618
FXUS66 KPQR 301054
AFDPQR
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE PORTLAND OR
354 AM PDT SUN AUG 30 2026
SYNOPSIS
TODAY THROUGH MONDAY, A SHORTWAVE RIDGE OF HIGH
PRESSURE WILL BRING A BRIEF PERIOD OF DRY AND WARM CONDITIONS
WITH MOSTLY SUNNY SKIES. TUESDAY THROUGH THE END OF THE WEEK,
WILL SEE A SIGNIFICANT PATTERN CHANGE WITH COOLER TEMPERATURES,
WIDESPREAD RAIN CHANCES, AND A 5-15% CHANCE FOR THUNDERSTORMS.
WEDNESDAY AND THURSDAY ARE EXPECTED TO BE THE WETTEST DAYS.
TOWARDS THE END OF THE WEEK, WARMER AND DRIER CONDITIONS ARE
EXPECTED TO RETURN, BUT THERE IS A LOT OF UNCERTAINTY IN THE
FORECAST.
SHORT TERM...TODAY THROUGH TUESDAY
A SHORTWAVE RIDGE LOOKS TO
BUILD OVER THE REGION THROUGH MONDAY. THIS WILL RESULT IN A
BRIEF WARMING AND DRYING TREND THROUGH THE FIRST PART OF THIS
WEEK. DAYTIME HIGHS TODAY ARE EXPECTED TO WARM UP INTO THE MID
TO UPPER 70S FOR INTERIOR VALLEYS, MID TO UPPER 60S ALONG THE
COAST AND LOW TO UPPER 70S FOR THE CASCADES. AS FOR MONDAY,
DAYTIME HIGHS WILL WARM FURTHER INTO THE UPPER 70S TO MID 80S
FOR INTERIOR VALLEYS, MID 60S TO LOWER 70S ALONG THE COAST AND
UPPER 70S TO MID 80S FOR THE CASCADES. MONDAY WILL BE THE
WARMEST DAY OF THE WEEK AS THE RIDGE REACHES ITS PEAK. AS
TUESDAY APPROACHES, THE SHORT WAVE RIDGE WILL GET DISPLACED BY
A SERIES OF UPPER LEVEL LOWS/TROUGHS DIVING SOUTHWARD OUT OF THE
GULF OF ALASKA. THESE INCOMING SYSTEMS WILL BRING ABOUT A
SIGNIFICANT COOL AND MOIST PATTERN FOR THE PAC NW FOR TUESDAY.
THE FIRST OF TWO LOWS WILL SWING DOWN FROM THE GULF OF ALASKA
AND TRACK TOWARDS OR/CA BORDER. THIS WILL BRING WIDESPREAD CLOUD
COVER, COOLER DAYTIME HIGHS AND ABOUT A 35-75% CHANCE FOR LIGHT
SHOWERS ON THROUGH TUESDAY NIGHT. DAYTIME HIGHS ON TUESDAY LOOK
TO BE AROUND 5-10 DEGREES COOLER THAN MONDAY WITH HIGHS IN THE
UPPER 60S TO MID 70S FOR INTERIOR VALLEYS, MID 50S TO MID 60S
ALONG THE COAST AND UPPER 60S TO MID 70S FOR THE CASCADES.
GIVEN THE POSITION OF THIS TROUGH, THIS WILL RESULT IN SOUTHERLY
FLOW ALOFT WHICH IS A FAVORABLE PATTERN FOR THUNDERSTORMS IN
OUR REGION. HOWEVER, THERE IS A LOT OF UNCERTAINTY AS TO HOW
MUCH INSTABILITY WILL ACCOMPANY THE TUESDAY/TUESDAY NIGHT
SYSTEM. MODEL SOUNDINGS ARE CURRENTLY SHOWING MINIMAL MOST
UNSTABLE, CONVECTIVE AVAILABLE POTENTIAL ENERGY (MUCAPE), WITH
VALUES MAXING OUT AROUND 100-150 J/KG OVER THE CASCADES. FOR
NOW, THERE IS ABOUT A 5-15% CHANCE FOR THUNDERSTORMS ACROSS THE
REGION ON TUESDAY INTO TUESDAY NIGHT. /42
LONG TERM...WEDNESDAY THROUGH SATURDAY
WEDNESDAY INTO EARLY
THURSDAY IS SHAPING UP TO BE MORE SIGNIFICANT, AS THE STRONGER
OF THE TWO SYSTEMS MOVE INTO THE PAC NW. THE ASSOCIATED FRONT
WITH THIS SYSTEM SWINGS THROUGH ON WEDNESDAY, BRINGING MORE
WIDESPREAD RAIN, COOLER TEMPERATURES, AND BREEZIER SOUTHERLY
WINDS. CHANCES FOR EXCEEDING 1 INCH OF RAIN IN 48 HOURS BETWEEN
5 AM WEDNESDAY TO 5 AM FRIDAY ARE AROUND 75-90% ACROSS THE CWA,
WITH THE HIGHEST CHANCES ALONG THE COAST, COAST RANGE, AND
CASCADES. CHANCES FOR EXCEEDING 2 INCHES DURING THIS SAME
TIMEFRAME ARE AROUND 25-40% FOR THESE HIGHER TERRAIN FEATURES,
AND 10-20% ALONG THE I-5 CORRIDOR.
