Area Forecast Discussion
Issued by NWS Portland, OR

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FXUS66 KPQR 251708
AFDPQR

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE PORTLAND OR
907 AM PST SUN JAN 25 2015

.SYNOPSIS...HIGH PRESSURE ALOFT WILL STRENGTHEN TODAY RESULTING IN
UNSEASONABLY WARM TEMPERATURES FOR THE COAST AND HIGHER TERRAIN.
SOME LOCATIONS COULD SEE RECORD HIGH TEMPERATURES. VALLEY INVERSIONS
WILL ALSO STRENGTHEN OVER THE NEXT COUPLE OF DAYS. A VERY WEAK
FRONTAL SYSTEM NEARS THE COAST TUESDAY FOR A THREAT OF SOME
LIGHT RAIN OR DRIZZLE. HOWEVER...HIGH PRESSURE AND DRY WEATHER
ARE EXPECTED TO RETURN AROUND MID-WEEK AND LAST INTO NEXT WEEKEND.
&&

.SHORT TERM...WIDESPREAD FOG THROUGHOUT THE WILLAMETTE VALLEY AND
INTO THE LOWER COLUMBIA OF SW WA. MANY SURFACE OBSERVING SITES
REPORTING ONE-QUARTER MILE OR LESS VISIBILITY...THUS THE DENSE FOG
ADVISORY WILL CONTINUE THROUGH AT LEAST 18Z. PRIMARY FEATURES ON
WATER VAPOR IMAGERY WITH MODEL 500 MB HEIGHT OVERLAYS INCLUDE STRONG
HIGH PRES CELL CENTERED OVER NE CALIFORNIA WITH MODEL 582 DM CONTOUR
TO NEAR THE COLUMBIA RIVER. ANOTHER FEATURE OF NOTE IS A CLOSED LOW
JUST SOUTH OF BAJA.

THE 12Z KSLE SOUNDING TELLS THE SHORT-TERM STORY. VERY STRONG
SUBSIDENCE INVERSION AS EVIDENCED BY MILD EARLY MORNING TEMPERATURES
IN THE HIGHER TERRAIN. SOUNDING INDICATES THE BASE OF THE INVERSION
AROUND 800 TO 1000 FT. THUS...THE VALLEY FOG LAYER IS FAIRLY SHALLOW.
SOUNDING ALSO SHOWED TEMPS NEAR 60F AT 4500 TO 5000 FT WITH RH OF 10%
OR LESS. THE 6000 FT TIMBERLINE LODGE SENSOR WAS AT 52F AS OF 15Z.
BIGGEST CHALLENGE TODAY WILL BE INTERIOR VALLEY MAX TEMPS. WITH SUCH
WIDESPREAD FOG...IT WOULD SEEM A GOOD BET THAT SOME OF IT WILL STICK
AROUND THROUGH THE BETTER PART OF THE DAY. AFTER A WARM DAY SAT IT
LOOKS LIKE THE VALLEYS SHOULD REMAIN COOLER TODAY DESPITE THE WARM
AIR ALOFT. TERRAIN ABOVE ABOUT 1K FT WILL BE QUITE WARM FOR THIS TIME
OF YEAR. MODEL FORECASTS STILL HAVE H8 TEMPS AROUND 16 TO 18 DEG C
TODAY...WHICH WOULD PUT IT CLOSE TO THE WARMEST H8 TEMP RECORDED IN
JANUARY IN NW OREGON SINCE RECORDS BECAME AVAILABLE IN THE 1950S. A
NUMBER OF LOCATIONS IN THE COAST RANGE AND CASCADE FOOTHILLS REACHED
THE 60S SAT WITH H8 TEMPS AROUND 12 C...SO 60S SHOULD BE EVEN MORE
COMMON THERE TODAY WITH PERHAPS SOME LOCATIONS TOPPING 70. THE
BEACHES WILL ALSO BE ON THE MILD SIDE TODAY AS ANY FOG THERE SHOULD
CLEAR OUT BEFORE NOON.

THE UPPER RIDGE WILL QUICKLY MOVE E TONIGHT AND MON...RESULTING IN
MODERATING TEMPS FOR THE HIGHER TERRAIN. GFS FORECASTS 850 TEMPS OF
15 TO 18C 06Z MON...BUT DOWN TO 10 TO 13C BY 00Z TUE. HIGHER PARTS OF
THE COAST RANGE AND CASCADES COULD SEE MAX TEMPS MON FAIRLY EARLY.
VALLEYS ARE LIKELY TO SEE LOW CLOUDS AND FOG PERSISTING AS THE
INVERSION WEAKENS DURING THE DAY MON.

MODELS REMAIN PRETTY CONSISTENT IN DEPCITING A WEAK FRONT PUSHING
ONTO THE COAST BY TUE AS THE UPPER FLOW FLATTENS OUT. MODEL
CROSS SECTIONS INDICATE MOISTURE WITH THE DECAYING FRONT IS LIKELY
TO BE ON THE SHALLOW SIDE...ESPECIALLY INITIALLY LATE MON NIGHT AND
TUE MORNING. THERE IS STILL SOME MODEST LOW LEVEL UPWARD VERTICAL
MOTION ASSOCIATED WITH THE FRONT...SO WILL INCLUDE SOME LOW POPS OVER
THE N AND W PARTS OF THE AREA TUE. WEISHAAR

