255
FXUS66 KPQR 251105
AFDPQR
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE PORTLAND OR
405 AM PDT MON MAY 25 2026
SYNOPSIS
A MAJOR PATTERN SHIFT IS UNDERWAY EARLY THIS MORNING
AS A GULF OF ALASKA SYSTEM APPROACHES. EXPECT WIDESPREAD RAIN TO
SPREAD INLAND TODAY, ALONG WITH BREEZY WINDS AND A SHARP DROP
IN TEMPERATURES. SHOWERS PERSIST TUESDAY WITH A LOW-END (10-20%)
THUNDERSTORM CHANCE, THEN A GRADUAL RETURN TO WARMER AND DRIER
WEATHER MIDWEEK INTO NEXT WEEKEND.
DISCUSSION...TODAY THROUGH SATURDAY
EARLY THIS MONDAY
MORNING, THE REMAINING INFLUENCE OF LAST NIGHT’S RIDGE IS
QUICKLY GIVING WAY TO A BROAD UPPER LOW OVER THE NORTHEAST
PACIFIC. SATELLITE TRENDS SUPPORT AN EASTWARD PROGRESSION OF
THIS SYSTEM, AND THE ASSOCIATED COLD FRONT WILL BE THE DRIVER
FOR TODAY’S WETTER, COOLER WEATHER.
RAIN IS EXPECTED TO REACH THE COAST AROUND DAYBREAK, THEN
EXPAND INLAND THROUGH LATE MORNING INTO EARLY AFTERNOON. CURRENT
TIMING SUPPORTS ONSET ALONG THE COAST ROUGHLY 7-9 AM, WITH THE
I-5 CORRIDOR AND INTERIOR LOWLANDS SEEING STEADIER RAIN DEVELOP
AROUND 12-2 PM. WIDESPREAD CLOUD COVER WILL KEEP TEMPERATURES
WELL BELOW THIS PAST WEEKEND’S TEMPERATURES.
RAINFALL TOTALS THROUGH EARLY TUESDAY REMAIN IN A BENEFICIAL
BUT NON-HAZARDOUS RANGE. GUIDANCE SUPPORTS 48-HOUR AMOUNTS
(ROUGHLY 5 AM MONDAY TO 5 AM WEDNESDAY) AROUND 0.15 TO 0.80
INCHES, HEAVIEST ALONG THE COAST AND COAST RANGE. PROBABILITIES
FOR AT LEAST 0.25 INCH ARE ABOUT 35-75% ACROSS THE WILLAMETTE
VALLEY AND 70-95% ACROSS THE COAST/COAST RANGE/CASCADES. FOR
0.50 INCH OR MORE, ODDS ARE LOWER IN THE WILLAMETTE VALLEY
(AROUND 5-35%) BUT MUCH HIGHER FOR THE COAST AND COAST RANGE
(60-90%), WITH THE CASCADES GENERALLY 25-75%. THE BEST SIGNAL
FOR 1.0 INCH OR MORE REMAINS ALONG PORTIONS OF THE COAST FROM
FLORENCE NORTH TOWARD SEASIDE, WHERE PROBABILITIES RUN ABOUT
10-30%.
WINDS INCREASE AS THE FRONT PASSES, ESPECIALLY NEAR THE COAST
AND EXPOSED HEADLANDS. PROBABILITIES REMAIN HIGH FOR GUSTS AT OR
ABOVE 25 MPH ACROSS MUCH OF THE AREA (ROUGHLY 70-99%). GUSTS
EXCEEDING 30 MPH ARE MORE LIKELY ALONG THE COAST (ABOUT 60-90%)
THAN INLAND (15-30%), AND GUSTS AROUND 35 MPH OR HIGHER ARE
STILL MORE FAVORED ALONG THE COAST (30-60%) COMPARED TO INLAND
(5-10%). THESE WINDS ARE NOT EXPECTED TO MEET ADVISORY CRITERIA,
BUT COULD STILL BE DISRUPTIVE FOR TENTS, CANOPIES, AND
OTHER UNSECURED OUTDOOR ITEMS.