THURSDAY AFTERNOON TO FRIDAY, THE UPPER-LEVEL TROUGH MOVES
DIRECTLY OVERHEAD AND WE TRANSITION INTO A POST-FRONTAL
ENVIRONMENT WITH LINGERING SHOWERS. GIVEN THAT THERE WILL BE
COOLER AIR ALOFT, THIS WILL FAVOR INCREASING ATMOSPHERIC
INSTABILITY AND THUS CHANCES FOR THUNDERSTORMS. THERE IS AROUND
A 15-20% CHANCE FOR THUNDERSTORMS ON THURSDAY FOLLOWING THE
INITIAL FRONTAL PASSAGE. ANY PASSING THUNDERSTORMS MAY PRODUCE
LIGHTNING, HEAVY RAIN, ERRATIC WINDS, AND SMALL HAIL. OVERALL,
WHILE THE UPCOMING RAIN WILL NOT QUITE YET BE A "FIRE SEASON
ENDER," IT WILL DEFINITELY SLOW DOWN FIRE SEASON AND HELP PUT A
DAMPER ON ONGOING WILDFIRES. /42-10
AVIATION...THROUGH 12Z MONDAY
GENERALLY VFR CONDITIONS ACROSS
THE AIRSPACE. HOWEVER, SATELLITE IMAGERY IS SHOWING SOME PATCHY
STRATUS DEVELOPING AT VARIOUS LOCATIONS ACROSS THE AIRSPACE.
PRIMARILY, THE MARINE STRATUS IS DEVELOPING NEAR PDX, KTTD AND
IN- BETWEEN KSLE AND KEUG. WITH THAT IN MIND, THERE IS A 20-40%
CHANCE FOR MVFR CONDITIONS TO AT THESE LOCATIONS THROUGH AT
LEAST 16Z SUNDAY. ANY LOWERED FLIGHT CONDITIONS THAT DO DEVELOP,
SHOULD RETURN BACK TO VFR BETWEEN 16Z-18Z SUNDAY, WHICH SHOULD
PERSIST THROUGH THE REMAINDER OF THE TAF PERIOD.
WINDS GENERALLY NORTH TO NORTHEAST LESS THAN 6 KTS THROUGH 16Z
SUNDAY, BECOMING MORE NORTHERLY AND INCREASING TO 6-10 KTS AFTER
18Z-21Z SUNDAY. ALSO, EXPECT GUSTS APPROACHING 22 KT AROUND
KEUG AND KONP STARTING AROUND 19Z SUNDAY THROUGH AROUND 03Z
MONDAY.
KPDX AND APPROACHES...VFR CONDITIONS PREVAIL WITH A 20-40% CHANCE
OF MVFR CONDITIONS DEVELOPING THROUGH 16Z SUNDAY. CONDITIONS
EXPECTED TO IMPROVE TO VFR BETWEEN 16Z-18Z SUNDAY. WINDS GENERALLY
NORTH TO NORTHWEST 3-5 KTS, INCREASING TO AROUND 7-10 KTS AFTER
22Z SUNDAY. /42
MARINE
A SHORTWAVE UPPER-LEVEL RIDGE WILL BUILD OVER THE WATERS
THROUGH TUESDAY. THIS MAINTAIN NORTH/NORTHWEST WINDS THAT WILL
SLOWLY STRENGTHEN AS THE RIDGE BUILDS, REACHING DIURNAL PEAKS
AROUND 10-15 KT SUNDAY AND MONDAY AFTERNOONS. BY TUESDAY, A MORE
ROBUST UPPER-LEVEL TROUGH DIGGING OVER THE NORTHEAST PACIFIC WILL
RESULT IN A SOUTHERLY WIND SHIFT ACROSS ALL WATERS BY TUESDAY
MORNING. LARGELY WIND-DRIVEN SEAS THROUGH THIS PERIOD WILL PERSIST
AROUND 4-6 FT.
AS THE AFOREMENTIONED TROUGH AND ASSOCIATED FRONTS APPROACH THE
COAST TUESDAY INTO WEDNESDAY, WILL BRING INCREASING SOUTHERLY
WINDS WITH GUSTS UP TO 35 KT POSSIBLE. IF THE FORECAST TRENDS
CONTINUE, WILL LIKELY BE ISSUING A GALE WATCH IN THE NEAR FUTURE.
SEAS WILL SIMILARLY BUILD TOWARDS 10-12 FT AS WINDS INCREASE ALONG
WITH A FRESH SWELL. TOWARDS THE LATTER PART OF THE UPCOMING WEEK,
EXPECT WINDS AND SEAS TO EASE. /42
PQR WATCHES/WARNINGS/ADVISORIES
OR...NONE.
WA...NONE.
PZ...NONE.
WWW.WEATHER.GOV/PORTLAND
INTERACT WITH US VIA SOCIAL MEDIA:
WWW.FACEBOOK.COM/NWSPORTLAND
X.COM/NWSPORTLAND
CLICK HERE TO GO TO PREVIOUS BULLETINS.
Main Text Page