323
FXUS66 KPQR 041808 AAD
AFDPQR
AREA FORECAST DISCUSSION...UPDATED
NATIONAL WEATHER SERVICE PORTLAND OR
1105 AM PDT SUN OCT 4 2026
UPDATED AVIATION DISCUSSION...
SYNOPSIS
UNSEASONABLY WARM AND DRY CONDITIONS CONTINUE
THROUGH MUCH OF THE WORKWEEK WITH PERIODS OF OFFSHORE FLOW AND
EARLY MORNING VALLEY AND COASTAL FOG. A TROUGH MOVING INTO THE
PACIFIC NORTHWEST WILL BRING COOLER TEMPERATURES AND CHANCES FOR
RAIN FRIDAY INTO NEXT WEEKEND.
SHORT TERM...NOW THROUGH TUESDAY NIGHT
UPPER-LEVEL HEIGHTS
OVERHEAD PEAK TODAY BEFORE RIDGING CENTERED OVER THE DESERT
SOUTHWEST BEGINS TO SHIFT EASTWARD AND DE-AMPLIFY. A THERMAL
TROUGH ALONG THE COAST WILL ALSO SHIFT INLAND, WITH GOOD
AGREEMENT AMONG SHORT-RANGE ENSEMBLES THAT THE PRESSURE GRADIENT
BETWEEN PORTLAND AND THE DALLES OF AROUND -2 MB WILL WEAKEN
THROUGH THIS AFTERNOON, PUTTING AN END TO OVERNIGHT OFFSHORE
WINDS IN THE CASCADES AND FOOTHILLS. EAST WINDS GUSTING TO 20-30
MPH IN THE WESTERN COLUMBIA GORGE AND NEARBY TERRAIN WILL
THEREFORE EASE BY MIDDAY.
RIDGING ALOFT WILL ALSO PROMOTE AREAS OF OVERNIGHT AND EARLY
MORNING FOG IN SHELTERED COAST RANGE VALLEYS AND THE SOUTHERN
WILLAMETTE VALLEY THANKS TO LIGHT WINDS AWAY FROM THE CASCADES,
CLEAR SKIES, ROBUST NOCTURNAL INVERSIONS DURING INCREASINGLY
LONG NIGHTS, AND BROAD SUBSIDENCE WHICH ACTS TO COMPRESS THE
SURFACE LAYER. A DENSE FOG ADVISORY HAS BEEN ISSUED FOR THE
NORTH AND CENTRAL OREGON COAST UNTIL 10 AM PDT THIS MORNING,
WHERE OBSERVATIONS AND CAMERAS SHOW WIDESPREAD FOG AND LIMITED
VISIBILITY. TRAVELERS SHOULD TAKE CAUTION THIS MORNING; DRIVERS
SHOULD SLOW DOWN AND LEAVE EXTRA FOLLOWING DISTANCE, WHILE
PEDESTRIANS AND CYCLISTS SHOULD WEAR BRIGHT COLORS AND CARRY
LIGHTS TO INCREASE VISIBILITY TO PASSING CARS. AS RIDGING ALOFT
WEAKENS AND SOME HIGH CLOUD COVER STREAMS OVERHEAD MONDAY AND
TUESDAY NIGHTS, CHANCES FOR DENSE FOG WILL GENERALLY DECREASE,
BUT THE AREAS WHICH MAY SEE RESTRICTED VISIBILITY FROM PATCHY
FOG ACTUALLY BROADENS TO INCLUDE MUCH OF THE I-5 CORRIDOR;
COMMUTERS SHOULD CONSIDER ALLOWING EXTRA TIME FOR THEIR MORNING
TRIP TO WORK.
UPPER-LEVEL RIDGING WILL ALSO CONTINUE TO SUPPORT ABNORMALLY
WARM TEMPERATURES THROUGH THE PERIOD. MID-LEVEL TEMPERATURES
PEAK TODAY NEAR 20C, TRANSLATING TO AFTERNOON HIGHS IN THE LOW
TO MID 80S IN THE WILLAMETTE VALLEY AND ALONG THE I-84 CORRIDOR.
