283
FXUS66 KPQR 210410 AAA
AFDPQR
AREA FORECAST DISCUSSION...UPDATE
NATIONAL WEATHER SERVICE PORTLAND OR
910 PM PDT FRI MAR 20 2026
UPDATED AVIATION DISCUSSION...
SYNOPSIS
A SLOW-MOVING COLD FRONT WILL MOVE SOUTHEASTWARD ACROSS
SOUTHWEST WA AND NORTHWEST OR LATE FRIDAY AFTERNOON THROUGH FRIDAY
NIGHT, SPREADING LIGHT RAIN SOUTHWARD FROM THE COLUMBIA RIVER DOWN TO
LANE COUNTY. ISOLATED POST-FRONTAL SHOWERS EARLY SATURDAY MORNING
WILL DIMINISH QUICKLY AS SURFACE HIGH PRESSURE BUILDS INTO THE AREA,
BRINGING INCREASING SUN ON SATURDAY. THIS PATTERN WILL THEN HOLD
STEADY FOR A FEW DAYS, BRINGING COOLER AND DRIER CONDITIONS SATURDAY
AFTERNOON THROUGH MONDAY. A STRONGER PACIFIC COLD FRONT ARRIVES
SOMETIME BETWEEN MONDAY NIGHT AND TUESDAY EVENING, BRINGING
WIDESPREAD RAIN AND BREEZY WINDS TO THE AREA. SNOW LEVELS FALL BEHIND
THE FRONT LATE WEDNESDAY, HOWEVER THE BULK OF THE PRECIPITATION
ASSOCIATED WITH THIS SYSTEM SHOULD BE FINISHED BY THE TIME SNOW
LEVELS FALL BELOW THE CASCADE PASSES. MINIMAL SNOW ACCUMULATION AND
TRAVEL IMPACTS ARE EXPECTED AT THE PASSES.
SHORT TERM...NOW THROUGH MONDAY NIGHT
THERE HAS BEEN MINIMAL
CHANGE TO THE FORECAST. SATELLITE AND RADAR OBSERVATIONS FROM EARLY
FRIDAY AFTERNOON DEPICTED A SLOW-MOVING COLD FRONT DRAPED ACROSS
WESTERN WASHINGTON AND EXTENDING INTO THE COASTAL WATERS OFF THE
NORTH OREGON COAST, WITH A NARROW BAND OF LIGHT RAIN ALONG AND AHEAD
OF THE FRONT. THIS FRONTAL BOUNDARY WAS FINALLY BEGINNING TO SHOW
MORE NOTICEABLE MOVEMENT TOWARDS THE SOUTHEAST AS OF NOON-2 PM PDT
FRIDAY, WHICH SEEMS TO BE ON TRACK WITH THE LATEST SUITE OF HI-RES
MODEL GUIDANCE. THIS WILL ALLOW THE AFOREMENTIONED BAND OF RAIN TO
GRADUALLY PUSH SOUTHWARD ACROSS NORTHWEST OREGON FROM THE COLUMBIA
RIVER DOWN TO LANE COUNTY LATE FRIDAY AFTERNOON THROUGH FRIDAY NIGHT.
RAIN RATES AND AMOUNTS WILL BE MUCH TOO LIGHT FOR IMPACTS TO OCCUR,
WITH MOST LOCATIONS PICKING UP ANYWHERE FROM A TRACE TO 0.15 INCHES
OF RAIN.
RAIN IS EXPECTED TO END QUICKLY SATURDAY MORNING AS MODELS AND THEIR
ENSEMBLES REMAIN IN AGREEMENT FOR SURFACE HIGH PRESSURE AND ZONAL
FLOW ALOFT BEHIND THE FRONTAL PASSAGE FOR THE SATURDAY THROUGH MONDAY
TIME FRAME. THIS WILL BRING DRIER WEATHER AND RELATIVELY COOLER
TEMPERATURES WITH HIGHS CLOSE TO AVERAGE FOR THIS TIME OF YEAR
(MAINLY IN THE MID TO UPPER 50S). WINDS WILL ALSO BE LIGHT,
ESPECIALLY DURING THE OVERNIGHT HOURS EACH DAY. THE LIGHT WINDS WILL
BE IN CONJUNCTION WITH CLEARING SKIES SATURDAY AFTERNOON INTO
SATURDAY NIGHT, RESULTING IN AN IDEAL SET-UP FOR RADIATIONAL COOLING.
