436
FXUS66 KPQR 151247
AFDPQR
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE PORTLAND OR
447 AM PST MON DEC 15 2025
SYNOPSIS
A SERIES OF COMPLEX FRONTAL SYSTEMS WILL MOVE
THROUGH THE AREA THIS WEEK EACH BRINGING CHANCES FOR STRONG
WINDS, HEAVY RAIN, AND RIVER FLOODING LATER IN THE WEEK. EACH
SYSTEM HAS THE POTENTIAL TO BE IMPACTFUL IN IT'S OWN WAY. IN THE
SHORT TERM, THE MAIN CONCERNS LIE WITH RAIN ON MONDAY, AND WIND
ON TUESDAY. THERE ARE INCREASING PROBABILITIES OF SOME INTERIOR
AREAS MEETING WIND ADVISORY CRITERIA ON TUESDAY. HEAVY RAIN
RETURNS ON THURSDAY BUT IS SHIFTING FURTHER SOUTH TO AREAS THAT
DID NOT RECEIVE AS MUCH RAIN THE LAST TIME AROUND.
SHORT TERM...NOW THROUGH WEDNESDAY
THE NEXT 48 HOURS WILL BE
QUITE DYNAMIC WITH WIDESPREAD RAIN AND GUSTY CONDITIONS.
CURRENT RADAR AND SATELLITE SHOWS WIDESPREAD RAIN OVER THE
REGION WITH TOTALS RANGING FROM 0.1-0.4 INCH OF RAIN SINCE
MIDNIGHT WITH THE NORTHERN PORTIONS OF THE FORECAST AREA SEEING
MORE RAIN THAN SOUTH OF NEWBERG. RAIN WILL CONTINUE TODAY WITH
HEAVIER ACCUMULATIONS ALONG THE COAST THIS MORNING AND SHIFTING
EASTWARD THROUGH THE DAY. THE BULK OF THE FRONT WILL HAVE PASSED
BY SUNSET. THE THREAT TODAY CONTINUES TO BE WIND AS STRONG
SOUTHWESTERLY FLOW TAKES OVER. ALOFT A VERY STRONG JET STREAM AT
35,000 FT IS PASSING OVER. THIS JET IS COUPLED WITH A LOW LEVEL
JET AT RIGHT AROUND 5000 FT. THIS JET HAS THE POTENTIAL TO MIX
STRONG WINDS DOWN TO THE SURFACE. AT 3500 FT AND ABOVE WINDS ARE
CURRENTLY AROUND 40-50 MPH BUT THAT WILL AMPLIFY THROUGH THE
MORNING AND EARLY AFTERNOON. THERE IS ONE FACTOR ABOUT THIS
FRONT THAT MAY ASSIST IN KEEPING THE INTERIOR VALLEYS LESS
WINDY. THIS IS A WARM FRONTAL PASSAGE AND THEREFORE AN INVERSION
IS IN PLACE AS IT MOVES OVER. THIS INVERSION CAN ACT LIKE A
BARRIER KEEPING THE WIND FROM MIXING DOWN. HOWEVER, AS IT
BREAKS DOWN IN THE AFTERNOON THERE IS THE POTENTIAL FOR GUSTS UP
TO 40 MPH INLAND. THERE IS AROUND A 10-15% CHANCE FOR GUSTS UP
TO 40 MPH WITHIN THE WILLAMETTE VALLEY AND AROUND A 50-60%
CHANCE OF GUSTS UP TO 40 MPH ALONG THE CASCADE FOOTHILLS. THE
NBM 24-HR MAXIMUM GUSTS IS SHOWING AROUND A 60-70% CHANCE OF
GUSTS GREATER THAN 45 MPH THIS AFTERNOON, HOWEVER THAT IS LIKELY
AN INSTANTANEOUS GUST. EVEN WITH THOSE PROBABILITIES HAVE
DECIDED AGAINST ISSUING A WIND ADVISORY FOR THE NORTHERN OREGON
CASCADE FOOTHILLS GIVEN THE LACK OF CONFIDENCE IN THE PROLONGED
PERIOD OF TIME. WITH ALL THAT BEING SAID THOUGH, THE RAIN FROM
THE PAST SEVERAL DAYS HAVE MADE SOILS INCREDIBLY SATURATED AND
THEREFORE CANNOT RULE OUT TREE DAMAGE FROM EVEN INSTANTANEOUS
GUSTS. AS HIGHER RESOLUTION MODELS ARRIVE WE WILL CONTINUE TO
MONITOR.
