907
FXUS66 KPQR 140606
AFDPQR
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE PORTLAND OR
1006 PM PST SAT DEC 13 2025
UPDATED AVIATION AND MARINE DISCUSSIONS
SYNOPSIS
HIGH PRESSURE WILL MAINTAIN DRY WEATHER ACROSS NW
OREGON AND SW WASHINGTON THROUGH TONIGHT. ON SUNDAY, A WEAK
FRONT WILL MOVE OVER THE AREA BRINGING ANOTHER ROUND OF LIGHT
RAIN. A PAIR OF QUICK MOVING FRONTAL SYSTEMS ASSOCIATED WITH
SUBTROPICAL MOISTURE WILL BRING ADDITIONAL ROUNDS OF HEAVIER
RAINFALL AND RIVER RISES, THOUGH PROBABILITIES FOR EXCEEDING
MINOR FLOOD STAGE AT THE MAJORITY OF RIVERS REMAINS AROUND
20-25% OR LESS. BREEZY TO GUSTY SOUTHERLY WINDS ARE ALSO
EXPECTED WITH THE STRONGEST WINDS LIKELY TUESDAY NIGHT. ONSHORE
FLOW CONTINUES WITH SHOWERS ON WEDNESDAY. LOWERING SNOW LEVELS
WILL ALLOW FOR SNOW TO FALL AT PASS LEVEL IN THE CASCADES.
PRECIPITATION CONTINUES THROUGH LATE NEXT WEEK, WITH POTENTIAL
FOR ANOTHER STRONG SYSTEM ON THURSDAY.
DISCUSSION...TONIGHT THROUGH FRIDAY
WATER VAPOR SATELLITE IMAGERY
THIS AFTERNOON REVEALS AN UPPER LEVEL RIDGE SITUATED OVER THE
PACIFIC NORTHWEST, WITH THE MAIN RIDGE AXIS SHIFTING EAST OF THE
CASCADES. VISIBLE SATELLITE IMAGERY SHOWS WIDESPREAD STRATUS THROUGH
MUCH OF THE WILLAMETTE VALLEY, BUT SHOWING INDICATIONS OF SCATTERING
OUT, ESPECIALLY ALONG THE FRINGES WITH SKIES BECOMING MOSTLY SUNNY
THIS AFTERNOON. THERE IS A CHANCE SOME AREAS IN THE CENTRAL VALLEY
MAY REMAIN SOCKED IN THROUGHOUT THE DAY. WITH THE SURFACE INVERSION
IN PLACE, ALSO SEEING WARMER TEMPERATURES INTO THE MID-60S AT HIGHER
ELEVATIONS IN THE COAST RANGE AND FOOTHILLS OF THE CASCADES. GOOD
DAY FOR A HIKE!
INCREASING CLOUDS BY SUNDAY AS A WEAK FRONT APPROACHES THE COAST
EARLY SUNDAY MORNING. THE UPPER SHORTWAVE TROUGH QUICKLY LIFTS NORTH
INTO BRITISH COLUMBIA, REMOVING MUCH OF THE SYNOPTIC SUPPORT FOR
THIS SYSTEM, AND ALLOWING FOR THE FRONT TO DECAY AND DISSIPATE AS IT
PUSHES INLAND. RAINFALL AMOUNTS ARE NOT EXPECTED TO BE OVERLY
IMPRESSIVE ON SUNDAY, WITH MOST LIKELY AMOUNTS RANGING FROM 0.1-0.4
INCH ALONG THE COAST AND COAST RANGE, WHILE AMOUNTS WILL LIKELY
RANGE FROM A TRACE UP TO A QUARTER INCH INLAND, HIGHEST AMOUNTS IN
SOUTHWEST WA AND LOWEST TO THE SOUTH.
