456
FXUS66 KPQR 171224 AAA
AFDPQR
AREA FORECAST DISCUSSION...UPDATED
NATIONAL WEATHER SERVICE PORTLAND OR
424 AM PST WED DEC 17 2025
UPDATED AVIATION DISCUSSION.
SYNOPSIS
A STRONG FRONTAL SYSTEM BROUGHT GUSTY WIND AND HEAVY
RAIN TO THE REGION THIS MORNING, WITH RAIN EXPECTED TO PERSIST
THROUGH THE REMAINDER OF THE DAY. THE NEXT SIGNIFICANT WEATHER
SYSTEM IS A STRONG ATMOSPHERIC RIVER THAT WILL ARRIVE ON
THURSDAY. HIGH PROBABILITY OF FLOODING, CASCADE SNOW, AND
POTENTIALLY ANOTHER ROUND OF GUSTY WINDS. RAIN PERSISTS THROUGH
EARLY NEXT WEEK.
SHORT TERM...NOW THROUGH FRIDAY NIGHT
THIS MORNING CAN BE
DESCRIBED IN JUST A FEW WORDS: STRONG FRONTAL PASSAGE WINDS.
MUCH OF THE AREA EXPERIENCED GUSTS RANGING FROM 35 MPH UP TO 55
MPH IN THE INTERIOR LOWLANDS, AND AROUND 65 MPH ALONG THE COAST.
WHILE SHORT LIVED, THE IMPACTS HAVE BEEN HIGH WITH WIDESPREAD
POWER OUTAGES, DOWNED TREE BRANCHES, AND POTENTIALLY OTHERS THAT
ARE NOT OBSERVED AT THIS TIME. THIS WIND WILL BE FOLLOWED BY
POST FRONTAL SHOWERS THAT HAVE THE POTENTIAL OF PRODUCING MORE
STRONG OUTFLOW WIND GUSTS AND THUNDER. RAIN PERSISTS THROUGH THE
DAY TODAY BUT OVERALL WILL HAVE LITTLE IMPACT. TODAY WE WILL
ALSO SEE A POTENTIAL FOR THUNDERSTORMS DUE TO THE CONVECTIVE
NATURE OF THE ENVIRONMENT AND SUPPORT ALOFT. SNOW LEVELS TODAY
WILL DROP TO AROUND 2500 FT AND THUS, SNOW IN THE CASCADES IS
LIKELY. ACCUMULATION WILL VARY BASED ON PRECIPITATION RATES AND
COULD SEE LESSER AMOUNTS DUE TO THE FACT THAT THE GROUND IS
STILL QUITE WARM. CURRENT FORECAST SHOW AROUND 6-11 INCHES OF
SNOW IN THE SOUTH WASHINGTON CASCADES, AND AROUND 4-7 INCHES FOR
THE OREGON CASCADES AT PASS LEVEL. THERE IS A 10% CHANCE OF
SEEING WARNING LEVEL SNOW AMOUNTS TODAY.
THURSDAY IS THE DAY WE HAVE REALLY ALL BEEN LOOKING TOWARDS AS
BEING THE MOST RISK PRONE DAY IN REGARDS TO WEATHER. A STRONG
ATMOSPHERIC RIVER WILL PASS OVER THE REGION THROUGH THE DAY
STARTING IN THE MORNING. SYNOPTICALLY THE SYSTEM CONTINUES TO
SHIFT NORTH AND SOUTH WITH NOW A MORE NORTHERLY SHIFT. SO WHY
DOES THIS KEEP HAPPENING - ESPECIALLY WHEN IT'S JUST 24-HOURS
OUT? ONE DRIVING FORCE OF THIS IS THE PRESSURE GRADIENT OF A LOW
PRESSURE SYSTEM IN THE NORTHEAST PACIFIC. AS THAT LOW SHIFTS
NORTH, THE AR FOLLOWS SUIT WITH A SIMILAR TREND AS THE LOW MOVES
SOUTHWARD. WHILE ONLY A 50 MILE DIFFERENCE BETWEEN THE SOUTHERN
BOUNDARY OF THE AR, THE IMPACTS WILL SHIFT AND WHICH AREAS WILL
SEE THE MOST PRECIPITATION. IN ADDITION, BECAUSE THE AR IS
ASSOCIATED WITH WARM AIR A NORTHERLY TRACK WILL MAKE GETTING
SNOW MORE DIFFICULT THAN IN PREVIOUS MODEL RUNS. WILL CONTINUE
TO MONITOR. THIS STRONG FRONT WILL PUSH THROUGH INTO FRIDAY.
