESPECIALLY IN THE VALLEY...AND POINTS NORTH AND EAST 
THU NIGHT AND THROUGH THE DAY FRI. WE ALSO ADDED SLIGHT CHC OF 
T-STORMS FOR THE COASTAL WATERS AND ADJACENT COASTAL AREAS SAT INTO 
SUN. FOCUS THEN WILL TURN TO THE STRONGER SYSTEM MOVING IN FRI NIGHT 
INTO SATURDAY WITH MOUNTAIN SNOW...GORGE AND UPPER HOOD RIVER VALLEY 
SNOW...AND ALSO ACCUMULATING SNOW IN THE COAST RANGE. 

UPPER LEVEL RIDGE AXIS...WHICH WAS CENTERED OVER THE CWA THIS
MORNING...IS SLOWLY SHIFTING OFF TO THE EAST. THE RIDGE IS ALLOWING
FOR CLEAR SKIES SOUTH...WHILE CLOUDY CONDITIONS RULE THE NORTH. THE
BIG WEATHER MAKER REALLY LIES WELL OFFSHORE...AN UPPER LEVEL LOW IN
THE VICINITY OF 50N 149W. THIS FEATURE WILL CONTINUE TO SPREAD PIECES
OF ENERGY TOWARD THE PAC NW. THE FIRST WEAK AREA IS OFFSHORE NEAR
130W. ALOT OF SHOWERS IN THIS AREA...BUT  EXPECT THESE SHOWERS TO BE
JUST A LIMITED THREAT OF MOVING INLAND THOUGH LATER TONIGHT AND THU
DUE TO THE SLOWLY MOVING...AMPLIFYING...UPPER LEVEL RIDGE... AND A
DEVELOPING OFFSHORE FLOW AT THE SURFACE.  INITIAL SHORTWAVES PUSHING
IN FROM THE DEEPENING UPPER LOW OFFSHORE THU NIGHT AND FRI SIMILARLY
SHOULD BE OF LIMITED THREAT FOR  PRECIPITATION INLAND AS THE
SHORTWAVES WILL BE PUSHING INTO THE SLOWLY RETREATING UPPER RIDGE AND
DRY OFFSHORE SURFACE FLOW. MODELS HAVE BACKED OFF ON QPF AND RH
INLAND ON FRI...AND POPS HAVE BEEN TWEAKED DOWN ACCORDINGLY...AND MAY
LIKELY STILL BE TOO HIGH IN THE 6Z-12Z TIME PERIOD...BUT KEPT A SMALL
POP IN AT THE TIME OF THIS AFD...THEN KEPT MOST AREAS AWAY FROM THE
COAST/COAST RANGE DRY FOR THE REST OF THE DAY FRIDAY.  LATEST 6Z
FURTHER BACKS OFF ON PRECIP CHANCES IN THE VALLEY...SO EXPECT A DRY 
DAY FRIDAY FOR MOST LOCATIONS EXCEPT IN THE SOUTH AS PRECIP SPREADS 
NORTH. 

MAIN FOCUS FOR THE SHORT TERM THEN SHIFTS TO A STRONGER SHORTWAVE 
PUSHING IN LATE FRI NIGHT AND SAT. THE MAIN VORT MAX APPEARS TO 
SPLIT OFF TO THE NE SAT OFFSHORE...SO THE STRENGTH OF THE SYSTEM 
EXPECTED TO BE ON THE WEAK SIDE...ALTHOUGH DECENT MOISTURE 
ASSOCIATED WITH THE SYSTEM AND THE LOW LEVEL FLOW EVENTUALLY TURNING 
BACK ONSHORE SAT SUGGESTS RELATIVELY HIGH POPS ARE IN ORDER FROM 
LATE FRI NIGHT THROUGH SAT. THE LOW LEVEL OFFSHORE FLOW SUGGESTS 
USING CONTINENTAL RULES OF THUMB FOR FINDING A RAIN SNOW LINE. FAVOR 
USING THE NAM FOR THERMAL PROFILES WITH THE OFFSHORE FLOW...AND 
THESE SUPPORT A SNOW EVENT IN THE GORGE LATE FRI NIGHT AND THROUGH
MUCH OF SAT BEFORE THE OFFSHORE FLOW CEASES. IN THE ADJOINING N 
WILLAMETTE VALLEY THERMAL PROFILE OF WET BULB TEMPS IS GENERALLY 
NEAR TO A LITTLE ABOVE FREEZING LATE FRI NIGHT AND SAT MORNING BELOW 
850 MB. AS THE DEPICTED DEPTH OF THE NEAR FREEZING TEMPS IS FAIRLY 
DEEP...ODDS SEEM TO FAVOR A RAIN EVENT FOR MOST OF THE N VALLEY... 
BUT CANNOT RULE OUT SOME WET SNOW AT THIS POINT EITHER.  

