North Plains, Oregon Weather Forecast Discussion

496
FXUS66 KPQR 271745
AFDPQR
Area Forecast Discussion
National Weather Service Portland OR
1045 AM PDT Sat Sep 27 2025
Updated Aviation discussion...
&&
.SYNOPSIS...Conditions will be dry and mild through Sunday,
with the warmest temperatures expected today as high pressure
remains over the region. The first in a series of Pacific
frontal system will bring widespread rain to the area Sunday
night into Monday. Conditions remain cool and showery through at
least the middle of next week as additional frontal systems
move into the region. The strongest system currently is expected
Tuesday through Wednesday and will bring breezy south winds,
however uncertainty remains high for exact wind speeds, timing
and associated impacts.
&&
.DISCUSSION...Now through Friday...High clouds will increase
from the west through this morning as a weak upper level
impulse moves overhead. Even with the could filtered sunshine,
still expecting high temperatures in the upper 70s to low 80s
for the interior lowlands, with highs in the 60s at the coast.
Sunday should be a few degrees cooler due to more substantial cloud
cover and slightly cooler temperatures aloft. This increase in cloud
cover will be in response to a slow-moving Pacific cold front
originating from a low sitting within the NE Pacific Ocean. Due
to the slow motion of this front, Sunday will likely stay dry.
However, stratiform rain will eventually spread over the area
Sunday night into Monday, most likely beginning at the coast
overnight when PoPs increase to 80-90%, and for inland areas
Monday morning when PoPs also increase to 80-90%. Stratiform
rain will transition to a more showers pattern late Sunday/
early Monday within the post-frontal environment.
Another weather system arrives late Tuesday into Wednesday.
This system will likely be stronger than the Sunday night/Monday
system, at least in regards to wind speeds and rain amounts.
That said, uncertainty is high for exact wind speeds, as the
outcome will be highly dependent on the exact strength and track
of the aforementioned low pressure system over the northeast
Pacific. A small subset of ensemble guidance suggests this low
will move towards the coast while remaining strong, resulting in
gusty south winds up to 50 mph for the coast and possibly even
for inland areas. However, the probability for wind gusts of 45
mph or stronger is low (less than 5% for inland areas, 15-30%
for coastal areas). While this is far from being the most likely
outcome, it is worth mentioning as wind speeds of this magnitude
would be enough to result in tree damage and some power outages,
especially when considering the fact that leaves are still on
trees. Precipitation totals from the Sunday/Monday system range
from 0.50"-0.90" along the coast and 0.20"-0.50" inland. For the
Tuesday/Wednesday system precipitation totals range from
0.75"-1.50" and 0.50"-1.00" inland. For the Tuesday/Wednesday
system it should be noted that there are higher precipitation
totals along the Coast Range and the Cascades. For the end of
the week system, precipitation totals range from 0.15"-0.40"
along the coast and 0.10"-0.40" inland.
Overall, fall looks to be knocking on the Pac NW door as this
coming week looks to be very active. Expect cool and wet
conditions along with some breezy conditions through the
upcoming week. -42/TK
&&
.AVIATION...High pressure is receding ahead of a weak frontal
system approaching from the Northeast Pacific. VFR conditions will
continue through this afternoon, before low marine stratus at
around 500 ft will bring IFR/LIFR cigs and IFR vis to coastal
terminals by 00-03z Sun. Inland, there are low to moderate
chances, around 30%, of MVFR or lower cigs developing after 12z
Sun if marine stratus can push far enough east. Light north to
northwest winds this afternoon will turn out of the south this
evening and overnight ahead of the approaching front. Rain is
likely to hold off until after 18z Sun.
KPDX AND APPROACHES...Continuing VFR conditions beneath sct-bkn
high clouds through much of the period. A marine push overnight
may see low stratus reach up the Lower Columbia, with around a 30%
chance of cigs at 1-2 kft or lower. Light northwest winds today
will turn out of the south overnight. -Picard
&&
.MARINE...Relatively light winds of 10 kt or less expected
through Saturday as a frontal band remains stalled well offshore
to the north and west, and surface high pressure continues to
gradually weaken over the coastal waters. Seas 8 to 10 ft on
Saturday as a fresh northwest swell moves into the waters. As a
result of the elevated seas, have extended the Small Craft
Advisory across all waters as well as for the Columbia River Bar
through at least this evening.
A frontal system will approach the waters on Sunday resulting in
increasing southerly winds through Sunday night. At this time
there remains around a 25% chance of Gale Force wind gusts before
the cold front pushes inland Monday morning. As the middle of the
week approaches a more robust low pressure system is forecasted
to send a series of frontal system into the Pac NW through the
middle of next week. Guidance is showing around a 70-80% chance of
widespread Gales across all the waters as well as seas building
into the mid to upper teens. It should also be noted that there is
around a 5-10% chance of seas building to 20 ft or higher around
the same time frame. Seas to remain above 10 ft into the latter
part of the next week, but seas are expected to slowly subside.
-42/Hartsock
&&
.BEACH HAZARDS...A low pressure system anchored over the
northeast Pacific is sending a fresh, northwest swell of 7-10 ft
with a dominant period of 14-16 seconds into OR and WA waters.
This is resulting in an elevated sneaker wave threat through
Saturday evening. Waves can run up significantly farther on a
beach than normal, including over rocks and jetties. Sneaker
waves can suddenly knock people off of their feet and quickly
pull them into the frigid ocean which may lead to serious injury
or drowning. -42
&&
.PQR WATCHES/WARNINGS/ADVISORIES...
OR...None.
WA...None.
PZ...Small Craft Advisory until 11 PM PDT this evening for PZZ210-
     251>253-271>273.
&&
$$
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NWS PQR Office Area Forecast Discussion