NOW LET'S DIVE INTO SOME OF THE NUMBERS TO PAINT A PICTURE OF
THE LEVEL OF UNCERTAINTY THAT ACCOMPANIES THIS SYSTEM. THE
CURRENT FORECAST FAVORS THE HEAVIEST RAIN BEGIN ALONG THE
CENTRAL OREGON COAST RANGE, THE CASCADES NORTH OF LINN COUNTY,
AND THE INTERIOR LOWLANDS SOUTH OF MARION COUNTY. THE 48 HOUR
RAINFALL TOTAL (REPRESENTING THE ENTIRE STORM) RANGES FROM 4.25
INCHES ALONG THE COAST TO 4.75 INCHES IN THE CENTRAL OREGON
COAST RANGE. IN THE CASCADES, PRECIPITATION WILL BE MUCH HIGHER
WITH ANYWHERE FROM 6.0-7.75 INCHES OF PRECIPITATION FORECAST.
IF WE WANT TO OBSERVE THE "WORST CASE" SCENARIO (10% CHANCE OF
OCCURRING) WE COULD SEE GREATER THAN 6.5 INCHES IN THE CENTRAL
OREGON COAST RANGE, 2.75 IN THE WILLAPA HILLS, NEARLY 4.0-4.5
INCHES IN THE WILLAMETTE VALLEY FROM SALEM NORTH, AND AROUND 5
INCHES AROUND EUGENE. WITH EQUAL PROBABILITY IS THE "DRY END"
SCENARIO. IF THIS WERE TO MANIFEST, RAINFALL TOTALS WOULD BE
DRASTICALLY DIFFERENT. THE SAME AREAS WOULD SEE THE BULK OF THE
RAIN BUT THE IT WOULD DROP TO AROUND 2.5 INCHES IN THE CENTRAL
OREGON COAST RANGE, TO 1.25 INCHES IN THE WILLAPA HILLS, 2
INCHES AROUND EUGENE, AND AROUND 1 INCH IN PORTLAND. ULTIMATELY,
GIVEN THE STRENGTH OF THE AR INDICATING INDICES, THOSE LOW END
AMOUNTS HAVE A VERY MINIMAL CHANCE OF OCCURRING.
TO WRAP UP THE WEATHER ON THURSDAY WE MUST ADDRESS WIND AND
SNOW. WINDS WILL BE ELEVATED AND BASED ON SURFACE PRESSURE
GRADIENTS IT APPEARS WE MAY SEE ANOTHER HINT OF A WEAK COASTAL
JET FORMING EARLY ON IN THE FRONTAL PASSAGE. HIGH RESOLUTION
ENSEMBLES SHOW THE PEAK PERIOD OF WIND GUSTS INLAND WOULD BE IN
THE AFTERNOON WITH THE MEAN SITTING AROUND PEAK GUSTS OF 35
MPH. NOW TRADITIONALLY THE HIGHER RESOLUTION GUIDANCE HAS A
TENDENCY TO OVERPERFORM ON WIND SPEEDS. HOWEVER, IN THIS
SCENARIO GIVEN THE OVERALL PATTERN WE CANNOT RULE OUT GUSTS OF
THESE SPEEDS. SNOW WILL BE A BIT MORE CHALLENGING DUE TO THE
NATURE OF ARS AND THAT BY DESIGN ARE WARM. SNOWFALL TOTAL
PROBABILITY IS HIGHEST IN THE SOUTH WASHINGTON CASCADES AS THEY
ARE MOST LIKELY TO SIT IN THE COOLEST AIR.
