190
FXUS66 KPDT 152238
AFDPDT

Area Forecast Discussion
National Weather Service Pendleton OR
238 PM PST Sat Nov 15 2025

.DISCUSSION...

Key Messages:

1. Widespread showers and breezy winds Monday.

2. Near normal temperatures Tuesday onward.

3. Precipitation returns late Wednesday into Thursday.


Current radar and visible satellite imagery shows some light
returns along the Cascade crest under partly to mostly cloudy
skies. This is in response to a weak transient ridge of high
pressure that will be departing to our east tonight as the next
system approaches the coast. An upper level low pressure system,
currently located off the coast of California, will slide up the
backside of the exiting ridge to bring rainfall across Central
Oregon and the John Day Basin shortly after midnight tonight and
will continue to spread north by late morning. Widespread rain
chances (40-80%) stay heightened into the early morning hours on
Monday before slowly confining to the Cascades and Blue Mountains
late Monday into Tuesday. Snow levels will be on a slow decline,
from 6500-7500 feet Sunday, 4500-5500 feet Monday, and 3500-4500
feet Tuesday. However, the bulk of the moisture will arrive
Sunday, only leading to snow amounts of less than an inch across
our mountain zones Monday and Tuesday. The inclusion of moisture
from the southern low pressure along with the incoming upper level
trough from the west will allow for rain amounts of 0.10-0.20"
across the northern Blue Mountain foothills and portions of the
Lower Columbia Basin (including Tri-Cities and Hermiston).
0.30-0.45" of rainfall is likely through the Grande Ronde Valley
and the John Day Basin, with less than 0.10" expected through the
Eastern Gorge (The Dalles), Central Oregon (Bend, Redmond), and
the Yakima/Kittitas Valleys. An additional 0.05" is likely across
the northern Blue Mountain foothills, Central Oregon, John Day
Basin, and the Grande Ronde Valley Monday, as only a trace is
expected for the Lower Columbia Basin. Deterministic and ensemble
guidance is still struggling with the strength of the incoming
upper level trough, which directly relates to the above rain
amounts. This leads to moderate (50-60%) confidence in forecasted
accumulations, primarily across the Lower Columbia Basin and
northern Blue Mountain foothills. Currently, 56% of ensemble
members advertise a stronger system and wetter scenario, which
would inflate these rain amounts by about 0.05".

This passing system will also attribute to breezy winds across the
Lower Columbia Basin, northern Blue Mountain foothills, Eastern
Gorge, and the Kittitas Valley as sustained west winds of 10-15 mph
and gusts of up to 25 mph are likely. Much like precipitation
amounts, winds are also susceptible to the incoming system`s
strength. Thus, 56% of ensembles align more with a windier
scenario, with the NBM suggesting a 40-60% chance of wind gusts
reaching 25 mph or greater. However, with ensembles hinting at a
slightly windier outcome Monday, the wind forecast may bump up
slightly as the event nears.

Upper level flow becomes more from the northwest in the wake of
the Sunday/Monday system, dropping high temperatures about 10
degrees across the Lower Columbia Basin from Monday to Wednesday.
Highs midweek are expected to reach into the upper 40s to low
50s with lows hovering around freezing, which is near normal for
this time of year. These normal temperatures should stay through
the week, with a slight uptick Friday when west-southwest flow
aloft returns.

These near normal temperatures midweek are a result of another
incoming upper level trough, returning scattered to widespread
showers to the region. Ensembles highlight timing and system
strength inconsistencies, with 43% of members aligning with the
current forecast, 31% of members hinting at a slightly wetter
outcome, and 25% of members suggesting a drier scenario. The
current consensus is rain amounts of less than 0.10" across the
Lower Columbia Basin, Central Oregon, and the northern Blue
Mountain foothills. 75




&&

.AVIATION...00Z TAFs...Sites will initially start at VFR. Although a
tough forecast, I`m a bit more confident to input some fog for DLS
overnight starting at 14Z. Guidance is a bit stronger on this than
earlier in the day, so went ahead and put a group for 1/2SM fog. Fog
is of course a bit tricky to forecast this time of year, so
additional monitoring is needed if the outlook needs to be updated
for the 06Z TAFs. Other sites that could see some sub-MVFR
conditions is ALW with a PROB30 group at the tail end of the
forecast period. This will be in due part of the weather system and
will be dependent where the heaviest rain forms. All sites will
experience some precipitation by late tomorrow morning through the
early afternoon hours. That said, all sites have at least a 5-15%
chance of seeing sub-MVFR conditions briefly, depending where the
heaviest rain forms. /95


&&

.PRELIMINARY POINT TEMPS/POPS...
PDT  41  52  43  55 /   0  70  80  60
ALW  44  52  46  55 /  10  80  90  70
PSC  44  54  43  56 /   0  50  60  30
YKM  43  58  42  56 /  10  20  40  10
HRI  43  52  44  55 /   0  60  60  40
ELN  43  54  39  51 /  20  30  60  20
RDM  36  57  36  51 /   0  30  60  30
LGD  40  54  43  53 /  10  90  90  80
GCD  42  54  42  53 /  20  90  90  70
DLS  47  57  47  54 /  10  40  70  40

&&

.PDT WATCHES/WARNINGS/ADVISORIES...
OR...None.
WA...None.
&&

$$

SHORT TERM...75
LONG TERM....75
AVIATION...95