024
FXUS66 KPQR 180532
AFDPQR
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE PORTLAND OR
1032 PM PDT THU SEP 17 2026
.UPDATED AVIATION DISCUSSION.
SYNOPSIS
TEMPERATURES TREND TOWARD NORMAL ON FRIDAY WITH A
SLIGHT INCREASE THROUGH THE WEEKEND. HEADING INTO NEXT WEEK, THE
PATTERN IS EXPECTED TOR TREND COOLER AS TROUGHING DROPS
SOUTHWARD FROM THE GULF OF ALASKA. DRY CONDITIONS ARE HEAVILY
FAVORED THROUGH THE NEXT WEEK WITH A POSSIBLE PATTERN SHIFT
TOWARD COOLER, WETTER CONDITIONS BY THE END OF NEXT WEEK.
DISCUSSION..NOW THROUGH WEDNESDAY
A CLOSED UPPER LEVEL LOW
COVERING NORTHERN CALIFORNIA TO EASTERN OREGON CONTINUES TO
SLOWLY SHIFT NORTHEAST AS RIDGING BUILDS IN FROM THE WEST. WARM
CONDITIONS PEAK TODAY BEFORE RETURNING TO NEAR NORMAL TOMORROW
AS ONSHORE FLOW RETURNS AND MARINE STRATUS IS EXPECTED TO BE IN
PLACE TO START THE NEXT FEW MORNINGS. WEAK OFFSHORE FLOW THAT
WAS IN PLACE ACROSS THE WESTERN SLOPES OF THE HIGHER TERRAIN
HAVE SHIFTED TO LIGHT WEST TO SOUTHWEST FLOW WHILE WINDS ACROSS
THE INTERIOR LOWLANDS ARE NORTHERLY. THE VAST MAJORITY OF THE
FORECAST AREA IS EXPECTED TO REMAIN DRY WITH THE ONLY EXCEPTION
BEING THE FAR SOUTHEASTERN PORTIONS OF LANE AND LINN COUNTIES
WHICH COULD SEE LIGHT SHOWERS OR A BRIEF THUNDERSTORM THROUGH
THE EVENING.
INCREASING ONSHORE FLOW IS EXPECTED TO HELP MARINE STRATUS DEVELOP
ALONG THE COAST LATER THIS EVENING, EVENTUALLY SPREADING EASTWARD UP
THE COLUMBIA RIVER INTO THE PORTLAND METRO AND THROUGH THE GAPS IN
THE COAST RANGE AND INTO THE WILLAMETTE VALLEY LATER TONIGHT. THIS
MEANS FRIDAY LIKELY BEGINS WITH CLOUDY SKIES FOR MUCH OF THE AREA
WHICH WILL IMPACT OVERALL HIGH TEMPERATURES. CLOUD COVER IS EXPECTED
TO DISSIPATE BY LATE MORNING ACROSS THE INTERIOR AND MAY NOT
COMPLETELY DISSIPATE ALONG THE COAST. HIGHS ARE EXPECTED TO PEAK
CLOSER TO NORMAL IN THE MID TO UPPER 70S ACROSS THE INTERIOR
LOWLANDS AND 60S FOR THE COAST AND HIGHER TERRAIN.
CONFIDENCE REMAINS HIGH HEADING INTO THE WEEKEND FOR A SLIGHT WARM
UP INTO THE UPPER 70S TO LOW 80S ACROSS THE INTERIOR AND NO
PRECIPITATION. BEYOND THE WEEKEND, THE PATTERN TRENDS TOWARD COOLER
TEMPERATURES AS TROUGHING DROPS SOUTHWARD FROM THE GULF OF ALASKA.
