An approaching upper-level trough in combination with an ridge of high pressure to the east of the CWA facilitated a tight pressure gradient and strong down-sloping winds over the Blue Mountains.
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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.
An approaching upper-level trough in combination with an ridge of high pressure to the east of the CWA facilitated a tight pressure gradient and strong down-sloping winds over the Blue Mountains.
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 Jan 4, 9:40 AM PST, 1 hour 20 minutes earlier.
Area Forecast Discussion
National Weather Service Pendleton OR
940 AM PST Wed Jan 4 2023
.UPDATED AVIATION DISCUSSION...18Z TAFs...Only KPDT and KBDN are
currently VFR while KDLS/KRDM/KYKM/KPSC are MVFR and KALW is
LIFR. VIS is being affected by fog and freezing fog, especially
along the foothills of the Blue mountains and is slowly making its
way into Central Or. CIGs are ranging from VFR to mostly MVFR and
will remain as such through the period. Winds will be mostly
light through the period until 01Z when Central Or TAF sites will
see a southerly wind with gusts to 30kts as the next system moves
overhead. This round will also provide rain/snow showers for all
TAF sites after 20Z with the exception of KPSC and KPDT, which
should stay dry as the system dissipates. 90
&&
.PREV DISCUSSION... /issued 920 AM PST Wed Jan 4 2023/
MORNING UPDATE...A strong closed low is currently located off the
southern Oregon coast this morning. Clouds are moving into central
Oregon and radar shows precipitation moving into southwestern
Oregon. Still anticipating light snow to move into central Oregon
later this morning turning to a rain/snow mix this afternoon
while areas further north and east will see snow. Tonight will see
a rain/snow mix over much of the area though light amounts of
freezing rain will be possible from the eastern Columbia Gorge
northward through the Simcoe Highlands into the WA Cascades and
the Yakima and Kittitas Valleys. Might also see a hundredth of an
inch or two of freezing rain in the lower valleys of north central
Oregon and the southern Blue Mountain Foothills but at this time,
it looks like too little to be a significant issue given some
expected light snow as well. Latest runs of the NBM QPF and WPC
Guidance QPF have trended towards significantly lighter
precipitation amounts over most of the area with a sharper cut
off of precipitation this evening. However, QPF amounts haven't
changed much in the areas already having Winter Weather
Advisories, so do not see snow and freezing rain amounts changing
much there.
Pressure gradients are tightening and winds are already
increasing in the Grande Ronde Valley and along the base of the
Blue Mountains in the Blue Mountain Foothills. The NBM 4.1 shows
an area of gusts to 50 to 60 mph from Cabbage Hill along the base
of the Blue Mountains to near Walla Walla. Will be assessing
whether to upgrade the current wind advisory to a high wind
warning. Current forecast was in good shape and only made a few
minor changes to temperatures and winds. Forecast update already
out. Perry/83
PREV DISCUSSION... /issued 355 AM PST Wed Jan 4 2023/
Updated Aviation Discussion.
SHORT TERM...Today through Friday night...The next system to
arrive to the forecast area late this afternoon and tonight poses
several concerns, and winter weather advisories and wind
advisories will be issued for the morning package. For now, a
decaying shortwave has done little in precipitation since
midnight, but WSR-88D is detecting a few weak returns over the
Lower Columbia Basin. KYKM is showing -SN in the latest
observation, and Dual Pol from WSR-88D indicates precipitation
type as light snow compared to any freezing drizzle.
The remainder of the morning will be quiet, then precipitation
associated with a deep closed low off the eastern Pacific will
spread from the north during the afternoon and evening hours. By
00Z, the center of the low will be about 450 miles west of Port
Orford, then the low will travel north along the OR/WA coast
tonight and Thursday morning. The front will arrive as a warm
front, but no strong warm air advection or significant subtropical
moisture tap is associated with it. However, confidence has
increased that a wintry mix of snow and freezing rain will occur
in the colder valleys of south central WA and north central OR.
