Hermiston, Oregon 7 Day Weather Forecast

Wx Forecast - Wx Discussion - Wx Aviation

996
FXUS66 KPDT 052240
AFDPDT

Area Forecast Discussion
National Weather Service Pendleton OR
240 PM PST Fri Dec 5 2025

.DISCUSSION...Rest of Today through Sunday: Wet conditions will
continue through this weekend as an upper ridge offshore continues
to guide a weak to moderate atmospheric river into the PacNW.

By this evening, a cold front boundary will be in the process of
crossing the forecast area while accompanied by a shortwave trough
aloft. Cooler air with the cold front will mainly bring
temperatures near to below freezing across mountain areas mainly
above 4kft to 5kft. That will result in moderate to locally heavy
snowfall across the WA Cascade crest, with high confidence that
White Pass will see 8 to 12 inches of snowfall through tomorrow
evening. The interior of the northern Blues will also see some
moderate snow accumulations, though confidence is only moderate
(50-60%) in snow amounts exceeding 6 inches above 5kft.

Breezy to windy conditions are also anticipated to develop across
the forecast area starting later this afternoon. A low level jet
(45-60kts) associated with the incoming shortwave trough will
move over the forecast area, with moderate to high confidence
(55-85%) that winds will mix down and impact many of our lower
elevation areas across north Central Oregon, the eastern Gorge,
and the Columbia Basin & adjacent valleys/foothills. Atypical for
this setup and wind direction, strong west to northwest winds are
also anticipated to develop through the Wallowa valley tonight
through tomorrow. In the aforementioned areas, expect sustained
winds of 25-40mph with gusts 40-55mph, while some ridges along the
east slopes of the Cascades can also anticipate wind gusts between
50-75mph through tomorrow afternoon.

A brief precipitation break will develop for the lower elevations
Saturday while light to moderate snow and/or rain will continue
across the mountains under northwest flow aloft. By Sunday
morning, another front and shortwave passage will ramp up
precipitation chances during the day, with light to locally
moderate snowfall above 4kft in the mountains, and light rain
elsewhere.

Monday through Thursday: Overall, ensemble guidance is in good
agreement of a progressive pattern consisting of several shortwave
and frontal systems parading through the PacNW Monday through
Thursday. ECMWF and GFS ensemble systems are also in a great
agreement that these systems will be accompanied by a prolonged AR
with IVT values peaking between 500 to 750 kg/m/s filtering into
eastern OR/WA for at least a 48 hour period early to mid next
week. What that translates to is a moderate to high confidence in
(60-80%) heavy precipitation amounts at least across the Cascade
crest and east slopes, as well as the Northern Blue mountains and
the Wallowa mountains. That said, ensemble guidance is in
disagreement over the timing and positions of the incoming systems
each day, which results in a low confidence (20-40%) in the exact
amounts of QPF that each area will see. But to provide an idea of
the potential QPF amounts, the NBM gives the WA Cascade crest a
30-70% chance of at least 5 inches of QPF over a 72-hour period
ending Thursday morning, and a 15-30% chance along the OR Cascade
crest. Meanwhile in the northern Blues, likely owing to much of
the precipitation falling out over the Cascades and west, NBM only
shows a 20-50% chance of 2 inches of QPF, which drops to a 10-20%
chance for 3 inches through Thursday morning. Due to the
warm/mild nature of the incoming AR/airmass, much of the
precipitation will be falling as rain across the mountain areas,
which translates to rises along area rivers and streams. Of note,
current river stage forecasts from the Northwest River Forecast
Center place many rivers originating or along the WA Cascade east
slopes into action stage by the middle of next week. Lawhorn/82


&&

.AVIATION...00Z TAFs...The winds are beginning to pick up ahead of
the front with PDT/BDN/ALW already seeing sustained winds 10-13kts
and gusts to 20kts. This has assisted with clearing out the FG/BR
and low CIGs with the exception of YKM which is still IFR due to
CIGs below 500 feet. Timing of the winds remains the challenge this
forecast period, however, guidance does show that winds are expected
to pick up across the remaining TAF sites within the next hour or
two allowing all sites to go VFR by 00-02Z (60-80% confidence).
Winds will be between 15-25 with some isolated 30 kts (PDT) sustained
with gusts to 35 kts and higher. All sites are expected to stay VFR
with only DLS seeing a slight chance (30-40%) of low CIGs after 20Z
Sunday. 90


&&

.PRELIMINARY POINT TEMPS/POPS...
PDT  40  51  38  52 /  30  40  40  80
ALW  41  50  40  51 /  50  50  50  80
PSC  41  55  39  52 /  10  10  10  70
YKM  38  55  34  50 /  40  20  20  70
HRI  43  55  39  53 /  10  20  20  70
ELN  35  48  32  44 /  60  40  30  70
RDM  32  49  31  54 /  30  20  10  50
LGD  38  46  33  44 /  80  70  70  80
GCD  34  45  32  47 /  50  40  40  80
DLS  47  55  44  54 /  70  60  70  90

&&

.PDT WATCHES/WARNINGS/ADVISORIES...
OR...Wind Advisory until 10 AM PST Saturday for ORZ041-044-507-508-
     510.

     Wind Advisory until 1 PM PST Saturday for ORZ050.

WA...Wind Advisory until 10 AM PST Saturday for WAZ024-521.

     Wind Advisory from 7 PM this evening to 7 AM PST Saturday for
     WAZ026>029.

     Winter Weather Advisory from 7 PM this evening to 7 PM PST
     Saturday for WAZ522.

&&

$$

.DISCUSSION...82
AVIATION...90