435
FXUS66 KPQR 010455 AAA
AFDPQR
AREA FORECAST DISCUSSION...UPDATED
NATIONAL WEATHER SERVICE PORTLAND OR
954 PM PDT TUE MAR 31 2026
UPDATED AVIATION DISCUSSION.
SYNOPSIS
A WEAK TROUGH WILL MAINTAIN LIGHT RAIN SHOWERS
ACROSS THE AREA THROUGH THIS EVENING. A STRONGER FRONTAL SYSTEM
ARRIVES WEDNESDAY, BRINGING WIDESPREAD RAIN, CASCADE SNOW, AND
BREEZY SOUTH-SOUTHWESTERLY WINDS THROUGH THURSDAY. ACCUMULATING
SNOW ALONG THE CASCADE PASSES WILL RESULT IN HAZARDOUS TRAVEL
CONDITIONS FROM WEDNESDAY TO THURSDAY MORNING, ESPECIALLY ALONG
SANTIAM AND WILLAMETTE PASSES WHERE SNOWFALL RATES MAY EXCEED 1
INCH PER HOUR. HIGH PRESSURE REBUILDS FRIDAY INTO THE WEEKEND,
RETURNING DRY WEATHER, SUNNIER SKIES, AND A WARMER TEMPERATURES.
SHORT TERM...TODAY THROUGH THURSDAY NIGHT
RADAR IMAGERY AS OF
EARLY TUESDAY AFTERNOON DEPICTS LIGHT SCATTERED SHOWERS ACROSS
NORTHWEST OREGON AND SOUTHWEST WASHINGTON AS A WEAK TROUGH
BRINGS MOISTURE TO THE AREA. CHANCES FOR PRECIPITATION LAST
THROUGH THIS EVENING AND ARE AROUND AROUND 20-40% WEST OF THE
CASCADES AND 40-60% ACROSS THE CASCADES. WINDS GRADUALLY TURN
MORE SOUTHERLY TODAY AHEAD OF THE NEXT SYSTEM THAT WILL ARRIVE
TOMORROW.
THE NEXT ROBUST SYSTEM ARRIVES ON WEDNESDAY AS AN UPPER LEVEL
TROUGH TRACKS SOUTHEASTWARD FROM THE GULF OF ALASKA AND SWINGS A
FRONTAL SYSTEM ACROSS THE PACIFIC NORTHWEST. THIS WILL RETURN
WIDESPREAD RAIN, BREEZY SOUTHERLY/SOUTHWESTERLY WINDS, AND
CASCADE SNOW ACROSS THE REGION. THE MAJORITY OF ENSEMBLE MEMBERS
FROM THE HIGH-RESOLUTION REFS SUGGESTS THAT PRECIPITATION FROM
THE INITIAL WARM FRONT WILL BEGIN ALONG THE COAST EARLY
WEDNESDAY MORNING (AFTER MIDNIGHT-2 AM). PRECIPITATION WILL
GRADUALLY SPREAD INLAND AND PERSIST THROUGH WEDNESDAY AFTERNOON
AS THE TRAILING COLD FRONT FOLLOWS.
