286
FXUS66 KPQR 171044
AFDPQR
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE PORTLAND OR
344 AM PDT WED SEP 17 2025
SYNOPSIS
OFFSHORE FLOW THAT FUELED TUESDAYS WARMTH AND WINDS
HAS ENDED. A WEAK FRONT BRUSHING THE COAST EARLY THIS MORNING
WILL RETURN ONSHORE FLOW, BUT WITH LITTLE MOISTURE TO WORK WITH,
ONLY LIGHT PRECIPITATION CHANCES EXIST ALONG THE COAST. A
LARGER TROUGH DIGGING SOUTHEAST FROM THE GULF OF ALASKA THIS
WEEKEND WILL BRING A MORE NOTICEABLE COOL-DOWN AND HIGHER RAIN
CHANCES, ESPECIALLY FOR THE COAST AND SOUTHWEST WASHINGTON.
SHORT TERM...NOW THROUGH THURSDAY NIGHT
AFTER TUESDAYS RECORD-SETTING HEAT, CONDITIONS HAVE SHIFTED BACK
TOWARD SEASONAL AVERAGES AS ONSHORE FLOW REDEVELOPS. A WEAK
FRONTAL BOUNDARY MOVING INLAND EARLY THIS MORNING MAY SQUEEZE
OUT A FEW LIGHT SHOWERS ALONG THE COAST, BUT PROBABILITIES
REMAIN LOW AT JUST 10-20%. OTHERWISE, EXPECT COOLER AND DRIER
WEATHER THROUGH AT LEAST THURSDAY. TEMPERATURES WILL BE MORE
TYPICAL FOR MID-SEPTEMBER: HIGHS IN THE UPPER 60S TO LOW 70S AT
THE COAST AND UPPER 70S TO LOW 80S INLAND TODAY. MINIMUM
RELATIVE HUMIDITY VALUES WILL ALSO BE HIGHER THAN RECENT DAYS,
AROUND 40-50% THIS AFTERNOON. THURSDAY CONTINUES THE TREND OF
MODEST COOLING, WITH COASTAL HIGHS IN THE LOW TO MID 60S AND
INLAND HIGHS IN THE MID TO UPPER 70S. LITTLE TO NO FOG
DEVELOPMENT IS ANTICIPATED THROUGH THURSDAY NIGHT.
LONG TERM...FRIDAY THROUGH TUESDAY
FRIDAY WILL BRING A BRIEF BUMP IN TEMPERATURES UNDER A NARROW
RIDGE, WITH HIGHS CLIMBING INTO THE UPPER 70S TO LOW 80S INLAND
AND UPPER 60S TO LOW 70S ALONG THE COAST. BY SATURDAY, ENSEMBLE
GUIDANCE REMAINS CONSISTENT IN BRINGING A BROAD TROUGH
SOUTHEASTWARD FROM THE GULF OF ALASKA, WHICH WILL GRADUALLY
INCREASE PRECIPITATION CHANCES ACROSS THE REGION.
FOR SATURDAY INTO SUNDAY, PROBABILITIES FOR MEASURABLE RAIN WILL
RANGE FROM 20-40% FOR MOST OF NORTHWEST OREGON, WITH LOWER
CHANCES (AS LOW AS 10%) IN THE SOUTHERN WILLAMETTE VALLEY AND
INTO THE LANE/LINN COUNTY CASCADES AND FOOTHILLS. HIGHER CHANCES
OF 50-80% ARE EXPECTED NORTH AND WEST OF A LINE FROM THE WILLAPA
HILLS DOWN TO TILLAMOOK, INCLUDING THE SOUTHWEST WASHINGTON
COAST AND AROUND ASTORIA. TEMPERATURES OVER THE WEEKEND WILL
TREND COOLER, GENERALLY IN THE 70S INLAND AND LOW TO MID 60S
ALONG THE COAST.
LOOKING INTO EARLY NEXT WEEK, HIGHS REMAIN SEASONABLE IN THE
MID TO UPPER 70S INLAND, WITH CONTINUED COOL CONDITIONS ALONG
THE COAST. TUESDAY INTO WEDNESDAY, A LOW PRESSURE SYSTEM OFF THE
COAST OF NORTHERN CALIFORNIA RIDES UP A TROUGH OVER THE
NORTHEAST PACIFIC AND INTO OREGON. GUIDANCE CURRENTLY SUGGESTS
WIDESPREAD 20-30% PROBABILITIES FOR PRECIPITATION, THOUGH
DETAILS SUCH AS TIMING REMAINS UNCERTAIN.
~HALL
AVIATION
SOUTHWEST FLOW ALOFT AS UPPER RIDGE OF HIGH PRESSURE
SHIFTS EAST OF THE CASCADES TODAY. VFR WITH MOSTLY CLEAR SKIES
EXPECTED INLAND ACROSS THE WILLAMETTE VALLEY THROUGH THIS EVENING.
ALONG THE COAST, MARINE STRATUS WILL MAINTAIN IFR TO LOW MVFR CIGS
THROUGH THIS MORNING. LIGHT RAIN OR DRIZZLE IS POSSIBLE LATER THIS
MORNING AS THE MARINE LAYER DEEPENS. LOW STRATUS LOOKS TO BREAK
OUT MVFR, AND POTENTIALLY VFR BRIEFLY, AFTER 18-20Z WED. NORTH TO
NORTHWEST WINDS INCREASE THIS AFTERNOON, WITH GUSTS UP TO 25 KT
ALONG THE COAST.
KPDX AND APPROACHES...VFR UNDER MOSTLY CLEAR SKIES EXPECTED
THROUGH THE PERIOD. LIGHT AND VARIABLE WINDS THIS MORNING BECOME
NORTHWEST BY THE AFTERNOON, WITH GUSTS TO AROUND 20 KT AFTER 00Z
THU. /DH
MARINE
LIGHT SOUTHERLY WINDS CONTINUE THIS MORNING AHEAD OF A
DECAYING FRONT. BY THIS AFTERNOON, WINDS TURN NORTHERLY AS HIGH
PRESSURE RETURNS OVER THE COASTAL WATERS. GUSTS UP TO 25-30 KT ARE
LIKELY TONIGHT THROUGH THURSDAY EVENING. SEAS ARE ALSO EXPECTED TO
BUILD TO AROUND 8 TO 10 FT WITH A PERIOD OF AROUND 10-11 SECONDS
DURING THIS TIME. THEREFORE, HAVE EXTENDED THE SMALL CRAFT
ADVISORY ACROSS ALL COASTAL WATERS THROUGH THU EVENING.
NORTHERLY WINDS EASE ON FRIDAY AS HIGH PRESSURE SHIFTS SOUTH,
WEAKENING ACROSS THE COASTAL WATERS. A FRONTAL SYSTEM WILL LIKELY
APPROACH FROM THE NORTH LATER THIS WEEKEND, THOUGH NO SUBSTANTIAL
IMPACTS EXPECTED. /DH
PQR WATCHES/WARNINGS/ADVISORIES
OR...NONE.
WA...NONE.
PZ...SMALL CRAFT ADVISORY FROM 3 PM THIS AFTERNOON TO 5 AM PDT
THURSDAY FOR PZZ210.
SMALL CRAFT ADVISORY FROM 3 PM THIS AFTERNOON TO 11 PM PDT
THURSDAY FOR PZZ251>253-271>273.
WWW.WEATHER.GOV/PORTLAND
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