BY TUESDAY, THE UPPER LOW DROPS SOUTHEAST WITH SHOWERS
CONTINUING AND WINDS TURNING MORE SOUTHERLY ALOFT. THAT CHANGE
INCREASES INSTABILITY MODESTLY, AND A 10-20% CHANCE OF
THUNDERSTORMS REMAINS FOR THE WILLAMETTE VALLEY AND CASCADES
FROM LATE TUESDAY MORNING INTO TUESDAY EVENING.
FROM WEDNESDAY INTO NEXT WEEKEND, GUIDANCE FAVORS A DRYING AND
WARMING TREND AS WEAKER HIGH PRESSURE AND MORE ZONAL FLOW
RETURN. EVEN WITH THAT WARM-UP, DAYTIME HIGHS LIKELY STAY
SOMEWHAT COOLER THAN THE RECENT WARM SPELL, WITH ENSEMBLE
GUIDANCE SUGGESTING A 85-99% CHANCE TEMPERATURES REMAIN ON THE
COOLER SIDE RELATIVE TO THE WEEKEND (BELOW 80 DEGREES). THERE
ARE EARLY HINTS THAT THE RIDGE COULD WEAKEN AGAIN LATE WEEK AS
ANOTHER TROUGH APPROACHES THE NORTHEAST PACIFIC, BUT RECENT
ENSEMBLE GUIDANCE LOOKS TO TREND TOWARD THE TROUGH WEAKENING AND
THE RIDGE REMAINING OVER THE REGION. WHILE CONFIDENCE HAS
INCREASED REGARDING A TROUGH LATE WEEK, CONFIDENCE FOR THE
WEAKENING OF THIS UPCOMING MIDWEEK RIDGE HAS DECREASED AS THE
LATE WEEK TROUGH LOOKS SIGNIFICANTLY WEAKER.~12
AVIATION
CURRENTLY VFR INLAND AND ISOLATED LIFR CONDITIONS AT
THE COAST (MAINLY KONP) AS OF 11Z MON. A FRONTAL SYSTEM
WILL MOVE THROUGH THE AIRSPACE THIS MORNING AND AFTERNOON,
CURRENTLY LOCATED JUST OFF THE COAST. SPECIFICALLY, EXPECTING
THE FRONT TO BRING RAIN AND DETERIORATED CONDITIONS TO THE COAST
BY 14-16Z MON AND PERSISTING THROUGH THE TAF PERIOD. WITH RAIN
EXPECTED TO BECOME WEAKER AND SHOWERY BY 22-23Z MON FOR COASTAL
TERMINALS, CONDITIONS AT KTMK AND KAST MAY IMPROVE BACK TO VFR
AROUND THEN. AS FOR INLAND TERMINALS, THE FRONT WILL BRING RAIN
AND HIGH-END MVFR / LOW-END VFR CONDITIONS BY 20-22Z MON (10-30%
CHANCE OF MVFR CONDITIONS). WHILE RAIN WILL BECOME WEAKER AND
SHOWERY BY 01-03Z TUE, LOW CHANCES FOR MVFR CONDITIONS WILL
CONTINUE UNTIL AT LEAST 12Z TUE.
CURRENT SOUTHERLY WINDS WILL SHIFT A BIT MORE SOUTHWESTERLY BY
17-18Z MONDAY AS THE FRONT MOVES THROUGH THE AIRSPACE. EXPECT
CONTINUED WINDS AROUND 14-17 KT WITH GUSTS UP TO 20-25 KT AT
THE COAST UNTIL 03-06Z TUE, WHILE INLAND WILL SEE WINDS INCREASE
TO AROUND 10-14 KT WITH GUSTS UP TO 20 KT BETWEEN 17Z MON AND
03Z TUE. SOME AREAS WITHIN THE COLUMBIA RIVER GORGE MAY BE EVEN
WINDIER WITH SOME MODELS SUGGESTING AS HIGH AS 30 KT AT 3000
FT.
