758
FXUS66 KPQR 111854 AAA
AFDPQR
AREA FORECAST DISCUSSION...UPDATED
NATIONAL WEATHER SERVICE PORTLAND OR
1154 AM PDT THU SEP 11 2025
UPDATED AVIATION DISCUSSION.
SYNOPSIS
MORNING CLOUDS ACROSS THE REGION SHOULD BEGIN TO
BREAK OUT THIS AFTERNOON. THERE IS ALSO A 15-25% CHANCE FOR
THUNDERSTORMS FROM SANTIAM PASS INTO THE LANE COUNTY CASCADES
THIS AFTERNOON. WARMER CONDITIONS WITH SUNNIER SKIES EXPECTED
TOMORROW THROUGH SATURDAY AFTERNOON. THE NEXT FRONTAL SYSTEM
ARRIVES SATURDAY NIGHT TO SUNDAY, RETURNING WIDESPREAD RAIN.
CONDITIONS DRY AND WARM UP EARLY NEXT WEEK, WITH POTENTIAL FOR
LIGHT OFFSHORE WINDS.
SHORT TERM...NOW THROUGH SATURDAY NIGHT
SATELLITE IMAGERY
AND SURFACE OBSERVATIONS AS OF EARLY THURSDAY MORNING DEPICT
WIDESPREAD STRATUS ACROSS NORTHWEST OREGON AND SOUTHWEST
WASHINGTON AS THE LOW-LEVEL ATMOSPHERE REMAINS MOIST WITH LIGHT
ONSHORE FLOW. WE SHOULD BEGIN TO SEE MORE CLOUD BREAKS THIS
AFTERNOON AS DAYTIME HEATING PROGRESSES. EXPECT SEASONABLE
TEMPERATURES TODAY WITH AFTERNOON HIGHS IN THE MID 70S ACROSS
INTERIOR VALLEYS AND LOW 60S ALONG THE COAST.
ANOTHER WEATHER FEATURE TODAY IS THE BROAD UPPER LEVEL LOW
CENTERED OVER THE GREAT BASIN THAT WILL CONTINUE TO BRING WRAP
AROUND MOISTURE INTO THE AREA FROM THE NORTHEAST. WHILE MOST
PLACES WEST OF THE CASCADES ARE EXPECTED TO BE DRY TODAY, THERE
REMAINS A 20-60% CHANCE OF SHOWERS ACROSS THE CASCADES AND
FOOTHILLS THIS AFTERNOON, WITH THE HIGHEST CHANCES AS YOU MOVE
FURTHER SOUTH INTO THE LINN AND LANE COUNTY CASCADES. THERE IS
ALSO A 15-25% CHANCE FOR THUNDERSTORMS THIS AFTERNOON FROM
SANTIAM PASS SOUTHWARD INTO THE LANE COUNTY CASCADES. ANY
PASSING THUNDERSTORMS MAY BRING LIGHTNING AND BRIEF HEAVY RAIN.
CHANCES FOR SHOWERS AND THUNDERSTORMS DIMINISH AFTER 5-7 PM
TODAY.
SHORTWAVE RIDGING RETURNS TO THE REGION ON FRIDAY, LEADING TO
DECREASING CLOUDS AND MORE SUNNY SKIES. TEMPERATURES ARE
FORECAST SLIGHTLY WARMER, WITH UPPER 70S ACROSS INTERIOR
VALLEYS AND MID 60S ALONG THE COAST. HIGH PRESSURE WITH SUNNY
SKIES CONTINUES THROUGH SATURDAY AFTERNOON, WITH TEMPS WARMING
UP INTO THE LOW 80S ACROSS INTERIOR VALLEYS. BY SATURDAY
EVENING, THE SHORTWAVE RIDGE WILL PROGRESS EASTWARD AS THE NEXT
FRONTAL SYSTEM APPROACHES. CLOUDS AND CHANCES FOR WIDESPREAD
RAIN RETURN SATURDAY NIGHT, WITH RAIN BEGINNING AT THE COAST AS
EARLY AS 5-8 PM SAT. WINDS ACROSS THE REGION ALSO TURN MORE
WEST-SOUTHWESTERLY AHEAD OF THE FRONT. -ALVIZ
LONG TERM...SUNDAY THROUGH THURSDAY
WIDESPREAD RAIN RETURNS
ACROSS NORTHWEST OREGON AND SOUTHWEST WASHINGTON AS OUR FIRST
FALL-LIKE FRONTAL SYSTEM SWINGS THROUGH THE REGION. LREF
ENSEMBLE GUIDANCE (ENS/GEFS/GEPS) ARE IN GENERAL AGREEMENT (80%
CHANCE) THAT THE FRONT WILL MOVE THROUGH SATURDAY NIGHT INTO
SUNDAY MORNING, WHICH IS WHEN THE BULK OF THE RAIN IS EXPECTED.
