066
FXUS66 KPQR 132124
AFDPQR
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE PORTLAND OR
224 PM PDT MON APR 13 2026
SYNOPSIS
SCATTERED LIGHT SHOWERS CONTINUE AT TIMES TODAY.
HOWEVER, OUR FOCUS REMAINS ON A STRONGER FRONTAL SYSTEM ARRIVING
TUESDAY EVENING THROUGH EARLY THURSDAY MORNING. THIS SYSTEM WILL
BRING WIDESPREAD PRECIPITATION TO THE REGION AND A PERIOD OF
HEAVY CASCADE SNOWFALL. AS A RESULT HAVE UPGRADED THE WINTER
STORM WATCH TO A WINTER STORM WARNING FROM LATE TUESDAY INTO
EARLY THURSDAY ABOVE 2500FT. IT SHOULD BE NOTED THAT THERE IS
AROUND A 5% CHANCE FOR WET, HEAVY SNOW TO BE OBSERVED ALONG WITH
SOME ACCUMULATION FOR ELEVATIONS ABOVE 1000 FT DURING THE TIMES
MENTIONED ABOVE. LOOKING BEYOND, WHILE SHOWERS IN THE WAKE OF
THE FRONT DECREASE, COOLER OVERNIGHT TEMPERATURES QUICKLY
FOLLOW WITH INCREASING FROST CONCERNS. THEN, LOOKING TOWARDS THE
END OF THE WEEK AND INTO THE WEEKEND A WARMING AND DRYING TREND
BRIEFLY RETURNS.
SHORT TERM...TONIGHT THROUGH WEDNESDAY NIGHT
AS WE MOVE INTO
THE EVENING HOURS, A WEAK, TRANSIENT RIDGE WILL CONTINUE TO
BUILD OVER THE AREA AND WILL LIKELY BRING A STOP TO THE MAJORITY
OF SHOWERS THAT HAVE IMPACTED THE CWA. WHILE MOST OF THE LOWER
ELEVATIONS WILL SEE A BRIEF DRY PERIOD, THAT CANNOT BE SAID FOR
ELEVATED LOCATIONS WITH THE COAST RANGE, CASCADES, AND ADJACENT
FOOTHILLS AS THEY COULD SEE LINGERING SHOWER ACTIVITY THROUGH
THE OVERNIGHT HOURS.
AS TUESDAY APPROACHES, A RATHER SIGNIFICANT PATTERN CHANGE IS
EXPECTED. MODELS ARE CURRENTLY IN EXCELLENT AGREEMENT THAT A
ROBUST LOW WILL DIVE OUT OF THE GULF OF ALASKA AND INTO THE PAC
NW. THIS SYSTEM WILL BRING ABOUT COOLER AIR, WIDESPREAD
PRECIPITATION AND SOME BREEZY CONDITIONS TO OUR CWA. AS THE
LEADING COLD FRONT OF THIS SYSTEM SWEEPS INTO THE AREA, EXPECT
BREEZY SOUTHERLY WINDS WITH GUSTS UP TO 25 MPH INLAND AND GUSTS
UP TO 35 MPH ALONG THE COAST. BY THE LATE MORNING/EARLY
AFTERNOON, WIDESPREAD PRECIPITATION WILL BE HERE ALONG WITH
COOLER, 850 MB TEMPERATURES. CURRENT MODEL AND ENSEMBLE GUIDANCE
IS SHOWING 850 MB TEMPERATURES IN THE -4 TO -5 C RANGE, WHICH
WILL BRING SNOW LEVELS DOWN TOWARDS 2000-3000 FT BY LATE
TUESDAY/EARLY WEDNESDAY. 24 HOUR RAINFALL AMOUNTS DURING THIS
PERIOD, GENERALLY RANGE FROM 0.80 TO 1.30 INCHES ACROSS THE
WILLAMETTE VALLEY AND PORTLAND METRO, 1.00 TO 2.25 INCHES ALONG
THE COAST AND COAST RANGE, AND 1.10 TO 2.30 INCHES ACROSS THE
CASCADES. HOWEVER, FOR THE LATTER REGION, ESPECIALLY AT PASS
LEVEL, THE PRECIPITATION WILL LIKELY BE FALLING AS SNOW.
