035
FXUS66 KPDT 061737
AFDPDT

Area Forecast Discussion
National Weather Service Pendleton OR
1037 AM PDT Mon Oct 6 2025


.UPDATED AVIATION.

.AVIATION...00Z TAFs...TAFs are generally VFR for the most part
with the only exclusion of some TEMPO haze in YKM that has
brought VIS down to MVFR. Will expect to move out later on and
remain VFR for the remainder of the period. Winds for the most
part are generally light and variable with clear skies dominating.


.DISCUSSION...An upper-level ridge of high
pressure extends from the northeastern Pacific Ocean into the
Pacific Northwest. Beneath the ridge, clear skies coupled with
predominantly light winds and a dry air mass (PWATs of 0.25-0.60")
will facilitate efficient radiational cooling. Isolated near-
freezing to freezing temperatures are expected (80% confidence)
this morning for low-lying, cold- prone locations within the
Yakima and Kittitas valleys, Columbia Basin, and along the Blue
Mountain foothills; no Freeze Warnings have been issued due to
limited spatial extent. However, have added a mention of frost in
the forecast this morning as well as Tuesday morning. Elsewhere,
more widespread sub-freezing temperatures are expected (80-100%
confidence) this morning for central Oregon, the John Day Basin,
and the Grande Ronde and Wallowa valleys. Freeze Warnings remain
in effect until 10 AM for the aforementioned zones.

By Tuesday, the ridge will flatten as a couple vort lobes drop
south from the Gulf of Alaska and BC and carve out an offshore
closed low. Analysis of ensemble clusters suggests a very high
chance (>90%) that the low will deepen and spin offshore of the
Pacific Northwest Wednesday through Thursday. Any precipitation
associated with the low will likely (75% chance) remain pinned to
the Cascades and their immediate east slopes.

Ensemble clusters indicate the longwave pattern will almost
certainly (>90% chance) become more progressive Friday through
the weekend. While some differences in exact timing are apparent
among ensemble clusters, all ensemble systems track the closed
low inland over the Pacific Northwest Friday through Saturday,
with a second shortwave trough digging southeast out of BC
Saturday through Sunday. The combination of these two systems will
facilitate medium-high chances (55-85%) of precipitation for the
Cascades and Blues with a low-medium chance (20-50%) of rain for
the lower elevations late Friday through Sunday. Snow levels will
drop sufficiently low (4-5 kft) over the weekend to allow a
medium-high chance (50-80%) of measurable snow in the mountains.

Breezy westerly winds are also forecast Saturday into Sunday.
NBM probabilities suggest a low-medium (30-60%) chance of winds
reaching advisory thresholds, and the ECMWF EFI for wind and wind
gusts ranges from 0.5-0.8 across wind-prone areas of the Columbia
Gorge/Basin and adjoining foothill and valley areas. Plunkett/86


&&

.PREV DISCUSSION... /issued 408 AM PDT Mon Oct 6 2025/


&&

.PRELIMINARY POINT TEMPS/POPS...
PDT  40  74  43  73 /   0   0   0   0
ALW  45  74  48  74 /   0   0   0   0
PSC  37  72  40  73 /   0   0   0   0
YKM  41  72  41  70 /   0   0   0   0
HRI  38  73  41  73 /   0   0   0   0
ELN  37  70  38  67 /   0   0   0   0
RDM  31  75  34  73 /   0   0   0   0
LGD  35  72  42  73 /   0   0   0   0
GCD  36  73  38  76 /   0   0   0   0
DLS  44  76  46  71 /   0   0   0   0

&&

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

$$

SHORT TERM...86
LONG TERM....86
AVIATION...95