698
FXUS66 KPQR 182350
AFDPQR
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE PORTLAND OR
450 PM PDT SUN OCT 18 2026
SYNOPSIS
LARGELY DRY WEATHER EXPECTED THROUGH MIDWEEK WITH
TEMPERATURES REMAINING NEAR TO ABOVE NORMAL FOR MID-OCTOBER.
CHANCES FOR WETTER AND COOLER WEATHER RETURN LATE IN THE WEEK.
DISCUSSION...NOW THROUGH SUNDAY
TRANQUIL EARLY FALL WEATHER
WILL CONTINUE INTO THE WORKWEEK DESPITE AN UPPER-LEVEL TROUGH
APPROACHING THE COAST THROUGH TOMORROW. THERE REMAINS GOOD
CONSENSUS THAT THE TROUGH WILL ELONGATE AND PINCH OFF INTO A
CLOSED LOW WELL OFFSHORE WHICH WILL ULTIMATELY DRIFT SOUTH AND
AWAY FROM THE PACIFIC NORTHWEST. LOCALLY, CLOUD COVER WILL
INCREASE THIS AFTERNOON THROUGH TONIGHT AS THE SYSTEM MAKES ITS
CLOSEST APPROACH, WHICH WILL STYMIE RADIATIONAL COOLING AND
MITIGATE FROST CONCERNS FOR MOST. THE TYPICAL COLDEST SPOTS IN
THE FAR UPPER HOOD RIVER VALLEY NEAR DEE AND PARKDALE, NORTH
OREGON COAST RANGE VALLEYS AROUND VERNONIA AND GRAND RONDE, AND
PERIPHERAL VALLEYS AROUND THE SOUTHERN WILLAMETTE VALLEY (ALONG
THE MIDDLE AND COAST FORK WILLAMETTE RIVER AND THE MCKENZIE
RIVER) MAY SEE SOME AREAS AT RISK OF DEVELOPING FROST, AND THOSE
WITH AGRICULTURAL INTERESTS OR SENSITIVE OUTDOOR PLANTS SHOULD
TAKE PRECAUTIONARY ACTIONS TO PREVENT DAMAGE. CHANCES FOR RAIN
FROM THIS SYSTEM TONIGHT THROUGH MONDAY ARE MINIMAL, WITH THE
CASCADE FOOTHILLS AND COAST RANGE SOUTH OF US-20 HAVING A 15-25%
CHANCE OF LIGHT RAIN OR DRIZZLE ACCUMULATING TO 0.01 INCHES.
OTHERWISE, DRY WEATHER IS EXPECTED WITH NEAR-NORMAL AFTERNOON
HIGH TEMPERATURES IN THE 50S ALONG THE COAST AND IN TERRAIN, AND
60S IN INLAND VALLEYS.
AS THE CLOSED LOW DRIFTS SOUTH INTO CALIFORNIA, LIGHT OFFSHORE
FLOW ON ITS NORTHERN FLANK WILL HELP CLEAR SKIES AND PUSH
TEMPERATURES SOME 10 DEGREES ABOVE NORMAL TUESDAY AND WEDNESDAY,
WHEN AFTERNOON HIGHS SHOULD REACH THE 60S ALONG THE COAST AND IN
TERRAIN, AND THE LOW TO MID 70S IN INLAND VALLEYS. DESPITE WARM
AFTERNOONS, CLEAR SKIES OVERNIGHT MAY ALLOW FOR NIGHTLY AREAS
OF FROST WITHIN INLAND VALLEYS; THOSE WITH AGRICULTURAL
INTERESTS OR SENSITIVE OUTDOOR PLANTS SHOULD CONTINUE TO
MONITOR THE FORECAST FOR POTENTIAL FROST ADVISORIES.
