035 
FXUS66 KPQR 161050
AFDPQR

Area Forecast Discussion
National Weather Service Portland OR
350 AM PDT Thu Oct 16 2025

.SYNOPSIS...Our ridge of high pressure begins to decay and shift
eastward today as dry weather likely holds in place through the
daytime hours across the interior valleys. This evening into 
Friday the pattern become more progressive starting with a weak 
frontal system ushering in chances for light rain showers and/or
drizzle, most likely near the coast. 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.

&&

.SHORT TERM...Now through Saturday night...Today the axis of a 
positively tilted ridge of high pressure shifts overhead
supporting the continuation of rather benign fall weather 
conditions through the daytime hours. The clear skies and light
winds approaching sunrise this morning have lead to cooler
temperatures for many outlying areas with a Frost Advisory in 
effect until 9am for spots like the Hood River Valley, Tualatin 
Valley, portions of SW Washington, and the southern Willamette 
Valley. 

Later today into tonight a strong jet stream to the north will 
work to flatten out the upper ridge while increasing onshore 
northwesterly flow brings increasing clouds to the area. A weak
front at the tail end of the system to the north will push 
onshore this evening into Friday morning bringing potential for 
some light rain showers and/or drizzle across the area. Thanks 
to the added cloud cover, overnight temperatures jump 4 to 8 
degrees compared to this(Thursday) morning. Should see clearing
skies Friday afternoon into the evening with dry conditions 
expected through Fri night. 

Seasonable temperatures with afternoon highs in the 60s persist
through at least the first half of the weekend as broad upper 
level ridging transitions over the region on Saturday. A more 
robust frontal system is expected to approach the region from
the northwest later Saturday. This system will bring increasing
chances for rain to the SW Washington and NW Oregon coast by the
late afternoon hours with rain likely spreading inland later 
Sat evening through Sat night. -99/02

.LONG TERM...Sunday through Wednesday night...An upper level 
trough is anticipated to move over the region on Sunday, though
there is still minor uncertainty as to the exact amplitude of 
this feature - at least there's slightly better agreement 
compared to the prior model runs this time yesterday. Still, 
this maintains a decent spread of potential rainfall 
accumulation amounts through Sunday night into Monday, though 
there is high confidence that higher amounts are more likely on 
the northern end of the forecast area than the southern ends. 
According to the latest NBM guidance, the lower end rainfall 
amounts range between ~0.3 inland to ~0.8 inch coast/Cascades (90%
chance of exceeding), while the higher end amounts show 
anywhere from ~1.3 inches inland to ~3.5 inches along the coast 
possible (10% chance). Showers likely break out behind the cold
front that pushes across the area on Sunday. Latest guidance 
shows around a 15-20% chance of thunder at the coast through the
I-5 corridor Sunday afternoon. Given the "skinny" CAPE profile 
and winds around 30-40 knots aloft expect locally gusty/erratic 
winds, heavy rain, small hail, and infrequent lightning in 
stronger convective activity. Speaking of winds, confidence is 
growing for a period of breezy conditions around and after the 
frontal boundary passage later Saturday night through Sunday 
with peak gusts generally around 23-30 mph inland; high degree 
of agreement among EPS ensemble members during this period. A 
few lingering showers possible into early next week as onshore 
flow persists, mainly near the coast. The most active weather 
likely remains to the north through Wednesday and Thursday. But,
long range models are indicating potential for this active 
weather to slide farther south, bringing a moderate risk of 
hazardous weather to western Washington and Oregon later next 
week. -99/02

&&

.AVIATION...A ridge of high pressure overhead begins to degrade
and shift eastward today as frontal system approaches this
afternoon into the evening. Expect VFR conditions through a 
majority of the TAF package except in the later half when the 
coastal sites see increased chances for persistent MVFR and even 
IFR CIGs, and precipitation. That said, we'll need to watch for 
patchy sunrise fog formation early this morning before 15-17z, 
particularly along the coast, and spots like KEUG/KHIO which are
more fog prone. Temperatures to start today will still be cold 
enough to form frost in some interior valleys though it will be 
less widespread than previous days. In general looking at mainly 
our cold spots within southwest Washington valleys and from KCVO 
southward. As the front moves in late in the forecast period 
(after 00-06z Fri) showery precipitation is expected first at KAST
before slowly progressing inland. Winds remain fairly light at all
sites, generally less than 5-10 knots. 

KPDX AND APPROACHES...VFR conditions likely prevail through the 
next 24-hrs. Still, guidance indicates an off chance (15-20%) for
a period of degraded conditions around 12-17z this morning in the
form of patchy fog/low clouds; something to keep an eye on. -99

&&

.MARINE...The influence of a ridge of high pressure overhead
begins to wane today although seas hold around 4-6 ft with a 
dominate northwesterly swell period of 14-15 seconds. Conditions 
become more active Friday and into the weekend as a large west to 
northwest swell enters the waters thanks to a frontal system
swinging into the region. Wave heights are expected to increase
to 8-12 feet Friday evening with a period of 16-18 seconds, 
leading to dangerous conditions for Small Craft. A Small Craft 
Advisory remains in effect for all waters and the Columbia River
Bar starting at 5 pm Friday. At least winds stay rather tame 
out of the north with gusts up to 10-17 kt into Saturday 
morning. Going forward the pattern remains rather active 
through the latter half of the weekend into early next week as 
comparatively stronger frontal system progresses through the 
coast waters. Conditions will quickly amplify as a result with a
60-80% chance of seas greater than 15 ft late Sunday into early
Monday and a 40-50% chance for seas to exceed 18 ft across the 
outer waters during the same time frame. Wave heights likely 
decrease later Monday into Tuesday morning bottoming out around 
7-9 ft at ~13 seconds before another potent northwesterly swell 
arrives Tuesday afternoon and evening pushing seas into the 
10-15 ft range again. -99/19

&&

.BEACH HAZARDS...A decent north to northwest swell of 10-12 ft at
16-18 seconds is expected to enter the waters Friday afternoon. 
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 continues across the Central and Northern Coast of 
Oregon and the South Washington Coast. 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! -99/19

&&

.PQR WATCHES/WARNINGS/ADVISORIES...
OR...Frost Advisory until 9 AM PDT this morning for ORZ104-109-
     116>118-121.
WA...Frost Advisory until 9 AM PDT this morning for WAZ205-208.
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

Interact with us via social media:
www.facebook.com/NWSPortland
x.com/NWSPortland