.LONG TERM...NO CHANGES. PREVIOUS DISCUSSION FOLLOWS. TUESDAY NIGHT
THROUGH SATURDAY...A WEAK FRONTAL SYSTEM WILL MOVE ACROSS THE REGION
LATE TUESDAY BRINGING LIGHT PRECIPITATION THROUGH LATE WEDNESDAY
NIGHT AT LEAST...AS THE FRONT DRAGS AND LINGERS. MODELS SHOW THE
UPPER LEVEL RIDGE REBUILDING BY THURSDAY...BRINGING THE RETURN OF
VALLEY FOG AND LOW CLOUDS AND BENIGN CONDITIONS. AFTERNOON
TEMPERATURES THROUGH THE EXTENDED FORECAST WILL CONTINUE TO BE
UNSEASONABLY WARM AT MOST LOCATIONS. /27
&&

.AVIATION...LIFR/VLIFR ACROSS MOST TAF SITES...EXCEPT KONP WHERE
LIGHT EASTERLY FLOW HAS RESTRICTED FOG TO THE YAQUINA BAY. EAST
WIND HAS DEVELOPED AT KAST...WHICH SHOULD CLEAR OUT FOG OVER THE
NEXT HOUR OR TWO...IMPROVING THIS SITE TO VFR BY 18Z. LIGHT WINDS
ACROSS THE AREA WILL NOT HELP MIX OUT THE FOG FROM BELOW...SO HAVE
TO WAIT FOR IT TO BURN OFF FROM ABOVE. SOUNDING TAKEN AT SALEM
THIS MORNING INDICATES THAT THE FOG WAS AROUND 2000 FT THICK AT
12Z. IMPROVEMENT TO IFR IS LIKELY AT NORTHERN SITES BY 19Z...WITH
FURTHER IMPROVEMENT TO MVFR OR POSSIBLY EVEN VFR BY AROUND 21-22Z.
NOT VERY OPTIMISTIC FOR FULL CLEARING AT KHIO...THOUGH. SOUTH
VALLEY SITES WILL BE SLOWER TO IMPROVE...WITH KEUG NOT RISING TO
IFR UNTIL 22Z...IMPROVING TO MVFR BY 23-00Z. NOT CONFIDENT THAT
KEUG WILL IMPROVE TO VFR AT ALL TODAY.

FOG TO RETURN TONIGHT LOWERING CIGS AND VIS TO IFR BY AROUND
05-07Z AT NORTHERN VALLEY SITES...AND 02-04Z AT KSLE AND KEUG.
AS FOG CONTINUES TO DEVELOP AND THICKEN...EXPECT LIFR CIGS AND VIS
TO DEVELOP BY AROUND 07-09Z AT NORTHERN SITES...AND 04-06Z IN THE
SOUTHERN WILLAMETTE VALLEY. OFFSHORE WINDS AT COASTAL SITES SHOULD
KEEP THEM VFR...BUT THERE MAY BE SOME FOG ADVECTED INTO THE
TERMINAL AT KAST FROM YOUNGS BAY AS WINDS LOOK TO BE OUT OF THE
SOUTHEAST AT THIS SITE.

KPDX AND APPROACHES...EXPECT LIFR CIGS/VSBYS TO IMPROVE TO IFR
BY 18Z. TERMINAL WILL LIKELY HANG ON TO IFR CIGS AND VIS FOR A FEW
HOURS BEFORE IMPROVING TO MVFR/VFR BY 21Z. FURTHER IMPROVEMENT
TO VFR IS POSSIBLE BY 22Z. CIGS AND VIS TO DROP BACK DOWN TO IFR
THIS EVENING AROUND 06Z...WITH LIFR CONDITIONS RETURNING BY
AROUND 08Z. -MCCOY

&&

.MARINE...LIGHT WINDS IN PLACE OVER THE AREA THROUGH EARLY MONDAY.
A SOUTHERLY SURGE MAY BRING WINDS UP BRIEFLY AT ONSET...WITH GUSTS
TO 20 TO 25 KT. SOUTHERLY WINDS THEREAFTER WILL BE GUSTING TO
AROUND 20-22 KTS...MAKING FOR A MARGINAL SMALL CRAFT WINDS EVENT.
WILL EVALUATE FURTHER WITH NEW MODEL RUNS LATER THIS MORNING.

SEAS ARE CURRENTLY AROUND 8-9 FT. SWELL AT BUOY 005 EARLIER GAVE
CONFIDENCE FOR THE 9 TO 10 FT SWELL EXPECTED TO MOVE IN LATER THIS
MORNING...BRINGING SEAS BACK UP TO AROUND 10 FT. WILL LIKELY SEE
SEAS RISE TO 10 FT BY AROUND NOON TODAY. SEAS LOOK TO EASE BACK
BELOW 10 FT AROUND MIDNIGHT TONIGHT. THERE MAY BE A PERIOD OF SEAS
GETTING BACK UP TO 10 FT WITH INCREASING SOUTHERLY WINDS MIDDAY
MONDAY...BUT SHOULD DROP BACK BELOW 10 FT MONDAY NIGHT AND SUBSIDE
TO REMAIN WELL BELOW 10 FT THROUGH MIDWEEK. -MCCOY

&&

.PQR WATCHES/WARNINGS/ADVISORIES...
OR...DENSE FOG ADVISORY UNTIL 10 AM PST THIS MORNING FOR CENTRAL
     WILLAMETTE VALLEY-GREATER PORTLAND METRO AREA-LOWER
     COLUMBIA-SOUTH WILLAMETTE VALLEY.

WA...DENSE FOG ADVISORY UNTIL 10 AM PST THIS MORNING FOR GREATER
     VANCOUVER AREA-I-5 CORRIDOR IN COWLITZ COUNTY.

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

     SMALL CRAFT ADVISORY FOR ROUGH COLUMBIA RIVER BAR UNTIL 10 AM
     PST THIS MORNING.

     SMALL CRAFT ADVISORY FOR ROUGH COLUMBIA RIVER BAR FROM 6 PM TO
     11 PM PST THIS EVENING.

&&

$$

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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