An arctic front combined with abundant Pacific moisture resulted in very heavy snowfall over a 2-day period. Snow accumulations of 8+ inches occurred from Billings and areas westward. The biggest impacts with this storm occurred after the snow ended as lee-side troughing developed. This resulted in very tight pressure gradients across the Upper Yellowstone and Stillwater valleys. In addition, very strong winds aloft, around 50kts, mixed down to the surface across these areas. As a result, very strong surface winds occurred from about Laurel to Livingston. These strong winds, combined with fresh powdery snowfall from the 15th and 16th, resulted in a blizzard across portions of Stillwater, Sweet Grass, and Park Counties.
Peak winds (with new snow on the ground) were the following:
Livingston-75 to 83 mph
Nye-74 mph
Big Timber-72 mph
Fort Smith-63 mph
Roscoe-58 mph
Harlowton-54 mph
Interstate 90 was closed for 27 hours from Sunday the 18th to Monday the 19th from Livingston to Park City. In addition, Park and Sweet Grass County roads drifted shut.
The following impacts occurred across Stillwater, Sweet Grass and Park Counties:
Stillwater County
-Upwards of a foot of snow on the ground with gusts at least 75 mph at the height of the storm
-Stillwater Mine (normally continuous operations) closed down for their day shift on the 19th
-Columbus, Park City, Reed Point, and Rapelje all cancelled classes on Friday the 16th
-Multiple motor vehicle accidents
Sweet Grass County
-Upwards of a foot of snow on the ground with peak winds just over 70 mph at the height of the storm
-Big Timber schools were closed on Monday the 19th
-The area was overwhelmed with stranded travelers
-From Friday through Tuesday, County 911 Dispatchers fielded:
-95 calls, 89 were weather related
-Roughly 1 call per hour, more than triple their normal wintertime average
(typically 4-6 calls per day)
-Ambulance ran 10 calls, well above average of one per day
-Search and Rescue responded to calls to help ambulance crews access patients
and in some cases carry patients through the snow to ambulances
Park County
-Numerous county roads were drifted shut from blowing snow, crews were unable
to maintain roads, including the Livingston area
-Utilized heavy equipment to clear the snow
-Assistance was requested from contractors in Gallatin County(Bozeman) for snow removal
-Emergency crews were prepared to follow the plows for emergency calls with much
longer response times expected
-Drivers reportedly were unable to see and drove into snow drifts
-County offices were closed on Monday the 19th.

Blizzard in BEARTOOTH FOOTHILLS, MONTANA
From 17-DEC-16 19:24:00 to 19-DEC-16 11:59:00 (MST-7)
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Trained Spotter

Winds were gusting 50 to 56 mph resulting in significant blowing and drifting snow. Snow drifts of 8 feet were also reported.

Blizzard in LIVINGSTON AREA, MONTANA
From 18-DEC-16 09:25:00 to 19-DEC-16 11:45:00 (MST-7)
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Department of Highways

Winds gusted 50 to 56 mph resulting in significant blowing and drifting snow. Interstate 90 was closed.

Blizzard in NORTHERN SWEET GRASS, MONTANA
From 17-DEC-16 12:40:00 to 19-DEC-16 07:20:00 (MST-7)
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Department of Highways

Winds gusted 45 to 65 mph resulting in 1/4 mile visibilities at Big Timber. Interstate 90 was closed.

Blizzard in NORTHERN PARK COUNTY, MONTANA
From 18-DEC-16 07:00:00 to 19-DEC-16 11:00:00 (MST-7)
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Trained Spotter

Blizzard conditions resulted in impassable roads due to blowing and drifting snow.