343
FXUS66 KPDT 081111
AFDPDT

Area Forecast Discussion
National Weather Service Pendleton OR
411 AM PDT Wed Oct 8 2025

.UPDATED AVIATION DISCUSSION...

.PREV DISCUSSION... /issued 225 AM PDT Wed Oct 8 2025/

DISCUSSION...Water vapor imagery reveals a shortwave trough
digging south off the coast of the PacNW. Ensemble NWP guidance
is in excellent agreement (>95% chance) that this wave will
develop into an offshore closed low through the day. Analysis of
ensemble clusters suggests a very high chance (>90%) that the low
will then deepen and spin offshore through Thursday. Have seen a
flip-flop in guidance again with respect to how far east
precipitation chances will spread Wednesday night and Thursday,
with higher PoPs (40-65%) now roughly confined to the Cascades and
their eastern slopes with lower PoPs (15-30%) extending eastward
across central and north-central Oregon into south-central
Washington.

Ensemble clusters indicate the longwave pattern will almost
certainly (>90% chance) become more progressive late Friday
through the weekend. While some differences are evident among
ensemble clusters, all track the closed low inland over the
Pacific Northwest through Saturday, with a second shortwave
trough digging southeast out of BC late Saturday through the
weekend. The combination of these two systems will induce medium-
high chances (45-90%) of precipitation for the Cascades and Blues
with a low-medium chance (20-60%) of rain for the lower
elevations late Friday through Sunday. Snow levels will drop
sufficiently low (4-5 kft) Saturday night through Sunday to allow
a medium-high chance (50-80%) of measurable snow in the mountains.
NBM probabilities suggest a 30-60% chance of at least 2" of snow
for areas above 4500 feet.

The lack of significant moisture transport into the region will
limit precipitation totals over the weekend, especially for the
lower elevations. While the Cascade crest has a medium-high
(50-80%) chance of 1" of precipitation for the 72-hr period ending
Sunday night, chances elsewhere are <30%. The Blues do have a
30-70% chance of 0.5" of precipitation for the aforementioned
period. The lower Columbia Basin has low (15-35%) chances of
0.25", while communities in central Oregon and along the Blue
Mountain foothills have medium (40-65%) chances of 0.25" or
greater.

Breezy westerly winds are forecast Saturday into Sunday as the
second shortwave tracks across the region, though the forecast
magnitude of these winds has decreased since yesterday. NBM
probabilities now suggest a low-medium (20-50%) chance of winds
reaching advisory thresholds across wind-prone areas of the
Columbia Gorge/Basin and adjoining foothill and valley areas.
Plunkett/86

AVIATION...12Z TAFs...VFR conditions will prevail through the
forecast period. All TAF sites will begin to see CIGs 15-25kft
after 18Z with an increase in winds nearing 12 kts at DLS/RDM/BDN.
Elsewhere will remain below 10kts. Bennese/90

&&

.PRELIMINARY POINT TEMPS/POPS...
PDT  74  44  72  46 /   0  10  10  10
ALW  77  49  73  50 /   0  10  10  20
PSC  74  42  73  45 /   0  10  10  10
YKM  72  47  71  48 /   0  30  30  20
HRI  74  43  73  46 /   0  10  10  10
ELN  69  42  70  43 /   0  40  30  30
RDM  74  38  67  38 /   0  40  30  20
LGD  74  45  76  45 /   0   0   0  10
GCD  76  46  76  45 /   0  10  10  10
DLS  71  49  70  51 /   0  50  40  40

&&

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

$$

SHORT TERM...86
LONG TERM....99
AVIATION...90