OVERNIGHT CONDITIONS WILL EASE SLIGHTLY ALLOWING FOR A BRIEF
PERIOD OF RECOVERY. IT WILL BE SHORT-LIVED THOUGH AS YET ANOTHER
FRONTAL SYSTEM APPROACHES. LOOKING AT THE ENSEMBLE LOW
LOCATIONS, THERE IS HIGH CONFIDENCE IN A CONCENTRATED LOW CENTER
MOVING UP AND OVER VANCOUVER ISLAND. THIS LOW WILL DRIVE THE
WEATHER ON TUESDAY WHICH HAS SHIFTED A BIT SINCE PREVIOUS
FORECASTS. AGAIN, THIS FRONTAL SYSTEM APPEARS TO MOVE FAIRLY
QUICKLY ACROSS THE AREA TUESDAY NIGHT, WITH THE HEAVIEST
PRECIPITATION EXPECTED BETWEEN 4 PM TUE - 10 AM WED. TOTAL
RAINFALL AMOUNTS ARE LIKELY TO BE SIMILAR TO OR SLIGHTLY HIGHER
THAN TODAY'S SYSTEM. THE CHANGE COMES IN REGARDS TO WIND.
CONCERN CONTINUES TO RISE REGARDING THE POTENTIAL FOR ANOTHER
ROUND OF STRONG WIND ON TUESDAY. A COMPONENT TO WATCH FOR IN
THESE SCENARIOS IS THE LOW LEVEL JET. TYPICALLY AT AROUND
975-850 MB, THE STRONGER THESE WINDS THE HIGHER PROBABILITY OF
MIXING DOWN TO THE SURFACE. THE FLOW ALOFT IS WESTERLY WHILE
SURFACE FLOW IS SOUTHWESTERLY. AT 850 MB (AROUND 5,000-7,000 FT)
WIND SPEEDS BETWEEN 7PM TUESDAY AND 4 AM WEDNESDAY RANGE FROM
55-70 MPH. AGAIN, THERE IS AN INVERSION IN PLACE THAT COULD
INHIBIT THEIR ABILITY TO REACH THE SURFACE. INCREASING
CONFIDENCE IN GUSTS GREATER THAN 45 MPH ALONG THE COAST RANGE
AND EVEN INLAND. THERE PEAK WIND GUSTS SHOWS UP TO A 20-30%
CHANCE OF WIND GUSTS UP TO 58 MPH AROUND THE HIGHEST POINTS OF
THE COAST RANGE AND ALONG THE COAST ON TUESDAY. EASILY WILL SEE
GUSTS EXCEEDING 60 MPH ALONG THE CASCADES AND ABOVE 3000 FT. GIVEN
THE VARIABLE NATURE IN THIS SYSTEM AND THE PACE/STRENGTH OF THE
LOW, WILL WAIT FOR THE NEXT ROUND OF HIGHER RESOLUTION MODELS
TO GIVE A BIT MORE DETAILS TO DETERMINE IF ANY HAZARDS ARE
NEEDED.
