804
FXUS66 KPDT 201140
AFDPDT

Area Forecast Discussion
National Weather Service Pendleton OR
340 AM PST Thu Nov 20 2025

Updated Aviation Discussion

.DISCUSSION...Overnight water vapor imagery depicts a closed low
descending down toward southern California, with our forecast area
being clipped by its northeastward flank. Light showers have
circulated across western Oregon and into the east slopes of the
Cascades as a result, however given this low`s trajectory, moisture
is relatively paltry overall, so precip impacts associated with this
system are expected to be minimal. The northerly flow aloft
associated with the forward flank of this system may provide some
light shower activity across the eastern mountains and into the
foothills (30-40% chance), but accumulations are expected to be a
couple hundredths at best.

For the rest of Thursday, the PacNW will transition into a more
ridge-like pattern through the weekend, making for a relatively dry
forecast. There is a `dirty` component to the ridge, with models
suggesting enough moisture transport to support low-end shower
chances (20-40%) across the central WA Cascades, however QPF will be
limited until around Sunday evening, when models try to bring in a
broad trough through the forecast area. Should note that ensemble
guidance doesn`t show particularly strong agreement on the amplitude
of this trough, but that overall guidance suggests that this Sunday
night into Monday timeframe looks to be the area`s next best chance
for area-wide precip. This system does look to bring in enough cold
air to drop snow levels down to around 2500-3000 ft for the central
Washington Cascades, where the bulk of precip is expected to occur.
This would support snow at Snoqualmie Pass, but forecasted amounts
are light (only a couple of inches) as this trough looks to be
pretty quick-moving. Still, this looks to be the most significant
synoptic-level feature across ensemble guidance for the next week,
so focus will be on this potential trough over the coming days.

Patchy fog may develop this weekend due to the ridge pattern, but
otherwise our lowlands are not anticipated to see impactful
sensible weather over the next 4-5 days. Ensembles diverge in
solutions beyond the midweek next week due to the progressive
nature of the synoptic pattern, so forecast confidence is
unfortunately too low (15-25%) in predicting how Thanksgiving will
shape up this far out. 74

.AVIATION...12Z TAFS...A mix of VFR and MVFR or lower conditions
are expected through the period. An upper low approaching the
PacNW is light precipitation across the forecast area, with
scattered light rain across the Lower Columbia Basin. All sites
will see periodic light rain this morning, with precipitation
ending before 18Z. Site RDM is currently the only site with
degraded CIGs, with bkn-ovc CIGs as low as 700ft. MVFR or lower
CIGs are expected to develop at all sites this morning with or
after light precipitation ends. CIGs will improve to VFR
categories this afternoon, with VFR conditions persisting through
the remainder of the period. Winds will be light, 12kts or less,
through the period. Lawhorn/82

&&

.PRELIMINARY POINT TEMPS/POPS...
PDT  47  29  50  31 /  40   0   0   0
ALW  44  34  49  36 /  40  10  10   0
PSC  49  30  48  31 /  20   0   0   0
YKM  51  28  48  30 /  30   0   0   0
HRI  49  30  48  31 /  30   0   0   0
ELN  47  27  47  31 /  30   0  10  10
RDM  47  21  51  24 /  20   0   0   0
LGD  47  29  50  29 /  60  10   0   0
GCD  47  29  50  29 /  70   0   0   0
DLS  52  34  50  37 /  40   0   0  10

&&

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

$$

DISCUSSION...74
AVIATION...82