652
FXUS66 KPQR 021802 AAA
AFDPQR
AREA FORECAST DISCUSSION...UPDATED
NATIONAL WEATHER SERVICE PORTLAND OR
1100 AM PDT FRI OCT 2 2026
UPDATED AVIATION DISCUSSION...
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 18Z SATURDAY
CURRENTLY MOSTLY VFR INLAND AND
A MIX OF IFR TO VFR CONDITIONS ALONG THE COAST. COASTAL TERMINAL
CONDITIONS WILL GRADUALLY IMPROVE BACK TO VFR IN THE AFTERNOON AS
DAYTIME MIXING LIFTS CLOUDS AND DECREASES CLOUD COVER. HOWEVER,
PROBABILISTIC GUIDANCE SUGGESTS A 40-50% CHANCE OF MVFR CIGS THROUGH
THE AFTERNOON AT ALL COAST TERMINALS. AROUND 02-06Z SAT, MARINE
STRATUS WILL RETURN TO THE COASTAL TERMINALS AND INCREASE CHANCES
OF DETERIORATED CONDITIONS. SPECIFICALLY, CHANCES OF LIFR
CONDITIONS WILL INCREASE TO AROUND 30-50%, IFR AROUND 50-60%, AND
MVFR AROUND 60-70% OVERNIGHT BETWEEN 06-16Z SAT. WHILE INLAND
TERMINALS WILL LIKELY STAY VFR THROUGH THE PERIOD, CHANCES OF
DETERIORATED CONDITIONS INCREASE AFTER 11Z SAT, TO AROUND
10-20% FOR LIFR/IFR CONDITIONS AND 20-30% FOR MVFR CONDITIONS.
LIGHT AND VARIABLE WINDS WILL INCREASE OUT OF THE NORTHWEST TO
AROUND 3 TO 6 KT THIS AFTERNOON. WINDS THEN EASE TONIGHT AROUND
06Z SAT AND SHIFT EASTERLY AT TERMINALS NEAR THE CASCADE
FOOTHILLS AND COASTAL GAPS.
KPDX AND APPROACHES...VFR CONDITIONS LIKELY THROUGH THE TAF
PERIOD, WITH A 20-30% CHANCE OF MVFR AND 10-20% CHANCE OF LIFR/IFR
CONDITIONS AFTER 11Z SAT. NORTHWEST WINDS 5 KT OR LESS THROUGHOUT
THE PERIOD. ~12
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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