WEDNESDAY IS ALMOST A RECOVERY DAY FROM THE TWO BOUTS OF RAIN
AND WIND. NOW THAT'S NOT TO SAY THAT WE WON'T SEE ACTIVE
WEATHER, BUT THE OVERALL IMPACT APPEARS TO BE LOWER. SNOW LEVELS ARE EXPECTED
TO DROP SIGNIFICANTLY BY WEDNESDAY MORNING WITH THE PASSAGE OF THE
UPPER TROUGH. THIS WILL ALLOW FOR SNOW TO BEGIN ACCUMULATING AT PASS
LEVEL ON WEDNESDAY. THE WEATHER SETUP ON WEDNESDAY WILL FEATURE
ONSHORE FLOW WITH ZONAL FLOW ALOFT, LIKELY MAINTAINING SHOWERS
ENHANCED BY OROGRAPHIC EFFECTS. THERE STILL REMAINS SOME UNCERTAINTY
REGARDING SNOWFALL AMOUNTS THROUGH WEDNESDAY NIGHT, AS
PROBABILITY FOR MORE WIDESPREAD MOUNTAIN SNOW OF 12 INCHES OR
MORE HAVE COME DOWN EXCEPT ON THE VOLCANOS. THERE IS STILL A
PERIOD OF TIME ON WEDNESDAY INTO THURSDAY WHERE 6+ INCHES OF
SNOW MAY FALL AROUND THE PASSES. ULTIMATELY IT WILL COME DOWN TO
WHEN THE COLD AIR AND PRECIPITATION MESH. -27
AS THE SYNOPTIC PATTERN PROGRESSES INTO LATE NEXT WEEK THERE IS
A TREND FOR YET ANOTHER ATMOSPHERIC RIVER ON THURSDAY INTO FRIDAY.
AT THIS POINT, CONFIDENCE REMAINS LOW AS THERE REMAINS SIGNIFICANT
DIFFERENCES BETWEEN ENSEMBLES, BUT THESE HAVE GRADUALLY BEEN COMING
INTO BETTER AGREEMENT OVER THE PAST 48-HOURS. THE WPC (WEATHER
PREDICTION CENTER) HAS MAINTAINED A SLIGHT RISK OF EXCESSIVE
RAINFALL ACROSS MOST OF WESTERN OREGON, WHICH MEANS THERE IS
INCREASING PROBABILITY OF EXCEEDING FLASH FLOODING GUIDANCE. WITH
OUR SOILS VERY SATURATED AND RIVERS FULL, ADDING THE THURSDAY-
FRIDAY SYSTEM, LOCAL AREA RIVERS COULD SEE POTENTIAL FLOODING. THERE
REMAINS QUITE A BIT OF VARIABILITY AS TO WHERE THE PLUME OF MOISTURE
AND HIGHEST IVT VALUES SET UP, BUT INDICATIONS ARE THAT THESE 24 TO
48-HR RAINFALL AMOUNTS THURSDAY INTO EARLY FRIDAY ARE LIKELY TO BE
THE HIGHEST OF THE WEEK. LATEST MODEL RUNS HAVE SHIFTED THE SYSTEM
FARTHER NORTH WITH MORE WEST-SOUTHWEST FLOW. THIS WOULD ALSO PUSH
SNOW LEVELS HIGHER IN THE CASCADES THROUGH THURSDAY NIGHT.
WITH THE POTENTIAL FOR HEAVIER RAINFALL LATE IN THE WEEK,
PROBABILITIES FOR LOCAL TRIBUTARY RIVERS REACHING AT LEAST MINOR
FLOOD STAGE HAVE INCREASED TO AROUND 30-50%. MODERATE FLOOD STAGE
REMAINS LOW AROUND 10-20%. AGAIN, STILL QUITE A BIT OF UNCERTAINTY.
BUT MOVING INTO THE WEEKEND, CONDITIONS LIKELY EASE WITH CLUSTERS
SHOWING LOW AMPLITUDE TROUGHING LIKELY OVER THE PACIFIC NW. SHOWERS
WILL LIKELY CONTINUE WITH LOWER SNOW LEVELS. THERE IS AROUND A 10%
CHANCE THAT SNOW FLAKES OR A SNOW/RAIN MIX FALLS TO AROUND 1500 FT
IN THE FOOTHILLS. /DH
LONG TERM...THURSDAY THROUGH SUNDAY
NOW AS WE TRANSITION INTO
