455
FXUS66 KPQR 021137
AFDPQR
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE PORTLAND OR
437 AM PDT FRI OCT 2 2026
SYNOPSIS
BUILDING HIGH PRESSURE WITH PERIODS OF OFFSHORE FLOW
WILL SUPPORT WARM AND DRY CONDITIONS THROUGH MUCH OF NEXT WEEK.
EARLY MORNING VALLEY FOG WILL BE LIMITED TO SHELTERED VALLEYS,
ESPECIALLY IN THE COAST RANGE.
DISCUSSION...NOW THROUGH THURSDAY
A WEAK UPPER SHORTWAVE
MOVING INLAND ALONG THE US-CANADA BORDER WILL ACT TO FLATTEN
BROAD UPPER-LEVEL RIDGING CENTERED OVER THE DESERT SOUTHWEST
THROUGH TONIGHT. ANY RAINFALL CHANCES FROM THIS WAVE WILL REMAIN
TO THE NORTH OVER THE OLYMPIC PENINSULA AND PUGET SOUTH, WITH
DRY WEATHER AND ABOVE-NORMAL TEMPERATURES CONTINUING LOCALLY. AS
THE WAVE EXITS EASTWARD THROUGH THIS AFTERNOON, PASSING HIGH
CLOUDS WILL CLEAR, LEADING TO MOSTLY SUNNY SKIES INLAND. THE
COASTAL MARINE LAYER WILL BE MORE PERSISTENT, LEAVING THOSE
ALONG THE IMMEDIATE COAST AND NEAR THE COLUMBIA RIVER AND
WILLAPA BAY ESTUARIES LARGELY OVERCAST AND SLIGHTLY COOLER.
TONIGHT THROUGH THE WEEKEND, THE UPPER RIDGE AMPLIFIES OVER MUCH
OF THE WEST COAST IN THE WAKE OF THE DEPARTING SHORTWAVE, BEFORE
SHIFTING INLAND BY EARLY NEXT WEEK. MID-LEVEL TEMPERATURES
RISING TO NEAR 20C WILL PUSH SURFACE TEMPERATURES WELL ABOVE
SEASONAL NORMS THROUGH THE WEEKEND, LIKELY PEAKING SUNDAY
AFTERNOON IN THE LOW TO MID 80S WITHIN INLAND VALLEYS. WHILE
MOST DAILY TEMPERATURES RECORDS APPEAR TO BE OUT OF REACH, A
RECORD VALUE COULD BE TIED OR BROKEN AT PORTLAND INT'L (84F SET
IN 1952).
THERMAL TROUGHING DEVELOPING ALONG THE COAST IS EXPECTED TO
REMAIN FAIRLY WEAK, WITH A MEAN PRESSURE GRADIENT BETWEEN
PORTLAND AND THE DALLES OF -2 MB AND ALMOST CERTAINLY REMAINING
LESS THAN -4 MB PER SHORT-RANGE ENSEMBLES. THIS MAGNITUDE OF
GRADIENT FAVORS A DIURNALLY VARYING WIND WITH OFFSHORE
(EASTERLY) FLOW DEVELOPING NIGHTLY OVER THE CASCADES AND THEIR
WESTERN SLOPES, AS WELL AS POSSIBLY IN THE HIGHEST REACHES OF
THE COAST RANGE, BEFORE DAYTIME MIXING SEES WINDS DECREASE OVER
TERRAIN AND INCREASE OUT OF THE NORTH WITHIN INLAND VALLEYS.
OFFSHORE WINDS LOOK TO PEAK SATURDAY NIGHT INTO SUNDAY MORNING,
WITH GUSTS OF 20-35 MPH IN THE CASCADES AND FOOTHILLS, HIGHEST
IN TYPICAL AREAS WITHIN AND NEAR THE COLUMBIA RIVER GORGE. THIS
PATTERN WILL ADDITIONALLY PROMOTE NIGHTLY AREAS OF VALLEY FOG
THANKS TO LIGHT WINDS AWAY FROM THE CASCADES, DRY MID AND UPPER
LEVELS LIMITING CLOUD COVER, AND ROBUST NOCTURNAL INVERSIONS
DURING INCREASINGLY LONG NIGHTS. COAST RANGE VALLEYS ARE THE
MOST LIKELY TO SEE AREAS OF LIMITED VISIBILITY, BUT THE COVERAGE
OF FOG ACROSS THE REGION AND POSSIBLY INCLUDING THE WILLAMETTE
VALLEY REMAINS UNCERTAIN.
