766
FXUS66 KPQR 121217
AFDPQR
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE PORTLAND OR
417 AM PST WED NOV 12 2025
SYNOPSIS
RELATIVELY CALM WEATHER CONDITIONS CONTINUES THIS
MORNING AHEAD OF THE NEXT SYSTEM. COULD SEE SOME LIGHT SHOWERS
THIS AFTERNOON, BUT MOST PLACES REMAIN DRY. TONIGHT, A COLD
FRONT WILL PUSH THROUGH THE AREA, RETURNING WIDESPREAD RAIN.
SNOW LEVELS FALL THURSDAY INTO EARLY FRIDAY, RETURNING CHANCES
FOR ACCUMULATING, SUB-ADVISORY SNOW ACROSS THE CASCADE PASSES.
THE ACTIVE AND UNSETTLED PATTERN IS EXPECTED TO PERSIST THROUGH
THE WEEKEND AND INTO EARLY NEXT WEEK.
DISCUSSION...NOW THROUGH TUESDAY
SATELLITE IMAGERY AS OF
EARLY WEDNESDAY MORNING DEPICTS MID TO HIGH LEVEL CLOUD COVER
ACROSS THE REGION AHEAD OF THE NEXT SYSTEM. THERE IS DENSE FOG
BEING OBSERVED IN THE SOUTHERN WILLAMETTE VALLEY THIS MORNING
BASED ON WEBCAMS AND OBSERVATIONS AT THE KEUG (EUGENE) ASOS.
THEREFORE, A DENSE FOG ADVISORY HAS BEEN ISSUED FOR THE LANE
COUNTY LOWLANDS UNTIL 10 AM THIS MORNING. PATCHY DENSE FOG IS
POSSIBLE ACROSS OTHER CENTRAL/SOUTHERN WILLAMETTE VALLEY
LOCATIONS INCLUDING CORVALLIS AND ALBANY. IF YOU'LL BE COMMUTING
IN THE FOG THIS MORNING, MAKE SURE TO SLOW DOWN, USE LOW BEAM
HEADLIGHTS, AND LEAVE PLENTY OF DISTANCE AHEAD OF YOU. ANY FOG
THIS MORNING SHOULD LIFT BY 10-11 AM AS MIXING INCREASES DUE TO
DAYTIME HEATING AND THE INCOMING SYSTEM.
WEATHER SHOULD REMAIN BENIGN THIS MORNING AHEAD OF THE NEXT
SYSTEM. THIS AFTERNOON, A WEAK WARM FRONT ASSOCIATED WITH A LOW
PRESSURE SYSTEM IN THE NE PACIFIC WILL LIFT OVER NORTHWEST
OREGON AND SOUTHWEST WASHINGTON. THIS COULD POTENTIALLY BRING
LIGHT SHOWERS TO THE COAST AS BY 10 AM-1 PM WED AND ACROSS THE
WILLAMETTE VALLEY BY 1-2 PM WED. GIVEN WE'VE BEEN DRY THE LAST
FEW DAYS, IT MAY TAKE SOME TIME FOR THE ATMOSPHERE TO SATURATE;
THUS, MANY PLACES COULD STAY DRY THIS AFTERNOON. REFS GUIDANCE
SUGGESTS ONLY A 5-15% CHANCE FOR MEASURABLE RAIN (>0.01") FOR
COASTAL LOCATIONS SOUTH OF TILLAMOOK AND INLAND LOCATIONS SOUTH
AND EAST OF LONGVIEW FROM 12-6 PM TODAY. THE HIGHEST CHANCES
(20-30%) ARE ALONG THE NORTH OREGON AND SOUTH WASHINGTON COASTS.
AT THE VERY LEAST, WE'LL DEFINITELY BE OVERCAST TODAY. WINDS
ARE ALSO NOT A CONCERN TODAY AS THERE IS A LESS THAN 5% CHANCE
FOR WIND GUSTS GREATER THAN 35 MPH ACROSS THE AREA.
