489
FXUS66 KPQR 281102
AFDPQR
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE PORTLAND OR
402 AM PDT FRI AUG 28 2026
SYNOPSIS
A COOL AND SOMEWHAT UNSETTLED PATTERN WILL PERSIST
THROUGH THE WEEKEND AS UPPER-LEVEL TROUGHING REMAINS OVER THE
PACIFIC NORTHWEST. PERIODIC MARINE PUSHES WILL CONTINUE TO BRING
MORNING CLOUD COVER INLAND, WHILE WEAK DISTURBANCES MAY PRODUCE
OCCASIONAL LIGHT PRECIPITATION ALONG THE COAST AND AT HIGHER
TERRAIN. FORECAST UNCERTAINTY INCREASES INTO EARLY NEXT WEEK AS
ENSEMBLE SOLUTIONS ARE POINTING TOWARDS A LOW PRESSURE SYSTEM
BRINGING PRECIPITATION INTO THE REGION.
DISCUSSION...TODAY THROUGH THURSDAY
UPPER-LEVEL TROUGHING
REMAINS THE DOMINANT FEATURE OVER THE NORTHEAST PACIFIC, MAINTAINING
A COOL AIR MASS AND PERSISTENT ONSHORE FLOW ACROSS THE REGION.
WHILE CLOUDIER AND COOLER DAYS REMAIN IN THE FORECAST THROUGH
THE WEEKEND, PRECIPITATION CHANCES REMAIN LOW, WITH MOST LOCATIONS
STAYING DRY. TEMPERATURES TODAY LOOK TO TOP OUT IN THE UPPER 70S
TO LOW 80S ACROSS THE INTERIOR, 60S ALONG THE COAST AND UPPER
60S TO MID 70S FOR THE CASCADES.
THIS BROAD TROUGHING WILL REMAIN IN PLACE THROUGH SATURDAY,
A WEAK, EMBEDDED PERTURBATION WITHIN THE OVERALL FLOW COULD
BRIEFLY ENHANCE PRECIPITATION CHANCES, PARTICULARLY NORTH OF A
LINE FROM MCMINNVILLE AND MOLALLA. ENSEMBLE GUIDANCE CURRENTLY
GIVES A 20-60% CHANCE OF TOTAL RAINFALL AMOUNTS ACROSS THESE
AREAS OF 0.05 INCHES TO 0.20 INCHES. ANY PRECIPITATION THAT
DEVELOPS IS EXPECTED TO BE LIGHT, WITH THE COAST, COAST RANGE,
AND CASCADE FOOTHILLS FAVORED FOR THE HIGHEST CHANCES. CONTINUED
ONSHORE FLOW WILL ALSO MAINTAIN THE POTENTIAL FOR MORNING MARINE
STRATUS ACROSS THE INTERIOR. BY SUNDAY, THE UPPER-LEVEL LOW
SHIFTS EASTWARD OF THE CASCADES AND A SHORTWAVE RIDGE BUILDS
OVER THE REGION FOR THE START OF THE WEEK. THIS TRANSITION WILL
RESULT IN DAYTIME HIGHS ON SUNDAY TO BE A FEW DEGREES WARMER
THAN SATURDAY AND FURTHER WARMING IS EXPECTED ON MONDAY WITH
DAYTIME HIGHS IN THE UPPER 70S TO LOW 80S ACROSS THE INTERIOR,
60S ALONG THE COAST AND INTO THE 70S FOR THE CASCADES.
LOOKING TOWARDS NEXT WEEK, ENSEMBLE GUIDANCE CONTINUES TO FAVOR
A COOLER AND POTENTIALLY WETTER PATTERN, BUT CONFIDENCE REMAINS
LOW, EVEN WITH MOST MODELS AND THEIR ENSEMBLES SHOWING SOME AMOUNT
OF MEASURABLE PRECIPITATION. WHILE A MAJORITY OF ENSEMBLE MEMBERS
SUPPORT MEASURABLE PRECIPITATION ACROSS A LARGER PORTION OF THE
FORECAST AREA, THERE REMAINS SUBSTANTIAL SPREAD IN THE FINER
DETAILS SUCH AS TIMING, STRENGTH, AND POSITION OF THE UPPER-
LEVEL TROUGH.
