Avalanche forecast

Bitterroot

West Central Montana Avalanche Center
View on map

Avalanche danger

Mon
Alpine
3 · Considerable
Treeline
2 · Moderate
Below
2 · Moderate
Open full map
Out of date — this forecast expired 6 months ago. You’re viewing past conditions, not the current bulletin.

Highlights

Conditions could change quickly today with forecast wind and warm temperatures. Look for and avoid steep slopes with freshly wind-blown snow, or 6 inches or more of wet snow. It is still possible to trigger an avalanche on buried weak layers. These avalanches could be large and destructive. When making decisions, it is important to consider the consequences of a large avalanche. 

The elevated hazard at low elevations focuses on the Lolo Pass area.  Elsewhere, low elevations are at Low Hazard, as the snowpack is largely below threshold for avalanches.

Avalanche problems

  • Wind Slabs

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

    Wind speeds picked up again overnight and are forecast to remain high today. Couple this with soft new snow still available for transport, and we can expect new sensitive wind slabs today. The caveat, is that high freezing levels yesterday and overnight caused moist snow to at least 7500 feet. If the snow is wet, the wind has a very difficult time blowing it into a slab. Expect wind slabs specific to the highest elevations, where dry snow remains.

    If you find a localized area of relatively deeper or denser snow, you’ve likely found a wind slab. Shooting cracks underfoot are further indications of unstable snow. To avoid this problem, stay off of steep slopes where you see these signs of wind loading and/or signs of instability.

    Intentionally-triggered wind slab avalanche on a steep test slope. NE aspect at 7,600' in the Lost Horse drainage.

    (3/6/2026) Photo: Ben VandenBos

  • Persistent Slabs

    • Alpine
    • Treeline
    • Below treeline
    Likelihood
    Possible
    Size
    2–3

    Prominent weak layers are buried 1-3 feet deep. Snowfall and rain over the past few days has been incrementally loading the snowpack. Wind-deposited snow and precipitation will continue to load it today. It remains to be seen if this will eventually tip the balance to natural avalanches, and increase the sensitivity to human triggering.

    What we do know, is that human-triggered avalanches are already possible, and as the snow piles up their potential size becomes larger. Two days ago a skier triggered a large avalanche in the Southern Bitterroot (click here for information). These same weak layers exist throughout the Bitterroot and you could expect similar avalanches anywhere you find the right slab and weak layer combination. However, it’s difficult to predict exactly where on a slope you’ll find a trigger point. As always, persistent slab problems come with inherent uncertainty.

    As this avalanche problem becomes more stubborn, we’ve reached a point where we aren’t seeing signs of instability such as collapsing. So, triggering an avalanche could be the first sign of instability that you see. It is possible to remote-trigger these avalanches from below, beside, or above steep slopes. Completely avoiding this problem includes avoiding terrain threatened from above.

    Tracks and crown of a large skier-triggered avalanche in backcountry terrain adjacent to Lost Trail that was triggered on March 6th. The avalanche failed around two feet down on a layer of surface hoar that was buried in mid-February.

    Photo: Ben VandenBos

  • Loose Wet

    • Alpine
    • Treeline
    • Below treeline
    Likelihood
    Possible
    Size
    1–1.5

    Even with the cloud cover yesterday, we had reports of small wet loose avalanches and roller balls in the Bitterroot (see observation). We did not see a substantial refreeze overnight, and temperatures are supposed to be even warmer today. Combine that with decreasing cloud cover, particularly in the Southern Bitterroot, and we’re going to see signs of wet snow avalanche problems. This could include wet slabs where prominent weak layers exist, though you’re more likely to observe wet loose avalanches.

    Up high, wind will keep the snow cool, but as you descend out of windy areas you may suddenly find yourself in wet snow, especially if the clouds clear.  Soft new snow can very quickly become wet and unstable as soon as the sun hits. If you see roller balls, or find yourself travelling through wet surface snow, it's time to move to shadier or dryer aspects.

    In places where skies are forecast to be sunnier, like Lost Trail Pass, expect to see wet snow problems right up to ridgetop on southerly aspects.

    Roller balls in the Southern Bitterroot. This indicates wet snow, and is a sign that wet loose avalanches are possible.

Avalanche Discussion

Today will be like yesterday, but with a little bit more of everything – more wind up high and more warmth everywhere. Where yesterday was a stiff moderate at the highest elevations, we’re looking to bump just up into considerable later today thanks to the wind, plus some precipitation forecast for the afternoon. With spring-like temperatures and the strongest gusts existing at ridgetop, the cut-off between middle elevation and high elevation may feel closer to 8000 rather than 7000.

Don’t let the changing surface snow distract you from buried weak layers lurking below. While surface avalanches are plenty dangerous, avalanches failing on deeper layers can do the most damage. Weak layers buried in late January and throughout February include facets, crusts, facet-crust combos, and surface hoar. The exact character changes as you move around the compass.

We’ve seen the weakest stability test results on northerly slopes, and most of last week’s natural avalanches occurred on northeast, east, and southeast aspects (see avalanches here). When dealing with this type of avalanche problem, where exact timing and location is difficult to predict, it's good practice to allow potential consequences to guide decision-making.

With buried weak layers and a wet snowpack, we’re starting to think about wet slab avalanches. These exist as a unique blend between wet loose and persistent slab. They require the same weather conditions as wet loose (sun or rain adding water to the snowpack), but the snowpack structure of a persistent slab problem. Collapses on wet snow are a sign of instability related to wet slab avalanches, rather than wet loose.

If you get out, please continue to send us observations. We appreciate each and every one of them. Click here for our observation form. Today, we’re particularly interested to know about the extent of blowing snow, and the highest elevation at which you find wet snow. Signs of instability and avalanches are always appreciated, as this is bullseye data that helps us write a more accurate forecast.

Regions covered