159
FXUS66 KPQR 182132
AFDPQR
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE PORTLAND OR
232 PM PDT WED MAR 18 2026
SYNOPSIS
THE REGION REMAINS ON THE NORTHERN PERIPHERY OF AN UPPER
LEVEL RIDGE THROUGH FRIDAY, BRINGING MUCH WARMER THAN NORMAL
TEMPERATURES TO MOST OF NORTHWEST OREGON. MEANWHILE, A WEAKENING
ATMOSPHERIC RIVER AIMED AT WESTERN WASHINGTON AND VANCOUVER ISLAND
WILL OCCASIONALLY WOBBLE SOUTHWARD FROM TIME TO TIME, BRINGING
OCCASIONAL LIGHT RAIN DOWN TO THE NORTH OREGON COAST AT TIMES WITH
MORE PERSISTENT RAIN OVER PACIFIC, WAHKIAKUM, AND NORTHERN
COWLITZ/SKAMANIA COUNTIES. TRENDING COOLER SATURDAY THROUGH MONDAY
WITH MAINLY DRY CONDITIONS ASIDE FROM ISOLATED LIGHT SHOWERS, MAINLY
IN THE MOUNTAINS. WIDESPREAD RAIN DEVELOPS ON TUESDAY WITH BREEZY
SOUTH TO SOUTHWEST WINDS. PRECIPITATION IN THE CASCADES ON TUESDAY
WILL FALL AS EITHER RAIN, SNOW, OR A RAIN/SNOW MIX DEPENDING ON SNOW
LEVELS (WHICH COULD RANGE ANYWHERE FROM 2000 TO 9000 FEET PER MODEL
SPREAD).
SHORT TERM...NOW THROUGH FRIDAY NIGHT
THERE HAS BEEN MINIMAL
CHANGE TO THE SHORT TERM FORECAST WITH TODAY'S UPDATE AS THE WEATHER
PATTERN IN PLACE REMAINS PERSISTENT. THE TWO SIGNIFICANT SYNOPTIC
SCALE FEATURES AT PLAY ARE A BROAD UPPER LEVEL RIDGE CENTERED OVER
THE U.S. DESERT SOUTHWEST AND A BROAD TROUGH OVER THE GULF OF ALASKA,
MAINTAINING PERSISTENT WEST TO SOUTHWEST FLOW ALOFT OVER THE PACIFIC
NORTHWEST. BETWEEN THESE TWO FEATURES IS A WEAKENING ATMOSPHERIC
RIVER EMBEDDED WITHIN THE PERSISTENT SOUTHWESTERLY FLOW.
AS OF 2 PM PDT WEDNESDAY, RADAR AND SATELLITE OBSERVATIONS DEPICTED A
NARROW BAND OF LIGHT STRATIFORM RAIN AROUND 50-100 MILES WIDE WITHIN
THE AXIS OF GREATEST MOISTURE TRANSPORT. THIS BAND OF RAIN WAS MAINLY
IMPACTING PACIFIC COUNTY, WAHKIAKUM COUNTY, AND NORTHERN PORTIONS OF
COWLITZ AND SKAMANIA COUNTIES. HI-RES MODEL GUIDANCE SUGGESTS THIS
BAND OF RAIN WILL OCCASIONALLY SHIFT TO THE SOUTH AND NORTH,
IMPACTING THE FAR NORTH OREGON COAST AT TIMES THROUGH THURSDAY NIGHT.
AS SUCH, THESE AREAS WILL REMAIN CLOUDY AND COOLER WHILE THE REST OF
NORTHWEST OREGON REMAINS PARTLY TO MOSTLY SUNNY WITH WARMER HIGH
TEMPERATURES IN THE UPPER 60S TO MID 70S, EXCEPT MID 50S TO MID 60S
ALONG THE COAST. THE WARMEST TEMPERATURES ARE EXPECTED OVER THE
CENTRAL AND SOUTHERN WILLAMETTE VALLEY AND THE CASCADE FOOTHILLS;
NOTE RECENT SURFACE WEATHER OBSERVATIONS SHOW RELATIVE HUMIDITIES
FALLING INTO THE 20-40% RANGE OR LOWER IN THESE AREAS DURING PEAK
DAYTIME HEATING. THIS MEANS HUMIDITY LEVELS ARE LOW AND THE AIRMASS
REMAINS QUITE DRY TO THE SOUTH OF THE AFOREMENTIONED BAND OF RAIN.
THE NBMV5.0 WAS UTILIZED TO HELP LOWER THE RELATIVE HUMIDITY FORECAST
IN THESE AREAS.
