157
FXUS66 KPQR 092340
AFDPQR
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE PORTLAND OR
440 PM PDT WED SEP 9 2026
UPDATED AVIATION DISCUSSION.
SYNOPSIS
TEMPERATURES WILL GRADUALLY COOL EACH DAY THURSDAY
THROUGH THE WEEKEND AS ONSHORE FLOW STRENGTHENS AHEAD OF A LOW
PRESSURE SYSTEM SET TO BRING WIDESPREAD RAIN TO THE AREA ON
SATURDAY. SHOWERS DISSIPATE ON SUNDAY, WITH DRY AND MILD
CONDITIONS EXPECTED EARLY NEXT WEEK.
SHORT TERM...NOW THROUGH SATURDAY NIGHT
THE SHORT TERM
FORECAST IS HIGHLIGHTED BY A GRADUAL COOLING TREND WITH
WIDESPREAD RAIN ARRIVING ON SATURDAY. UP UNTIL SATURDAY,
CONFIDENCE IS HIGH CONDITIONS WILL STAY DRY. ALTHOUGH THURSDAY
WILL BE RELATIVELY COOLER COMPARED TO WEDNESDAY, TEMPERATURES
WILL STILL BE SEASONABLY WARM IN THE AFTERNOON WITH HIGHS
RANGING BETWEEN 75-80 DEGREES FOR MOST INLAND VALLEY LOCATIONS,
EXCEPT 65-70 DEGREES AT THE COAST. THE HREF ENSEMBLE MEAN FOR
CLOUD COVER SUGGESTS A BAND OF MID TO HIGH LEVEL CLOUDS WILL
MOVE SOUTHWARD OVER SOUTHWEST WASHINGTON AND NORTHWEST OREGON
DURING THE LATE MORNING AND EARLY AFTERNOON HOURS. MEANWHILE,
LANE COUNTY SHOULD REMAIN MOSTLY SUNNY THROUGH THE DAY, WHICH
WILL RESULT IN SLIGHTLY WARMER TEMPERATURES IN THIS AREA
COMPARED TO LOCATIONS TO THE NORTH OF LANE COUNTY. SKIES ON
FRIDAY LOOK TO BE MOSTLY CLOUDY TO THE NORTH OF A LINE EXTENDING
FROM NEWPORT TO SALEM TO MOLALLA AND PARTLY CLOUDY TO MOSTLY
CLEAR SOUTH OF THAT LINE. TEMPERATURES ALOFT WILL BE SEVERAL
DEGREES COOLER, WITH HIGHS RUNNING 5-10 DEGREES BELOW AVERAGE
FOR THIS TIME OF YEAR.
CLOUD COVER WILL INCREASE ACROSS ALL OF SOUTHWEST WASHINGTON AND
NORTHWEST OREGON FRIDAY NIGHT INTO SATURDAY AHEAD OF A LOW
PRESSURE SYSTEM THAT WILL BRING WIDESPREAD RAIN TO THE AREA
BEGINNING SOMETIME BETWEEN EARLY SATURDAY MORNING AND LATE
SATURDAY AFTERNOON. DESPITE THE MODEL TIMING DIFFERENCES, AROUND
95% OF MODEL ENSEMBLE GUIDANCE FROM THE GEFS/GEPS/ENS SUGGESTS
MEASURABLE RAIN WILL OCCUR WITH THIS SYSTEM. AS SUCH, EXPECT A
COOL AND WET DAY ON SATURDAY WITH TEMPERATURES IN THE 60S AND
TOTAL RAIN AMOUNTS RANGING BETWEEN 0.2-0.5 INCHES FOR MOST
LOCATIONS, HIGHEST IN THE CASCADES IN COAST RANGE. NOTE THIS IS
NOT ENOUGH RAIN TO RESULT IN FLOODING IMPACTS. SOME RAIN SHOWERS
WILL LINGER INTO SATURDAY NIGHT, ESPECIALLY IN THE CASCADES AND
FOOTHILLS. NOTE THE NBM ALSO SUGGESTS THERE IS A 15-25% CHANCE
OF THUNDERSTORMS SATURDAY AFTERNOON, AND THE OVERALL SET-UP
SUGGESTS STRONGER CONVECTIVE CELLS COULD PRODUCE A COLD CORE
FUNNEL CLOUD. ROTATION WITH COLD CORE FUNNEL CLOUDS RARELY
REACHES THE GROUND OR CAUSES IMPACTS, BUT IT IS NOT IMPOSSIBLE.
