Area Forecast Discussion
Issued by NWS Portland, OR

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FXUS66 KPQR 290447
AFDPQR

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE PORTLAND OR
847 PM PST WED JAN 28 2015

.SYNOPSIS...A WEAK UPPER SHORT WAVE WILL MOVE OVER THE REGION LATE
TONIGHT INTO THURSDAY MORNING MAINTAINING CLOUDY SKIES AND POSSIBLY
PRODUCING SOME DRIZZLE. AN UPPER LEVEL RIDGE WILL BUILD OVER THE
PACIFIC NORTHWEST THURSDAY AFTERNOON AND FRIDAY AND HOLD THROUGH
SATURDAY FOR MORE DRY AND MILD WEATHER. EASTERLY WINDS WILL DEVELOP
THROUGH THE GORGE...BUT WITH AREAS OF FOG AND STABLE CONDITIONS BELOW
TEMPERATURE INVERSIONS IN MOST VALLEY AREAS. THE NEXT CHANCE
FOR RAIN IS FOR LATE IN THE WEEKEND.

&&

.UPDATE...HAVE REDUCED POPS FOR THIS EVENING AS RAIN CHANCES LOOK
MINIMAL. THE BEST CHANCE FOR ANY PRECIPITATION WILL BE LATE TONIGHT
AS A WEAK UPPER LEVEL SHORTWAVE TROUGH FROM THE SOUTH MOVES NORTHWARD
OVER NW OREGON...BUT STILL THINK IT WILL BE MAINLY DRIZZLE. THE
TROUGH SHOULD PROVIDE ENOUGH MIXING TO PREVENT WIDESPREAD DENSE FOG
THURSDAY MORNING. AN UPPER RIDGE WILL BUILD THURSDAY AFTERNOONWITH
INCREASING EAST WINDS. EAST WINDS OF 25 MPH MAY GUST THROUGH THE
GORGE AND KEEP FOG AWAY FROM THE EASTERN METRO AREAS THU NIGHT AND
FRIDAY...BUT EXPECT VALLEY FOG ELSEWHERE. TJ

PREVIOUS SHORT TERM...TONIGHT THROUGH SATURDAY...THE BOUNDARY THAT
HAS BEEN OVER PARTS OF SOUTHWEST WASHINGTON LATE TUESDAY INTO THIS
MORNING HAS CONTINUED TO FALL APART AND THERE ARE NOT MANY CLOUDS
LEFT. THE MAIN CLOUDS ARE THE PERSISTENT VALLEY LOW CLOUDS AS WELL AS
SOME HIGHER CLOUDS ASSOCIATED WITH AN UPPER SHORT WAVE ALONG THE
COAST.

THE UPPER SHORT WAVE ALONG THE COAST WILL BE OVER OUR FORECAST AREA
TONIGHT INTO EARLY THURSDAY...THEN SLOWLY BEGIN TO SLIDE SOUTHEAST
DURING THE DAY THURSDAY AND MOVE OUT OF THE AREA THURSDAY NIGHT. WILL
CONTINUE TO KEEP A SMALL CHANCE OF SHOWERS INTO THURSDAY MORNING AS
THIS FEATURE MOVES THROUGH THOUGH CONFIDENCE OF ANY SHOWERS HITTING A
RAIN GAGE IS NOT HIGH. WILL ALSO KEEP CLOUDS OVER THE AREA FROM IT AS
WELL.

THE CLOUDS WILL FINALLY COLLAPSE AND CLEAR THURSDAY NIGHT AS THE
UPPER SHORT WAVE MOVES AWAY AND AN UPPER RIDGE STARTS TO MOVE IN.
EXPECT AREAS OF FOG TO REDEVELOP THURSDAY NIGHT AND CONTINUE THROUGH
AT LEAST FRIDAY MORNING ESPECIALLY IN THE VALLEYS. WILL SEE SOME
MODEST EAST WINDS THROUGH THE GORGE AS WELL THURSDAY NIGHT AND
FRIDAY...THAT MAY BRING SOME CLEARING TO AT LEAST THE NORTH VALLEY
AREAS FRIDAY AFTERNOON. NOT MUCH CHANGE IN THE PATTERN FROM FRIDAY TO
SATURDAY...WITH VALLEY FOG CONTINUING AND ALSO MORE MODEST EAST WIND
NEAR THE GORGE. TOLLESON

