391
FXUS66 KPQR 121833
AFDPQR
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE PORTLAND OR
1133 AM PDT THU MAR 12 2026
UPDATE
IT'S WET OUT THERE TODAY AS AN ATMOSPHERIC RIVER
CONTINUES TO INUNDATE THE REGION. CURRENT RADAR OBSERVATIONS
SHOW THE PRIMARY BAND OF RAINFALL CENTERED ROUGHLY BETWEEN
SALEM, OR AND CLARK COUNTY, WA NOW STARTING TO SLOWLY LIFT
NORTHWARD IN RESPONSE TO A WEAK DISTURBANCE APPROACHING THE
COAST. BASED ON THE LATEST 12Z HREF/REFS AND OTHER ENSEMBLE
SYSTEMS, CONFIDENCE IS HIGH THE QUASI-STATIONARY COLD FRONTAL
BOUNDARY HELPING TO DIRECT THE AXIS OF HEAVIEST PRECIPITATION
WILL CONTINUE TO TREND INTO NORTHERN OREGON AND SOUTHWEST
WASHINGTON THROUGH THE EVENING HELPING TO LOWER RAINFALL RATES
IN THE CENTRAL/SOUTHERN WILLAMETTE VALLEY BEFORE FINALLY KICKING
BACK SOUTHWARD FOR THE FINAL TIME FRIDAY THROUGH FRIDAY NIGHT.
THIS LATTER MOVEMENT WILL BE A SLUGGISH AND GRADUAL PROGRESSION
AND THE LATEST GUIDANCE SEEMS TO BE AROUND 3-6HRS SLOWER
COMPARED TO YESTERDAY. THUS, FLOODING CONCERNS CONTINUE THROUGH
FRIDAY NIGHT, PARTICULARLY FIR FLASHIER RIVER/STREAMS WITH
LOCALIZED AREAL FLOODING POSSIBLE AS WELL. FOR THE LATEST RIVER
FORECASTS, VISIT HTTP://WWW.WATER.NOAA.GOV . AT LEAST ONCE WE
GET PAST THIS EVENT WE'LL BE GIFTED WITH SOME WARMER
TEMPERATURES EARLY NEXT WEEK. THE PREVIOUS DISCUSSION REMAINS
BELOW. -99
SYNOPSIS
AN ATMOSPHERIC RIVER (AR) WILL CONTINUE TO IMPACT
THE PACIFIC NORTHWEST THROUGH FRIDAY. EXPECT PERIODS OF MODERATE
TO HEAVY RAIN, AND MOUNTAIN SNOW (MAINLY WA CASCADES). WHILE
THE PROBABILITY FOR MAINSTEM RIVER FLOODING IS LOW, SOME OF THE
MORE FLOOD PRONE COASTAL AND COAST RANGE RIVERS HAVE RISEN TO
MINOR OR MAJOR FLOOD STAGE. WITH HEAVY RAIN RATES, AN AREAL
FLOOD WATCH REMAINS IN EFFECT THROUGH FRIDAY EVENING. FROM
THERE, ANOTHER WEATHER SYSTEM CLIPPING THE AREA TO THE NORTH
LATE IN THE WEEKEND MAY BRING ADDITIONAL PRECIPITATION IN
ADDITION TO USHERING IN MUCH WARMER TEMPERATURES FOR EARLY NEXT
WEEK.
SHORT TERM...NOW THROUGH FRIDAY NIGHT
RADAR IMAGERY THIS
MORNING SHOWS THE ATMOSPHERIC RIVER DRAPED OVER THE PACIFIC
NORTHWEST WITH THE HEAVIEST RAINFALL NEARLY DIRECTLY OVER
NORTHWEST OREGON AND SOUTHWEST WASHINGTON. THIS SHOWS THAT THE
PROJECTED ATMOSPHERIC RIVER (AR) SHIFTED SLIGHTLY SOUTHWARD FROM
WHAT MODELS WERE PROJECTING. BECAUSE OF THIS, WE HAVE
EXPERIENCED HEAVY RAIN WITH HIGH RAIN RATES. IN THE LAST 6 HOURS
(AS OF 2 AM), RAINFALL TOTALS HAVE RANGED FROM 1.50" IN THE
NORTH OREGON COAST RANGE, 0.60" IN THE WILLAPA HILLS, INLAND
NORTH OF AURORA, AND LESS THAN 0.5" SOUTH OF SALEM. THESE
RAINFALL TOTALS HAVE EQUATED TO RISING RIVER LEVELS ALONG THE
COASTAL AND COAST RANGE RIVERS/TRIBUTARIES. SEE THE "HYDROLOGY"
DISCUSSION BELOW FOR HYDROLOGICAL PROBABILITIES AND IMPACTS.