TONIGHT, THE AFOREMENTIONED LOW PRESSURE SYSTEM WILL STRENGTHEN
AND SWING A COLD FRONT THROUGH THE REGION, RETURNING WIDESPREAD
RAIN. THE MAJORITY OF ENSEMBLE MEMBERS FROM THE
GFS/EURO/CANADIAN ARE IN AGREEMENT THAT THE CENTER OF THE LOW
WILL BE STRONGEST JUST OFFSHORE OF SOUTHERN OREGON AND NORTHERN
CALIFORNIA, SO THOSE AREAS ARE FAVORED TO RECEIVE THE HEAVIEST
PRECIPITATION. FOR OUR AREA BETWEEN 10 PM WEDNESDAY AND 10 PM
THURSDAY, CHANCES FOR 24-HOUR RAINFALL EXCEEDING 0.50 INCH ARE
AROUND 30-50% FOR INTERIOR VALLEYS (HIGHEST CHANCES ACROSS THE
SOUTHWEST WASHINGTON LOWLANDS), AND 60-80% ALONG THE COAST,
COAST RANGE, WILLAPA HILLS, AND NORTH OREGON/SOUTH WASHINGTON
CASCADES. WINDS WILL ALSO INCREASE AND TURN MORE SOUTHWESTERLY
ON THURSDAY, BUT LIKELY (80% CHANCE) REMAIN NON-IMPACTFUL. THERE
IS ONLY A 10-20% CHANCE FOR IMPACTFUL WIND GUSTS EXCEEDING 45
MPH ALONG THE COAST, AND A 5-10% CHANCE FOR INLAND LOCATIONS.
THIS SCENARIO WOULD ONLY OCCUR IF THE LOW ENDS UP STRENGTHENING
AND TRACKING FURTHER NORTH (OFFSHORE OF CENTRAL/NORTHERN
OREGON).
SINCE THE LOW IS EXPECTED TO TRACK FURTHER SOUTH, TEMPERATURES
HAVE TRENDED WARMER ACROSS THE REGION BEHIND THE COLD FRONT,
INCLUDING THE CASCADES. CHANCES FOR SNOW LEVELS DROPPING BELOW
5000 FT (PASS-LEVEL) THURSDAY-FRIDAY ARE NOW 25-45% ACROSS THE
OREGON CASCADES, WITH THE HIGHEST CHANCES (45%) AT HIGHWAY 26
NEAR GOVERNMENT CAMP, AND LOWEST CHANCES (25-35%) AT SANTIAM AND
WILLAMETTE PASSES. CHANCES FOR 48-HOUR SNOWFALL OF 6 INCHES OR
GREATER (ADVISORY LEVEL) BETWEEN 4 AM THURSDAY AND 4 AM
SATURDAY HAVE NOW FALLEN TO 5-10% ACROSS THESE PASSES. FOR ONE
INCH OF SNOW IN THE PASSES, THE CHANCES ARE 30-40%. ANOTHER
CHANGE THESE RELATIVELY WARMER TEMPERATURES HAVE ARE ON
THUNDERSTORM POTENTIAL. SINCE WE WON'T BE AS COOL ALOFT,
INSTABILITY IS MORE LIMITED AND THUS CHANCES FOR THUNDERSTORMS
THURSDAY HAVE FALLEN TO 10% OR LESS ACROSS NORTHWEST OREGON AND
SOUTHWEST WASHINGTON.
THE BROADER WEATHER PATTERN STAYS ACTIVE THROUGH THE END OF THE
WEEKEND AND INTO THE WEEKEND. A WARM FRONT LIFTING NORTH ON
SATURDAY WILL RAISE SNOW LEVELS AND TRANSITION PRECIPITATION
BACK TO RAIN IN THE CASCADES, FOLLOWED BY ANOTHER COLD FRONT ON
SUNDAY THAT WILL LOWER SNOW LEVELS ONCE AGAIN, RETURNING SNOW
CHANCES TO THE PASSES BY SUNDAY NIGHT. ELSEWHERE, PERIODIC RAIN
IS EXPECTED TO PERSIST THROUGH TUESDAY UNDER CONTINUED SOUTHWEST
FLOW ALOFT. -10
AVIATION
SATELLITE IMAGERY AND TERMINAL OBSERVATIONS AS OF
EARLY WEDNESDAY MORNING DEPICTS LIFR CIGS ACROSS THE CENTRAL
AND SOUTHERN WILLAMETTE VALLEY WITH LIFR VIS AT KEUG DUE TO FOG
AND IFR VIS AT KUAO/KSLE DUE TO MIST. HIGH PRESSURE ALOFT WILL
MAINTAIN THESE LIFR CIGS IN THE CENTRAL/SOUTHERN VALLEY THROUGH
18-19Z WED. MEANWHILE THERE IS A 20-30% CHANCE THAT LOW STRATUS
WILL REACH THE PORTLAND METRO TERMINALS BETWEEN 12-18Z WED.
THESE LOW CIGS/VIS SHOULD CLEAR OUT AFTER 18-19Z WED AS MIXING
INCREASES DUE TO DAYTIME HEATING AND THE INCOMING SYSTEM.
