Avalanche forecast

Flathead Range & Glacier NP

Flathead Avalanche Center
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Avalanche danger

Mon
Alpine
3 · Considerable
Treeline
2 · Moderate
Below
1 · Low
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Highlights

Up to a foot of snow fell overnight, with more on tap for today. The avalanche danger may be higher and more widespread than it has been in quite a while. You could trigger slides from gentler terrain below, above, and to the sides of steep slopes. Cracking beneath your skis or machine indicates an instability directing you to lower-angle terrain.

The danger will be lower in areas that only received a few inches of snow, like John F. Stevens Canyon.

 

Avalanche problems

  • Storm Slabs

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

    Around a foot of new snow fell in most mountainous areas over the past 24 hours. This snow rests on soft snow from the past few days above a crust. On some slopes, the snow above the crust is faceted and may allow you to trigger slides remotely. These slides could propagate wider and higher above you than expected.

    Search for relatively stiff, cohesive snow. This will be where your skis, boards, or machine do not sink as deeply into the new snow. Cracking in this snow indicates an unstable slab and directs you to seek out lower-angle terrain.

    (12/23/2022)

    Storm slabs were touchy and failed on a layer of extremely low-density snow.

    Photo: Mark Dundas

  • Loose Dry

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

    At upper and middle elevations, pay attention to slopes with 8 inches or more of new, cohesionless dry snow.  Before you ski or ride slopes steeper than about 35 degrees, consider what terrain features are connected or below you.  Triggering sluff that leads to terrain traps, such as cliffs, tree wells, or gullies can have deadly consequences.  Keep the lure of powder skiing and riding in perspective today.

    (2/28/2023)

    A thin, point release or Loose Dry sluff on a steep slope.

    Photo: sw

Avalanche Discussion

The third time, a charm! The Thursday and Friday storm systems were generally disappointing, but the disturbance that moved into our area mid-day Saturday has delivered. As of 0500 this morning, settled new snow depths at mid-elevation stations are around 9-12 inches in the Whitefish Range, the Swan Range, the Flathead Range, and central Glacier Park. Snow water equivalent (SWE) readings range from 0.7 to 1.0 inches.  Unfortunately, the Highway 2 corridor from John F. Stevens Canyon to Marias Pass only picked up a measly couple of inches. 

Winds have been relatively light over the past 24 hours, except for Aeneas Ridge, where average wind speeds have been 30 mph, well above the minimum threshold of 16 mph required for snow transport. Winds have shifted to the north or east at multiple stations as a weak arctic intrusion moved into the Flathead overnight. This cold air will interact with the relatively warmer, moist air from the Idaho Panhandle, producing light snow throughout the day. Where atypical winds occur, snow will drift onto westerly and southerly aspects. 

The new snow falls on 4 to 12 inches of soft snow, capping a crust. Any slides that occur today should entrain most, if not all, of the new snow above the crust. Observations report the near-surface crust to be relatively strong, but in more extensive terrain, slide debris may break through this crust into weak, faceted snow and produce a larger slide. 

Before the recent stormy period, an extensive dry snap formed weak, faceted snow or surface hoar on the surface in various locations. Observations over the past few days report mostly stable conditions with minimal instability (Observation, Observation, Observation). However, we remain concerned that today's slabs may be resting on this weak snow. On these slopes, slides may behave more like a Persistent Slab avalanche and could be triggered remotely from relatively flat terrain above, below, and to the sides of steep slopes. Resulting avalanches may break wider and higher than expected. 

 

 

Regions covered