AS SUCH, FORECAST LOW TEMPERATURES REMAIN COLDEST SATURDAY NIGHT WITH
WIDESPREAD LOWS IN THE LOW TO MID 30S. WIDESPREAD FROST WILL LIKELY
DEVELOP AS A RESULT. SUNDAY NIGHT INTO MONDAY MORNING WILL BE CHILLY
ONCE AGAIN, THOUGH LOW TEMPERATURES WILL BE A FEW DEGREES WARMER IN
THE MID TO UPPER 30S WITH LESS WIDESPREAD FROST DEVELOPMENT. THOSE
WITH SENSITIVE OUTDOOR PLANTS SHOULD TAKE PRECAUTIONS TO PROTECT
VEGETATION FROM FROST THIS WEEKEND. NOTE THAT NWS PORTLAND WILL NOT
BEGIN ISSUING FROST ADVISORIES AND FREEZE WATCHES/WARNINGS FOR
AGRICULTURAL PURPOSES UNTIL APRIL 1ST WHEN THE GROWING SEASON BEGINS
TO RAMP UP MORE AND IMPACTS FROM FROST AND FREEZE CONDITIONS BECOME
MORE SIGNIFICANT. -23
LONG TERM...TUESDAY THROUGH THURSDAY NIGHT
CONFIDENCE REMAINS HIGH
FOR WIDESPREAD RAIN AND BREEZY WINDS TUESDAY INTO WEDNESDAY AS A
STRONGER PACIFIC COLD FRONT MOVES INLAND. MODEL ENSEMBLE GUIDANCE
CONTINUES TO SHOW UNCERTAINTY ON TIMING AND EXACT PRECIPITATION
AMOUNTS. HOWEVER, CONFIDENCE IS HIGH THAT RIVER FLOODING IS NOT
EXPECTED, EVEN IN THE WETTEST POSSIBLE SCENARIO. THIS FRONT COULD
ARRIVE AS EARLY AS EARLY MONDAY NIGHT OR AS LATE AS TUESDAY EVENING,
WITH THE MOST LIKELY ARRIVAL TIME BEING SOMETIME BETWEEN TUESDAY
AFTERNOON AND TUESDAY EVENING. AS A RESULT OF THESE TIMING
DIFFERENCES, THE NBM 10-90TH PERCENTILE FOR SNOW LEVELS CONTINUES TO
SHOW LARGE SPREAD ON TUESDAY, RANGING FROM 5000-10000 FT. LARGE MODEL
SPREAD IS EVIDENT FOR SURFACE TEMPERATURES AS WELL, WITH HIGHS
POTENTIALLY RANGING ANYWHERE FROM THE LOWER 50S TO UPPER 60S. THE
OUTCOME WILL BE DEPENDENT ON THE COLD FRONTAL TIMING; IF THE FRONT
HOLDS OFF UNTIL LATE IN THE DAY, SURFACE TEMPERATURES WILL BE WELL
INTO THE 60S WITH SNOW LEVELS WELL ABOVE PASS LEVEL. IF THE FRONT
ARRIVES MONDAY NIGHT OR TUESDAY MORNING, TEMPERATURES WILL BE IN THE
LOWER 50S WITH SNOW LEVELS APPROACHING PASS LEVEL. REGARDLESS OF THE
EXACT ARRIVAL TIME, CONFIDENCE IS HIGH THAT SNOW LEVELS WILL DROP
CONSIDERABLY BEHIND THE COLD FRONTAL PASSAGE, BOTTOMING OUT WEDNESDAY
NIGHT INTO THURSDAY MORNING WELL BELOW THE CASCADE PASSES. THAT BEING
SAID, ENSEMBLE GUIDANCE FOR QPF CLEARLY SHOWS PRECIPITATION BEGINNING
TO END BY THAT TIME, MEANING CONDITIONS WILL TREND COLDER AND DRIER
WITH LITTLE ACCUMULATING SNOW AND TRAVEL IMPACTS AT PASS LEVEL.
NBMV5.0 PROBABILITIES FOR 6 INCHES OF SNOW OR MORE IN A 48-HOUR
PERIOD ENDING AT 5AM PDT THURSDAY CONTINUE TO BACK THIS EXPECTATION
UP, AS CHANCES ARE ONLY AROUND 5% AT WILLAMETTE AND SANTIAM PASSES,
AND 15% ALONG HIGHWAY 26 NEAR GOVERNMENT CAMP. NOTE THAT LOWLAND SNOW
IS NOT EXPECTED GIVEN CONDITIONS WILL BE DRYING OUT BY THE TIME
TEMPERATURES BECOME COLDER.
BY THURSDAY AFTERNOON, THE WEATHER SYSTEM IS EXPECTED TO MOVE OUT OF
THE AREA WITH UPPER LEVEL FLOW BECOMING MORE ZONAL. EXPECTING DRY
CONDITIONS WITH CLEARING SKIES BY MIDDAY THURSDAY, WHICH COULD
ALLOW FOR TEMPERATURES TO WARM INTO THE UPPER 50S. -23/03
AVIATION
THE FRONT CONTINUES TO MOVE SOUTHWARD, SPREADING LIGHT
RAIN OVER THE CENTRAL/SOUTHERN WILLAMETTE VALLEY AND CENTRAL
OREGON COAST. SPECIFICALLY, RADAR IMAGERY CURRENTLY SHOWS THE
RAIN BAND STRETCHED FROM KONP TO KSLE.
