Bollettino valanghe

Banner Summit

Sawtooth Avalanche Center
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Pericolo valanghe

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Alta quota
1 · Debole
Limite del bosco
1 · Debole
Sotto il limite
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In sintesi

Triggering a large avalanche is unlikely. Continue to use extra caution on very steep, rocky, wind-affected slopes. Small but sensitive wind drifts formed yesterday—watch for these along upper elevation ridgelines. Sunny slopes will be frozen this morning, but be ready to head for colder slopes if surfaces become wet and mushy later today.

Problemi valanghivi

  • Persistent Slabs

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

    We've been plagued by persistent weak layers the entire season. First by early-season facets near the ground, then by weak layers that were buried in late-January and February. Warm temperatures and a lack of loading over the past week have finally given these layers the breather they need. These weak layers still exist on most slopes, but observations from across the forecast area indicate that triggering a persistent slab avalanche is unlikely.

    There are two types of snowpacks in this world: those with persistent weak layers, and those without. Even if both snowpacks are considered "stable", I'd choose the one without weak layers every single time. So what I'm saying is—don't let your guard down. Even though triggering a persistent slab avalanche is unlikely, that's not the same as impossible. There's still a small chance of triggering a persistent slab avalanche on very steep (approaching 40 degrees), rocky, wind-affected slopes. Terrain like this is most common at upper elevations and especially in the alpine. 

    ADDITIONAL DISCUSSION:

    • The 1-2" of snow that fell yesterday was blown into small, thin drifts along upper elevation ridges. Observers on Banner Summit yesterday reported that these were touchy.
    • Given a hard freeze overnight and cooler temperatures expected today, wet snow avalanches are unlikely to be a significant problem. Still, if your backcountry travels take you onto steep, sunny slopes, be sure to monitor crusts as they soften through the day. If you find you're beginning to punch through the thawing crust or the surface has become wet and mushy, head for colder slopes. Wet snow will be more common at middle and especially lower elevations, so don't forget about the terrain you need to travel through on your exit later in the day.

    (3/5/2021) Persistent weak layers in the Banner Summit zone are unlikely to produce avalanches - but they're still there. Here, a layer of surface hoar 3' down didn't fail during a snowpack test, but sheared when the block was pried out of the column. N, 8400'.

Avalanche Discussion

Today the avalanche danger is rated LOW—the first time since December 16th! A winter of exceptionally unstable conditions has left many folks chomping at the bit to ski or ride in steeper terrain. As an avalanche forecaster, dropping the danger rating is intimidating. It conjures up images of "opening the floodgates"—people flocking to avalanche terrain with reckless abandon. For obvious reasons, we hope this isn't the case.  Remember the old adage: LOW danger does not equal NO danger. Here are some tips for managing the lingering avalanche hazard:

  • Read the forecast carefully to understand where there are still avalanche concerns. Even the definition of LOW danger states "Watch for unstable snow on isolated terrain features." Continue to factor these into your travel plans.
  • Speaking of plans, continue to make a travel plan with your partners that clearly defines what terrain is "off-limits". Once in the backcountry, stick to your plan and be prepared to step back if you see something you didn't expect.
  • Evaluate terrain carefully, and never stop paying attention to consequences. If you're considering riding or skiing a slope where triggering a slide would likely be fatal or result in a deep burial, you need to be very, very confident in the snowpack stability. If there's any question, choose lower consequence terrain.
  • Continue to use safe travel practices. Decreasing danger can result in folks entering avalanche terrain MORE often but using safe travel practices LESS often—a bad combination.

To summarize: keep doing what you've been doing all winter. The terrain you play in may change, but your practices, rituals, protocols, and systems should stay the same. Don't get sloppy—keep it tight!

Be sure to check out Ben's latest installment of our Weekend Update.

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