481
FXUS66 KPQR 151748 AAA
AFDPQR
AREA FORECAST DISCUSSION...UPDATED
NATIONAL WEATHER SERVICE PORTLAND OR
1047 AM PDT MON SEP 15 2025
UPDATED AVIATION DISCUSSION.
SYNOPSIS
SHOWERS ASSOCIATED WITH SUNDAYS FRONTAL PASSAGE HAVE
DIMINISHED, LEAVING DRY AND CALMER CONDITIONS FOR TODAY.
OFFSHORE FLOW WILL STRENGTHEN TONIGHT INTO TUESDAY, PRODUCING
WARM TEMPERATURES AND BREEZY TO LOCALLY STRONG EASTERLY WINDS
THROUGH THE COLUMBIA RIVER GORGE AND CASCADE GAPS. ONSHORE FLOW
AND A WEAK FRONT BRUSH THE COAST MIDWEEK WITH ONLY LIMITED
PRECIPITATION POTENTIAL. A BROADER TROUGHING PATTERN FROM THE
NORTHEAST PACIFIC MAY THEN BRING INCREASING RAIN CHANCES INTO
THE WEEKEND.
SHORT TERM...NOW THROUGH TUESDAY NIGHT
AS OF 4 AM, SKIES
REMAIN MOSTLY CLEAR ACROSS INTERIOR VALLEYS WITH ONLY PATCHY
STRATUS NOTED OVER THE CASCADES. FOG HAS NOT BEEN OBSERVED SO
FAR, THOUGH PATCHY DEVELOPMENT IS STILL POSSIBLE NEAR SUNRISE IN
MORE SHELTERED VALLEYS OF SOUTHWEST WASHINGTON. CONFIDENCE IN
WIDESPREAD DENSE FOG REMAINS LOW.
BUILDING SHORTWAVE RIDGING TODAY ENSURES DRY CONDITIONS WITH
NEAR-SEASONAL HIGHS - MID TO UPPER 70S INLAND AND MID 60S AT THE
COAST. BY THIS EVENING, A THERMALLY INDUCED SURFACE TROUGH
STRENGTHENS ALONG THE COAST, TIGHTENING THE OFFSHORE PRESSURE
GRADIENT (-4 TO -6 MB KTTD-KDLS). THIS SETS UP BREEZY TO LOCALLY
STRONG EASTERLIES BEGINNING TONIGHT.
WINDS WILL PEAK LATE TONIGHT INTO TUESDAY MORNING, STRONGEST
THROUGH THE WESTERN COLUMBIA GORGE AND CASCADE GAPS WHERE GUSTS
OF 25-40 MPH ARE EXPECTED. THERE IS A 40-60% CHANCE FOR GUSTS
EXCEEDING 40 MPH IN FAVORED LOCATIONS SUCH AS CROWN POINT AND
THREE CORNER ROCK. WINDS WILL GRADUALLY EASE TUESDAY EVENING AS
GRADIENTS RELAX, WITH GUSTS GENERALLY DROPPING BELOW 20 MPH
OUTSIDE OF EXPOSED TERRAIN.
TEMPERATURES CLIMB SHARPLY TUESDAY UNDER DOWNSLOPE OFFSHORE FLOW
AND COMPRESSIONAL WARMING. INTERIOR VALLEYS CARRY A 70-90%
CHANCE OF REACHING OR EXCEEDING 85 DEGREES, WITH A 10-30% CHANCE
OF TOUCHING 90 DEGREES. A FEW ISOLATED SITES ARE LIKELY TO REACH
90 DEGREES. ELEVATED FIRE WEATHER CONDITIONS WILL ACCOMPANY THE
WARM, DRY, AND BREEZY PATTERN, THROUGH THE STRONGEST WINDS
SHOULD PRECEDE THE LOWEST DAYTIME HUMIDITIES, REDUCING OVERLAP
OF CRITICAL THRESHOLDS.
LONG TERM...WEDNESDAY THROUGH SUNDAY
ONSHORE FLOW RETURNS
WEDNESDAY AS A WEAK TROUGH BRUSHES THE REGION. LIGHT RAIN
(10-20% CHANCE) WILL BE CONFINED TO THE IMMEDIATE COAST AND
ADJACENT WATERS, WHILE INLAND AREAS ARE EXPECTED TO REMAIN DRY.
