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Avalanche Forecast

Archived

Mar 8th, 2024–Mar 9th, 2024

Alpine
Natural avalanches possible, human triggered probable.
Treeline
Natural avalanches possible, human triggered probable.
Below Treeline
Natural avalanches unlikely, human triggered possible.
Alpine
Natural avalanches possible, human triggered probable.
Treeline
Natural avalanches possible, human triggered probable.
Below Treeline
Natural avalanches unlikely, human triggered possible.
Alpine
Natural avalanches possible, human triggered probable.
Treeline
Natural avalanches possible, human triggered probable.
Below Treeline
Natural avalanches unlikely, human triggered possible.

Regions

Glacier.

We haven't had significant snowfall in awhile, but it is not time to start stepping out yet.

Skiers/riders could still trigger large avalanches on the persistent weak layer.

Make plans to ski conservative slopes with limited overhead exposure, and stick to them.

Confidence

Moderate

Avalanche Summary

On Thursday, we observed fresh naturally triggered size 3 slab avalanches from Catamount Mtn SE face and Mt. Leda NE face. These were both deep slabs, suspected to have failed on the Feb 3rd crust.

On Monday, a field crew remote-triggered a sz 1 on the Feb 3 crust while approaching a snow profile site.

We continue to see daily reports in the region of human triggered avalanches on the Feb 3rd layer.

Snowpack Summary

Intense spring sun has created a thin surface crust on South & West aspects.

Variable winds have created soft wind slabs at ridgetop on most aspects. Expect significant wind effect below glaciers due to strong downflow winds.

80-140cm of settled snow sits atop a sugary facet layer. These facets are not bonding well to the widespread, very firm crust from Feb 3rd. This crust is a significant persistent weak layer and will be the main layer of concern for the foreseeable future.

Weather Summary

A cold front moving inland gives modest snowfall amounts and increasing winds Saturday afternoon into Sunday.

Tonight: Clear periods. Alpine low -6°C. Light Southerly ridgetop winds.

Sat: Cloudy, pm flurries (5-10cm). Alpine high -1°C. Freezing level (FZL) 1800m. Increasing SW winds (extreme gusts by the PM).

Sun: Flurries (5-10cm). Low -9°C, High -5°C. Gusty mod SW winds.

Mon: Flurries (~5cm).

Terrain and Travel Advice

  • Use conservative route selection. Choose simple, low-angle, well-supported terrain with no overhead hazard.
  • Remote triggering is a concern, avoid terrain where triggering slopes from below is possible
  • If triggered, wind slabs avalanches may step down to deeper layers resulting in larger avalanches.

Problems

Persistent Slabs

Persistent Slab avalanches are the release of a cohesive layer of snow (a slab) in the middle to upper snowpack, when the bond to an underlying persistent weak layer breaks. Persistent layers include: surface hoar, depth hoar, near-surface facets, or faceted snow. Persistent weak layers can continue to produce avalanches for days, weeks or even months, making them especially dangerous and tricky. As additional snow and wind events build a thicker slab on top of the persistent weak layer, this avalanche problem may develop into a Deep Persistent Slab.

Wind Slabs

Wind Slab avalanches are the release of a cohesive layer of snow (a slab) formed by the wind. Wind typically transports snow from the upwind sides of terrain features and deposits snow on the downwind side. Wind slabs are often smooth and rounded and sometimes sound hollow, and can range from soft to hard. Wind slabs that form over a persistent weak layer (surface hoar, depth hoar, or near-surface facets) may be termed Persistent Slabs or may develop into Persistent Slabs.