Jan 4, 2018 @ 6:12 am

The current avalanche danger is CONSIDERABLE on wind loaded slopes above 6,500 feet in the West Central Montana backcountry. A moderate avalanche danger exists on all other terrain. Careful evaluation of terrain and snowpack is necessary to identify areas of concern.

Good morning, this is Logan King with the West Central Montana Avalanche Center’s avalanche advisory for January 4th, 2018.  This danger rating does not apply to operating ski areas, expires at midnight tonight and is the sole responsibility of the U.S. Forest Service.

Weather and Snowpack

Winds this morning at Deer Mountain are 9 mph gusting to 12 mph from the SSE. At point six the winds are 13 mph gusting to 15 mph from the SW. Mountain temperatures currently range from the high teens to mid twenties. An additional 1-2 inches of snow accumulated in the last 24 hours.

Travis and I rode to Twin Lakes in the central Bitterroot yesterday. We found stable snow at lower elevations with wind slab concerns continuing at higher elevations. The primary avalanche concern today is wind slabs.

The tail end of the last storm brought strong winds and developed some large wind slabs. Wind slabs are primarily located above 6,500 feet. Avoid terrain that is wind loaded. We observed a few small natural wind slab crowns yesterday and continue to receive reports of wind slabs failing with human triggers and stepping down to the Thanksgiving crust.

The secondary avalanche concern is the deep persistent weak layer on top of the Thanksgiving crust. After the last couple of storms this layer is now buried deep but is reactive when paired with wind slabs. Be very cautious of this layer, the consequences of a slide this deep would likely be catastrophic. Avoid any steep terrain where this layer is suspect including run out zones.

Loose snow avalanches are the final concern today. We observed loose surface snow sluffs yesterday that were small and non threatening. Be aware of terrain traps that increase the consequences of getting caught in a loose snow avalanche. We observed a small windslab that was triggered by a loose snow avalanche and ran through rocks breaking branches and small trees (video).

Light snow showers today and into tomorrow before the next system moves in this weekend. Snow total today will be insignificant but will provide more snow for transport. Avalanche conditions will remain the same through today.

If you are out in the backcountry, please send us your observation, these are very helpful in producing the advisory. A weather update will be issued on Friday.

Ski and ride safe.


Problem 1 - Wind Slabs

  • TYPE


    Wind Slabs

    Release of a cohesive layer of snow (a slab) formed by the wind.  Wind typically erodes snow from the upwind sides of terrain features and deposits snow on the downwind side.  Wind slabs are often smooth and rounded and sometimes sound hollow, and can range from soft to hard. Wind slabs that form over a persistent weak layer (surface hoar, depth hoar, or near-surface facets) may be termed Persistent Slabs or may develop into Persistent Slabs.

  • SIZE


    2 (Large)

    The potential size of avalanche resulting from this problem.




    The likelihood of an avalanche resulting from this problem.

Wind slabs are widespread and suspect above 6,500 feet.

Problem 2 - Deep Persistent

  • TYPE


    Deep Persistent Slabs

    Release of a thick cohesive layer of hard snow (a slab), when the bond breaks between the slab and an underlying persistent weak layer, deep in the snowpack or near the ground.  The most common persistent weak layers involved in deep, persistent slabs are depth hoar, deeply-buried surface hoar, or facets surrounding a deeply-buried crust. Persistent, Deep-Slabs are typically hard to trigger, are very destructive and dangerous due to the large mass of snow involved, and can persist for months once developed. They are often triggered from areas where the snow is shallow and weak, and are particularly difficult to forecast for and manage. They commonly develop when Persistent Slabs become more deeply-buried over time.

  • SIZE


    3 (Large-Very Large)

    The potential size of avalanche resulting from this problem.




    The likelihood of an avalanche resulting from this problem.

Susceptible to human triggers in shallow areas or when paired with a wind slab.

Problem 3 - Loose

  • TYPE


    Loose Wet

    Release of wet unconsolidated snow or slush. These avalanches typically occur within layers of wet snow near the surface of the snowpack, but they may quickly gouge into lower snowpack layers. Like Loose-Dry Avalanches,they start at a point and entrain snow as they move downhill, forming a fan-shaped avalanche. They generally move slowly, but can contain enough mass to cause significant damage to trees, cars or buildings. Other names for loose-wet avalanches include point-release avalanches or sluffs. Loose-wet avalanches can trigger slab avalanches that break into deeper snow layers.

  • SIZE


    < 1 (Small)

    The potential size of avalanche resulting from this problem.




    The likelihood of an avalanche resulting from this problem.

Mild temps and mixed sun yesterday was creating small loose slides.



Light scattered snow showers with mild temperatures through tonight.

This information is the sole responsibility of the Forest Service and does not apply to operating ski areas. The avalanche danger rating expires at midnight tonight but the information can help you make a more informed decision regarding travel in avalanche terrain for the next few days.

Our advisory area includes National Forest System lands in the Bitterroot Mountains from Lost Trail Pass north to Granite Pass, the Rattlesnake Mountains north of Missoula and the Southern Swan and Mission Mountains near Seeley Lake, MT. Avalanche information for the Lookout Pass/St. Regis Basin area is available from the Idaho Panhandle Avalanche Center.