Bollettino valanghe

Silver Valley & Bitterroot Mountains

Idaho Panhandle Avalanche Center
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Pericolo valanghe

Sat
Alta quota
2 · Moderato
Limite del bosco
2 · Moderato
Sotto il limite
1 · Debole
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Non aggiornato — questo bollettino è scaduto 5 years ago. Stai vedendo condizioni passate, non il bollettino in corso.

In sintesi

New snow available for transport and strong wind = wind slabs. With new wind slabs and several layers of concern in the upper snowpack, the snowpack is becoming more complicated. Overall stability seems fair , but caution and smart terrain choices are warranted. Understanding the avalanche problems will help you to mitigate risk by picking routes that minimize your exposure.

Expect to find wind slabs on north and east aspects at upper elevations. Surface hoar is buried 1-2 feet deep on specific north aspect slopes. Buried persistent layers are most likely to fail on unsupported convex roll-overs and slopes on northerly aspects that tend not have bridging crusts above the weak layer.

Problemi valanghivi

  • Wind Slabs

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

    The new snow was easily transported by wind that was howling out of the west-southwest yesterday afternoon. This new snow will form soft slabs on the surface over older hard slabs.

    Wind slabs are likely on the lee side of ridge lines, which currently tend to be north through east aspects, and terrain features like gullies. Although relatively small, if triggered they could sweep a rider off their feet and into terrain traps below, or step-down to deeper buried persistent weak layers.

    (2/17/2022)

    Ski pole weather veins! Gusts up to 32mph.

    Photo: Mikey Church

  • Deep Persistent Slabs

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

    Buried surface hoar remains a concern on open wind sheltered north aspect slopes. These are places that bridging crusts have not developed and the snow remains soft down to the weak layer.

    We are also finding more developed weak facets associated with the January crusts buried 40-50cm from surface. These are more likely found on solar aspects, but are masked by the bridging strength of more recently formed crusts above this layer.

    This might be starting to sound like a broken record. That is the nature of buried persistent weak layers: they can remain hidden and quiet, not providing feedback, for weeks or months. These layers are showing moderate reactivity in Compression Tests. Even though they did not propagate in our stability tests, I am wary and uncertain of these layers.

    (2/17/2022)

    Not the best pic ever, but this is the buried surface hoar we keep talking about. Can you see the striated plates and geometric crystals? I found these on a wind sheltered north aspect at mid elevation.

    Photo: Mikey Church

Avalanche Discussion

Yesterday we toured up to Granite Peak from Revett Lake. Surface conditions were variable, ranging from wind scoured hard crust and wind stiffened slabs, to soft new snow on sheltered mid elevation slopes and in the trees.

The forecast today is tricky because overall stability seems fair to good , but there are a number of avalanche problems and weak layers that, if triggered, could have serious consequences.

On a steep slope I did trigger a very small 4” storm slab on unsupported snow between ski cuts. And yesterday I found buried surface hoar in a north aspect open bowl that was sheltered from wind by cliffs and steep terrain above. The snow was soft, and it would be tempting to ride that terrain.

Today’s high could reach into the 40’s, so pay attention to signs that likelihood of wet slides is increasing as the day goes on: snow clumping on your skis and skins, tree bombs and rollerballs.

Looking ahead, the weather will be changing over the coming days: warm spring like conditions shift to arctic cold. Anytime the weather changes drastically in a short timeframe caution is warranted as we wait to see how the snowpack responds.

 

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