SPEAKING OF SNOW, HAVE UPGRADED THE WINTER STORM WATCH TO A
WINTER STORM WARNING. THE INCOMING SYSTEM LOOKS TO BRING 12 TO
20 INCHES OF SNOWFALL TO THE CASCADES STARTING TUESDAY AFTERNOON
THROUGH EARLY THURSDAY MORNING, FOR ELEVATIONS ABOVE 2500 FT.
CURRENT NBM PROBABILITIES SHOW A 75-95% PROBABILITY OF 12 INCHES
OR GREATER SNOWFALL OVER A 48 HOUR PERIOD (TUESDAY AFTERNOON -
THURSDAY AFTERNOON), A 40-60% PROBABILITY OF 20 INCHES OR MORE
FOR ELEVATIONS ABOVE 4500 FT AND A 20-30% CHANCE FOR 25 INCHES
OR MORE FOR ELEVATIONS ABOVE 5500 FT. THE HIGHEST AMOUNTS IN
THE HIGH CASCADES FROM MARION TO LANE COUNTY. SO, IF YOU ARE
PLANNING ON GOING OVER THE CASCADE PASSES IN THE NEXT FEW DAYS,
PLEASE KEEP AN EYE ON ROAD CONDITIONS AS WELL AS ANY
INFORMATIONAL POSTS MADE BY LOCAL OFFICIALS.
IN ADDITION WE ARE KEEPING AN EYE ON THE INCOMING SYSTEM AS
THERE IS A LOW CHANCE (~5%) OF SOME WET SNOW ACCUMULATIONS ABOVE
1000 FT DURING THE SAME TIME PERIOD. IF THIS WERE TO OCCUR, WET
SNOW ALONG WITH THE INCREASE IN SURFACE AREA ON TREES VIA THE
GREEN UP, COULD RESULT IN IMPACTS OCCURRING. POTENTIAL IMPACTS
COULD BE DOWN TREE BRANCHES DUE TO WET SNOW LOAD AND THAT COULD
LEAD TO POWER OUTAGES. WHAT IS MORE LIKELY TO OCCUR (20-30%
CHANCE) IS THAT PEOPLE ABOVE 1000 FT IN ELEVATION COULD SEE
VISIBLE SNOW FALL (CHUNKY RAIN) IN THE SKY WITH NO IMPACTS. SO,
DON'T BE SURPRISED IF LATE TUESDAY/EARLY WEDNESDAY MORNING YOU
OBSERVE SNOW IN THE AIR.
LOOKING TOWARDS WEDNESDAY AND THE POST FRONTAL ENVIRONMENT,
OVERALL INSTABILITY INCREASES AS THE BODY OF THE UPPER LEVEL LOW
TREKS SOUTHEAST. THE STRATIFORM PRECIPITATION OF WEDNESDAY
MORNING WILL BECOME SHOWERY AS WEDNESDAY AFTERNOON/EVENING
APPROACHES. CONVECTIVE AVAILABLE POTENTIAL ENERGY (CAPE)
INCREASES WITH MODELS SHOWING VALUES OF 200-500 J/KG, WHICH IS
RATHER ROBUST FOR OUR CWA. THE MAIN TIME PERIOD OF FOCUS IS 11AM
TO 7PM ON WEDNESDAY WHEN HEATING BETWEEN SHOWER BANDS MAY BE
MAXIMIZED. GIVEN THIS INFORMATION, THERE IS A 15-25% CHANCE FOR
THUNDERSTORMS ACROSS THE MAJORITY OF OUR CWA. AS A REMINDER WITH
ANY THUNDERSTORMS EXPECTED MODERATE TO HEAVY RAIN, INFREQUENT
LIGHTNING, SMALL HAIL/GRAUPEL, GUSTY AND ERRATIC WINDS. SO, WHEN
THUNDER ROARS, GO INDOORS OR WHEN YOU SEE A FLASH (OF
LIGHTNING), DASH INSIDE. /42
LONG TERM...THURSDAY THROUGH SUNDAY
BY THURSDAY, THE UPPER
LEVEL LOW AND ASSOCIATED FRONT HAVE LEFT THE CWA, BUT WILL
LEAVE THE REGION COOL AND MOIST CONDITIONS. THURSDAY INTO FRIDAY
LOOKS TO HAVE OVERNIGHT LOWS IN THE MID 20S TO MID 30S. THIS
MEANS THAT THERE IS THE POTENTIAL FOR FROST DEVELOPMENT OR EVEN
FREEZING TEMPERATURES TO IMPACT THE VALLEY FLOOR. CURRENTLY,
THE PORTLAND/VANCOUVER METRO THERE IS A 10-40% CHANCE OF
OVERNIGHT LOWS AT OR BELOW 36 DEGREES F. FROM THE
PORTLAND/VANCOUVER METRO AREAS SOUTHWARD TOWARDS SALEM AND
EUGENE, OR, EXPECT A 45-85% CHANCE OF OVERNIGHT LOWS AT OR BELOW
36 DEGREES F. FOR LOCATIONS NORTH OF VANCOUVER, EXPECT A 50-75%
CHANCE OF OVERNIGHT LOWS AT OR BELOW 36 DEGREES F.
