577
FXUS66 KPQR 161034
AFDPQR
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE PORTLAND OR
334 AM PDT WED SEP 16 2026
SYNOPSIS
A TRANSITION TO WARMER AND DRIER WEATHER IS
UNDERWAY TODAY AS OFFSHORE FLOW DEVELOPS ACROSS THE REGION.
TEMPERATURES PEAK THURSDAY BEFORE ONSHORE FLOW RETURNS, WHILE
DRY CONDITIONS ARE EXPECTED TO PERSIST THROUGH THE WEEKEND. A
COOLER PATTERN MAY DEVELOP EARLY NEXT WEEK AS TROUGHING
APPROACHES FROM THE GULF OF ALASKA.
DISCUSSION...NOW THROUGH TUESDAY
THE WEAK UPPER-LEVEL TROUGH
THAT MOVED THROUGH THE REGION TUESDAY IS SHIFTING SOUTH INTO
NORTHERN CALIFORNIA TODAY AS RIDGING STRENGTHENS OFFSHORE AND
THERMAL TROUGHING DEVELOPS INLAND. THE WILL MARK A QUICK
TRANSITION TOWARD WARMER AND DRIER CONDITIONS, WITH OFFSHORE
FLOW INCREASING THROUGH THE COLUMBIA RIVER GORGE AND CASCADE
GAPS. EASTERLY TO NORTHEASTERLY WINDS WILL ALSO DEVELOP ACROSS
THE FOOTHILLS AND COAST RANGE, WHILE NORTHERLY WINDS INCREASE
THROUGH THE WILLAMETTE VALLEY. THE COMBINATION OF DOWNSLOPING
FLOW AND INCREASING SUBSIDENCE WILL ALLOW TEMPERATURES TO
REBOUND INTO THE UPPER 70S TO LOWER 80S ACROSS THE INTERIOR
VALLEYS, WHILE COASTAL TEMPERATURES CLIMB INTO THE LOW TO MID
70S.
THE STRONGEST WINDS ARE EXPECTED THROUGH THE GORGE AND OTHER
EAST-WEST ORIENTED GAPS IN THE CASCADES, WHERE GUSTS AROUND
20-30 MPH ARE LIKELY. EXPOSED RIDGETOPS COULD SEE LOCALLY
STRONGER GUSTS APPROACHING 40 MPH, ALTHOUGH THE PROBABILITY OF
EXCEEDING 40 MPH REMAINS RELATIVELY LOW AT 5-20 PERCENT.
NORTHERLY WINDS WILL ALSO MAKE FOR A BREEZY DAY ACROSS THE
CENTRAL AND SOUTHERN WILLAMETTE VALLEY, WITH GUSTS GENERALLY
AROUND 20-25 MPH AND ROUGHLY A 10-30 PERCENT CHANCE OF GUSTS
EXCEEDING 30 MPH. DESPITE THE DRIER AND WINDIER PATTERN,
AFTERNOON HUMIDITY IS EXPECTED TO REMAIN ABOVE 30 PERCENT ACROSS
MOST AREAS, LIMITING THE POTENTIAL FOR RAPID FIRE SPREAD.
THURSDAY SHOULD BE THE WARMEST DAY OF THE WEEK AS WEAK OFFSHORE
FLOW PERSISTS INTO THE MORNING. THERE IS MODERATE TO HIGH
CONFIDENCE THAT INTERIOR VALLEY TEMPERATURES WILL REACH THE
LOWER 80S (65-95% CHANCE OF HITTING 80 DEGREES, LOWEST TO
HIGHEST CHANCES FROM EUGENE NORTHWARD), WITH CONTINUED DRY
CONDITIONS ACROSS MOST OF THE FORECAST AREA. THE THERMAL TROUGH
THEN WEAKENS THURSDAY AFTERNOON, ALLOWING ONSHORE FLOW TO RETURN
AND BRINGING A GRADUAL MODERATION IN TEMPERATURES. AN UPPER-
LEVEL LOW SHIFTING NORTHEAST FROM NORTHERN CALIFORNIA TOWARD THE
GREAT BASIN COULD DRAW ENOUGH MOISTURE NORTHWARD TO SUPPORT A
SMALL CHANCE FOR THUNDERSTORMS ALONG THE CREST OF THE LANE
COUNTY CASCADES. CURRENT PROBABILITIES REMAIN ONLY 5-10 PERCENT,
WITH THE REST OF THE FORECAST AREA EXPECTED TO REMAIN DRY AND
OUTSIDE OF THE THUNDERSTORM THREAT. SPC HAS INCLUDED A PORTION
OF THE LANE COUNTY CASCADES IN A GENERAL THUNDERSTORM RISK, SO
THIS POTENTIAL WILL NEED TO BE MONITORED AS THURSDAY APPROACHES.
THE OVERALL PATTERN BECOMES LESS CERTAIN FRIDAY THROUGH THE
WEEKEND AS ENSEMBLE GUIDANCE DIFFERS ON THE STRENGTH AND
POSITION OF THE UPPER-LEVEL RIDGE. SOME SOLUTIONS MAINTAIN WEAK
TROUGHING OVER THE GREAT BASIN, WHICH WOULD FAVOR TEMPERATURES
CLOSER TO THE LOWER 70S, WHILE OTHERS BUILD STRONGER RIDGING
OVER THE PACIFIC NORTHWEST AND SUPPORT TEMPERATURES INTO THE LOW
80S. SUNDAY HAS SLIGHTLY HIGHER CHANCES OF WARM TEMPERATURES,
WITH TEMPERATURES ANYWHERE FROM THE MID 70S TO MID 80S EXPECTED.
