Bollettino valanghe

Silver Valley & Bitterroot Mountains

Idaho Panhandle Avalanche Center
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Pericolo valanghe

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

In sintesi

Fresh snowfall and a gradual rise in temperatures over the next 24 to 48 hours may help lingering weak snow layers in the upper snowpack become more reactive. Despite lesser expected snowfall than the Northern Mountains, increasing winds will aid deeper slab formation on northwest through north to southeast-facing slopes above 5,500 feet. Approach steep and open slopes cautiously, and watch for signs of unstable snow like shooting cracks, audible whumpfing, or recent avalanches.

Problemi valanghivi

  • Persistent Slabs

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

    Weak layers - surface hoar, faceted grains, and a faceted crust - around two feet deep are the culprit of lingering instability in the upper snowpack. Snowpack tests on slopes near treeline down to about 5,500 feet continue to produce ongoing failures in these weak grains - albeit with harder force. You may find isolated places with buried surface hoar 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, the ability to affect weaker snow and trigger a slide appears directly influenced by overlying slab depth.

    Photo: Izzy Davis

  • Wind Slabs

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

    Don’t be complacent if you only find a couple inches of new snow, as increasing winds will aid deeper slab formation on leeward-facing slopes above about 5,500 feet. Areas directly below ridgelines and on sidewalls of gullies are where you can anticipate deeper drifts. Approach steep and open slopes cautiously, and watch for signs of unstable snow like shooting cracks, audible whumpfing, or recent avalanches. If you notice the snow surface quickly transitions from soft to hard or you barely make an impression on the snow surface, you are likely on top of a hard, problematic slab.

    (1/21/2025)

    It will be very easy to trigger avalanches in the new snow. Fresh slabs of snow are overloading fragile weak snow layers directly below. Bitterroot Mountains. January 21, 2025.

    Photo: Izzy Davis

Avalanche Discussion

Managing newly emerging surface problems will help you avoid the sleeping snowpack dragon deeper within. The next round of snow arrives with much warmer air. While we expect the snow line to be well below our bottom forecast elevation of 4,000 feet, snow densities will likely be notably higher than the last several storms. This will quickly form fresh cohesive slabs on the surface with potentially lesser new snow depths. As you move closer to the treeline and above, you may start to encounter more wind-drifted, slabby conditions and where terrain management may need adjusting. Lens-shaped pillows, fresh cornice growth, and the snow surface becoming harder and hollow sounding should clue you into the more worrisome places.

As the snowpack gets exposed to much warmer air in the coming days, it will likely promote additional settling and stiffening of the upper snowpack. This could make buried surface hoar or faceted grains more reactive as increasing slab weight further stresses these weaker interfaces. While the forecast staff and public observers continue to report improving conditions, we’re not ready to write off looming concerns just yet. Triggering a dangerous avalanche is still in the cards if you travel on steep, rocky, shallower areas, or where drifting builds uneven slab depths influenced by terrain twists, turns, or bends. 

Despite several days since the last natural or human triggered avalanche, warning signs continue to rear their heads - albeit with less predictable occurrence. With how weak the various flavors of persistent grains were before being buried, treating them as suspect till proven otherwise will help reduce your avalanche risk. If decision-making around stability is too challenging or you observe non-conclusive snowpack evaluations, there’s plenty of excellent riding conditions on lower-angled terrain away from bigger avalanche paths to wait for another day.

Regioni coperte