667
FXUS66 KPQR 180503
AFDPQR
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE PORTLAND OR
1003 PM PDT TUE MAR 17 2026
UPDATED AVIATION, MARINE, AND HAZARDS SECTIONS.
SYNOPSIS
THROUGH THE REMAINDER OF THE WORK WEEK THE REGION
REMAINS ON THE NORTHERN PERIPHERY OF AN UPPER-LEVEL RIDGE OF
HIGH PRESSURE FACILITATING MUCH WARMER THAN NORMAL CONDITIONS.
HOWEVER, AN ATMOSPHERIC RIVER AIMED AT NORTHERN WASHINGTON AND
VANCOUVER ISLAND WILL OCCASIONALLY WOBBLE SOUTHWARD FROM TIME TO
TIME GIVING PORTIONS OF THE REGION CHANCES FOR RAIN, ESPECIALLY
IN PACIFIC/WAHKIAKUM COUNTY AND ALONG THE NORTH OREGON COAST.
THEN OVER THE WEEKEND WE'LL TREND COOLER AS A TROUGH SWINGS
INTO THE PACIFIC NORTHWEST ALTHOUGH FORECAST CONFIDENCE
DEGRADES FROM THIS POINT ONWARD DUE TO INCREASING MODEL
UNCERTAINTY.
SHORT TERM...NOW THROUGH FRIDAY
THIS AFTERNOON CURRENT RADAR
AND SATELLITE DATA SHOWS LIGHT RAINFALL ATTEMPTING TO PUSH
INLAND BUT SURFACE OBSERVATIONS SHOW LITTLE ACCUMULATION SO FAR
AWAY FROM THE COASTLINE. THANKS TO A VERY DRY AIRMASS ALOFT
HIGHLIGHTED ON THE MORNING KSLE SOUNDING, IT'S LIKELY MOST OF
THE PRECIPITATION AROUND THE I-5 CORRIDOR IS FALLING AS VIRGA
AS IT GETS EATEN AWAY/EVAPORATED BY THE MUCH DRIER AIRMASS
ABOVE THE SURFACE. IN SHARP CONTRAST, PORTIONS OF FAR WESTERN
PACIFIC COUNTY HAVE CLOCKED UPWARD OF 2 INCHES OF RAINFALL OVER
THE LAST 12 HRS. MOVING THROUGH THE NEXT SEVERAL DAYS THE LARGE
SCALE PATTERN OF AN UPPER-LEVEL RIDGE TO OUR SOUTH-SOUTHEAST AND
TROUGHING OVER THE NORTH HALF OF BRITISH COLUMBIA WILL HOLD IN
PLACE WITH FAIRLY SIMILAR CONDITIONS DAY TO DAY. WHILE THE
UPPER-LEVEL RIDGE ALMOST CERTAINLY FACILITATES "WARM"
CONDITIONS OVER THE AREA, OUR FOCUS REMAINS ON THE AN
ATMOSPHERIC RIVER (AR) TAKING AIM AT THE WESTERN OLYMPIC
PENINSULA AND VANCOUVER ISLAND. THE PUSH AND PULL OF BOTH THE
AFOREMENTIONED TROUGH AND RIDGE FEATURE WILL HELP TO MODULATE
THE PLACEMENT OF THE AR. OVERALL, RAIN WILL BE MOST PERSISTENT
OVER PACIFIC COUNTY AND THE FAR NORTH OREGON COAST; THESE AREAS
HAVE ADDITIONAL RAIN TOTALS RANGING BETWEEN 0.60-3.50 INCHES
BETWEEN 5 PM TODAY THROUGH 5PM FRIDAY - HIGHEST TOTALS NORTH
PACIFIC COUNTY.
OTHERWISE CONDITIONS REMAIN DRY MOST HOURS INLAND THROUGH
FRIDAY, PARTICULARLY SOUTH OF THE PORTLAND/VANCOUVER METRO
AREA. GIVEN THE BROAD SOUTHWESTERLY FLOW ALOFT AND 850MB
TEMPERATURES ABOVE THE SURFACE AT 10-13C (ANOMALOUSLY WARM FOR
THIS TIME OF YEAR) PORTLAND SOUTHWARD, HIGH TEMPERATURES RESPOND
IN-KIND LIKELY RISING INTO THE THE MID TO UPPER 60S ACROSS THE
LOWLANDS. CAN'T RULE OUT LOWER TO MID 70S AROUND LANE COUNTY AS
WELL. THE PRIMARY PIECE OF UNCERTAINLY IN REGARDS TO
TEMPERATURES WILL BE THE AMOUNT OF MID TO HIGH CLOUD COVER FROM
THE SYSTEM TO OUR NORTH, IF SKIES ARE CLEARER THAN FORECAST
PARTICULARLY THURSDAY AFTERNOON, THE NORTH WILLAMETTE VALLEY AND
PORTLAND METRO HAVE A BETTER SHOT AT MEETING/EXCEEDING 70
DEGREES - A 30-40% CHANCE ACCORDING TO THE LATEST NBM. IT'S ALSO
WORTH QUICKLY NOTING THE DRY AIRMASS ALOFT WILL BE STICKING
WITH US ALOFT LEADING TO POOR DAYTIME AND NIGHTTIME RELATIVE
HUMIDITY VALUES FOR THE HIGHER PEAKS IN THE CASCADE FOOTHILLS
AND CENTRAL OREGON COAST RANGE. -99
LONG TERM...FRIDAY NIGHT THROUGH TUESDAY
THIS WEEKEND THE
LARGE SCALE PATTERN FINALLY SHOWS SIGNS OF PROGRESSING ALTHOUGH
IT REMAINS TO BE SEEN HOW EXACTLY THIS WILL PLAY OUT IN THE
FORECAST AS DETERMINISTIC AND ENSEMBLE MODEL UNCERTAINTY BEGINS
TO GROW. THE CURRENT CONSENSUS IS FOR AN UPPER-LEVEL SHORTWAVE
AND ACCOMPANYING COLD FRONT TO KICK WESTWARD INTO THE PACIFIC
NORTHWEST FRIDAY NIGHT AND/OR SATURDAY LEADING TO INCREASING
PRECIPITATION CHANCES ACROSS THE INLAND VALLEYS. HOWEVER, MODELS
DO SHOW A SPREAD IN THE POTENTIAL AMPLITUDE AND STRENGTH WITH
THIS SYSTEM AND GIVEN THE DRY AIRMASS IN PLACE NEAR THE CASCADES
WOULD TEND HEDGE TOWARDS THE LOWER-END RAINFALL SOLUTION.
