Montana, 2021

Avalanche and Extreme Cold in Montana, February 11 to 13, 2021

February 11 to 13, 2021 · NWS TFX · 24 events in 16 counties and zones

Over the week-long period of February 8-15, an arctic air mass settled over North-Central Montana, bringing one of the longest stretches of subzero temperatures in recorded history to the area (8 days at Great Falls, tied for 4th longest stretch). While winds were generally on the light side, they combined with the bitterly cold temperatures, resulting in wind chills below -40 F at times.

The toll

Deaths
0
Injuries
0
Property damage
None recorded
Crop damage
None recorded
Events
24

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.

What happened

The episode as NWS TFX wrote it up.

Over the week-long period of February 8-15, an arctic air mass settled over North-Central Montana, bringing one of the longest stretches of subzero temperatures in recorded history to the area (8 days at Great Falls, tied for 4th longest stretch). While winds were generally on the light side, they combined with the bitterly cold temperatures, resulting in wind chills below -40 F at times. These wind chills prompted Wind Chill Advisories and Wind Chill Warnings across the entire Great Falls County Warning Area. The core of the cold arrived for Wednesday through Friday, with air temperatures dropping to -30 or colder in some areas.

What forecasters said that day

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 Great Falls, MT wrote its last area forecast discussion before the first event at Feb 11, 4:38 PM MST, 1 hour 17 minutes earlier.

Area forecast discussion, Feb 11, 4:38 PM MST, 1 hour 17 minutes before
Area Forecast Discussion
National Weather Service Great Falls MT
438 PM MST Thu Feb 11 2021

...Updated Aviation Discussion...

.SYNOPSIS...

Continued very cold temperatures and dangerous wind chills will
prevail across the region through Friday and into Saturday. Near
record cold minimum temperatures are possible across north central
Montana the next few nights before temperatures slowly moderate back
towards seasonal averages late this weekend into early next week.
Most snow outside of some occasional flurries will remain from the
Helena area south through the weekend.

&&

.DISCUSSION...

This evening through Saturday night...
A deep upper level low remains over central Canada and will
continue to pump very cold Arctic air into Montana through the
remainder of this week. The pattern finally begin to shift
eastward later this weekend into early next week. All wind chill
warnings/advisories remain in effect for their zones as currently
set, and have been extended through Friday night. Some wind chill
highlights likely will be needed for Saturday and perhaps Sunday
nights, but changes are likely in terms of what zones are covered
and warning/advisory level of the zones, so decisions on those
nights is deferred to tonight or tomorrow. Record or near record
minimum temperatures remain possible in many locations tonight.
Some areas of flurries and light snow have been intermittently
affecting parts of central MT, including the Helena Valley, and
this may continue into tonight with minor accumulations possible.
A more widespread accumulating snowfall will affect southwestern
this evening through Friday evening. Valley locations are likely
to stay under an inch or two, except 1-3 inches for the Big Sky to
West Yellowstone stretch, and several inches are possible in the
mountains, especially along the western border of Beaverhead.
Another weak wave may bring light snow to SW MT Saturday into
Saturday evening.

Sunday through next Thursday...
The deep upper level low finally moves off to the east on Sunday,
thereby allowing a westerly flow aloft to develop over the
region. Temperatures will begin to moderate late Sunday so that
even overnight lows should remain above zero by Tuesday as
currently forecast. However, there remains some uncertainty on the
speed of the warm-up, especially on the north-central Plains
Monday and Tuesday, where the NBM and other ensembles like the
GEFS have 20+ degree ranges on high temps those days. Occasional
weak weather disturbances will likely move through the region next
week for a continued off and on chance for light snow at times.
Currently the best time frame looks to be Monday through Tuesday
night, but even in that 48 hour time frame, accumulations look to
be pretty minimal outside of the mountains. -Kredensor/mpj

&&

.AVIATION...
438 PM MST Thu Feb 11 2021 (12/00Z TAF period)

Clouds increase again along and south of a KHLN-KMVH line through
tonight as the next system moves into the area. MVFR to locally IFR
ceilings and visibility are expected in areas of snow and low
clouds, mainly for KBZN, KEKS, and KDLN. Can't rule out some periods
of light snow for KHLN, as well. Mountain obscuration will be a
common hazard for the central and SW MT mountain ranges.