ADDITIONALLY, THERE IS A 80-95% CHANCE OF AT LEAST FREEZING
TEMPERATURES IN THE UPPER HOOD RIVER VALLEY FOR WEDNESDAY NIGHT
INTO THURSDAY MORNING. SIMILAR CONDITIONS MAY DEVELOP AGAIN
THURSDAY NIGHT INTO FRIDAY MORNING, THOUGH WITH SLIGHTLY LOWER
PROBABILITIES (ONLY 10-30% LOWER).
WHILE FROST POTENTIAL STARTS FOR MOST AREAS THURSDAY MORNING,
THE UPPER HOOD RIVER VALLEY WILL HAVE FROST POTENTIAL SOONER AND
LONGER, WITH A 45-85% CHANCE OF FROST WEDNESDAY MORNING, 90-99%
THURSDAY AND FRIDAY MORNING, AND 65-95% SATURDAY MORNING.
CHANCES OF FROST PLUMMET TO 10-35% BY SUNDAY MORNING FOR THE
UPPER HOOD RIVER VALLEY.
LOOKING TOWARDS THE WEEKEND, TEMPERATURES GRADUALLY WARM, REDUCING
FROST CONCERNS. ENSEMBLES SHOW A SHORTWAVE RIDGE OF HIGH PRESSURE
MOVING QUICKLY OVERHEAD ON SATURDAY, BUT BEING QUICKLY FOLLOWED
BY ANOTHER LOW PRESSURE SYSTEM ON SUNDAY ORIGINATING FROM THE
GULF OF ALASKA. NOW, BEYOND SUNDAY AND INTO THE START OF NEXT
WEEK, WPC CLUSTER GUIDANCE IS FAVORING THIS LOW HOLDING JUST
OFF THE OR/WA COAST OR MOVING OVER THE INLAND PAC NW, WHICH
MEANS THAT COOLER AND MOISTER CONDITIONS ARE FAVORED FOR THE
START OF NEXT WEEK. /42
AVIATION
NORTHWEST FLOW ALOFT WITH DIMINISHING SHOWERS TODAY.
PREDOMINATELY VFR CONDITIONS EXPECTED THROUGH TONIGHT, WITH ONLY
A 10-20% CHANCE OF MVFR OCCURRING WITH PASSING SHOWERS THROUGH
THIS EVENING. WESTERLY SURFACE WINDS AROUND 10 KT OR LESS CONTINUE
TODAY. A COLD FRONT WILL APPROACH THE REGION FROM THE NORTHWEST
TUESDAY MORNING, BRINGING INCREASING CHANCES FOR RAIN AND LOWER
CEILINGS TO THE AREA ON TUESDAY. CHANCES FOR MVFR CONDITIONS BEGIN
TO INCREASE AGAIN AFTER 12Z TUE AT THE COAST WHILE WINDS ARE
EXPECTED TO BECOME MORE SOUTHERLY AHEAD OF THE FRONT.