PROBABILISTIC GUIDANCE SUGGESTS AT LEAST 0.01 INCHES OF RAIN
OVER 48 HOURS FROM LATE TUESDAY TO LATE THURSDAY RANGES FROM
70-90%. AS FOR CHANCES OF HIGHER AMOUNTS OF RAIN, THERE IS A
45-80% CHANCE FOR 0.25 INCHES, 30-65% CHANCE FOR 0.50 INCHES,
AND A 15-45% CHANCE FOR 1 INCH. WHILE THIS ISN'T SHAPING UP TO
BE A "FIRE SEASON ENDER", THE AMOUNT OF RAINFALL WILL AT A
MINIMUM WILL BE LOOKED UPON AS FAVORABLE BY MOST. STILL, WHILE
THE PATTERN CONTINUES TO LOOK FAVORABLE FOR PRECIPITATION, IT
MUST BE POINTED OUT THAT WE ARE TALKING ABOUT RAIN ON DAYS 4-6
AND THE FORECAST WILL MOST LIKELY CHANGE BETWEEN NOW AND THEN.
/42~12
AVIATION...THROUGH 12Z SATURDAY
AN UPPER-LEVEL TROUGH
EXTENDING OVER THE PACIFIC NORTHWEST WILL CONTINUE TO SUPPORT
ONSHORE FLOW THROUGH THE TAF PERIOD. CURRENT OBSERVATIONS AS OF
11Z FRIDAY SHOW SCATTERED AREAS OF MVFR TO LIFR CONDITIONS ACROSS
THE AIRSPACE. COASTAL LOCATIONS ARE EXPECTED TO FILL IN WITH
IFR/LIFR CONDITIONS OVER THE NEXT FEW HOURS, WITH SCATTERED MVFR
CONDITIONS FOR INLAND LOCATIONS. KEUG, KPDX AND KTTD HAVE THE
HIGHEST PROBABILITY FOR THESE MVFR CONDITIONS TO DEVELOP THROUGH
15Z FRIDAY, WITH KTTD ALREADY SHOWING MVFR CONDITIONS AT THIS
TIME. ANY LOWERED FLIGHT CONDITIONS ARE EXPECTED TO IMPROVE
TOWARDS VFR BY 17Z-19Z FRIDAY FOR INLAND LOCATIONS AND 18Z-21Z
FRIDAY FOR COASTAL LOCATIONS. NORTH TO NORTHWEST WINDS WILL BUILD
TO 5-10 KT INLAND AND 8-12 KT ALONG THE COAST BY MIDDAY FRIDAY.
COULD SEE SOME GUSTS ALONG THE COAST (KONP) AND INLAND (KHIO AND
KSLE) UP TO 20 KT BETWEEN 20Z FRIDAY THROUGH 06Z SATURDAY.
PERSISTENT ONSHORE FLOW, WILL BRING A RETURN OF MVFR TO LIFR
CONDITIONS TO THE COAST STARTING AROUND 06Z-08Z SATURDAY, WITH
MVFR CONDITIONS EXPECTED TO RETURN TO KEUG, KTTD AND KPDX AFTER
12Z SATURDAY.
KPDX AND APPROACHES...VFR CONDITIONS EXPECTED TO PERSIST, WITH A
45-60%, FOR MVFR CIGS DEVELOPING AROUND 13Z-15Z FRIDAY WITH
BACKBUILDING CLOUDS DEVELOPING. FLIGHT CONDITIONS EXPECTED TO
IMPROVE TO VFR AROUND 16Z-18Z FRIDAY AND REMAIN UNTIL MVFR
CONDITIONS COULD RETURN AFTER 12Z SATURDAY. NORTHWEST WINDS TO 5-8
KT BY FRIDAY AFTERNOON. /42
MARINE
BROAD TROUGHING CONTINUES IN ACROSS THE NE PACIFIC
BRINGING NORTH-NORTHWESTERLY WINDS TODAY. WINDS ARE EXPECTED TO
REMAIN AROUND 10-15 KT OR LESS. A WEAK FRONT DROPS INTO THE
NORTHERN COASTAL WATERS LATE TONIGHT INTO SATURDAY WITH LITTLE TO
NO IMPACT EXPECTED. NORTHERLIES PERSIST THROUGH THE WEEKEND WHILE
PREDOMINATELY WIND DRIVEN SEAS REMAIN AT AROUND 3 TO 5 FT. THE
PATTERN MAY BECOME A BIT MORE ACTIVE AS A BROAD UPPER LEVEL TROUGH
APPROACHES THE REGION TOWARDS THE START OF NEXT WEEK AND IS
FOLLOWED BY AN ALASKAN LOW MOVING SOUTHEAST FROM THE GULF OF
ALASKA INTO THE PAC NW. THIS SECOND SYSTEM COULD BRING LOW END
GALE FORCE GUSTS ACROSS OUR WATERS BY THE MIDDLE OF NEXT WEEK AS
WELL AS RESULT IN SEAS BUILDING TOWARDS 10 FT. /42-DH
PQR WATCHES/WARNINGS/ADVISORIES
OR...NONE.
WA...NONE.
PZ...NONE.
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