A strong upper level trough slid down the coast of British Columbia facilitating a period of strong southerly winds along Blue Mountains foothills, and heavy snow across the mountain areas between November 29th and December 1st. Wind gusts of 60-65mph were measured along the foothills of the northern Blue Mountains and snow accumulations of up to 22 inches were reported in the Washington…
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The episode as NWS PDT wrote it up.
A strong upper level trough slid down the coast of British Columbia facilitating a period of strong southerly winds along Blue Mountains foothills, and heavy snow across the mountain areas between November 29th and December 1st. Wind gusts of 60-65mph were measured along the foothills of the northern Blue Mountains and snow accumulations of up to 22 inches were reported in the Washington Cascades, and up to 24 inches in portions of the northern Blue Mountains of Oregon and Washington.
The local office's own words before the first event, as it sent them, from the Iowa Environmental Mesonet's archive of National Weather Service text.
NWS Pendleton, OR wrote its last area forecast discussion before the first event at Nov 29, 3:33 PM PST, 4 hours 27 minutes earlier.
Area Forecast Discussion
National Weather Service Pendleton OR
333 PM PST Tue Nov 29 2022
.UPDATED AVIATION DISCUSSION...
.SHORT TERM...Tonight through Thursday...An active pattern
remains through the next several days as a deep upper low brings
multiple days worth of precipitation and heavy snowfall, primarily
along the Cascades and the Blue Mountains, though adjacent low-
lying regions may also see some impactful conditions as well.
The aforementioned low begins its descent through the middle of
the week, skirting the coast of the PacNW. This will bring an
abundance of moisture and promote widespread precipitation, with
heavy snow likely for the mountains and a mixture of rain and
snow for the low lying elevations. The one caveat to this system
will be the southwesterly flow it brings tomorrow, which should
promote warmer temperatures for the day and will limit how low
snow elevations can remain. The Cascades should see a widespread 1
to 2 feet in the high elevations, while the valleys will see
closer to 6 to 12 inches on average. Very gusty winds nearing 40
mph will also promote periods of blowing snow which will
considerably reduce visibilities and impact travel in the region.
Similarly, the Blue Mountains of Washington and Oregon will see
around 6 to 18 inches, once again primarily across the high
terrain near the borders of the two states. The southern Blue
Mountains of Oregon aren't expected to see nearly as much snow,
though amounts could exceed 10 inches for the high terrain here.
Finally, adjacent low- lying areas near the Blues could see gusty
winds, with wind gusts currently around 35 to just under 40 mph.
This precludes a wind advisory, but conditions will near the
threshold and subsequent updates could warrant a wind advisory.
The eastern mountains including the Wallowas will see heavy
snowfall for the highest elevations, but the low-lying areas
should remain just out of advisory criteria for now as only a few
inches are expected.
The temporary warm up seen on Wednesday will decay as cooler air
drops in with the descent of the low, with temperatures 5 to 10
degrees colder on Thursday. The low will continue its descent and
eventually transition eastward during the day, moving through the
region and bringing a high pressure ridge by the end of the
forecast period. This will be only a transient ridge however, as
the next low begins to approach by the end of the short-term
period. Goatley/87
.LONG TERM...Friday through Tuesday...Active north to northwest
flow aloft keeps below normal temperatures in place moving forward
as a weather disturbances swings into the Pacific Northwest Friday
night into Saturday followed by second potential disturbance Monday
into Tuesday. Uncertainty regarding precipitation/snowfall coverage
and amounts for portions of the CWA like the Columbia Basin are
noteworthy for both systems, providing ambiguity in potential
impacts outside of the mountain zones. Nevertheless, the ECMWF
Extreme Forecast Index maintains below normal high and low
temperatures into early next week so winter-related conditions
remain the focus.
Both ensemble and deterministic guidance are in fairly good
agreement regarding the large scale pattern to begin the extended
period on Friday as the previous trough quickly progresses eastward
into the Rockies and a transient shortwave ridge moves overhead.
This’ll lead to a brief reprieve from wintry weather Friday
afternoon outside of the Cascade crests as lingering light snow over
the eastern Mountains comes to an end. The focus then shifts to a
robust, vertically stacked low pressure system dropping down the
coastline late Friday into Friday night and Saturday. Snow in the
Cascades likely increases late Friday into Friday evening as a warm-
frontal boundary on the southeastern periphery of the upper-low
moves into the CWA. Both GEFS and ECMWF ensemble means paint similar
pictures in the overall progression of precipitation headed into
Saturday morning, with a chance for light snow bleeding into
portions of the Columbia Basin, central Oregon, and the eastern
Mountains. However, viewing individual ensemble members, the
ensemble cluster analysis, and deterministic guidance suggests
moderate to high uncertainty in precipitation/snowfall coverage,
amounts, and timing outside of the Cascades. This appears to be the
result of models struggling resolve the inland penetration and
orientation of the associated moisture plume, weak wave features
rotating around the upper-low, and the lows longitudinal placement.
