017
FXUS66 KPQR 150614
AFDPQR
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE PORTLAND OR
1014 PM PST SUN DEC 14 2025
.UPDATED AVIATION AND MARINE DISCUSSION.
SYNOPSIS
A PAIR OF QUICK MOVING FRONTAL SYSTEMS ASSOCIATED
WITH SUBTROPICAL MOISTURE WILL BRING ADDITIONAL ROUNDS OF
HEAVIER RAINFALL AND RIVER RISES ON MONDAY AND TUESDAY. THE
PROBABILITY FOR EXCEEDING MINOR FLOOD STAGE FOR A HANDFUL OF
RIVERS HAS INCREASED TO AROUND 30-50%, MAINLY FOCUSED TOWARD
LATER IN THE WEEK. BREEZY TO GUSTY SOUTHERLY WINDS ARE ALSO
EXPECTED BOTH DAYS WITH THE STRONGEST WINDS LIKELY TUESDAY
NIGHT. ONSHORE FLOW CONTINUES WITH SHOWERS ON WEDNESDAY.
LOWERING SNOW LEVELS WILL ALLOW FOR SNOW TO FALL AT PASSES IN
THE CASCADES ON WEDNESDAY AND AGAIN BY FRIDAY. PRECIPITATION
CONTINUES THROUGH LATE NEXT WEEK, WITH POTENTIAL FOR ANOTHER
STRONG ATMOSPHERIC RIVER SYSTEM ON THURSDAY.
SHORT TERM...NOW THROUGH TUESDAY NIGHT
WATER VAPOR IMAGERY
THIS AFTERNOON REVEALS A LONG PLUME OF MOISTURE ORIGINATING NEAR
THE HAWAIIAN ISLANDS MOVING TOWARD THE WASHINGTON AND NORTHWEST
OREGON COASTS. A STRONG LOW PRESSURE SYSTEM IN THE GULF OF
ALASKA WILL DRAW THIS MOISTURE NORTHWARD WHILE A WARM FRONTAL
BAND SITS OVER VANCOUVER ISLAND TONIGHT INTO MONDAY MORNING.
PEAK IVT VALUES OF THE ASSOCIATED ATMOSPHERIC RIVER (AR) ARE
FAIRLY ROBUST AT AROUND 800- 1000 KG/M/S ACROSS COASTAL PARTS OF
SW WASHINGTON AND FAR NW OREGON. BUT, PEAK IVT VALUES ARE
EXPECTED TO MOVE THROUGH FAIRLY QUICKLY AS A TRAILING COLD FRONT
WILL PUSH ACROSS THE REGION LATER MONDAY MORNING THROUGH MONDAY
AFTERNOON.
THE SOUTHWEST ORIENTATION OF THE FLOW WITH THIS AR WILL ALSO IMPACT
LOCATIONS OF HEAVIEST RAINFALL. AS IS TYPICAL WITH THESE QUICK
MOVING SYSTEMS, HIGHEST ACCUMULATIONS ARE EXPECTED ALONG SOUTHWEST
FACING SLOPES OF THE COAST RANGE AND CASCADES MOUNTAINS. THE AREAS
WITH HIGHEST PROBABILITIES (35-55%) OF EXCEEDING 2 INCHES IN 12-24
HOURS THROUGH MONDAY EVENING ARE THE WILLAPA HILLS, NORTH OREGON
COAST RANGE, AND SOUTHWEST WA CASCADES AND FOOTHILLS. THESE WILL
CAUSE RIVER RISES, BUT AT THIS TIME FLOODING IS NOT EXPECTED.
RAINFALL AMOUNTS FOR INLAND LOWLANDS WITH THIS FIRST SYSTEM ARE MORE
LIKELY TO BE AROUND 0.25-0.75 INCH, WITH ONLY A 10% CHANCE OF
EXCEEDING 1 INCH THROUGH THE WILLAMETTE VALLEY, BUT AROUND A 40%
CHANCE IN THE KELSO/LONGVIEW AREA.
IMPACTS FROM WIND IS ALSO A CONCERN WITH THIS SYSTEM ON MONDAY.