THE NAM LOOKS LIKE AN OUTLIER, BRINGING THE FRONT FURTHER SOUTH
INTO SOUTHERN OREGON AND NORTHERN CALIFORNIA. IF THIS SCENARIO
WERE TO OCCUR, THEN WE WOULD END UP MUCH DRIER.
WHILE THE LREF ENSEMBLES ARE IN GENERAL AGREEMENT WITH THE
TIMING OF THE FRONT, THERE IS STILL UNCERTAINTY WITH THE
MAGNITUDE OF THE FRONT, AND THUS TOTAL RAINFALL AMOUNTS. THE
NBM 75TH PERCENTILE FOR 24 HOUR RAINFALL ENDING 5 PM SUNDAY IS
AROUND 1-1.5" ALONG THE COAST AND 0.60-0.80" ACROSS INTERIOR
VALLEYS, WHILE THE NBM 25TH PERCENTILE IS AROUND 0.30-0.50"
ALONG THE COAST AND 0.10-0.20" ACROSS INTERIOR VALLEYS.
CURRENTLY, THE GEFS ENSEMBLE IS WANTING TO BRING IN THE HIGHER-
END RAINFALL AMOUNTS WHILE THE ENS/GEPS ENSEMBLES ARE SUGGESTING
LOWER AMOUNTS. WILL CONTINUE TO MONITOR HOW THIS EVOLVES IN THE
NEXT DAY OR SO. FOR NOW, WE CAN GENERALLY SAY THAT SUNDAY IS
LOOKING TO BE WETTER AND COOLER. BY LATE SUNDAY AFTERNOON, THE
FRONT WILL WEAKEN AND RAIN WILL GRADUALLY TAPER OFF SUNDAY NIGHT
INTO EARLY MONDAY MORNING.
MONDAY LOOKS DRIER (75% CHANCE) AS SHORTWAVE RIDGING RETURNS TO
THE REGION AND THE AFOREMENTIONED SYSTEM PROGRESSES EASTWARD.
HOWEVER, AROUND 25% OF ENSEMBLE MEMBERS (MAINLY FROM THE GEFS)
KEEP TROUGHING OVER THE PACIFIC NORTHWEST ON MONDAY, SO IF THIS
WERE TO OCCUR WE MAY MAINTAIN COOLER AND POTENTIALLY WETTER
CONDITIONS FOR AN EXTRA DAY. BY TUESDAY, THERE IS HIGH AGREEMENT
AMONG ENSEMBLE MEMBERS THAT ABOVE-AVERAGE 500 MB HEIGHTS
RETURN, REBOUNDING TEMPERATURES INTO THE LOW 80S ACROSS INTERIOR
VALLEYS WITH SUNNY SKIES. WEDNESDAY LOOKS SIMILAR TO TUESDAY,
HOWEVER, 25% OF ENSEMBLE MEMBERS DO ALSO SHOW A WEAK FRONT
APPROACHING THE PACIFIC NORTHWEST.
ONE LAST THING TO NOTE ABOUT MONDAY NIGHT TO WEDNESDAY, A
THERMAL TROUGH DEVELOPS ACROSS WESTERN OREGON WITH HIGH
PRESSURE EAST OF THE CASCADES, LEADING TO AN OFFSHORE FLOW
PATTERN. THESE OFFSHORE WINDS EARLY NEXT WEEK ARE NOT LOOKING
PARTICULARLY STRONG AT THIS POINT, BUT WILL BE SOMETHING TO
MONITOR IN THE COMING DAYS. -ALVIZ
AVIATION
PREDOMINATELY MVFR CONDITIONS PERSIST ACROSS THE AREA
LATE THIS MORNING. EXPECTING MVFR CIGS TO PERSIST ALONG THE COAST
WHILE CLOUD COVER BEGINS TO SCATTER OUT INLAND EARLY THIS
AFTERNOON BETWEEN 20-23Z. COULD SEE PATCHES LINGER A BIT PAST THAT
BUT GENERALLY EXPECTING VFR CONDITIONS TO DEVELOP THROUGHOUT THE
WILLAMETTE VALLEY. A BRIEF BREAK IN THE CLOUDS IS POSSIBLE ALONG
THE COAST AROUND 23Z THU TO 02Z FRI BEFORE STRATUS BUILDS BACK IN.
