A series of winter weather systems impacted the Pacific Northwest between December 1st through the 3rd. While the systems moving through were fairly quick, they were able to produce heavy snow accumulations across many of the mountain zones across the forecast area.
Every event with a place to put it; 4 filed by county or forecast zone are drawn at its center, in a lighter ring. Tap one for its entry below.
Deaths and injuries are direct and indirect together, as the offices filed them. Damage is property and crops in the dollars of the year, not adjusted for inflation, and only where an office estimated it.
The episode as NWS PDT wrote it up.
A series of winter weather systems impacted the Pacific Northwest between December 1st through the 3rd. While the systems moving through were fairly quick, they were able to produce heavy snow accumulations across many of the mountain zones across the forecast area.
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 Dec 1, 3:37 AM PST, 23 minutes earlier.
Area Forecast Discussion
National Weather Service Pendleton OR
337 AM PST Fri Dec 1 2023
.SHORT TERM...Today through Sunday...The first in a prolonged
series of upper weather systems has exit the region this early
morning, while a northwest flow aloft has setup behind this
system. Earlier in the evening, this system brought light snow
with accumulations generally around an inch or less in the lower
elevations, while reports of an inch to 3 inches have been noted
in mountain zones. Areas of snow induced patchy fog have also
developed along the Blue Mountain foothills, Yakima/Kittitas
valleys, and the Columbia Basin.
Radar imagery along the PacNW coast shows the next shortwave
trough in northwest flow aloft fast approaching the region this
morning. The main band of precipitation will quickly move across
the forecast area and exit by the afternoon. This shortwave trough
is expected to start the process of increasing snow levels from
southwest to northeast, as well as begin to scour out the colder
airmass that has settled in the Columbia Basin and the adjacent
valleys. Light to moderate snow in the lower elevations will be
possible at onset of precipitation this morning, but as the day
progresses toward the afternoon, the expectation is for
precipitation to become a wintry mix with isolated pockets of
just rain along the southern and eastern fringes of the Lower
Columbia Basin as well as in north central OR. That said, CAMS are
indicating that stubborn pocket of cold air in the eastern Gorge
will allow for a slight chance of light freezing rain for a couple
hours before 10AM. Otherwise, moderate to heavy snow will be
possible in the Cascades, Northern Blues, and Wallowas while light
to moderate snow will be possible in the eastern mountains. After
the main band of precipitation passes through the lower
elevations, breezy west to southwest winds will develop and help
to continue scouring out the colder airmass near the surface in
the lower elevations.
Early tomorrow, the next more potent shortwave trough is expected
to dive southeast across the PacNW bringing with it more
precipitation and stronger winds area-wide. Ahead of this system
arrival, however, winds around 850mb are expected to take on a
more southerly component and push a more mild airmass into the
intermountain PacNW. The expectation is for snow levels to rise to
above 3kft to 3.5kft later tonight, resulting in mostly rain or a
rain dominant rain/snow mix at onset of precipitation. As the day
progresses, snow levels will still be between 3kft to 3.5kft
across the northern half of the forecast area, with an increasing
gradient to 5.5kft moving towards the southern edge of the
forecast area (central OR and Ochoco-John Day Highlands). This
will result in mostly rain across the lower elevations tomorrow,
while moderate to heavy snow continues in the mountains. West to
southwest winds will increase quite a bit area-wide early tomorrow
morning, with sustained winds of 25-35mph and gusts between
45-50mph expected to develop in the Oregon Columbia Basin, along
the Blue Mountain foothills up to Dayton, and across the higher
ridges in the Cascades. Elsewhere in the lower elevations,
sustained winds will generally be 15-25mph with gusts 30-45mph
possible as well. Winds will weaken overnight Saturday, except for
areas of central OR and the eastern mountains where breezy south
winds will continue through the overnight hours.
