391
FXUS66 KPQR 201055
AFDPQR
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE PORTLAND OR
355 AM PDT TUE OCT 20 2026
SYNOPSIS
LARGELY DRY WEATHER EXPECTED THROUGH MIDWEEK. ABOVE
AVERAGE TEMPERATURES TODAY AND WEDNESDAY. CHANCES FOR WETTER
AND COOLER WEATHER RETURN LATE IN THE WEEK WITH POTENTIAL FOR A
MORE ROBUST SYSTEM OVER THE WEEKEND.
DISCUSSION...NOW THROUGH MONDAY
DRY CONDITIONS ARE EXPECTED
THROUGH AT LEAST THURSDAY. THE UPPER LEVEL LOW CONTINUES TO
PINCH OFF FROM THE MAIN FLOW AS IT DROPS SOUTH TOWARD CALIFORNIA
TODAY. IN ITS WAKE, SHORTWAVE RIDGING WILL BUILD INTO THE PACNW
TODAY. CLOUD COVER WILL DISSIPATE THROUGH THE DAY WITH LIGHT
OFFSHORE WINDS DEVELOPING ON THE EASTERN FLANKS OF THE CASCADES
AND COAST RANGE AND THROUGH THE WESTERN COLUMBIA RIVER GORGE.
THESE OFFSHORE WINDS ARE NOT EXPECTED TO BE IMPACTFUL THOUGH
THEY MAY BE LOCALLY GUSTY UP TO 40 MPH IN THE TYPICAL SPOTS
WITHIN THE GORGE. HIGHS JUMP TO AROUND10 DEGREES ABOVE NORMAL
TODAY AND WEDNESDAY, TRANSLATING TO AFTERNOON HIGHS IN THE 60S
ON THE COAST AND IN TERRAIN, AND IN THE LOW TO MID 70S WITHIN
INLAND VALLEYS.
THE LATTER HALF OF THE WEEK AGAIN TRENDS TOWARD COOLER
TEMPERATURES AND MODEST CHANCES FOR RAIN. CLUSTER ANALYSIS SHOWS
GOOD AGREEMENT IN TROUGHING DEVELOPING OVER THE GULF OF ALASKA
AND DROPPING SOUTHEAST TOWARD THE PACNW THURSDAY INTO FRIDAY.
THIS PATTERN WOULD FAVOR A RETURN TO NEAR NORMAL TEMPERATURES
AND CHANCES FOR LIGHT PRECIPITATION. CURRENTLY, THE BEST CHANCES
FOR PRECIPITATION ARE OVER THE CASCADE FOOTHILLS AND AREAS EAST
OF I-5 BUT REMAIN RATHER LOW AT 20-40%. RAINFALL ASSOCIATED
WITH THIS SYSTEM IS NOT EXPECTED TO BE NOTEWORTHY IF IT OCCURS
AT ALL. OVERNIGHT LOWS THURSDAY AND FRIDAY NIGHT ARE EXPECTED TO
BE MUCH COOLER THAN THE START OF THE WEEK. MORE WIDESPREAD
TEMPERATURES BELOW 37 DEGREES ARE POSSIBLE THROUGHOUT THE
CENTRAL AND SOUTHERN WILLAMETTE VALLEY, CASCADE FOOTHILL
VALLEYS, AND PARTS OF THE COAST RANGE VALLEYS. IF TRENDS
CONTINUES, WILL LIKELY NEED FROST ADVISORIES FOR SOME OR ALL OF
THESE LOCATIONS.
DETAILS HEADING INTO THE WEEKEND REMAIN MURKY AS ENSEMBLES
SOLUTIONS REMAIN UNDECIDED IN REGARDS TO THE DEVELOPING PATTERN.