COME FRIDAY, CONDITIONS SHOULD BECOME MORE MOIST WITH RELATIVELY
COOLER TEMPERATURES AS THE BAND OF RAIN FOCUSED OVER SOUTHWEST
WASHINGTON FINALLY SHIFTS SOUTHWARD AS A COLD FRONT ACROSS NORTHWEST
OREGON, ALBEIT DECAYING AT THE SAME TIME. THIS WILL RESULT IN
INCREASING CLOUDS ON FRIDAY WITH HIGH TEMPERATURES GENERALLY IN THE
MID 50S TO MID 60S, COOLEST NORTH OF SALEM AND WARMEST SOUTH OF
SALEM. THERE IS ALSO A 50-80% CHANCE OF LIGHT RAIN SHOWERS ON FRIDAY
AS THE COLD FRONT MOVES THROUGH, WITH THE HIGHEST PROBABILITIES IN
THE MOUNTAINS LATE IN THE DAY. RAIN AMOUNTS ARE EXPECTED TO BE LIGHT
AND INSIGNIFICANT WITH NO NOTABLE IMPACTS TO DISCUSS. IN FACT, SOME
LOCATIONS WILL LIKELY ONLY SEE TRACE AMOUNTS OF RAIN, ESPECIALLY OVER
THE CENTRAL AND SOUTHERN WILLAMETTE VALLEY. SHOWERS SHOULD BEGIN TO
DECREASE IN COVERAGE FRIDAY NIGHT. -23
LONG TERM...SATURDAY THROUGH WEDNESDAY
THE LONG TERM FORECAST
REMAINS HIGHLIGHTED BY A RELATIVELY COOLER WEATHER PATTERN WITH
SEASONABLE TEMPERATURES AND MAINLY DRY CONDITIONS, EXCEPT TUESDAY AND
WEDNESDAY WHEN WETTER CONDITIONS ARRIVE. FOR THE SATURDAY THROUGH
MONDAY TIME FRAME, MODELS AND THEIR ENSEMBLES ARE IN GOOD AGREEMENT
FOR NEARLY ZONAL FLOW ALOFT WITH SURFACE HIGH PRESSURE IN PLACE OVER
SOUTHWEST WASHINGTON AND WESTERN OREGON. THIS WILL RESULT IN MAINLY
DRY CONDITIONS DURING THAT TIME, HOWEVER THERE MAY BE ISOLATED
POST-FRONTAL RAIN SHOWERS LINGERING ON SATURDAY, MAINLY OVER THE
MOUNTAINS EARLY IN THE DAY (30-60% CHANCE).
ATTENTION THEN TURNS TO THE TUESDAY TO WEDNESDAY TIME FRAME. THIS IS
WHEN ENSEMBLE GUIDANCE DEPICTS THE ARRIVAL OF A STRONGER PACIFIC COLD
FRONT, BRINGING WETTER CONDITIONS WITH WIDESPREAD RAIN. NBM
PROBABILITIES FOR PRECIPITATION PICK UP ON THIS WELL AND PEAK BETWEEN
80-90% BY TUESDAY EVENING/NIGHT. ALTHOUGH CONFIDENCE IS HIGH
PRECIPITATION WILL RETURN, CONFIDENCE IS NOT AS HIGH REGARDING EXACT
PRECIPITATION AMOUNTS AS MODEL SPREAD FOR QPF IS LARGE. THE NBM 10TH
PERCENTILE FOR 48-HOUR QPF AMOUNTS FROM 5AM TUESDAY TO 5AM THURSDAY
RANGES FROM AROUND 0.10-0.50 INCHES, WHILE THE NBM 90TH PERCENTILE
RANGES FROM 1.00-3.50 INCHES (HIGHEST AMOUNTS AT THE COAST AND ACROSS
THE WESTERN SLOPES OF THE COAST RANGE AND CASCADES). REGARDLESS OF
THE EXACT OUTCOME, IT APPEARS FLOODING WILL NOT BE A CONCERN. ANOTHER
ASPECT OF THE FORECAST ON TUESDAY AND WEDNESDAY THAT HAS HIGH
UNCERTAINTY IS SNOW LEVELS. THE NBM 10-90TH PERCENTILE FOR SNOW
LEVELS DURING THAT TIME RANGES FROM 2000-9000 FEET, RESPECTIVELY. THE
MOST LIKELY OUTCOME IS AROUND 5500-8000 FEET, HIGHEST OVER THE LANE
AND LINN COUNTY CASCADES AND LOWEST OVER THE SOUTH WASHINGTON
CASCADES. AS SUCH, IS NOT CLEAR YET WHETHER OR NOT THE CASCADES WILL
SEE RAIN, A RAIN/SNOW MIX, OR ACCUMULATING SNOW. IT IS ALSO NOT CLEAR
YET IF THE CASCADE PASSES WILL BE IMPACTED WITH ACCUMULATING SNOW.