HREF shows precipitation type as a mixture of snow and freezing
rain, including the Lower Columbia Basin. The Conditional
Probability of freezing rain from the NBM is around 60-80 pct for
the Lower Columbia Basin. Despite the high conditional
probabilities, overnight low in the Basin will be near the
freezing mark and the road temperatures may even be above freezing
and too warm for ice to form. The Winter Weather Advisories will
be focused for the east slopes of the southern WA Cascades (mainly
south of HWY 12), the Simcoe Highlands, the Kittitas and Yakima
Valleys, and the eastern Columbia River Gorge tonight through
Thursday morning. Snow amounts will be on the low end of the
advisory criteria, but there will also be the chance (50-60 pct)
of light freezing rain with ice accumulations from a glaze to a
tenth of an inch.
Winds through the Grande Ronde Valley and the base of the Blue
Mountains east-southeast of Pendleton and Milton-Freewater will be
increasing during the day, and wind advisories will be issued due
to south-southeast winds gusting to 45-55 mph. The ECMWF EFI
continues to show the foothills as unusually high winds with a
value of 0.8 out of 1.0. However, the surface gradient from ONO-
MEH may only peak out at 7 mb this evening based on deterministic
models which is strong but not a critical gradient.
Although the warm front brings a variety of winter weather
concerns, the impacts are primarily in our western zones. The
eastern mountains and valleys as well as central OR will only
observe less than an inch of new snow for most locations. The
front will lift north out of the forecast area Thursday, but the
upper flow will remain from the south. The deep vertically stacked
low will be off the southern BC coast Thursday night and will
send a series of embedded waves across the forecast area. The
mountains will have scattered snow showers with snow levels around
3500-400 feet, and the rest of the area will have a 10-20 pct
chance of rain or rain/snow mix. I can not rule out localized
light freezing rain Thursday night and Friday night over some of
the colder valleys east of the WA Cascades. Wister/85
LONG TERM......SATURDAY THROUGH WEDNESDAY...The extended period is
characterized by a rather active period with persistent southwest
flow aloft, keeping conditions warmer and wetter as multiple
shortwaves allow for daily mountain snow over the Cascades, Blue
Mountain, and Wallowas. This will also result in temperatures that
are 5 to 10 degrees warmer than normal, with highs peaking in the
mid to upper 40s and lows in the mid 30s across lower elevations of
the Basin and through Central Oregon. The other sensible weather
concern that arises through the period is related to breezy
conditions for Central Oregon, Blue Mountains, and the Grande Ronde
Valley that peak Saturday night through Sunday afternoon before
returning again Monday night through Tuesday. Peak wind gusts of 25
to 35 mph from the south will be possible during both timeframes.
An upper level ridge sets up just to our east late Friday into
Saturday, which will linger through the weekend before flattening
and shifting east into the Central Plains Sunday into Monday. This
ridge will help to deflect and weaken an incoming weak shortwave on
Saturday and an upper level trough on Sunday. The weak shortwave on
Saturday will produce mountain snow showers primarily along the
Washington Cascades early Saturday morning before incorporating the
east slopes, Kittitas/Yakima Valleys, Goldendale/Bickleton area, and
the Oregon Cascades by the afternoon. Trapped cold air along the
east slopes of the Washington Cascades and the Yakima/Kittitas
Valleys will attribute to snow levels between 2000-3000 feet, with
snow levels elsewhere between 3500-4500 feet due to the southwest
flow aloft advecting a warmer marine airmass into the region. 1 to 4
inches of snowfall is expected along the Washington Cascades and
east slopes through the day on Saturday, with less than an inch
likely for Yakima/Kittitas Valleys, Goldendale/Bickleton area, and
along the Oregon Cascades and eastern mountains. A reinforcing upper
level trough will be following closely behind the earlier shortwave
on Sunday, but again will be dissipating as it moves onshore and
into the Interior Pacific Northwest. A slight chance (15-20%) of
lower elevation rain is possible Saturday night into Sunday morning,
but confidence is high (80%) that amounts will stay minimal and
below 0.1 inch. A substantial pressure gradient will develop as the
incoming upper level trough moves onshore and interacts with the
upper level ridge to our east. This, coupled with southerly,
downsloping winds, will produce elevated winds through Central
Oregon, Blue Mountains/Foothills, John-day/Ochoco Highlands, and the
Grande Ronde Valley with gusts of 25-35 mph possible. Confidence in
these values are moderate to high (70-80%) as ECMWF EFI highlights
these areas as incurring above climatologically normal wind gusts.
