The seasons first, widespread winter storm occurred across most of the Billings Forecast Area from February 5th through February 7th. This was also the first and only arctic airmass of the season that impacted the Billings Forecast Area.
An arctic front blasted through the area on the 5th.  Following the front, a moist Pacific flow aloft moved over this arctic airmass which resulted in a prolonged period of heavy snow. Many areas received 8 to 12 inches of snow with some locations reporting well over a foot of snow. After the snow ended and skies cleared, overnight lows of -20F to -40F were common. Many areas stayed below zero for 7 consecutive days.
Major impacts occurred with this storm as warm roads initially melted the snow. These wet roads then quickly froze resulting in icy and hazardous driving conditions. As a result, many accidents occurred across the area. In addition to the snow, strong winds resulted in blowing and drifting snow, as well as significantly reduced visibilities. US-191 was closed near Harlowton due to severe driving conditions as visibilities were a half mile in snow with wind gusts to 43 mph.
Two major crashes occurred on I-90 near Park City just a day apart. The first incident occurred on Saturday the 6th and was a 20-vehicle pileup on the eastbound lanes of I-90. Responders were dealing with a semi stuck in the median when another semi traveling east failed to slow down and yield to road signage. That semi nearly struck a Stillwater County deputy before jackknifing and causing the pileup of vehicles behind it. The Montana Highway Patrol reported only minor injuries with this incident.  Another major crash occurred on Sunday the 7th. A pickup truck was hauling a camper that jackknifed. A second pickup truck hauling a camper then crashed into the jackknifed pickup. Shortly after the initial crash, multiple semis crashed into each other as they tried to slow down on an icy bridge deck ahead of the pickup trucks. In one instance, a semi collided with the cab of another semi that was sandwiched in the middle of everything. The driver of the semi that was struck had to be extricated from the vehicle. All five semis were disabled by the crash and two of them caught fire. Just east of this crash, two other semis crashed, including one that went into the median.

Winter Storm in SOUTHERN ROSEBUD, MONTANA
From 05-FEB-21 08:00:00 to 07-FEB-21 03:00:00 (MST-7)
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Trained Spotter

Snowfall of 6 inches was reported across the Lame Deer area.

Winter Storm in SOUTHEASTERN CARBON, MONTANA
From 05-FEB-21 07:35:00 to 07-FEB-21 03:00:00 (MST-7)
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Trained Spotter

Snowfall of 10 inches was reported across the Bridger area.

Winter Storm in BEARTOOTH FOOTHILLS, MONTANA
From 05-FEB-21 07:30:00 to 07-FEB-21 03:00:00 (MST-7)
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Trained Spotter

Reed Point and Fishtail received 12 inches of snow.

Winter Storm in LIVINGSTON AREA, MONTANA
From 05-FEB-21 07:00:00 to 07-FEB-21 03:00:00 (MST-7)
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Trained Spotter

The Livingston area received 9 to 17 inches of snow.

Winter Storm in RED LODGE FOOTHILLS, MONTANA
From 05-FEB-21 07:10:00 to 07-FEB-21 03:00:00 (MST-7)
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Trained Spotter

Red Lodge received 10 inches of snow.

Winter Storm in SOUTHWESTERN YELLOWSTONE, MONTANA
From 05-FEB-21 07:15:00 to 07-FEB-21 03:00:00 (MST-7)
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Trained Spotter

The Billings area received 8 to 10 inches of snow. Multiple accidents were reported.

Winter Storm in SOUTHERN WHEATLAND, MONTANA
From 05-FEB-21 06:58:00 to 07-FEB-21 03:00:00 (MST-7)
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Trained Spotter

U.S 191 from Harlowton north was closed due to severe conditions.

Winter Storm in NORTHEASTERN YELLOWSTONE, MONTANA
From 05-FEB-21 03:00:00 to 07-FEB-21 03:00:00 (MST-7)
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Trained Spotter

Snowfall of 7 to 10 inches was reported across the Pompeys Pillar area.

Winter Storm in MELVILLE FOOTHILLS, MONTANA
From 05-FEB-21 05:00:00 to 07-FEB-21 03:00:00 (MST-7)
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Trained Spotter

Snowfall of 12 inches was reported across the Melville area.

Winter Storm in NORTHERN CARBON, MONTANA
From 05-FEB-21 06:00:00 to 07-FEB-21 03:00:00 (MST-7)
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Trained Spotter

Snowfall of 8 to 12 inches was reported across the Joliet, Fromberg and Bridger areas.

Winter Storm in BIGHORN CANYON, MONTANA
From 05-FEB-21 07:00:00 to 07-FEB-21 03:00:00 (MST-7)
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Trained Spotter

The Big Horn Canyon received 6 inches of snow.

Winter Storm in NORTHERN SWEET GRASS, MONTANA
From 05-FEB-21 06:00:00 to 07-FEB-21 03:00:00 (MST-7)
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Trained Spotter

Snowfall of 11 inches was reported in the Big Timber area.

Winter Storm in SOUTHERN BIG HORN, MONTANA
From 05-FEB-21 03:00:00 to 07-FEB-21 03:00:00 (MST-7)
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Trained Spotter

Snowfall of 7 to 11 inches occurred from Fort Smith to Lame Deer.

Winter Storm in JUDITH GAP, MONTANA
From 05-FEB-21 06:00:00 to 07-FEB-21 03:00:00 (MST-7)
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Trained Spotter

U.S 191 was closed due to severe driving conditions.

Winter Storm in NORTHERN BIG HORN, MONTANA
From 05-FEB-21 03:00:00 to 07-FEB-21 03:00:00 (MST-7)
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Trained Spotter

Busby and Hardin both received 6 to 10 inches of snow.

Winter Storm in GOLDEN VALLEY, MONTANA
From 05-FEB-21 04:00:00 to 07-FEB-21 03:00:00 (MST-7)
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Trained Spotter

Ryegate received 12 to 14 inches of snow.

Winter Storm in NORTHERN STILLWATER, MONTANA
From 05-FEB-21 03:45:00 to 07-FEB-21 03:00:00 (MST-7)
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Trained Spotter

Snowfall of 6 to 10 inches was widespread across the area.

Winter Storm in MUSSELSHELL, MONTANA
From 05-FEB-21 03:00:00 to 07-FEB-21 03:00:00 (MST-7)
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Trained Spotter

The Roundup area received 8 inches of snow.

Winter Storm in CRAZY MOUNTAINS, MONTANA
From 04-FEB-21 17:00:00 to 07-FEB-21 05:00:00 (MST-7)
Property damage: 0.00K
Crop damage: 0.00K
Reported by: SNOTEL

Snowfall around 12 inches occurred over the mountains.

Winter Storm in ABSAROKA / BEARTOOTH MOUNTAINS, MONTANA
From 04-FEB-21 18:00:00 to 07-FEB-21 09:00:00 (MST-7)
Property damage: 0.00K
Crop damage: 0.00K
Reported by: SNOTEL

The mountains around Livingston and Red Lodge received 12 to 18 inches of snow.