265
FXUS66 KPQR 161759 AAA
AFDPQR

Area Forecast Discussion...UPDATED
National Weather Service Portland OR
1058 AM PDT Thu Oct 16 2025

...Updated aviation discussion...

.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...High pressure will maintain VFR conditions with high
clouds today. 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%) for MVFR CIGs south of KUAO toward KEUG.
Minimal showers expected for the Willamette Valley as this front
is very weak. Variable winds today across the region around 5 kt
or less.

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...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...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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