081
FXUS66 KPQR 191033
AFDPQR
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE PORTLAND OR
233 AM PST FRI DEC 19 2025
SYNOPSIS
RAINFALL RATES ARE NOW ON A SHARP DOWNTREND EARLY
THIS MORNING THANKS TO THE ATMOSPHERIC RIVER DEPARTING THE
REGION. THAT SAID, WE'LL CONTINUE TO SEE IMPACTS IN THE FORM OF
RIVER FLOODING FOR THE NEXT 24-48 HOURS. HIGH CONFIDENCE IN
WIDESPREAD MINOR AND MODERATE RIVER FLOODING WITH EVEN MAJOR
RIVER FLOODING FOR THE CLACKAMAS RIVER NEAR ESTACADA TODAY INTO
SATURDAY. AT LEAST A COOLER POST-FRONTAL AIRMASS ENSURES SOME
MUCH NEEDED CASCADE SNOWFALL INTO WEEKEND. EXPECT A FAIRLY
ACTIVE AND PROGRESSIVE WEATHER PATTERN TO PERSIST THROUGH THE
MIDDLE OF NEXT WEEK. ADDITIONAL WEATHER IMPACTS BY SUNDAY ONWARD
APPEAR MUCH MORE IN-LINE WITH CLIMATOLOGICAL NORMS FOR MID TO
LATE DECEMBER.
SHORT TERM...NOW THROUGH SUNDAY NIGHT
CURRENT SATELLITE AND
RADAR OBSERVATIONS EARLY THIS MORNING SHOW OUR POTENT
ATMOSPHERIC RIVER AND THE ACCOMPANYING FRONTAL BOUNDARY NOW
PUSHING SOUTHEASTWARD OUT THE REGION WITH COLDER AND SHOWERY
POST- FRONTAL CONDITIONS RAPIDLY TAKING HOLD. WINDS HAVE BEEN ON
THE DECREASE AS WELL. THIS TRANSITION WILL LARGELY BRING AN END
TO ANY ADDITIONAL AREAL, URBAN, AND/OR SMALL STREAM FLOODING.
ALTHOUGH, SHOULD ANY HEAVIER SHOWER BANDS TRAIN OVER AN AREA FOR
AN EXTENDED PERIOD OF TIME ON FRIDAY, ESPECIALLY WITH THE
ALREADY SATURATED SOILS IN MIND, WE COULD OBSERVE SOME
ADDITIONAL LOCALIZED IMPACTS. WE ARE STILL NOT OUT OF THE WOODS
REGARDING RIVER FLOODING HOWEVER (SEE HYDRO SECTION). IT'S WORTH
HIGHLIGHTING COME THE AFTERNOON HOURS TODAY MOST DETERMINISTIC
MODELS PROJECT AROUND 100-300 J/KG OF MUCAPE EXTENDING INTO THE
MIXED PHASED (-10C TO -20C) REGION OF THE ATMOSPHERE SUPPORTIVE
OF ISOLATED LIGHTNING STRIKES. GIVEN THE SET-UP, CERTAINLY NOT
EXPECTING WIDESPREAD ACTIVITY WITH A 10-20% CHANCE OF
THUNDERSTORMS EXTENDING FROM THE COAST INTO THE INTERSTATE 5
CORRIDOR. ANTICIPATE LOCALLY HEAVY RAIN, SMALL HAIL, A LIGHTNING
STRIKE OR TWO, AND BRIEF GUSTY WINDS WITH ANY "STRONGER"
CONVECTION. ISOLATED THUNDERSTORM ACTIVITY LIKELY REVERT CLOSER
TO THE COASTLINE WITH THE LOSS OF DAYTIME HEATING POST-SUNSET.
ON A SLIGHTLY MORE POSITIVE NOTE FOR ALL THE SKIERS/SNOWBOARDERS
OUT THERE (THIS FORECASTER INCLUDED) THE COLDER AIRMASS
FILTERING IN OVERHEAD DROPS SNOW LEVELS TO ROUGHLY 2000-3500
FEET IN THE CASCADES BY MIDDAY TODAY WITH FAIRLY FREQUENT SNOW
SHOWERS CONTINUING INTO SATURDAY MORNING BEFORE THESE SHOWERS
DECREASE. THE HEAVIEST SNOW DURING THIS PERIOD IS LIKELY ABOVE
~3000 FEET, EXCEPT FOR ABOVE 4500 FEET IN THE LANE COUNTY
CASCADES, WITH 6-12 INCHES EXPECTED AT PASS LEVEL AND SLIGHTLY
MORE ABOVE THE ABOVE PASSES. A WINTER WEATHER ADVISORY REMAINS
IN EFFECT INTO SATURDAY MORNING AS A RESULT. PREPARE TO WINTER-
LIKE DRIVING CONDITIONS IF YOU PLAN TO TRAVERSE ACROSS THE
MOUNTAIN PASSES THIS WEEKEND.
