Gallatin National Forest officials are warning backcountry enthusiasts to take extra care after three snowmobilers escaped injury in a weekend avalanche near Big Sky.

Forecaster Alex Marienthal says the snowmobilers were caught Saturday in a 1,500-foot-wide slide that measured 4-to-6-feet deep.

Marienthal says similar avalanches have broken naturally on sugary and weak layers hidden deep inside snowpack in recent days.

Backcountry visitors are urged to avoid slopes that are wind-loaded with snow and to avoid steep slopes that may hide persistent weak layers of snow.

Two snowmobilers were killed in a Jan. 1 avalanche near Lake Dinah, northwest of Seeley Lake.