Bollettino valanghe

Northern New Mexico

Taos 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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In sintesi

If the forecast verifies, snowfall today combined with transportable SW winds will load slopes with shallow wind slabs above treeline. These wind slabs may not be bonding well to the older firm surface.  Triggering a persistent slab avalanche remains possible on West through Southeast-facing terrain near and above treeline. Faceted persistent weak layers continue to linger deeper down in the snowpack and have been slow to heal and strengthen. Below treeline the avalanche danger is LOW but continues to remain weak with isolated steep open slopes remaining suspect.  Before committing to a slope, take the time to dig down to assesses if this strong over weak snowpack structure exists. Avoiding being on or connected to slopes steeper than 35 degrees is a great way to stay safe today. Any avalanche triggered has the potential to be large and very dangerous.

Problemi valanghivi

  • Persistent Slabs

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

    Snow and wind today will start to load slopes, especially near and above treeline on the leeward side of ridgelines and cross-loaded slopes.  Faceted weak layers continue to persist in the snowpack and have been slow to heal and strengthen. We are starting to see a lot of variability throughout the snowpack with some slopes still having a shallow snowpack with easier to trigger weak layers. Wind-loaded slopes on the leeward side of ridgelines and in cross-loaded terrain especially near and above treeline have deeper snowpacks (2 m) with harder to trigger weak layers that may just take you finding a likely trigger point where the slab is thinner on the margins of the slab or near rock outcrops.   

    Obvious signs of instability like shooting cracks and loud audible collapses may not be present in travels. Taking the time to dig down deeper into the snowpack is the only way to assess whether this strong over weak snowpack structure exists. To mitigate the hazard, avoid being on or connected to slopes steeper than 35 degrees. 

    A shallower snowpack on a NNE aspect near treeline. Weak faceted snow continues to linger below and above hard slab that formed from previous wind events. With shallow wind-drifted slabs forming today, slopes like this will become increasingly more dangerous.

  • Wind Slabs

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

    If the forecast verifies and we pick up or exceed the 2 to 5 inches forecasted throughout the day, expect wind slabs to develop on the leeward side of ridgelines and cross-loaded terrain features. Transportable wind speeds in the 20 - 30 mph range should easily drift snow into shallow wind slabs.  These slabs will be forming on a variety of different surfaces from crusts, hard wind packed slabs, and near-surface facets and may not be bonding well to these existing surfaces. 

    Pay attention to wind drifted pillows and shooting cracks on the surface.  Avoid steeper slopes where you find 6 or more inches of wind drifted snow.  A wind slab avalanche will be small but has the potential to step down into deeper weak layers creating a larger more dangerous avalanche.   

Avalanche Discussion

After several days of spring-like weather, it'll be nice to see a return to winter.  Today's storm will be the appetizer to the main course later Saturday night/Sunday where we could see a significant storm with upwards of a foot of snow.  The quick-hitting system today should bring a modest 2 to 5 inches of snow with transportable SW winds starting to load slopes and creating wind slabs on the leeward sides of ridgelines and in cross-loaded terrain. This shouldn't be enough to increase the avalanche danger for today, but with more snow in the forecast over the weekend through the beginning of next week, expect to see an increased danger in the coming days!

It's a highly variable snowpack right now, with below and near treeline terrain still incredibly weak and shallow.  Facets and depth hoar continue to make up much of the snowpack and may have a semi supportable melt-freeze crust on the surface from the warm temperatures and sun over the last week.  Today's storm shouldn't be enough to fully stress these weak layers, but in the coming days, this terrain will become increasingly suspect as snow totals add up.  

Above treeline, winds over the last week have created stiff supportable slabs on the surface capping an overall deeper snowpack (2+ meters of snow) on slopes that have not avalanched from the avalanche cycle at the end of January. Faceted weak layers deeper down in the snowpack are still lingering, but in long column tests are taking moderate to hard force to get these layers to fail. It may just take you hitting a "sweet spot" on the margins of the slab or near rock outcrops where the weak layer is easier to impact to get the slope to fail. On slopes that have run, we are finding a shallow overall snowpack, with faceted layers and depth hoar continuing to persist under the old bed surface. Wind drifted snow today may start to build cohesive slabs on top of these fragile weak layers, setting us up for avalanche paths being repeat offenders. As we've seen with natural avalanches over the last week, these slides can be large failing on faceted weak layers on or near the ground.  It's this low likelihood but high consequence scenario that should give you pause before committing to a slope. Obvious signs of instability like cracking and collapsing most likely will not be present, and it may not be the first or second person on the slope to get it to fail. It's this false sense of security that may lure you into steeper more committing terrain. 

Last week was the deadliest week for avalanches in the US in over a century with 15 fatalities (NYT Article).  As a community, we've done a great job of dialing back our terrain as we deal with a scary snowpack structure that has plagued much of the West this season.  Continue to remain diligent and patient as we start to look towards another active weather pattern starting today.  With every loading event this season we've seen an uptick in avalanche activity.  Expect that trend to continue over the weekend as snow totals add up.    

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