UNCERTAINTY GROWS FURTHER EARLY NEXT WEEK AS ENSEMBLES STRUGGLE
RESOLVING THE LARGE SCALE PATTERN ALOFT. BY LATE MONDAY INTO
TUESDAY, AROUND 50% OF THE ENSEMBLE SPACE SHOWS A TROUGH SITTING
JUST OF THE COASTLINE WITH CLOSER TO NORMAL TEMPERATURES
REMAINING IN PLACE AND BETTER RAINFALL CHANCES. ANOTHER 30% OF
ENSEMBLES HAVE THE RIDGE TO OUR EAST A BIT MORE OVERHEAD WHICH
WOULD KEEPS THE INLAND AREAS DRIER AND WARMER, AND THEN THE
REMAINING 20% PUT THE RIDGE OF HIGH PRESSURE DIRECTLY OVERHEAD
LEADING TO MUCH DRIER AND WARMER CONDITIONS THAN CURRENTLY FORECAST.
IN ANY CASE THE MAJORITY OF ENSEMBLE MEMBERS HINT AT ANOTHER
TROUGH ARRIVING AROUND THE MIDDLE OF NEXT WEEK. -99
AVIATION
UPPER LEVEL RIDGING TO THE SOUTH AND AN ATMOSPHERIC
RIVER TO THE NORTH CONTINUE TO INFLUENCE THE REGION. THE ATMOSPHERIC
RIVER MOISTURE IS SUPPORTING MID AND HIGH LEVEL CLOUDS AREAWIDE
ALONG WITH LOW LEVEL CLOUD COVER ALONG THE COAST. CONDITIONS ALONG
THE COAST ARE MVFR/IFR AND ARE EXPECTED TO MAINTAIN SUB-VFR
CONDITIONS THROUGH THE MAJORITY OF THE TAF PERIOD, THOUGH CONDITIONS
COULD BRIEFLY LIFT TO VFR BETWEEN 20Z WED THROUGH 03Z THU. INLAND
LOCATIONS SHOULD EXPECT VFR CONDITIONS, THOUGH THERE IS A 20-40%
CHANCE OF MVFR CIGS BETWEEN 10-18Z WED. LIGHT WINDS GENERALLY
SOUTHERLY LESS THAN 10 KTS.
WINDS INCREASE ALONG THE COAST AFTER 12-15Z WED NORTH OF KTMK AND
AFTER 15-18Z SOUTH OF KTMK TO AROUND 10-15 KTS WITH OCCASIONAL GUSTS
UP TO 20 KTS. ON AND OFF SHOWERS EXPECTED OVERNIGHT AT KAST AND
NORTH, BECOMING MORE STEADY LIGHT RAIN AFTER 18-20Z WED.
KPDX AND APPROACHES...MAINLY VFR CONDITIONS EXPECTED WITH MID LEVEL
CLOUDS PERSISTING. THERE IS A 20-40% CHANCE OF MVFR CIGS BETWEEN 10-
18Z WEDNESDAY. LIGHT SOUTHERLY WINDS LESS THAN 10 KTS THROUGH THE
TAF PERIOD. -03/19
MARINE
SOUTHERLY WINDS ACROSS ALL WATERS EXPECTED THROUGH THE
MIDDLE OF THE WEEK. INCREASED WIND GUSTS WILL BE POSSIBLE THROUGH
THE EVENING AS A COLD FRONT SAGS SOUTHWARD TOWARD THE NORTHERN
OREGON AND SOUTHERN WASHINGTON COASTS. OCCASIONAL WIND GUSTS UP TO
25 KT WILL BE POSSIBLE FOR ZONES NORTH OF CAPE FOULWEATHER,
INCLUDING THE COLUMBIA RIVER BAR, ON WEDNESDAY. SEAS OF 8 AND 11
FEET AT 10 TO 13 SECONDS AS WINDS INCREASE AND A SOUTHWESTERLY TO
WESTERLY SWELL MOVES INTO THE WATERS. CHANCES FOR SMALL CRAFT
CONDITIONS REMAIN LOW FOR THE WEAK SYSTEM THAT MOVES THROUGH ON
THURSDAY. -19/42
PQR WATCHES/WARNINGS/ADVISORIES
OR...NONE.
WA...NONE.
PZ...NONE.
WWW.WEATHER.GOV/PORTLAND
INTERACT WITH US VIA SOCIAL MEDIA:
WWW.FACEBOOK.COM/NWSPORTLAND
X.COM/NWSPORTLAND
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