021
FXUS66 KPQR 010549 AAA
AFDPQR

Area Forecast Discussion...UPDATED
National Weather Service Portland OR
1049 PM PDT Sat Oct 31 2026

Updated Aviation Discussion...

.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 06Z Monday...Currently mostly VFR across the
airspace with northward-moving mid to high level clouds gradually
breaking and shifting east of the Cascades due to high pressure
aloft. With skies gradually clearing through 9-13Z Sun, expect
increasing chances for fog development. KAST and KUAO have already
begun to experience deteriorated conditions, currently with MVFR
to IFR visibility. After 9-13Z Sun, expect fog to develop at most
inland terminals, with the least confidence for fog at KTTD.
Probabilistic guidance currently suggests a 20-50% chance of LIFR
conditions between 09-20Z Sun, with the highest chances, earliest
occurrence, and longest duration at terminals within the southern
Willamette Valley. Specifically, most terminals will improve back
to VFR by 18-19Z Sun, while KSLE and KEUG may remain under
deteriorated conditions until 20-21Z Sun. Winds will remain
generally light and variable through the TAF period, further
favoring fog development overnight. Light easterly wind at coastal
terminals will likely limit conditions to VFR, with only a 15-25%
chance of MVFR conditions between 10-18Z Sun.

KPDX AND APPROACHES...Currently VFR conditions with mid to high
level clouds gradually clearing towards 13Z Sun. Clearing skies
will bring favorable conditions for fog development, prompting
probabilistic guidance to suggest a 20-30% chance of LIFR VIS
anytime between 12-18Z Sun. VFR conditions will return by 18-19Z
Sun. Generally light and variable winds through the TAF period.
~12

&&

.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...Dense Fog Advisory from 1 AM to 10 AM PDT Sunday for ORZ108-109-
     111-112-114>118.

WA...Dense Fog Advisory from 1 AM to 10 AM PDT Sunday for WAZ204>207.

PZ...None.

&&

$$

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