Lawinenlagebericht

Selkirk Mountains

Idaho Panhandle Avalanche Center
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Lawinengefahr

Tue
Hochgebirge
2 · Mässig
Waldgrenze
2 · Mässig
Unterhalb
2 · Mässig
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Veraltet — dieser Lagebericht ist 2 years ago abgelaufen. Du siehst vergangene Verhältnisse, nicht den aktuellen Bericht.

Kernpunkte

The stubborn slab, weak layer combination in the upper snowpack is best managed through conservative terrain choices. Incremental thickening of fresh slabs on the surface adds another element of concern, one in which triggering an avalanche in the new snow could be the extra nudge to spark a deeper failure and produce a more dangerous slide. Approach steep, open areas with caution and adjust your travels if you hear whumpfing sounds, or see cracking in the snow or recent avalanches.

Lawinenprobleme

  • Persistent Slabs

    • Hochgebirge
    • Waldgrenze
    • Unterhalb der Waldgrenze
    Wahrscheinlichkeit
    Possible
    Größe
    2–3

    Weak layers - surface hoar, faceted grains, and a faceted crust - two to three feet deep are the culprit of lingering instability in the upper snowpack. Slopes near treeline down to about 5,000 feet continue to produce worrisome failures in these weak grains. Surface hoar is most well-preserved on north to east-facing slopes, while southeast through south to west-facing slopes harbor a breakable crust with facets looming above and below. While deeper weak grains are showing evidence of strengthening, they still remain vulnerable to the added weight of a rider or machine - especially where the overlying slab is thinner.

    The spatial distribution of buried weak layers is not consistent across similar aspects/ elevations within our forecast zones. Due to the depth and stiffness of the overlying slab, triggering an avalanche in one of these weak layers will likely result in a large, wide-breaking avalanche. Backcountry users are still reporting signs of instability although natural avalanche activity has waned. Steady as she sails for now, but slab depth appears to directly influence triggering potential and ultimate avalanche size.

    (2/2/2025)

    An example of shooting cracks that extends across the slope. This is a warning sign that a cohesive slab of snow can fail under the weight of a skier or snowmobiler.

    Photo: Micah Krmpotich

  • Storm Slabs

    • Hochgebirge
    • Waldgrenze
    • Unterhalb der Waldgrenze
    Wahrscheinlichkeit
    Possible
    Größe
    1–2

    Since February 14, snow totals range 10 to 16 inches across the Selkirk and West Cabinet Mountains. Snowfall has been accompanied by generally light winds and cold temperatures depositing a pile of goose down feathers. With a plethora of low-density snow on the surface, a subtle uptick in wind speeds will easily drift the new snow into deeper, more cohesive slabs on leeward-facing slopes. Slopes steeper than about 30 degrees with around a foot of new snow are where your odds are highest to trigger a slide in the storm snow. Whether the slide stays confined to the storm snow is the biggest unknown.

    If venturing into steep, open, and wind-sheltered terrain, disturbing the pile of loose, unconsolidated snow may jump start loose snow sloughing. These generally harmless slides can pick up steam quickly and entrain additional snow volume. This poses the greatest risk if you get knocked off your feet above a cliff or pushed into natural obstacles, or stuffed in a terrain trap. Manage your group so you are not above each other.

    (2/1/2025) Small tree bomb slide Photo: PB

Avalanche Discussion

Manage today’s storm snow hazard and you’ll likely avoid the sleeping dragon deeper within. Snow totals since Valentine’s Day are adding up nicely and will continue to stack up with additional snowfall on Monday. Cold temperatures and light winds allowed the snow to mostly fall straight down and you’re more likely to find a pile of goose down feathers than widespread cohesive slabs. As you move closer to the treeline and above, you may start to encounter more wind-drifted, slabby conditions and where terrain management needs to change. Lens-shaped pillows, fresh cornice growth, and a hollow sound below your feet or machine will help clue you into the more dangerous places and where to go around.

After the early-February storm cycle that drove a fast uptick in avalanche conditions after three weeks of high pressure, and one that lasted almost two weeks in time, weak snow layers in the upper snowpack have found a bit of balance. All of our persistent weak grain worries didn’t dramatically go away, they simply are more difficult to affect now that the overlying slab has got stiffer and/ or deeper. Triggering a dangerous avalanche is still a possibility on a steep, rocky, shallow area of the slope, or from wind-drifting building uneven slab depths where the terrain twists, turns, or bends. As temperatures warm in the coming days along with more snow, this may create an inverted “upside-down” slab that’s more reactive than today, and carries a higher chance to step-down into deeper weak layers that you thought were out of question.

Although natural and human triggered activity has waned recently, warning signs continue to rear their heads - albeit with less predictable occurrence. With how weak the various persistent weak layers were before being buried, chances are they will remain in a vulnerable state longer before quieting down or going away completely. If decision-making about stability is too challenging or you observe non-conclusive results from your evaluations, there’s plenty of excellent riding conditions on lower-angled terrain away from bigger avalanche paths to wait for another day.

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