SOUTHWESTERLY WINDS WILL BE STRONG ALOFT, WITH WIND SPEEDS OF AROUND
50-60 KT EXPECTED AT 925 MB. THESE STRONGEST WINDS WILL LIKELY BE
FELT AT HIGHER ELEVATIONS AND EXPOSED RIDGE TOPS, BUT COULD
POTENTIALLY MIX DOWN IF THE ENVIRONMENT BECOMES MORE CONVECTIVE WITH
THE FRONTAL PASSAGE. HAVE ISSUED A WIND ADVISORY STARTING LATE
TONIGHT THROUGH MONDAY AFTERNOON FOR THE COASTAL MOUNTAINS, WHERE
WIND GUSTS ARE EXPECTED TO REACH 45-50 MPH. A FEW ISOLATED GUSTS UP
TO 65 MPH WILL BE POSSIBLE, ESPECIALLY IN THE WILLAPA HILLS AND
NORTH OREGON COAST RANGE. ALSO EXPECTING WINDS TO GUST UP TO 40-50
MPH ALONG THE COAST MONDAY MORNING, AND UP TO 35 MPH INLAND. THERE
IS A 5-10% CHANCE THAT WIND GUSTS EXCEED 45 MPH THROUGH THE
WILLAMETTE VALLEY ON MONDAY. BUT, SATURATED SOILS DO INCREASE THE
CHANCES FOR DOWNED TREES AND ISOLATED POWER OUTAGES.
ALSO OF NOTE ON MONDAY IS THIS FRONT COMES WITH A SLIGHT (10-20%)
CHANCE OF THUNDERSTORMS. A FEW LIGHTNING FLASHES MAY OCCUR WHEREVER
DEEP-MOIST CONVECTION CAN DEVELOP AS COLDER TEMPERATURES ALOFT
ACCOMPANY THE UPPER TROUGH. IF A STRONGER STORM DOES MATERIALIZE,
ENOUGH DOWNWARD MOMENTUM FOR THE AFOREMENTIONED WINDS COULD SUPPORT
A FEW DAMAGING GUSTS, BUT CONFIDENCE IS LOW AT THIS TIME. EXPECT
DECREASING SHOWER ACTIVITY MONDAY NIGHT INTO TUESDAY MORNING.
THE REPRIEVE EARLY TUESDAY WILL BE SHORT LIVED AS ANOTHER 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, WITH THE HEAVIEST PRECIPITATION
EXPECTED BETWEEN 4 PM TUE - 4 AM WED. 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 OR SLIGHTLY HIGHER THAN MONDAY'S SYSTEM. MODELS AND THEIR
ENSEMBLES CONTINUE TO INDICATE THE POTENTIAL FOR STRONGER WINDS
TUESDAY NIGHT AS A RATHER ROBUST SHORTWAVE TROUGH PASSES OVER THE
REGION. SURFACE PRESSURE GRADIENTS ARE EXPECTED TO TIGHTEN ALLOWING
FOR SOUTHERLY WINDS TO INCREASE. NBM PROBABILITIES FOR WIND GUSTS
EXCEEDING 45 MPH (WIND ADVISORY CRITERIA) WITHIN THE INTERIOR
LOWLAND VALLEYS REMAINS AROUND 15-25%, THOUGH THINK THAT MIGHT BE A
BIT LOW, ESPECIALLY FOR THE CENTRAL WILLAMETTE VALLEY. LOWER CHANCES
FOR HIGH WINDS (GUSTS OF 58+ MPH) ALONG THE COAST AND CASCADE
FOOTHILLS. /DH
LONG TERM...WEDNESDAY THROUGH SATURDAY
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 THE HIGHER
END AMOUNTS HAVE COME DOWN (10% OR LESS CHANCE OF EXCEEDING 12
INCHES OF SNOW IN 24 HOURS), EXCEPT IN THE SOUTH WASHINGTON CASCADES
WHERE SNOW LEVELS ARE LIKELY TO DROP TO AROUND 2500-3000 FT. FOR
OREGON CASCADE PASSES, THERE REMAINS AROUND A 30-50% CHANCE FOR
EXCEEDING 6 INCHES OF SNOWFALL THROUGH WEDNESDAY NIGHT. THE NBM'S
10TH TO 90TH PERCENTILES AT BOTH SANTIAM PASS AND GOVERNMENT CAMP
GIVES A RANGE NOW OF AROUND 2 TO 11 INCHES OF SNOWFALL. SO, FOR
THOSE PREPARING TO TRAVEL OVER THE CASCADES, KEEP AN EYE ON THE
UPDATED FORECASTS.
