An amplified and positively-tilted longwave trough moved eastward over North-Central and Southwest MT. Isentropic lift of warm, moist air over an arctic air mass occurred ahead of the trough, allowing widespread light to moderate snow to develop over the region. Low-level northwesterly to northerly upslope flow enhanced this snow along the north aspects of the Big Belt, Little Belt, and Big Snowy Mountains near Great Falls and Lewistown. In addition, mesoscale bands of heavier snow impacted portions of Southwest MT in association with low- to mid-level frontogenesis ahead of a shortwave trough embedded within the aforementioned longwave trough. The bulk of snow during this event fell between Thursday, December 15th and the morning of Friday, December 16th. Many locations reported storm-total snowfall in the range of 3 to 12-inches.

Winter Storm in SOUTHERN LEWIS AND CLARK, MONTANA
From 15-DEC-16 10:35:00 to 15-DEC-16 10:35:00 (MST-7)
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Department of Highways

MT DOT reported I-15 closed at Capital Interchange in Helena due to semi truck stuck on the southbound exit ramp. DOT also reported snow and ice on area roadways at the time.

Winter Storm in JEFFERSON, MONTANA
From 15-DEC-16 15:40:00 to 15-DEC-16 15:40:00 (MST-7)
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Department of Highways

MT DOT declared snow chains required for towing units on I-15 between Boulder Hill and Clancy (i.e. between mile markers 171 and 182).

Winter Storm in JEFFERSON, MONTANA
From 16-DEC-16 16:55:00 to 16-DEC-16 16:55:00 (MST-7)
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Department of Highways

MT DOT declared snow chains required for towing units on Homestake Pass along I-90.

Winter Storm in CASCADE, MONTANA
From 15-DEC-16 20:24:00 to 15-DEC-16 20:24:00 (MST-7)
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Broadcast Media

KFBB-TV reported that the Great Falls Police Department had responded to 25 different vehicular accidents since 6 AM MST December 15th. Some accidents involved injuries, but number and types of injuries were not reported.

Winter Storm in CHOUTEAU, MONTANA
From 15-DEC-16 11:30:00 to 15-DEC-16 11:30:00 (MST-7)
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Department of Highways

Two-vehicle accident with vehicles off roadway per MT DOT. MT DOT also reported snow-covered roadways at time of accident.

Winter Storm in GALLATIN, MONTANA
From 16-DEC-16 13:43:00 to 16-DEC-16 13:43:00 (MST-7)
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Broadcast Media

KBZK-TV reported that the Friday evening, December 16th boys and girls high school basketball games in Bozeman were postponed.

Winter Storm in MADISON, MONTANA
From 16-DEC-16 13:43:00 to 16-DEC-16 13:43:00 (MST-7)
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Broadcast Media

KBZK-TV reported the Twin Bridges vs. Ennis boys and girls high school basketball games for Friday evening, December 16th, had been postponed.

Winter Storm in MEAGHER, MONTANA
From 16-DEC-16 13:43:00 to 16-DEC-16 13:43:00 (MST-7)
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Broadcast Media

KBZK-TV reported the Lone Peak at White Sulphur Springs boys and girls high school basketball games for Friday evening, December 16th, had been postponed.