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 30, 10:02 PM PST, 1 hour 58 minutes earlier.
Area Forecast Discussion
National Weather Service Pendleton OR
1002 PM PST Wed Nov 30 2022
&&
.AVIATION...06Z TAFs...All TAF sites will have a mix of VFR and
MVFR conditions through 18Z tomorrow morning though MVFR is less
likely at KDLS, KPSC and KPDT. KRDM and KBDN could possibly drop
to IFR with snow showers through 10Z tonight but did not have the
confidence to mention this in those TAFs. Light rain and snow is
expected at all sites except KYKM and KPSC. After 18Z,
precipitation will end but BKN-OVC skies will continue with CIGs
rising to 4K-8K feet AGL. South to southwest winds at 10 to 15 kts
will continue at KPDT, KALW and KBDN through around 10Z.
Otherwise, winds will remain below 12 kts for the next 24 hours.
Perry/83
&&
.PREV DISCUSSION... /issued 850 PM PST Wed Nov 30 2022/
EVENING UPDATE...Radar and satellite imagery continue to show
overcast skies across the area with a plume of moisture crossing
from the Oregon Cascades through the eastern mountains and Blue
Mountain Foothills. Heaviest amounts of precipitation has been
rain along the Blue Mountain Foothills with a couple of tenths of
an inch in the last few hours. Snow is continuing in the mountains
and the remaining Winter Storm Warnings for the Oregon Cascade
East Slopes and Northern Blue Mountains and the Winter Weather
Advisory for the Southern Blue Mountains will remain in effect
until tomorrow afternoon. Made some changes to end or greatly
reduce the chances of precipitation in the lower Columbia Basin
and Yakima and Kittitas Valleys. Winds are continuing at 15 to 25
mph with higher gusts in the Grande Ronde Valley so have bumped
winds up there but have a gradual decrease through the night. Made
a few other wind adjustments to better agree with observations.
Overcast skies are expected through the night and with
temperatures still in the mid 30s to lower 40s in the Columbia
Basin, raised lows a few degrees as temperatures are not expected
to drop as low as previously forecast. Made a few other
adjustments as well. Forecast update already out. Perry/83
PREV DISCUSSION... /issued 301 PM PST Wed Nov 30 2022/
SHORT TERM...TODAY THROUGH THURSDAY NIGHT...Current radar and
visible satellite imagery showing mostly cloudy skies as light to
moderate returns continue to stream in through the Lower Columbia
Basin, and across the Blue Mountains and foothills. Multiple
Winter Weather Warnings are currently in effect through Thursday
evening, primarily over the Oregon Cascades and the Northern Blue
Mountains. The Winter Storm Warning currently in effect for the
east slopes of the Washington Cascades will be expiring at 4PM
PST, as snowfall rates are expected to decrease tonight and into
Thursday morning. However, snowfall will still be occurring over
the crest and at pass level, with additional amounts into Thursday
morning staying below 6 inches at pass level. Winter Weather
Advisories are also in effect for the Southern Blue Mountains and
the Simcoe Highlands, with the latter expiring at 4 PM PST. The
Southern Blue Mountains are still anticipated to receive up to 5-6
inches below 5500 feet, so have kept the advisory for the area
through Thursday afternoon. The other weather concern resides in
breezy winds through the John Day- Ochoco Highlands and across the
Blue Mountains as 20 to 30 mph gusts will be possible out of the
southwest. This will provide the ability for blowing snow to occur
in these areas, which could impact travel as decreased
visibilities and drifting snow may occur. High confidence (70-90%)
resides in forecast snow amounts, with the NBM v.4.1 highlighting
a 80-100% chance of exceeding 6 inches along the Southern Blue
Mountains, 70-80% chance of exceeding 6 inches along the Northern
Blue Mountains, and 50-70% chance of exceeding 4 inches over the
Southern Blue Mountains.
These conditions are in response to a strong upper level trough
that continues to drop along the Washington coast tonight before
pushing inland and across our area through the day on Thursday.
