A moist, Pacific flow , combined with a strong jet stream, resulted in significant blowing and drifting snow across the western mountains.
Every event with a place to put it; 2 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 BYZ wrote it up.
A moist, Pacific flow , combined with a strong jet stream, resulted in significant blowing and drifting snow across the western 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 Billings, MT wrote its last area forecast discussion before the first event at Jan 12, 8:55 PM MST, 4 hours 5 minutes earlier.
Area Forecast Discussion
National Weather Service Billings MT
855 PM MST Tue Jan 12 2021
.UPDATE...
Just a small change to drop overnight lows along the foothills. No
other changes to tonight's forecast. Vertz
&&
.DISCUSSION...
Tonight through Thursday...
All wind advisories and watches have been upgraded to High Wind
Warnings. Issued Winter Storm Warning for western mountains, and
Winter Weather Advisory for the Pryor and Bighorn mountains with
this forecast package.
Severe to Extreme wind event (gusts 70 to 85 mph) continues to be
advertised by the models starting tonight over western foothills
areas, and spreading east tomorrow as a strong Pacific jet pushes
a cold front through the area. Winds on Thursday will subside some
over western areas on Thursday, but will remain severe over areas
from Billings east into the Dakotas into Thursday evening. Unlike
our usual wind events, these strong winds will persist during the
overnight hours, and in fact some areas will see their strongest
winds overnight on Wednesday.
Already have winds gusting over 65 mph in the western foothills
from Livingston to Nye. Winds will continue to trend up overnight
with some enhancement from mountain wave activity likely. Winds
from Big Timber to Harlowton and Judith Gap will also increase
tonight also enhanced by mountain wave activity off the Crazy
mountains. The latest high-res models are showing streams of
strong winds working east into Golden Valley and northern
Stillwater counties overnight as well. Went ahead and upgraded the
Livingston/Nye advisory to a High Wind Warning starting this
afternoon. Pushed the start time up to 6pm for the Big Timber to
Wheatland county warning, and added Golden Valley and Northern
Stillwater to that warning.
Mountain wave activity is also possible tonight into tomorrow in
the Red Lodge foothills, and tomorrow into tomorrow evening in
the Sheridan foothills. Mountain waves can produce sudden damaging
wind gusts out of the blue, so winds can be calm one minute and
gusting over 70 mph the next.
Cold front will be the impetus for strong winds spreading off the
foothills and across the plains. Frontal timing has moved up about
4 to 6 hours over yesterdays runs, which affected warning timing
just a bit in a few areas. Expect the strongest winds in the
west in the morning to early afternoon as the front arrives there,
in the mid afternoon central (Billings) areas, and into the
evening/overnight for areas further south and east (Sheridan,
Miles City, Baker). As previously mentioned, winds will not
subside with sunset with this system so expect sleep to be
disturbed by house creaking noises across the area. Winds will
begin to weaken from extreme levels Thursday morning over areas
west of Billings, but mixing of strong northwest winds behind the
front will keep gusts of 50 to 65 mph going for areas Billings
east into the afternoon and evening hours.
Models are producing some precipitation along the front Wednesday
afternoon as an atmospheric river pushes enough moisture into the
area to somewhat overcome the extreme downslope winds that are
expected. Kept lower elevation precipitation chances low and given
the Pacific nature precipitation will be mainly rain below 6000
feet. For the mountains, west facing slopes look to pick up 4 to 8
inches of snow from late tonight through Thursday morning. The
wind will deposit this snow and existing snow into other areas of
the mountain range and may push some over onto the north/east side
at times with whiteout conditions likely. Issued a Winter Storm
Warning for the Crazy and Beartooth/Absaroka mountains, and a
Winter Weather Advisory for the Bighorn/Pryor mountains, to
handle these extreme winter conditions in the high country. It's
possible the Bighorns could be upgraded to a warning should winds
go stronger than forecast or more snow falls.
Impacts from this extreme wind storm will include tree/power line
damage, dangerous winter conditions in the mountains, dangerous
travel for high profile vehicles and those towing trailers,
property damage from construction projects and loose objects
becoming airborne, poor visibility from blowing dust in spots,
grass fire starts from power line damage, rapid spread of any
fires that do start.
Please take this time to secure any loose property to prevent
damage, and if you are planning travel in a high profile vehicle
or pulling a trailer consider delaying travel until winds subside
Friday. Chambers
Friday through Tuesday...
Friday will continue to be breezy as strong northerly flow aloft
persists over the area especially in southeast Montana but winds
will be tapering off further west as a batch of pressure falls
over north central Montana reverses pressure gradients in the
central zones. The wave driving the pressure falls moves across
the area in the evening bringing a round of showers, mainly over
the mountains. Models show the wave deepening a bit as it gets
further east and begins to phase with the strong northerly flow
aloft which is shifting into the Dakotas. This gives a bit better
chance for some precipitation in southern parts of southeast
Montana but amounts will be light. Temperatures on Friday will
still be above normal means that some of the precip could be rain
instead of snow.
Quieter looking weekend with above normal temperatures before
another wave drops into the area from the northwest trying to
bring a chance for some precipitation and cooler temperatures by
mid week. borsum/Carrothers
&&
.AVIATION...
VFR conditions will prevail. Very strong winds will continue from
KLVM-K6S0-KHWQ, with gusts 60-70 kts through Wednesday night.
Increasing wind gusts of 30-35 kts can be expected across the rest
of southern Montana by Wednesday morning, increasing to 60 kts
Wednesday afternoon. The mountains will be obscured as snow
showers move in there. Carrothers/TWH
&&
.PRELIMINARY POINT TEMP/POPS...
