914
FXUS66 KPQR 012133
AFDPQR
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE PORTLAND OR
233 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 18Z WEDNESDAY
LATEST TERMINAL OBSERVATIONS
SHOW LARGELY MVFR CIGS INLAND WITH LOW-END VFR CIGS ALONG THE
COAST. CIGS LIFTING TO 4-6 KFT IS EXPECTED AT ALL TERMINALS AS
DIURNAL MIXING FAVORS MORE WIDESPREAD VFR INTO THIS AFTERNOON.
CHANCES FOR FURTHER MVFR CIGS INCREASE TO 50% OR GREATER AFTER
00-03Z WED AT COASTAL TERMINALS, WHILE LOWERING CIGS SHOULD
REMAIN AT LOW-END VFR LEVELS INLAND, WITH 10-20% CHANCES OF MVFR
AFTER 06Z WED. THE CHANCES FOR SCATTERED RAIN SHOWERS ALSO TEND
TO INCREASE AFTER 00Z WED, THOUGH CONFIDENCE IN THE OCCURRENCE
AND PLACEMENT OF THESE SHOWERS IS TOO LOW TO INCLUDE IN TAFS AT
THIS POINT; ANY SHOWERS THAT DO AFFECT A TERMINAL WILL BE LIGHT
WITH VERY BRIEF OR LIMITED IMPACTS. SOUTH-SOUTHWEST WINDS WILL
RISE TO 8-12 KT INLAND AND 10-15 KT WITH GUSTS OF 20-25 KT ALONG
THE COAST THROUGH THIS AFTERNOON.
A MORE POTENT FRONTAL BOUNDARY LOOKS TO APPROACH THE REGION LATE
IN THE PERIOD, BRINGING WIDESPREAD LIGHT TO MODERATE RAIN
BEGINNING BY 12-18Z WED. THERE IS HIGH CONFIDENCE IN FURTHER
MVFR CIGS AT COASTAL TERMINALS AS RAIN BEGINS, WHILE VFR CIGS
ARE MORE LIKELY TO PREVAIL THROUGH AT LEAST 18Z WED INLAND. MVFR
VIS IS ALSO MORE LIKELY ALONG THE COAST FOLLOWING PRECIPITATION
ONSET. WINDS WILL INCREASE ACROSS THE AIRSPACE AS THE BOUNDARY
NEARS, REACHING 15-20 KT WITH GUSTS OF 25-30 KT ALONG THE COAST
AND 10-15 KT AT INLAND TERMINALS.
KPDX AND APPROACHES...DIURNAL MIXING WILL FAVORING CURRENT MVFR
CIGS LIFTING TO VFR AT 4-5 KFT THIS AFTERNOON. VFR CONDITIONS
ARE THEN FAVORED TO PREVAIL THROUGH THE REMAINDER OF THE PERIOD,
ALTHOUGH CHANCES FOR MVFR CIGS INCREASE LATE IN THE PERIOD,
AFTER 15Z WED, AS STEADY RAIN ARRIVES FROM THE WEST. SOUTH-
SOUTHWEST WINDS CONTINUE THROUGH THE PERIOD, BUT INCREASING
TOWARD 10-12 KT AS THE FRONTAL BOUNDARY APPROACHES WEDNESDAY
MORNING. -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
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