906
FXUS66 KPQR 151808 AAB
AFDPQR
AREA FORECAST DISCUSSION...UPDATED
NATIONAL WEATHER SERVICE PORTLAND OR
1006 AM PST MON DEC 15 2025
..UPDATED AVIATION DISCUSSION
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
RADAR IMAGERY AS OF LATE MONDAY MORNING DEPICTS
WIDESPREAD SHOWERS AS A FRONTAL SYSTEM MOVES THROUGH THE AREA.
THIS IS ALSO BRINGING A MIX OF MVFR AND LOW-END VFR CIGS ACROSS ALL
TERMINALS, WITH SOME IFR CIGS ALONG THE COAST. EXPECT THIS TREND TO
CONTINUE THROUGH 00Z TUE, WITH CIGS BRIEFLY IMPROVING TO
PREDOMINATELY VFR THIS EVENING. HIGH CONFIDENCE (80% CHANCE OR
GREATER) CIGS DROP BACK DOWN TO IFR OR LOWER ALONG THE COAST AFTER
12-15Z TUE AS THE NEXT SYSTEM MOVES IN. DURING THIS SAME TIME FRAME,
INLAND TERMINALS ALSO HAVE A 20-40% CHANCE OF DROPPING BACK DOWN TO
MVFR.
SOUTH-SOUTHWESTERLY WINDS ARE GUSTING TO 40-45 KT ALONG THE COAST
AND 20-25 KT ACROSS THE WILLAMETTE VALLEY AS OF LATE MONDAY MORNING.
WINDS AROUND 2000 FT ARE AROUND 50-60 KT, WHICH WILL CREATE A STRONG
CROSSWIND ESPECIALLY FOR E-W ALIGNED RUNWAYS. LOW LEVEL SPEED SHEAR
IS POSSIBLE WITH THESE STRONG WINDS. THIS WIND SHEAR WILL BE
UNIDIRECTIONAL FOR MOST TERMINALS, EXCEPT FOR THE FAR EASTERN
PORTLAND METRO TERMINALS WHERE EASTERLY WINDS STILL PERSIST THIS
MORNING. WINDS ACROSS THE AREA WEAKEN OVERNIGHT, AND BECOME BREEZY
AGAIN AFTER 12-15Z TUE WITH THE NEXT SYSTEM.
KPDX AND APPROACHES...MIX OF HIGH-END MVFR AND LOW-END VFR CIGS,
WITH CIGS TRENDING MORE VFR THIS AFTERNOON. SOUTH-SOUTHWESTERLY
WINDS GUSTING UP TO 25 KT TODAY. WINDS REMAIN EASTERLY AT KTTD
THROUGH 21Z TUE WHILE STRONG SOUTHWESTERLY WINDS REMAIN AT 2000 FT,
SO DIRECTIONAL WIND SHEAR IS POSSIBLE IN THE FAR EAST PORTLAND METRO
UNTIL THEN. WINDS SHOULD SHIFT SOUTHERLY AFTER 21Z TUE AT KTTD.
WINDS WEAKEN BELOW 10 KT AFTER 00Z TUE, WITH BREEZY SOUTHERLY WINDS
RETURNING AFTER 12-15Z TUE. -10
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...HIGH WIND WARNING UNTIL 1 PM PST THIS AFTERNOON FOR ORZ101-102.
WIND ADVISORY UNTIL 4 PM PST THIS AFTERNOON FOR ORZ106-107.
WA...HIGH WIND WARNING UNTIL 1 PM PST THIS AFTERNOON FOR WAZ201.
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
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