TRANSITIONING INTO FRIDAY, THE RAIN WILL CONTINUE THOUGH WILL
BE MUCH LIGHTER. THE MAIN IMPACT ON FRIDAY WILL BE THE
PROBABILITY OF FLOODING. SEE THE HYDROLOGY DISCUSSION FOR MORE
DETAILS. SNOW LEVELS WILL DROP ONCE AGAIN ON FRIDAY DOWN TO PASS
LEVEL. BECAUSE THE WARMEST PORTION OF THE FRONT WILL HAVE
PASSED, THE CHANCES FOR SNOW ARE HIGHEST ON FRIDAY. AT THIS
POINT CONFIDENCE IS QUITE LOW THOUGH AS THERE ARE MANY FACTORS
THAT ARE GOING TO ALTER THE PROBABILITIES FOR SNOW. HOWEVER, TO
GIVE JUST A BIT OF AN IDEA, THERE IS A 15-20% CHANCE OF WARNING
LEVEL SNOW ON THE PASSES WITH HIGHER PROBABILITY ALONG THE
VOLCANOES, AND A 50-70% CHANCE OF ADVISORY LEVEL SNOW (6-12
INCHES). -27
LONG TERM...SATURDAY THROUGH TUESDAY
THE WEEKEND WILL FEEL
LIKE THE CALM AFTER THE STORM BUT IT IS ANYTHING BUT THAT. WE
WILL STILL SEE CONTINUED RAINFALL BUT IT WILL BE MORE
CLIMATOLOGICALLY NORMAL. SOUTH TO SOUTHWESTERLY FLOW WILL ALSO
BRING BREEZY CONDITIONS TO INTERIOR VALLEYS AND EVEN THE
COLUMBIA RIVER GORGE. THE COMPONENT ABOUT SATURDAY TO KEEP AN
EYE ON IS THAT WE WILL SEE CONTINUED FLOODING FROM THE RISING
THAT OCCURRED ON THURSDAY AND FRIDAY. MANY RIVERS ARE FORECAST
TO BE IN A FLOOD STAGE ON THAT DAY.
AS MOIST ZONAL FLOW THEN CONTINUES THROUGH THE WEEKEND,
PERSISTENT LOWLAND RAIN AND HIGH ELEVATIONS SNOW CHANCES ALSO
CONTINUE. WHILE THE DETAIL REMAIN RELATIVE LOW CONFIDENCE,
CURRENT LONG-RANGE GUIDANCE DOES NOT FAVOR ANOTHER HIGH-END
RAINFALL EVENT THROUGH THE MIDDLE OF NEXT WEEK. BUT DON'T LET
THAT CATCH YOU OFF OF YOUR FEET. 500 MB HEIGHTS AND OTHER
SYNOPTIC FEATURES ARE SUGGESTING A BROAD TROUGH TAKING OVER
MUCH OF THE NORTHEAST PACIFIC. THIS TROUGH IS ASSOCIATED WITH A
COLD WRAPPED LOW THAT WILL PRODUCE WEAK IMPULSES. THESE
DISTURBANCES WILL THEN PUSH OVER THE REGION. WHILE NOT WELL
REALIZED AT THIS TIME, RAIN WILL PERSIST THROUGH TUESDAY. -27/36
AVIATION
POST FRONTAL SHOWERS THIS MORNING WILL BE HEAVY AT
TIMES WITH GUSTY WINDS ALOFT. AT AROUND 1000 FT MSL GUSTS AS
HIGH AS 30 KT HAVE BEEN OBSERVED FROM THE WEST. DUE TO THE
UNIDIRECTIONAL NATURE OF THE WIND AND THE DECAYING SYSTEM HAVE
OMITTED LLWS BUT CANNOT RULE OUT PERIODS DURING THE HEAVIEST
SHOWERS. GENERALLY VFR THROUGH THE DAY WITH LINGERING RAIN
SHOWERS. CONDITIONS BEGIN TO DEGRADE AFTER 10Z THURSDAY AS A
STRONG ATMOSPHERIC RIVER APPROACHES. MOST OF THE STRONG WINDS
AND HEAVY RAIN WILL OCCUR AFTER THE TAF PERIOD, BUT MAY
EXPERIENCE SOME PERIODS OF HEAVIER RAIN AND GUSTY WINDS ALONG
THE LEADING EDGE. THERE IS A 45% CHANCE OF MVFR CIGS AFTER 11Z
THU.
DUE TO A VERY STRONG FRONT OVERNIGHT, SEVERAL ASOS AND AWOS HAVE
BEEN LEFT WITHOUT POWER AND OBSERVATIONS MAY BE UNAVAILABLE.
KPDX AND APPROACHES...VFR THROUGH MOST OF THE NEXT 24-HRS.