BEYOND MIDWEEK, ENSEMBLE GUIDANCE DIVERGES ON THE AMPLITUDE AND
TIMING OF SUBSEQUENT TROUGHING. ROUGHLY 80% OF MEMBERS FAVOR
DRIER WEATHER THURSDAY INTO FRIDAY, WHILE 20% MAINTAIN LIGHT
SHOWERS ALONG THE COAST TIED TO CONTINUED WEAK TROUGHING.
ATTENTION THEN TURNS TO THE WEEKEND, WHEN MORE ORGANIZED
TROUGHING FROM THE NORTHEAST PACIFIC DIGS INTO THE REGION. THIS
FEATURE MAY REINTRODUCE PRECIPITATION CHANCES AREA-WIDE, WITH
CURRENT ENSEMBLE PROBABILITIES SHOWING A 20-40% CHANCE FOR
MEASURABLE RAINFALL ACROSS SOUTHWEST WASHINGTON AND NORTHWEST
OREGON LATE SATURDAY INTO SUNDAY. CONFIDENCE IS MODEST AT THIS
RANGE, BUT TRENDS SUPPORT INCREASING RAIN CHANCES OVER THE
WEEKEND COMPARED TO THE MIDWEEK SYSTEM. TEMPERATURES COOL
ACCORDINGLY, WITH ENSEMBLE RANGES GENERALLY MID 70S TO LOW 80S
SATURDAY, THEN LOW TO UPPER 70S BY SUNDAY. ~HALL
AVIATION
EXPECT CLEAR SKIES AND WIDESPREAD VFR FLIGHT
CONDITIONS ACROSS THE REGION MONDAY AFTERNOON THROUGH TUESDAY
AFTERNOON AS HIGH PRESSURE BUILDS INTO THE AREA. LOW-LEVEL
OFFSHORE FLOW WILL DEVELOP TONIGHT, BRINGING GUSTY EASTERLY WINDS
UP TO 25 KT AT KPDX AND KTTD. WINDS FROM KUAO TO KSLE AND KEUG
WILL BE OUT OF THE NORTH TO NORTHEAST, WITH GUSTS UP TO 15-20 KT,
EXCEPT UP TO 25 KT AT KEUG. OFFSHORE WINDS WILL GRADUALLY WEAKEN
TUESDAY AFTERNOON AND EVENING.
KPDX AND APPROACHES...VFR CONDITIONS ARE EXPECTED TO CONTINUE
THROUGH 18Z TUESDAY. GUSTY EASTERLY WINDS DEVELOP TONIGHT AND
CONTINUE THROUGH TOMORROW, STRONGEST BETWEEN 10-18Z WHEN GUSTS UP
TO 25 KT ARE LIKELY. -TK
MARINE
NORTHWESTERLY WINDS, INCREASING TO AROUND 10-15 MPH
WITH GUSTS UP TO 20 KT THIS AFTERNOON AND EVENING, MAINLY FOR
ZONES PZZ272, 273, 252, AND 253. THERE COULD BE SOME ISOLATED
GUSTS UP TO 25 KT FOR THOSE ZONES AS WELL, BUT NOT WIDESPREAD
ENOUGH FOR A SMALL CRAFT ADVISORY AT THIS TIME. WILL MONITOR
OBSERVATIONS IN CASE THIS CHANGES. SEAS 4-6 FEET AT 10-12 SECONDS
EXPECTED THROUGH THE MIDDLE OF THE WEEK AS A NORTHWESTERLY SWELL
MOVES INTO THE WATERS.
WEAK OFFSHORE FLOW WILL DEVELOP BRIEFLY LATE TONIGHT INTO TUESDAY
MORNING. HOWEVER, THIS WILL BE SHORT LIVED AS ANOTHER LOW
PRESSURE SYSTEM AND ASSOCIATED SURFACE FRONT APPROACHES THE WATERS
TUESDAY INTO WEDNESDAY. AS THE SYSTEM APPROACHES, WINDS BECOME
WEST/NORTHWEST AND WILL INCREASE WITH GUSTS UP TO 25 KTS. SEAS
WILL ALSO BUILD TOWARDS 7-10 FT, AS WELL. THERE STILL REMAINS
SOME UNCERTAINTY AS TO THE EXACT TIMING AND OVERALL STRENGTH OF
THE MIDWEEK SYSTEM, SO WILL HOLD OFF ON ISSUING ANY SMALL CRAFT
ADVISORIES AT THIS TIME. -HEC
PQR WATCHES/WARNINGS/ADVISORIES
OR...NONE.
WA...NONE.
PZ...NONE.
WWW.WEATHER.GOV/PORTLAND
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