Refer to weather.gov/zlc for more detailed regional aviation weather
and hazard information.

&&

.PRELIMINARY POINT TEMPS/POPS...
GTF -34 -10 -24  -8 /   0   0   0   0
CTB -33  -8 -26  -8 /   0   0   0   0
HLN -23  -6 -20  -2 /  30  30  10  20
BZN -20  -6 -23  -1 /  60  60  10  30
WYS   1  18 -12  19 /  70  80  30  60
DLN -11   1 -15   5 /  60  60  10  40
HVR -32  -8 -27  -7 /   0   0   0   0
LWT -34 -12 -27  -8 /   0  10   0   0

&&

.TFX WATCHES/WARNINGS/ADVISORIES...
Wind Chill Warning until 11 AM MST Saturday Cascade...Central
and Southern Lewis and Clark...Chouteau...Eastern Pondera...
Eastern Teton...Fergus...Judith Basin...Southern Rocky Mountain
Front.

Wind Chill Advisory until 11 AM MST Saturday Broadwater...
Gallatin...Jefferson...Madison...Meagher.

Wind Chill Warning until 11 AM MST Saturday Blaine...Eastern
Glacier...Hill...Liberty...Northern Rocky Mountain Front...Toole.

&&

http://www.weather.gov/greatfalls

Event by event

18 cold/wind chill, 5 extreme cold/wind chill, 1 avalanche. Local standard time, as filed.

Cold/Wind Chill, Cascade

When
February 11, 5:55 PM MST
Where
Cascade forecast zone
Reported by
ASOS

Asos station kgtf great falls reports wind chill of -49.

Cold/Wind Chill, Southern Lewis and Clark

When
February 11, 5:56 PM MST
Where
Southern Lewis and Clark forecast zone
Reported by
Mesonet

Mesonet station mtmdp macdonald pass (mt dot) reports wind chill of -46.

Cold/Wind Chill, Madison

When
February 11, 5:57 PM MST
Where
Madison forecast zone
Reported by
Mesonet

Mesonet station mtnor norris hill (mt dot) reports wind chill of -40.

Cold/Wind Chill, Fergus

When
February 11, 5:58 PM MST
Where
Fergus forecast zone
Reported by
Mesonet

Mesonet station k1mm moore reports wind chill of -50.

Cold/Wind Chill, Judith Basin

When
February 11, 5:58 PM MST
Where
Judith Basin forecast zone
Reported by
AWOS

Awos station k1bm bravo reports a wind chill of -46.

Cold/Wind Chill, Fergus

When
February 11, 6:05 PM MST
Where
Fergus forecast zone
Reported by
Mesonet

Mesonet station mtlew lewistown divide (mt dot) reports wind chill of -48.

Cold/Wind Chill, Judith Basin

When
February 11, 6:06 PM MST
Where
Judith Basin forecast zone
Reported by
Mesonet

Mesonet station mtgys geyser (mt dot) reports wind chill of -48.

Cold/Wind Chill, Toole

When
February 11, 6:06 PM MST
Where
Toole forecast zone
Reported by
Mesonet

Mesonet station mtswt sweetgrass (mt dot) reports wind chill of -46.

Cold/Wind Chill, Liberty

When
February 11, 6:15 PM MST
Where
Liberty forecast zone
Reported by
Mesonet

Mesonet station ew9495 hill reports wind chill of -44.

