Bollettino valanghe

Whitefish Range

Flathead Avalanche Center
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Pericolo valanghe

Fri
Alta quota
2 · Moderato
Limite del bosco
1 · Debole
Sotto il limite
1 · Debole
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Non aggiornato — questo bollettino è scaduto 2 years ago. Stai vedendo condizioni passate, non il bollettino in corso.

In sintesi

You could trigger an avalanche 1 to 2 feet deep on steep slopes at mid- and upper elevations. Slabs will be thicker and more sensitive where wind has drifted recent snow. Choose low angle terrain if you find stiff snow that supports your weight or cracks around your feet or machine.

Problemi valanghivi

  • Persistent Slabs

    • Alta quota
    • Limite del bosco
    • Sotto il limite del bosco
    Probabilità
    Unlikely
    Dimensione
    1–2

    Your best chance of triggering an avalanche on a buried weak layer will be on slopes where February's snowfall has settled into a cohesive slab above weak facets and surface hoar formed in January. Slopes with snow stiffened by recent winds are prime candidates. Slabs could break 1 to 2 feet deep, or deeper in wind-favored locations. Recent observations have featured buried surface hoar on shaded aspects, propagating pit tests on slopes facing south and east, and isolated collapsing on weak layers.

    Use thoughtful terrain selection to lessen the chances (or the potential consequences) of getting surprised. Choose planar slopes, where an accidental slide will not sweep you over a cliff, through trees, or into a ditch. When in doubt, defer to low-angle terrain. Steep roll-overs or slopes that have variable snow depths due to wind scouring and drifting are likely places trigger points.

    (2/6/2025)

    Propagating pit test results suggest weak layers may be sensitive to human triggering. This extended column test failed on facets formed in January.

    Photo: Flathead Avalanche Center

Avalanche Discussion

A couple items to note today:

  1. We removed Wind Slab from the Whitefish Range. Aside from a few moderate gusts, southwest winds have been light. Continue to look for isolated wind-affected features along exposed ridges or in open alpine bowls. Also, recall that the developing Persistent Slab problem could be more reactive on slopes where recent snowfall has been stiffened by wind. 
  2. On Tuesday, a party in the northern Flathead Range  reported large (D2) sluffs on a steep convexities. Manage this hazard by descending diagonally across slope so that loose snow sluffs beside you instead of over you. Sluff will be largest on very steep sustained slopes and in confined terrain features. Even small slides can have severe consequences if you are knocked off your line and carried over a cliff, through tight trees or deposited in gully, where snow can pile up deeply.
  3. Weak snow formed in January (and buried in February) is widespread in all zones and may be trending towards reactive (obs). 

With snowfall in the forecast and weak layers in the snowpack, expect increasing avalanche danger into next week. 

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