ISOLATED PERIODS OF LLWS WITH POST FRONTAL SHOWERS BEHIND THE
STRONG FRONT OVERNIGHT. SHOWERY CONDITIONS PERSIST THROUGH THE
DAY WITH WEST TO SOUTHWESTERLY WINDS. MAY SEE TIMES WITHOUT
RAIN, BUT GIVEN THE OVERALL PATTERN WILL BE SHORT LIVED. -27
MARINE
CONDITIONS OVERNIGHT HAVE BEEN LESS INTENSE THAN
PREVIOUSLY THOUGH ASIDE FROM THE WIND FORECAST THAT REMAINS ON
TRACK. OVERALL HAVE SEEN SEAS AROUND 14 FT AT 10 SECONDS ASIDE
FROM AROUND BUOY 46050 WHERE SEAS OF 17 FT WERE OBSERVED WITH
THE PASSING STRONG FRONTAL SYSTEM. ONE REASON COULD BE THAT THE
BACKGROUND SWELL WAS WEAKER THAN FORECAST AND THUS THE SEAS WERE
PREDOMINATELY WIND WAVE DRIVEN. AT THIS POINT, NOT EXPECTING
SEAS ABOVE 18 FT AND IF THEY DO REACH THOSE HEIGHTS, IT WOULD
BE INDIVIDUAL AND ISOLATED WAVES. WINDS WILL REMAIN WEST TO
NORTHWEST WITH GUSTS GREATER THAN 35 KT THROUGH THE MORNING
BEFORE FALLING TO 15 TO 20 KT WITH GUST SUP TO 30 KT. SEAS WILL
CONTINUE TO BE HAZARDOUS THROUGH THE DAY.
WITH THE INCOMING STRONG SYSTEM GALES ARE ONCE AGAIN EXPECTED
WITH SIMILAR SPEEDS AS EXPERIENCED THIS MORNING. A WEAK LOW
LEVEL JET WILL FORM THURSDAY MORNING AND PERSIST THROUGH THE
EVENING. GUSTS WILL BE HIGHEST WITHIN PZZ252-253. SEAS WILL
BUILD TO AROUND 14-16 FT. THERE IS AROUND A 5-10% CHANCE OF
SEAS OF 18-20 FT BUT CONFIDENCE IS QUITE LOW AT THIS TIME.
-27
HYDROLOGY
POTENTIAL FOR RIVER FLOODING IS HIGHEST ON
THURSDAY AND FRIDAY DUE TO THE ABUNDANT RAINFALL FROM AN
ATMOSPHERIC RIVER. HEAVIEST RAINFALL OCCURS FOR A RELATIVELY
SHORT PERIOD OF TIME FROM THURSDAY THROUGH THURSDAY NIGHT. THE
ALREADY SATURATED SOILS AND HIGH RIVERS COMBINED WITH THE
INCOMING WELL ABOVE NORMAL RAINFALL HAS RESULTED IN AN ELEVATED
RISK FOR FLOODING LATE THIS WEEK. AS IS TYPICAL IN ATMOSPHERIC
RIVERS, THE HIGHEST RAINFALL TOTALS ARE LIKELY TO BE OVER AREAS
OF TERRAIN INCLUDING THE COAST RANGE AND CASCADES, WHILE LESSER
TOTALS CAN BE EXPECTED ACROSS INLAND VALLEYS. NONETHELESS,
RAINFALL IS LIKELY TO BE MEASURED IN INCHES ACROSS MOST OF THE
REGION. ONE DIFFERENCE BETWEEN THE LAST SERIES OF ARS AND THE
ONE ARRIVING ON THURSDAY IS THE PLACEMENT OF HIGHEST RAINFALL
TOTALS. THIS NEXT SYSTEM FAVORS A MORE SOUTHERN MAXIMUM, AND
THUS AREAS THAT PREVIOUSLY MISSED THE HEAVIEST RAIN WILL SEE THE
HIGHER ACCUMULATIONS THIS TIME AROUND.
DUE TO THE LACK OF OBSERVED RAIN, PARTICULARLY IN LANE COUNTY,
SOME BASINS WILL BE MORE CAPABLE OF HANDLING HEAVY RAINFALL
WITHOUT EXPERIENCING FLOODING. OTHER AREAS TO THE NORTH WITHIN
THE COAST RANGE IN LINCOLN, TILLAMOOK, BENTON, POLK, YAMHILL,
AND WASHINGTON COUNTIES MAY SEE MORE OVERLAP BETWEEN RECENTLY
OBSERVED HEAVY RAINFALL AND ADDITIONAL HIGH TOTALS WITH THIS
UPCOMING SYSTEM. SIMILARLY, RIVER BASINS COVERING THE CENTRAL OR
CASCADES IN LANE AND LINN COUNTIES MAY HAVE A SLIGHTLY MORE
OPTIMISTIC OUTLOOK THAN NORTH INTO MARION AND CLACKAMAS
COUNTIES, BUT THAT DOES NOT MEAN FLOODING CANNOT HAPPEN IN ALL
OF THE AFOREMENTIONED AREAS. LUCKILY, WHERE RAINFALL HAS SO FAR
BEEN THE HEAVIEST ACROSS SOUTHWESTERN WASHINGTON AND FAR
NORTHWESTERN OREGON MAY SEE THE LOWEST TOTALS FROM THIS SYSTEM,
ALTHOUGH EVEN 1-2 INCHES OF RAIN OVER 24 HOURS MAY BE ENOUGH TO
CAUSE ADDITIONAL FLOODING IN THESE VERY SATURATED AREAS.
