386
FXUS66 KPDT 171133
AFDPDT

Area Forecast Discussion
National Weather Service Pendleton OR
433 AM PDT Fri Oct 17 2025

Updated Aviation Discussion

.DISCUSSION...Today through Saturday Morning: Cloud cover has
increased across the region as a shortwave with an attendant cold
front will arrive to the PacNW. Light rain showers will develop
along mainly the WA Cascade crest with light snow showers mainly
above 6.5kft. The cold front passage today will result in breezy
to locally windy west to northwest winds through the Cascade gaps
(gusts around 30-45 mph) and the Columbia Basin (gusts around
25-35mph). There is moderate confidence (55-70%) that localized
areas of the Kittitas valley may see sustained winds around 30 mph
with occasional gusts between 45-50mph this afternoon. That said,
confidence is too low to issue any wind highlights for the
Kittitas valley at this time. Otherwise, while the region is well
within the Fall season, there is a moderate concern for elevated
fire weather conditions developing this afternoon. CAMs and
deterministic model guidance indicate the potential for a very dry
airmass (RHs 5-15%) around 700mb to mix down along the WA Cascade
east slopes and into the Kittitas valley this afternoon and
overlap with strong winds, producing critical fire weather
conditions. At this time, confidence is only moderate (55%) in
widespread Red Flag conditions this afternoon.

Dry conditions with light winds will briefly return to the
forecast area late Friday through Saturday morning as an upper
level ridge pushes across the PacNW (confidence 80-90%).

Saturday Afternoon through Monday Morning: By Saturday afternoon,
ensemble guidance continues to be in great agreement of an upper
low and surface cold front dropping out of the Gulf of Alaska,
then passing over the PacNW Sunday and exiting by late Monday
morning. This system will bring with it widespread chances of rain
showers and light mountain snow above 5kft, but as compared to
model runs from 24 hours ago, rain amounts east of the Cascade
crest have been reduced owing to higher confidence (70-85%) in a
faster and further north trough passage. Confidence is at least
mod-high (65-80%) in rain amounts between 0.5-0.75 inches or
higher along the Cascade crest, 0.25-0.5 inches across the
northern Blues and the Eagle Cap Wilderness, 0.1-0.2 along the
northern Blue mountain foothills and lower Cascade east slopes,
with a few hundreths up to 0.1 inches elsewhere. A pressure
gradient developing across the Blue Mountains will result in
breezy south winds (gusts 25-45mph) developing through the Grande
Ronde Valley and north-south oriented canyons/valleys across
Wallowa county throughout Saturday night as the trough approaches.
Otherwise, the incoming upper trough/cold front will bring breezy
west to southwest winds through the Columbia Basin and Cascade
gaps Sunday (confidence 70-85%).

There is good agreement amongst ensemble guidance that upper
level ridging will build back over the PacNW with mostly dry
conditions and lingering light showers across the Cascades and
portions of the northern Blues Monday.

Monday Afternoon through Thursday: Moderate confidence (50-65%)
that upper level ridging will persist over the region, but will
briefly flatten as a shortwave crosses into southern BC early
Tuesday. Light showers along the WA Cascade crest will be
possible, but with a stronger shortwave the northern OR Cascade
crest may see light showers as well. Good agreement amongst
ensemble members in ridging building back over the PacNW with
mostly dry conditions(confidence 40-60%) Tuesday night through
Wednesday morning. Wednesday afternoon through Thursday, cluster
ensemble solutions all depict some form of troughing developing
off the PacNW coast with upper level ridging pushing of to the
east, though there is disagreement on timing. That said, ensemble
guidance favors rain and high mountain snow developing sometime
Thursday along the Cascade crest, with dry conditions elsewhere.
Lawhorn/82

.AVIATION...12z TAFs...VFR conditions to prevail through the
period. Sct-Ovc CIGs will continue over sites through the morning
and early afternoon as a weather system moves overhead, with skies
clearing by this evening. Winds will increase to 12-15kts with
gusts up to 25kts at sites RDM/YKM/ALW/PSC this afternoon; sites
DLS/PDT will see strong winds to around 20kts and gusts up to
30kts this afternoon. Winds will weaken to 12kts or less during
the evening and early nighttime hours at the aforementioned sites.
Winds at site BDN will remain light, 12kts or less, through the
period. Lawhorn/82

&&

.PRELIMINARY POINT TEMPS/POPS...
PDT  65  34  64  45 /   0   0   0  40
ALW  64  39  64  47 /   0   0   0  60
PSC  67  32  61  47 /   0   0   0  40
YKM  66  34  59  41 /   0   0   0  60
HRI  67  33  62  46 /   0   0   0  40
ELN  59  28  56  37 /  10   0  10  70
RDM  65  26  70  40 /   0   0   0  20
LGD  63  31  64  44 /   0   0   0  30
GCD  64  31  69  43 /   0   0   0  10
DLS  66  38  65  49 /  10   0   0  60

&&

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

$$

DISCUSSION...82
AVIATION...82