597
FXUS66 KPQR 281826 AAA
AFDPQR
AREA FORECAST DISCUSSION...UPDATED
NATIONAL WEATHER SERVICE PORTLAND OR
1026 AM PST SAT FEB 28 2026
UPDATED AVIATION DISCUSSION.
SYNOPSIS
CHANCES FOR FOG AND FROST HAVE LOWERED THIS MORNING
DUE TO INCREASED CLOUD COVER FROM THE NEXT APPROACHING WEATHER
SYSTEM. THIS SYSTEM WILL MAINLY BE DIRECTED TOWARD NORTHERN
CALIFORNIA BUT RETURN CHANCES FOR PRECIPITATION, MAINLY FROM
SALEM SOUTHWARD. DRY WEATHER RETURNS MONDAY BEFORE ANOTHER
SYSTEM ARRIVES AND BRINGS WIDESPREAD RAIN AND PASS-LEVEL CASCADE
SNOW TUESDAY INTO WEDNESDAY. RAIN AND MOUNTAIN SNOW TRANSITION
TO SHOWERS THURSDAY TO FRIDAY.
DISCUSSION...TODAY THROUGH FRIDAY
SATELLITE IMAGERY AS OF
EARLY SATURDAY MORNING SHOW INCREASING HIGH CLOUDS OVER
NORTHWEST OREGON AND SOUTHWEST WASHINGTON AS A CUT-OFF LOW
PRESSURE SYSTEM APPROACHES THE REGION FROM THE PACIFIC. BECAUSE
OF THE INCREASING CLOUD COVER, FOG AND FROST MAY BE HARDER TO
DEVELOP THIS MORNING. HOWEVER, SOME PLACES ARE STILL CLEAR
AND/OR HAVE THIN HIGH CLOUDS, SO THERE IS STILL LOW TO MODERATE
CONFIDENCE (30-50% CHANCE) FOR FOG DEVELOPMENT THIS MORNING FOR
INTERIOR VALLEYS. TEMPERATURES ARE ALSO DROPPING INTO THE LOW TO
MID 30S THIS MORNING, SO THAT'S STILL COLD ENOUGH TO SUPPORT
FROST DEVELOPMENT OVER GRASSES AND METAL SURFACES. HOWEVER,
LOCATIONS WITH COMPLETE CLOUD COVER MAY END UP WARMER AND THUS
GO FROST/FOG-FREE THIS MORNING. ANY FROST OR FOG THAT DEVELOPS
THIS MORNING SHOULD DISSIPATE BY 10 AM-12 PM.
ENSEMBLE GUIDANCE REMAINS IN EXCELLENT AGREEMENT THAT THE
AFOREMENTIONED LOW PRESSURE SYSTEM WILL SWING THROUGH NORTHERN
CALIFORNIA FROM THE NORTHEAST PACIFIC THIS AFTERNOON THROUGH
EARLY MONDAY MORNING. ENSEMBLE GUIDANCE HAS LOCKED IN THAT THE
LOW TRACK WILL BE FAR ENOUGH NORTH THAT WRAP-AROUND
PRECIPITATION FROM THE SOUTH WILL REACH AT LEAST THE SOUTHERN-
MOST PARTS OF NORTHWEST OREGON SATURDAY AFTERNOON INTO SUNDAY,
MAINLY FROM LINCOLN/POLK/MARION COUNTIES SOUTHWARD. FOR
LOCATIONS NORTH OF THESE COUNTIES, THERE'S ABOUT A 25-40%
CHANCE OF RAIN ALL THE WAY NORTH TO THE COLUMBIA RIVER ON
SUNDAY, INCLUDING THE PORTLAND/VANCOUVER METRO AREA, AND ABOUT A
15-30% CHANCE NORTH OF THIS. NOT MUCH RAIN NOR IMPACTS ARE
EXPECTED FROM THIS SYSTEM. THERE IS STILL SOME UNCERTAINTY WITH
EXACT PRECIPITATION AMOUNTS, BUT GUIDANCE SUGGESTS HIGH
CONFIDENCE (>75% CHANCE) THAT 48 HOUR RAINFALL AMOUNTS ENDING 4
PM MONDAY REMAIN UNDER 0.50 INCH ACROSS INTERIOR LOWLAND
VALLEYS. AN EXCEPTION ARE THE LINN AND LANE COUNTY CASCADES,
WHERE THERE IS A 60-70% CHANCE THAT PRECIPITATION AMOUNTS EXCEED
0.50 INCH DUE TO OROGRAPHIC ENHANCEMENT. ADDITIONALLY, GUIDANCE
CURRENTLY SUGGESTS THAT THE WETTEST SCENARIO (10% CHANCE) IS
AROUND 0.50-0.85 INCH FOR LOCATIONS SOUTH OF TILLAMOOK AND
SALEM. NORTH OF THESE AREAS, THE WETTEST SCENARIO IS BETWEEN
0.20-0.35 INCH. SNOW LEVELS WILL ALSO BE AROUND 6000-7000 FEET,
KEEPING SNOWFALL WELL-ABOVE THE CASCADE PASSES.