BY EARLY NEXT WEEK, THE UPPER-LEVEL RIDGE LOOKS TO SHIFT INLAND
AND BROADEN, YIELDING COOLER BUT STILL ABOVE-NORMAL TEMPERATURES
LOCALLY. LONG-RANGE ENSEMBLE GUIDANCE SUPPORTS HIGH CONFIDENCE
IN CONTINUED DRY CONDITIONS THROUGH NEARLY THE ENTIRE WORKWEEK,
WITH THE NEXT WIDESPREAD CHANCES FOR RAIN HOLDING OFF UNTIL NEXT
FRIDAY AT THE EARLIEST. -36
AVIATION...THROUGH 12Z SATURDAY
RESTRICTED FLYING CONDITIONS
EXPECTED AT COASTAL TERMINALS WHILE VFR CONDITIONS FAVORED
INLAND THROUGHOUT THE PERIOD. LATEST SATELLITE IMAGERY DEPICTS
LOW MARINE STRATUS ALONG THE IMMEDIATE CENTRAL OR COAST AND
PUSHING INLAND OVER THE NORTH OR AND SOUTH WA COASTS. IFR/LIFR
CIGS ALREADY OBSERVED AT COASTAL TERMINALS ARE VERY LIKELY,
70-80% CHANCE, TO CONTINUE THROUGH AT LEAST FRIDAY MORNING,
BEFORE INCREASED DAYTIME MIXING FAVORS LIFTING CLOUD BASES AND
DECREASED SKY COVER BY 19-22Z FRI. MVFR CONDITIONS REMAIN
FAVORED THROUGH THE AFTERNOON, ESPECIALLY NORTH OF KTMK,
ALTHOUGH THERE ARE NEARLY 50% CHANCES BKN CIGS REMAIN IN PLACE
ALONG THE CENTRAL OR COAST AS WELL. MARINE STRATUS AGAIN FRIDAY
NIGHT WILL RETURN WIDESPREAD IFR/LIFR CONDITIONS ALONG THE COAST
AFTER 03-06Z SAT.
INLAND, LATEST SATELLITE DEPICTS SKIES TRENDING CLEARER AS HIGH
CLOUDS STEADILY EXIT TO THE SOUTH AND EAST. THERE IS HIGH
CONFIDENCE IN CONTINUED VFR CONDITIONS THROUGH MUCH OF THE
PERIOD, WITH LOW BUT INCREASING CHANCES LATE, 10-20% AFTER 09Z
SAT, FOR MVFR CIGS BENEATH LOW STRATUS ALONG THE CASCADE
FOOTHILLS AND IN THE NORTHERN WILLAMETTE VALLEY INCLUDING AT
PORTLAND-AREA TERMINALS.
CALM TO LIGHT AND VARIABLE WINDS EARLY THIS MORNING WILL
INCREASE OUT OF THE NORTHWEST TO AROUND 5 KT THIS AFTERNOON.
WINDS EASE AGAIN TONIGHT AFTER 03-06Z SAT BECOMING CALM FOR MOST
BUT WITH LIGHT EASTERLY FLOW FAVORED AT TERMINALS NEAR THE
CASCADE FOOTHILLS AND GAPS IN COASTAL TERRAIN.
KPDX AND APPROACHES...HIGH CONFIDENCE IN VFR CONDITIONS THROUGH
AT LEAST 06Z SAT BENEATH LARGELY CLEAR SKIES. LOW CHANCES,
NEAR 10%, FOR LOW STRATUS AND MVFR CIGS EARLY SATURDAY MORNING.
NORTHWEST WINDS 5 KT OR LESS THROUGHOUT THE PERIOD. -36
MARINE
A WEAK SYSTEM MOVING INTO WESTERN WASHINGTON WILL SEE
WEST TO SOUTHWEST WINDS NORTH OF CASCADE HEAD TODAY, VEERING OUT
OF THE NORTH BY TONIGHT. NORTH WINDS OTHERWISE REMAIN IN PLACE
THROUGH THE NEXT WEEK AS HIGH PRESSURE STRENGTHENS. DIURNAL PEAK
GUSTS SATURDAY AND SUNDAY AFTERNOON MAY EXCEED 20 KT, MOST
LIKELY WITHIN 20 NM OF THE COAST. SEAS CONTINUE AT 3-6 FT
THROUGH MUCH OF THE NEXT WEEK WITH A PERSISTENT NORTHWESTERLY
SWELL AT 8-9 SECONDS THROUGH SUNDAY, LENGTHENING TO 10-12
SECONDS EARLY NEXT WEEK. -36
PQR WATCHES/WARNINGS/ADVISORIES
OR...NONE.
WA...NONE.
PZ...NONE.
WWW.WEATHER.GOV/PORTLAND
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