Bollettino valanghe

Selkirk Mountains

Idaho Panhandle Avalanche Center
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Pericolo valanghe

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

In sintesi

New snow and variable winds formed fresh slabs on many slopes. These slabs may be located lower in the terrain or on atypical slopes after Friday's easterly winds. Avalanches could be easier to trigger, larger, and potentially more dangerous on upper elevation slopes with around 8 inches of dense snow sitting above softer snow. To avoid these more concerning drifted slabs, stick to sheltered slopes and go around steeper areas if you see cracking in the snow or if the surface looks smooth and rounded. 

Problemi valanghivi

  • Storm Slabs

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

    Today, most slopes harbor 3 to 7 inches of dense new snow that fell Friday resting on top of dry, softer snow that fell earlier in the week. Avalanches in the new snow will generally be small, but they could grow larger on slopes with broader, deeper wind-drifting. Northerly and easterly winds on Friday may have formed problematic drifts on slopes that you aren't accustomed to seeing them. You will likely encounter freshly drifted slabs on southwest through west to northwest-facing slopes - particularly near ridgelines.

    Storm snow hazards at lower elevations could pose an elevated concern where winds cross-loaded slopes and gullies. Look for signs of unstable snow like recent avalanches, stiff or hollow-sounding snow, and cracks shooting through the snow surface. Use caution on slopes around 35 degrees where you find evidence of unstable snow, and go around steep, convex rollovers.

    Due to the way the last two storms played out, heavy snow over softer, lower-density snow could be more reactive with lesser new accumulations. If in the wrong spot, these could quickly catch you off guard, knock you over, and push you somwhere you don't want to go. Use extra caution traveling above rock bands or terrain traps where a small slide stuffing you in the wrong spot could carry higher consequences.

  • Persistent Slabs

    • Alta quota
    • Limite del bosco
    • Sotto il limite del bosco
    Probabilità
    Possible
    Dimensione
    2–3

    Faceted grains persist around several older rain crusts, creating a weak and slippery sliding interface that extends two to three feet deep across our forecast zones. Before the current storm, the slab directly above both crusts had settled and strengthened more than the faceted grains surrounding the crust. Where the crust has degraded and become more breakable, the facets have grown larger and weaker. The increased load from new snow may make these layers more reactive, and it's nearly impossible to predict how close they are to failing.

    While these layers are healing and becoming harder to trigger, exercise caution when traveling near exposed rocks or below cliffs, where it may be easier to impact the weaker snow in these areas. Recent avalanche activity suggests that storm slabs in motion can provoke deeper layers to fail, resulting in a more dangerous avalanche. Persistent slab avalanches can behave unpredictably and span across adjacent terrain features, so treat steeper terrain as suspect until proven otherwise.

     

    (12/31/2024)

    The December 18 rain crust is thin, breakable, and very translucent. It lurks around two feet deep and was stubborn in our snowpack tests. We did observe resistent planar failures with moderate force. Selkirk Mountains. December 31, 2024.

    Photo: Chris Bilbrey

Avalanche Discussion

New snow last weekend capped off an impressive storm cycle, delivering copious amounts of snow to all mountain regions. After a brief break in the weather mid-week, the snowpack has settled and strengthened. Yesterday and last night, 3-9 inches of heavy, wet snow fell on a soft, cold snow surface. Today, be on the lookout for this setup. It may be worth testing the snow on safe slopes to assess how reactive last night's snow is. As you gain elevation, wind-deposited snow will become a more significant factor. North winds from yesterday filled in low spots and cross-loaded north and east-facing slopes. Be aware of filled-in pockets, gullies, and open slopes that are typically leeward, as they may have newly formed wind drifts and slabs. New wind slabs maybe found near rigelines on slopes that are normally stripped of snow, most likely on Southwest and Westerly slopes.

Interestingly, an IPAC team observed a glide crack yesterday on an east-facing slope in the St. Regis Basin, an area that has produced large avalanches in the past. While this may appear to be an anomaly, please submit an observation if you find one as you are out and about. Glide cracks are known to spontaneously avalanche, so avoid traveling on or below them if you encounter one.

Looking ahead, expect avalanche danger to increase tomorrow (Sunday) with the possibility of an additional foot of new snow and a rising snowline, potentially bringing rain.

Regioni coperte