297 
FXUS66 KPQR 180406 AAA
AFDPQR

Area Forecast Discussion...UPDATED
National Weather Service Portland OR
905 PM PDT Fri Oct 17 2025

...Updated aviation discussion...

.SYNOPSIS...Transient shortwave ridging tonight will bring 
chilly overnight temperatures and areas of frost for some inland
valleys. A robust frontal system arrives late Saturday into 
Sunday, bringing widespread soaking rain to the area with gusty 
southerly winds. Trending drier Sunday night into early next 
week, however some uncertainty remains with a 20-45% chance of 
rain returning by Wednesday. A stronger weather system is 
possible late next week, though uncertainty is high in details 
this far out.

&&

.SHORT TERM...Friday Afternoon through Sunday 
Night...There has been very little change to the forecast.
Visible satellite imagery early Friday afternoon shows a band of
low clouds with drizzle over northern Oregon slowly dissipating
as the front that moved into the region this morning continues 
moving southeast. Transient ridging will build into the area
behind this front this afternoon into early Saturday, setting 
the stage for clear skies and calm winds tonight. This will 
lead to chilly temperatures once again for inland valleys 
tonight into Saturday morning. The coldest areas will likely be 
the Upper Hood River Valley, south WA Cascade foothills, Battle 
Ground and Ridgefield areas. Confidence is generally over 70-80%
these zones will see low temperatures dip to 33-36 degrees, 
and Frost Advisories remain in effect tonight into Saturday 
morning. Meanwhile, a Freeze Warning remains in effect for the 
Upper Hood River Valley for low temperatures as cold as 29-30 
degrees. While patchy frost is also possible in portions of the
southern Willamette Valley, especially east of I-5, confidence 
remains too low to include these zones in the Frost Advisory. 
This is due to potential low clouds or fog that may develop 
instead of frost; the latest HREF and REFS runs indicate a 
chance for low cloud development late Friday night or early
Saturday morning, which would favor temperatures bottoming out 
in the upper 30s with minimal frost concerns. The overall 
weather pattern beyond Friday morning does not favor widespread 
frost or freeze concerns, so this round of frost/freeze 
headlines may wind up being the last of this growing season.

Despite the chilly temperatures in place Saturday morning,
temperatures will rebound nicely in the afternoon with highs in the
60s, except near 70 degrees in Eugene-Springfield, Creswell, Blue
River, Lowell and Oakridge. These areas will see sunny skies
throughout the day, however northern areas will see clouds begin to
increase ahead of the next frontal system. Models are in good
agreement on the timing of this front, bringing stratiform rain to
southwest Washington and the north Oregon coast Saturday evening and
then the rest of northwest Oregon from Lane County northward Saturday
night into Sunday morning. Persistent stratiform rain will transition
to post-frontal showers by late Sunday morning or early Sunday
afternoon. This is when forecast soundings show 850 mb temperatures
cooling to +1 to +2 degrees Celsius, with SBCAPE values increasing
to 100-200 J/kg and equilibrium levels generally below -10 degrees
Celsius. However, 0-3 km AGL bulk shear values are fairly high at
30-35 kt (have opted to use 0-3 km AGL bulk shear values instead of
0-6 km as cloud tops generally look to stay near or below 3 km). Both
speed shear and directional shear are in place, as the wind direction
will veer with height for a few hours or so as the upper level trough
axis moves overhead. The limited instability and shallow nature of
Sunday's convection suggests overall lightning activity will most
likely be limited (which helps explain why NBM thunder probabilities
only peak around 10-20%). However, whether lightning occurs or 
not, stronger showers will have the potential to produce a 
funnel cloud, landspout, or gusty outflow winds up to 45 mph 
given the environmental wind profile in place, meaning highly 
localized wind damage is possible. Note southerly winds will be 
breezy in general Saturday night and Sunday, even away from 
showers and thunderstorms. Currently expecting southerly wind 
gusts up to 20-30 mph for inland areas and up to 30-40 mph for 
the south WA/north OR coast. Gusts up to 40-50 mph appear likely
in the high Cascades. Winds will weaken Sunday night while any 
lingering showers begin to dissipate. -23/03

&&

.LONG TERM...Monday through next Friday...Most model guidance
suggests dry weather with seasonable temperatures, relatively light
winds and a mix of clouds and sun Monday and Tuesday. That said,
there remains a handful of GEFS/ENS ensemble members with light QPF
amounts Monday morning/afternoon and Tuesday morning/afternoon as a
pair of weak upper level impulses move overhead. As such, there is a
10-30% chance of light rain showers on Monday for the south
WA/north OR coast and 15-35% chance on Tuesday everywhere, with
highest chances in southwest WA and along the south
WA/north OR coast.

