An upper level trough and cold front passage at the surface produced snow showers across the Cascade and Blue mountain ranges in Oregon and Washington, while a low level jet associated with this winter storm mixed down strong gusts across the Washington Columbia Basin.
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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 upper level trough and cold front passage at the surface produced snow showers across the Cascade and Blue mountain ranges in Oregon and Washington, while a low level jet associated with this winter storm mixed down strong gusts across the Washington Columbia Basin.
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 10, 9:41 PM PST, 19 minutes earlier.
Area Forecast Discussion
National Weather Service Pendleton OR
941 PM PST Fri Dec 10 2021
Updated aviation discussion
.SHORT TERM...Tonight and Saturday...An upper level trough in the
upper Gulf of Alaska has begun to drop southward pushing a cold
front towards the Pacific Northwest. Ahead of the Cold front is a
warm front that is currently impacting Washington and northern
Oregon. This is producing some snow over the Washington Cascades and
east slopes as well as over the northern Blue Mountains of OR and
WA. Snow levels will gradually rise overnight and into Saturday to
3000 to 4000 feet as the warm front passes. The cold front will
arrive into the Washington Cascades Saturday afternoon and then
sweep across the region overnight once again lowering snow levels
and producing some significant snowfall over the mountains through
Sunday morning. Multiple Winter Storm Warnings are in effect for the
mountains. Ahead of the cold front there will be some increasing
southerly winds leading to the issuance earlier today of some wind
advisories.
AVIATION...06Z TAFs...VFR conditions will prevail for most of the
forecast period but there may be brief periods of MVFR CIGS,
especially in areas of light rain. The main aviation concern will
be winds, as winds increase Saturday and will predominantly be WSW
at 15-25 kts gusting to around 35-40 kts through afternoon before
decreasing in the evening. LLWS is forecast for KRDM and KBDN
overnight through early Saturday when SW winds will be considerably
stronger just above the surface.
&&
.PREV DISCUSSION... /issued 254 PM PST Fri Dec 10 2021/
SHORT TERM...Tonight through Sunday...Busy next 48 hours weather
wise as an upper level trough coupled with a surface frontal
system approaches the PacNW from the gulf of Alaska. This
evening, the warm sector associated with this coupled system will
start to move on shore, with snow showers increasing across the WA
Cascades initially, then spreading east and south overnight
tonight across the forecast area. Snow levels under this warm
sector will gradually rise, with a north-south gradient of snow
levels at 3.5kft to 4kft expected by late tomorrow morning. Behind
a cold front passage starting early tomorrow, snow levels will
begin and continue to decrease to 1kft in the WA Cascades and
3.5kft in the northern Blues and OR Cascades. There will be a
moderate moisture plume associated with this coupled system as it
impacts the region through early Sunday morning. Tonight into
early tomorrow morning, the bulk of the moisture will move across
the WA Cascades then the northern Blues and OR Cascades by late
tomorrow morning through tomorrow evening. Snow accumulations
through the duration of this system are expected to be between
12-16 inches around the Tollgate and Ski Bluewood areas in the
northern Blues, as well as near and in the Cascades passes with
higher amounts towards the crests. Winter Storm Warnings have been
issued from this evening through Sunday morning for the WA
Cascades above 2,500ft, the OR Cascades above 4kft, and the OR/WA
northern Blues above 3,500ft for the anticipated snowfall. Across
the lower elevations, expect a chance of light rain, with some
locations along the foothills and higher elevation valleys to see
a rain/snow mix tomorrow morning then snow later in the day. Out
ahead of the cold front passage early tomorrow, breezy to gusty
southerly winds will begin to develop as surface pressure
gradients tighten across the northeast mountains. At times, the
low level jet developing over the inland PacNW will mix down gusty
southerly winds up to 50 mph into the Bend area, as well as along
the Blue Mountain foothills into the OR Lower Columbia Basin, and
through the Grande Ronde Valley tomorrow morning and afternoon.
Wind advisories have been issued for these areas, and will be in
effect from the morning hours into the early evening tomorrow.