COULD SEE MVFR CIGS INLAND BEGINNING AROUND 10-12Z FRI WITH A
40-60% CHANCE THROUGH 17-19Z FRI. WINDS REMAIN LIGHT AND VARIABLE,
GENERALLY LESS THAN 10 KTS.
THERE REMAINS A 15-30% PROBABILITY FOR SHOWERS AND A 10-20%
PROBABILITY FOR THUNDERSTORMS OVER THE CASCADES AND CASCADE
FOOTHILLS FROM 12Z THURSDAY THROUGH 06Z FRIDAY. THERE IS LESS
THAN 10% PROBABILITY THAT A THUNDERSTORM MOVES WESTWARD INTO THE
WILLAMETTE VALLEY.
KPDX AND APPROACHES...MVFR CONDITIONS HOLDING STEADY BUT THE CLOUD
DECK SEEMS TO BE RISING SLOWLY. GUIDANCE SUGGESTS CLOUDS BREAK UP
AND VFR CONDITIONS RETURN AROUND 20Z BUT GIVEN THE TREND, LIKELY
LATER AROUND 23Z. VFR CONDITIONS IN THE EVENING WITH ANOTHER
MARINE PUSH EXPECTED AROUND 10-12Z FRI. WEST TO NORTHWESTERLY
WINDS LESS THAN 10 KTS. -BATZ/HEC
MARINE
HIGH PRESSURE OVER THE WATERS WILL MAINTAIN NORTHERLY
TO NORTHWESTERLY WINDS WITH GUSTS LESS THAN 15 KT THROUGH
THURSDAY. WINDS BECOME MORE VARIABLE ACROSS THE WATERS ON FRIDAY
AHEAD OF THE NEXT SYSTEM, BUT STILL REMAIN LIGHT. EXPECT SEAS
AT 5-6 FT AT 13-14 SEC THURSDAY TO FRIDAY WITH A WEST-
NORTHWESTERLY SWELL.
A LOW PRESSURE SYSTEM MOVES THROUGH THE WATERS THIS WEEKEND. A
FRONT ASSOCIATED WITH THIS LOW WILL WEAKEN AS IT MOVES ACROSS
THE WATERS SATURDAY AND SUNDAY. THE WINDS WILL SHIFT SOUTHERLY
AHEAD OF THE FRONT ON SATURDAY, THEN NORTHERLY WITH AND BEHIND
THE FRONT BY SUNDAY AFTERNOON. PROBABILITIES FOR OBSERVING WIND
GUSTS OF 21 KT OR GREATER (SMALL CRAFT CONDITIONS) ACROSS THE
WATERS IN A 24 HOUR PERIOD ON SATURDAY INTO SUNDAY RANGE FROM
30-60%, HIGHEST ACROSS THE OUTER WATERS. HOWEVER, 1-HOUR
PROBABILITIES FOR SMALL CRAFT GUSTS ARE ONLY 15-30%, SUGGESTING
THAT ANY SMALL CRAFT WIND GUSTS MAY BE BRIEF AND NOT AS
FREQUENT/LONG-LASTING. GIVEN THE LEAD TIME AND SOME UNCERTAINTY
WITH THE EXACT LOW TRACK, WILL CONTINUE TO HOLD OFF ON ISSUING
ANY PRODUCTS FOR NOW. SEAS ARE FORECAST AROUND 6-7 FEET AT 10-12
SEC THROUGH SATURDAY. A NORTHWEST SWELL IS EXPECTED TO MOVE
INTO THE WATERS ON SUNDAY BRINGING WAVES OF 9-12 FEET AT 10-12
SECONDS WHICH WOULD SUPPORT STEEP, HAZARDOUS SEAS FOR SOME TIME.
PQR WATCHES/WARNINGS/ADVISORIES
OR...NONE.
WA...NONE.
PZ...NONE.
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