BEHIND THE COLD FRONT, PRECIPITATION TURNS SHOWERY AND COOLER
AIR WILL FILTER IN THE AREA. SNOW LEVELS WILL GRADUALLY DROP TO
2000-3000 FT BY WEDNESDAY EVENING, RESULTING IN ACCUMULATING
SNOW ALONG THE CASCADE PASSES AND POTENTIAL TRAVEL IMPACTS. THE
WINTER STORM WATCHES HAVE BEEN UPGRADED TO WINTER STORM WARNINGS
FOR THE MARION, LINN, AND LANE COUNTY CASCADES FROM 5 AM
WEDNESDAY TO 5 PM THURSDAY. THERE IS HIGH CONFIDENCE (70-80%
CHANCE) FOR 1 FOOT OF SNOW OR MORE ALONG SANTIAM AND WILLAMETTE
PASSES BETWEEN 11 AM WEDNESDAY TO 11 AM THURSDAY. BASED ON REFS
ENSEMBLE GUIDANCE, THERE IS ALSO A 25-50% CHANCE FOR SNOWFALL
RATES OF 1+ INCH PER HOUR AT ANY GIVEN HOUR DURING THIS TIME
PERIOD ALONG THESE PASSES, WITH THE HIGHEST CHANCES OCCURRING
BETWEEN 11 PM WEDNESDAY AND 5 AM THURSDAY. MEANWHILE, LOWER SNOW
AMOUNTS ARE FORECAST NORTH OF THE MARION COUNTY CASCADES;
THEREFORE, WINTER WEATHER ADVISORIES WERE ISSUED FOR THE NORTH
OREGON AND SOUTH WASHINGTON CASCADES INSTEAD OF WARNINGS. IF YOU
HAVE PLANS TO TRAVEL THROUGH THE CASCADES, MAKE SURE TO PACK AN
EMERGENCY SUPPLY KIT AND REFER TO ODOT/WSDOT FOR THE LATEST
ROAD CONDITIONS AND RESTRICTIONS.
WEST OF THE CASCADES, MINIMAL IMPACTS ARE EXPECTED FROM THE RAIN
AND WIND. THE HIGHEST CHANCES FOR 48-HOUR RAINFALL EXCEEDING 1
INCH ENDING THURSDAY AFTERNOON ARE AROUND 40-60% ACROSS THE
SOUTHERN WILLAMETTE VALLEY AND 70-90% FOR THE COAST SOUTH OF
ASTORIA. AS THE COLD FRONT PUSHES THROUGH ON WEDNESDAY
MORNING/EARLY AFTERNOON, SOUTHWESTERLY WINDS WILL STRENGTHEN
WITH GUSTS UP TO 20-30 MPH FOR INTERIOR VALLEYS, WITH STRONGER
GUSTS OF 30-40 MPH FOR HIGHER TERRAIN AND ALONG THE COAST.
CHANCES FOR STRONGER WIND GUSTS ALONG THE COAST (50+ MPH) AND
ACROSS THE WILLAMETTE VALLEY/SOUTHWEST WASHINGTON LOWLANDS (40+
MPH) ARE AROUND 10-25% AT ANY GIVEN HOUR DURING THE FRONTAL
PASSAGE. ANOTHER POTENTIAL IMPACT FOR THE LOWLANDS IS A 10-20%
CHANCE FOR THUNDERSTORMS WEDNESDAY AFTERNOON/EVENING. COOLER AIR
ALOFT BEHIND THE COLD FRONT WILL INCREASE ATMOSPHERIC
INSTABILITY, AND MODEL SOUNDINGS SUPPORT THIS WITH SKINNY CAPE
PROFILES AND CAPE VALUES BETWEEN 100-150 J/KG. ANY PASSING
THUNDERSTORMS MAY PRODUCE LIGHTNING, BRIEF HEAVY DOWNPOURS THAT
REDUCE VISIBILITY, SMALL HAIL, AND LOCALLY ERRATIC WINDS.
