665
FXUS66 KPDT 251125
AFDPDT

Area Forecast Discussion
National Weather Service Pendleton OR
425 AM PDT Fri Sep 25 2026

.KEY MESSAGES...
- Widespread rain showers and breezy to windy conditions will
  develop throughout today, with an isolated thunderstorm or two
  in the Washington Cascades

- Wind Advisories in effect today from Central Oregon to the
  Lower Columbia Basin

- Dry conditions and light winds return over the weekend, then a
  return of periodic light showers in the Cascades next week

&&

.DISCUSSION...Satellite and radar imagery tonight show a
surface low and upper trough swinging into the PacNW, with a
cold front pushing a band of rain across the Cascade east
slopes.

Today through Sunday: The north/south oriented band of rain
leading the cold front and surface low will continue to push
east this morning and exit in the afternoon. Post frontal
showers will continue across the Cascade crest and east slopes
thanks to support from the upper trough passage, but will
diminish through the evening hours as the trough exits to the
northeast. There remains a widespread 60-90% chance of at least
measurable rain across much of the forecast area today, with
only a 30-45% chance of 0.25 inches in the northern Blues and a
65-95% chance of 0.5 inches along the Cascade crest and east
slopes. In addition to precipitation, the upper trough and
surface low passage will bring increasing west to southwest
winds across the forecast area. Winds will be 25-35 mph with
gusts 35-50 mph through the Cascade gaps, central OR, and into
the Columbia Basin and adjacent foothills/valleys. Winds 15-25
mph and gusts up to 35 mph are expected in most other locations,
with stronger winds along the Cascade Crest. Surface winds will
be supported by a 40-50kt low level jet that will mix down
across portions of the Columbia Basin this afternoon. Wind
advisories are in effect across central/north central OR,
Columbia Basin/Gorge, Yakima Valley, and the Blue Mountain
foothills from 8AM to 11PM today.

Shower activity and windy conditions will diminish tonight into
Saturday as the upper trough and surface low exit to the
northeast. Deterministic and ensemble guidance continue to
depict weak broad troughing developing offshore the PacNW
Saturday, then sliding across the region through Sunday. The
trough passage will lack moisture and mid to upper level jet
support, resulting in dry conditions with light winds. It will
however continue to support below normal temperatures across the
region, with afternoon highs in the 60s. While widespread
overnight freezing temperatures (outside of the mountain zones)
are not expected to develop, areas of the Wallowa valley and
central OR will see a  25-65% chance of freezing morning
temperatures Saturday. The make or break for freezing
temperatures will be cloud cover in the overnight and early
morning hours, though confidence is low (25-35%) in extent of
cloud cover for tomorrow morning.

Monday through Thursday: Ensemble guidance is in good agreement
of mostly zonal flow developing over the PacNW as an upper
trough develops over AK and northern BC and ridging out in the
eastern Pacific through Tuesday. While Monday will remain mostly
dry, ensemble cluster solutions hint at a shortwave and
attendant weak frontal passage bringing light rain showers to
the Cascade crest and east slopes throughout Tuesday, though
about 30-45% of cluster members bring light rain to the northern
Blues latter half of Tuesday. Winds are favored to remain light
to locally breezy with the system passage Tuesday (confidence
60-65%).

Disagreement grows amongst ensemble members mid week in the
evolution of the synoptic pattern. Solutions range from ridging
Wednesday then upper trough passage Thursday to slow moving
troughing Wednesday into Thursday. Either solutions would favor
more mountain precipitation, but with plenty of disagreement
amongst the members, confidence is low (20-25%) in extent,
timing, and amounts of precipitation next week.

&&

.AVIATION /12Z TAFS THROUGH 12Z SATURDAY/...VFR conditions to
prevail through the period. Cold front passage will continue to
bring rain shower impacts to all sites this morning, with
showers expected to end in western sites around 13-14Z, and
showers to impact sites PSC/PDT/ALW between 12Z to 16-18Z.

Winds will increase through this morning and persist through the
afternoon, with winds generally 15-25kts and gusts 30-40kts.
Winds will decrease in the evening across most sites, though
sites PDT/ALW will see breezy winds persist to around 6-8Z.
While not included in the current TAF, there is a chance
(50-70%) that gusts may periodically reach 40kts or greater at
site PSC between 18Z-00Z. Will continue to monitor incoming
guidance, as an airport weather warning may be warranted during
that period. Lawhorn/82

&&

.Preliminary Point Temps/PoPs...
PDT  69  40  65  41 /  90   0   0   0
ALW  69  45  66  44 /  90  10   0   0
PSC  72  43  69  41 /  70   0   0   0
YKM  65  40  64  40 /  30   0   0   0
HRI  72  43  68  40 /  80   0   0   0
ELN  61  36  60  36 /  50  10   0   0
RDM  59  31  64  33 /  10   0   0   0
LGD  66  38  64  38 /  60   0   0   0
GCD  66  37  67  40 /  50   0   0   0
DLS  66  45  68  45 /  60  10   0   0

&&

.PDT WATCHES/WARNINGS/ADVISORIES...
WA...Wind Advisory from 8 AM this morning to 11 PM PDT this evening
     for WAZ024-027-521.
     Wind Advisory from 11 AM this morning to 11 PM PDT this
     evening for WAZ028-029.
OR...Wind Advisory from 8 AM this morning to 11 PM PDT this evening
     for ORZ041-044-507-508-510.
     Wind Advisory from 8 AM this morning to 5 PM PDT this
     afternoon for ORZ511.

&&

$$

DISCUSSION...82
AVIATION...82