309
FXUS66 KPQR 211830 AAA
AFDPQR
AREA FORECAST DISCUSSION...UPDATED
NATIONAL WEATHER SERVICE PORTLAND OR
1129 AM PDT TUE OCT 21 2025
...UPDATED AVIATION DISCUSSION AND WATCHES/WARNINGS/ADVISORIES
SECTION...
SYNOPSIS
HIGH PRESSURE WILL BRING DRY AND CALM WEATHER WITH
MILD AFTERNOON TEMPERATURES TODAY. WEDNESDAY, A SERIES OF
FRONTAL SYSTEMS STEMMING FROM A BROAD LOW IN THE GULF OF ALASKA
WILL MOVE OVER THE REGION. WE ARE LOOKING AT A PROLONGED PERIOD
OF RAIN, WIND AND CASCADE SNOW. A TREND TOWARDS A MODERATE
ATMOSPHERIC RIVER (AR) ON FRIDAY WILL BE ACCOMPANIED BY GUSTY
SOUTH/SOUTHWESTERLY WINDS. SNOW LEVELS WILL BEGIN TO DROP OVER
THE WEEKEND WITH SNOW POSSIBLE ALONG THE PASSES.
SHORT TERM...NOW THROUGH MONDAY
A WEAKENING AREA OF HIGH
PRESSURE PERSISTS OVER THE REGION THROUGH TODAY. THIS WILL
MAINTAIN RELATIVELY BENIGN CONDITIONS WITH DAYTIME HIGHS IN THE
UPPER 50S TO UPPER 60S, WITH CLEAR SKIES AND LIGHT WINDS. THESE
CONDITIONS ARE FAVORABLE FOR FOG DEVELOPMENT ALONG THE COAST AND
ALONG THE I-5 CORRIDOR. ANY FOG DEVELOPMENT SHOULD CLEAR OUT
RIGHT AROUND SUNRISE.
AS WEDNESDAY APPROACHES, THE FIRST IN A SERIES OF FRONTAL
PASSAGES WILL APPROACHES THE REGION. THESE SYSTEMS ARE STEMMING
FROM A LARGE "PARENT" LOW THAT IS SLOWLY MOVING SOUTHWARD INTO
THE THE GULF OF ALASKA THROUGH THE LATTER PART OF THE WEEK.
THE FIRST FRONT WILL MOVE OVER NORTHWEST OREGON AND SOUTHWEST
WASHINGTON EARLY WEDNESDAY. THIS FIRST SYSTEM LOOKS TO BE THE
WEAKEST WITH MOST AREAS SEEING VERY LITTLE PRECIPITATION, WITH
THE HIGHEST PRECIPITATION TOTALS EXPECTED ALONG THE COAST.
A BREAK IN THE PRECIPITATION IS EXPECTED ON THURSDAY, BUT THAT
WILL BE SHORT LIVED, AS BY LATE THURSDAY/EARLY FRIDAY A
COMBINATION OF A FRONTAL PASSAGE FROM THE GULF OF ALASKA LOW
COMBINED WITH A MODERATE ATMOSPHERIC RIVER (AR) FROM THE
SOUTHWEST. EXPECT AMPLE PRECIPITATION, STRONG SOUTH TO
SOUTHWESTERLY WINDS, AND WARMER AIR BEFORE TRAILING COOLER AIR
MOVES IN ON FRIDAY. AS OF RIGHT NOW THERE IS STILL A WIDE RANGE
OF PROBABILITIES FOR BOTH WIND AND RAIN, BUT CURRENT
PRECIPITATION TOTALS FROM LATE THURSDAY/EARLY FRIDAY THROUGH
LATE SATURDAY NIGHT. INLAND AREAS SHOULD EXPECT 1.50-2.25
INCHES, THE COAST AND COAST RANGE 2.50-4.00 INCHES AND THE
CASCADES 2.50-3.75 INCHES. IMPACT WISE, RAIN HAS A LOWER
PROBABILITY OF ISSUES AS ACCUMULATION RATES ARE NOT HIGH ENOUGH
TO PRODUCE SIGNIFICANT URBAN FLOODING AT THIS TIME. HOWEVER,
GIVEN THE TIME OF YEAR AND FALLEN LEAVES, CLOGGED DRAINS/GUTTERS
COULD PRODUCE LOCALIZED ISSUES SUCH AS PONDING THAT COULD CAUSE
IMPACTS TO TRAFFIC. WINDS WILL BE ANOTHER CONCERN BUT ONE THAT
HAS SIGNIFICANTLY MORE VARIABILITY. THE COAST WILL SEE THE
HIGHEST WIND SPEEDS, ESPECIALLY ALONG THE BEACHES AND HEADLANDS.
