091
FXUS66 KPQR 012345
AFDPQR
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE PORTLAND OR
445 PM PDT TUE SEP 1 2026
SYNOPSIS
AN UNUSUALLY STRONG SERIES OF SYSTEMS, BY EARLY
SEPTEMBER STANDARDS, TAKES AIM AT THE PACIFIC NORTHWEST FOR THE
MIDDLE OF THE WEEK. THESE SYSTEMS LOOK TO BRING WIDESPREAD
RAINFALL, LOCALLY BREEZY/GUSTY WINDS, AND A 15-30% CHANCE FOR
POP-UP THUNDERSTORMS, WITH HIGHER CHANCES ON THURSDAY.
CONDITIONS TREND SLIGHTLY DRIER BY LATE THURSDAY/FRIDAY AND
CONTINUE INTO THE WEEKEND. HOWEVER, COOLER THAN NORMAL
TEMPERATURES AND SHOWER CHANCES PERSIST.
SHORT TERM...NOW THROUGH THURSDAY NIGHT
CONDITIONS ACROSS
THE AREA HAVE TRANSITIONED FROM WARM AND SUNNY YESTERDAY TO MUCH
COOLER AND CLOUDY TODAY AS AN UPPER LEVEL LOW ENTERS THE
PICTURE. LOW AND MID LEVEL CLOUDS COVERING THE AREA HAVE
PROMPTED A FEW REPORTS OF DRIZZLE OR LIGHT RAIN WHICH IS A GOOD
SIGN THAT THE ATMOSPHERE IS MOIST AND PRIMED FOR A BETTER SHOT
OF RAIN TOMORROW. TEMPERATURES ACROSS THE INTERIOR LOWLANDS TOP
OUT IN THE LOW 70S, LOW TO MID 60S ALONG THE COAST AND UPPER 50S
TO LOW 60S IN THE CASCADES EXPECTED TODAY. WEST TO SOUTHWEST
WINDS WITH GUSTS GENERALLY LESS THAN 20 MPH EXCEPT IN THE
WESTERN COLUMBIA RIVER GORGE WHERE GUSTS UP TO 30-40 MPH ARE
POSSIBLE.
TOMORROW WILL BE MORE EVENTFUL AS A MUCH STRONGER UPPER LEVEL LOW
DROPS SOUTH ALONG THE WESTERN CANADA COAST, TOWARD THE PACNW.
CONDITIONS WILL TREND MUCH WETTER, COOLER, AND WINDIER THROUGH THE
DAY AS THE ASSOCIATED SURFACE LOW AND COLD FRONT IMPACT OR AND
WA. RAIN IS EXPECTED TO REACH THE COAST LATE TONIGHT INTO EARLY
WEDNESDAY MORNING, REACHING THE INTERIOR LOWLANDS AND CASCADES
BY MID-MORNING. SOUTHERLY WINDS ALSO INCREASE DURING THIS TIME
WITH THE STRONGEST WINDS EXPECTED ALONG THE COAST, MOST LIKELY
BETWEEN 35-45 MPH BUT THERE IS A 20-30% CHANCE FOR ISOLATED
GUSTS OF 55 MPH OR GREATER THROUGH EARLY WEDNESDAY AFTERNOON.
WHILE WIND GUSTS ARE NOT EXPECTED TO REACH WARNING CRITERIA
ALONG THE COAST, THIS WILL BE THE STRONGEST WINDS OBSERVED IN
SEVERAL MONTHS SO IT IS POSSIBLE TREES OR BRANCHES THAT HAVE
WEAKENED OR DIED MAY COME LOSE WITH THESE WINDS. INLAND GUSTS
WILL PEAK AROUND 25-30 MPH WITH ISOLATED GUSTS UP TO 35 MPH WITH
LITTLE TO NO IMPACT EXPECTED. THIS SYSTEM WILL BRING THE MOST
SIGNIFICANT WIDESPREAD RAINFALL SINCE THE SPRING WITH SOLID
CHANCES FOR 48 HOUR RAINFALL TOTALS TO REACH 1 INCH OR GREATER
BY FRIDAY MORNING. MOST OF THE FORECAST AREA HAS AN 80% CHANCE
OR GREATER FOR 1 INCH OR MORE FROM 5 AM WEDNESDAY TO 5 AM
FRIDAY WITH SLIGHTLY LOWER CHANCES ACROSS THE NORTHERN
WILLAMETTE VALLEY AND PORTLAND METRO AROUND 60-70%. CHANCES FOR
2 INCHES OR MORE DURING THE SAME TIME FRAME ARE 20-30% AND ARE
CONFINED TO THE COAST AND COAST RANGE ALONG WITH THE SOUTHWEST
WA CASCADES. THERE IS ALSO A SLIGHT CHANCE FOR EMBEDDED
THUNDERSTORMS TOMORROW AFTERNOON, MAINLY ACROSS THE COAST RANGE,
WILLAMETTE VALLEY AND PORTLAND METRO. TEMPERATURES WILL ALSO
DROP INTO THE MID 60S FOR MOST LOCATIONS AND 50S FOR THE HIGHER
TERRAIN IN THE COAST RANGE AND CASCADES.