TRANSIENT RIDGING RETURNS TO THE PACIFIC NORTHWEST FOR MONDAY,
LEADING TO A RETURN OF COMPLETELY DRY WEATHER AND WARMER
DAYTIME TEMPERATURES IN THE UPPER 50S. THE NEXT WEATHER SYSTEM
APPROACHES THE REGION ON TUESDAY, WITH THE MAJORITY OF ENSEMBLE
MEMBERS (70-80%) SUGGESTING PRECIPITATION BEGINNING ALONG THE
COAST TUESDAY MORNING AND SPREADING INLAND BY THE AFTERNOON.
MEANWHILE, THE OTHER 20-30% OF ENSEMBLE MEMBERS HAVE
PRECIPITATION STARTING LATE MONDAY NIGHT INTO EARLY TUESDAY
MORNING. IN EITHER SCENARIO, DRY WEATHER WILL COME TO AN END BY
TUESDAY EVENING. MORE SUBSTANTIAL RAIN ARRIVES WEDNESDAY, WITH
THE CHANCES FOR 48 HOUR LIQUID PRECIPITATION EXCEEDING 1 INCH
BEING AROUND 10-20% ALONG THE I-5 CORRIDOR FROM COWLITZ TO LANE
COUNTY, 30-50% ALONG THE COAST, AND 60-80% FOR THE COAST RANGE
AND CASCADES.AT THIS POINT, NO WIND IMPACTS ARE EXPECTED WITH
THIS SYSTEM, THOUGH COULD SEE SOME GUSTS UP TO 25 MPH, LOCALLY
UP TO 35-40 MPH OVER THE TERRAIN, AS THE FRONT PASSES ON
WEDNESDAY. SNOW COULD RETURN TO THE CASCADES AS SNOW LEVELS DROP
TO AROUND 3500-4500 FEET ON WEDNESDAY. CHANCES FOR 6+ INCHES OF
SNOW IN A 48 HOUR PERIOD FROM 4 AM TUESDAY THROUGH 4 AM THURSDAY
ARE AROUND 60-80% ALONG THE SANTIAM AND WILLAMETTE PASSES AND
25% FOR HIGHWAY 26 AT GOVERNMENT CAMP, WITH THE MOST SNOW
FALLING LATE TUESDAY INTO WEDNESDAY. THURSDAY TO FRIDAY, RAIN
AND MOUNTAIN SNOW DECREASE AND TRANSITION INTO SHOWERS.
-10/03
AVIATION...MID AND UPPER LEVEL CLOUDS CONTINUE TO INCREASE OVER
THE AREA AS AN UPPER LEVEL LOW TO THE SOUTHWEST SUPPORTS MOIST
SOUTHWEST FLOW. CONDITIONS ARE EXPECTED TO REMAIN LARGELY VFR
THROUGH THE TAF PERIOD WITH ONLY A 10-20% CHANCE OF MVFR
CONDITIONS IN THE SOUTHERN AND CENTRAL WILLAMETTE VALLEY TONIGHT.
CHANCES FOR LIGHT RAIN SHOWERS INCREASE THIS AFTERNOON AS A WEAK
DISTURBANCE WITHIN THE UPPER LEVEL FLOW MOVES IN FROM THE SOUTH.
RAIN CHANCES WILL BE HIGHEST IN THE SOUTHERN AND CENTRAL
WILLAMETTE VALLEY. INLAND WINDS WILL BE NORTHERLY AT AROUND 5 KT
OR LESS WITH EASTERLY OFFSHORE WINDS ALONG THE COAST UP TO 10 KT.
KPDX AND APPROACHES..VFR CONDITIONS EXPECTED TO PREVAIL THROUGH
THE TAF PERIOD WITH INCREASING HIGH CLOUDS. THERE IS A LOW 10-20%
CHANCE FOR RAIN AFTER 12Z ON SUNDAY BUT CONDITIONS ARE EXPECTED TO
REMAIN VFR. -19
MARINE
A NORTHWESTERLY SWELL CONTINUES TODAY WITH SEAS
GRADUALLY SUBSIDING TO 7-8 FT AT 11-12 SEC BY THIS AFTERNOON.
SURFACE HIGH PRESSURE OFFSHORE AND A THERMAL TROUGH ALONG THE
COAST WILL RESULT IN BREEZY NORTHEASTERLY WINDS TODAY WITH GUSTS
UP TO 25 KT, MAINLY FOR THE OUTER WATERS BEYOND 10 NM OFFSHORE.
WEAKER WINDS AROUND 10-15 KT EXPECTED FOR THE INNER WATERS FROM
THE SHORE TO 10 NM. THE SMALL CRAFT ADVISORY REMAINS IN EFFECT
FOR THE OUTER WATERS THROUGH 4 PM THIS AFTERNOON. SUNDAY TO
MONDAY, WINDS FURTHER WEAKEN AND SEAS CONTINUE TO SUBSIDE TO
AROUND 3-5 FT. TUESDAY INTO MID-WEEK, SOUTHERLY WINDS RETURN
AHEAD OF THE NEXT SYSTEM WITH A 40-60% CHANCE FOR FREQUENT AND
WIDESPREAD SMALL CRAFT WIND GUSTS OF 22 KT OR GREATER. THERE IS
ALSO A 10-20% CHANCE THAT SEAS EXCEED 10 FT BY MID TO LATE NEXT
WEEK. -10
PQR WATCHES/WARNINGS/ADVISORIES
OR...NONE.
WA...NONE.
PZ...SMALL CRAFT ADVISORY UNTIL 4 PM PST THIS AFTERNOON FOR
PZZ271>273.
WWW.WEATHER.GOV/PORTLAND
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