Bollettino valanghe

Selkirk Mountains

Idaho Panhandle Avalanche Center
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Pericolo valanghe

Tue
Alta quota
3 · Marcato
Limite del bosco
2 · Moderato
Sotto il limite
1 · Debole
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Non aggiornato — questo bollettino è scaduto 8 months ago. Stai vedendo condizioni passate, non il bollettino in corso.

In sintesi

Stiff, wind-drifted slabs now rest above weaker snow layers and crust on leeward-facing slopes. Traveling on northerly and easterly-facing slopes around 35 degrees with more than about 8 inches of new snow increases your chance to trigger a dangerous avalanche, and those slides will be more destructive the deeper they break. Avoid places where you see cracking in the snow or hear audible collapses, and make mindful terrain choices if traveling adjacent or below steeper slopes. 

Problemi valanghivi

  • Wind Slabs

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

    Upper elevations in the Selkirk and West Cabinet Mountains have been able to stay slightly cooler than the southern end of the forecast area, resulting in more widespread snowfall that has been redistributed from winds and drifted into growing slabs. Snow totals in the previous 24 hours amount to 4 to 6 inches and have seen steady winds from the west and southwest. These growing slabs are resting on a variety of surfaces, ranging from weaker faceted snow and surface hoar. Slabs will be most sensitive in places where these weaker snow surfaces exist, on northerly and easterly facing aspects.

    Expect slabs to be more reactive in areas where depths exceed 8 inches below ridgelines and at the top of steep gully features. To identify new wind slabs, look for a textured surface, or feeling a denser slab sitting on top of softer snow-often described as feeling hollow. New cornice growth below ridges can be useful in identifying where wind slabs have developed, and the cornices point to leeward side of the ridge where snow has been drifted.

    Stiff slabs of wind drifted snow will be building throughout the day and increasing in their sensitivity as they gain size.

  • Persistent Slabs

    • Alta quota
    • Limite del bosco
    • Sotto il limite del bosco
    Probabilità
    Possible
    Dimensione
    2–2.5

    Buried faceted crust and surface hoar lurk in the upper snowpack and carry the highest odds to fail from added weight of a rider or machine. Observations on Saturday found that recent rains had not percolated deep enough to wet or disturb an upright layer of surface hoar which was buried overnight on January 1. Additionally, the top 1 to 3 feet below the surface consists of a worrisome mish-mash of rain crust surrounded by fragile faceted grains. 

    Before this storm, these weaker layers had become more stubborn, requiring extra force to provoke a failure in tests. The addition of rain and/ or dense snow will help move these problematic weak layers back toward a more reactive state. As the slab above stiffens from liquid water input or denser snowfall this will help slides break wider than expected and potentially be triggered from farther distances. Be aware of where you are in the broader scope of terrain. Your chances to awaken the sleeping dangers may be higher where the overlying slab is thinner near rocky outcrops, around slab margins, and on the backsides of steep rollovers.

    Multiple faceted crusts exist within the upper 3 feet of the snowpack.  These weak layers will be put to the test today, with the additional weight of new snow, and rain on snow at middle elevations.

Avalanche Discussion

The latest storm is slowly winding down. Top end snow totals landed pretty similar across most of our forecast zones, 8 to 12 inches, but the big discrepancy is where the rain line climbed to. Field observations and second-hand reports suggest the rain line topped out around 5,500 to 5,700 feet in the Northern Mountains but had a more extended period of time above 6,000 feet in the south. To our knowledge, this influenced conditions in slightly different ways.

During high-pressure that closed out 2025, the old snow surface evolved into a variety of forms - surface hoar and small faceted grains on shady and wind-sheltered areas, a thin melt-freeze crust capped sunny slopes, and harder layers were found in more wind-exposed areas. At the onset of snowfall last Friday, 2 to 4 inches of snow fell with generally light winds. This placed a nice blanket over the older snow surface helping preserve some weak, troublesome grains. Then the wind came along with rising snow levels. In our northern areas, initial rainfall was just enough to wet the surface and add extra weight to slabs, but rainfall in the south - while overall light - appears to have penetrated deeper into older snow layers and possibly disturbed those troublesome grains.

Observations over the weekend found increasing sensitivity where buried weak snow layers like surface hoar and facets remained preserved but were not happy with the added weight above. Throw in drifting of dense snow on the surface and snowpack tests started propagating in less than 24 hours from the rapid load - commonly failing in a layer of buried surface hoar. Where the water front made it deeper from prolonged rains, those looming layers below did not demonstrate the same increase in sensitivity from the new load. Regardless, this interface is shallow and easy to dig to and evaluate before making a final terrain decision.

What has been constant is faceted grains surrounding the Christmas-Grinch crust continue to perform despite the new flavor of snowpack weight. Observations in our northern and southern areas continue to report concerning results in failures in any one of the many faceted crust in the top 2 to 3 feet of the snowpack. Some tests will produce a propagating failure while another doesn’t, and compression tests vary between sudden collapse and sudden planar failures. This points to lingering potential for shallower failures to provoke a deeper failure and more dangerous avalanches. The caveat is natural avalanche activity has been almost non-existent and free feedback has almost disappeared as well.

Following such rapid snowpack change from varying types of water input (snow, rain, or wintry mix) and shallowly buried faceted grains, an extra cautions mindset remains prudent. Evaluate the consequences of the terrain you travel above, through, or below and how wide an avalanche could break. Now that mid and upper elevation start zones and slopes are more broadly connected, potential avalanche size increases with each new load as long as persistent weaknesses linger below. Places that have avoided recent rains and harbor a deeper overall snowpack, faceting in the snowpack has been less pronounced recently and individual layers there are better bonded.

Regioni coperte