THE LATER HALF OF THE WEEK THE WEATHER APPEARS TO RAMP BACK UP
WITH A TREND TOWARDS ANOTHER ATMOSPHERIC RIVER. ON THURSDAY WE
WILL EXPERIENCE THE HIGHEST PRECIPITATION OF THE LONG TERM
FORECAST AS IT BLEEDS INTO FRIDAY. THE CHALLENGE WITH THIS
SPECIFIC SYSTEM IS THAT THERE IS A LACK OF CONSISTENCY WITH THE
SYNOPTIC FLOW. THE ATMOSPHERIC RIVER HAS A HIGH PROBABILITY OF
OCCURRING, BUT MODELS ARE SHOWING SEVERAL SHORTWAVES AND LOWS
TRAILING BEHIND IT IN THE FLOW. THIS WOULD LEAD TOWARDS A MORE
PROLONGED SYSTEM VS A SHORT BURST OF RAIN LIKE THE
MONDAY/TUESDAY SYSTEMS. HOWEVER, IF YOU LOOK AT THE GUIDANCE WE
TYPICALLY USE FOR ATMOSPHERIC RIVERS, THEY SHOW SIMILAR
FEATURES TO THAT OF THE EARLIER EVENTS. AT THIS POINT,
CONFIDENCE IS INCREDIBLY LOW BUT IF WE MAINTAIN THE COLD AIR
WITH LOWERED SNOW LEVELS, WE COULD BE LOOKING AT OUR FIRST HEAVY
SNOWFALL OF THE SEASON. IN FACT, THE MEAN OF THE NBM 48-HR
SNOWFALL AMOUNTS SHOWS AS MUCH AS 35 INCHES OF SNOW FOR THURSDAY
& FRIDAY COMBINED AT MT HOOD. THERE IS A 10% CHANCE OF NEARLY 4
FEET IN THOSE 48 HOURS. HOWEVER, IF THE SNOW LEVELS RISE LIKE
THEY MAY DO IF THE ATMOSPHERIC RIVER SHIFTS FURTHER NORTH, THEN
WE WOULD SEE SIGNIFICANTLY LESS SNOW WITH A 10% CHANCE OF ONLY
15 INCHES OF SNOW. IF YOU'RE PLANNING ON TRAVELING OVER THE
PASSES THIS WEEKEND, PLEASE CONTINUE TO TRACK THE FORECAST
SHIFTS AS THIS SYSTEM DEVELOPS FURTHER.
WITH THE INFLUX OF ADDITIONAL HEAVY PRECIPITATION FLOODING AGAIN
RISES AS A CONCERN. WHILE THE EXTENT OF THE FLOODING IS NOT
FORECAST TO BE AS WIDESPREAD AT THIS POINT, WE MUST STILL BE
DILIGENT AS THERE ARE STILL A NUMBER OF RIVERS THAT ARE
FORECAST TO REACH FLOOD STAGE. THEREFORE, IF YOU LIVE NEAR ANY
RIVERS, PLEASE VISIT WWW.WATER.NOAA.GOV/WFO/PQR FOR LOCALIZED
FORECASTS.
PRECIPITATION REMAINS THROUGH THE WEEKEND. -27
AVIATION
HEAVY RAIN EXPECTED OVER THE NEXT 12 HOURS AS AN
ATMOSPHERIC RIVER MOVES OVER THE REGION. GUSTY WINDS WILL BE
ASSOCIATED WITH THE PASSING FRONT AND THEREFORE MAY SEE REDUCED
VIS WITH FALLING CIGS AND RAIN. THE PIECE OF THE FORECAST THAT
IS A BIT MORE UNIQUE IS THE WIDESPREAD POTENTIAL FOR LLWS.
BETWEEN 2000-5000 FT AGL WINDS WILL BE IN EXCESS OF 40 KT WITH
SOME AREAS REACHING AS HIGH AS 65 KT AT 5000 FT. THE SURFACE
FLOW WILL BE MORE SOUTHERLY WHILE FLOW ALOFT SOUTHWESTERLY.
THEREFORE, PREPARE FOR LLWS FOR THE NEXT SEVERAL HOURS. AS THE
FRONT EXITS, POST FRONTAL SHOWERS WILL FORM. AS THE FRONT
PASSES, CONDITIONS WILL IMPROVE WITH LOW-END VFR CIGS AFTER 00Z
TUE. THE WIND THREAT REMAINS THROUGH 06Z TUE FOR HIGHER
ELEVATIONS AND APPROACHES.