COME SATURDAY NIGHT INTO SUNDAY DETERMINISTIC AND ENSEMBLE
GUIDANCE MAINTAIN BROAD WEST-SOUTHWEST ALLOW ALOFT GRADUALLY
GAINING A SOUTHERLY COMPONENT AS A LONG WAVE TROUGH FEATURE
BEGINS TO SLOWLY AMPLIFY OVER THE EASTERN PACIFIC. SHOWERS
PERSIST THROUGH THIS PERIOD PERSIST, MOST LIKELY ALONG THE COAST
AND COAST RANGE, BEFORE A MID-LEVEL WAVE FEATURE AND COLD-
FRONTAL BOUNDARY INCREASE SHOWER ACTIVITY WHOLESALE SUNDAY
AFTERNOON. THAT SAID, GIVEN THE SOUTHERLY COMPONENT TO THE FLOW
SNOW LEVELS TOP OUT AROUND 3000-5000FT LATE SUNDAY KEEPING
SNOWFALL IMPACTS CONFINED CLOSER TO THE PASSES. FROM 4AM SUNDAY
THROUGH SUNDAY NIGHT UNTIL 4AM MONDAY, CONFIDENCE IS DECENT
(40-65% GOV CAMP/SANTIAM) FOR IN AT LEAST ANOTHER 6IN+ OF
SNOWFALL, ALTHOUGH DUE TO LOCALLY HIGHER SNOW LEVELS NEAR
WILLAMETTE PASS THIS PROBABILITY IS NOTICEABLY LOWER THERE
(20-30%). STILL, ANY SNOW WILL HELP AT THIS POINT OF THE YEAR
GIVEN OUR CURRENT DEFICIT. -99
LONG TERM...MONDAY THROUGH THURSDAY
EARLY NEXT WEEK BOTH
DETERMINISTIC AND ENSEMBLE GUIDANCE ARE IN GOOD AGREEMENT
RESOLVING THE OVERALL LONGWAVE PATTERN, AT LEAST TO START. A
LARGER UPPER-LEVEL TROUGHING FEATURE OVER THE EASTERN PACIFIC
WILL REMAIN RELATIVELY STATIONARY THROUGH MONDAY NIGHT WITH THE
VERTICALLY STACKED LOW TO MID LEVEL HEIGHT FIELDS CENTERED JUST OFF
THE COAST OF CENTRAL BRITISH COLUMBIA. MODELS SHOW ADDITIONAL
SHORTWAVE IMPULSES ROTATING AROUND THIS BROADER FEATURE
PROVIDING PERIODIC INCREASES IN PRECIPITATION ACROSS THE
PACIFIC NORTHWEST, AND LIKE ON SUNDAY, THERE IS MODERATE
CONFIDENCE ANOTHER ONE OF THESE SHORTWAVES ARRIVES THE SECOND
HALF OF MONDAY INTO MONDAY NIGHT. BUT, THE EXACT DETAILS
REGARDING IMPACTS WITH THIS AND OTHER SUBTLE WAVES FEATURES ARE
UNCERTAIN AT THIS POINT THROUGH WEDNESDAY. BY THE MIDDLE OF THE
WEEK THE AFOREMENTIONED UPPER LEVEL TROUGH IS EXPECTED TO
TRANSITION INTO A CLOSED LOW WHILE RETROGRADING AND DROPPING
SOUTHWARD LEAVING US IN BOARD SOUTHERLY FLOW. FROM THIS POINT
ONWARD FORECAST UNCERTAINTY SIGNIFICANTLY INCREASES AS MODEL
GUIDANCE STRUGGLES TO RESOLVE THE PLACEMENT OF THIS BROAD CLOSED
LOW AND THE SHORTWAVE DISTURBANCES ROTATING AROUND IT. AT THE
VERY LEAST THE VAST MAJORITY OF MODEL ENSEMBLE MEMBERS HOLD THE
AXIS OF HEAVIEST RAINFALL WELL TO OUR SOUTH IN CALIFORNIA. KEEP
AN EYE ON THE FORECAST THIS WEEK, ESPECIALLY THOSE WHO HAVE
TRAVEL PLANS AROUND THE HOLIDAY. -99
AVIATION
VFR TO MVFR CONDITIONS CONTINUING ACROSS THE MAJORITY
OF THE AIRSPACE AS A COLD FRONT PROGRESSES OUT OF THE AREA. BEHIND
THE COLD FRONT, EXPECT WINDS TO BECOME MORE SOUTHWESTERLY AS
WELL AS DECREASE TOWARDS 10-15 KT OR LESS. FLIGHT CONDITIONS
ARE EXPECTED TO TREND MORE TOWARDS VFR WITH OCCASIONAL MVFR
BEHIND THE FRONT AS WELL.