LOWLAND RAIN SHOWERS AND CASCADE SNOW SHOWERS CONTINUE ON THURSDAY
BUT GRADUALLY DECREASE THROUGHOUT THE DAY AS THE SYSTEM WEAKENS AND
EXITS THE REGION. THURSDAY NIGHT TO FRIDAY MORNING, CLEARING SKIES
AND CALM WINDS WILL LEAD TO EFFICIENT RADIATIONAL COOLING AND
TEMPERATURES DROPPING INTO THE LOW TO MID 30S ACROSS INTERIOR
VALLEYS. THIS WOULD SUPPORT FROST DEVELOPMENT OVER VEGETATION AND
METAL SURFACES. GIVEN THAT APRIL 1ST MARKS THE START OF GROWING
SEASON, WE MAY NEED TO ISSUE FROST/FREEZE HEADLINES DURING THIS
TIME. -10
LONG TERM...FRIDAY TO MONDAY
ENSEMBLE GUIDANCE REMAINS IN
AGREEMENT THAT UPPER LEVEL RIDGING WILL BUILD OVER THE PACIFIC
NORTHWEST, RETURNING DRY WEATHER AND SUNNIER SKIES THROUGH THE
WEEKEND. ABOVE-AVERAGE 500 MB HEIGHTS ALSO OCCUR DURING THIS
TIME, SUGGESTING WARMER TEMPERATURES AND AFTERNOON HIGHS
REACHING THE MID TO UPPER 60S BY THE WEEKEND. THERE IS ALSO A
50-80% CHANCE FOR HIGH TEMPERATURES EXCEEDING 70 DEGREES SUNDAY
AND MONDAY ALONG THE I-5 CORRIDOR, WITH THE HIGHEST CHANCES
ACROSS THE WILLAMETTE VALLEY. WILL NOTE THAT THERE IS SOME
UNCERTAINTY MONDAY ONWARD AS HALF OF ENSEMBLE MEMBERS MAINTAIN
THE UPPER LEVEL RIDGE OVER OUR AREA AND DRY WEATHER, WHILE THE
OTHER HALF SHIFTS THE RIDGE EASTWARD AND RETURNS SLIGHTLY
COOLER TEMPERATURES AND SLIGHT CHANCES (15-25%) FOR
PRECIPITATION. -10
AVIATION
MOIST SOUTHWEST FLOW ALOFT HAS MAINTAINED OVERCAST
SKIES ACROSS THE AREA TUE EVENING, ALBEIT WITH CIGS REMAINING
VFR. EXPECT CIGS TO LOWER TO MVFR THRESHOLDS AROUND 08-10Z
WED AS A ROBUST PACIFIC FRONTAL SYSTEM BEGINS TO PUSH INLAND,
BRINGING WIDESPREAD RAIN WITH IT. PROBABILITIES FOR MVFR CIGS
INCREASE ACROSS THE AREA TO AROUND 50% BETWEEN 08-10Z WED, EXCEPT
60-80% AT THE COAST. LIGHT RAIN WILL MOST LIKELY BEGIN SPREADING
ACROSS THE AREA BY 08Z WED, WITH HEAVIER RAIN ARRIVING AT THE
COAST AFTER 12Z WED AND INLAND TERMINALS AFTER 15Z WED. SOUTH TO
SOUTHEASTERLY WINDS ARE EXPECTED TO INCREASE INTO WEDNESDAY
MORNING AS WELL, BECOMING GUSTY, ESPECIALLY ALONG THE COAST. NOTE
THERE IS ALSO A 10-20% CHANCE OF THUNDERSTORMS AT ALL TERMINALS
WEDNESDAY AFTERNOON AND EVENING. ANY THUNDERSTORMS THAT FORM WILL
HAVE THE POTENTIAL TO PRODUCE BRIEF PERIODS OF SMALL HAIL UNDER
THE SIZE OF PEAS, GUSTY AND ERRATIC OUTFLOW WIND GUSTS AS HIGH AS
35 KT AND A FEW FLASHES OF LIGHTNING. STRONGER SHOWERS WILL ALSO
BRING A RISK OF SMALL HAIL AND GUSTY OUTFLOW WINDS, ALBEIT WITHOUT
THE LIGHTNING RISK. PROBABILITIES FOR THUNDERSTORMS AT ANY GIVEN
TERMINAL ARE NOT HIGH ENOUGH TO WARRANT A PROB30 GROUP.
