196
FXUS66 KPQR 201757 AAB
AFDPQR
AREA FORECAST DISCUSSION...UPDATED
NATIONAL WEATHER SERVICE PORTLAND OR
1056 AM PDT SUN SEP 20 2026
..UPDATED AVIATION DISCUSSION
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 18Z MONDAY
SATELLITE IMAGERY AND TERMINAL
OBSERVATIONS AS OF LATE SUNDAY MORNING DEPICTS PREDOMINATELY
IFR/LIFR STRATUS ACROSS THE WILLAMETTE VALLEY AND COAST AS HIGH
PRESSURE KEEPS CIGS LOW. STRATUS IS BEGINNING TO GRADUALLY DISSIPATE
AND SHOULD CLEAR OUT FOR MOST TERMINALS BY 20-21Z SUN AS DAYTIME
HEATING PROGRESSES. AN EXCEPTION WOULD BE THE CENTRAL OREGON COAST
INCLUDING KONP, WHERE IFR STRATUS MAY LINGER THROUGHOUT THE DAY. VFR
CONDITIONS PREVAIL ACROSS THE VALLEY THROUGH LATE TONIGHT.
THIS EVENING AFTER 00-03Z MON, THERE IS HIGH CONFIDENCE (>80%) FOR A
RETURN OF IFR/MVFR STRATUS ALONG THE COAST. SIMILAR TO PREVIOUS
MORNINGS, WILL SEE A RETURN OF STRATUS ACROSS THE VALLEY BETWEEN 12-
18Z MON WITH A 30-50% CHANCE FOR MVFR CIGS AT ANY GIVEN HOUR. UNLIKE
TODAY, HIGH PRESSURE ALOFT WILL MOVE EASTWARD TOMORROW, SO CIGS MAY
NOT BE AS LOW TOMORROW (10-20% CHANCE FOR IFR AT ANY GIVEN HOUR
ACROSS THE VALLEY). HOWEVER, GIVEN THAT WE'LL GET DECENT ONSHORE
FLOW FROM AN APPROACHING TROUGH, STRATUS TOMORROW MORNING COULD
LINGER LONGER INTO THE AFTERNOON. NORTH/NORTHWESTERLY WINDS TODAY
UNDER 10 KT FOR MOST TERMINALS EXCEPT 10-15 KT WITH GUSTS UP TO 25
KT AT KONP.
KPDX AND APPROACHES...IFR CIGS AND MVFR VIS THROUGH 19-20Z SUN.
AFTERWARDS, VFR CONDITIONS PREVAIL THROUGH LATE TONIGHT. MVFR
STRATUS RETURNS AFTER 12Z MON, WITH A 10-20% CHANCE FOR IFR CIGS AT
ANY GIVEN HOUR BETWEEN 12-18Z MON. NORTHWESTERLY WINDS 4-6 KT TODAY,
WEAKENING OVERNIGHT. -10
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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