020
FXUS66 KPQR 130722
AFDPQR

Area Forecast Discussion...UPDATED
National Weather Service Portland OR
1220 AM PDT Sat Sep 13 2026

Aviation Discussion Updated...

.SYNOPSIS...Expect cooler and unsettled conditions through the
weekend as an upper-level low pressure system progresses
overhead. Conditions then turn progressively warmer and drier
early next week as high pressure builds offshore. Increasing
easterly flow by Wednesday and Thursday could bring locally
breezy/gusty winds to the Gorge, Cascades and nearby foothills,
while also aiding the warmer and drier weather.

&&

.DISCUSSION...Now through Friday...This afternoon an upper-
level low pressure system continues to move towards the
coastline with rain and showers expected to further develop
headed into the evening hours. This precipitation likely
persists at times overnight into Sunday morning as the upper low
gradually shifts eastward. From this afternoon through Sunday
evening most locations from the coast into the Willamette Valley
should see around 0.10-0.30 inch of rainfall; measurable
amounts but not much more. However, there`s decent confidence
noticeably higher amounts fall across the southwest Washington
foothills/Cascades into the north Oregon Cascades where closer
to 0.50-1.25 inch of rain is anticipated. This is due to a
deformation band developing on the northern periphery of the
upper-level low helping to consolidate showers leading to
locally moderate sustained rainfall. There still remains a
slight bit of uncertainty among high-resolution models as to
exactly how far south this area of steadier precipitation could
wander. A slight southward nudge would increase rainfall totals
across the Portland Metro, particularly Sunday morning. As the
upper low moves well east of the Cascades by Sunday afternoon,
showers should become more scattered and increasingly focused
over higher terrain features. The inland valleys and immediate
coast likely trend mostly dry by the mid to late afternoon
hours, while the Cascades continue to see lingering showers into
the evening.

It`s worth quickly highlighting a ~15% chance of thunderstorms
was maintained in the forecast for this evening as cold air
moving in aloft may provide just enough instability for a stray
short-lived T-storm. Cold-core funnel clouds are also possible
with the stronger showers through Sunday. These are typically
short-lived and largely remain above the ground.

Come Monday and Tuesday the low pressure system ejects further
eastward with large scale troughing and northwesterly flow holding
in place across the Pacific Northwest thanks to a secondary
weak shortwave feature sliding down the BC coastline late
Monday. Temperatures will warm day to day compared to this
weekend, although only a couple degrees each afternoon. Expect
highs in the low to mid 70s by Tuesday afternoon - mid 60s along
the coast.

Then a more noticeable warm-up begins Wednesday into Thursday
as a ridge of high pressure which had been forming over the
eastern Pacific begins to shift eastward into the region. The
bulk of deterministic models and ensemble systems have now
converged on this solution. High temperatures to soar well into
the 80s across the interior lowlands as a result of this more
summer- like pattern. For Thursday afternoon specifically, the
latest NBM shows a 15-35% chance for highs to exceed 90s degrees
across the central/northern Willamette Valley, 0-10% elsewhere.
Easterly flow is also becoming more likely midweek. The
strongest winds currently appear on Wednesday into Thursday
morning, with gusts of 25-35 mph and isolated gusts near 40 mph
possible in more wind-prone areas of the Columbia River Gorge,
Cascades and adjacent foothills. The tops of the Coast Range
could also become breezy, although confidence here is lower.
Currently, there is around a 10-15% chance gusts could exceed 45
mph in the most exposed locations near/within the Columbia
River Gorge. The combination of warmer temperatures, lower
humidity and increasing east winds Wednesday and Thursday may
provide a window of elevated fire-weather concerns. -99/12

&&

.AVIATION...Through 06z Monday...A low pressure system near the
coast will move across the area tonight, pushing east of the
Cascades on Sunday. As of 04z Sunday, predominately VFR conditions
prevail across the airspace with periods of MVFR this evening at the
coast. Scattered rain showers will continue to spread across the
area with lowering CIGs likely. Best chance for MVFR conditions will
be after 06z on the coast and between 12-20z Sunday for inland
terminals. As showers end from west to east after 15-18z Sun,
conditions may begin to improve Sunday afternoon. South winds ease
overnight, then rise to 5-10 kt out of the southwest by Sunday
afternoon.

KPDX AND APPROACHES...VFR conditions favored through at least 12z
Sunday. Light rain showers possible into Sunday afternoon. Chances
for MVFR CIGs increase to around 40% between 14-20z Sunday. South
winds around 4-8 kt expected through the period. /DH

&&

.MARINE...A weak surface low centered off the central Oregon coast
as of early Saturday afternoon will traverse the waters this
afternoon before moving inland over the north Oregon coast by early
Sunday morning. Ahead of this system, southerly winds of 8-15 kt
will continue, with the strongest winds and gusts to 20 kt limited
to areas within 20 NM south of Cape Foulweather.
Numerous rain showers are also expected during this time, as well as
15-20% chances of isolated thunderstorms capable of producing gusty
and erratic winds and locally heavy downpours through this evening.
Onshore flow at 5-10 kt out of the west to southwest continues on
Sunday while rain shower coverage decreases through the day. A
persistent northwesterly swell at 8-9 seconds will maintain overall
seas around 5 ft through the weekend.

Surface high pressure rebuilds over the waters through the first
half of next week, with northerly flow returning late Monday.
Strengthening northerlies through midweek will see 50% or greater
chances of winds 20 kt or higher on Wednesday, especially beyond 10
NM south of Cape Falcon. Seas around 5 ft with a dominant
northwesterly swell at 8-9 seconds otherwise continue. -36

&&

.PQR WATCHES/WARNINGS/ADVISORIES...
OR...None.
WA...None.
PZ...None.
&&

$$

www.weather.gov/portland

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