KPDX AND APPROACHES...CONDITIONS HAVE REMAINED VFR THIS MORNING,
LIKELY DUE TO THE LIFTING ASSOCIATED WITH THE FRONT. THE LOWER
ATMOSPHERE IS WELL MIXED WHICH COULD COMBAT THE CIGS DROPPING
SIGNIFICANTLY. THERE REMAINS A TREND TOWARDS MVFR THOUGH AS THE
BULK OF THE FRONT SHIFTS OVER THE TERMINAL. SOME HI-RESOLUTION
GUIDANCE SUPPORTS EVEN STRONGER GUSTS EXCEEDING 30 KT, MOST
LIKELY BETWEEN UNTIL 20Z MON. A STRONG LOW-LEVEL JET OUT OF THE
SOUTH-SOUTHWEST WILL ALSO SUPPORT LOW-LEVEL WIND SHEAR OF 30-45
KT. THIS CONCERN RAPIDLY DISSIPATES ~19-20Z BEHIND THE FRONTAL
PASSAGE. -27/99
MARINE
A STRONG COLD-FRONTAL SYSTEM IS SLATED TO PASS
THROUGH THE WATERS TODAY (MONDAY) LEADING TO FAIRLY IMPACTFUL
CONDITIONS ACROSS THE WATERS. GALE WARNINGS ARE IN EFFECT FOR
THE INNER AND OUTER WATERS, INCLUDING THE COLUMBIA RIVER BAR,
THROUGH THE DAYTIME HOURS WITH HIGH CONFIDENCE IN SUSTAINED
WINDS OF 25-35 KT WITH GUSTS OF 40-50 KT. AT THIS POINT ISOLATED
STORM-FORCE GUSTS ASSOCIATED WITH A COASTAL JET ACCOMPANYING
THE FRONTAL BOUNDARY CAN'T BE RULED OUT MONDAY MORNING WITH A
35-45% CHANCE OF OCCURRING SOMEWHERE ALONG THE SOUTHWEST
WASHINGTON OR NORTHWEST OREGON COASTS, AND ONLY 10-20% CHANCES
ACROSS THE OUTER WATERS. WHILE WINDS PEAK MONDAY MORNING, SEAS
CONTINUE TO BUILD INTO MONDAY AFTERNOON BEFORE SLOWLY EASING ON
TUESDAY. SEAS WILL MOST LIKELY REACH INTO THE 15-18 FT RANGE
MONDAY AFTERNOON, WITH A 10-35% CHANCE OF SURPASSING 18 FT
BEYOND 30 NM NORTH OF CAPE FALCON - 10% OR LESS ELSEWHERE. BY
TUESDAY AFTERNOON, SIGNIFICANT WAVE HEIGHTS ARE LIKELY CLOSER TO
11-14 FT WITH A DOMINATE PERIOD OF 11-12 SECONDS.
GOING FORWARD A RATHER ACTIVE WEATHER PATTERN, EVEN BY DECEMBER
STANDARDS, CONTINUES THROUGH THE WORK WEEK BRINGING ADDITIONAL
WINDS AND WAVE HAZARDS TO THE COASTAL WATERS. SEAS ARE VERY
LIKELY TO REMAIN ELEVATED ABOVE 10 FT (GREATER THAN 90%
CONFIDENCE) FROM WEDNESDAY THROUGH FRIDAY AS ADDITIONAL WEATHER
SYSTEMS MOVE ONSHORE. AT LEAST MODELS ARE BEGINNING TO HINT AS
SOME LARGER BREAKS BETWEEN WEATHER DISTURBANCES NEXT WEEKEND INTO
THE FOLLOWING WEEK, BUT AT THIS 7-8 DAY TIME-SCALE, THE
CONFIDENCE IN THIS SLOWDOWN MATERIALIZING IS ONLY LOW TO MODERATE
AT THIS TIME. -99/36
PQR WATCHES/WARNINGS/ADVISORIES
OR...WIND ADVISORY UNTIL 4 PM PST THIS AFTERNOON FOR ORZ106-107.
WA...WIND ADVISORY UNTIL 4 PM PST THIS AFTERNOON FOR WAZ203.
PZ...GALE WARNING UNTIL 4 PM PST THIS AFTERNOON FOR PZZ210-251>253-
271>273.
HAZARDOUS SEAS WARNING FROM 4 PM THIS AFTERNOON TO 4 AM PST
TUESDAY FOR PZZ210-251>253-271>273.
SMALL CRAFT ADVISORY FROM 4 AM TO 4 PM PST TUESDAY 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