EXPECT CHANCES OF MVFR CIGS AT INLAND TERMINALS AROUND 40-60%
THROUGH 12Z SAT (HIGHEST CHANCES KSLE SOUTHWARD), THEN VFR THROUGH
THE REST OF THE TAF PERIOD. AS FOR THE COAST, MVFR/VFR CONDS AT
KAST AND LIFR/IFR CONDITIONS AT KONP ARE EXPECTED TO END AT
DIFFERENT TIMES. WHILE KAST WILL LIKELY IMPROVE TO PREDOMINANTLY
VFR BY 10-12Z SAT, KONP WONT IMPROVE TO VFR CONDS UNTIL 19-21Z SAT
(30-50% CHANCE OF LIFR CONDITIONS BEFORE 19Z SAT AT KONP). EXPECT
NORTHERLY WINDS AT MOST TERMINALS THROUGH THE TAF PERIOD, WITH
THE EXCEPTION OF NORTHWESTERLY WINDS AT TERMINALS NEAR THE
COLUMBIA RIVER. WIND WILL REMAIN UNDER 10 KT FOR MOST TERMINALS,
WITH THE ONLY EXCEPTION OF GUSTS UP TO 20 KT AT KONP THROUGH
MAJORITY OF THE TAF PERIOD.
KPDX AND APPROACHES...THERE IS A 30-50% CHANCE FOR MVFR CIGS
BEFORE 12Z SAT, THEN VFR THROUGH THE REST OF THE TAF PERIOD.
NORTHWESTERLY WINDS UNDER 8 KT THROUGH THE TAF PERIOD.
~12
MARINE
HIGH PRESSURE WILL GRADUALLY BUILD TONIGHT, TURNING
WINDS MORE NORTHERLY OVER THE WATERS AND REMAINING UNDER 20 KT. A
BRIEF NORTHWESTERLY SWELL WILL MOVE IN TONIGHT, BRINGING MARGINAL
SMALL CRAFT SEAS OF 8-9 FT AT 10 SEC. THEREFORE, A SMALL CRAFT
ADVISORY HAS BEEN ISSUED FOR ALL WATERS FROM 11 PM FRIDAY TO 8 AM
SATURDAY. AN EXCEPTION IS THE COLUMBIA RIVER BAR, WHERE A SMALL
CRAFT ADVISORY IS IN EFFECT BETWEEN 5-10 AM SATURDAY FOR A VERY
STRONG EBB CURRENT THAT WILL BRING SEAS AROUND 9 FEET. OUTSIDE OF
THE PERIOD WITH THE VERY STRONG EBB, SEAS ALONG THE MAIN CHANNEL
OF THE BAR ARE SLIGHTLY LOWER (7-8 FT), SO THIS ZONE WAS EXCLUDED
FROM THE SMALL CRAFT ADVISORY THAT STARTS LATE FRIDAY EVENING.
BENIGN MARINE CONDITIONS CONTINUE THROUGH MONDAY AS HIGH PRESSURE
PERSISTS. SEAS FALL TO 5-7 FT AT 10 SEC BY LATE SATURDAY NIGHT,
BUT RE-BUILD TO 8-9 FT HEADING INTO MONDAY.
THE NEXT ROBUST WEATHER SYSTEM RETURNS TUESDAY INTO WEDNESDAY.
THIS SYSTEM WILL BRING A RETURN OF BREEZY SOUTHERLY WINDS ACROSS
ALL WATERS. CURRENT GUIDANCE SUGGESTS HIGH CONFIDENCE (60-80%
CHANCE) FOR WIDESPREAD AND FREQUENT SMALL CRAFT WIND GUSTS OF 21
KT OR GREATER, AND A 10-30% CHANCE FOR WIDESPREAD AND FREQUENT
GALE FORCE WIND GUSTS OF 34 KT OR GREATER ON TUESDAY. CHANCES FOR
ISOLATED GALE FORCE WIND GUSTS ARE AROUND 50-75%, WITH THE HIGHEST
CHANCES BEYOND 20 NM OFFSHORE. SEAS ON TUESDAY AND WEDNESDAY ARE
ALSO EXPECTED TO BUILD TO AROUND 14-16 FT IN RESPONSE TO
INCREASING WIND WAVES ALONG WITH AN INCREASING WESTERLY SWELL.
THERE'S A 30-60% CHANCE SEAS COULD EXCEED 15 FT WITH A 5-15%
CHANCE FOR SEAS EXCEEDING 20 FT. CHANCES INCREASE FROM SOUTH TO
NORTH, PEAKING ACROSS THE WATERS NORTH OF CAPE FALCON. -10
PQR WATCHES/WARNINGS/ADVISORIES
OR...NONE.
WA...NONE.
PZ...SMALL CRAFT ADVISORY FROM 5 AM TO 10 AM PDT SATURDAY FOR PZZ210.
SMALL CRAFT ADVISORY UNTIL 8 AM PDT SATURDAY FOR PZZ251>253-
271>273.
WWW.WEATHER.GOV/PORTLAND
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