Avalanche forecast

Bitterroot

West Central Montana Avalanche Center
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Avalanche danger

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Out of date — this forecast expired 4 years ago.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

Highlights

At least a foot of new snow and strong winds have created dangerous avalanche conditions in the mountains. The hazard will continue to rise as more snow arrives today.

A sensitive storm slab exists on all aspects at mid and upper elevations. Strong winds have built wind slabs on multiple aspects. Below the rain/snow line, wet snow avalanches are possible.

Travel in avalanche terrain is not recommended today. 

Avalanche problems

  • Storm Slabs

    • Alpine
    • Treeline
    • Below treeline
    Likelihood
    Likely
    Size
    1–2

    New snow totals vary across the Bitterroot, but at least a foot of new snow has fallen so far. The far northern Bitterroot has received the most, but totals are uncertain due to a lack of weather stations in the area.  Today, 10-15 inches of snow are expected. The hazard is currently considerable but could rise to high across the entire zone by tomorrow.

    Temperatures overnight and yesterday were warm, and the new snow is dense. Snow densities are upside down, with heavier dense snow on top of lighter snow. This has created an especially sensitive storm slab on all aspects. Avoid slopes steeper than 30 degrees, convex rollovers, and terrain traps. 

  • Wind Slabs

    • Alpine
    • Treeline
    • Below treeline
    Likelihood
    Likely
    Size
    1–2

    Strong ridgetop winds out of the west have created fresh wind slabs on multiple aspects. Observations from yesterday reported the strong winds were also transporting snow at mid elevations and wrapping around terrain features. In the Rattlesnake, wind slabs up to 3 feet deep were easily triggered yesterday. Today these slabs could be even deeper. 

    Wind slab can be identified by its smooth rounded appearance. If you experience cracking or collapsing, these are good indicators you are on a wind slab. 

    (2/19/2023)

  • Loose Wet

    • Alpine
    • Treeline
    • Below treeline
    Likelihood
    Possible
    Size
    1–2

    Low elevation temperatures are forecast to rise to the high 30s or low 40s today. With the high temperatures comes the potential for low elevation rain. Yesterday the rain/snow line was reported at 7000’ in the Rattlesnake by afternoon. 

    If you find yourself in the rain today, expect wet snow avalanches. Stay off of slopes over 30 degrees, and be aware of what terrain is above you. 

Avalanche Discussion

A large winter storm is currently impacting all forecast zones creating dangerous avalanche conditions. Since Friday, 3 feet of new snow have fallen in Seeley Lake, 2 feet in the Rattlesnake, and 1-2 in the BItterroot, with higher totals in the north. Winds have been strong and steady out of the west throughout the storm. Snow will continue today, with another foot or two expected by evening across all zones. 

Today, expect storm slabs at all elevations. Yesterday, observations reported  “upside down” snow or snow with higher densities above lighter density snow. This can create conditions where storm slabs are more sensitive and propagate further. There are also widespread sensitive wind slabs in all zones. There is a lot of snow available for transport, and a steady west wind has built large wind slabs on multiple aspects. The strong wind have also been able to reach down into terrain that is often sheltered, creating mid elevation wind slab and cross loading.

Temperatures could rise into the mid 30s, potentially low 40s at low elevations in the Bitterroot. There is uncertainty about where the rain/snow line will be today. Temperatures in Seeley Lake will stay cold enough to avoid a wet snow avalanche problem. Yesterday, a light freezing rain was reported up to 7000’. Rain falling on fresh storm snow creates dangerous avalanche conditions and a natural avalanche cycle. If you find yourself getting rained on today, stay out of avalanche terrain and be very careful traveling under avalanche paths. 

We have been tracking a buried facet/crust combination in the Bitterroot and portions of the Rattlesnake. This layer has not produced any avalanches lately. However, it is still concerning in all areas with a stout buried crust and a cohesive slab above it.  The only way to identify this layer is to dig.

Excellent skiing and riding conditions exist out of avalanche terrain today. 

Let us know what you are seeing by submitting an observation. 

Ski and ride safe! 

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