REGRADING THE GORGE AND THE MOUNTAINS...STARTING TO GET SNOW TOTALS
INTO THE ADVISORY LEVEL AT THIS TIME THROUGH THE
MOUNTAINS...ESPECIALLY IN THE LANE COUNTY CASCADES WHERE BEST
OROGRAPHICS AND SHORTER DURATION OF OFFSHORE FLOW WILL ALLOW FOR
HIGHER ACCUMS...BUT STILL BEYOND THE 4TH PERIOD...SO NO HEADLINES
NEEDED YET. WE WILL NEED TO WATCH THE GORGE AND AREAS EAST...WITH
SNOW TOTALS EASILY INTO THE ADVISORY LEVEL SATURDAY NEAR HOOD RIVER
AND OTHER LOCALES IN THE VICINITY...APPROACHING WARNING LEVELS IF YOU
BELIEVE THE 0Z/6Z NAM BUFR/COBB OUTPUT PARAMETERS. KMD

.LONG TERM...MODELS IN AGREEMENT KEEPING STRONG UPPER LOW OVER THE 
NE PACIFIC THROUGH EARLY NEXT WEEK. MANY COLD FRONTS WILL MOVE 
ONSHORE IN OREGON AND WASHINGTON...KEEPING THE AREA UNDER A 
PARTICULARLY ACTIVE WET PATTERN THROUGH THE PERIOD. DETAILS ON 
SPECIFIC SYSTEMS ARE NOT AGREED UPON BY THE VARIOUS MODELS SO HAVE 
KEPT A GENERALLY WET FORECAST IN THROUGH EARLY NEXT WEEK. BROWN 
&&

.AVIATION...MOSTLY VFR CONDITIONS ACROSS THE REGION TODAY BUT
STILL A THREAT OF MVFR CEILINGS IN SHOWERS THIS MORNING ESPECIALLY
NEAR THE COAST. LIGHT WINDS AND WEAK SUBSIDENCE SOUTHERN INLAND
VALLEYS BRING A STRONG LIKELIHOOD FOR AREAS OF FOG DEVELOPMENT
THROUGH 19Z.

KPDX AND APPROACHES...MOSTLY VFR CONDITIONS TODAY BUT MODERATE
CONFIDENCE OF TEMPORARY MVFR CLOUD DECK 13Z-18Z. 

&&

.MARINE...SEAS SHOULD DROP A BIT BELOW 10 FT TODAY THEN HOVER IN A
9 TO 10 FT RANGE THROUGH FRI. WINDS WILL BE RISING BACK ABOVE
ADVISORY CRITERIA TODAY AS THE NEXT FRONT SLOWLY APPROACHES THE
WATERS. THIS FRONT FINALLY MOVES THROUGH THE AREA SAT MORNING
WITH SOME GALES POSSIBLE FRI NIGHT.

&&

.PQR WATCHES/WARNINGS/ADVISORIES...
OR...NONE.
WA...NONE.
PZ...SMALL CRAFT ADVISORY FOR WINDS FROM 10 AM THIS MORNING TO 4 PM 
     PST FRIDAY FOR COASTAL WATERS FROM CAPE SHOALWATER WA TO 
     CASCADE HEAD OR OUT TO 60 NM.

     SMALL CRAFT ADVISORY FOR HAZARDOUS SEAS UNTIL NOON PST TODAY
     FOR COASTAL WATERS FROM CAPE SHOALWATER WA TO FLORENCE OR OUT 
     TO 60 NM.

     SMALL CRAFT ADVISORY FOR WINDS FROM 6 PM THIS EVENING TO 4 PM 
     PST FRIDAY FOR COASTAL WATERS FROM CASCADE HEAD TO FLORENCE 
     OR OUT TO 60 NM.

     SMALL CRAFT ADVISORY FOR ROUGH COLUMBIA RIVER BAR UNTIL 3 PM 
     PST THIS 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.

999
FXUS66 KPQR 161115
AFDPQR

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE PORTLAND OR
300 AM PST THU DEC 16 2010

.SYNOPSIS...WEAK RIDGING ALOFT DEVELOPING OFFSHORE BEHIND TROUGH OF
LOW PRESSURE MOVING OVER THE PACNW. THE RIDGE OF HIGH PRES WILL MOVE
SLOWLY ACROSS THE REGION THURSDAY. THIS SHOULD CONFINE PRECIPITATION
TO THE COAST ON THU. AN OFFSHORE SURFACE FLOW WILL DEVELOP THU AND 
CONTINUE INTO EARLY SAT AS HIGH PRES DEVELOPS E OF THE CASCADES. A 
DEEP UPPER LEVEL LOW PRESSURE SYSTEM WILL FORM OVER THE E PACIFIC 
AT...SENDING THE FIRST IN A SERIES OF TROUGHS ACROSS THE REGION FRI 
NIGHT AND SAT.

