077
FXUS66 KPQR 050340
AFDPQR
AREA FORECAST DISCUSSION...UPDATED
NATIONAL WEATHER SERVICE PORTLAND OR
840 PM PDT SAT OCT 4 2025
UPDATED AVIATION DISCUSSION...
SYNOPSIS
OFFSHORE FLOW DEVELOPS SUNDAY AND CONTINUES THROUGH AT
LEAST TUESDAY, BRINGING AN EXTENDED PERIOD OF DRY AND BREEZY
CONDITIONS WITH MOSTLY CLEAR SKIES AND HIGH TEMPERATURES IN THE 70S
ACROSS THE LOWLANDS EACH DAY. TEMPERATURES TREND RELATIVELY COOLER
WEDNESDAY ONWARD WITH INCREASING CHANCES FOR RAIN, HOWEVER FORECAST
UNCERTAINTY IS HIGH MID TO LATE WEEK.
DISCUSSION...SATURDAY THROUGH FRIDAY NIGHT
THERE HAS BEEN VERY
LITTLE CHANGE TO THE FORECAST WITH TODAY'S UPDATE. MODELS AND THEIR
ENSEMBLES REMAIN IN GOOD AGREEMENT THAT UPPER LEVEL RIDGING
OVER THE NORTHEAST PACIFIC WILL BUILD OVER THE PACIFIC NORTHWEST
SUNDAY AND MONDAY WHILE A SURFACE THERMAL TROUGH FORMS ALONG
THE OREGON AND SOUTHERN WASHINGTON COAST. THIS PATTERN WILL
RESULT IN THE RETURN OF DRY WEATHER WITH WARMING TEMPERATURES AND
STRENGTHENING OFFSHORE FLOW AT LOW LEVELS. EAST TO NORTHEAST SURFACE
WINDS MAY GUST UP TO 30-40 MPH AT TIMES SUNDAY AFTERNOON THROUGH
EARLY TUESDAY MORNING, WITH THE STRONGEST GUSTS ON EXPOSED
RIDGETOPS IN THE CASCADES AND IN THE WESTERN COLUMBIA RIVER GORGE.
GUSTS UP TO 25 MPH ARE EXPECTED IN THE WILLAMETTE VALLEY AND
CASCADE FOOTHILLS, WITH A NORTHERLY TO NORTHEASTERLY WIND DIRECTION.
NOTE NORTHERLY WINDS WILL BE STRONGEST OVER THE CENTRAL AND SOUTHERN
WILLAMETTE VALLEY, FROM SALEM SOUTHWARD TO EUGENE-SPRINGFIELD.
ALTHOUGH ATMOSPHERIC CONDITIONS WILL BE DRYING OUT, CAUSING DAYTIME
RELATIVE HUMIDITY VALUES TO FALL QUITE SIGNIFICANTLY, THE RECENT
RAINS WILL LIMIT ANY FIRE WEATHER CONCERNS. STILL, THOSE BURNING
SHOULD USE CAUTION SUNDAY MORNING THROUGH TUESDAY MORNING.
ON TUESDAY, THE HIGH PRESSURE AND THERMAL TROUGH WILL BEGIN
BREAKING DOWN LATER IN THE DAY DUE TO AN UPPER LEVEL LOW
PRESSURE SYSTEM APPROACHING THE REGION, ALLOWING WINDS TO BEGIN
SHIFTING ONSHORE AGAIN, THOUGH DRY AND WARM CONDITIONS ARE
EXPECTED TO CONTINUE. THE FORECAST BECOMES MUCH MORE UNCERTAIN
WEDNESDAY ONWARD AS ENSEMBLES ARE SPLIT ON HOW TO RESOLVE THE
AFOREMENTIONED UPPER LEVEL LOW.
WPC'S 12Z CLUSTER ANALYSIS FOR 500 MB HEIGHTS (WHICH UTILIZES THE
GEFS/ENS/GEPS COMBINED) STILL SHOWS HALF OF TOTAL ENSEMBLE SPACE WITH
A CLOSED LOW DEEPENING RIGHT ALONG THE WASHINGTON AND OREGON COAST,
WHILE THE OTHER HALF SUGGESTS THE LOW WILL DEEPEN JUST WEST OF THE
COAST WEDNESDAY THROUGH FRIDAY. THE FIRST SCENARIO WOULD BRING THE
RETURN OF COOLER TEMPERATURES AND SHOWER CHANCES TO NW OREGON AND SW
WASHINGTON, WHEREAS THE LATER SCENARIO WOULD KEEP CONDITIONS DRY AND
ON THE WARMER SIDE. THE NBM 25TH PERCENTILE TO 75TH PERCENTILE
TEMPERATURE SPREAD FOR WEDNESDAY AND THURSDAY RANGES FROM THE LOW 60S
TO MID 70S FOR DAYTIME HIGHS. THE DETERMINISTIC NBM (WHICH OUR
FORECAST REFLECTS) INTRODUCES A 15-35% CHANCE OF RAIN WEDNESDAY
THROUGH FRIDAY, INCREASING TO AROUND 45-60% CHANCE FRIDAY NIGHT.
