Timberline Lodge

000
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.

&&

$$

www.weather.gov/portland

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