Wed Thu Fri Sat Sun Mon Tue
-----------------------------------------------------------
BIL 044/057 036/042 023/044 031/044 028/044 031/043 029/045
01/N 10/N 00/B 11/B 02/S 32/S 12/S
LVM 034/053 032/037 019/043 030/040 025/042 027/039 026/043
25/W 20/N 00/N 21/N 03/S 31/N 12/S
HDN 035/059 032/043 020/044 026/045 023/044 027/043 024/047
02/W 11/N 00/B 22/S 02/S 32/S 12/S
MLS 033/056 028/041 019/036 022/040 020/041 025/039 024/042
13/W 20/N 00/N 01/B 01/B 22/S 11/B
4BQ 032/055 029/039 020/036 022/039 022/041 025/038 024/042
03/W 31/N 00/N 11/N 01/B 22/S 11/B
BHK 032/056 026/038 017/032 016/037 017/038 021/038 021/039
03/W 20/N 00/N 01/N 01/B 21/E 11/B
SHR 031/058 030/038 017/040 022/039 019/041 022/038 019/042
03/W 52/J 00/B 22/S 02/S 33/S 22/S
&&
.BYZ WATCHES/WARNINGS/ADVISORIES...
MT...High Wind Warning in effect from 6 AM Wednesday to 6 PM MST
Thursday FOR ZONES 29-30-57-138-139-169-170-173-235.
High Wind Warning in effect from noon Wednesday to midnight
MST Thursday night FOR ZONES 31>33-36-37-58.
High Wind Warning in effect until 6 PM MST Thursday FOR ZONES
34-40-42-63-65-66-141-172-228.
High Wind Warning in effect from 6 AM Wednesday to 6 AM MST
Thursday FOR ZONE 56.
Winter Storm Warning in effect until 6 AM MST Thursday FOR
ZONES 67-68.
Winter Weather Advisory in effect from 6 AM Wednesday to 6 PM
MST Thursday FOR ZONE 171.
WY...Winter Weather Advisory in effect from 6 AM Wednesday to 6 PM
MST Thursday FOR ZONE 198.
High Wind Warning in effect from noon Wednesday to 6 PM MST
Thursday FOR ZONE 199.
&&
weather.gov/billingsPreliminary Local Storm Report
National Weather Service Billings, MT
759 PM MST Tue Jan 12 2021
..TIME... ...EVENT... ...CITY LOCATION... ...LAT.LON...
..DATE... ....MAG.... ..COUNTY LOCATION..ST.. ...SOURCE....
..REMARKS..
0614 PM Non-Tstm Wnd Gst 3 WSW Nye 45.41N 109.87W
01/12/2021 M59.00 MPH Stillwater MT Mesonet
0618 PM Non-Tstm Wnd Gst 17 S Fort Smith 45.07N 107.89W
01/12/2021 M60.00 MPH Big Horn MT Mesonet
&&
VertzPreliminary Local Storm Report
National Weather Service Billings, MT
810 PM MST Tue Jan 12 2021
..TIME... ...EVENT... ...CITY LOCATION... ...LAT.LON...
..DATE... ....MAG.... ..COUNTY LOCATION..ST.. ...SOURCE....
..REMARKS..
0716 PM Non-Tstm Wnd Gst 6 ENE Livingston 45.70N 110.45W
01/12/2021 M68.00 MPH Park MT ASOS
&&
VertzPreliminary Local Storm Report
National Weather Service Billings, MT
840 PM MST Tue Jan 12 2021
..TIME... ...EVENT... ...CITY LOCATION... ...LAT.LON...
..DATE... ....MAG.... ..COUNTY LOCATION..ST.. ...SOURCE....
..REMARKS..
0719 PM Non-Tstm Wnd Gst 3 ENE Livingston 45.69N 110.50W
01/12/2021 M65.00 MPH Park MT Dept of Highways
&&
TWHPreliminary Local Storm Report
National Weather Service Billings, MT
903 PM MST Tue Jan 12 2021
..TIME... ...EVENT... ...CITY LOCATION... ...LAT.LON...
..DATE... ....MAG.... ..COUNTY LOCATION..ST.. ...SOURCE....
..REMARKS..
0848 PM Non-Tstm Wnd Gst 6 ENE Livingston 45.70N 110.45W
01/12/2021 M70.00 MPH Park MT ASOS
&&
VertzPreliminary Local Storm Report
National Weather Service Billings, MT
947 PM MST Tue Jan 12 2021
..TIME... ...EVENT... ...CITY LOCATION... ...LAT.LON...
..DATE... ....MAG.... ..COUNTY LOCATION..ST.. ...SOURCE....
..REMARKS..
0925 PM Non-Tstm Wnd Gst 2 SSW Big Timber 45.81N 109.98W
01/12/2021 M52.00 MPH Sweet Grass MT AWOS
&&
VertzPreliminary Local Storm Report
National Weather Service Billings, MT
1247 AM MST Wed Jan 13 2021
..TIME... ...EVENT... ...CITY LOCATION... ...LAT.LON...
..DATE... ....MAG.... ..COUNTY LOCATION..ST.. ...SOURCE....
..REMARKS..
1240 AM Non-Tstm Wnd Gst 2 SSW Big Timber 45.81N 109.98W
01/13/2021 M58.00 MPH Sweet Grass MT AWOS
&&
STPThe national radar mosaic for the moment the first event began.
2 winter storm. Local standard time, as filed.
Significant blowing and drifting occurred across the area. Winds at Wicked Creek RAWS gusted 75 to 80 mph.
Significant blowing and drifting snow occurred across the area. Winds gusted to 69 mph.
After NWS Directive 10-1605, the rules offices file Storm Data by.
Every storm in Montana in 2021Every state in 2021This day in weather historyWarnings in Montana, 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: 935092, 935097.