By early Sunday morning, flow aloft will have become more zonal
while a potent warm front will arrive to the PacNW with yet
another round of heavy mountain precipitation. With south to
southwest winds at 850mb continuing in the overnight hours as well
as the expected arrival of the warm front in the morning, snow
levels will quickly rise to above 6kft to 7kft across the forecast
area, resulting in precipitation falling as mostly rain outside of
the higher peaks in the Cascades and Wallowas. By Sunday
afternoon, area rivers and streams will begin to respond to the
moderate to heavy rain on the newly established snowpack, with
rises anticipated through early next week. As a result, area
stream and river flooding will begin to be a concern through the
middle of next week, though at this time current forecasts keep
rivers within bankfull towards the end of next week. Will continue
to monitor river forecasts in case river flooding highlights will
be needed. Otherwise, breezy west to southwest winds will
redevelop across the lower elevations Sunday morning through the
afternoon, though winds will be generally be 15-25mph with gusts
30-40mph possible in the lower elevations.
While snow is expected again in the lower elevations today, model
guidance advertises less than 15% chances of exceeding 1 inch of
snow accumulations through this afternoon. Turning our attention
to the mountains over the next 48 hours, the chance of exceeding
12/18 inches of snowfall in the northern Blues, Wallowas, and
Cascade east slopes are >90%/60-75% respectively. For the same
period in the southern Blues and Ochoco-John Day Highlands, the
probabilities of exceeding 6 inches is generally 40-60%, though
the higher peaks above 5kft in eastern Grant county and southwest
Union county will see a 60-80% chance of exceeding 10 inches of
snowfall. Lawhorn/82
.LONG TERM...Monday through Friday....Latest GEFS and EC
ensembles are in good agreement on the 500 mb height pattern through
the extended period. An upper ridge will build northward across the
region on Monday which will result in a surge of warmer air and
higher snow levels (rising to 9000 feet MSL) which will result in
all precipitation falling as rain. Latest GEFS and EPS show a weak
atmospheric river extending into the inland Northwest from Monday
into Wednesday which will result in moderate to heavy QPF. NBM 50th
percentile QPF for the 72 hour period ending 12Z Wednesday range
from .25-.50 inches in the lower elevations...1.5-2.0 inches in the
Blue Mountains and 3-5 inches along the Cascade crest of Oregon and
Washington. Hydrologic conditions will have to be monitored next
week as the rain falls on the heavy snow that is expected over the
next 24 hours. Most of the rivers are running fairly low at the
present time, but the current RFC forecast shows the Naches River
getting close to bankfull on Wednesday.
On Monday into Tuesday a southeasterly pressure gradient is forecast
to set up across eastern Oregon and extreme southeast Washington.
The NBM deterministic is not showing particularly strong winds but
pattern recognition would suggest that stronger winds would be
possible along the base of the Blues and the Grande Ronde Valley.
For this forecast increased the winds to the 90th percentile NBM
values to reflect the potential for stronger winds.
On Thursday into Friday 500 mb heights begin to lower as a shortwave
trough moves across the region. Snow levels will lower but as this
occurs, QPF will be lighter. Precipitable water decreases to near
normal compared to 150-200 percent of normal earlier in the week. By
Friday afternoon/evening POPS will be down to 25-40 percent in the
mountains and 10-20 percent in the lowlands. At that time snow
levels will be 2000-3000 feet.
&&
.AVIATION...12Z TAFs...A band of light to locally
moderate snow snow will move quickly across the region this morning
and exit KALW and KPDT around midday. This will cause IFR/LIFR
conditions except at KBDN and KRDM where mostly MVFR conditions are
expected. Afterward winds will pick up a bit especially at
KPDT...KRDM and KBDN where 20-25 kt gusts are expected. This will
aid in improving vsbys to mostly VFR by late this afternoon. By this
evening CIGS will become VFR at 035-050 feet AGL with mid clouds
above. 78
&&
.PRELIMINARY POINT TEMPS/POPS...