KPDX AND APPROACHES...PREDOMINATELY VFR CONDITIONS EXPECTED
THROUGH AT LEAST 18Z TUESDAY. SHOWERS WILL CONTINUE TO DIMINISH
THIS AFTERNOON. NORTHWEST WINDS AROUND 4-6 KT EXPECTED TO BECOME
SOUTHERLY BY 08Z TUESDAY, WITH SOUTH WINDS INCREASING TO AROUND
10-15 KT LATER TUE MORNING. /DH
MARINE
RELATIVELY CALM CONDITIONS ARE EXPECTED THROUGH THIS
EVENING AS WESTERLY WINDS PERSIST AT AROUND 10 KT OR LESS WITH
SEAS OF AROUND 5 TO 7 FT. SOUTHWESTERLY WINDS BEGIN TO INCREASE
LATER TONIGHT INTO TUESDAY AS A STRONG COLD FRONT APPROACHES THE
WATERS. EXPECT SOUTHWEST WINDS TO GUST UP TO 30 KT ACROSS ALL
COASTAL WATERS ON TUESDAY AS THE FRONT SLOWLY MOVES SOUTH. WINDS
ARE EXPECTED TO BE STRONGEST TUESDAY AFTERNOON INTO EARLY TUE
EVENING. DURING THIS TIME, THERE WILL BE AROUND A 3-6 HOUR PERIOD
WHEN GUSTS COULD (50% CHANCE) EXCEED 34 KT, PRODUCING MARGINAL
GALE FORCE WIND GUSTS. HAVE MAINTAINED THE STRONGLY WORDED SMALL
CRAFT ADVISORY BEGINNING EARLY TUE MORNING FOR THE NORTHERN WATERS
AND EXTENDING ACROSS ALL WATERS, INCLUDING THE COLUMBIA RIVER BAR,
TUE MORNING THROUGH TUE NIGHT. THE INCREASED WIND WAVES ARE
EXPECTED TO BUILD SEAS TO AROUND 10 TO 12 FT WITH A PERIOD OF
AROUND 8-10 SECONDS. SEAS REMAIN STEEP AND CHOPPY THROUGH TUE
NIGHT AS WELL.
WINDS ARE EXPECTED TO ABRUPTLY SHIFT TO THE NORTHWEST BEHIND THE
FRONTAL PASSAGE LATER TUESDAY THROUGH TUESDAY NIGHT AS THE COLD
FRONT MOVES SOUTH ACROSS THE COASTAL WATERS. BREEZY NORTHWEST
WINDS CONTINUE THROUGH WEDNESDAY WITH GUSTS INCREASING BACK UP TO
20-25 KT AS AN AREA OF LOW PRESSURE DROPS ALONG THE CANADIAN COAST
TOWARD THE PUGET SOUND. THIS WILL ALSO BRING A 15-25% CHANCE OF
THUNDERSTORMS OVER THE WATERS THROUGH WED EVENING. SEAS ARE
EXPECTED TO PERSIST AT AROUND AROUND 8 TO 10 FT ON WEDNESDAY,
BUILDING SLIGHTLY TO AROUND 9 TO 11 FT WED NIGHT AS A NORTHWEST
SWELL MOVES THROUGH THE WATERS. WILL LIKELY NEED TO EXTEND THE
SMALL CRAFT ADVISORY INTO THU MORNING. HIGH PRESSURE THEN BUILDS
OVER THE WATERS LATER THIS WEEK AS NORTHERLY WINDS RETURN AND SEAS
GRADUALLY SUBSIDE TO AROUND 4 TO 6 FT FRIDAY INTO SATURDAY. THERE
IS POTENTIAL FOR ANOTHER WEATHER SYSTEM TO IMPACT THE WATERS LATER
THIS WEEKEND. /DH
PQR WATCHES/WARNINGS/ADVISORIES
OR...WINTER STORM WARNING FROM 5 PM TUESDAY TO 5 AM PDT THURSDAY FOR
ORZ126>128.
WA...WINTER STORM WARNING FROM 5 PM TUESDAY TO 5 AM PDT THURSDAY FOR
WAZ211.
PZ...SMALL CRAFT ADVISORY FROM 8 AM TUESDAY TO 5 AM PDT WEDNESDAY FOR
PZZ210-252-253-272-273.
SMALL CRAFT ADVISORY FROM 5 AM TUESDAY TO 5 AM PDT WEDNESDAY FOR
PZZ251-271.
WWW.WEATHER.GOV/PORTLAND
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