A shortwave diving down northwest flow aloft combined with increasing moisture transport from the west resulted in heavy snow accumulations along the east slopes of the Washington Cascades overnight Dec. 19th through the evening of the 20th.
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 shortwave diving down northwest flow aloft combined with increasing moisture transport from the west resulted in heavy snow accumulations along the east slopes of the Washington Cascades overnight Dec. 19th through the evening of the 20th.
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 19, 8:59 PM PST, 1 hour 1 minute earlier.
Area Forecast Discussion
National Weather Service Pendleton OR
859 PM PST Mon Dec 19 2022
.EVENING UPDATE...A Winter Weather Advisory has been issued across
the Northern Blue Mountain of Oregon and Washington through 4 AM
PST, as persistent light snow has been occurring in the area over
the last several hours and additional snowfall is expected
tonight. Current radar imagery is showing an additional snow band
traveling through the Eastern Gorge, which has already blanketed
I-84 with light accumulations on the roadway via area webcams.
This band is likely to intensify as it reaches the Blue Mountain
foothills via upslope/orographic lifting, keeping snow showers in
the area over the next several hours. Additional amounts of 1 to 2
inches will be possible.
The remainder of the forecast is still on track, with persistent
snowfall expected over the Washington Cascades through Tuesday
afternoon, Oregon Cascades Tuesday afternoon through the evening,
and the Blue Mountains Tuesday afternoon through Tuesday night.
Thus, multiple winter weather highlights have been issued for the
aforementioned areas that extend through the early morning hours
on Wednesday. Edits to temperatures, winds, and snow amounts
(along the Blue Mountain Foothills) were conducted with this
evening's forecast update to reflect current observations and
recent guidance. 75
&&
.PREV DISCUSSION... /issued 229 PM PST Mon Dec 19 2022/
SHORT TERM...Tonight through Tuesday...A west to northwest flow
aloft continues over the region tonight as a very cold upper level
trough remains over southern Canada. There will be some spotty light
precipitation in the form of snow over the northern portion of the
forecast area overnight. A shortwave dropping down the back side of
the trough overnight will tap into some moisture in the westerly
flow and move it into the forecast area late tonight and Tuesday.
This will begin to increase snow in the Washington Cascades after
midnight and continue through the day then tapering off Tuesday
evening. The winter storm watch has been upgraded to a warning for
the east slopes of the Washington Cascades with a foot or more along
the crest then decreasing amounts further east away from the crest.
This moisture will move into the mountains of NE Oregon and SE
Washington during the day Tuesday. This will provide the northern
Blues with some snow into early Wednesday with warnings amounts of
snow expected so a winter storm has been issued. The foothills of
the Blue mountains will also see some snow late Tuesday and
overnight but just expecting advisory amounts of snowfall. This
system will also usher in some much colder air into the region late
Tuesday. There is some warmer air aloft over Oregon Tuesday which
could combine with the cold air in the Lower Columbia Basin of
northern Oregon to produce some freezing rain potential in the
afternoon and evening. Confidence of this is low and expected
amounts are minimal at this time but needs to be monitored.
LONG TERM...Wednesday through Friday...A myriad of impacts are
expected through the holiday weekend as everything from frigid
temperatures to rain is in store for the forecast area. Ensemble
guidance in pretty good agreement on the overall synoptic pattern
during the period, but how well the models resolve the mesoscale
processes following Thursday and Friday morning's extreme cold is to
be seen, as warm air surging into the forecast area above a strong
cold pool heading into the weekend could complicate the
precipitation forecast.
Confidence is high (>80%) in bitterly cold temperatures across the
forecast area lasting through much of the day Friday, with the
coldest temperatures expected Thursday morning. Temperature
ensembles have come down dramatically over the last 24 hours,
supporting widespread subzero lows in the Basin, while lows waver
around zero for central OR and the John Day Valley. Have issued a
Wind Chill Advisory from Wednesday night through Friday morning due
to strong model consensus, as well as the timing around the holiday
weekend. While we're not currently anticipating widespread record
low temperatures, caution is encouraged for those who plan to be out
and about in these cold temperatures, especially Thursday, making
sure that friends, family, and neighbors who may be especially
vulnerable to the cold are taking steps to bundle up.
