Jan 13, 2021 @ 7:04 pm

The avalanche warning has ended. The avalanche danger for the west central Montana backcountry is HIGH. This danger rating does not apply to operating ski areas and is the sole responsibility of the U.S. Forest Service. Tomorrow’s forecast will update avalanche conditions.

Continued snow and wind will accompany rising temperatures with freezing levels climbing up to 8000′ and rain to 7000′ by Wednesday morning.  Up to 3” of SWE is expected by tomorrow night. Avalanche hazard will increase with the storm. Of particular concern is the effect of warm temps, heavy snow, and rain on mid-elevations where the snowpack has the worst structure. Wind slab will be growing. Widespread surface hoar under the new snow is an issue. Natural avalanches are likely, human triggered avalanches are certain.

Variable is the best way to describe the snowpack throughout the forecast area. Minutely variable. Wide-ranging conditions can be found in very close proximity making stability assessments challenging. Yesterday at Gash Point the 6’ deep snowpack at 7300’ on the north aspect was well consolidated with no concerning layers. 500’ lower at 6800’ on the same aspect the snowpack was 3’ deep, comprised entirely of facets. It has truly terrible structure that cannot be trusted. Shallow mid-elevation and wind-scoured areas have similar faceting throughout the forecast area.

In the southern Missions yesterday, a small human triggered avalanche ran on buried surface hoar. A similar problem exists throughout the forecast area.

The north aspect of Mt. Fuji over the weekend was showing increased strength and consolidation, while the south face has developed depth hoar and failing in tests.

In the southern Bitterroot yesterday, small wind slabs were touchy, and faceted layers remain a concern.

The Rattlesnake may have the shallowest snowpack in the area and as a result the worst structure. Some spots are touchier than others but the whole zone requires caution. Staying under 30º is wise.

Throughout the forecast area there was widespread surface hoar prior to this storm.

Heavy snow and wind are rapidly loading all of these layers and problems. Warm temperatures are loosening bonds within the snowpack. Rain may further deteriorate stability.

The Bottom Line

Travel in avalanche terrain is not recommended. Avoid runout zones. You can trigger an avalanche remotely.

This warning will be terminated or extended tomorrow at 7:00 pm.

Ski and ride safe.


Problem 1 - Wind Slab

  • 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


    2-3 (Large)

    The potential size of avalanche resulting from this problem.



    Very Likely/Certain

    The likelihood of an avalanche resulting from this problem.

Widespread natural release of wind slab today


See Forecast.

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.