A WARM FRONT LIFTING NORTHWARD TODAY WILL BRING RAIN SHOWERS TO
THE REGION BY WEDNESDAY AFTERNOON. AHEAD OF THE BOUNDARY,
LARGELY VFR CONDITIONS REMAIN IN PLACE ACROSS THE WILLAMETTE
VALLEY WITH BKN/OVC MID TO HIGH LEVEL CLOUDS. ALONG THE COAST,
THERE IS A 50-70% CHANCE FOR MVFR/LOW-END VFR CIGS AFTER 15-18Z
WED AS THE FRONT ARRIVES. CONDITIONS AT THE COAST SHOULD IMPROVE
BEHIND THE WARM FRONT BACK TO VFR AFTER 22Z WED-00Z THU. WINDS
GENERALLY LIGHT AND VARIABLE ACROSS THE REGION FOR MOST OF THE
TAF PERIOD, EXCEPT FOR BRIEF SOUTHERLY WINDS ALONG THE COAST
FROM 18Z WED-00Z THU WITH GUSTS UP TO 20 KT AT KONP AS THE FRONT
PASSES THROUGH.
KPDX AND APPROACHES...VFR WITH LIGHT AND VARIABLE WINDS UNDER 5
KT EXPECTED THROUGH EARLY THIS MORNING. ONLY A 10-15% CHANCE
THAT MVFR CIGS EXTEND INTO THE PORTLAND AREA BY 15Z WED.
OTHERWISE, CIGS REMAIN AROUND 10 KFT OR HIGHER WITH EAST WINDS
AROUND 5 KT. RAIN SHOWERS BEGIN AFTER 21Z WED-00Z THU. -10/36
MARINE
HIGH PRESSURE OVER THE WATERS WILL MAINTAIN CALM
MARINE CONDITIONS THROUGH EARLY THIS MORNING. WINDS WILL
GENERALLY REMAIN EAST SOUTHEASTERLY WITH GUSTS LESS THAN 15 KT
AND SEAS OF 7-8 FT AT 13-14 SEC. THE NEXT LOW PRESSURE SYSTEM IN
THE NE PACIFIC WILL RETURN BREEZY SOUTHERLY WINDS AND BUILDING
SEAS TODAY, WITH HIGH CONFIDENCE FOR ANOTHER PERIOD OF
CONDITIONS HAZARDOUS TO SMALL CRAFT. AS THIS SYSTEM SWINGS A
FRONT THROUGH THE WATERS, THERE'S A 60-80% CHANCE OF FREQUENT
SOUTHERLY WIND GUSTS EXCEEDING 21 KT THIS AFTERNOON AND A
GREATER THAN 90% CHANCE THAT SEAS BUILD ABOVE 10 FT BY LATE
WEDNESDAY NIGHT/EARLY THURSDAY MORNING.
WINDS BRIEFLY TURN EASTERLY AND EASE TO AROUND 20 KT OR LESS
WEDNESDAY NIGHT, HOWEVER, WINDS QUICKLY INCREASE AND TURN
SOUTHERLY AGAIN ON THURSDAY AS THE LOW DEEPENS AND SWINGS
ANOTHER FRONT THROUGH THE WATERS. WILL NOTE THAT OCCASIONAL
GALE-FORCE WIND GUSTS OF 34 KT OR GREATER ARE POSSIBLE BETWEEN
10 AM AND 4 PM THURSDAY, MAINLY SOUTH OF CAPE FALCON AND BEYOND
20-30 NM. THIS AREA WILL ALSO HAVE A 40-50% CHANCE FOR SEAS
BUILDING ABOVE 15 FT. THE SMALL CRAFT ADVISORY FOR ALL MARINE
ZONES GOES INTO EFFECT 10 AM WEDNESDAY AND HAS BEEN EXTENDED
THROUGH 4 AM FRIDAY.
ANOTHER FRONTAL SYSTEM WILL SWING THROUGH BRITISH COLUMBIA AND
FAR NORTHWEST WASHINGTON ON FRIDAY, MAINTAINING RELATIVE
BREEZY SOUTHWESTERLY WINDS OVER OUR COASTAL WATERS. HOWEVER,
CHANCES FOR FREQUENT WIND GUSTS STRONGER THAN 21 KT ARE ONLY
AROUND 30-40% ON FRIDAY. -10
PQR WATCHES/WARNINGS/ADVISORIES
OR...NONE.
WA...NONE.
PZ...SMALL CRAFT ADVISORY FROM 10 AM THIS MORNING TO 4 AM PST FRIDAY
FOR PZZ210-251>253-271>273.
WWW.WEATHER.GOV/PORTLAND
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