DETAILS AT THIS TIME ARE UNCLEAR REGARDING EXACT TEMPERATURES AND
PRECIPITATION. AS OF RIGHT NOW, CONDITIONS EXPECTED TO BE NEAR OR
SLIGHTLY BELOW AVERAGE FOR HIGHS AND MOSTLY DRY. MOST ENSEMBLE
MEMBERS ARE SHOWING DRY CONDITIONS THROUGH NEXT WEDNESDAY WITH A
MINORITY OF ~10% OF MEMBERS SHOWING MEASURABLE RAIN INLAND TUE-THU.
UNCERTAINTY INCREASES SUBSTANTIALLY BEYOND THIS TIME FRAME BUT THERE
ARE POSSIBLE SIGNALS FOR A PATTERN SHIFT TO A COOLER, WETTER PATTERN
BY THE END OF NEXT WEEK. -19
AVIATION...THROUGH 06Z SATURDAY
LATE THIS EVENING SATELLITE
IMAGERY AND TERMINAL OBSERVATIONS SHOW WIDESPREAD MVFR TO LOCALLY
IFR CONDITIONS DUE TO MARINE STRATUS ALONG THE COAST WHILE VFR
CONDITIONS PREVAIL INLAND. CONFIDENCE REMAINS HIGH THAT THE MARINE
AIRMASS ALONG THE COAST WILL GRADUALLY PROGRESS THROUGH THE COAST
RANGE GAPS ENTERING THE WILLAMETTE VALLEY AND I-5 CORRIDOR BY
12-15Z. THERE IS A 50-70% CHANCE AT ANY GIVEN HOUR BETWEEN 12-18Z
FRI FOR MVFR CIGS (1.5-3 KFT) ACROSS INLAND TERMINALS, WITH THE
HIGHEST CHANCES AT KEUG AND KTTD. STRATUS WILL GRADUALLY DISSIPATE
AFTER 17-19Z FRI ACROSS THE VALLEY AS DAYTIME HEATING PROGRESSES
WITH A RETURN TO WIDESPREAD VFR (EXCLUDING THE COAST). WINDS
GENERALLY REMAIN UNDER 10 KNOTS AT ALL SITES.
KPDX AND APPROACHES...VFR CONDITIONS WITH MOSTLY CLEAR SKIES
PERSIST THROUGH MOST OF THE OVERNIGHT HOURS. APPROACHING SUNRISE,
CHANCES FOR MVFR CIGS INCREASE, PEAKING AROUND 65-70% BETWEEN
14-17Z. CIGS THEN TREND BACK TO VFR AROUND 18-19Z ALTHOUGH
CONFIDENCE IN THIS TIMING IS ONLY MODERATE. -99/10
MARINE
HIGH PRESSURE WILL MAINTAIN LIGHT NORTHERLY WINDS
THROUGH THIS EVENING. TONIGHT INTO FRIDAY, WEAK LOW PRESSURE
WILL TURN WINDS MORE SOUTHERLY TO SOUTHWESTERLY BUT REMAIN BELOW
15 KT. HIGH PRESSURE RE-BUILDS OVER THE WATERS FRIDAY NIGHT
INTO SATURDAY, RETURNING NORTHERLY WINDS THROUGH NEXT WEEK. THIS
WEEKEND, THERE IS A 40-70% CHANCE FOR BRIEF AND ISOLATED WIND
GUSTS UP TO 25 KT ACROSS THE WATERS, WITH THE HIGHEST CHANCES
SUNDAY AFTERNOON ACROSS THE INNER WATERS OUT TO 10 NM OFFSHORE.
GIVEN THAT WIND GUSTS UP TO 25 KT ARE NOT EXPECTED TO BE
WIDESPREAD OR FREQUENT, SMALL CRAFT ADVISORIES ARE NOT
ANTICIPATED. SEAS AROUND 4-6 FT AT 8-10 SEC EXPECTED THROUGH
NEXT WEEK WITH A PERSISTENT NORTHWESTERLY SWELL. -10
PQR WATCHES/WARNINGS/ADVISORIES
OR...NONE.
WA...NONE.
PZ...NONE.
WWW.WEATHER.GOV/PORTLAND
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