This digging trough has tilted positively this morning and will
continue to do so through the evening, which will keep breezy
conditions across Oregon as a pressure gradient has set up
southwest to northeast. These features, coupled with a low level
jet, provides high confidence (70-90%) in breezy winds of 15 to 25
mph occurring along the east slopes of the Cascades, John Day-
Ochoco Highlands, Southern Blue Mountains/foothills, and across
southern/eastern Wallowa county. These winds will begin to subside
through the day Thursday as the upper level trough's axis exits
east by the evening. Precipitation will begin to focus at
elevation along the Cascades, Blues, and Wallowas into Thursday
morning, as a drier airmass advects in from the north via
northerly flow aloft by the afternoon. Temperatures will be 5 to
10 degrees cooler on Thursday, especially at lower elevations of
the Basin with highs peaking into the mid to upper 30s. 75
LONG TERM...FRIDAY THROUGH WEDNESDAY...The beginning of the long
term will be characterized by a transient ridge while the region
sits between two systems. The GFS/ECMWF/NAM12/SREF are showing the
low will be parked off the coast of B.C. ushering in a bit of
moisture up the back edge of the ridge that will affect mainly the
Oregon Cascades (40-60%) while the back end of the system that is to
the east will allow for some precipitation to linger over the
eastern mountains (20-40%). This will also tighten up the gradients
across the mountains and allow for some breezy conditions in Central
OR and downsloping winds to occur along the foothills of the Blues
on Friday (40-60%) due to the S to SW flow aloft. Confidence is
moderate (40-60%) with the positioning and timing as the clusters
and models are in fairly close agreement. NW flow will still be
present and cold air will move into the region. The NBM and
GFS/ECMWF meteograms ensembles are showing high temperatures to be
in the 30s to 40s in the lower elevations and 20s for the higher
terrains. The EFI is showing that the region is still below seasonal
average temperatures for this time of year.
As we head into the weekend, the GFS/ECMWF/NAM and SREF are in
fairly good agreement with the next system digging a bit farther
southward and swinging farther offshore. The positively tilted trough
will actually pull the moisture away from shore only allowing for
the WA Cascades to be affected by any precipitation. By Sunday
models show the low traversing even farther to the south and
allowing the region to be free and clear of any precipitation but
under NW flow again. Temperatures will be around 5 degrees
cooler averaging in the 20s to 30s region wide.
The beginning of the next work week is when the long term becomes a
bit out of sorts. The models are no longer in agreement and are
struggling with the system. The clusters and models are showing a
trough, but are not in agreement on strength, timing or positioning.
The ensembles are also struggling with whether or not the next
system will be wet or dry. As this is days 5 and 6, confidence is
low as to the solution so we will just have to wait to see
how this all shakes out. Bennese/90
&&
.PRELIMINARY POINT TEMPS/POPS...
PDT 30 37 19 36 / 60 20 20 10
ALW 31 37 20 35 / 80 20 30 10
PSC 28 36 20 29 / 30 10 10 10
YKM 16 33 11 26 / 40 10 0 20
HRI 30 39 22 36 / 40 10 10 10
ELN 19 31 11 24 / 50 20 0 10
RDM 25 35 15 37 / 60 20 10 10
LGD 30 36 16 30 / 80 50 30 10
GCD 28 35 14 32 / 70 50 20 10
DLS 32 40 24 39 / 70 40 30 20
&&
.PDT WATCHES/WARNINGS/ADVISORIES...
OR...Winter Storm Warning until 4 PM PST Thursday for ORZ502-509.
Winter Weather Advisory until 4 PM PST Thursday for ORZ503.
WA...Winter Storm Warning until 4 PM PST Thursday for WAZ030.
&&
EVENING UPDATE...83
SHORT TERM...75
LONG TERM....99
AVIATION...83The national radar mosaic for the moment the first event began.
2 heavy snow. Local standard time, as filed.
The Milk Shakes Snotel measured 10 inches of new snow over a 16 hour period ending at 0400 PST on Dec. 1st. A trained spotter in Tollgate measured 2 feet of new snow between 1AM Nov. 30th and 10PM Dec. 1st.
The Hogg Pass Snotel measured 16 inches of new snow in a 29 hour period ending at 0900 on Dec. 1st.
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, December 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: 1071974, 1071975.