908
FXUS66 KPDT 242049
AFDPDT

Area Forecast Discussion
National Weather Service Pendleton OR
149 PM PDT Sat Oct 24 2026

.KEY MESSAGES...

1. Dry and cool conditions through Sunday

2. Pattern shift at the beginning of the week will bring
   slightly below seasonal temperatures

3. Increased chances of precipitation at the start of the week

&&

.DISCUSSION...
Current satellite is showing mid to high level clouds moving in over
the WA Cascades with high level clouds moving in over the OR
Cascades. Temperatures today will remain in the mid to upper 50s
with some isolated 60s in central OR and the Colombia Basin/Gorge.
Overnight temperatures will be sub-freezing along a few areas in
central OR, the Columbia Basin and Yakima Valley as well as through
the cold prone areas of Seneca and Wallowa Valley.

A weak upper level ridge is over the region through the day today
and most of tomorrow. This will keep the region under dry conditions
and cool conditions. In house calculations show the region to be at
or slight below normal seasonal temperatures for today with the NBM
showing temperatures in the mid to upper 50s across much of the
region. A few isolated locations in central OR and the John Day
Basin could see low 60s. Overnight temperatures will be sub-freezing
along a few areas in central OR, the Columbia Basin and Yakima
Valley as well as through the cold prone areas of Seneca and Wallowa
Valley.

A change in the synoptic pattern will lead to below seasonal average
temperatures continuing with the coolest day being Monday.
Deterministic guidance models show an upper level low moving into
the PacNW from the Gulf of Alaska by Sunday night. Models are in
good agreement with the initial low making its way onshore by Monday
afternoon. This will bring with it below seasonal average
temperatures with in house calculations showing nearly 5-10 degrees
below normal across central OR, eastern mountains and the foothills
of the Blues while the Gorge Basin and adjacent valleys will see
temperatures 1-5 degrees below seasonal normal. Monday NBM raw
ensembles show 60-80% chances of these areas seeing mid to upper
50s. Temperatures will steadily trend downward through midweek.

Not only will this upper level low bring cooler temperatures, but
models are also showing increased chances of precipitation. Looking
at the mean 24 hour precipitation statistic, rain/snow will be along
the Cascades as early as Sunday night. The rain will continue to
spread across the region through Monday becoming widespread between
11 AM and 5 PM. Looking at the NBM raw ensembles for the 24 hour
period, the ensembles show a 50-80% chance the eastern mountains,
Blues, foothills and the eastern slopes of the Cascades will see
near 0.05 inches of rain. The remaining locations will see 0.01-0.04
inches of rain. As the low continues to move to the east, clusters
and deterministic models begin to diverge. NBM shows rain showers
continuing on Wednesday while the variance between the models
differ in timing and amounts.


&&

.AVIATION /18Z TAFS THROUGH 18Z SUNDAY/...
VFR conditions will persist through the forecast period with
generally light winds. CIGs will continue to increase over the
region from west to east. No CIG or VIS issues will occur.

&&

.Preliminary Point Temps/PoPs...
PDT  32  59  33  56 /   0   0  20  40
ALW  38  61  38  56 /   0   0  10  30
PSC  29  58  33  58 /   0   0  20  20
YKM  32  58  36  58 /   0  10  20  20
HRI  30  58  32  57 /   0   0  20  20
ELN  25  54  30  54 /   0  10  30  40
RDM  28  64  27  51 /   0   0  30  60
LGD  34  61  37  57 /   0   0  10  80
GCD  30  64  34  55 /   0   0  10  60
DLS  36  60  38  59 /   0  10  40  60

&&

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

&&

$$

DISCUSSION...90
AVIATION...90