A 15-30% PROBABILITY FOR THUNDERSTORMS IS ALSO EXPECTED ACROSS
THE AIRSPACE STARTING AROUND 15-18Z FRIDAY AND LIKELY THROUGH
12Z SATURDAY (MAINLY NEAR THE COAST). ANY THUNDERSTORMS COULD
PRODUCE LOCALLY GUSTY WINDS AND SMALL HAIL.
KPDX AND APPROACHES...MVFR/VFR CONDITIONS EXPECTED TO CONTINUE
THROUGH THE TAF PERIOD WITH SHOWERY PRECIPITATION. A 15-20%
PROBABILITY FOR THUNDERSTORMS ALSO RETURNS AROUND 18-20Z
SATURDAY THROUGH 03Z SATURDAY. ANY THUNDERSTORMS COULD PRODUCE
LOCALLY GUSTY WINDS AND SMALL HAIL. -99/42
MARINE
WINDS CONTINUE TO GUST TO LESS THAN 20 KT FOR MOST OF
THE WATERS AS THE COLD FRONT CONTINUE TO DISTANCE ITSELF FROM THE
AREA. WINDS REMAIN FROM THE WEST TO NORTHWEST IN THE WAKE OF THE
FRONT THROUGH FRIDAY NIGHT. SEAS IN THE LOW TO MID TEENS AT 10-12
SECONDS WILL KEEP SEAS VERY STEEP THROUGH THE OVERNIGHT. A
HAZARDOUS SEAS WARNING REMAINS IN PLACE THROUGH 10 AM FRIDAY. SEAS WILL
DROP BACK TO AROUND 10 FEET FRIDAY MORNING, REMAINING STEEP
THROUGH THE EVENING. SEAS REMAIN AROUND 8-10 FEET AT 10-12
SECONDS THROUGH THE WEEKEND. WINDS TURN SOUTHWESTERLY ON SATURDAY
AS ANOTHER SYSTEM APPROACHES THE WATERS. WIND GUSTS CREEP INTO
THE 25-30 KT RANGE SATURDAY AFTERNOON, LIKELY REQUIRING ANOTHER
SMALL CRAFT ADVISORY TO BE ISSUED DURING A LATER FORECAST PACKAGE.
THE ACTIVE PATTERN CONTINUES INTO NEXT WEEK AS A SERIES OF SYSTEMS
MOVES THROUGH THE AREA BRINGING ROUND OF ELEVATED WINDS AND SEAS.
THE EXACT DETAILS ARE UNCLEAR AT THIS TIME. /19
HYDROLOGY
WHILE THE STEADIEST AND HEAVIEST RAINFALL IS ON THE
DECREASE EARLY THIS MORNING, IMPACTS ARE STILL RAMPING UP AS
RIVERS CONTINUE TO RESPOND ACROSS THE REGION. A NUMBER OF RIVER
POINTS HAVE ALREADY REACHED MINOR TO MODERATE FLOOD STAGE WITH
AROUND 20-25 TOTAL RIVER POINTS FORECAST TO REACH AT LEAST MINOR
FLOOD STAGE TODAY THROUGH TONIGHT. CURRENTLY ONLY ONE RIVER
POINTS IS FORECAST TO AND HAS JUST ACTUALLY JUST REACHED MAJOR
FLOOD STAGE; THE CLACKAMAS RIVER NEAR ESTACADA, BUT THE
CLACKAMAS RIVER NEAR OREGON CITY, AND JOHNSON CREEK NEAR
SYCAMORE WILL BE RATHER CLOSE. RIVER FLOODING WILL CONTINUE FOR
THE NEXT 24-48 HOURS, WITH SOME SLOWER RESPONDING LOCATIONS
CONTINUING TO SEE IMPACTS THIS WEEKEND. THESE RIVER FORECASTS
REMAIN VERY SENSITIVE TO ADDITIONAL RAINFALL AND PRECIPITATION
WILL BE SHOWERY AND HIT/MISS IN NATURE TODAY. THE LATEST RIVER
FORECASTS ACROSS THE REGION CAN BE FOUND AT
WWW.WATER.NOAA.GOV/WFO/PQR.
PQR WATCHES/WARNINGS/ADVISORIES
OR...COASTAL FLOOD ADVISORY FROM 10 AM THIS MORNING TO 4 PM PST
THIS AFTERNOON FOR ORZ101>103.
WINTER WEATHER ADVISORY FROM 4 AM EARLY THIS MORNING TO 10 AM
PST SATURDAY FOR ORZ126-127.
WINTER WEATHER ADVISORY FROM 4 AM EARLY THIS MORNING TO 4 AM
PST SATURDAY FOR ORZ128.
WA...WINTER WEATHER ADVISORY FROM 4 AM EARLY THIS MORNING TO 10 AM
PST SATURDAY FOR WAZ211.
PZ...HAZARDOUS SEAS WARNING UNTIL 10 AM PST THIS MORNING FOR PZZ210-
251>253-271>273.
SMALL CRAFT ADVISORY FROM 10 AM THIS MORNING TO 9 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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