ALONG COASTAL CITIES, WINDS COULD BE AS LOW AS 30 MPH, OR AS
HIGH AS 60 MPH (THE 10TH TO 90TH PERCENTILE). INLAND, GUSTS
COULD RANGE, BASED ON THE 10TH TO 90TH, BETWEEN 20 MPH TO NEARLY
50 MPH ON FRIDAY AFTERNOON INTO SATURDAY MORNING. THIS SPREAD
MAKES NARROWING DOWN ON AN EXACT FORECAST DIFFICULT. ULTIMATELY
THE RAIN COMBINED WITH WIND AND FULL LEAFED TREES COULD LEAD TO
DOWNED BRANCHES AND SOME HEAVIER TREES.
AS WE GET TO THE LATTER PART OF THE WEEK AND INTO THE WEEKEND,
LOWERING SNOW LEVELS WILL ALSO COME INTO PLAY. THE DETERMINISTIC
NBM SUGGESTS SNOW LEVELS WILL FALL TO 3500-4500 FEET BY SATURDAY
NIGHT, WHILE THE 10TH PERCENTILE SUGGESTS SNOW LEVELS DOWN TO
3000-3500 FEET (10% CHANCE OF OCCURRING). IN BOTH CASES, ACCUMULATING
SNOW WOULD OCCUR AT PASS LEVEL, RESULTING IN TRAVEL IMPACTS.
PRECIPITATION ALONG WITH THE LOWERED SNOW LEVELS IS EXPECTED TO
PERSIST THROUGH AT LEAST MONDAY MORNING. THIS WILL KEEP SNOW IN
THE FORECAST FOR ELEVATIONS ABOVE 4000 FT OR SO, WITH RAIN AT
LOWER ELEVATIONS. /42-27
AVIATION
WESTERLY FLOW ALOFT WITH A WEAK RIDGE OF HIGH
PRESSURE OVER THE REGION. THIS WILL BRING MOSTLY CLEAR SKIES
THROUGH THE TAF PERIOD WITH LIGHT, NORTHERLY WINDS. THESE
CONDITIONS WILL ALSO FAVOR FOG DEVELOPMENT, PARTICULARLY ACROSS
THE SOUTHERN WILLAMETTE VALLEY AND ALONG THE COAST. THIS IS
RESULTING IN A 15-30% PROBABILITY OF LIFR/IFR CONDITIONS
DEVELOPING BETWEEN 12Z-18Z TUESDAY, WHERE FOG DOES DEVELOP. ANY
LOWERED FLIGHT CONDITIONS THAT DO DEVELOP SHOULD LIFT AROUND
17Z-19Z TUESDAY. OTHERWISE, PREDOMINATELY VFR CONDITIONS EXPECTED.
KPDX AND APPROACHES...PREDOMINATELY VFR CONDITIONS EXPECTED. MAIN
EXCEPTION WILL BE FOR CHANCES OF FOG DEVELOPING BETWEEN 12Z-18Z
TUESDAY, WITH A 15-30% PROBABILITY OF OCCURRENCE. /42
MARINE
STEEP SEAS AND HAZARDOUS SEAS CONTINUE ACROSS ALL WATERS
THROUGH AT LEAST TUESDAY EVENING. SEAS CURRENTLY AROUND 10 TO 12
FEET AT 14 SECONDS BUT ARE EXPECTED TO BUILD TOWARDS TO 15 TO 18
FEET AT 16 TO 18 SECONDS THROUGH TUESDAY AFTERNOON, BEFORE BRIEFLY
SUBSIDING TOWARDS 10 TO 13 FT AT 15 SECONDS BY TUESDAY NIGHT.