Changes in these aforementioned features may drastically shift QPF
and thus snowfall impacts, best highlighted between the differences
in the 12z ECMWF and GFS deterministic runs. Should the low pressure
remain further offshore than currently predicted as suggested by
roughly 22% of the grand ensemble members, and in some ways the
ECMWF deterministic, QPF would stay pinned closer to the Cascades
through Saturday resulting in lesser impacts spilling eastward. On
the flip side, a progression closer to the coastline than
projected(23% of the the grand ensemble members) snowfall impacts
would extend further inland throughout much of the CWA. The forecast
was nudged towards the ECMWF ensemble and GEFS means which best
capture the most likely scenario moving through Saturday night; a
blend somewhere between the two outcomes discussed above.
On Sunday the closed upper-level low will have likely morphed into a
long-wave trough feature extending southward into California while
lingering light snow over the Oregon Cascades, eastern Mountains,
and central Oregon decreases. What occurs with the progression of
the large scale pattern past this point hinges on the speed at which
the long-wave trough axis in California moves eastward, and the
placement of a ridge of high pressure amplifying over the eastern
Pacific. These both help to steer a shortwave trough and
accompanying arctic frontal boundary dropping southward through
British Columbia towards northern Washington. The Ensemble Cluster
Analysis reveals a wide range of potential outcomes manifesting in a
huge 10-15 degree temperature spread between the 25th and 75th
percentiles in the NBM ensemble for locations around the region late
in period. Low confidence in the forecast past Sunday. Should the
shortwave trough dropping southward take a more westward track,
snowfall and very cold temperatures may follow late Monday into
Tuesday. Otherwise, northwest flow will keep a slight chance for
snow showers pinned to the mountainous terrain into the middle of
next week should it progress closer towards the Rockies. Schuldt/99
&&
.AVIATION...00Z TAFs...A weather disturbance moving through the
region spreads snow and deteriorating conditions to YKM and DLS
late this afternoon and evening with moderate periods of snow,
particularly for YKM, dropping CIGs/VSBYs to IFR at times. Lower
confidence in RDM/BDN and PDT/ALW overnight where downslope winds
should help to decrease precipitation chances. These
aforementioned locations see a better chance for precipitation
later tomorrow morning into the afternoon as a frontal boundary
sags into the area. PSC may see some light snow later this evening
towards midnight as well, then a second round returns Wednesday
morning turning to rain approaching midday; MVFR CIGs. Winds
increase to 10-20 kts along the foothills and Central Oregon this
evening and overnight. 99
&&
.PRELIMINARY POINT TEMPS/POPS...
PDT 28 43 29 36 / 40 70 50 40
ALW 28 42 31 36 / 50 80 60 40
PSC 27 41 30 35 / 60 60 30 20
YKM 20 36 19 34 / 90 60 20 10
HRI 29 44 30 37 / 40 70 40 30
ELN 18 35 19 32 / 100 60 30 10
RDM 29 44 25 35 / 40 70 70 50
LGD 24 36 28 35 / 60 70 80 70
GCD 24 41 28 36 / 70 50 80 70
DLS 30 44 28 40 / 90 90 70 50
&&
.PDT WATCHES/WARNINGS/ADVISORIES...
OR...Winter Storm Warning from 1 AM Wednesday to 4 PM PST Thursday
for ORZ502.
Winter Storm Warning from 4 AM Wednesday to 4 PM PST Thursday
for ORZ509.
WA...Winter Storm Warning from 1 AM Wednesday to 4 PM PST Thursday
for WAZ030.
Winter Storm Warning until 1 PM PST Wednesday for WAZ026.
Winter Storm Warning until 4 PM PST Wednesday for WAZ520.
Winter Weather Advisory until 4 PM PST Wednesday for WAZ521.
&&
SHORT TERM...87
LONG TERM....99
AVIATION...99The national radar mosaic for the moment the first event began.
1 high wind. Local standard time, as filed.
The Mesonet station AS881 measured a gust of 66mph at 0200PDT on November 30th and the Mesonet station OD184 measured a gust of 65mph at 0537PDT on November 30th.
After NWS Directive 10-1605, the rules offices file Storm Data by.
Every storm in Oregon in 2022Every state in 2022This day in weather historyWarnings in Oregon, November 2022
NOAA National Centers for Environmental Information, Storm Events Database, compiled from the National Weather Service’s monthly Storm Data. Complete through 2026-06; NCEI adds each month about 75 days after it ends and revises past years a few times a year. Rebuilt 2026-09-24. Each event’s entry at NCEI: 1067515.