THERE A RELATIVE LULL IN PRECIPITATION IS EXPECTED WEDNESDAY
EVENING INTO THE OVERNIGHT WITH SCATTERED SHOWERS. PRECIPITATION
WILL INCREASE LATER THURSDAY MORNING INTO THE AFTERNOON AS THE
SURFACE LOW CONTINUES TO TRACK ALONG THE WA THEN OR COASTS. IN
THE POST FRONTAL ENVIRONMENT, SHOWER ACTIVITY WILL INCREASE
ALONG WITH A BETTER CHANCE FOR THUNDERSTORMS ACROSS THE ENTIRE
AREA. CAPE IS EXPECTED TO BE BETWEEN 100-200 J/KG DURING THE
AFTERNOON ALONG WITH COOLER TEMPERATURES IN THE UPPER LEVELS
WILL SUPPORT A 20-30% CHANCE FOR THUNDERSTORMS. THE SHEAR
ENVIRONMENT LOOKS POOR AND ISN'T EXPECTED TO SUPPORT LONG LIVED
CELLS, JUST SHORT LIVED STORMS CAPABLE OF SOME LIGHTNING, GUSTY
WINDS AND SMALL HAIL. IN ADDITION, COLD AIR ALOFT WILL ALSO PUT
INTO PLAY THE POTENTIAL DEVELOPMENT OF COLD CORE FUNNEL CLOUDS.
-19
LONG TERM...FRIDAY THROUGH TUESDAY
CHANCES FOR SHOWERS AND
THUNDERSTORMS CONTINUE INTO FRIDAY AND THE WEEKEND AS THE UPPER
LEVEL LOW WEAKENS BUT REMAINS OVERHEAD. CAPE WILL BE ON THE
LOWER SIDE, AROUND 100 J/KG DURING EACH AFTERNOON FRIDAY THROUGH
SUNDAY. TEMPERATURES DO TREND UPWARD FRIDAY THROUGH SUNDAY BACK
INTO THE MID 70S DURING THE WEEKEND ACROSS THE INTERIOR AS
CLOUD COVER BECOMES MORE BROKEN AND LESS OVERCAST. DRIER, MORE
BENIGN CONDITIONS ARE EXPECTED TO RETURN EARLY NEXT WEEK AS
SHORTWAVE RIDGING DEVELOPS ACROSS THE PACNW. -19
AVIATION...THROUGH 00Z THURSDAY
LARGELY VFR CONDITIONS
CONTINUE ACROSS THE AIRSPACE WITH CIGS OF 4-6 KFT AHEAD OF AN
APPROACHING FRONTAL SYSTEM EXPECTED TO BRING WIDESPREAD RAIN AND
CIG/VIS RESTRICTIONS TONIGHT INTO WEDNESDAY. WHILE LIGHT RAIN
SHOWERS MAY BEGIN IN THE VICINITY OF COASTAL TERMINALS WHEN
CHANCES FOR MVFR CIGS EXCEED 50% AFTER 06-09Z WED, MORE
WIDESPREAD STEADY RAIN WILL HOLD OFF UNTIL 12-14Z WED AT THE
COAST AND THEN REACH INLAND TERMINALS BY 15-17Z WED. MVFR/IFR
CIGS ARE LIKELY TO PERSIST WITH MVFR VIS WHILE RAIN CONTINUES
ALONG THE COAST, WHILE INLAND TERMINALS WILL INITIALLY MAINTAIN
VFR VIS/CIGS UNTIL CHANCES FOR MVFR VIS/CIGS REACH 60-75% AFTER
21Z WED. CONDITIONS MAY BEGIN TO IMPROVE ALONG THE COAST LATE IN
THE PERIOD AS STEADY RAIN TRANSITIONS TO RAIN SHOWERS BEHIND
THE FRONTAL BOUNDARY LATE IN THE PERIOD.
SOUTH WINDS WILL STEADILY INCREASE THIS EVENING AND OVERNIGHT AS
THE FRONTAL BOUNDARY APPROACHES. ALONG THE COAST, 10-15 KT WINDS
WITH GUSTS TO 20 KT THIS EVENING WILL BUILD TO 15-20 KT WITH
GUSTS OF 25-30 KT BY EARLY WEDNESDAY MORNING, BEFORE EASING
SLIGHTLY AND VEERING OUT OF THE SOUTHWEST BEHIND THE BOUNDARY.
