470
FXUS66 KPQR 200954
AFDPQR
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE PORTLAND OR
254 AM PDT SUN SEP 20 2026
SYNOPSIS
AREAS OF FOG AND LOW CLOUDS SUNDAY MORNING WILL GIVE WAY
TO SUNNY AND WARM CONDITIONS IN THE AFTERNOON. TEMPERATURES TREND
COOLER MONDAY THROUGH FRIDAY AS UPPER LEVEL TROUGHING DEVELOPS OVER
THE GULF OF ALASKA. CHANCES FOR RAIN HAVE INCREASED THURSDAY NIGHT
INTO FRIDAY TO 40-60% AS TROUGHING ATTEMPTS PUSHING INTO WESTERN
WASHINGTON AND WESTERN OREGON.
SHORT TERM...NOW THROUGH WEDNESDAY
GUIDANCE IS IN STRONG AGREEMENT
THAT A BROAD BUT LOW-AMPLITUDE RIDGE WILL STEADILY SHIFT EASTWARD
THROUGH THE MIDDLE OF NEXT WEEK WHILE BEING REPLACED BY AN
UPPER-LEVEL TROUGH DIGGING SOUTHWARD OVER THE GULF OF ALASKA. UPPER
LEVEL FLOW WILL BECOME SOUTHWESTERLY OVER WASHINGTON AND OREGON AHEAD
OF THE AFOREMENTIONED TROUGH, WITH NO SIGNS OF ANY SIGNIFICANT
MOISTURE PUSHING INLAND. AS SUCH, THE FORECAST REMAINS DRY THROUGH
WEDNESDAY. AFTER UPPER LEVEL HEIGHTS PEAK ON SUNDAY, MID-LEVEL
TEMPERATURES WILL BEGIN TO TREND DOWNWARD MONDAY THROUGH WEDNESDAY,
WHICH WILL BRING A COOLING TREND ACROSS THE REGION.
SURFACE TEMPERATURES WILL REACH AROUND 4-7 DEGREES ABOVE NORMAL OVER
INLAND AREAS SUNDAY AFTERNOON AFTER AREAS OF MORNING FOG AND LOW
CLOUDS LIFT, WITH HIGHS MOST LIKELY IN THE UPPER 70S TO LOW 80S OVER
THE LOWLANDS. MEANWHILE, TEMPERATURES WILL REMAIN NEAR NORMAL AT THE
COAST IN THE 60S. AS ONSHORE FLOW STRENGTHENS MONDAY THROUGH
WEDNESDAY AND TEMPERATURES COOL ALOFT, SURFACE TEMPERATURES WILL
STEADILY COOL BE A FEW DEGREES EACH DAY OVER INLAND AREAS. OTHERWISE,
LONGER NIGHTS AND LIGHT WINDS WILL FAVOR PERIODS OF EARLY MORNING FOG
IN SHELTERED VALLEYS EACH DAY, WITH A TYPICAL FALL PATTERN OF LOW
CLOUDS PUSHING INLAND OVERNIGHT AND CLEARING THROUGH THE DAY. -23
LONG TERM...WEDNESDAY NIGHT THROUGH SATURDAY NIGHT
THE FORECAST
REMAINS DRY AND MILD WEDNESDAY NIGHT THROUGH THURSDAY AFTERNOON AS
DRY SOUTHWEST FLOW ALOFT PERSISTS. HOWEVER, CHANCES FOR RAIN THURSDAY
NIGHT INTO FRIDAY HAVE INCREASED DUE TO AN UPTICK IN THE NUMBER OF
ENSEMBLE MEMBERS SHOWING AT LEAST SOME QPF OVER THE AREA WITH AN
APPROACHING UPPER LEVEL TROUGH. CHANCES FOR PRECIPITATION FALLING
WITHIN A 24-HOUR PERIOD ENDING AT 5 PM FRIDAY HAVE INCREASED TO
40-60%. EXACT TIMING AND RAIN AMOUNTS REMAIN UNCERTAIN, AND AROUND
30-40% OF ENSEMBLE GUIDANCE CONTINUES TO SHOW NO RAIN AT ALL OVER THE
WILLAMETTE VALLEY. THEREFORE, CONFIDENCE IS ONLY MODERATE AND IT IS
TOO SOON TO TELL IF FRIDAY WILL FOR SURE BE A WET DAY OR NOT.
REGARDLESS OF THE OUTCOME, CHANCES FOR RAIN DECREASE SIGNIFICANTLY
FRIDAY NIGHT INTO SATURDAY TO LESS THAN 15%, SUGGESTING MULTIPLE DAYS
WITH RAIN ARE UNLIKELY.