-59/03
AVIATION
CURRENTLY VFR INLAND AND MVFR CONDITIONS ALONG THE
COAST AS OF 04Z SUNDAY. MARINE STRATUS BEGINS TO RE-DEVELOP ALONG
THE COAST, BRINGING MORE PROMINENT LOW-END MVFR CIGS. CURRENT
GUIDANCE SUGGESTS A 30-50% CHANCE FOR MVFR CONDITIONS FROM NOW
UNTIL 10Z SUNDAY. WITH CURRENT CIGS AROUND FL010 AT THE COAST,
THERE IS MODERATE CONFIDENCE FOR INTERMITTENT IFR CIGS OVERNIGHT.
BY 09-10Z SUNDAY, WINDS WILL SHIFT MORE NORTHEASTERLY AND AID IN
DISSIPATING LOW STRATUS, BRINGING A RETURN OF VFR CONDITIONS TO
THE COAST. AS FOR INLAND, MOST TERMINALS HAVE A 20-40% CHANCE FOR
IFR/MVFR CONDITIONS BETWEEN 09-16Z SUNDAY AS STRATUS DEVELOPS
ALONG THE CASCADE FOOTHILLS. THERE IS RATHER LOW CONFIDENCE ON
WHETHER STRATUS WILL BUILD WESTWARD ENOUGH TO IMPACT VALLEY
TERMINALS OR NOT, BUT GUIDANCE DOES SUGGEST HIGHER CHANCES THIS
OCCURRENCE IN THE SOUTHERN WILLAMETTE VALLEY.
EXPECT LIGHT AND VARIABLE WINDS INLAND AND NORTHEASTERLY WINDS
ALONG THE COAST OVERNIGHT. INLAND WINDS WILL INCREASE AND SHIFT
NORTHEASTERLY BY 18-20Z SUNDAY.
KPDX AND APPROACHES...PRIMARILY VFR CONDITIONS THROUGH THE TAF
PERIOD. THERE IS A 15-30% CHANCE FOR IFR/MVFR CIGS BETWEEN 12-16Z
SUNDAY. LIGHT NORTHWESTERLY WINDS OVERNIGHT, INCREASING AND SHIFTING
NORTHEASTERLY AROUND 18-20Z SUNDAY.
~12
MARINE
TONIGHT INTO SUNDAY, STRONGER HIGH PRESSURE AND
TIGHTENING PRESSURE GRADIENTS DUE TO A THERMAL TROUGH DEVELOPING
ALONG THE COAST WILL SHIFT WINDS NORTHEASTERLY AND ALLOW WINDS TO
INCREASE. A SMALL CRAFT ADVISORY HAS BEEN ISSUED FOR ALL WATERS
SOUTH OF CAPE FALCON FOR A COMBINATION OF NORTH-NORTHEASTERLY WIND
GUSTS UP TO 25 KT AND CHOPPY SEAS, BEGINNING 8 AM FOR THE OUTER
WATERS (BEYOND 10 NM) AND 2 PM FOR THE INNER WATERS (OUT 10 NM).
FOR THE WATERS NORTH OF CAPE FALCON, CHANCES FOR SMALL CRAFT
CONDITIONS REMAIN AROUND 20% OR LESS. WINDS REMAIN NORTHEASTERLY
MONDAY, BUT WILL WEAKEN TO LESS THAN 20 KTS. SEAS AROUND 4-6 FT AT
12-13 SEC THIS EVENING, WITH PERIODS DROPPING TO 8-10 SEC SUNDAY
INTO EARLY NEXT WEEK. -10/03
PQR WATCHES/WARNINGS/ADVISORIES
OR...NONE.
WA...NONE.
PZ...SMALL CRAFT ADVISORY FROM 2 PM TO 11 PM PDT SUNDAY FOR PZZ252-
253.
SMALL CRAFT ADVISORY FROM 8 AM SUNDAY TO 5 AM PDT MONDAY FOR
PZZ272-273.
WWW.WEATHER.GOV/PORTLAND
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