719
FXUS66 KPQR 041705 AAD
AFDPQR
AREA FORECAST DISCUSSION...UPDATED
NATIONAL WEATHER SERVICE PORTLAND OR
1004 AM PDT SUN OCT 4 2026
UPDATED PQR WATCHES/WARNINGS/ADVISORIES.
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 12Z MONDAY
LATEST TERMINAL OBSERVATIONS
DEPICT WIDESPREAD LIFR CONDITIONS WITHIN FOG ALONG THE NORTH AND
CENTRAL OREGON COAST WHILE INLAND TERMINALS IN THE SOUTHERN
WILLAMETTE VALLEY AND SHELTERED PERIPHERAL VALLEYS ARE BEGINNING
TO SEE FOG DEVELOP, YIELDING RESTRICTED CONDITIONS. DENSE FOG
AND LIFR VIS/CIGS ARE LIKELY (60-80% CHANCE) TO PREVAIL AT
COASTAL TERMINALS UNTIL 17-18Z SUN, WHEN DAYTIME HEATING AND
INCREASING WINDS WILL AID IN MIXING OUT LOW CLOUDS. WHILE VFR
CONDITIONS ARE MOST LIKELY, IF CLOUD COVER REMAINS HIGH ENOUGH,
MVFR CIGS MAY PERSIST THROUGH THE AFTERNOON. NORTHWEST WINDS
INCREASE TO 10-15 KT WITH GUSTS TO 20 KT MOST LIKELY ALONG THE
CENTRAL OREGON COAST INCLUDING AT KONP. WINDS EASE AGAIN AFTER
03Z MON WHILE THE NIGHTLY PUSH OF MARINE CLOUDS INTO THE COAST
IS AGAIN EXPECTED TO PRODUCE RESTRICTED VIS/CIGS. INLAND,
COVERAGE OF FOG OR LOW STRATUS WILL CONTINUE TO INCREASE IN THE
HOURS AROUND SUNRISE. CHANCES FOR RESTRICTED VIS WITHIN FOG
INCREASE TO THE SOUTH ALONG THE WILLAMETTE VALLEY, AS WELL AS TO
THE EAST NEAR THE CASCADE FOOTHILLS; SOUTHERN WILLAMETTE VALLEY
TERMINALS (KEUG, KCVO, K77S) ARE THE MOST LIKELY (40-60% CHANCE)
TO SEE PERSISTENT IFR/LIFR VIS/CIGS WITHIN FOG, WHILE CENTRAL
VALLEY (KSLE, KMMV, KUAO) AND OTHER FOOTHILL TERMINALS (KTTD)
ARE MORE LIKELY TO SEE MVFR VIS AND MIST WITH A LOWER LIKELIHOOD
(25-45% CHANCE) OF IFR/LIFR. ANY LOW CLOUDS OR VIS RESTRICTIONS
ARE EXPECTED TO MIX OUT BY 17-18Z SUN. CALM TO LIGHT WINDS
EARLY THIS MORNING WILL BUILD OUT OF THE NORTH TO NORTHWEST AT
AROUND 5 KT TODAY, THEN EASE AGAIN TONIGHT.
KPDX AND APPROACHES...VFR CONDITIONS FAVORED THROUGHOUT THE
PERIOD, WITH A 15-20% CHANCE OF IFR/LIFR CIGS IF FOG BECOMES
MORE WIDESPREAD IN THE HOURS AROUND SUNRISE, 13-17Z SUN.
OTHERWISE, LARGELY CLEAR SKIES ARE EXPECTED WITH DIURNAL
NORTHWEST WINDS RISING TO AROUND 5 KT THIS AFTERNOON. -36
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:
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X.COM/NWSPORTLAND
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