WINDS REMAIN GUSTY ABOVE 1000 FT WITH SOME OBSERVATIONS
REPORTING 50 MPH GUSTS ALONG THE COAST RANGE, WITHIN THE AREA
SURROUNDING THE COLUMBIA RIVER GORGE, AND THE CASCADES. WINDS
WILL CONTINUE TO EASE AS THE LOW-LEVEL JET SHIFTS EASTWARD. BY
THIS AFTERNOON THE WINDS ALOFT WILL REACH TYPICAL SPEEDS FOR
THIS TIME OF YEAR. HOWEVER, UNTIL THEN, THEY WILL BE
CLIMATOLOGICALLY ABNORMAL WITH A RESURGENCE ON FRIDAY MORNING.
NOW, BACK TO PRECIPITATION...THE BIG PAGE TURNER FOR THE NEXT 2
DAYS. TODAY CONTINUES TO SEE AN ELEVATED THREAT FOR HEAVY RAIN
AND SNOW IN THE SOUTH WASHINGTON CASCADES. HIGH RESOLUTION
MODELS SHOW HIGH CONFIDENCE IN THE AR CONTINUING TO IMPACT THE
REGION WITH NORTHWEST OREGON SITTING IN THE SOUTHERN HALF OF THE
SYSTEM. THIS MEANS WE WILL CONTINUE TO SEE A STEADY STREAM OF
PRECIPITATION THROUGH AT LEAST FRIDAY. LET'S DIVE INTO THOSE
NUMBERS. 48 HOUR RAINFALL TOTALS ENDING SATURDAY MORNING
CONTINUE TO SHOW SOMEWHAT OF A RANGE IN REGARDS TO
ACCUMULATION, BUT DEFINITELY A MUCH MORE NARROW RANGE THAN
PREVIOUSLY OBSERVED. IN TILLAMOOK THERE IS A 40-50% CHANCE OF
SEEING AN ADDITIONAL 3 INCHES OF RAIN, A 30-60% CHANCE IN
PORTLAND, A 15-30% CHANCE AROUND KELSO, AND LESS THAN A 10%
CHANCE SOUTH OF SALEM. NOW WITH THAT SAID, THE SPACIAL COVERAGE
OF THE MODELS COMES INTO QUESTION. SOME STILL SUGGEST A BIT OF A
RAIN SHADOW EFFECT WITHIN THE INTERIOR VALLEYS, BUT BASED ON
THE DYNAMICS THERE LIKELY WILL BE LESS OF THIS EFFECT. THEREFORE
TRENDING ON THE HIGHER END OF THOSE PROBABILITIES.
PROBABILITIES FOR 5+ INCHES OF RAIN ARE LESS THAN 30% EXCEPT
ALONG THE CASCADES AS THE PRECIPITATION WILL BE OROGRAPHICALLY
LIFTED.
AS FAR AS SNOWFALL IS CONCERNED MAIN THREAT IS OVER THE SOUTH
WASHINGTON CASCADES WHERE A WINTER STORM WARNING REMAINS IN
EFFECT FOR THE GIFFORD PINCHOT NATL FOREST AND MT ADAMS THROUGH
EARLY FRIDAY MORNING TO ACCOUNT FOR A BRIEF SURGE IN
PRECIPITATION IN THE EVENING AND THE SOUTHERLY TRACK OF THE AR.