DAILY RECORD HIGHS ARE LIKELY OUT OF REACH FOR MOST SITES,
HOWEVER A RELATIVELY LOW RECORD OF 84F AT PORTLAND INT'L SET IN
1952 MAY BE IN JEOPARDY, WITH A 40% CHANCE OF TYING OR BREAKING
THE RECORD VALUE. DESPITE THESE WARM TEMPERATURES, THE MAJORITY
OF THE REGION WILL EXPERIENCE ONLY MINOR HEATRISK, WITH MODERATE
HEATRISK MOST LIKELY LIMITED TO CASCADE VALLEYS WHERE OFFSHORE
FLOW WILL SUPPORT WARMER LOW TEMPERATURES EARLY THIS MORNING.
OTHERWISE, THE PORTLAND-VANCOUVER METRO AREA MAINTAINS A 30-45%
CHANCE OF REACHING MODERATE HEATRISK, CORRESPONDING TO THE
CHANCES FOR SUNDAY MORNING LOWS TO FALL ONLY INTO THE UPPER 50S.
INLAND TEMPERATURES ARE EXPECTED TO COOL A FEW DEGREES MONDAY
AND TUESDAY AFTERNOONS AS ONSHORE FLOW RETURNS AND THE UPPER-
LEVEL RIDGE WEAKENS, BUT THESE TEMPERATURES WILL NONETHELESS
REMAIN SOME 5-10 DEGREES ABOVE NORMAL FOR EARLY OCTOBER. -36
LONG TERM...WEDNESDAY THROUGH SATURDAY
THE UPPER-LEVEL
PATTERN LOOKS TO AMPLIFY AGAIN THROUGH THE MIDDLE OF THE WEEK,
LEADING TO A SLIGHT WARMING TREND AS INLAND TEMPERATURES REMAIN
AROUND 10 DEGREES ABOVE NORMAL WEDNESDAY AND THURSDAY. DRY
WEATHER ALSO CONTINUES, WHILE THE RESURGENT RIDGE AND WARM
TEMPERATURES WILL AGAIN ALLOW FOR THE DEVELOPMENT OF A COASTAL
THERMAL TROUGH, NOCTURNAL OFFSHORE WINDS IN THE CASCADES AND
FOOTHILLS, AND EARLY MORNING VALLEY FOG IN THE COAST RANGE AND
WILLAMETTE VALLEY.
THERE IS INCREASING CONSENSUS AMONG LONG-RANGE ENSEMBLE MEMBERS
IN THE EVOLUTION OF AN UPPER-LEVEL TROUGH ARRIVING FRIDAY INTO
NEXT WEEKEND, BRINGING A RETURN TO MORE SEASONABLE TEMPERATURES
AND POTENTIAL RAINFALL. WHILE THERE IS STILL UNCERTAINTY IN
TIMING AND AMOUNTS, RAIN CHANCES PEAK FRIDAY AFTERNOON INTO
FRIDAY NIGHT, HIGHEST IN THE CASCADES AND ALONG THE COAST FROM
TILLAMOOK COUNTY NORTHWARD. -36
AVIATION...THROUGH 18Z MONDAY
CURRENTLY LIFR/IFR STRATUS AT
COASTAL TERMINALS AND MOSTLY VFR CONDITIONS INLAND (THE EXCEPTION
BEING LIFR AT KEUG). EXPECT CONDITIONS AT TERMINALS WITH
DETERIORATED CONDITIONS TO IMPROVE BACK TO VFR BY 19-20Z SUN, WITH
THE EXCEPTION OF KONP POSSIBLY STAYING IFR THROUGH THE AFTERNOON. BY
03-06Z MON, DETERIORATED CONDITIONS WILL LIKELY RETURN TO COASTAL
TERMINALS, TO THE EAST NEAR THE CASCADE FOOTHILLS, AND TO THE
CENTRAL/SOUTHERN WILLAMETTE VALLEY. PROBABILISTIC GUIDANCE SUGGESTS
A 25-50% CHANCE OF LIFR CONDITIONS AT COASTAL TERMINALS, HIGHEST AT
KONP, AND A 20-30% CHANCE OF LIFR CONDITIONS AT KSLE AND KEUG. AS
FOR OTHER INLAND TERMINALS, THERE IS A 10-20% CHANCE OF LIFR
CONDITIONS AFTER 12Z MON.