Focus then shifts to a shortwave looking to impact the forecast area
from late Thursday night into Friday, before ridging sets up through
the remainder of the period. Guidance not too bullish on QPF with
this system, but feeling relatively confident (>50%) that despite
the uptick in winds and potential mixing through the boundary layer,
the majority of the forecast area will see primarily snow, with
warmer conditions expected to be limited to the west side of the
Cascades. Confidence decreases (30-40%) closer to the east slopes of
the Cascades, particularly for central OR and the Gorge where
warming will be a bit more robust, but thinking that cold conditions
will be prevalent ahead of the system and that models may be
overmixing the cold air.
Precip type concerns amplify over Christmas weekend, however, as
models depict a dirty ridge overhead that will work to warm us up
closer to seasonable temperatures, but with the cold pool likely to
be stubborn to mix out, the presence of warm air aloft and cold
temperatures at the surface may make for a tricky precip forecast
over the holidays. Models are aggressive in depicting ice, but with
how far out the forecast is, want to be a little more cautious and
stick with a mixed forecast for the lower elevations rather than
advertise any widespread freezing rain, especially around Christmas.
We do encourage everyone with travel plans for the holidays to
monitor the latest forecast updates, as we expect lots of changes in
the messaging to occur for this high travel period over the coming
days. Evans/74
AVIATION...Low clouds continue to prevail for PSC/YKM,
while PDT and ALW see spurts of light snow showers due to an
oncoming weather system expected to bring more impactful snow for
the aforementioned areas by late Tuesday. Primarily MVFR to VFR
conditions expected, with cigs possibly lowering to IFR at sites
within the Basin and DLS overnight heading into Tuesday morning.
BDN/RDM should remain VFR through the entire period. Evans/74
&&
.PRELIMINARY POINT TEMPS/POPS...
PDT 26 18 33 15 / 20 40 20 60
ALW 21 18 28 13 / 20 60 40 70
PSC 19 16 21 11 / 10 30 20 30
YKM 21 12 20 6 / 10 20 40 20
HRI 23 18 28 16 / 10 30 20 40
ELN 14 8 15 4 / 10 30 50 30
RDM 34 18 39 27 / 10 0 20 20
LGD 24 24 37 21 / 20 50 30 70
GCD 30 25 38 28 / 20 10 20 50
DLS 38 25 37 26 / 20 40 50 50
&&
.PDT WATCHES/WARNINGS/ADVISORIES...
OR...Wind Chill Advisory from 10 PM Wednesday to 10 AM PST Friday for
ORZ041-044-049-050-505-507-508-510-511.
Winter Storm Warning from 4 AM Tuesday to 10 AM PST Wednesday
for ORZ502.
Winter Weather Advisory until 4 AM PST Tuesday for ORZ507.
Winter Weather Advisory from 4 PM Tuesday to 10 AM PST Wednesday
for ORZ507.
WA...Wind Chill Advisory from 10 PM Wednesday to 10 AM PST Friday for
WAZ024-026>029-521.
Winter Storm Warning from 4 AM Tuesday to 10 AM PST Wednesday
for WAZ030.
Winter Weather Advisory until 4 AM PST Tuesday for WAZ029.
Winter Weather Advisory from 4 PM Tuesday to 10 AM PST Wednesday
for WAZ029.
Winter Storm Warning until 4 AM PST Wednesday for WAZ520.
&&
UPDATE...75
SHORT TERM...91
LONG TERM....74
AVIATION...741 heavy snow. Local standard time, as filed.
The Bumping Ridge Snotel station reported 12 inches of new snow in a 13 hour period ending at 1200 PST on Dec. 20th. The Washington Department of Highways reported 15 inches of new snow in a 25 hour period ending at 1817 PST on Dec. 20th.
After NWS Directive 10-1605, the rules offices file Storm Data by.
Every storm in Washington in 2022Every state in 2022This day in weather historyWarnings in Washington, 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: 1073265.