AT THIS POINT, THE RIVERS WITH THE HIGHEST CHANCES OF REACHING
FLOOD STAGE ARE THOSE WHICH DRAIN THE CENTRAL OREGON COAST
RANGE, INCLUDING THE WILSON, TRASK, SILETZ, AND SIUSLAW DRAINING
TOWARD THE COAST, AND THE MARYS, LUCKIAMUTE, YAMHILL, AND
TUALATIN DRAINING TOWARD THE WILLAMETTE. THE CHANCES FOR THESE
RIVERS TO REACH AT LEAST MINOR FLOOD STAGE ARE 30-70% AT THIS
TIME. THOSE DRAINING TOWARD THE COAST, PARTICULARLY IN LINCOLN
AND LANE COUNTIES WHERE RAINFALL IS LIKELY TO CONTINUE LATER
INTO FRIDAY MAY SEE MINOR TIDAL OVERFLOW AS RIVERS CRESTS
COINCIDE WITH HIGH TIDE ON FRIDAY, THOUGH THIS OCCURRENCE
REMAINS LOWER CONFIDENCE. RIVERS DRAINING THE CASCADES,
INCLUDING THE MOHAWK, SANTIAM, PUDDING, MOLALLA, CLACKAMAS, AND
SANDY, HAVE SLIGHTLY LOWER BUT STILL SIGNIFICANT CHANCES OF
15-45%. THESE RIVERS WILL BEGIN TO RISE LATER ON THURSDAY AS
HEAVY RAIN CONTINUES, NOT CRESTING UNTIL FRIDAY IN MOST CASES.
THE WILLAMETTE RIVER MAIN STEM ITSELF ALSO HAS A 5-10% CHANCE OF
REACHING FLOOD STAGE ABOVE WILLAMETTE FALLS, AND SLIGHTLY
HIGHER CHANCES IN TIDALLY- INFLUENCED PORTIONS DOWNSTREAM OF
OREGON CITY, HOWEVER RUNOFF WILL TAKE LONGER TO REACH THE
WILLAMETTE AND FLOODING WOULD BE DELAYED LATER THAN IN ITS
TRIBUTARIES. A FLOOD WATCH REMAINS IN EFFECT ACROSS ALL OF
NORTHWESTERN OREGON AND SOUTHWESTERN WASHINGTON FROM 4 AM
THURSDAY THROUGH 4 AM SATURDAY TO HIGHLIGHT THESE RISKS.
THESE RIVER FORECASTS REMAIN VERY SENSITIVE TO RAINFALL
FORECASTS, AND INTERESTED PARTIES SHOULD EXPECT CHANGES AS THE
EVENT NEARS. THE LATEST RIVER FORECASTS ACROSS THE REGION CAN BE
FOUND AT WWW.WATER.NOAA.GOV/WFO/PQR. -36
PQR WATCHES/WARNINGS/ADVISORIES
OR...HIGH WIND WARNING UNTIL 6 AM PST EARLY THIS MORNING FOR
ORZ101>103.
WIND ADVISORY UNTIL 6 AM PST EARLY THIS MORNING FOR ORZ104>107-
123>125.
WINTER WEATHER ADVISORY UNTIL 4 PM PST THIS AFTERNOON FOR
ORZ126>128.
WA...HIGH WIND WARNING UNTIL 6 AM PST EARLY THIS MORNING FOR WAZ201.
WIND ADVISORY UNTIL 6 AM PST EARLY THIS MORNING FOR WAZ202-203-
208.
WINTER WEATHER ADVISORY UNTIL 10 PM PST THIS EVENING FOR
WAZ211.
PZ...GALE WARNING UNTIL 10 AM PST THIS MORNING FOR PZZ210-251>253-
271>273.
HAZARDOUS SEAS WARNING FROM 10 AM THIS MORNING TO 10 PM PST
THIS EVENING 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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