A deformation zone formed over Southwest Idaho and Eastern Oregon creating significant instability and resulted in bands of heavy precipitation, including heavy snow, along the Idaho and Oregon border.
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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 BOI wrote it up.
A deformation zone formed over Southwest Idaho and Eastern Oregon creating significant instability and resulted in bands of heavy precipitation, including heavy snow, along the Idaho and Oregon border.
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 Boise, ID wrote its last area forecast discussion before the first event at Jan 12, 3:15 AM MST, 1 hour 45 minutes earlier.
Area Forecast Discussion
National Weather Service Boise ID
315 AM MST Tue Jan 12 2021
.SHORT TERM...Today through Thursday night...A moist system is
pushing into the Intermountain West this morning, with
precipitation moving into southeast Oregon mid- morning and
spilling into southwest Idaho by the afternoon. Most of the
moisture associated with this system will be concentrated over
the northern mountains, with 1 to 2 inches of incoming
precipitable water. Snow levels this morning will start at valley
floors and will rise above 6000-7000 ft by this evening. As warmer
air aloft mixes down during the day, areas in the lower valleys
across southeast Oregon, particularly near Burns and between Baker
and Ontario, will see a slight chance of freezing rain. Steady
precipitation will continue over the northern mountains overnight
into Wednesday, and a passing cold front will bring snow levels
back down to 4000 ft by Wednesday afternoon. Locations across the
Snake River Plain will see mostly rain showers through Wednesday
afternoon, and will see some shadowing at the onset of
precipitation into Idaho today. Breezy winds will accompany this
system, especially south of the Snake River Plain. Models have
increased the moisture content of this atmospheric river event
that will spill into the mountains, so snow totals have been
raised by 1 to 2 inches across the advisory areas. The Upper
Weiser River Basin is now forecast to see snow accumulations of 3
to 7 inches below 4000 ft before the precipitation transitions to
rain, so the advisory for this zone has been upgraded to a Winter
Storm Warning. A cold front will pass through the region on
Wednesday afternoon, ending the precipitation by the late evening.
Patchy valley fog is expected to develop overnight into Thursday
under mostly clear skies. Conditions on Thursday will be dry and
seasonable.
.LONG TERM...Friday through Tuesday...Friday through Tuesday...Light rain and snow showers
Friday and Friday evening as a weak upper trough passes through
from northwest to southeast. Clearing Friday night, then sunny
and cooler Saturday as the next Pacific upper ridge approaches.
Pacific moisture overrunning the ridge will bring a slight chance
of rain and snow late Saturday night and Sunday. Clearing west
to east Sunday evening as the next Pacific upper ridge approaches,
Sunny Monday. Mostly clear and milder Monday night. Partly
cloudy, breezy, and cooler Tuesday as a north Pacific trough
moves inland across northern Idaho.
&&
.AVIATION...VFR with increasing clouds. Precipitation
spreading east across the area after 12Z and reaching KTWF and
KJER around 13/00Z. Conditions lowering to MVFR/IFR with all
mountains becoming obscured in clouds and precipitation.
Freezing rain possible north and west of KBNO-KMYL, changing to
rain after 20Z. Snow levels rising to 5000-7000ft by 13/00Z.
Surface winds SE-SW 5-15kt. Winds aloft at 10kft MSL: SW 15-
30kt increasing to 35-50kt by 12Z. Areas of low level wind shear
in eastern Oregon after 12Z.
&&
.BOI WATCHES/WARNINGS/ADVISORIES...
ID...Winter Storm Warning from 5 AM early this morning to 11 PM MST
this evening IDZ033.
Winter Weather Advisory from 5 AM early this morning to 11 PM
MST this evening IDZ011.
OR...Winter Weather Advisory from 4 AM early this morning to 10 PM
PST this evening ORZ062.
&&
www.weather.gov/Boise
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www.twitter.com/NWSBoise
SHORT TERM...AL
LONG TERM....LC
AVIATION.....LCThe national radar mosaic for the moment the first event began.
1 heavy snow. Local standard time, as filed.
The COOP observer at Halfway reported 6 inches of new snow before changing over to freezing rain.
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, January 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: 937029.