&&

.SHORT TERM...MAIN CHANGES DURING THIS FORECAST PERIOD WAS TO BACK 
OFF ON POPS...ESPECIALLY IN THE VALLEY...AND POINTS NORTH AND EAST 
THU NIGHT AND THROUGH THE DAY FRI. WE ALSO ADDED SLIGHT CHC OF 
T-STORMS FOR THE COASTAL WATERS AND ADJACENT COASTAL AREAS SAT INTO 
SUN. FOCUS THEN WILL TURN TO THE STRONGER SYSTEM MOVING IN FRI NIGHT 
INTO SATURDAY WITH MOUNTAIN SNOW...GORGE AND UPPER HOOD RIVER VALLEY 
SNOW...AND ALSO ACCUMULATING SNOW IN THE COAST RANGE. 

UPPER LEVEL RIDGE AXIS...WHICH WAS CENTERED OVER THE CWA THIS
MORNING...IS SLOWLY SHIFTING OFF TO THE EAST. THE RIDGE IS ALLOWING
FOR CLEAR SKIES SOUTH...WHILE CLOUDY CONDITIONS RULE THE NORTH. THE
BIG WEATHER MAKER REALLY LIES WELL OFFSHORE...AN UPPER LEVEL LOW IN
THE VICINITY OF 50N 149W. THIS FEATURE WILL CONTINUE TO SPREAD PIECES
OF ENERGY TOWARD THE PAC NW. THE FIRST WEAK AREA IS OFFSHORE NEAR
130W. ALOT OF SHOWERS IN THIS AREA...BUT  EXPECT THESE SHOWERS TO BE
JUST A LIMITED THREAT OF MOVING INLAND THOUGH LATER TONIGHT AND THU
DUE TO THE SLOWLY MOVING...AMPLIFYING...UPPER LEVEL RIDGE... AND A
DEVELOPING OFFSHORE FLOW AT THE SURFACE.  INITIAL SHORTWAVES PUSHING
IN FROM THE DEEPENING UPPER LOW OFFSHORE THU NIGHT AND FRI SIMILARLY
SHOULD BE OF LIMITED THREAT FOR  PRECIPITATION INLAND AS THE
SHORTWAVES WILL BE PUSHING INTO THE SLOWLY RETREATING UPPER RIDGE AND
DRY OFFSHORE SURFACE FLOW. MODELS HAVE BACKED OFF ON QPF AND RH
INLAND ON FRI...AND POPS HAVE BEEN TWEAKED DOWN ACCORDINGLY...AND MAY
LIKELY STILL BE TOO HIGH IN THE 6Z-12Z TIME PERIOD...BUT KEPT A SMALL
POP IN AT THE TIME OF THIS AFD...THEN KEPT MOST AREAS AWAY FROM THE
COAST/COAST RANGE DRY FOR THE REST OF THE DAY FRIDAY.  LATEST 6Z
FURTHER BACKS OFF ON PRECIP CHANCES IN THE VALLEY...SO EXPECT A DRY 
DAY FRIDAY FOR MOST LOCATIONS EXCEPT IN THE SOUTH AS PRECIP SPREADS 
NORTH. 

MAIN FOCUS FOR THE SHORT TERM THEN SHIFTS TO A STRONGER SHORTWAVE 
PUSHING IN LATE FRI NIGHT AND SAT. THE MAIN VORT MAX APPEARS TO 
SPLIT OFF TO THE NE SAT OFFSHORE...SO THE STRENGTH OF THE SYSTEM 
EXPECTED TO BE ON THE WEAK SIDE...ALTHOUGH DECENT MOISTURE 
ASSOCIATED WITH THE SYSTEM AND THE LOW LEVEL FLOW EVENTUALLY TURNING 
BACK ONSHORE SAT SUGGESTS RELATIVELY HIGH POPS ARE IN ORDER FROM 
LATE FRI NIGHT THROUGH SAT. THE LOW LEVEL OFFSHORE FLOW SUGGESTS 
USING CONTINENTAL RULES OF THUMB FOR FINDING A RAIN SNOW LINE. FAVOR 
USING THE NAM FOR THERMAL PROFILES WITH THE OFFSHORE FLOW...AND 
THESE SUPPORT A SNOW EVENT IN THE GORGE LATE FRI NIGHT AND THROUGH
MUCH OF SAT BEFORE THE OFFSHORE FLOW CEASES. IN THE ADJOINING N 
WILLAMETTE VALLEY THERMAL PROFILE OF WET BULB TEMPS IS GENERALLY 
NEAR TO A LITTLE ABOVE FREEZING LATE FRI NIGHT AND SAT MORNING BELOW 
850 MB. AS THE DEPICTED DEPTH OF THE NEAR FREEZING TEMPS IS FAIRLY 
DEEP...ODDS SEEM TO FAVOR A RAIN EVENT FOR MOST OF THE N VALLEY... 
BUT CANNOT RULE OUT SOME WET SNOW AT THIS POINT EITHER.  

