Avalanche forecast

Seeley Lake

West Central Montana Avalanche Center
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Avalanche danger

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

Windslab will build throughout the day with moderate southwest winds and strong gusts. As wind slabs build, avoid loaded slopes greater than 35º.  Instabilities are isolated to the surface and new snow in most areas. The southern Bitterroot is the exception, where persistent slab avalanches are possible above 7,500 feet. Facets buried 36 inches deep could be triggered from above, below, and to the sides of steep slopes resulting in large destructive avalanches. Avoid slopes over 30 degrees in this zone. 

Avalanche problems

  • Wind Slabs

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

    Plenty of snow remains available for wind transport, and the potential for wind slabs will build throughout the day. We will have moderate winds with high gusts from the southwest as the storm approaches. When the arctic air mass moves in sometime tomorrow or early Monday expect the wind to shift to the north and east. 

    Signs that wind slabs have formed include cornices above the slope, hollow-sounding pillows of drifted snow, and shooting cracks on small loaded test slopes. As wind slabs build, avoid wind-loaded slopes greater than 35º.

  • Persistent Slabs

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

    Persistent slab avalanches are possible in the southern Bitterroot at elevations above 7,500 feet, especially on shaded aspects where old snow sits at the base of the snowpack. A layer of facets three feet deep rests atop the hard basal crusts buried in early December. Stability tests failed on this buried weak layer. Further investigation is warranted for travel on slopes steeper than 30°. Careful travel considerations are necessary. Avalanches may be triggered from flatter terrain below, above, and to the sides of steep slopes. Slides on this layer would be large and destructive.

Avalanche Discussion

The last week can be characterized by active snowfall and generally light winds, primarily south and west. Temperatures have remained relatively mild, allowing the snowpack to settle and bond well. It is generally stable, and instabilities are isolated to the surface and new snow in most areas. 

Elevations above 7,500 feet in the southern Bitterroot are the exception. A layer of facets three feet deep rests atop the hard basal crusts buried in early December. Stability tests failed on this buried weak layer 2 to 3 feet deep. 

A brief period of high pressure moved in yesterday, beckoning clear skies and shifting winds. With clear skies and calm winds, surface hour development might be possible in isolated areas last night, depending on cloud cover. It poses no risk today but is worth watching if it gets buried.

Expect stormier weather to return this weekend as a system from the west interacts with an arctic air mass moving in from the north. Our forecast area may not see snow today, but winds and cloud cover will increase as the storm approaches. The bulk of the precipitation will arrive on Sunday and Monday. Accumulations in the 12 to 24-inch range are possible by Monday, with the Bitterroot favored to receive the most. Southwesterly winds will be strong. 

Despite the new snow, many obstacles are still barely hidden. As the snowpack continues to settle, care is still warranted to avoid injury from unexpected contact with rocks, stumps, and small trees. 

Many thanks to the folks who have been submitting observations. They are extremely helpful for assessing conditions throughout the forecast area. Please continue to submit them here:

https://missoulaavalanche.org/submit-an-observation/

Ski and ride safe.

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