459 
FXUS66 KPQR 162221
AFDPQR

Area Forecast Discussion
National Weather Service Portland OR
321 PM PDT Thu Oct 16 2025

.SYNOPSIS...This evening into Friday, the weather pattern 
becomes more progressive. A weak frontal system will produce 
chances for light rain showers and/or drizzle, most likely near 
the coast and in SW Washington. High confidence remains in a 
widespread rain event slated for for late Saturday into Sunday 
thanks to the arrival of an upper- level trough followed by 
unsettled post- frontal conditions. The weather trends drier by 
late Monday into Tuesday morning, although some uncertainty 
remains with a 20-45% chance of rain returning by mid-week.

&&

.DISCUSSION...Thursday Afternoon through Wednesday...Visible
satellite imagery Thursday afternoon shows upper level clouds
beginning to stream into NW Oregon and SW Washington as high
pressure begins to break down over the region and a weak
approaches. The cloud cover will continue overnight into
tomorrow morning, which will keep overnight temperatures warmer
than the previous number of nights. Expect widespread low 
temperatures in the 40s except for mid to upper 30s in the
higher elevations. The weak front is expected to move through
the area late tonight through tomorrow morning, bringing a
localized chance of rain showers to the northern Oregon and
southern Washington coast and adjacent terrain. The front is
expected to continue to weaken as it makes landfall, with most
inland areas south of the Portland metro area not expected to
receive any rain and only a 15-25% chance of light showers
elsewhere inland. 

Transient ridging builds again tomorrow afternoon into early 
Saturday, with skies clearing by tomorrow evening. This could
lead to chilly temperatures once again for inland valleys 
Friday night into Saturday morning. Will have to monitor for
the potential of another frost advisory, especially for the
Upper Hood River Valley, northern Oregon Coast Range lowlands,
and portions of the southern Willamette Valley as low
temperatures could fall into the mid 30s to low 40s.

Ensemble guidance is in good agreement that the next weather
system will slide northwest into the region late Saturday into
Sunday, though some inconsistencies continue with the depth and
timing of the upper trough, leading to uncertainties in timing
of precipitation onset and amount of precipitation. Latest
guidance narrows down the timing of widespread precipitation to
begin along the coast sometime in the late hours Saturday night
or early Sunday, then moving inland not long after. The bigger
uncertainty is still in rain amounts, though overall model
guidance remains consistent that locations south of Highway 20
will receive less rain than locations north. NBM's low-end 
forecast (90% chance of exceeding) is around 0.1-0.5 inch for 
inland valleys and 0.2-0.8 inches along the coast and terrain, 
whereas the high end forecast (10% chance of exceeding) is 
around 1.1-1.6 inches for inland valleys and 1.25-2.75 inches 
for the coast and terrain through 5am Monday. The deterministic
forecast is around 0.25-0.6 inches for inland valleys, 0.35-1.1
inches for the coast and Coast Range, and 0.5-2 inches for the
Cascades. The other concern is a 15-25% chance of post-frontal 
thunderstorms on Sunday midday through the evening, mainly for 
locations west of the Cascades. Model soundings indicate some 
instability behind the front as well as a 30-40 kt low level
jet, which could produce gusty winds, heavy rain, small hail,
and some lightning with stronger showers/thunderstorms.
Additionally, some breezy winds could mix down from the low
level jet. NBM has a 40-60% chance of wind gusts greater than 30
mph along the coast north of Lincoln City and a 40-60% chance of
gusts greater than 25 mph for inland areas north of Eugene
Saturday night into Sunday. These winds would not cause
significant impacts, but they could still cause minor concerns
such as causing dying leaves to fall off of trees and clog
drains and gutters.

For Monday, some showers could linger over the terrain in the 
morning, but otherwise dry weather should return as LREF
clusters indicate some level of ridging returns. For Tuesday and
Wednesday, the LREF ensemble clusters show uncertainties in the
general weather pattern. There's about a 15-20% chance of
showers returning Tuesday and/or Wednesday, increasing to 20-40%
by late Wednesday, with temperatures remaining fairly mild. 
However, the period of more concern to keep an eye on is October
24-27 where CPC has indicated a moderate risk for the PacNW of 
heavy precipitation, strong winds, and Cascade snow. This is out
of the main 7-day forecast period, but we will provide updates 
as this moves into the period. -03

&&

.AVIATION...High pressure will maintain VFR conditions with high 
clouds this afternoon. A weak frontal system approaches the 
region this evening, returning low-end VFR CIGs to Willamette 
Valley terminals after 06z Fri. Meanwhile, there is high 
confidence (>80% chance) that MVFR CIGs and showers return to the 
north Oregon coast (KAST) after 06-09z Fri. MVFR CIGs spread 
southward into the central Oregon coast (KONP) around 12-14z Fri 
as the front progresses southeastward. High confidence (60-80%) 
for MVFR CIGs as well across northern Valley terminals after 
15-18z Fri. Lower confidence (20-40%) tomorrow morning for MVFR 
CIGs south of KUAO toward KEUG. Minimal showers expected for the 
Willamette Valley as this front is very weak. Variable winds across
the region around 5 kt or less through tonight.

KPDX AND APPROACHES...VFR CIGs through the TAF period, with CIGs
lowering after 10-12z Fri with the frontal passage. 70-90% chance
for MVFR CIGs between 2-3 kft after 15z Fri. Variable winds under
5 kt.    -10

&&

.MARINE...A weak front will briefly shift winds southwesterly 
across the waters tonight and remain around 10 kt or less. Winds 
return to a northerly direction behind the front Friday morning 
around 10-15 kt as high pressure re-builds. Seas hold around 4-6 
ft at 14-15 seconds. Conditions become more active on Friday as a
northwesterly swell enters the waters due to a low pressure 
system over the Gulf of Alaska. This swell will build seas to 
11-13 ft at 15-16 seconds, resulting in hazardous conditions for 
small craft. Small Craft Advisories go into effect across all 
waters including the Columbia River Bar 5 PM Friday and last 
through at least Saturday evening. At least winds stay rather tame
out of the north with gusts up to 10-15 kt into Saturday morning.

Going forward, the pattern remains rather 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 (>80% 
chance) on Sunday. There is also a 15-20% chance that seas reach 
20 ft or higher across the outer waters (beyond 10 NM) on Sunday 
as well. Seas likely decrease later Monday into Tuesday morning 
bottoming out around 8-10 ft at 13 seconds before another potent 
northwesterly swell arrives Tuesday afternoon and evening pushing 
seas into the 10-15 ft range again.      -10/99

&&

.BEACH HAZARDS...A northwest swell of 10-12 ft at 16-17 seconds 
is expected to enter the waters Friday evening. This increase in 
wave energy will support a high threat for sneaker waves through 
much of Saturday, possibly longer into Saturday night or Sunday as
a moderate threat. A Beach Hazards Statement remains in effect 
across the Central and Northern Coast of Oregon and the South 
Washington Coast through Saturday afternoon. 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. Remember, never turn your back on
the ocean! -10/99

&&

.PQR WATCHES/WARNINGS/ADVISORIES...
OR...None.
WA...None.
PZ...Small Craft Advisory from 5 PM Friday to 2 PM PDT Saturday for 
     PZZ210.
     Small Craft Advisory from 5 PM Friday to 8 PM PDT Saturday for 
     PZZ251>253-271>273.
&&

$$

www.weather.gov/portland

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