Avalanche forecast

Seeley Lake

West Central Montana Avalanche Center
View on map

Avalanche danger

Sat
Alpine
4 · High
Treeline
4 · High
Below
3 · Considerable
Open full map
Out of date — this forecast expired 5 years ago. You’re viewing past conditions, not the current bulletin.

Highlights

Very dangerous avalanche conditions exist. Continued snowfall, rising temperatures, and strong winds are increasing the avalanche hazard. Human triggered avalanches are certain, and natural avalanches are likely. Backcountry travel is not recommended.

Avalanche problems

  • Wind Slabs

    • Alpine
    • Treeline
    • Below treeline
    Likelihood
    Certain
    Size
    1–2.5

    The main avalanche problem has pivoted to windslab. While there is new snow falling, most of it will be affected by wind. Winds increased to moderate yesterday afternoon and sustained this speed overnight. They will increase to strong today with extreme gusts. There is ample snow for transport, and snow that falls today will add to this. By three PM yesterday, wind slabs had become touchy and very reactive to human triggering. With continued growth overnight and today, these will be very dangerous. Due to the strength of the wind, windslab will form not just at ridges but farther down slopes and on multiple aspects as winds wrap around terrain features. 

    Natural avalanches are likely, and human-triggered avalanches are certain. 

    Travel in the backcountry is not recommended today.

  • Wet Slabs

    • Alpine
    • Treeline
    • Below treeline
    Likelihood
    Possible
    Size
    1–3

    In some parts of the forecast area, such as the central Bitterroot, the freezing level has already risen to 6500’. Areas up to 5600’ have been above freezing for 12 hours. Temperatures have saturated the new snow, which sits on lower density snow and facets created in the shallow low elevation snowpack.  Temperatures will rise this morning, and a wet snow/freezing rain/rain mix is forecast, which will further saturate the snowpack. Conditions are perfect for wet slab release at lower elevations. Slopes you may not normally consider avalanche terrain could be a problem today. Road cuts, such as the ones by Crystal Amphether parking, are loaded with enough snow to bury, injure or kill a person. Numerous wet or heavy snow slides may occur where not normally seen. Valleys in the Bitterroot such as Lost Horse, where peak to creek slide paths exist, could see very large slides today due to warmer temperatures in the area. Avoid back-country travel where wet sloppy snow is found. If there is any rain, it’s time to head home.

  • Deep Persistent Slabs

    • Alpine
    • Treeline
    • Below treeline
    Likelihood
    Possible
    Size
    1–3

    Northerly aspects above 7400’ in the southern Bitterroot harbor a depth hoar layer now buried over 5 feet deep. 

    This layer still shows a high likelihood for propagation in tests and is capable of producing avalanches. 

    Heavy snowfall and rising temperature may be what it takes to tip the balance on this layer. 

    These slides would not be survivable.

    Avoid all travel where this layer exists.

Avalanche Discussion

This is the second day of high avalanche danger and an avalanche warning. The weather that impacted the area yesterday has intensified with strong winds and rising temperatures. The avalanche hazard will continue to rise throughout the day. 

Yesterday's avalanche hazard did not rise to the extent anticipated across the forecast area. Temperatures remained colder than forecasted in the northern portion leading to limited snowpack consolidation. There was abundant cracking, but the slab lacked the cohesion to transmit propagations, limiting storm slab avalanches. Snowfall was also slightly less than anticipated with 12” or 1.2” SWE in the Rattlesnake by yesterday evening. The southern Missions saw up to 18”. Winds were relatively mild until mid-afternoon, when they rose to moderate. Wind slab built quickly, and we remotely triggered wind slab from the ridge in addition to finding evidence of natural releases.

 The forecast area's southern portion saw heavier snowfall, up to 18” or 1.7” of SWE, and higher temperatures. Twin Lakes at 6400’ reached 32º at 4:00 pm. This led to more cohesion and a more reactive storm slab. Multiple slides were reported in the southern Bitterroot, as well as reports of widespread cracking. 

The remoteness of many slide paths and poor visibility limit knowledge of the extent of avalanches. Valleys such as Lost Horse with multiple steep avalanche paths likely saw an active avalanche cycle with heavy loading, warm temperatures, and increasing wind in the afternoon. These are good places to avoid today.

This morning temperatures have risen to 28º at Stuart, and freezing levels are averaging 5000 feet, with warmer temperatures in the Bitterroot. Temperatures will rise to 37º at upper elevations until mid-afternoon when the arrival of a cold front drops them to the mid-teens. 

Snow continues to fall with up to 7”  last night and up to 12” expected today. The mountains have received up to 2.7” of SWE in the past 48 hours, a tremendous load in a short time. 

Winds were a sustained 25mph last night with gusts to 40mph. Today they will be 30mph with gusts to 55mph. Wind slab will grow rapidly throughout the day. 

These three factors, continued snowfall, rising temperatures, and strong winds, could tip the balance on weak layers in the snowpack. The primarily weak layer is low-density snow from January 5th. It could also include the depth hoar layer on northerly aspects in the southern Bitterroot and isolated areas of faceting in the central Bitterroot and Rattlesnake.

Elevations below 5000’ will see wet, heavy snow and possibly rain, increasing the likelihood of wet slides.

Today is a great day to enjoy ample powder inbounds with lift service. Dangerous conditions exist in the backcountry, and it is best to let this storm and avalanche cycle run it's course before venturing out. 

Any observation on snow and avalanche conditions is very helpful to us. Even just a picture is great. Please submit observations here: https://missoulaavalanche.org/submit-an-observation/

Ski and ride safe.

 

Regions covered