NOTE THESE ARE NON-MESOCYCLONIC IN NATURE, AND CAN FORM WITHOUT
STRONG DEEP-LAYER WIND SHEAR IN PLACE. -23
LONG TERM...SUNDAY THROUGH TUESDAY
THE LONG TERM FORECAST IS
HIGHLIGHTED BY MAINLY DRY CONDITIONS AND THE CONTINUATION OF
BELOW AVERAGE TEMPERATURES, ALBEIT A BIT WARMER THAN WHAT IS
EXPECTED ON SATURDAY. THE VAST MAJORITY (>90%) OF ENSEMBLE
GUIDANCE SUGGESTS THE UPPER LEVEL LOW OVER THE AREA ON SATURDAY
WILL PUSH EASTWARD AND MOVE TOWARDS THE NORTHERN PLAINS SUNDAY
INTO EARLY NEXT WEEK. A WEAKER SECONDARY TROUGH ON THE BACKSIDE
OF THIS LOW LOOKS TO REMAIN OVER OREGON AND WASHINGTON, HOWEVER
IT IS UNCLEAR HOW DEEP THIS SECONDARY TROUGH WILL BE. TOTAL
MODEL SPREAD FOR TEMPERATURES ON THE NBM 1D VIEWER RANGES IS
FAIRLY LOW ON SUNDAY, WITH HIGHS MOST LIKELY RANGING BETWEEN THE
MID 60S AND LOWER 70S (80% CHANCE). ON MONDAY, SPREAD RANGES
FROM THE UPPER 60S TO AROUND 80 DEGREES, WITH LOW TO MID 70S
BEING THE MOST LIKELY OUTCOME. SPREAD INCREASES A BIT ON
TUESDAY, AS HIGHS COULD RANGE ANYWHERE FROM THE MID 60S TO THE
MID 80S. OVERALL, THERE ARE NO SIGNS OF ANY HIGH IMPACT WEATHER
ON THE HORIZON. -23
AVIATION...THROUGH 00Z FRIDAY
WIDESPREAD VFR CONDITIONS
EXPECTED AT INLAND TERMINALS THROUGH THIS PERIOD WHILE LOW CLOUD
COVERAGE WILL FAVOR IFR/LIFR CIGS ALONG THE COAST. REINVIGORATED
MOIST ONSHORE FLOW WILL SEE MARINE STRATUS COVERAGE EXPAND FROM
NORTH TO SOUTH BY 03-09Z THU, WITH 50-70% CHANCES FOR LIFR CIGS
AFTER 09Z THU. CHANCES FOR IFR VIS ARE LOWER, 20-30%, AFTER 09Z
THU. LOW CLOUD COVERAGE INLAND IS EXPECTED TO REMAIN LOW AND
MVFR CIGS ARE VERY UNLIKELY, 10% OR LOWER CHANCES. ANY LOW
CLOUDS WILL TEND TO CLEAR AFTER 18Z THU, WITH VFR CONDITIONS
AGAIN FAVORED ACROSS THE AIRSPACE BY 21Z THU BENEATH INCREASING
HIGH CLOUD COVERAGE.
NORTH TO NORTHWEST WINDS AROUND 5 KT INLAND AND 8-12 KT WITH
GUSTS TO 20 KT ALONG THE COAST THIS AFTERNOON WILL EASE THIS
EVENING, BEFORE RISING TO 5-10 KT INLAND AND 10-15 KT WITH GUSTS
OF 20-25 KT ALONG THE COAST BY THURSDAY AFTERNOON.
KPDX AND APPROACHES...VFR CONDITIONS EXPECTED THROUGHOUT THE
PERIOD WITH INCREASING COVERAGE OF HIGH CLOUDS ON THURSDAY.
NORTHWEST WINDS OF LESS THAN 5 KT TONIGHT WILL RISE TO NEAR 10
KT BY THURSDAY AFTERNOON. -36
MARINE
HIGH PRESSURE OFFSHORE WILL MAINTAIN PREDOMINATELY
NORTHERLY WINDS ACROSS ALL WATERS THROUGH AT LEAST FRIDAY.
BREEZY NORTH WINDS CONTINUE WITH GUSTS UP TO 30 KT FROM LATE
TONIGHT THROUGH THURSDAY EVENING. THEREFORE, HAVE ISSUED A SMALL
CRAFT ADVISORY ACROSS ALL WATERS. SEAS 5 TO 8 FT THROUGH FRIDAY
WITH PERIOD OF 9 TO 11 SECONDS THROUGH AT LEAST THURSDAY NIGHT.
ANOTHER WEAKER SYSTEM IS EXPECTED TO APPROACH THE COASTAL
WATERS FROM THE NORTH LATE FRIDAY INTO SATURDAY. THIS WILL
RESULT IN A SOUTHERLY WIND SHIFT ALONG WITH SEAS SUBSIDING
TOWARDS 4 TO 6 FT AND GUSTS BELOW 20 KTS WITH THIS SYSTEM. /42
PQR WATCHES/WARNINGS/ADVISORIES
OR...NONE.
WA...NONE.
PZ...SMALL CRAFT ADVISORY FROM 5 AM TO 8 PM PDT THURSDAY FOR
PZZ251>253-271>273.
WWW.WEATHER.GOV/PORTLAND
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