PROBABILITIES FOR 6 INCHES OF SNOW OR MORE IN A 48-HOUR PERIOD ENDING
AT 5AM THURSDAY ARE QUITE LOW AS PASS LEVEL (10-15%). THIS SEEMS
REASONABLE AS ONLY THE COLDEST ENSEMBLE GUIDANCE SUGGESTS SNOW LEVELS
WILL FALL LOW ENOUGH FOR IMPACTFUL SNOW AMOUNTS AT PASS LEVEL. ALSO
WORTH NOTING IS BREEZY SOUTH TO SOUTHWEST WINDS WITH THE FRONTAL
PASSAGE ON TUESDAY, ALBEIT LIKELY STAYING BELOW 35 MPH WITH MINIMAL
IMPACTS. -23
AVIATION
RADAR IMAGERY AS OF EARLY WEDNESDAY AFTERNOON DEPICTS
LIGHT RAIN ALONG THE NORTH OREGON AND SOUTH WASHINGTON COAST AS AN
ATMOSPHERIC RIVER IS SQUEEZED BETWEEN AN UPPER LEVEL RIDGE TO THE
SOUTH AND A BROAD UPPER LEVEL TROUGH OVER THE GULF OF ALASKA.
LIGHT RAIN IS EXPECTED TO CONTINUE THROUGH THIS EVENING AT KAST,
BEFORE TRANSITIONING TO SHOWERS THURSDAY MORNING. HIGH PRESSURE
WILL ALSO KEEP MARINE STRATUS ALONG THE COAST AND MAINTAIN A MIX
OF IFR/MVFR CIGS. OCCASIONAL DROPS TO 5-6 SM EXPECTED AROUND AST
DURING PERIODS OF HEAVIER RAIN OR MIST. MEANWHILE, WILLAMETTE
VALLEY TERMINALS REMAIN VFR WITH HIGH CLOUDS THROUGHOUT THE TAF
PERIOD AS THESE LOCATIONS STAY UNDER THE INFLUENCE OF THE UPPER
LEVEL RIDGE. WINDS GENERALLY SOUTHERLY TO SOUTHWESTERLY AND UNDER
10 KT, EXCEPT FOR OCCASIONAL GUSTS UP TO 20 KT ALONG THE NORTH
OREGON COAST THROUGH 03Z THU.
KPDX AND APPROACHES...PREDOMINATELY VFR CONDITIONS WITH HIGH
CLOUDS THROUGH THE TAF PERIOD. SOUTHERLY TO SOUTHEASTERLY WINDS
UNDER 10 KT. -10
MARINE
LOW PRESSURE OFFSHORE WILL MAINTAIN BREEZY SOUTHERLY
WINDS THROUGH THURSDAY, MAINLY FOR THE WATERS NORTH OF CAPE
FALCON INCLUDING THE COLUMBIA RIVER BAR. A SMALL CRAFT ADVISORY
HAS BEEN ISSUED FOR THESE AREAS THROUGH 5 PM THURSDAY FOR
SOUTHERLY WINDS 15-20 KT WITH GUSTS UP TO 25 KT. WINDS REMAIN
WEAKER SOUTH OF CAPE FALCON. SWELLS ARE FORECAST OUT OF THE
SOUTHWEST AND NORTHWEST, WITH COMBINED WAVE HEIGHTS AROUND 7-9 FT
AT 10-11 SEC THROUGH FRIDAY. HIGH PRESSURE BUILDS THIS WEEKEND,
TURNING WINDS MORE NORTHERLY AND REMAINING UNDER 20 KT. SEAS THEN
GRADUALLY FALL TO 5-7 FT AT 10-11 SEC. BENIGN MARINE CONDITIONS
CONTINUE THROUGH MONDAY BEFORE ANOTHER SYSTEM RETURNS TUESDAY-
WEDNESDAY. GUIDANCE SUGGESTS A 50-60% CHANCE FOR WIDESPREAD, SMALL
CRAFT WIND GUSTS OF 21 KT OR GREATER ON TUESDAY. -10
PQR WATCHES/WARNINGS/ADVISORIES
OR...NONE.
WA...NONE.
PZ...NONE.
WWW.WEATHER.GOV/PORTLAND
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