Area Forecast Discussion
Issued by NWS Portland, OR

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FXUS66 KPQR 271028
AFDPQR

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE PORTLAND OR
230 AM PST TUE JAN 27 2015

.SYNOPSIS...A WEAK FRONTAL SYSTEM WILL MOVE ONTO THE S WA AND N
OREGON COAST THIS MORNING...AND SPREAD INLAND OVER THE N PART OF THE
FORECAST AREA LATER TODAY BEFORE STALLING TONIGHT. THE FRONT WILL
LINGER THROUGH WED AS IT FURTHER DECAYS. ANOTHER UPPER RIDGE IS
EXPECTED TO DEVELOP OVER THE PACIFIC NORTHWEST LATER IN THE WEEK AND
CONTINUE INTO THE WEEKEND. THE NEXT CHANCE FOR RAIN IS PROBABLY NOT
UNTIL LATER IN THE WEEKEND OR EARLY NEXT WEEK.
&&

.SHORT TERM...SURFACE OBSERVATIONS INDICATED FOG WAS STILL
WIDESPREAD OVER THE SOUTHERN HALF OF THE WILLAMETTE VALLEY EARLY
THIS MORNING...AND LOCALLY DENSE. THE WEAK FRONT THAT WAS MOVING
ONTO THE WA COAST EXTENDED OFFSHORE TO THE SW. MODELS HAVE THIS
FRONT SAGGING SE INTO NW OREGON TODAY...AND STALLING OVER SW WA AND
EXTREME NW OREGON TONIGHT. THE FRONT WILL TURN THE LOW LEVEL FLOW
WEAKLY ONSHORE TODAY FROM THE SW...PUSHING MARINE MOISTURE INLAND.
AS THE SHALLOW INVERSION IS REPLACED BY A LITTLE DEEPER MARINE AIR
MASS EXPECT TO SEE FOG LIFT THIS AFTERNOON...AND END THE THREAT OF
DENSE FOG FOR THE TIME BEING. A NARROW BAND OF DEEPER MOISTURE WILL
ACCOMPANY THE FRONT AS IT MOVES INLAND LATER TODAY AND
TONIGHT...WITH GFS PRECIPITABLE WATER PROGS INDICATING VALUES
BETWEEN EIGHT AND NINE TENTHS OF AN INCH. 00Z MODEL RUNS HAVE THIS
BAND OF DEEPER MOISTURE SINKING JUST A LITTLE FURTHER SE INTO NW
OREGON THAN YESTERDAYS MODEL RUNS...BUT OVERALL CONSISTENCY IN
MODELS IN DEPICTING WHERE THE BAROCLINIC ZONE WINDS UP REMAINS GOOD.
WITH AMPLE MOISTURE AND WEAK LIFT...WILL UP THE POPS A BIT MORE IN
THE NARROW ZONE OF MOST LIKELY PRECPITATION LATER TODAY THROUGH WED
MORNING...FROM THE S WA CASCADES SW THROUGH THE LOWER COLUMBIA
VALLEY AND OFF THE N OREGON COAST. WITH A CONSIDERABLY WEAKENED
RIDGE ALOFT AND LOW LEVEL ONSHORE FLOW EXPECT TO SEE A MUCH MORE
NORMAL LOOKING THERMAL PROFILE OVER THE NEXT FEW DAYS...BUT STILL A
FEW DEGREES WARMER THAN NORMAL.

LATE WED INTO THU MODELS SLOWLY DRY OUT THE BAROCLINIC ZONE AS A
SURFACE RIDGE EXTENDS DOWN THROUGH EASTERN WA AND ID...TURNING THE
LOW LEVEL FLOW OFFSHORE AGAIN. THIS WILL BRING AN END TO THE THREAT
OF SHOWERS BY WED NIGHT.

