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Avalanche Forecast

Archived

Jan 19th, 2025–Jan 20th, 2025

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

Regions

Glacier.

Cold temperatures are the main storyline. Be prepared with extra layers and know how to stay warm if your group has an unexpected hiccup.

The persistent slab that we are tracking, down 30-50cm, is still "popping" in snowpack tests. Be cautious if you encounter a pocket of wind slab in committing terrain.

Confidence

Moderate

Avalanche Summary

A field team conducted explosives testing on steep, northerly Treeline features yesterday. Results up to size 1.5 were observed, with minimal propagation.

On Thursday, there were several large (up to size 2) natural avalanches in the steep terrain on the N face of Mt MacDonald. These were triggered by the extreme SW winds (up to 125km/hr!)

Snowpack Summary

~10cm of cold, faceted snow sits atop a denser, wind-pressed layer. Below this lies a weak interface (Jan 7th layer) down 30-50cm, comprised of surface hoar (all aspects) and/ or a thin crust on steep S aspects.

In the start zone of Mt Fidelity, moderate "resistant" and "sudden planar" snowpack test results were found down 30cm. We are keeping an eye on this persistent layer as the snowpack builds on top of it.

Overall the mid and lower snowpack is strong and well settled.

Weather Summary

Continuing cold, clear, and calm.

Tonight Clear periods. Alpine low -15°C. Ridge winds W-10km/h.

Mon Mainly sunny. Alpine high -13°C. Light SW wind. Alpine temp inversion.

Tues Cloud, sunny periods, isolated flurries. Alpine high -12°C. Winds W 20 gusting 50km/h.

Wed Sun and cloud. Alpine high -8°C. Winds W 10-20km/h.

Terrain and Travel Advice

  • Be especially cautious as you transition into wind-affected terrain.
  • Watch for signs of instability like whumpfing, hollow sounds, shooting cracks, or recent 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.