958
FXUS66 KPDT 311215
AFDPDT

Area Forecast Discussion
National Weather Service Pendleton OR
515 AM PDT Sat Oct 31 2026

.KEY MESSAGES...

- Near- to below-normal temperatures into next week.

- Periodic showers today, then more widespread precipitation
  this evening into Sunday morning, mainly for eastern Oregon
  and far southeast Washington.

- Low chance (30% or less, except for freeze-prone areas) of a
  season-ending freeze for the eastern Columbia River Gorge
  Monday.

&&

.DISCUSSION...
Water vapor imagery shows a large, quasi-stationary low-
pressure system located just offshore of the Pacific Northwest,
centered in the vicinity of 45.2N, 129.5W. Middle and high cloud
cover is present across much of central to eastern Oregon and
southeast Washington, while mostly clear skies are noted over
north-central Oregon and south-central Washington. Radar
reveals isolated showers over the Columbia Plateau, mainly along
a line from the Bend metro to the Tri-Cities metro. At the
surface, most valley locations are nearly saturated at around
95-100% RH, and fog formation remains a concern for early
morning. That said, low stratus and any widespread fog currently
remains north and east of our forecast area of responsibility.

Over the weekend, the low is expected (99% confidence) to
transition to an open-wave trough and move inland. While chances
of precipitation have continued to trend downward, they are
still medium-high (30-70%) across the majority of
central/eastern Oregon and southeast Washington this evening
into Sunday. The best chance of significant precipitation will
be over northeast Oregon and southeast Washington where the NBM
places a 20-50% chance (locally higher in eastern Wallowa
County) of 0.25" through Sunday.

Ensemble solutions have coming to a concensus with regard to
when the trough will exit to the east and upper-level ridging
will build in from the Pacific; specifically, they suggest the
trough will slide east late Sunday afternoon into Sunday night,
and an amplified upper-level ridge will be overhead by Monday
morning. Given clearing skies and dry conditions, this presents
the best chance, albeit low at 30% or less, of a season-ending
freeze for the eastern Columbia River Gorge in the next week.
Freeze-prone portions of the Gorge do have somewhat higher
chances of freezing (locally in excess of 50%), but at this
time confidence remains too low to issue any watches.

Uncertainty in the 500-hPa pattern then grows Tuesday through
the remainder of the week. Ensemble clusters show a range of
solutions regarding a compact closed low Tuesday into Wednesday.
Most members (~55%) take it into the Pacific Northwest across
northern California or southern Oregon; the remaining members
keep the low offshore or delay its inland transit. The majority
of solutions (~80%) take the low too far south to produce
significant precipitation for our forecast area, and mostly dry
conditions (PoPs of 20% or less) are forecast to continue until
Thursday when ensemble guidance hints at the return of some more
active weather. Even then, chances of precipitation remain low
(40% or less, highest for the Cascades) until Friday when a more
robust low-pressure system is advertised.

&&

.AVIATION /12Z TAFS THROUGH 12Z SUNDAY/...
A range of conditions are forecast over the next 24 hours. Aside
from high confidence (80-100%) in low stratus at DLS, confidence
was too low (30% or less) to include any mention of sub-VFR
conditions this morning. Later today into Sunday morning, a
low-pressure system will move onshore, facilitating additional
chances of rain (generally 10-40%, highest at ALW). Moreover,
chances of sub-VFR CIGs increase significantly overnight into
Sunday morning, peaking at 80% at RDM/BDN and 20-40% elsewhere.
Winds of 12 kts or less are forecast through the period.

&&

.Preliminary Point Temps/PoPs...
PDT  50  35  51  31 /  10  20  20   0
ALW  51  38  51  34 /  10  30  30   0
PSC  54  35  57  31 /   0  10  10   0
YKM  54  32  60  30 /   0   0   0   0
HRI  51  33  55  30 /   0  10  20   0
ELN  50  27  56  24 /   0   0   0   0
RDM  48  26  48  20 /  10  50   0   0
LGD  56  36  49  29 /  20  40  30   0
GCD  58  35  47  29 /  10  40  30   0
DLS  55  36  60  34 /   0  30  10   0

&&

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

&&

$$

DISCUSSION...86
AVIATION...86