Bollettino valanghe

Silver Valley & Bitterroot Mountains

Idaho Panhandle Avalanche Center
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Pericolo valanghe

Wed
Alta quota
2 · Moderato
Limite del bosco
2 · Moderato
Sotto il limite
2 · Moderato
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Non aggiornato — questo bollettino è scaduto 3 years ago. Stai vedendo condizioni passate, non il bollettino in corso.

In sintesi

Recent rain at all elevations that saturated the snowpack combined with continued above freezing temperatures will create the possibility for widespread wet loose avalanches today. The added weight from rain and meltwater has the potential to reawaken persistent weak layers that are located near the bottom of the snowpack. Careful route selection and cautious exposure to steep terrain will be important for avoiding these hazards. 

Problemi valanghivi

  • Loose Wet

    • Alta quota
    • Limite del bosco
    • Sotto il limite del bosco
    Probabilità
    Possible
    Dimensione
    1–1.5

    Rain at all elevations has made a wet top layer of the snowpack. Warm temperatures and no overnight freezing are also contributing to wet and weak snow on the surface. Human triggered Wet Loose slides are possible on slopes steeper than 35 degrees. A small slide of wet heavy snow can knock you off your feet or move your sled around; being punched into trees or over cliff bands will increase consequences. Avoid Wet Loose by recognizing steeper slopes where these features exist.

  • Persistent Slabs

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

    Recent rain has added weight while decreasing snowpack strength. A couple notable weak layers are currently present. Surface hoar from early January may still be found down 1.5 - 2 feet. Late November surface hoar and small faceted weak grains are found 2.5 - 3 feet down. Propagating test results are shown in the late November faceted weak grains holding a three foot thick slab sitting atop, see video (1/30/24) in this forecast.

    Long term relatively warm temperatures within the snowpack (at or just below freezing), as seen recently, will help strengthen weak snow grains over time. The snowpack still needs time to gain strength at this depth.  Keep these persistent weak layers in mind while being intentional with terrain and route selection.

    Photo: Micah Krmpotich

Avalanche Discussion

Recent rain from the weekend and sustained above freezing temperatures have taken its toll on the snowpack and conditions are changing rapidly. All elevations saw rain from the most recent storm and unseasonably spring like conditions have created the possibility for widespread wet loose avalanche hazards. A seemingly inconsequential wet loose avalanche can quickly become dangerous if it entrains more dense wet snow with it and knocks you off your feet, particularly in steep or rocky terrain. Wet snow avalanches are often tricky to predict, and the only real way to avoid them is to stay away from steep (over 30 degree) slopes. Being mindful of warning signs of wet loose avalanches are important if you choose to recreate in avalanche terrain. Seeing pinwheels that gain in size as they roll downhill and being able to effortlessly penetrate to ground in saturated snow using a ski pole or boot are indicators that it's a good idea to enjoy some lower angle terrain. 

The added weight to the snowpack from rain and meltwater have proven that it is enough to stress out deeper buried weak layers located in the lower portion of the snowpack. Stability tests performed yesterday showed that the buried surface hoar from November 24th and the facets at the base of the snowpack are now becoming reawakened and producing propagation. These instabilities failed in multiple extended column tests with moderate and hard force. Because these persistent weak layers are located so far down in the snowpack, an avalanche triggered would likely be large and consequential. Cautious route finding and careful snowpack evaluation will be important tools for navigating this problem. It's a good idea to wait to ski or ride in very steep terrain until after the snowpack has a chance to refreeze and stabilize if you observe these buried instabilities.

High pressure and spring weather will continue today, with temperatures getting into the 40's in the mountains. 

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