MORE ACTIVE WEATHER LOOKS TO RETURN BY MONDAY, AND CONTINUE THROUGH
MUCH OF NEXT WEEK. A BROAD UPPER LEVEL TROUGH WILL PERSIST OVER THE
PACIFIC AS STRONG LOW PRESSURE SYSTEMS SPIN IN THE GULF OF ALASKA
THROUGH LATE NEXT WEEK. A STRONG JET STREAM, ASSOCIATED WITH
SUBTROPICAL MOISTURE AT TIMES IS EXPECTED TO BE DIRECTED TOWARD THE
PACIFIC NW DURING THIS TIME. THE FIRST SYSTEM NEXT WEEK WILL BE
ASSOCIATED WITH IVT VALUES PEAKING AROUND 750-1000 KG/M/S, WHICH
WOULD PLACE IT IN THE STRONG ATMOSPHERIC RIVER CATEGORY. BUT, WHAT
MAKES THIS DIFFERENT FROM LAST WEEK'S AR EVENT IS BOTH A SHORTER
DURATION AND A MORE SOUTHWEST ORIENTATED FLOW. ENSEMBLES ARE
SUGGESTING THE INITIAL SURGE OF MOISTURE SUNDAY NIGHT INTO MONDAY
MORNING LIKELY REMAINS NORTH OVER WASHINGTON, BEFORE THE FRONT
QUICKLY PUSHES THROUGH NW OREGON, FOLLOWED BY MORE SHOWERY
CONDITIONS BY MONDAY AFTERNOON. MOST LIKELY RAINFALL TOTALS IN
COORDINATION WITH THE WPC THROUGH MONDAY EVENING HAS DECREASED
SOMEWHAT: AROUND 0.25-0.75 INCH WITHIN THE INTERIOR LOWLANDS, AND
FROM 0.75 UP TO 2 INCHES ALONG THE COAST AND COAST RANGE, AND
POTENTIALLY UP TO 2.5 INCHES IN 24 HOURS WITHIN THE CASCADES. THE
HIGHEST PROBABILITIES (50-70%) FOR EXCEEDING 2 INCHES OF RAINFALL ARE
IN THE HIGHER TERRAIN OF SW WASHINGTON AND THE NORTHERN OREGON COAST
RANGE, BUT CHANCES OF EXCEEDING 4 INCHES IS LESS THAN 10%. THE MAIN
CONCERN WITH THIS PATTERN REMAINS ON RIVERS THAT ARE RUNNING HIGH
FROM LAST WEEK'S RAINFALL.
ANOTHER CONCERN WITH THIS FIRST SYSTEM ON MONDAY WILL BE POTENTIAL
IMPACTS FROM WINDS. SOUTH TO SOUTHWESTERLY WINDS WILL LIKELY
INCREASE AHEAD OF THE SYSTEM LATE SUNDAY NIGHT INTO MONDAY MORNING.
WIND GUSTS ARE MOST LIKELY TO PEAK ALONG THE COAST AROUND 40-50 MPH
AND INLAND AROUND 25-35 MPH, THOUGH THERE IS AROUND A 10-20% CHANCE
OF WIND GUSTS EXCEEDING 40 MPH THROUGH THE WILLAMETTE VALLEY. THE
COMBINATION OF SATURATED SOILS AND THE STRONGEST WIND GUSTS COULD
PRODUCE ISOLATED DOWNED TREES AND POWER OUTAGES.
THE RAIN IS STILL EXPECTED TO EASE, WITH SCATTERED SHOWERS LIKELY
THROUGH TUESDAY MORNING. BUT, THE NEXT FRONTAL SYSTEM ARRIVES LATER
TUESDAY, BRINGING ANOTHER ROUND OF RAIN AND WIND. AGAIN, THIS
FRONTAL SYSTEM APPEARS TO MOVE FAIRLY QUICKLY ACROSS THE AREA
TUESDAY NIGHT. WHILE IVT VALUES ARE MODELED TO BE SLIGHTLY LOWER,
POTENTIALLY PEAKING AROUND 500-750 KG/M/S (MODERATE AR CATEGORY),
TOTAL RAINFALL AMOUNTS ARE LIKELY TO BE SIMILAR TO MONDAY'S SYSTEM.
MODELS AND THEIR ENSEMBLES ARE INDICATING THIS SYSTEM MAY BE MORE
DYNAMICALLY DRIVEN AS A STRONGER SHORTWAVE TROUGH AND ASSOCIATED
VORT MAX SLIDE ACROSS THE REGION. THIS ALSO SIGNALS TO POTENTIAL FOR
STRONGER, AND PERHAPS MORE IMPACTFUL WINDS ACROSS THE AREA TUESDAY
NIGHT. PROBABILITIES FOR WIND GUSTS EXCEEDING 40 MPH HAVE INCREASED
TO AROUND 50-60% THROUGH THE SOUTHERN AND CENTRAL WILLAMETTE VALLEY.