REGRADING THE GORGE AND THE MOUNTAINS...STARTING TO GET SNOW TOTALS
INTO THE ADVISORY LEVEL AT THIS TIME THROUGH THE
MOUNTAINS...ESPECIALLY IN THE LANE COUNTY CASCADES WHERE BEST
OROGRAPHICS AND SHORTER DURATION OF OFFSHORE FLOW WILL ALLOW FOR
HIGHER ACCUMS...BUT STILL BEYOND THE 4TH PERIOD...SO NO HEADLINES
NEEDED YET. WE WILL NEED TO WATCH THE GORGE AND AREAS EAST...WITH
SNOW TOTALS EASILY INTO THE ADVISORY LEVEL SATURDAY NEAR HOOD RIVER
AND OTHER LOCALES IN THE VICINITY...APPROACHING WARNING LEVELS IF YOU
BELIEVE THE 0Z/6Z NAM BUFR/COBB OUTPUT PARAMETERS. KMD

.LONG TERM...MODELS IN AGREEMENT KEEPING STRONG UPPER LOW OVER THE 
NE PACIFIC THROUGH EARLY NEXT WEEK. MANY COLD FRONTS WILL MOVE 
ONSHORE IN OREGON AND WASHINGTON...KEEPING THE AREA UNDER A 
PARTICULARLY ACTIVE WET PATTERN THROUGH THE PERIOD. DETAILS ON 
SPECIFIC SYSTEMS ARE NOT AGREED UPON BY THE VARIOUS MODELS SO HAVE 
KEPT A GENERALLY WET FORECAST IN THROUGH EARLY NEXT WEEK. BROWN 
&&

.AVIATION...MOSTLY VFR CONDITIONS ACROSS THE REGION TODAY BUT
STILL A THREAT OF MVFR CEILINGS IN SHOWERS THIS MORNING ESPECIALLY
NEAR THE COAST. LIGHT WINDS AND WEAK SUBSIDENCE SOUTHERN INLAND
VALLEYS BRING A STRONG LIKELIHOOD FOR AREAS OF FOG DEVELOPMENT
THROUGH 19Z.

KPDX AND APPROACHES...MOSTLY VFR CONDITIONS TODAY BUT MODERATE
CONFIDENCE OF TEMPORARY MVFR CLOUD DECK 13Z-18Z. 

&&

.MARINE...SEAS SHOULD DROP A BIT BELOW 10 FT TODAY THEN HOVER IN A
9 TO 10 FT RANGE THROUGH FRI. WINDS WILL BE RISING BACK ABOVE
ADVISORY CRITERIA TODAY AS THE NEXT FRONT SLOWLY APPROACHES THE
WATERS. THIS FRONT FINALLY MOVES THROUGH THE AREA SAT MORNING
WITH SOME GALES POSSIBLE FRI NIGHT.

&&

.PQR WATCHES/WARNINGS/ADVISORIES...
OR...NONE.
WA...NONE.
PZ...SMALL CRAFT ADVISORY FOR WINDS FROM 10 AM THIS MORNING TO 4 PM 
     PST FRIDAY FOR COASTAL WATERS FROM CAPE SHOALWATER WA TO 
     CASCADE HEAD OR OUT TO 60 NM.

     SMALL CRAFT ADVISORY FOR HAZARDOUS SEAS UNTIL NOON PST TODAY
     FOR COASTAL WATERS FROM CAPE SHOALWATER WA TO FLORENCE OR OUT 
     TO 60 NM.

     SMALL CRAFT ADVISORY FOR WINDS FROM 6 PM THIS EVENING TO 4 PM 
     PST FRIDAY FOR COASTAL WATERS FROM CASCADE HEAD TO FLORENCE 
     OR OUT TO 60 NM.

     SMALL CRAFT ADVISORY FOR ROUGH COLUMBIA RIVER BAR UNTIL 3 PM 
     PST THIS 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.