ADDITIONAL TOTALS THROUGH THIS PERIOD RANGE FROM 5-12 INCHES AT
2500-3000 FT UP TO NEARLY 20 INCHES ABOVE 4500-5000 FT. SURFACE
TEMPERATURES ALONG OREGON CASCADES HOVER RIGHT AROUND FREEZING
BUT WITH HEAVIER RAIN WE ARE SEEING SOME PERIODS OF DYNAMIC
COOLING AND THEREFORE SEEING A WET SNOW AROUND THE MT HOOD NATL
FOREST ABOVE 3500 FT. WILL SEE SOME ACCUMULATION, THOUGH WITH
THE WEIGHT MAY DIMINISH OVERALL GAINS.
THE LOCATION OF THE ATMOSPHERIC RIVER WILL ULTIMATELY BE KEY
THROUGH FRIDAY IN REGARDS TO HOW MUCH PRECIPITATION WE WILL SEE
AND WHAT TYPE. WHILE PREVIOUS MODELS SHOWED US ON THE SOUTHERN
OUTSKIRTS OF THE AR, OBSERVATIONS ARE SHOWING A SLIGHTLY
DIFFERENT STORY. EXPECTING MOST PRECIPITATION TO FALL AS RAIN
BELOW 3500-4000 FT. HOWEVER, IF THE COLD AIR DIPS FURTHER
SOUTH, THEN THE SNOW RATIOS WILL INCREASE AND ACCUMULATION WILL
RISE. SEVERAL HIGH-RESOLULATION MODELS LIKE THE NAMNEST ALSO
PRESENT A INTERESTING "DYNAMIC COOLING" SCENARIO ACROSS THE
LOWER ELEVATIONS OF SOUTHWEST WASHINGTON FRIDAY MORNING. THE
COOLER AIR ON THE NORTH SIDE OF THE FRONTAL BOUNDARY AND HIGH
PRECIPITATION RATES COMBINE TO ARTIFICIALLY PUSH SNOW LEVELS
LOWER, POTENTIALLY NEAR 500FT. THERE IS SIGNIFICANT UNCERTAINTY
AS WHETHER THIS WILL ACTUALLY UNFOLD AND CONFIDENCE IS VERY LOW
DUE TO THE COMPLEXITY OF THE SET-UP, BUT'S IT'S SOMETHING WE'LL
HAVE TO WATCH CLOSELY MOVING FORWARD. PROBABILISTICALLY, THERE
IS AROUND A 10-30% CHANCE OF SEEING ACCUMULATING SNOW WITHIN THE
COWLITZ LOWLANDS, WITH THE HREF SHOWING AROUND A 10% CHANCE OF
SEEING 3 INCHES OF SNOW IN AREAS LIKE CASTLE ROCK, WA. THE
GROUND REMAINS WARM THOUGH SO SNOW THAT DOES FALL WILL STRUGGLE
TO ACCUMULATE DUE TO THE NUMBER OF DAYS OF WARM TEMPERATURES
LEADING UP TO THE POTENTIAL COLD AIR. AGAIN, CONFIDENCE REMAINS
QUITE LOW BUT THE HIGHEST PROBABILITY TIMEFRAME WOULD BE LATE
TONIGHT INTO FRIDAY MORNING WHEN WE SEE THE MOST NIGHT-TIME
COOLING. -27
LONG TERM...SATURDAY THROUGH WEDNESDAY
RAIN TAPERS OFF ON
SATURDAY AS A HIGH PRESSURE RIDGE BUILDS IN OVER THE PACIFIC.
MAY STILL SEE SOME LINGERING SHOWERS OVER THE NORTH OREGON AND
SOUTH WASHINGTON CASCADES, BUT WILL BE LIMITED AND WOULD FALL AS
LIGHT SNOW DUE TO COOLER TEMPERATURES ALOFT. THIS RIDGE WILL
PREVAIL THROUGH SUNDAY AND WILL HAVE A GREAT IMPACT ON WHAT
HAPPENS EARLY NEXT WEEK.
