Area Forecast Discussion
Issued by NWS Portland, OR

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FXUS66 KPQR 262209
AFDPQR

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE PORTLAND OR
209 PM PST MON JAN 26 2015

.SYNOPSIS...A STRONG UPPER RIDGE WILL FLATTEN AND MOVE AWAY TO THE
EAST THROUGH TONIGHT...GRADUALLY WEAKENING THE LOW LEVEL INVERSION. A
VERY WEAK FRONTAL SYSTEM WILL APPROACH THE COAST LATE TONIGHT...
BEGIN TO SPREAD INLAND IN THE NORTH TUESDAY...THEN LINGER OVER
NORTHWEST OREGON AND SOUTHWEST WASHINGTON THROUGH WEDNESDAY. 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 NEXT WEEKEND OR EARLY NEXT WEEK.
&&

.SHORT TERM...TONIGHT THROUGH THURSDAY...THE FOG HAS MOSTLY CLEARED
IN CLARK AND MULTNOMAH COUNTIES AND TO THE NORTH THIS AFTERNOON.
THERE HAS BEEN SOME EROSION OF THE FOG AND LOW CLOUDS IN THE SOUTH
WILLAMETTE VALLEY AS WELL. THE LOW CLOUDS AND REMAINING PATCHY FOG
ARE HANGING TOUGH IN THE CENTRAL VALLEY AND NORTH INTO THE TUALATIN
VALLEY. THERE WILL PROBABLY BE A BIT MORE EROSION OF THE CENTRAL
MASS OF LOW CLOUDS AND FOG BUT IT WILL PROBABLY NOT CLEAR BEFORE
AGAIN EXPANDING THIS EVENING AND OVERNIGHT TONIGHT.

THE UPPER RIDGE THAT HAS BEEN OVER THE PACIFIC NORTHWEST THE LAST
COUPLE OF DAYS HAS BEEN MOVING EAST AND WEAKENING OR FLATTENING AND
WILL CONTINUE TO DO SO TONIGHT...WEAKENING THE TEMPERATURE INVERSIONS
ALOFT BUT NOT ENOUGH TO MIX THE FOG VERTICALLY. THUS EXPECT MORE FOG
AND LOW CLOUDS TO THICKEN AND REDEVELOP TONIGHT.

THERE IS A FRONTAL ZONE OUT NEAR 130W THAT THE MODELS CONTINUE TO
SHOW WILL MOVE INTO THE COASTAL WATERS AND CLOSE TO THE COAST
TONIGHT. THIS SYSTEM WILL WEAKEN A LOT AS IT APPROACHES. IT IS
ALREADY BEGINNING TO TURN THE LOW LEVEL FLOW ONSHORE NEAR THE
COAST...AS EVIDENCED BY THE BANK OF LOW CLOUDS NEAR THE COAST THAT
HAS MOVED ONSHORE INTO GRAYS HARBOR. EXPECT SOME LIGHT RAIN OR
DRIZZLE TO REACH ESPECIALLY THE NORTH COAST TONIGHT AND EARLY
TUESDAY. THE FRONTAL BAND WILL SLOWLY EASE INLAND ALONG THE COLUMBIA
RIVER TUESDAY...THEN HANG UP OVER THE NORTHERN PART OF OUR FORECAST
AREA...SAY FROM ABOUT SALEM NORTHWARD...TUESDAY NIGHT AND WEDNESDAY
BEFORE SLOWLY DRYING OUT. AMOUNTS WILL BE LIGHT...BUT EXPECT SOME
DRIZZLY PERIODS WITH SOME LIGHT RAIN TUESDAY NIGHT INTO WEDNESDAY.
SOME DRIZZLE SHOULD ALSO REACH THE CENTRAL OREGON COAST...BUT EXPECT
IT TO PROBABLY STAY DRY IN THE SOUTH WILLAMETTE VALLEY.

THE FRONTAL BAND WILL LIKELY LIFT THE FOG A BIT AND MAKE IT A BIT
PATCHIER IN THE NORTH HALF OF THE VALLEY TUESDAY AND WEDNESDAY. THE
SOUTH VALLEY WILL PROBABLY NOT SEE MUCH CHANGE IN THE FOG THE NEXT
COUPLE OF DAYS.