INLAND, 5-10 KT WINDS THIS EVENING WILL RISE TO 10-15 KT WITH
GUSTS NEAR 20 KT BY WEDNESDAY MORNING.
KPDX AND APPROACHES...VFR CONDITIONS FAVORED TO PREVAIL THROUGH
MUCH OF THE PERIOD. STEADY RAIN ARRIVES FROM THE WEST AFTER 15Z,
WITH CHANCES FOR MVFR VIS/CIGS INCREASING TO 60-70% AS RAIN
CONTINUES LATE IN THE PERIOD, AFTER 18-21Z WED. WINDS CONTINUE
OUT OF THE SOUTH TO SOUTHWEST, BUT INCREASE OVERNIGHT TO 10-15
KT WITH GUSTS NEAR 20 KT AS THE FRONTAL BOUNDARY APPROACHES
WEDNESDAY. -36
MARINE
AN ACTIVE WEATHER PATTERN CONTINUED THROUGH THE
MIDDLE OF THIS WEEK. A BROAD AREA OF LOW PRESSURE DROPPING FROM
THE GULF OF ALASKA TOWARD THE OREGON AND WASHINGTON COASTS WILL
DRIVE A STRONG FRONTAL BOUNDARY EASTWARD OVER THE WATERS ON
WEDNESDAY, WHICH WILL SEE STRENGTHENING WINDS AND BUILDING SEAS
ACROSS THE WATERS. SOUTH TO SOUTHWEST WINDS WILL REACH 30-35 KT
WITH FREQUENT GUSTS OF 40-45 KT FROM EARLY WEDNESDAY MORNING
(3-5 AM PDT) UNTIL THE EARLY AFTERNOON BEYOND 10 NM OF THE COAST
AND UNTIL THE MID- AFTERNOON WITHIN 10 NM OF THE COAST
INCLUDING THE COLUMBIA RIVER BAR. THE STRONGEST GUSTS WILL MOST
LIKELY OCCUR BETWEEN 8 AM AND NOON PDT BEYOND 30 NM FROM THE
COAST, AND BETWEEN 10 AM AND 3 PM WITHIN 30 NM. WHILE NOT
EXPECTED TO BE PERSISTENT OR WIDESPREAD, THERE ARE 20-40%
CHANCES OF ISOLATED STORM-FORCE GUSTS WITHIN 20 NM AS THE FRONT
IMPINGES ON THE COAST WEDNESDAY AFTERNOON. GALE WARNINGS
THEREFORE REMAIN IN EFFECT FROM 11 PM PDT THIS EVENING UNTIL 5
PM PDT WEDNESDAY ACROSS THE WATERS.
SEAS WILL REMAIN LARGELY WIND-DRIVEN AHEAD OF THE FRONTAL
PASSAGE, RISING TO 10-13 FT DURING THE DAYLIGHT HOURS ON
WEDNESDAY. BEHIND THE BOUNDARY, A WEST-NORTHWEST SWELL OF 7-9 FT
WILL ARRIVE, YIELDING SEAS AROUND 10 FT THROUGH MUCH OF THURSDAY.
THESE STEEP SEAS MAY REQUIRE SMALL CRAFT OR HAZARDOUS SEAS ALERTS
IF CONFIDENCE IN THEIR TIMING, OCCURRENCE, AND PERSISTENCE
INCREASES. THERE WILL ALSO BE 15-30% CHANCES FOR ISOLATED TO
SCATTERED THUNDERSTORMS ON THURSDAY, WHICH WILL BE CAPABLE OF
PRODUCING GUSTY AND ERRATIC WINDS, SMALL HAIL, AND LIGHTNING.
WHILE RELATIVELY ACTIVE WEATHER WITH LINGERING RAIN SHOWERS WILL
CONTINUE INTO THE WEEKEND, MARINE CONDITIONS WILL TEND TO IMPROVE
AS WINDS AND SEAS EASE IN THE LATTER HALF OF THE WORKWEEK. FAIRLY
BENIGN WINDS OF 5-15 KT AND SEAS OF 4-6 FT ARE EXPECTED BY THE
WEEKEND AND INTO EARLY NEXT WEEK. -36
PQR WATCHES/WARNINGS/ADVISORIES
OR...NONE.
WA...NONE.
PZ...GALE WARNING FROM 11 PM THIS EVENING TO 5 PM PDT WEDNESDAY FOR
PZZ210-251>253-271>273.
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