.LONG TERM...NO CHANGES. PREVIOUS DISCUSSION FOLLOWS. THURSDAY NIGHT
THROUGH MONDAY... FCST CONFIDENCE IS HIGH THAT AN UPPER LEVEL RIDGE
OVER THE NE PAC WILL STRENGTHEN AND BEGIN TO BUILD INTO THE PAC NW
STARTING THU NIGHT AND FRI. THE RIDGE AXIS IS EXPECTED TO MOVE
ONSHORE AND DIRECTLY OVERHEAD LATE FRI AND SAT. THIS SHOULD MEAN A
RETURN TO DRY WEATHER FROM THU NIGHT THROUGH SAT. THE RIDGE WILL
ALSO CREATE ANOTHER LOW LEVEL INVERSION...WHICH SHOULD MEAN THAT THE
INTERIOR LOWLANDS ARE AGAIN COOL AND MOSTLY SOCKED IN WITH FOG AND
LOW CLOUDS WHILE THE HIGHER TERRAIN AND COAST HAVE MORE SUN AND
ABOVE AVERAGE TEMPERATURES. THIS RIDGE IS NOT EXPECTED TO BE NEARLY
AS STRONG AS THE ONE SEEN THIS PAST WEEKEND...SO A REPEAT OF THE
RECORD SETTING WARM TEMPERATURES THAT MANY LOCATIONS SAW OVER THE
WEEKEND IS NOT EXPECTED. THE RIDGE IS CURRENTLY PROGGED TO BEGIN
SHIFTING EAST OF THE CASCADES LATE SAT INTO SUN. THIS WILL OPEN THE
DOOR FOR INCREASING CLOUDS AND PRECIPITATION CHANCES FOR LATER IN
THE WEEKEND AND EARLY NEXT WEEK. INCREASED POPS FOR THE SUN/MON TIME
FRAME AS THE FCST MODELS ARE STARTING TO SHOW DECENT AGREEMENT IN
BRINGING A WARM FRONT ONSHORE DURING THIS TIME PERIOD. PYLE
&&

.AVIATION...A MIX OF MVFR AND VFR CONDITIONS WILL CONTINUE ALONG
THE COAST THIS MORNING. FARTHER INLAND...LIFR AND IFR FOG AND
STRATUS CONTINUE...AND WILL LIKELY DO SO THROUGH APPROXIMATELY 18Z
TO 21Z TUESDAY. COOLER AIR ALOFT SHOULD DESTABILIZE THE LOWER
ATMOSPHERE ENOUGH TO ALLOW MOST TAF SITES TO IMPROVE TO A MIX OF
HIGH END IFR AND MVFR CONDITIONS TOWARDS 21Z TUESDAY. THERE MAY
EVEN BE A PERIOD OF VFR CONDITIONS AT SEVERAL TAF SITES TOWARDS
00Z WEDNESDAY...BUT CONFIDENCE IN THIS SCENARIO IS NOT HIGH. AFTER
STABILIZING A BIT OVERNIGHT...WEAK FLOW AND CONTINUING MOISTURE
SHOULD COMBINE TO ALLOW MVFR AND IFR CONDITIONS TO PERSIST AT MOST
TAF SITES IN THE WILLAMETTE VALLEY.

KPDX AND APPROACHES...EXPECT A MIX OF LIFR AND IFR CONDITIONS THIS
MORNING TO IMPROVE THIS AFTERNOON TO HIGH END IFR AND MVFR CONDITIONS.
THESE FLIGHT RESTRICTIONS SHOULD PERSIST THROUGH AT LEAST 12Z
WEDNESDAY. HOWEVER...A PERIOD OF VFR CONDITIONS CERTAINLY APPEAR
POSSIBLE TOWARDS 00Z WEDNESDAY...BUT CONFIDENCE IN THIS SCENARIO
IS NOT HIGH. EAST WINDS EARLY THIS MORNING SHOULD GIVE WAY TO A
LIGHT WEST NORTHWEST DRIFT LATER THIS MORNING. /NEUMAN

&&

.MARINE...A WEAK FRONT WILL DROP SOUTHEASTWARD ACROSS THE WATERS
TODAY AND DISSIPATE IN PLACE TONIGHT. ASIDE FROM A WIND SHIFT...EXPECT
FEW IMPACTS TO MARINE INTERESTS. A VERY WEAK LOW PRESSURE WILL
DRIFT NORTHEASTWARD OFF THE OREGON COAST WEDNESDAY...BUT
AGAIN...BRING FEW IMPACTS. HIGH PRESSURE OVER THE WATERS WILL
CONTINUE THE BENIGN WIND AND SEAS PATTERN INTO AT LEAST THE EARLY
PART OF THE UPCOMING WEEKEND. A MORE ACTIVE STORM PATTERN LOOKS TO
DEVELOP DURING THE SECOND HALF OF THE WEEKEND AND CONTINUE INTO
EARLY NEXT WEEK...BUT AT THIS MODELS DO NOT SUGGEST ANY MAJOR WIND
STORMS ON THE HORIZON. /NEUMAN

&&

.PQR WATCHES/WARNINGS/ADVISORIES...
OR...DENSE FOG ADVISORY UNTIL 10 AM PST THIS MORNING FOR CENTRAL
     WILLAMETTE VALLEY-SOUTH WILLAMETTE VALLEY.
WA...NONE.
PZ...NONE.

&&

$$

INTERACT WITH US VIA SOCIAL MEDIA
WWW.FACEBOOK.COM/NWSPORTLAND
WWW.TWITTER.COM/NWSPORTLAND

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.



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