328
FXUS66 KPDT 181146
AFDPDT

Area Forecast Discussion
National Weather Service Pendleton OR
446 AM PDT Sat Oct 18 2025

.Updated for Aviation...

.AVIATION...
12Z TAFS...VFR conditions are expected through the TAF period.
All terminals will start out dry, then RA will move in from west
to east overnight and toward the end of the period. Winds will
mainly be 10 kts or less, except at DLS which will se winds gust
to around 25 kts by early Sunday morning.

&&

.PREV DISCUSSION... /issued 338 AM PDT Sat Oct 18 2025/

DISCUSSION...Satellite depicts mostly clear skies, with the
Kittitas/Ellensburg area with some partly cloudy skies continuing
through the night as a weak ridge settles over the area. Some
freezing temps across the region expected tonight, with areas near
Kittitas/Ellensburg reaching the low 30s, with higher elevated
areas dropping to the mid to high 20s. Expect the rest of the
night to be clear and dry through most of the morning. Radiative
cooling is expected to be more effective in places of clearer
skies (i.e. the southern part of the CWA). Would not be surprise
with the clear skies coupled with light wind that temperatures
might drop slightly lower than expected.

Precipitation chances increase heading into Saturday afternoon, as
an approaching warm front will increase instability and moisture
advection throughout the day. Most precip will fall in the form of
stratiform rain showers across the Cascades, Kittitas Valley, and
the Columbia Basin. The heaviest QPF will be located in parts of
the WA Cascade crests with up to three-quarters of an inch
expected (>80% chance) while decreasing up-to 0.05 inches going
toward the Ellensburg/Kittitas Valley (>80% chance). Sunday
morning will bring a more active pattern as a trough begins to
pull its way into the PacNW accompanied with a cold front. As the
cold front pushes through Sunday morning, lapse rates increase to
7.8-8.1C/km (higher values located across the Dalles and Cascade
slopes) with Bulk wind shear values of 40-50 knots. CAPE values,
however, mostly show <100 J/kg according to NBM members and that
has me hesitated to add more widespread thunderstorm coverage past
the Cascade slopes. For now, have kept thunderstorm chances at
5-10%, but may re-assess if guidance suggests if thunderstorm
chances need to be adjusted later today. Additionally, this system
will bring some light mountain snow showers when the front will
drop snow levels at around 5000-5500 feet, but any accumulation is
expected to be light.

Model guidance has slightly increased the trends for winds going
through Sunday, with NBM showing increased chances of >45 mph
gusts through parts of the Southern Blue Mountains and approaching
the Hermiston area. The cold front will create tightening pressure
gradients increasing Wind Advisory criteria chances for places
like the Gorge (30-50% chance), Hermiston/Pendleton area (40-60%
chance), WA Basin (40-60% chance), and the Kittitas Valley (50-70%
chance). Confidence that criteria will be met and wind advisories
will be issued still remains moderate (50-60% chance), but
additional monitoring for trends will continue with the
approaching active weather pattern. Model guidance is in
agreement that after the system pushes through Sunday, the
pattern will shift to a more dry/stable atmosphere through mid-
next week as ridging returns to dominate the upper-levels.
Temperatures begin a warming trend through Wednesday as skies
clear out and rain moves out of the picture until another
approaching system makes its way by end of next-week.

AVIATION...06Z TAFS...VFR conditions currently across all sites,
which will stay the course through the period. Winds have decreased
and will stay below 10 kts at all terminals through Saturday
evening. Clear skies persist Saturday morning, but increasing clouds
associated with an incoming system will drop ceilings to 15-20 kft
in the evening. Light rain is also expected to occur at KYKM toward
the end of the period. 75

&&

.PRELIMINARY POINT TEMPS/POPS...
PDT  64  46  61  39 /  10  70  70  20
ALW  64  48  60  43 /  10  90  80  40
PSC  61  46  64  38 /  10  60  40  10
YKM  58  40  61  35 /  20  70  40  10
HRI  63  46  64  40 /  10  60  50  10
ELN  53  36  56  34 /  30  80  50  30
RDM  70  40  57  26 /   0  40  50  10
LGD  65  44  57  36 /   0  70  90  30
GCD  69  46  59  33 /   0  30  60  10
DLS  64  48  62  44 /  20  80  70  30

&&

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

$$

SHORT TERM...95
LONG TERM....95
AVIATION...77