MODELS SHOW YET ANOTHER ATMOSPHERIC RIVER MOVING IN LATE SUNDAY
INTO MONDAY HOWEVER MOST ENSEMBLES MAINTAIN A NORTHERLY
TRAJECTORY. IF THIS HIGH REALLY AMPLIFIES, IT WILL PUSH THE
SYSTEM TO OUR NORTH AND WE WOULD MAINTAIN DRIER AND MUCH WARMER
CONDITIONS. HOWEVER, IF THE JET STREAM AND DYNAMICS OF THE
SYSTEM CAN OVERPOWER THE RIDGE THEN THE AR WILL SHIFT SOUTHWARD
AND THUS WE COULD SEE RAIN ONCE AGAIN. THERE IS AROUND A 10-25%
CHANCE OF SEEING ACCUMULATING RAIN ON SUNDAY WITH THE HIGHEST
CHANCES WITHIN SOUTHWEST WASHINGTON.
TEMPERATURES WILL RISE AS THE WARM AIR MOVES IN FROM THE SOUTH.
THERE CONTINUES TO BE HIGH UNCERTAINTY DUE TO THE POTENTIAL FOR
THIS SECOND AR, BUT RIGHT NOW WE ARE SEEING HIGH TEMPERATURES
WELL ABOVE NORMAL IN THE UPPER 60S FOR INLAND SITES, AND NEAR 60
ALONG THE COAST. IN FACT, FOR HIGHS ON TUESDAY, THERE IS A 10%
CHANCE OF A TEMPERATURE AROUND 78 DEG F IN EUGENE AND IN THE
70S ALONG THE COAST. IF WE SEE TEMPERATURES THIS HIGH, THEN
SNOWMELT IN THE CASCADES IS PROBABLE. -27
AVIATION
EXPECT CIG/VIS CONDITIONS TO VARY THROUGH THE DAY AS
AN ATMOSPHERIC RIVER MOVES THROUGH THE REGION. OVERALL THROUGH THE
TAF PERIOD, INLAND TERMINALS WILL LIKELY STAY MVFR WITH
OCCASIONAL IFR CONDITIONS FROM HEAVIER RAIN, WHILE COASTAL
TERMINALS WILL BOUNCE BETWEEN MVFR AND LIFR. WITH RECENT
OBSERVATIONS AND GUIDANCE, EXPECT CONDITIONS AT KAST TO LEAN
TOWARDS MVFR WITH POSSIBLE IFR, WHILE KONP WILL LIKELY LEAN
TOWARDS IFR/LIFR CONDITIONS. SOUTHWESTERLY WIND GUSTS HAVE MOSTLY
STOPPED AND LIGHT WINDS HAVE SHIFTED MORE WESTERLY, BUT EXPECT
WIND GUSTS TO SHIFT SOUTHWESTERLY AND INCREASE AGAIN AROUND
00-06Z FRIDAY. FROM 00-06Z FRIDAY TO THE END OF THE TAF PERIOD,
EXPECT WIND GUSTS AROUND 25 KT INLAND AND UP TO 30 KT ALONG THE
COAST, MOSTLY AT KONP.
ANOTHER POTENTIAL FOR LLWS WILL BEGIN AROUND 00-03Z FRIDAY FOR
TERMINALS NEAR THE COLUMBIA RIVER GORGE. WITH SURFACE WINDS
EXPECTED TO INCREASE AROUND 00-06Z FRIDAY AND WINDS ALOFT EXPECTED
TO INCREASE AROUND 00-03Z FRIDAY, THE LLWS THREAT SHOULD NOT BE AS
SIGNIFICANT, BUT STILL NOTICEABLE, ESPECIALLY FOR AIRPORTS THAT
ARE NOT WITHIN NORTH-SOUTH ALIGNED TERRAIN. LLWS WILL LIKELY BE IN
THE FORM OF SPEED SHEAR RATHER THAN DIRECTIONAL SHEAR.
KPDX AND APPROACHES...AN ATMOSPHERIC RIVER WILL CONTINUE TO BRING
STEADY RAIN AND MOSTLY MVFR CIGS THROUGH THE TAF PERIOD.
SOUTHWESTERLY WIND GUSTS HAVE STOPPED THIS MORNING, BUT WILL
INCREASE AND GUST UP TO 20-25 KT BEGINNING AROUND 06Z FRIDAY. LLWS
WILL BE PRESENT AFTER 03Z FRIDAY, ALTHOUGH NOT AS SIGNIFICANT DUE
TO STRONGER SURFACE WINDS AND LLWS BEING MOSTLY SPEED SHEAR
RATHER THAN DIRECTIONAL. ~12
MARINE
CONDITIONS HAVE BEGUN TO IMPROVE AS A LOW PRESSURE
SYSTEM INLAND HAS SHIFTED EASTWARD. WIDESPREAD GALES HAVE
DISSIPATED WITH ONLY A FEW ROGUE GUSTS PERIODICALLY REMAINING.
