Avalanche forecast

Bitterroot

West Central Montana Avalanche Center
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Avalanche danger

Fri
Alpine
2 · Moderate
Treeline
1 · Low
Below
1 · Low
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Highlights

Skiers and riders could trigger pockets of wind slab at upper elevations on east aspects and along the edges of gullies. Avoid wind loaded terrain over 35º. Loose-dry avalanches may need management in steep terrain. Elsewhere the snowpack is generally stable.

Avalanche problems

  • Wind Slabs

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

    At upper elevations, wind slab could be triggered by skiers and riders on east aspects, just below ridges and along the edges of gullies. 

    Today's windslab will most likely be small. However, it could knock you off your feet and carry you into or over hazards. Terrain traps such as gullies increase the risk of burial. The depth of wind slab will grow today with continued winds and snowfall.

    Windlips and cornices indicate wind transport and wind direction. Smooth pillows of snow that may be stiff and hollow sounding indicate the presence of windslab, and shooting cracks are a sign of instability. 

    The best way to avoid triggering a windslab avalanche is to avoid pockets of wind loading over 35º.

  • Loose Dry

    • Alpine
    • Treeline
    • Below treeline
    Likelihood
    Possible
    Size
    1

    Yesterday, low-density snow was sluffing readily on various crusts in the Rattlesnake. Loose-dry avalanches are possible throughout the forecast area today, especially where crusts underlie the new snow. These pose little risk to skiers and riders unless encountered in a terrain trap such as a chute where they are funneled and increase in depth. They could knock skiers off their feet and push them into or over hazards. 

    If you are skiing steep consequential terrain, manage loose dry avalanches by getting out of their way and letting them run.

Avalanche Discussion

Since the last forecast, 1-2” of new snow trickled in. Temperatures remained cool, with limited warming of the snow surface. Winds have been mostly light but increased last night. Westerly winds blew 24-37mph at Point 6 and 20-37mph in the southern Bitterroot. 

Yesterday, observations throughout the forecast area noted no signs of instability, and unstable test results were very isolated. The exception is fresh windslab at upper elevations and loose dry avalanches in steep terrain. 

We are still mapping out the zipper crust laid down last Monday mid-storm. It seems that the Rattlesnake got the worst of it, and it is thinly buried under 4” of low-density snow at all aspects and elevations. It is also present in the northern Bitterroot and Lolo. It is not present on the east side of the Seeley zone, and it is not present in the central Bitterroot. The crust could pose a problem in the future as it gets more deeply buried.

Test results on the crust have been inconsistent, and there have been no slides on this layer. However, it’s worth performing stability tests if the crust is buried and has a cohesive layer of snow over it. Increase caution if there is propagation or soft snow under stiff.

Today, despite mostly stable conditions on non-wind-loaded slopes, continue to practice safe travel, such as skiing one at a time. Check for instabilities before entering steep terrain, and stay alert for red flags, like shooting cracks.

The next round of snow starts this afternoon. The danger will rise by tomorrow morning, with roughly 6” of snow and strong winds in the forecast. Dial back slope angles and avoid wind-loaded terrain if you travel in the backcountry tomorrow. 

Please let us know if you find the Presidents Day zipper crust and how much snow falls today by submitting an observation. 

Ski and ride safe

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