IT IS ALSO WORTH MENTIONING THAT CHANCES FOR FROST INCREASE OVER THE
UPPER HOOD RIVER VALLEY FRIDAY NIGHT AND SATURDAY NIGHT WHEN THERE IS
A 30-50% CHANCE FOR OVERNIGHT LOWS AROUND 37 DEGREES OR COLDER,
MAINLY IN THE PARKDALE AREA. PROBABILITIES ARE AROUND 10% IN ODELL
AND 1-5% IN HOOD RIVER. THOSE WITH SENSITIVE OUTDOOR VEGETATION IN
THIS AREA SHOULD MONITOR THE FORECAST OVER THE COMING DAYS. -23
AVIATION...THROUGH 06Z MONDAY
LATE THIS EVENING SATELLITE AND
SURFACE OBSERVATIONS SHOW GENERALLY VFR CONDITIONS ACROSS THE
REGION OUTSIDE OF SOME LOW CLOUDS/FOG ALONG PORTIONS OF THE OREGON
COAST, COAST RANGE, AND SOUTHERN WILLAMETTE VALLEY (INCLUDING
KEUG). THIS LOW CLOUD/FOG LAYER SHOULD CONTINUE EXPANDING UP THE
COASTLINE AS THE NIGHT PROGRESSES WITH WIDESPREAD DEGRADED
CIGS/VIS BY 12-14Z SUNDAY. EXPECT GRADUAL IMPROVEMENT TO MVFR AT
COASTAL TERMINALS BY THE MIDDAY HOURS WITH DECENT CHANCES FOR AT
LEAST SOME CLEARING DURING THE MID TO LATE AFTERNOON.
INLAND TERMINALS HAVE INCREASING CHANCES FOR A PERIOD OF FOG AND
LOW STRATUS BETWEEN 13-18Z SUNDAY, WITH KEUG ALREADY OBSERVING
DENSE FOG WITH LIFR FLIGHT CONDITIONS AS OF 09Z SUNDAY. OUTSIDE
OF THE SOUTH WILLAMETTE VALLEY, KSLE, KUAO, AND KTTD ARE OTHER
SITES WHICH COULD SEE SOME DEGRADED CONDITIONS (40-50% CHANCE)
BETWEEN 13-18Z BUT CONFIDENCE IN THE EXACT PLACEMENT OF THE FOG
REMAINS TOO LOW TO ADD IT AS A PREVAILING CONDITION AT THIS TIME.
HIGH CONFIDENCE (90%) IN WIDESPREAD VFR CONDITIONS AT INLAND
SITES SUNDAY AFTERNOON AND EVENING. WINDS STAY FAIRLY LIGHT
OVERALL OUTSIDE OF THE COAST WHERE INCREASING NORTHWESTERLY WINDS
AT SITES LIKE KONP LIKELY GUST UP AROUND 15-25 KNOTS SUNDAY
AFTERNOON.
KPDX AND APPROACHES...VFR CONDITIONS PREVAIL THROUGH LATE
TONIGHT. HOWEVER, THERE IS A CHANCE OF FOG AND/OR LOW STRATUS
BETWEEN 13-18Z SUNDAY (10-15% CHANCE FOR SURFACE VISIBILITIES OF 1
SM OR LOWER DURING THAT TIME, AND A 40-50% CHANCE FOR CEILINGS OF
1000 FT OR LOWER). THE LATEST GUIDANCE CONTINUES SHOWING THE
HIGHEST PROBABILITIES FOR FOG AND LOW STRATUS TO THE EAST AND
SOUTH OF THE KPDX TERMINAL. CONFIDENCE IN FOG AND/OR LOW STRATUS
DEVELOPMENT DIRECTLY OVER THE TERMINAL REMAINS TOO LOW TO REFLECT
IN THE TAF. OTHERWISE, HIGH CONFIDENCE IN VFR CONDITIONS 18-19Z
ONWARD WITH FAIRLY LIGHT WINDS (LESS THAN 10 KNOTS) THROUGH THE
TAF PERIOD. -99/23
MARINE
HIGH PRESSURE OVER THE WATERS WILL MAINTAIN NORTHERLY
WINDS THROUGH THIS WEEKEND. NORTHERLY WINDS PEAK IN STRENGTH
SUNDAY AFTERNOON AND EVENING WHEN THERE IS A 50-90% CHANCE FOR
MAXIMUM WIND GUSTS OF 21 KT OR SLIGHTLY STRONGER ACROSS THE
WATERS, WITH THE HIGHEST CHANCES ACROSS THE INNER WATERS OUT TO 10
NM OFFSHORE. GIVEN WIND GUSTS OF THIS MAGNITUDE ARE NOT EXPECTED
TO BE FREQUENT OR WIDESPREAD, SMALL CRAFT ADVISORIES ARE NOT
ANTICIPATED AT THIS TIME. SIGNIFICANT WAVE HEIGHTS WILL REMAIN
AROUND 3 TO 5 FT THROUGH THE WEEKEND, MAINLY DRIVEN BY A
PERSISTENT NORTHWESTERLY SWELL WITH A DOMINANT WAVE PERIOD NEAR 7
SECONDS.
NORTHERLY WINDS ARE EXPECTED TO LINGER MONDAY THROUGH WEDNESDAY,
WITH WIND GUSTS GENERALLY STAYING UNDER 20 KT. A LONG PERIOD
WEST-NORTHWESTERLY SWELL IS SET TO ARRIVE EITHER MONDAY AFTERNOON
OR EVENING, PUSHING SEAS UP BY ONE TO TWO FEET. HOWEVER, SEAS
WILL NOT BE PARTICULARLY STEEP AS THE DOMINANT WAVE PERIOD WITH
THIS SWELL WILL BE AROUND 11-13 SECONDS. -23
PQR WATCHES/WARNINGS/ADVISORIES
OR...NONE.
WA...NONE.
PZ...NONE.
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