BY THE LATTER HALF OF THE WORKWEEK, THE PATTERN LOOKS TO BECOME
MORE ACTIVE, FAVORING A RETURN TO COOLER AND WETTER WEATHER. AN
UPPER-LEVEL TROUGH LOOKS TRACK INLAND IN CONJUNCTION WITH THE
AFOREMENTIONED CLOSED LOW IN CALIFORNIA, BRINGING CHANCES FOR
LIGHT RAIN FROM THURSDAY THROUGH EARLY FRIDAY, ALTHOUGH
POTENTIAL RAINFALL AMOUNTS APPEAR VERY LOW. THERE IS INCREASING
CONSENSUS THAT A MORE POTENT SYSTEM MAY AFFECT THE PACIFIC
NORTHWEST SOMETIME THIS WEEKEND, POSSIBLY THE FIRST ATMOSPHERIC
RIVER OF THE SEASON. THERE ARE ELEVATED CHANCES FOR MORE
SUBSTANTIAL RAINFALL AMOUNTS, BUT UNCERTAINTY REMAINS HIGH AT
THIS LONGER LEAD TIME. -36
AVIATION...THROUGH 00Z TUESDAY
A LOW PRESSURE SYSTEM DROPPING
SOUTHWARD OFF THE COAST WILL SPREAD PLENTY OF MID AND HIGH LEVEL
CLOUDS ACROSS THE REGION THROUGH 00Z TUESDAY. HOWEVER, THIS WILL
RESULT IN LIGHT WINDS AND PREDOMINANTLY VFR CONDITIONS ACROSS THE
AREA THROUGH THIS TIME PERIOD. IT SHOULD BE NOTED THAT AROUND 40% OF
OUR HIGH RESOLUTION WEATHER MODELS SUGGEST A MIXTURE OF IFR AND MVFR
STRATUS WILL DEVELOP ALONG THE CENTRAL COAST OF OREGON AROUND 06-08Z
MONDAY BEFORE SPREADING EASTWARD INTO THE SOUTHERN WILLAMETTE VALLEY
TOWARDS 12Z MONDAY. CONFIDENCE IN THIS SCENARIO IS NOT HIGH, BUT IT
DOES SEEM MODESTLY PLAUSIBLE. WILL KEEP TAFS VFR FOR NOW LATER
TONIGHT INTO MONDAY MORNING, BUT WILL BE MONITORING TRENDS AND
ADDITIONAL GUIDANCE AND MAY MAKE A FEW AMENDMENTS LATER ON THIS
EVENING.
KPDX AND APPROACHES...A LOW PRESSURE SYSTEM DROPPING SOUTHWARD OFF
THE COAST WILL SPREAD PLENTY OF MID AND HIGH LEVEL CLOUDS ACROSS THE
REGION THROUGH 00Z TUESDAY. EXPECT PREDOMINANTLY VFR CONDITIONS AND
LIGHT WINDS THROUGH THIS TIME PERIOD. THERE IS A 20% CHANCE FOR MVFR
OR HIGH END IFR CONDITIONS TO DEVELOP IN THE 12-18Z MONDAY
TIMEFRAME, BUT SUSPECT MID AND HIGH CLOUDS WILL MINIMIZE FOG AND LOW
CLOUD CHANCES IN THE VICINITY OF KPDX.
MARINE
A CONTINUED WEST-NORTHWESTERLY SWELL AND WEAKENING
NORTHERLY WINDS WILL SEE SEAS OF 8-9 FT TODAY EASE TO 6-7 FT BY
EARLY MONDAY MORNING. A SYSTEM DROPPING SOUTHWARD WELL OFFSHORE
WILL GENERATE A STRONGER WESTERLY SWELL ARRIVING LATE MONDAY
WHICH WILL PUSH SEAS TO 8-11 FT, HIGHEST BEYOND 10 NM AND SOUTH
OF CAPE FALCON, WHERE SMALL CRAFT ADVISORIES HAVE BEEN HOISTED
FROM 5 PM PDT MONDAY THROUGH 5 AM PDT TUESDAY BEFORE SEAS EASE
BELOW 9-10 FT. STRENGTHENING NORTHERLY FLOW IN THE WAKE OF THIS
PASSING SYSTEM MAY SUPPORT GUSTS PEAKING AT 20-25 KT ON TUESDAY,
POTENTIALLY REQUIRING AN EXTENSION OR EXPANSION OF THE ADVISORY
IF CONFIDENCE IN THE COVERAGE AND DURATION OF STRONGER WINDS
INCREASES. CONDITIONS OTHERWISE IMPROVE MIDWEEK AS WINDS AND
SEAS EASE, BUT A MORE ACTIVE PATTERN LOOKS TO RETURN LATE IN THE
WEEK. INCREASING NORTHWESTERLY WINDS AND A NORTHWESTERLY SWELL
COULD PUSH SEAS CLOSE TO 10 FT AGAIN FROM THURSDAY INTO FRIDAY,
AND A MORE POTENT WEATHER SYSTEM NEXT WEEKEND WILL ALSO SEE
INCREASED CHANCES FOR SEAS ABOVE 10 FT AND GUSTY, POTENTIALLY
GALE-FORCE WINDS. -36
PQR WATCHES/WARNINGS/ADVISORIES
OR...NONE.
WA...NONE.
PZ...SMALL CRAFT ADVISORY FROM 5 PM MONDAY TO 5 AM PDT TUESDAY FOR
PZZ272-273.
WWW.WEATHER.GOV/PORTLAND
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