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 REMAINS
QUITE A LARGE SPREAD OF UNCERTAINTY FOR SNOWFALL AMOUNTS THROUGH
WEDNESDAY NIGHT, THOUGH PROBABILITIES FOR EXCEEDING 6 INCHES IS
AROUND 50%, AND 10-30% FOR EXCEEDING 12 INCHES IN 24 HOURS. (THE
NBM'S 10TH AND 90TH PERCENTILES AT SANTIAM PASS ARE CURRENTLY
SITTING AT 1 INCH TO 20 INCHES!) SO, IF YOU PLAN ON TRAVELING ACROSS
ANY OF THE CASCADES PASSES NEXT WEEK, KEEP AN EYE ON UPDATED
FORECASTS.
AS THE SYNOPTIC PATTERN PROGRESSES INTO LATE NEXT WEEK, UNCERTAINTY
ALSO REMAINS FAIRLY HIGH. THE GEFS AND ECMWF ENSEMBLES, WHICH WERE
QUITE DIFFERENT JUST 24-HOUR AGO, HAVE COME CLOSER TOGETHER, BUT THE
INDIVIDUAL MEMBERS REMAIN WILDLY SEPARATED. IT IS LIKELY (>90-95%
CHANCE) THE RAIN WILL CONTINUE THURSDAY AND FRIDAY, BUT RAINFALL
AMOUNTS ARE QUITE UNCERTAIN. THAT SAID, A STRONGER ATMOSPHERIC RIVER
APPEARS LIKELY TO SET UP SOMEWHERE ALONG THE WEST COAST LATE NEXT
WEEK, WITH THE HIGHEST PROBABILITIES FARTHER SOUTH NEAR THE OREGON-
CALIFORNIA BORDER. BUT IF THAT WERE TO SHIFT NORTH, WE COULD SEE
MUCH HIGHER RAINFALL AMOUNTS IMPACTING OUR FORECAST AREA.
AVIATION
LATE THIS EVENING LATEST SATELLITE IMAGERY AND
SURFACE OBSERVATIONS DEPICT A PERSISTENT FOG AND STRATUS LAYER
ACROSS THE WILLAMETTE VALLEY INTO SW WASHINGTON WITH A MIX OF IFR
TO LIFR CIGS AT INLAND TERMINALS. IT'S ALSO WORTH NOTING A SURGE
OF COASTAL STRATUS IS WORKING NORTHWARD FROM FLORENCE WHICH WILL
ALSO DEGRADE CONDITIONS OVERNIGHT AT SPOTS LIKE KONP. A FRONTAL
SYSTEM IS EXPECTED TO ARRIVE SUNDAY MORNING PROVIDING A MECHANISM
TO IMPROVE CIGS/VIS ALTHOUGH DUE TO THE WEAK NATURE OF THIS
INCOMING FEATURE IT STILL MAY TAKE UNTIL THE AFTERNOON TO SEE
APPRECIABLE IMPROVEMENT TO EITHER MVFR OR VFR. LOW CONFIDENCE IN
THE TIMING OF ANY IMPROVEMENT AS THE STRONG SURFACE TEMPERATURE
INVERSION AND ACCOMPANYING LOW STRATUS SET-UP IS NOTORIOUSLY
PESKY TO CLEAR OUT AND NOT HANDLED WELL BY MODEL GUIDANCE.
TERMINALS IN THE CENTRAL AND SOUTH WILLAMETTE VALLEY DO HOLD ONTO
A 20-30% CHANCE FOR IFR/LIFR CIGS TO EVEN PERSIST INTO SUNDAY
EVENING - SOMETHING TO WATCH. THIS PROBABILITIES ARE CLOSER TO
5-15% ELSEWHERE. LIGHT INTERMITTENT RAIN AND SHOWERS ARRIVE FROM
THE NORTHWEST BY 09-16Z SUN AT MOST SITES BEFORE DRIER WEATHER
RETURNS IN THE AFTERNOON BY 20-22Z.