DESPITE THE TEMPERATURE SPREAD, THE SIGNAL FOR DRY WEATHER
REMAINS STRONG THROUGH THE WEEKEND.
LOOKING AHEAD TO EARLY NEXT WEEK, ENSEMBLE GUIDANCE INCREASINGLY
SUPPORTS AN UPPER-LEVEL TROUGH DROPPING SOUTHEAST FROM THE GULF
OF ALASKA. THE EVENTUAL POSITION AND STRENGTH OF THIS FEATURE
REMAIN UNCERTAIN, BUT THE PATTERN WOULD FAVOR A RETURN TO
STRONGER ONSHORE FLOW AND COOLER TEMPERATURES ACROSS THE REGION.
~12
AVIATION...THROUGH 12Z THURSDAY
EXPECT MOSTLY VFR CONDITIONS
THROUGHOUT THE AIRSPACE DURING THE TAF PERIOD, WITH THE ONLY
EXCEPTION OF A 20-30% CHANCE OF LIFR/IFR CONDITIONS AT COASTAL
TERMINALS BEFORE 18Z WED AND THEN A 20-40% CHANCE OF LIFR/IFR
CONDITIONS AFTER 06-08Z THU. INLAND TERMINALS WILL STAY VFR
THROUGH THE PERIOD, WITH ONLY A 10-20% CHANCE OF MVFR CIGS
BEFORE 18Z WED.
OFFSHORE WINDS OUT OF THE EAST/NORTHEAST BEGIN TO DEVELOP AT
THE SURFACE EARLY THIS MORNING, INCREASING TO AROUND 10-15 KT
WITH GUSTS OF 20-25 KT DURING THE AFTERNOON. WINDS WILL BE THE
STRONGEST AND MORESO OUT OF THE NORTH TO THE SOUTH OF THE
AIRSPACE, MAINLY AT KONP, KSLE, AND KEUG. WINDS WILL THEN WEAKEN
AROUND 01-04Z THU.
KPDX AND APPROACHES...VFR CONDITIONS EXPECTED THROUGH THE TAF
PERIOD WITH MOSTLY CLEAR SKIES. NORTHWESTERLY WINDS WILL BECOME
NORTHERLY AT 8-10 KT BY 18Z WED, THEN NORTHEASTERLY WITH GUSTS
UP TO 20 KT BY 21Z WED. UNCERTAINTY REMAINS ON TIMING AND THE
MAGNITUDE OF THE WIND DIRECTION SHIFT. WINDS SHOULD WEAKEN
TO BELOW 8 KT BY 01-03Z THU. ~12
MARINE
NORTH WINDS WILL CONTINUE TONIGHT AS HIGH PRESSURE
BUILDS OFFSHORE. A STRENGTHENING THERMAL TROUGH ALONG THE COAST
WILL INCREASE PRESSURE GRADIENTS ACROSS THE COASTAL WATERS
TODAY, INCREASING NORTHERLIES TO 15-20 KT WITH GUSTS UP TO 25 KT
SOUTH OF CAPE FALCON IN THE LATE MORNING AND PERSISTING
OVERNIGHT. ISOLATED GUSTS AS HIGH AS 30 KT ARE POSSIBLE OVER THE
SOUTHERN OUTER WATERS TO THE SOUTH OF CAPE FOULWEATHER, BEYOND
10 NM OFFSHORE. GUSTS ARE EXPECTED TO APPROACH 20-25 KT BY LATE
WEDNESDAY MORNING FOR THE CENTRAL AND SOUTHERN OFFSHORE WATERS,
AND BY NOON OVER THE INNER WATERS. AS A RESULT, SMALL CRAFT
ADVISORIES WILL BEGIN AT 11 AM WEDNESDAY AND END AT 11 PM
WEDNESDAY, ALTHOUGH THE OUTER WATERS SOUTH OF CAPE FOULWEATHER
WILL MAINTAIN THE SMALL CRAFT ADVISORY UNTIL 2 AM THURSDAY AS
WINDS ARE FORECASTED TO REMAIN ELEVATED A LITTLE LONGER.
WINDS ARE LIKELY TO EASE LATER IN THE WEEK AS LOW PRESSURE
DRIFTS OFFSHORE. A PERSISTENT NORTHWEST SWELL AROUND 4 TO 5 FT
AT 7 TO 8 SECONDS IS EXPECTED TO CONTINUE THROUGH AT LEAST
FRIDAY. SEAS HAS BEGUN TO BUILD TOWARDS 6 FT TODAY AS NORTHERLY
WINDS STRENGTHEN. NORTHERLIES STRENGTHEN AGAIN OVER THE WEEKEND,
WITH AROUND A 50-70% CHANCE OF WIND GUSTS EXCEEDING 21 KT. THE
WATERS NORTH OF CAPE FALCON HAVE A 30-40% CHANCE OF WIND GUSTS
EXCEEDING 21 KT ON SATURDAY, BUT INCREASE TO 60-70% BY SUNDAY.
~12/23
PQR WATCHES/WARNINGS/ADVISORIES
OR...NONE.
WA...NONE.
PZ...SMALL CRAFT ADVISORY FROM 11 AM THIS MORNING TO 11 PM PDT THIS
EVENING FOR PZZ252-253-272.
SMALL CRAFT ADVISORY FROM 11 AM THIS MORNING TO 2 AM PDT
THURSDAY FOR PZZ273.
WWW.WEATHER.GOV/PORTLAND
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