THERE IS STILL A VERY WEAK UPPER DISTURBANCE MOVING THROUGH ON
WEDNESDAY NIGHT AND THURSDAY THAT MAY KEEP THE INVERSION FROM GETTING
TOO STRONG YET AND AFFECTING THE AMOUNT OF FOG A BIT. THIS ALSO
RESTRICTS HOW STRONGLY THE UPPER RIDGE WILL INITIALLY REBUILD. BUT
THE LEFTOVER BOUNDARY SHOULD BE DRYING OUT. THERE IS A HINT OF A
LITTLE WEAK NORTHERLY LOW LEVEL FLOW ON THURSDAY AFTERNOON THAT IF
THIS DEVELOPS...MIGHT GIVE US SOME SUN BREAKS THURSDAY AFTERNOON.
TOLLESON

.LONG TERM...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 TIMEFRAME
AS THE FCST MODELS ARE STARTING TO SHOW DECENT AGREEMENT IN BRINGING
A WARM FRONT ONSHORE DURING THIS TIME PERIOD. PYLE
&&

.AVIATION...LIGHT WINDS HAVE INCREASED A BIT THROUGH THE INTERIOR
THIS AFTERNOON...ALLOWING SOME AREAS OF FOG TO ERODE AND CLEAR.
HOWEVER...POCKETS OF FOG REMAIN AT KHIO AND IN PORTIONS OF THE S AND
CENTRAL VALLEY. EXPECT FAIRLY WIDESPREAD DENSE FOG TO AGAIN SETTLE
INTO THE INTERIOR THIS EVENING AROUND 02-03Z FOR THE CENTRAL AND
SOUTH VALLEY AND ANY SLIGHT IMPROVEMENT AT KHIO WILL BE SHORT LIVED
WITH FOG DEVELOPING THERE AS WELL. E WINDS THROUGH THE GORGE CONTINUE
TO MAINTAIN CLEAR SKIES AT KTTD...THOUGH THIS WIND SHOULD EASE A BIT
LATER TONIGHT WHICH MAY PERMIT SOME PATCHY FOG DEVELOPMENT. A LOWER
STRATUS DECK AROUND 2000 FT WILL PUSH ONSHORE FOR KAST AND KONP
AROUND 03Z AND PREVAIL THROUGH THE PERIOD AS FRONTAL ZONE PUSHES
ONSHORE...BUT LOWER CONFIDENCE ON HEIGHT OF THIS DECK.

KPDX AND APPROACHES...VFR UNDER MOSTLY CLEAR SKIES AT THE TERMINAL
THIS AFTERNOON. A LIGHT E WIND MAY MAINTAIN MORE CLEARING A BIT INTO
THIS EVENING...BUT STILL EXPECT TO SEE SOME FOG DEVELOP BETWEEN
09Z-12Z TONIGHT...ESPECIALLY AS WINDS EASE A BIT. SOMEWHAT LOWER
CONFIDENCE FORECAST TONIGHT WITH RESPECT TO BOTH ONSET AND
DISSIPATION OF FOG. INCREASING MID CLOUDS ON TUE AS WEAKENING FRONTAL
BAND APPROACHES BUT EXPECT HIGH MVFR TO VFR CIGS AFT 19Z TUE. CULLEN
&&

.MARINE...GUSTY S WINDS CONTINUE OVER THE NORTHERN WATERS THIS
AFTERNOON...AND HAVE BEEN A BIT STRONGER WITH SUSTAINED WINDS PUSHING
ABOVE 20 KT WITH GUSTS TO NEAR 30 KT. THEREFORE...HAVE ISSUED A SMALL
CRAFT ADVISORY THROUGH 6 PM FOR THE NORTHERN ZONES. WINDS WILL EASE
THIS EVENING...BUT CANNOT RULE OUT A FEW GUSTS TO 25 KT N OF CANNON
BEACH THROUGH AROUND 8 OR 9 PM TONIGHT. MEANWHILE... SEAS CONTINUE TO
HOLD AROUND 9 FT AND WILL CONTINUE TO MAINTAIN AT THIS LEVEL
TONIGHT...BEFORE GRADUALLY DECREASING OVER THE NEXT FEW DAYS.

A WEAK FRONT WILL SLIDE SE ACROSS THE WATERS AND STALL OUT AS IT
WEAKENS ON TUE INTO WED BRINGING A WIND SHIFT BUT WINDS REMAIN LIGHT.
HIGH PRESSURE THEN REBUILDS FOR THU AND FRI...AND PERHAPS INTO SAT. A
MORE ACTIVE PATTERN MAY DEVELOP BY LATE IN THE WEEKEND THROUGH EARLY
NEXT WEEK...THROUGH SOME UNCERTAINTY REMAINS IN THE TIMING AND
STRENGTH OF THESE SYSTEMS. CULLEN
&&

.PQR WATCHES/WARNINGS/ADVISORIES...
OR...NONE.
WA...NONE.
PZ...SMALL CRAFT ADVISORY FOR WINDS UNTIL 6 PM PST THIS EVENING FOR
     COASTAL WATERS FROM CAPE SHOALWATER WA TO CASCADE HEAD OR OUT 60
NM.

     SMALL CRAFT ADVISORY FOR ROUGH COLUMBIA RIVER BAR FROM 7 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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