THERE IS A LOW TO MODERATE CHANCE THAT A ROBUST SHORTWAVE
DEVELOPS OVER THE GULF OF ALASKA AND DROPS SOUTHWARD, SUPPORTING
A SURFACE LOW AS IT APPROACHES THE PACNW. AROUND 30-40% OF
ECMWF ENSEMBLE MEMBERS DEPICT BOTH OF THESE FEATURES HEADING
INTO SATURDAY AND SUNDAY. HOWEVER, THERE IS A NOTICEABLE TREND
IN SEVERAL OF THE MEMBERS TO KEEP THE CORE OF THE SURFACE LOW
OFFSHORE AND EVEN HAS IT RETROGRADING BACK OUT TO SEA DURING THE
LATTER HALF OF THE WEEKEND. THIS CURRENT TREND SIGNAL LOWER
POTENTIAL FOR MUCH NEEDED RAINFALL ACROSS THE AREA BUT ALSO
LOWER CHANCES FOR IMPACTFUL WINDS ACROSS THE REGION. GIVEN THIS
POTENTIAL SYSTEM IS STILL SEVERAL DAYS OUT, DETAILS REMAIN
UNCLEAR AND WILL HOPEFULLY BE FLESHED OUT IN THE COMING DAYS. -19
AVIATION...THROUGH 12Z WEDNESDAY
HIGH LEVEL CLOUDS CONTINUE
TO STREAM IN FROM THE SOUTH AS AN UPPER LEVEL LOW DRIFTS SOUTH.
THIS CLOUD COVER IS EXPECTED TO INHIBIT MOST, IF NOT ALL, FOG
DEVELOPMENT. OFFSHORE FLOW IS EXPECTED TO INCREASE AFTER 15-18Z
TODAY, BRINGING INCREASING EASTERLY WINDS TO KTTD AND PORTLAND
METRO TERMINALS AND INCREASING NORTHEAST WINDS TO KUAO. WINDS
WILL INCREASE OUT OF THE NORTH FROM KSLE TO KEUG. STRONGEST
WINDS WILL BE AT KTTD AND EAST INTO THE GORGE WITH GUSTS UP TO
25 KTS AT KTTD AND UP TO 30-35 KTS THROUGH THE WESTERN GORGE.
WINDS ALONG THE COAST TURN NORTHEASTERLY AROUND 5 KT WITH KONP
WINDS TURNING MORE NORTHERLY DURING THE AFTERNOON.
KPDX AND APPROACHES...VFR FLIGHTS CONDITIONS WILL CONTINUE THROUGH
THE TAF PERIOD WITH HIGH CLOUDS DISSIPATING THROUGH THE DAY.
NORTHWEST WINDS AROUND 5 KT INCREASING AND TURNING EASTERLY
AFTER 18Z AS AN OFFSHORE PRESSURE GRADIENT STRENGTHENS.
EXPECTING SUSTAINED WINDS AROUND 8-11 KT WITH OCCASIONAL GUSTS
AROUND 20KT. WINDS BEGIN DECREASING AFTER 00-02Z WED. -19/03
MARINE
NORTHERLY WINDS CONTINUE ACROSS THE WATERS IN THE
WAKE OF A SYSTEM THAT IS DROPPING SOUTHWARD. WIDESPREAD WIND
GUSTS UP TO 25 KT WILL BE POSSIBLE OVER THE OUTER WATERS BEYOND
10 NM OFFSHORE THROUGH THE AFTERNOON. A SMALL CRAFT ADVISORY
REMAINS IN EFFECT FOR THE OUTER WATERS THROUGH 5 PM. BEYOND 5
PM TOMORROW, WINDS AND SEAS WILL BE ON THE DECREASE AS HIGH
PRESSURE RETURNS.
WINDS AND SEAS ARE SET TO INCREASE AGAIN THURSDAY INTO FRIDAY
MORNING WITH THE PASSAGE OF A WEAK COLD FRONT, ESPECIALLY OVER
THE NORTHERN WATERS TO THE NORTH OF CAPE FALCON WHERE
CONDITIONS WILL LIKELY BE HAZARDOUS TO SMALL CRAFT. THERE IS THE
POTENTIAL FOR A STRONGER LOW PRESSURE SYSTEM OVER THE UPCOMING
WEEKEND, BRINGING A 20-40% CHANCE FOR GALE FORCE WIND GUSTS AND
SEAS OVER 10 FEET. OVERALL CONFIDENCE IN THE EXACT TRACK AND
STRENGTH OF THIS POTENTIAL LOW PRESSURE SYSTEM IS LOW AT THIS
TIME, AND THE FORECAST IS WORTH MONITORING OVER THE NEXT SEVERAL
DAYS. -19/23
PQR WATCHES/WARNINGS/ADVISORIES
OR...NONE.
WA...NONE.
PZ...SMALL CRAFT ADVISORY UNTIL 5 PM PDT THIS AFTERNOON FOR
PZZ271>273.
WWW.WEATHER.GOV/PORTLAND
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