Behind the cold front passage and after sunset tomorrow, winds
will gradually decrease into Sunday morning, though locally breezy
conditions will linger through Sunday as surface pressure
gradients will be slow to decrease. Sunday, the aforementioned
upper trough will continue to dig south along the BC coastline out
of the Gulf of Alaska, turning flow aloft to the southwest. This
will push the bulk of any moisture advection to the south of the
region, though lingering upslope snow showers will continue across
the Cascades and portions of the northeast mountains. Any
additional snow accumulations for Sunday will be 1 to 3 inches
across the mountain zones.
Temperatures will increase by about 5 degrees tomorrow afternoon
as the mild airmass under the warm sector moves across the inland
PacNW ahead of the surface cold front. Afternoon high tomorrow
will be in the mid 40s to the mid 50s in the lower elevations,
with 30s in the mountains. By Sunday, the cold air advection
behind the cold front will bring afternoon temperatures back down
into the 30s and 40s. Lawhorn/82
LONG TERM...Monday through Friday...A moist southwest flow aloft
will continue to bring numerous snow showers to the Cascades and the
eastern mountains/valleys on Monday. Snow levels will lower as the
offshore trough nudges towards the coast and spreads deeper cooler
air from the west. While most of the lower elevations will observe
rain, south central WA will have a mixture of rain/snow during the
day. This includes the Yakima and Kittitas Valleys and the Simcoe
Highlands. By 12Z Tuesday, the axis of the trough will be along the
Coastal Range, lowering snow levels down to around 1000-1500 feet
Monday night. Most of central Oregon and the Columbia Basin will
get missed out on the snow accumulations, but there may be some
locations receiving the first measurable snowfall of the season
around 0.5-1.0 inch. The Eagle Caps and Elkhorns could get hit
particularly hard with heavy snow Monday and Monday night, and snow
in the Blue Mountains may be pushing advisory criteria. NBM
Conditional Probability of FZRA indicates around 40 pct for the
Yakima and Kittitas Valleys Monday evening, but forecast soundings
from both the latest GFS and ECMWF indicate a snow profile. Freezing
rain will not be included in the forecast.
The upper trough is progged to move inland Tuesday and Tuesday night
with snow levels down to the Basin floor but also drier air
accompanying the trough. The trough decays as it exits the region
Wednesday morning, and the forecast area may be under a weak
transitory ridge on Wednesday. The latest deterministic models runs
are advertising a deeper low off the coast Wednesday compared to
previous runs and the ensembles. The ensembles also maintain a
cyclonic flow aloft (with some variation in amplitude) over the
PacNW which would suggest continued showers on Wednesday. The GFS
and ECMWF fill the low and push it to the southeast followed by a
drier northwest flow aloft Thursday through Friday. This matches
well with the ensembles, therefore there is a fair degree of
confidence that a brief break in weather can be expected at the end
of the work week. Wister/85
&&
.PRELIMINARY POINT TEMPS/POPS...
PDT 38 56 35 45 / 10 30 50 40
ALW 39 58 38 46 / 30 50 50 40
PSC 42 56 40 47 / 10 10 20 10
YKM 35 53 31 42 / 30 40 40 30
HRI 40 57 37 48 / 10 20 30 20
ELN 32 45 27 38 / 40 50 40 30
RDM 35 49 27 43 / 10 60 60 40
LGD 31 41 30 39 / 20 70 60 60
GCD 33 44 32 38 / 10 60 50 40
DLS 39 52 36 46 / 50 80 70 60
&&
.PDT WATCHES/WARNINGS/ADVISORIES...
OR...Winter Storm Warning until 4 AM PST Sunday for ORZ502-509.
Wind Advisory from 4 AM to 4 PM PST Saturday for ORZ044-049-507-
508-511.
WA...Winter Storm Warning until 4 AM PST Sunday for WAZ030.
Wind Advisory from 4 AM to 4 PM PST Saturday for WAZ029.
Winter Storm Warning until 4 AM PST Sunday for WAZ520.
&&
SHORT TERM...91
LONG TERM....91
AVIATION...91The national radar mosaic for the moment the first event began.
1 heavy snow. Local standard time, as filed.
The COOP Observer SUN03 measured 11 inches of new snow during the snow event period.
After NWS Directive 10-1605, the rules offices file Storm Data by.
Every storm in Oregon in 2021Every state in 2021This day in weather historyWarnings in Oregon, December 2021
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: 1004285.