Chances for rain gradually increase late Wednesday through Thursday
night, peaking near 75-90% by early Friday morning, as another
potentially stronger weather system approaches the area. This 
system has the potential to bring more impactful rain amounts 
and gusty south winds, however uncertainty is high in regards to
exact rain amounts and exact wind speeds, as the outcome will 
be highly dependent on the exact track and strength of a 
negatively tilted trough and associated deepening surface low 
that will be moving somewhere over the coastal waters during 
that time. Ensemble low locations vary significantly both 
spatially and temporally, with some ensemble guidance suggesting
a fairly weak low with minimal impacts, while other members 
suggest a very strong low capable of wind damage somewhere along
the Washington, Oregon, or northern California coast. There is 
currently a 15-25% chance for max wind gusts of 45 mph or 
stronger across all of northwest Oregon and southwest 
Washington, except for a 35-50% chance at the coast and on 
exposed ridges in the Coast Range and Cascades. This system will
also bring a 50-75% chance of 1" of rain or more in the
Willamette Valley and a 40-60% chance of 3" of rain or more
along the coast and terrain for Thursday and Friday, with 
additional rain chances continuing into the weekend. -23/03

&&

.AVIATION...Satellite imagery and terminals observations as of
Friday evening depicts VFR conditions with scattered cloud cover as 
high pressure briefly re-builds over the area. VFR conditions with 
FEW/SCT clouds persist through tonight. With some clearing tonight, 
can't rule out some fog development across the Willamette Valley. 
Guidance suggests a 30-45% chance for LIFR VIS/CIGs after 10-12z 
Sat, with the highest chances in the central and southern Willamette 
Valley. Fog development will depend on how much existing cloud cover 
there is and if the ground saturates. Any fog or low stratus that 
develops tonight should lift by 17-19z Sat as daytime heating 
progresses. Expect variable winds under 5 kt tonight. 

High clouds filter into the area after 18z Sat as the next frontal 
system approaches. Rain returns to the north Oregon coast by 18-21z 
Sat, gradually moving into the Willamette Valley by 03-06z Sun. 
Winds turn more southerly to southwesterly with this system.

KPDX AND APPROACHES...VFR conditions with a 15-25% chance for 
LIFR/IFR VIS and a 40-50% chance for LIFR/IFR CIGs from 11-17z Sat. 
Variable winds under 5 kt overnight, turning more southeasterly 
Saturday afternoon with the next approaching frontal system.   -10

&&

.MARINE...High pressure will maintain northerly winds around 10-15
kt tonight. Seas build overnight to 10-12 ft at 15-16 seconds as 
a northwesterly swell arrives from a dying low pressure system 
over the Gulf of Alaska. This will be hazardous to small craft, 
so Small Craft Advisories are in effect across all waters 
including the Columbia River Bar through at least Saturday.

The weather pattern remains active Saturday night into early next
week as a stronger frontal system progresses through the waters 
and brings breezy southerly to westerly winds. Marine conditions 
quickly amplify as a higher northwesterly swell enters the waters,
building seas above 15 ft at 15 seconds (>90% chance) on Sunday.
Chances for seas above 20 ft have decreased and are less than 10%,
indicating increasing confidence is the wave height forecast. In 
addition to increasing seas, winds will likely gust up to 25-30 
kt. Brief and isolated gale forced wind gusts up to 35 kt are 
possible over the northern and central inner waters (Cape
Shoalwater to Cape Foulweather) including the Columbia River Bar 
during the frontal passage Saturday night into early Sunday 
morning.

Seas will decrease later Monday into Tuesday morning, bottoming 
out around 7-9 ft at 12-13 seconds before another potent 
northwesterly swell arrives Tuesday afternoon and evening pushing 
seas into the 10-15 ft range again. Active weather continues later
in the week.        -10/23

&&

.BEACH HAZARDS...A northwest swell of 10-12 ft at 15-16 seconds 
seconds is expected to enter the waters Friday evening. This 
increase in wave energy will support a high threat for sneaker 
waves through this weekend. A Beach Hazards Statement remains in 
effect across the central and north Oregon coast and the south 
Washington coast through Sunday evening. Sneaker waves can run up
significantly farther on a beach than normal, including over 
rocks, logs, and jetties. Sneaker waves can suddenly knock people 
off of their feet and quickly pull them into the ocean which may 
lead to serious injury or drowning. Caution should be used when in
or near the water. Always keep an eye on the waves, and be 
especially watchful of children and pets. Remember, never turn 
your back on the ocean!      -10/23

&&

.PQR WATCHES/WARNINGS/ADVISORIES...

OR...Frost Advisory from midnight tonight to 9 AM PDT Saturday for 
     ORZ104.

     Freeze Warning from midnight tonight to 9 AM PDT Saturday for 
     ORZ121.

WA...Frost Advisory from midnight tonight to 9 AM PDT Saturday for 
     WAZ205-208.

PZ...Small Craft Advisory until 5 AM PDT Sunday for PZZ210-251-252-
     271-272.

     Small Craft Advisory until 8 PM PDT Saturday for PZZ253-273.
&&

$$

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