PDT 41 35 46 39 / 80 50 80 90
ALW 40 34 47 40 / 90 70 90 80
PSC 39 32 51 42 / 90 40 50 70
YKM 37 25 47 32 / 90 40 60 70
HRI 43 35 50 41 / 90 40 60 80
ELN 35 26 42 30 / 90 60 70 60
RDM 42 30 47 38 / 80 30 70 90
LGD 40 30 42 34 / 90 80 100 90
GCD 39 29 43 36 / 90 60 90 100
DLS 46 37 48 42 / 90 70 90 90
&&
.PDT WATCHES/WARNINGS/ADVISORIES...
OR...Wind Advisory from 4 AM to 6 PM PST Saturday for ORZ044-507-508.
Winter Storm Warning until 10 AM PST Sunday for ORZ502.
Winter Weather Advisory until 4 AM PST Sunday for ORZ503-506.
Winter Weather Advisory until 4 AM PST early this morning for
ORZ509.
Winter Storm Warning until 4 PM PST Saturday for ORZ509.
WA...Wind Advisory from 4 AM to 6 PM PST Saturday for WAZ029.
Winter Storm Warning until 10 AM PST Sunday for WAZ030.
Winter Storm Warning until 10 AM PST Sunday for WAZ522.
Winter Storm Warning until 4 AM PST Sunday for WAZ523.
&&
SHORT TERM...82
LONG TERM....78
AVIATION...78Preliminary Local Storm Report
National Weather Service Pendleton OR
1015 PM PST Thu Nov 30 2023
..TIME... ...EVENT... ...CITY LOCATION... ...LAT.LON...
..DATE... ....MAG.... ..COUNTY LOCATION..ST.. ...SOURCE....
..REMARKS..
0800 PM Snow 11 ESE Lonerock 45.05N 119.67W
11/30/2023 E2.0 inch Morrow OR Dept of Highways
2 inches of snow since 4 pm. elevation 4000
feet.
&&Preliminary Local Storm Report
National Weather Service Pendleton OR
1018 PM PST Thu Nov 30 2023
..TIME... ...EVENT... ...CITY LOCATION... ...LAT.LON...
..DATE... ....MAG.... ..COUNTY LOCATION..ST.. ...SOURCE....
..REMARKS..
1000 PM Snow 2 NW Pendleton 45.70N 118.86W
11/30/2023 M1.3 inch Umatilla OR Official NWS Obs
1.3 inches of snow since 6 pm. elevation
1492 ft.
&&Preliminary Local Storm Report
National Weather Service Pendleton OR
1024 PM PST Thu Nov 30 2023
..TIME... ...EVENT... ...CITY LOCATION... ...LAT.LON...
..DATE... ....MAG.... ..COUNTY LOCATION..ST.. ...SOURCE....
..REMARKS..
0700 PM Snow 9 NW Seneca 44.24N 119.09W
11/30/2023 E1.5 inch Grant OR Public
1.5 inches of new snow since 5 pm. Elevation
4800 ft. Social media report.
&&The national radar mosaic for the moment the first event began.
4 heavy snow. Local standard time, as filed.
The Lake Creek R.S. SNOTEL measured 8 inches of new snow in a 48 hour period ending 3am PST Dec. 3rd. The Starr Ridge SNOTEL measured 7 inches of new snow in a 48 hour period ending 3am Dec. 3rd.
The Gold Center SNOTEL site measured 10 inches of new snow in a 48 hour period ending at 3AM PST Dec. 3rd. The Beaver reservoir SNOTEL site measured 7 inches of new snow in a 48 hour period ending 3AM PST Dec. 3rd.
The Milk Shakes SNOTEL site measured 16 inches of new snow in a 24 hour period ending 8AM PST on Dec. 2nd. The Tollgate Crossing store in Tollgate, OR reported 12 inches of new snow fell overnight at 9:34AM PST on Dec. 2nd.
The Hogg Pass SNOTEL measured 11 inhces of new snow in a 24 hour period ending at 3AM PST on Dec. 2nd.
After NWS Directive 10-1605, the rules offices file Storm Data by.
Every storm in Oregon in 2023Every state in 2023This day in weather historyWarnings in Oregon, December 2023
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: 1154011, 1154012, 1154013, 1154017.