ADDITIONALLY, THERE IS A 15-30% CHANCE OF ISOLATED THUNDERSTORMS
AFTER 18Z MON, WITH MOST TERMINALS AT THE LOW END OF THIS
PROBABILITY RANGE. EXPECT AN ISOLATED THUNDERSTORM OR TWO RATHER
THAN WIDESPREAD THUNDERSTORMS WITH THIS SYSTEM.~12
KPDX AND APPROACHES...EXPECT VFR CONDITIONS THROUGH THE TAF
PERIOD WITH INCREASING SCT/BKN HIGH CLOUDS AS A FRONTAL SYSTEM
APPROACHES. AFFILIATED WITH THE FRONT, SOUTHERLY WINDS WILL
INCREASE WITH GUSTS UP TO 20 KT BETWEEN 17Z MON AND 03Z TUE.
CIGS WILL GRADUALLY FALL TO LOW-END VFR AFTER 20Z MON WITH
AROUND A 10-30% CHANCE OF MVFR CIGS. RAIN IN THE AREA WITH
GUSTY WINDS MAY TEMPORARILY REDUCE VIS AT TIMES. 15-20% CHANCE
OF ISOLATED THUNDERSTORMS AFTER 18Z MONDAY, WITH LOW CONFIDENCE
FOR ANYTHING WIDESPREAD. EXPECT MORE OF AN ISOLATED THUNDERSTORM
OR TWO.~12
MARINE
SOUTHERLY WINDS HAVE INCREASED SINCE LAST NIGHT, WITH NOW
WIDESPREAD GUSTS UP TO 30 KT ACROSS ALL WATERS AS THE FRONT
APPROACHES. PEAK WINDS ARE EXPECTED BETWEEN 5-11 AM THIS MORNING
WITH A 50-70% CHANCE FOR ISOLATED GALE FORCE GUSTS UP TO 35 KT
FOR THE INNER WATERS (FROM SHORE TO 10 NM OUT) NORTH OF CAPE
FOULWEATHER. AFTER 11 AM TODAY, WINDS TURN MORE WEST-
SOUTHWESTERLY BEHIND THE FRONT WITH GUSTS UP TO 25 KT. SMALL
CRAFT ADVISORIES ARE IN EFFECT UNTIL 5 PM MONDAY FOR ALL WATERS
INCLUDING THE COLUMBIA RIVER BAR. SEAS AROUND 6 TO 8 FT THROUGH
EARLY MONDAY MORNING.
FOLLOWING THE FRONTAL PASSAGE, A WESTERLY SWELL WILL MOVE IN A
BUILD SEAS ABOVE 13 FT (>90% CHANCE). THERE IS ALSO A 5-10% CHANCE
FOR SEAS EXCEEDING 20 FT TONIGHT INTO TUESDAY MORNING, WITH THE
HIGHEST CHANCES FOR THE OUTER WATERS BEYOND 30 NM OFFSHORE.
GIVEN THE POTENTIAL FOR SEAS BETWEEN 15-20 FT, THERE REMAINS A
HAZARDOUS SEAS WATCH FOR ALL WATERS INCLUDING THE COLUMBIA RIVER
BAR BETWEEN 5 PM TODAY AND 11 AM TUESDAY. SEAS SUBSIDE TO 10-12
FT BY TUESDAY EVENING AND GRADUALLY SUBSIDE INTO WEDNESDAY.
WILL ALSO NOTE THAT THERE IS A 10-20% CHANCE FOR THUNDERSTORMS
ACROSS THE WATERS TONIGHT. ANY PASSING THUNDERSTORMS MAY
PRODUCE LIGHTNING, BRIEF HEAVY DOWNPOURS THAT REDUCE VISIBILITY,
ERRATIC WINDS, AND/OR SMALL HAIL. ~12/10
PQR WATCHES/WARNINGS/ADVISORIES
OR...NONE.
WA...NONE.
PZ...SMALL CRAFT ADVISORY UNTIL 5 PM PDT THIS AFTERNOON FOR PZZ210-
251>253-271>273.
HAZARDOUS SEAS WATCH FROM THIS AFTERNOON THROUGH TUESDAY
MORNING FOR PZZ210-251>253-271>273.
WWW.WEATHER.GOV/PORTLAND
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