KPDX AND APPROACHES...LOW STRATUS AND IFR CIGS CONTINUE TO SLOSH
AROUND THE PORTLAND/METRO WITH IFR CONDITIONS PERSISTING AT TIMES
THE REMAINDER OF THE NIGHT. ONCE LIGHT RAINFALL ARRIVES SUNDAY
MORNING, IMPROVEMENT TO MVFR/VFR IS MORE LIKELY BUT OVERALL
CONFIDENCE IN THE FORECAST FOR CIGS THROUGH THE MORNING IS LOW.
WINDS GENERALLY STAY BETWEEN 5-10 KNOTS THROUGH THE TAF PERIOD.
-99
MARINE
A WEAK FRONTAL SYSTEM MOVES THROUGH THE COASTAL WATERS
ON SUNDAY WILL BRING AN END TO SOME OF THE CALMER CONDITIONS WE'VE
BEEN EXPERIENCING THE LAST COUPLE OF DAYS WITH SMALL CRAFT
ADVISORIES IN EFFECT THROUGH SUNDAY EVENING DUE TO HIGH CONFIDENCE
IN WIND GUSTS OF 20-25 KT AND A RISE IN SEAS TO 7-10 FT. OVERALL
THIS FIRST SYSTEM WILL SERVE AS A NICE APPETIZER FOR MORE THE
IMPACTFUL CONDITIONS WE'RE EXPECTING THIS COMING WEEK.
THEN ON MONDAY A STRONGER WEATHER SYSTEM LOOKS TO AFFECT THE
COASTAL WATERS, ONE IN A STRING OF SEVERAL GOING FORWARD. JUST AHEAD
OF A STRONG COLD FRONT, A TIGHT PRESSURE GRADIENT WILL FAVOR
WIDESPREAD SOUTHERLY GALES FROM LATE SUNDAY EVENING THROUGH MONDAY
AFTERNOON WHILE A BUILDING WEST-SOUTHWESTERLY SWELL WILL SEE SEAS
RISE ABOVE 15 FT BY MONDAY MORNING. THERE REMAINS HIGH CONFIDENCE
IN GALE FORCE WINDS WITH A GALE WARNING IN EFFECT FROM SUNDAY
NIGHT THROUGH MONDAY AFTERNOON. STILL IT'S WORTH HIGHLIGHTING
THERE IS STILL A 20-40% CHANCE FOR PEAK GUSTS TO BREAK INTO THE
STORM FORCE CATEGORY MONDAY MORNING ACROSS THE INNER WATERS, AND
5-25% CHANCE ACROSS THE OUTER WATERS. MEANWHILE, SEAS MOST LIKELY
BUILD TO 16-19 FT BY MONDAY AFTERNOON. CHANCES FOR SEAS ABOVE 15
FT ARE HIGH, 65-95%, BEYOND 10 NM AND NORTH OF CASCADE HEAD, AND
LESS SO TO THE SOUTH AND EAST. CHANCES SEAS REACH 18 FT OR GREATER
ARE ONLY 15-35% BEYOND 30 NM NORTH OF CAPE FALCON, AND LESS THAN
10% ELSEWHERE.
THE WEATHER PATTERN THEN LOOKS TO REMAIN EXTREMELY ACTIVE THROUGH
THE MIDDLE AND LATTER PORTIONS OF NEXT WEEK. SEAS ARE VERY LIKELY
TO REMAIN ELEVATED ABOVE 10 FT (GREATER THAN 90% CONFIDENCE), AND
POSSIBLY (50% CHANCE OR HIGHER) ABOVE 15 FT ON WEDNESDAY AND
THURSDAY AS ANOTHER POTENT WEATHER SYSTEM MOVES ONSHORE. -99/36
PQR WATCHES/WARNINGS/ADVISORIES
OR...DENSE FOG ADVISORY UNTIL 10 AM PST SUNDAY FOR ORZ116>118.
WA...NONE.
PZ...SMALL CRAFT ADVISORY UNTIL 1 AM PST MONDAY FOR PZZ210-253-273.
GALE WARNING FROM 1 AM TO 4 PM PST MONDAY FOR PZZ210-253-273.
SMALL CRAFT ADVISORY UNTIL 10 PM PST SUNDAY FOR PZZ251-252-271-
272.
GALE WARNING FROM 10 PM SUNDAY TO 4 PM PST MONDAY FOR PZZ251-
252-271-272.
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