These southerly winds will also attribute to upslope snowfall along
the east slopes of the Washington Cascades, allowing amounts of 1-2
inches of snowfall on Sunday. Southwest flow aloft continues into
the workweek as an upper level trough begins to dig as it approaches
the Pacific Northwest coast into Tuesday. A weak shortwave moves
across our area ahead of the larger, parent system on Monday,
allowing for light snowfall to continue along the Cascades.
Precipitation chances begin to extend into lower elevations of
Central Oregon Monday evening before encompassing our entire area
overnight into the early morning hours on Tuesday as the trough
moves through the region. Rain amounts of less than 0.10 inch are
expected for lower elevations of the Basin. Snow levels will still
be hovering in the 1500-2500 foot range along the east slopes of the
Washington Cascades and the Yakima/Kittitas Valleys, but will be
between 3500-4500 feet elsewhere Monday and Tuesday. Snow amounts of
2 to 5 inches will be possible along the east slopes of the
Cascades, with around an inch for Yakima/Kittitas Valleys, Blues,
and Wallowas.
Guidance is in good agreement with the overall weather pattern, with
differences arising regarding trough/shortwave strength and path
with Monday/Tuesday's system. The GFS incurs stronger
trough/shortwave strength than the ECMWF, which correlates to a
windier and wetter scenario. This is observed via the 500mb EOF
Patterns which highlight these discrepancies with shortwave
strength. The cluster phase space shows a shift in confidence from
the GFS Saturday and Sunday to the ECMWF Monday onward, which is
based on the overall spread and deterministic representation of the
ensembles. Thus, there is moderately high (70-80%) confidence for
wind and rain/snow values over the weekend, but confidence drops to
moderate (40-60%) Monday onward. 75
AVIATION...12Z TAFS...Variable conditions across all sites, with
VFR at RDM/BDN, MVFR at DLS/YKM, IFR at PDT, and LIFR at ALW/PSC due
to reduced ceilings of OVC002. These conditions look to persist
through the morning hours with slight improvement through the
afternoon with all sites reaching VFR conditions with the exception
of ALW/YKM/DLS, which will stay in MVFR through the period. Winds
will be picking up out of the south for RDM/BDN through the
afternoon associated with a passing shortwave. This wave will also
provide rain/snow showers for all taf sites after 21Z with the
exception of PSC, which should stay dry as the wave dissipates.
There is also a potential for -SN to transition to -FZRA around 07Z
for YKM. 75
&&
.PRELIMINARY POINT TEMPS/POPS...
PDT 40 33 47 36 / 10 40 10 10
ALW 40 32 50 38 / 10 30 10 10
PSC 38 31 43 33 / 10 40 20 10
YKM 34 28 38 28 / 10 70 60 30
HRI 37 31 44 33 / 10 50 10 10
ELN 31 25 36 27 / 10 70 50 30
RDM 40 34 48 33 / 50 30 10 20
LGD 35 32 41 34 / 10 40 20 20
GCD 38 33 44 33 / 20 40 20 10
DLS 38 32 42 36 / 40 90 40 40
&&
.PDT WATCHES/WARNINGS/ADVISORIES...
OR...Winter Weather Advisory from 7 PM this evening to 4 AM PST
Thursday for ORZ041.
Wind Advisory until 6 PM PST Thursday for ORZ049.
Wind Advisory from 3 PM this afternoon to 6 PM PST Thursday for
ORZ507.
Freezing Fog Advisory until 10 AM PST this morning for ORZ510.
WA...Winter Weather Advisory from 7 PM this evening to 4 AM PST
Thursday for WAZ024.
Wind Advisory from 3 PM this afternoon to 6 PM PST Thursday for
WAZ029.
Winter Weather Advisory from 4 PM this afternoon to 10 AM PST
Thursday for WAZ026-027-520-521.
&&
SHORT TERM...85
LONG TERM....75
AVIATION...90The national radar mosaic for the moment the first event began.
1 high wind. Local standard time, as filed.
The Mesonet Station OD184 recorded a gust of 76 mph at 0110 AM on January 5th, and the Mesonet Station OA881 recorded a gust of 68 mph at 0545 AM on January 5th.
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, January 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: 1078767.