KPDX AND APPROACHES...A ROBUST PACIFIC FRONTAL SYSTEM WILL BEGIN
MOVING INLAND AROUND 08-10Z WED, BRINGING AROUND A 50% CHANCE FOR
MVFR CIGS. THIS SYSTEM WILL ALSO BRING STEADY RAIN TO THE AREA,
HEAVY AT TIMES AFTER 15Z WED. SOUTHEAST WINDS AROUND 8-12 KT
ARE EXPECTED TO INCREASE BY 18-21Z WED WITH GUSTS UP TO 25 KT.
HOWEVER, BRIEF OUTFLOW WIND GUSTS UP TO 35 KT WILL BE POSSIBLE
NEAR STRONGER SHOWERS OR THUNDERSTORMS WED AFTERNOON AND EVENING
(NOTE THIS IS WHEN THERE IS A 10-20% CHANCE OF THUNDERSTORMS).
STRONGER SHOWERS OR THUNDERSTORMS WILL ALSO BRING THE POTENTIAL
FOR SMALL HAIL, MOST LIKELY UNDER THE SIZE OF PEAS. -23
MARINE
SOUTHERLY WINDS INCREASE TONIGHT INTO WEDNESDAY MORNING
AS AN OCCLUDING COLD FRONT APPROACHES THE WATERS. HAVE ISSUED A
GALE WARNING FOR SOUTHERLY WINDS GUSTING UP TO 35-40 KT FROM 2 AM
TO 11 AM WEDNESDAY. EXPECT AN ABRUPT WESTERLY SHIFT IN WINDS
BEHIND THE FRONTAL PASSAGE LATE WED MORNING. WIND WAVES ARE
EXPECTED TO BUILD ON WEDNESDAY IN RESPONSE TO THE INCREASING
SOUTHERLIES, BECOMING STEEP AND CHOPPY, WITH SIGNIFICANT WAVE
HEIGHTS BUILDING TO AROUND 12 TO 14 FT, HIGHEST OVER THE SOUTHERN
WATERS. SEAS WILL LIKELY FALL BACK TO AROUND 9 TO 10 FT WED
AFTERNOON.
SURFACE LOW PRESSURE MOVES OVER THE NORTHERN WATERS LATE
WEDNESDAY, AS BREEZY WESTERLIES EASE OVERNIGHT INTO THU MORNING.
AN INCREASING WEST SWELL WILL ALSO PUSH INTO THE WATERS WED NIGHT
INTO THURSDAY, BUILDING SEAS TO AROUND 11 TO 13 FT WITH A PERIOD
OF 12 SECONDS. THIS WILL LIKELY MAINTAIN SMALL CRAFT TO MARGINALLY
HAZARDOUS SEAS CONDITIONS INTO THURSDAY EVENING. MARINE
CONDITIONS ARE EXPECTED TO EASE LATER IN THE WEEK AS HIGH
PRESSURE REBUILDS AND NORTHERLY WINDS RETURN TO THE COASTAL WATERS
BY THE WEEKEND. SEAS ARE EXPECTED TO SUBSIDE TO AROUND 5 TO 6 FT
LATER FRIDAY THROUGH THE WEEKEND. /DH
PQR WATCHES/WARNINGS/ADVISORIES
OR...WINTER WEATHER ADVISORY FROM 5 AM WEDNESDAY TO 5 PM PDT
THURSDAY FOR ORZ126.
WINTER STORM WARNING FROM 5 AM WEDNESDAY TO 5 PM PDT THURSDAY
FOR ORZ127-128.
WA...WINTER WEATHER ADVISORY FROM 5 AM WEDNESDAY TO 5 PM PDT
THURSDAY FOR WAZ211.
PZ...SMALL CRAFT ADVISORY FROM 2 AM TO 5 PM PDT WEDNESDAY FOR PZZ210.
GALE WARNING FROM 2 AM TO 11 AM PDT WEDNESDAY FOR PZZ251>253-
271>273.
WWW.WEATHER.GOV/PORTLAND
INTERACT WITH US VIA SOCIAL MEDIA:
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X.COM/NWSPORTLAND
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