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
AVIATION
SATELLITE AND RADAR OBSERVATIONS SHOW OUT NEXT
FRONTAL SYSTEM BEGINNING TO PROGRESS INTO THE REGION USHERING IN
WIDESPREAD RAIN AND AN INCREASE IN WINDS. WHILE CONDITIONS AS OF
06Z ARE PRIMARILY VFR INLAND, MVFR CIGS REMAIN FAVORED ONCE THE
STEADIEST/HEAVIEST RAIN BUILDS OVERHEAD WITH GENERALLY 10-25%
CHANCES OF IFR CIGS AFTER 12Z AT BOTH INLAND AND COASTAL
TERMINALS. SURFACE WINDS WILL ALSO CONTINUE TO INCREASE AS HIGH-
RESOLUTION GUIDANCE FAVORS WIND GUSTS REACHING AT LEAST 30-35 KT
ALONG THE COAST AND 20-25 KT INLAND. A 50-60 KT LOW-LEVEL JET OUT
OF THE SOUTH-SOUTHWEST AT ONLY A FEW THOUSAND FEET OFF THE SURFACE
WILL ADDITIONALLY YIELD INCREASING LOW-LEVEL WIND SHEAR OF 35-55
KT THROUGH MONDAY MORNING AT ALL TERMINALS. THIS SHEAR WILL BE
UNIDIRECTIONAL FOR MOST, HOWEVER SURFACE WINDS REMAINING
SOUTHEASTERLY LATER INTO THE PERIOD AT PORTLAND-AREA TERMINALS
WILL RESULT IN A DIRECTIONAL SHEAR COMPONENT AS WELL. IT'S WORTH
NOTING ONCE THE FRONT PASSES LATE MORNING INTO THE AFTERNOON
SHOWERS WILL TREND MORE SHOWERY IN NATURE BUT MAY BE FAIRLY
FREQUENT, ESPECIALLY ALONG THE COAST AND AROUND HIGHER TERRAIN
FEATURES.
KPDX AND APPROACHES...CURRENTLY AS OF 06Z VFR CONDITIONS ARE
HOLDING IN PLACE AS INTERMITTENT STRATIFORM RAINFALL BEGINS TO
OVERTAKE THE REGION. CIGS/VIS IS EXPECTED TO TREND TO MVFR BY
10-12Z MON WHILE WINDS TURN TOWARD THE SOUTH AND BUILD TO AROUND
15 KT WITH GUSTS TO 25 KT TONIGHT AND THROUGH MONDAY MORNING. SOME
HIGH-RESOLUTION GUIDANCE SUPPORTS EVEN STRONGER GUSTS EXCEEDING
30 KT, MOST LIKELY BETWEEN ~14-20Z MON. A STRONG LOW-LEVEL JET
OUT OF THE SOUTH-SOUTHWEST WILL ALSO SUPPORT LOW-LEVEL WIND SHEAR
OF 30-45 KT. THIS CONCERN RAPIDLY DISSIPATES ~19-20Z BEHIND THE
FRONTAL PASSAGE. -99/36
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...WIND ADVISORY UNTIL 4 PM PST MONDAY FOR ORZ106-107.
WA...WIND ADVISORY UNTIL 4 PM PST MONDAY FOR WAZ203.
PZ...SMALL CRAFT ADVISORY UNTIL 1 AM PST MONDAY FOR PZZ210-253-273.
GALE WARNING UNTIL 4 PM PST MONDAY FOR PZZ210-253-273.
HAZARDOUS SEAS WARNING FROM 4 PM MONDAY TO 4 AM PST TUESDAY
FOR PZZ210-251>253-271>273.
GALE WARNING UNTIL 4 PM PST MONDAY FOR PZZ251-252-271-272.
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