.LONG TERM...NO CHANGES. PREVIOUS DISCUSSION FOLLOWS...SATURDAY NIGHT
THROUGH WEDNESDAY...THE UPPER RIDGE BEGINS TO SHIFT INLAND SATURDAY
NIGHT AS A LARGE LOW PRESSURE SYSTEM REMAINS IN THE CENTRAL NORTH
PACIFIC. MODELS REMAIN IN GOOD AGREEMENT THAT A MOIST FRONTAL SYSTEM
MOVES INTO THE REGION SUNDAY WITH PLENTY OF SHOWERS CONTINUING INTO
EARLY MONDAY. SNOW LEVELS LOWER A BIT BUT STILL LOOK TO REMAIN WELL
ABOVE THE CASCADE PASSES. ANOTHER FRONT MAY ARRIVE AROUND TUESDAY.
MODEL SOLUTIONS THEN DIVERGE A BIT FOR MIDWEEK...WITH THE ECMWF
CONTINUING A STREAM OF MOISTURE INTO THE
REGION WHILE THE GFS REBUILDS A RIDGE OVER THE AREA AND PUSHES THE
MOISTURE NORTH. GIVEN THIS UNCERTAINTY...AND THE FACT THAT THE GFS
ENSEMBLE MEMBERS MAINTAIN A WIDE RANGE ENCOMPASSING BOTH OF THESE
SOLUTIONS...OPTED TO BLEND AND MAINTAIN CHANCE POPS FOR TUESDAY AND
WEDNESDAY.  CULLEN
&&

.AVIATION...FOG AND LOW STRATUS IS CURRENTLY REDEVELOPING OVER
PORTIONS OF THE WILLAMETTE VALLEY THIS EVENING. AS THE FOG
SPREADS AND THICKENS EXPECT TO SEE WIDESPREAD IFR TO LIFR CIGS AND
VIS THROUGH TOMORROW MORNING AT MOST INLAND TAF SITES.
HOWEVER...EASTERLY WINDS NEAR THE COLUMBIA RIVER GORGE SHOULD KEEP
VFR CONDITIONS NEAR KTTD. OFFSHORE FLOW ALONG THE COAST SHOULD
ALSO KEEP VFR CONDITIONS AT THE COASTAL TAF SITES. NORTHERLY WINDS
ARE EXPECTED TO DEVELOP ACROSS THE REGION TOMORROW WHICH SHOULD
ALLOW THE VALLEY FOG AND LOW STRATUS TO CLEAR IN THE AFTERNOON
WITH VFR CONDITIONS EXPECTED AT MOST SITES BETWEEN 18-21Z.

KPDX AND APPROACHES...VFR CONDITIONS ARE EXPECTED THROUGH
TOMORROW EVENING AS EASTERLY WINDS DEVELOP NEAR THE COLUMBIA RIVER
GORGE. HOWEVER...THERE IS A SLIGHT CHANCE THAT WE MAY SEE A BRIEF
PERIOD OF MVFR TO IFR CIGS AND VIS LATE TONIGHT IF THE WINDS
WEAKEN...WHICH SHOULD ALLOW FOG AND LOW STRATUS TO REDEVELOP. /64

&&

.MARINE...NO SIGNIFICANT CHANGES WERE MADE WITH THE EVENING UPDATE
AS THINGS CONTINUE TO PROGRESS AS EXPECTED. THE LOW PRESSURE
CIRCULATION IS CONTINUING TO MOVE NORTHWARD ACROSS OUR WATERS
WITH HIGH PRESSURE BUILDING IN BEHIND IT. EXPECT HIGH PRESSURE TO
REMAIN OVER THE PACIFIC NORTHWEST FOR THE NEXT COUPLE OF DAYS AS A
THERMAL LOW STRENGTHENS OVER NORTHERN CALIFORNIA. EXPECT WINDS TO
REMAIN BELOW 20 KT WITH SEAS BELOW 10 FT THROUGH AT LEAST
SATURDAY. /64

THE NEXT FRONTAL SYSTEM APPEARS TO BE ON TAP FOR SAT NIGHT INTO
EARLY SUN. THIS SYSTEM APPEARS TO WEAKEN SIGNIFICANTLY BEFORE IT
NEARS SHORE...AND ASSOCIATED WINDS ARE NOT MODELED TO REACH SMALL
CRAFT CRITERIA. A SECOND STRONGER FRONT IS BEING ADVERTISED FOR
SUN NIGHT INTO MON. THEN A MORE ACTIVE PATTERN APPEARS POSSIBLE
FOR NEXT WEEK...ALTHOUGH CONFIDENCE IN THE DETAILS IS LOW AT THIS
TIME. PYLE

&&

.PQR WATCHES/WARNINGS/ADVISORIES...
OR...NONE.
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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