955
FXUS66 KPQR 312043
AFDPQR

Area Forecast Discussion
National Weather Service Portland OR
143 PM PDT Sat Oct 31 2026

.SYNOPSIS...Mostly clear skies and calm winds may bring frost
and/or fog development across much of NW OR and SW WA in the
mornings through Monday. Mostly dry conditions through Monday.
Low chances for scattered showers Monday night, then
precipitation chances increase later next week with limited
weather impacts expected.

&&

.DISCUSSION...Through Friday...Visible satellite imagery early
Saturday afternoon shows areas of fog/stratus across some
inland valleys with mostly clear skies elsewhere. Afternoon
temperatures are expected to warm into the mid- 50s, before
quickly falling into the 40s after sunset this evening. The
upper trough that has been spinning just offshore all week
became elongated offshore overnight and is slowly pushing inland
today through tonight. This will bring a 20-40% chance of
showers to mainly the Lane and Linn County Cascades and
foothills this afternoon and evening, decreasing around
midnight. Valley locations should remain dry with just some high
clouds overhead.

Dry conditions continue Sunday into Monday as an upper level
ridge of high pressure builds over the PacNW behind the trough
passage. Skies are expected to clear after midnight tonight,
which combined with calm winds is expected to lead to another
round of widespread fog or low stratus across inland valleys
Sunday morning. Radiational cooling is also expected under these
conditions, which will allow minimum temperatures outside of
urban areas to cool into the mid to upper 30s. Fog/low stratus
should dissipate by midday with sunny skies and high
temperatures in the 50s. Expect a rinse and repeat of this
forecast on Monday.

Today`s 12z ensemble guidance has come into much better
agreement on the overall weather pattern through midweek next
week, though some uncertainty on specifics still exist. Guidance
indicates a low pressure system will develop in the eastern
Pacific early next week as the high pressure moves inland over
the PacNW. The majority of ensemble members indicate this low
will move inland somewhere in northern CA or along the CA/OR
border late Monday through Tuesday. Currently the forecast has a
10-25% chance of scattered showers Monday night into early
Tuesday with very limited rain amounts, though depending on the
strength and north to south extent of this low, these chances
could decrease in subsequent forecasts. Tuesday through most of
Wednesday look to dry out with temperatures warming to near 60
degrees for the interior lowlands. Then precipitation chances
increase again late Wednesday into Friday as ensemble members
indicate another front or two could bring a couple more rounds
of moisture to the area. At this point, no significant
precipitation impacts are expected with any of these weather
systems, though there`s a 25-50% chance of wind gusts increasing
over 30 mph along the coast (5-20% chance inland) with each
frontal passage late in the week. -03

&&

.AVIATION...Through 00Z Sunday...Satellite imagery and terminal
observations as of early Saturday afternoon depicts predominately
VFR conditions for most terminals except for the central and
southern Willamette Valley, where there is a mix of MVFR/IFR/LIFR
CIGs. The further south in the Valley you go, the lower the CIGs.
Satellite imagery shows stratus slowly dissipating across the
valley, so expect remaining stratus to persist through about
21-23z Sat.

Tonight, will see another around of LIFR conditions due to fog
and low stratus across Valley terminals as high pressure builds
aloft and brings increasing cloud breaks. Guidance suggests a
30-60% chance for VIS < 1/2SM across the Valley at any given hour
between 12-17z Sun. However, typical foggy spots such as KHIO and
KEUG could see fog as early as 06-07z Sun based on what we saw
last night. Fog/stratus development is favored across the rest of
the Valley by 11-13z Sun. Light north/northwest winds around 5 kt
or less across the Valley this afternoon, becoming calm
overnight. Light easterly winds continue at the coast which will
support VFR conditions at KAST/KONP through the TAF period.

KPDX AND APPROACHES...IFR CIGs through 19-20z Sat, improving to
VFR afterwards with high clouds. Tomorrow morning, there is a
20-40% chance for LIFR VIS due to fog at any given hour between
12-17z Sun. Northwesterly winds around 5 kt or less today,
becoming variable overnight.      -10

&&

.MARINE...Weak low pressure offshore gradually dissipates today as
winds decrease below 10 kt. Seas around 4 to 5 ft continue to
subside to 3 to 4 ft into Sunday morning. Offshore winds develop
late Sunday night and persist into early next week. A long period
west-northwest swell also arrives Sunday evening, building seas
to around 7 to 9 ft at 16-19 seconds on Monday. Chances for seas
over 10 ft on Monday remain at around 30-50% across the outer
waters. This long period swell will result in a moderate threat
for sneaker waves at the coast Sunday evening through Tuesday.
Caution should be used at beaches when in or near the water.

A weak low pressure system approaches the waters mid next week,
returning light southerly winds. By the end of the week, model
guidance hints at a stronger system entering the waters, resulting
in a 60-80% chance for maximum wind gusts exceeding 21 kt on
Friday with a 30-50% chance for seas exceeding 15 ft.     -10/DH

&&

.PQR WATCHES/WARNINGS/ADVISORIES...

OR...None.
WA...None.
PZ...None.

&&

$$

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