850
FXUS66 KPQR 280526
AFDPQR
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE PORTLAND OR
1026 PM PDT THU AUG 27 2026
UPDATED AVIATION DISCUSSION.
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 DIVERGE ON THE PATTERN.
DISCUSSION...NOW THROUGH WEDNESDAY
UPPER-LEVEL TROUGHING REMAINS
THE DOMINANT FEATURE OVER THE NORTHEAST PACIFIC, MAINTAINING A
COOL AIR MASS AND PERSISTENT ONSHORE FLOW ACROSS THE REGION.
ANOTHER PUSH OF MARINE STRATUS IS EXPECTED TONIGHT INTO FRIDAY
MORNING, WITH CLOUDS LIKELY REACHING WELL INTO THE INTERIOR
LOWLANDS. DESPITE THE CLOUD COVER, PRECIPITATION CHANCES REMAIN
LOW, WITH MOST LOCATIONS STAYING DRY. TEMPERATURES FRIDAY SHOULD
REMAIN IN THE UPPER 70S ACROSS THE INTERIOR AND 60S ALONG THE
COAST.
THE BROADER TROUGH WILL REMAIN IN PLACE THROUGH SATURDAY, ALTHOUGH
ANOTHER WEAK DISTURBANCE MAY ENHANCE PRECIPITATION CHANCES,
PARTICULARLY NORTH OF A LINE FROM MCMINNVILLE AND MOLLALA.
ENSEMBLE GUIDANCE CURRENTLY GIVES A 20-60% CHANCE OF MEASURABLE
RAINFALL ACROSS THESE AREAS. 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 EAST
AND A SHORTWAVE RIDGE FORMS, ALLOWING TEMPERATURES TO INCREASE
1 TO 3 DEGREES INTO THE UPPER 70S ACROSS INTERIOR.
LOOKING INTO EARLY NEXT WEEK, ENSEMBLE GUIDANCE CONTINUES TO
FAVOR A COOLER AND POTENTIALLY WETTER PATTERN, BUT CONFIDENCE
REMAINS LIMITED. AN INCREASING NUMBER OF ENSEMBLE MEMBERS
SUPPORT MEASURABLE PRECIPITATION ACROSS A LARGER PORTION OF THE
FORECAST AREA, THOUGH THERE REMAINS SUBSTANTIAL SPREAD IN THE
TIMING, AMPLITUDE, AND EVENTUAL POSITION OF THE UPPER-LEVEL
TROUGH. FURTHER REFINEMENT WILL BE POSSIBLE AS THE PATTERN
BECOMES BETTER RESOLVED. LASTLY, TO GIVE A ROUGH APPROXIMATION
OF EXPECTED PRECIPITATION EARLY NEXT WEEK, PROBABILISTIC
GUIDANCE SUGGESTS CHANCES FOR AT LEAST 0.01 INCHES OF RAIN
OVER 48 HOURS FROM EARLY TUESDAY TO LATE WEDNESDAY RANGES FROM
70-90%. AS FOR CHANCES OF HIGHER AMOUNTS OF RAIN, THERE IS A
40-70% CHANCE FOR 0.25 INCHES, 25-50% CHANCE FOR 0.50 INCHES,
AND A 5-30% CHANCE FOR 1 INCH. ~12
AVIATION...THROUGH 06Z SATURDAY
AN UPPER-LEVEL TROUGH
EXTENDING OVER THE PACIFIC NORTHWEST WILL SUPPORT CONTINUED
ONSHORE FLOW AND INCREASED NIGHTTIME CHANCES FOR RESTRICTED CIGS
AS MARINE STRATUS PUSHES INLAND. CLOUD COVERAGE WILL INCREASE
INITIALLY ALONG THE COAST, WITH HIGH CONFIDENCE IN MVFR CIGS,
BUT ONLY MODERATE CHANCES FOR IFR, HIGHEST ALONG THE CENTRAL
OREGON COAST (70% AT KONP) AND DECREASING TO THE NORTH (30% AT
KAST). INLAND, CHANCES FOR MVFR CIGS INCREASE THROUGH THE NIGHT,
REACHING 50-70% AT KTTD AND KEUG BY 11-13Z FRI AND 30-50% AT
OTHER INLAND TERMINALS. LOW CLOUDS WILL ERODE THROUGH THE
MORNING, WITH A RETURN TO VFR CONDITIONS BY 16-18Z FRI INLAND
AND 18-21Z FRI ALONG THE COAST. NORTH TO NORTHWEST WINDS OF 3 KT
OR LESS TONIGHT WILL BUILD TO 5-10 KT INLAND AND 8-12 KT ALONG
THE COAST BY MIDDAY FRIDAY.
KPDX AND APPROACHES...VFR CONDITIONS EXPECTED TO PREVAIL
THROUGHOUT THE PERIOD, WITH MODERATE CHANCES, 40-50%, FOR MVFR
CIGS FROM 13-17Z FRI AS MARINE STRATUS PUSHES INLAND. LOW CLOUDS
WILL THEN TEND TO ERODE BY MIDDAY FRIDAY. NORTHWEST WINDS EASE TO
3-5 KT TONIGHT, THEN BUILD TO 5-8 KT BY FRIDAY AFTERNOON. -36
MARINE
AS LOW PRESSURE NEAR VANCOUVER ISLAND WEAKENS, HIGH
PRESSURE CONTINUES TO BUILD IN ACROSS THE NE PACIFIC. LIGHT
SOUTHERLY WINDS VEER WESTERLY LATER THIS AFTERNOON, BECOMING
NORTH-NORTHWESTERLY BY EARLY FRIDAY. WINDS ARE EXPECTED TO
REMAIN AROUND 10-15 KT OR LESS. A WEAK FRONT DROPS INTO THE
NORTHERN COASTAL WATERS LATE FRIDAY 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 EARLY TO THE MIDDLE OF
NEXT WEEK AS THERE IS POTENTIAL FOR MULTIPLE FRONTAL SYSTEMS TO
MOVE INTO THE COASTAL WATERS. /DH
PQR WATCHES/WARNINGS/ADVISORIES
OR...NONE.
WA...NONE.
PZ...NONE.
WWW.WEATHER.GOV/PORTLAND
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