HAZARDOUS DO REMAIN FOR THE NEXT FEW HOURS BUT ARE QUICKLY
EASING TO 12-14 FT AT 11-12 SECONDS. THE NORTHERN WATERS OF
PZZ251/271 HAVE MAINTAINED HIGHER SEAS AROUND 14-15 FT, BUT
THOSE TOO WILL SLOWLY EASE. SMALL CRAFT ADVISORIES WILL FOLLOW
THROUGH TODAY BEFORE LOWERING TO JUST BELOW 10 FT. THERE IS A
10% CHANCE OF MAINTAINING 10-11 FT SEAS THROUGH FRIDAY MORNING
BUT AT THIS TIME CONFIDENCE IS NOT HIGH ENOUGH TO EXTEND.
HIGH PRESSURE BUILDS OVER THE WATERS ON SATURDAY AND WILL
PERSIST THROUGH AT LEAST SUNDAY. MAY SEE SOME PERIODS OF WIND
GUSTS UP TO 25 KT, BUT WILL BE SHORT-LIVED AND ISOLATED.
-27
HYDROLOGY
HYDROLOGICAL CONCERNS HAVE INCREASED OVERNIGHT AS
AT LEAST ONE RIVER HAS RISEN TO MINOR FLOOD STAGE (THE WILSON
NEAR TILLAMOOK) AND THE GRAYS RIVER NEAR ROSBURG HAS REACHED
MODERATE FLOOD STAGE. FLOOD RISK REMAINS THROUGH FRIDAY AS THE
ATMOSPHERIC RIVER BRINGS A PROLONGED PERIOD OF MODERATE TO HEAVY
RAINFALL TO PORTIONS OF WESTERN OREGON AND SOUTHWEST
WASHINGTON. WHILE WE HAVE ALREADY SEEN EXCEPTIONAL RAINFALL OVER
THE LAST 12 HOURS, THERE IS STILL A LEVEL OF UNCERTAINTY IN
REGARDS TO WHERE THE HEAVIEST RAINFALL WILL SET UP TODAY INTO
FRIDAY. A NUMBER OF FLOOD WATCHES, INCLUDING AN AREAL FLOOD
WATCH, REMAIN IN EFFECT THROUGH FRIDAY. WHILE MOST MAIN-STEM
RIVERS HAVE LESS THAN A 5% CHANCE OF MINOR FLOODING, A FEW OF
OUR "FLASHIER" RIVERS HAVE GREATER CHANCES. THE PUDDING RIVER AT
AURORA, JOHNSON CREEK NEAR SYCAMORE, AND THE WILSON/TRASK NEAR
TILLAMOOK ARE EXPECTED TO REACH MINOR FLOOD STAGE WITH A 5-20%
TO REACH MODERATE. RIVER RESPONSES WILL LIKELY VARY IN TIME DUE
TO RAINFALL DURATION AND LOCATION, WITH SOME LIKELY OCCURRING
LATE TONIGHT THROUGH SATURDAY, AND OTHERS OCCURRING LATE TODAY
THROUGH SATURDAY. THE ADDITION OF ANY SNOWMELT OFF OF THE
CASCADES MAY AMPLIFY WATER INFLUX TO AREA TRIBUTARIES. THE MOST
LIKELY OUTCOME AT THIS TIME IS ELEVATED RIVER LEVELS AND WITHIN-
BANK RISES, THOUGH TRENDS WILL NEED TO BE MONITORED.
PQR WATCHES/WARNINGS/ADVISORIES
OR...WINTER WEATHER ADVISORY UNTIL 11 PM PDT THIS EVENING FOR
ORZ126.
WA...WINTER STORM WARNING UNTIL 5 AM PDT FRIDAY FOR WAZ211.
PZ...SMALL CRAFT ADVISORY UNTIL 5 PM PDT THIS AFTERNOON 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