381
FXUS66 KPDT 151708
AFDPDT

Area Forecast Discussion
National Weather Service Pendleton OR
1008 AM PDT Wed Oct 15 2025

.AVIATION...

Challenges for the terminal forecasts this morning center on
ceilings at RDM and BDN. Most models are not capturing the low
stratus in place at around 1800 to 2200 ft the area. This is being
represented a little better by the GFS Local MOS, and will follow
this as a trend until the shallow stratus dissipates. Drier
northwest flow should render the area VFR for the rest of the
period. HiRes soundings do show significant drops in boundary
layer T-Td depressions after 10 am, so the stratus could happen
rapidly over a couple of hours. Russell/71

PREV DISCUSSION... /issued 256 AM PDT Wed Oct 15 2025/

DISCUSSION...Today through Friday: A deep upper low across CA/NV
will track east today, placing the PacNW under a northeast to
north flow aloft. A cool, dry airmass will continue to flow into
the region under this flow regime, and coupled with effective
radiative cooling in the overnight hours, will result in near to
below freezing overnight low temperatures through Thursday
morning.

Dry conditions will persist through Thursday as weak ridging will
move across the PacNW as the upper low to the south pushes into
the Rockies. By Thursday night, a shortwave with an attendant cold
front will arrive to the PacNW, but will only clip WA and northern
OR as it moves across the region Friday. Light rain showers will
develop along mainly the WA and northern OR Cascade crest with
snow showers mainly above 6.5kft. Cold front passage late
Thursday through Friday will also result in breezy west to
northwest winds through the Cascade gaps (gusts around 30-40 mph)
and the Columbia Basin (gusts around 25-35mph).

Saturday through Tuesday: Dry conditions will briefly return to
the forecast area late Friday through Saturday morning as an upper
level ridge pushes across the PacNW. By Saturday afternoon,
ensemble guidance depicts an upper low dropping out of the Gulf of
Alaska, then passing over the PacNW Sunday into early Monday with
widespread chances of rain showers and light mountain snow above
4.5kft. Chances of snow amounts greater than 2 inches will
generally be between 35-70% across the Cascade crest, northern
Blues, and along the Elkhorns. As for rain amounts, there is a
45-80% chance for 0.75 inches along the Cascade crest and upper
east slopes, a 25-50% chance for 0.5 inches in the northern Blues
and Wallowa county, and around a 30-50% chance for 0.25 inches
across the remainder of the eastern mountains. As for the lower
elevations, chances of 0.1 inches will range from 40% to 75%, with
chances around 30-35% in the WA Lower Columbia Basin. Confidence
is mod-high (60-85%) that breezy winds (gusts 25-40mph) will
develop with the trough passage Sunday, with strongest winds
through Cascade gaps.

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 Monday. However,
disagreement grows amongst ensemble guidance on the progression
of the synoptic pattern. While upper level ridging is favored
overall (82% of members from ECMWF, GFS, and Canadian), solutions
range from the ridge flattening and a shortwave clips the Cascade
crest with rain/snow showers, or upper level ridging prevails and
keeps the forecast area dry. Overall confidence in any mountain
shower chances is low-moderate (25-40%), with moderate confidence
(40-60%) in the lower elevations remaining dry with locally breezy
winds into the middle of next week. Lawhorn/82

&&

.PRELIMINARY POINT TEMPS/POPS...
PDT  57  34  63  41 /   0   0   0   0
ALW  57  38  62  45 /   0   0   0   0
PSC  60  33  63  40 /   0   0   0   0
YKM  62  34  64  39 /   0   0   0   0
HRI  59  33  63  42 /   0   0   0   0
ELN  60  31  61  39 /   0   0   0  10
RDM  58  26  63  31 /   0   0   0   0
LGD  58  30  62  36 /   0   0   0   0
GCD  58  30  61  35 /   0   0   0   0
DLS  64  39  65  47 /   0   0   0  10

&&

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

$$

SHORT TERM...99
LONG TERM....99
AVIATION...71