483
FXUS66 KPQR 301911
AFDPQR
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE PORTLAND OR
1211 PM PDT SUN AUG 30 2026
SYNOPSIS
HIGH PRESSURE WILL RESULT IN DRY AND WARM CONDITIONS
ACROSS THE AREA TODAY AND MONDAY. A SIGNIFICANT PATTERN CHANGE
BEGINS ON TUESDAY WITH A RETURN OF COOLER TEMPERATURES, RAIN,
AND BREEZY SOUTHERLY WINDS THROUGH THE END OF THE WEEK.
WEDNESDAY AND THURSDAY ARE EXPECTED TO BE THE WETTEST DAYS WITH
ALSO A 10-20% CHANCE FOR THUNDERSTORMS. CONDITIONS TREND
SLIGHTLY DRIER OVER THE WEEKEND, BUT THERE REMAINS CHANCES FOR
LINGERING SHOWERS.
SHORT TERM...TODAY THROUGH TUESDAY NIGHT
SATELLITE IMAGERY
AND SURFACE OBSERVATIONS AS OF LATE SUNDAY MORNING DEPICTS
MOSTLY SUNNY SKIES ACROSS THE AREA WITH SOME SCATTERED CLOUDS
ACROSS SOUTHWEST WASHINGTON AND FAR NORTHWEST OREGON. WILL
MAINTAIN DRY AND WARM CONDITIONS TODAY AND MONDAY AS SHORTWAVE
RIDGING SETS UP OVER THE PACIFIC NORTHWEST. EXPECT AFTERNOON
HIGHS IN THE MID TO UPPER 70S TODAY ACROSS INTERIOR VALLEYS, AND
60S ALONG THE COAST. TOMORROW WILL BE THE WARMEST DAY OF THE
WEEK AS THE RIDGE REACHES ITS PEAK AMPLITUDE, WITH HIGHS WARMING
UP INTO THE MID 80S ACROSS INTERIOR VALLEYS. THIS DRY AND WARM
WEATHER WILL BE SHORT-LIVED AS WE HEAD INTO A SIGNIFICANT
PATTERN CHANGE BEGINNING TUESDAY.
MONDAY NIGHT INTO TUESDAY, THE AFOREMENTIONED RIDGE WILL WEAKEN
AND GET PUSHED EASTWARD AS THE FIRST OF TWO UPPER-LEVEL TROUGHS
DROPS DOWN FROM THE GULF OF ALASKA. THIS TROUGH WILL TRACK
TOWARDS SOUTHERN OREGON AND NORTHERN CALIFORNIA, BRINGING
INCREASED CLOUD COVER AND A 25-50% CHANCE FOR LIGHT SHOWERS.
THIS WILL SUPPORT COOLER TEMPERATURES ACROSS INTERIOR VALLEYS,
WITH TUESDAY AFTERNOON HIGHS FALLING INTO THE LOW TO MID 70S.
WINDS WILL ALSO BEGIN TO TURN OUT OF THE WEST/SOUTHWEST,
GENERALLY REMAINING LIGHT WITH GUSTS BELOW 20 MPH. AN EXCEPTION
WOULD BE THE COLUMBIA RIVER GORGE AND HOOD RIVER VALLEY, WHERE
WESTERLY GAP WINDS TUESDAY AFTERNOON COULD GUST TO 25-35 MPH
WITH A 30-50% CHANCE FOR MAXIMUM GUSTS EXCEEDING 40 MPH. -10
LONG TERM...WEDNESDAY THROUGH SATURDAY
WEDNESDAY INTO
THURSDAY WILL BE THE MORE SIGNIFICANT SOAKER DAYS AS THE
MAJORITY OF ENSEMBLE MEMBERS ARE SHOWING A SECOND, MUCH DEEPER
UPPER-LEVEL TROUGH DROPPING DOWN INTO THE PACIFIC NORTHWEST. THE
ASSOCIATED SURFACE FRONT SWINGS THROUGH ON WEDNESDAY, BRINGING
WIDESPREAD RAIN, COOLER TEMPERATURES, AND BREEZY WINDS FROM THE
SOUTH. IN ADDITION, THERE WILL BE A 10-20% CHANCE FOR
THUNDERSTORMS. CHANCES FOR EXCEEDING 1 INCH OF RAIN IN 48 HOURS
BETWEEN 5 AM WEDNESDAY TO 5 AM FRIDAY ARE HIGH (70-90%) ACROSS
NORTHWEST OREGON AND SOUTHWEST WASHINGTON, WITH THE HIGHEST
CHANCES ALONG THE COAST, COAST RANGE, AND CASCADES. CHANCES FOR
EXCEEDING 2 INCHES DURING THIS SAME TIMEFRAME ARE AROUND 30-50%
FOR THESE HIGHER TERRAIN FEATURES, AND 5-15% ALONG THE I-5
CORRIDOR. OROGRAPHIC ENHANCEMENT WILL PLAY A BIG ROLE WITH
PROVIDING HIGHER RAINFALL AMOUNTS TO THE MOUNTAINS.
THURSDAY AFTERNOON TO SATURDAY, THE UPPER-LEVEL TROUGH REMAINS
OVER THE PACIFIC NORTHWEST 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 WILL BE
ANOTHER 10-20% 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. -10
AVIATION...THROUGH 18Z MONDAY
VFR CONDITIONS FAVORED ACROSS
THE AIRSPACE THROUGHOUT THE PERIOD. LINGERING LOW CLOUDS LATE
THIS MORNING WILL MIX OUT, YIELDING LARGELY CLEAR SKIES BY 21Z
SUN. NORTH TO NORTHWEST WINDS WILL RISE TO 5-10 KT INLAND AND
10-15 KT WITH GUSTS AS HIGH AS 20-25 KT ALONG THE COAST AND IN
THE SOUTHERN WILLAMETTE VALLEY THIS AFTERNOON, THEN EASE TO 5 KT
OR LESS AFTER 03-06Z MON. LIGHT OFFSHORE (NORTH TO NORTHEAST)
FLOW OVERNIGHT WILL LIMIT CHANCES FOR MVFR CIGS BENEATH LOW
CLOUDS TO 20-30% ALONG THE COAST AND IN THE WILLAMETTE VALLEY.
KPDX AND APPROACHES...VFR CONDITIONS EXPECTED THROUGHOUT THE
PERIOD. LOW CLOUDS THIS MORNING WILL TEND TO CLEAR AND NORTHWEST
WINDS WILL BUILD TO 5-10 KT BY THE EARLY AFTERNOON. WINDS EASE
BELOW 5 KT TONIGHT, WITH LOW CHANCES, ONLY 10%, FOR MVFR CIGS IF
LOW CLOUD COVERAGE IS HIGHER THAN EXPECTED. -36
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, A GALE WATCH MAY BE ISSUED. 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.
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