CALM TO LIGHT WINDS EARLY THIS MORNING WILL BUILD OUT OF THE NORTH
TO NORTHWEST AT AROUND 5 KT TODAY, THEN EASE AGAIN AROUND 03Z MON.
WINDS OF 8-12 KT WITH GUSTS UP TO 20 KT ARE POSSIBLE THIS AFTERNOON
AT KONP.
KPDX AND APPROACHES...VFR CONDITIONS THROUGHOUT THE PERIOD, WITH A
15-20% CHANCE OF IFR/LIFR CONDITIONS IF FOG BECOMES MORE WIDESPREAD
AROUND 12-17Z SUN. DIURNAL NORTHWEST WINDS RISING TO AROUND 5 KT
THIS AFTERNOON. ~12
MARINE
PERSISTENT HIGH PRESSURE OFFSHORE WILL MAINTAIN
NORTHERLY WINDS THROUGH THE WEEK, WITH SPEEDS REACHING DIURNAL PEAKS
EACH AFTERNOON. CHANCES FOR PEAK WIND GUSTS OF 20-25 KT GENERALLY
INCREASE DAILY THROUGH WEDNESDAY, THOUGH THE DURATION AND COVERAGE
STRONGER GUSTS MAY NOT BE SUFFICIENT TO SUPPORT SMALL CRAFT
ADVISORIES EACH DAY. STRENGTHENING NORTHERLY FLOW WILL SEE LARGELY
WIND-DRIVEN SEAS CONTINUE AT 4-6 FT THROUGH MUCH OF THE WEEK, WITH A
MODEST WEST-NORTHWEST SWELL AT 8-9 SECONDS LENGTHENING TO 10-12
SECONDS EARLY IN THE WORKWEEK.
HIGH PRESSURE ALOFT THIS WEEKEND WILL ALSO SUPPORT AREAS OF DENSE
FOG DEVELOPING NIGHTLY AS CLOUD BASES ARE COMPRESSED DOWN TO THE
SURFACE. THE CURRENT DENSE FOG ADVISORY WHICH REMAINS IN EFFECT
THROUGH NOON PDT SUNDAY FOR VISIBILITIES OF 1 NM OR LESS HAS BEEN
EXPANDED TO COVER ALL OF THE WATERS.
MORE ACTIVE MARINE CONDITIONS ARE LIKELY IN THE LATTER HALF OF THE
WEEK AS TROUGHING OVER THE GULF OF ALASKA GENERATES A BUILDING
NORTHWEST SWELL AND CHANCES FOR RAIN RETURN TO THE REGION FRIDAY
INTO NEXT WEEKEND. A LONGER PERIOD NORTHWESTERLY SWELL MAY ALSO
BRING A MODERATE SNEAKER WAVE THREAT. -36/10
PQR WATCHES/WARNINGS/ADVISORIES
OR...NONE.
WA...NONE.
PZ...DENSE FOG ADVISORY UNTIL NOON PDT TODAY FOR PZZ210-251>253-
271>273.
WWW.WEATHER.GOV/PORTLAND
INTERACT WITH US VIA SOCIAL MEDIA:
WWW.FACEBOOK.COM/NWSPORTLAND
X.COM/NWSPORTLAND
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