Lawinenlagebericht

Selkirk Mountains

Idaho Panhandle Avalanche Center
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Lawinengefahr

Thu
Hochgebirge
2 · Mässig
Waldgrenze
2 · Mässig
Unterhalb
1 · Gering
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Veraltet — dieser Lagebericht ist last year abgelaufen. Du siehst vergangene Verhältnisse, nicht den aktuellen Bericht.

Kernpunkte

New dense snow is quickly building shallow, fresh slabs on many slopes. As wind speeds increase over the next 24 hours, this will likely contribute to broader drifting, and fresh slabs may become more reactive along with increasing size. Anticipate deeper, more problematic drifts in avalanche start zones near ridges and in cross-loaded gullies, and where your chance to get caught off guard is elevated. Be on the lookout for signs of unstable snow, and manage your terrain to lower slope angles or sheltered areas if you observe cracking in the new snow.

Lawinenprobleme

  • Storm Slabs

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

    Denser and heavier snow continues for the next couple of days and the Selkirks and West Cabinet mountains are expected to receive an additional 4"-8" of snow by Thursday morning. This new snow is falling on top of an already existing 2"-4" of lighter density snow, creating an inverted slab. New slabs will grow larger and become easier to trigger as the snow totals increase. The largest and most dangerous slabs will be found on areas of the terrain where the wind has drifted the new snow. If travelling on or directly below slopes that exceed over 30 degrees, heed warning signs of instabilities such as cracking within the new snow, or density changes underfoot. If the snow begins to feel hollow and more dense, this is a sign that the snow is becoming more cohesive and forming a slab. Lower angle terrain that is sheltered from the wind will provide the safest riding. 

    Cracking in the new snow suggests that the slab has become cohesive enough to produce an avalanche. Use these clues to help manage terrain. 

    Photo: Micah Krmpotich

Avalanche Discussion

After a taste of first spring, winter is now making a second appearance with the long-term forecast looking promising for more snowfall. Incremental loads of new snow continues to improve the skiing and riding conditions. However, with the new snow comes another breed of avalanche problems.

Sunday night delivered a few inches of lighter density snow, which landed on a variety of snow surfaces. Some solar aspects had developed a crust, while shaded and sheltered pockets of terrain held on to softer snow. Now, warmer temperatures are driving heavier and denser snowfall. This combination has created an inverted slab, which will continue to grow with the continuation of snowfall. Winds are forecasted to increase in the next 24 hours, which will create even larger and more sensitive slabs below ridgelines, and cross loading terrain features such as gullies and sides of steep rock bands. Stay vigilant in observing snow conditions and be ready to retreat to slopes that are less than 30 degrees if you feel drifts becoming larger or experience the telltale signs of slabby snow and cracks underfoot.

Although snow totals are much less impressive at the lower elevation band, temperatures are forecasted to be above freezing. Conditions are expected to be different at the trailhead vs. the peak and will have a noticeable change as you gain elevation. Look for clues on the surface as you work your way through the mountains. If you see large pinwheels gaining in size or gouging the surface at lower elevations, avoid traversing on or below steep slopes.

Looking deeper into the snowpack, we haven’t forgotten about the widely discussed January Drought Layer (JDL). After a long run of listing persistent slab as a problem, we are transitioning to focusing on new snow related avalanche problems. Here’s a quick breakdown of how we arrived here:

  • The month of January consisted mostly of a drought period, where we experienced very little snowfall and a prolonged spell of cold temperatures. This combination “rotted” the snowpack, weakening the snow grains and creating a well-established persistent slab problem.
  • The story changed in February, when the faucet turned back on, and the forecast area saw snowfall once again. The new snow successfully overloaded the weak JDL grains and observations reported a natural avalanche cycle.
  • Towards the end of February, snowfall changed to rain and in the long term this helped stabilize the snowpack. That rain event helped develop a thick and impenetrable crust at mid and upper elevations. Lower elevations saw warmer temperatures and more rain, which penetrated deep into the snowpack and helped wash out most of the weaker JDL layer.

It has now been over 2 weeks since an avalanche has been observed failing on this previously problematic interface. Fast forward to now, and the JDL is buried over a meter deep with a hard slab over top - concealing the buried grains from being influenced by a skier or snowmobiler. The exception to this being specific areas on the slope where the snowpack is significantly shallower, such as around rocky cliff bands and wind scoured pieces of terrain. However, the JDL layer hasn’t completely gone to bed yet. Observations continue to report that even though the drought layer is getting further and further away from the surface, the insulating snowpack is preserving some of the weak grains. This means that if a drastic warm up occurs, this could come back in to play.

**Your observations help us build the next forecast. Share what you see with us and your local backcountry community**

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