Extreme Cold/Wind Chill, Blaine

When
February 11, 6:18 PM MST
Where
Blaine forecast zone
Reported by
Mesonet

Mesonet station fblm8 fort belknap raws reports wind chill of -42.

Cold/Wind Chill, Cascade

When
February 11, 6:21 PM MST
Where
Cascade forecast zone
Reported by
Mesonet

Mesonet station fw2944 belt reports wind chill of -42.

Cold/Wind Chill, Blaine

When
February 11, 8:18 PM MST
Where
Blaine forecast zone
Reported by
RAWS

Ft. Belknap RAWS reports wind chill of -43.

Extreme Cold/Wind Chill, North Rocky Mountain Front

When
February 11, 8:57 PM MST
Where
North Rocky Mountain Front forecast zone
Reported by
Department of Highways

MT DOT Two Medicine Bridge sensor reports a wind chill of -46F.

Cold/Wind Chill, Southern Rocky Mountain Front

When
February 11, 8:59 PM MST
Where
Southern Rocky Mountain Front forecast zone
Reported by
Department of Highways

Pendroy MDOT sensor reports wind chill of -45.

Cold/Wind Chill, Eastern Teton

When
February 11, 9:00 PM MST
Where
Eastern Teton forecast zone
Reported by
Mesonet

MCSCN Dahlman reports wind chill of -44.

Cold/Wind Chill, Eastern Pondera

When
February 11, 9:00 PM MST
Where
Eastern Pondera forecast zone
Reported by
Mesonet

Conrad SCAN reports wind chill of -42.

Extreme Cold/Wind Chill, Eastern Glacier

When
February 11, 9:00 PM MST
Where
Eastern Glacier forecast zone
Reported by
ASOS

KCTB asos reports wind chill of -48.

Extreme Cold/Wind Chill, Chouteau

When
February 11, 9:00 PM MST
Where
Chouteau forecast zone
Reported by
Mesonet

MT-meso Fort Benton reports wind chill of -43.

Extreme Cold/Wind Chill, Hill

When
February 11, 9:00 PM MST
Where
Hill forecast zone
Reported by
ASOS

KHVR asos reports wind chill of -47.

Cold/Wind Chill, Beaverhead

When
February 13, 10:00 AM MST
Where
Beaverhead forecast zone
Reported by
Mesonet

Msonet station mtbhp big hole pass (mt dot) reports wind chill of -40.

Cold/Wind Chill, Hill

When
February 13, 7:30 PM MST
Where
Hill forecast zone
Reported by
Mesonet

Mesonet station dw0217 havre reports wind chill of -46.

Cold/Wind Chill, Toole

When
February 13, 10:05 PM MST
Where
Toole forecast zone
Reported by
Mesonet

Mesonet station dw0975 kevin reports wind chill of -40.

Cold/Wind Chill, Beaverhead

When
February 13, 10:30 PM MST
Where
Beaverhead forecast zone
Reported by
Mesonet

Mesonet station fw1664 hingham reports wind chill of -42.

Avalanche, Liberty

When
February 13, 11:46 PM MST
Where
Liberty forecast zone
Reported by
Mesonet

Mesonet station ew9427 chester-5nw reports wind chill of -44.

What these are

Cold/Wind Chill
Cold or wind chill below warning criteria that caused deaths, injuries or damage.
Extreme Cold/Wind Chill
Temperatures or wind chills at or below the local warning criteria, or cold that caused deaths.
Avalanche
A mass of snow sliding down a mountainside that caused a death, an injury or damage.

After NWS Directive 10-1605, the rules offices file Storm Data by.

The same day elsewhere

More

Every storm in Montana in 2021Every state in 2021This day in weather historyWarnings in Montana, February 2021

Sources

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: 935042, 935068, 935073, 935046, 935065, 935048, 935064, 935074, 935070, 935041, 935044, 935175, 935161, 935152, 935158, 935159, 935164, 935170, 935171, 935038, 935051, 935075, 935058, 935072.