THEREFORE, HAVE ADJUSTED THE HAZARDOUS SEAS WARNING ACROSS ALL
WATERS THROUGH LATE TONIGHT, FOLLOWED BY A SMALL CRAFT ADVISORY
THROUGH LATE WEDNESDAY MORNING.
AFTER A BRIEF PERIOD OF RELATIVELY CALMER CONDITIONS ON WEDNESDAY,
A VERY ACTIVE WEATHER PATTERN IS EXPECTED TO CONTINUE THURSDAY
THROUGH AT LEAST SATURDAY NIGHT. A DEEP LOW WILL DRAG A COLD FRONT
ACROSS ALL WATERS AND WILL RESULT IN A A PERIOD OF GALE FORCE,
POSSIBLY STORM FORCE SOUTHERLY WIND GUSTS STARTING THURSDAY
EVENING THROUGH AT LEAST LATE FRIDAY MORNING. PROBABILITIES FOR
GALE FORCE GUSTS ARE 40-70% WHILE THE PROBABILITIES FOR STORM
FORCE HAVE COME DOWN TO AROUND 20% FOR THE INNER WATERS ONLY. NOTE
THAT PROBABILITIES ARE HIGHEST OVER THE INNER WATERS DUE TO THE
POTENTIAL DEVELOPMENT OF A COASTAL JET DURING THAT TIME. THIS
SYSTEM WILL LIKELY PUSH SEAS TOWARDS 17 TO 19 FT, WITH A 10%
CHANCE FOR SEAS OVER 20 FT.
SEAS ARE EXPECTED TO REMAIN ELEVATED THROUGH THE WEEKEND AS A
SERIES OF SYSTEMS APPROACH THE REGION, PARTICULARLY SATURDAY
NIGHT INTO SUNDAY. /42
BEACH HAZARDS
RAZOR CLAM DIGGERS AT THE COAST WILL NEED TO
EXERCISE CAUTION FOR SNEAKER WAVES THIS WEEK, ESPECIALLY ON
TUESDAY AND WEDNESDAY WHEN A LONG PERIOD, WESTERLY SWELL WILL
BRING A HIGH THREAT FOR SNEAKER WAVES. SNEAKER WAVES CAN RUN UP
SIGNIFICANTLY FARTHER ON A BEACH THAN NORMAL, INCLUDING OVER
ROCKS, LOGS, AND JETTIES. SNEAKER WAVES CAN SUDDENLY KNOCK PEOPLE
OFF OF THEIR FEET AND QUICKLY PULL THEM INTO THE OCEAN WHICH MAY
LEAD TO SERIOUS INJURY OR DROWNING. CAUTION SHOULD BE USED WHEN IN
OR NEAR THE WATER. ALWAYS KEEP AN EYE ON THE WAVES, AND BE
ESPECIALLY WATCHFUL OF CHILDREN AND PETS. REMEMBER, NEVER TURN
YOUR BACK ON THE OCEAN. A BEACH HAZARDS STATEMENT IS IN EFFECT
ACROSS THE CENTRAL AND NORTHERN OREGON COAST AND THE SOUTH
WASHINGTON COAST TUESDAY MORNING THROUGH WEDNESDAY AFTERNOON TO
HELP MESSAGE THIS THREAT.
PQR WATCHES/WARNINGS/ADVISORIES
OR...NONE.
WA...NONE.
PZ...HAZARDOUS SEAS WARNING UNTIL 2 AM PDT WEDNESDAY FOR PZZ210-
251>253-271>273.
SMALL CRAFT ADVISORY FROM 2 AM 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