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Avalanche Forecast

Archived

Mar 20th, 2025–Mar 21st, 2025

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

Regions

Little Yoho.

Due to limited field observations, the likelihood of triggering large avalanches on persistent weak layers in this region is uncertain.

Conservative decision-making is recommended.

Confidence

Moderate

Avalanche Summary

No new avalanches were observed in Little Yoho. On Wednesday, avalanche control on Mont Field and Dennis produced avalanches to size 2.5 on the persistent layer.

Over the past two weeks, many large avalanches have been seen in adjacent areas to the East of the divide. See Banff bulletin for details.

Snowpack Summary

At treeline, 70-100 cm of snow overlies the Jan. 30 / Feb. 22 drought layers, which consist of 20-30 cm of weak faceted crystals. These layers have been reactive in tests and recent avalanches. Average snowpack depth at treeline is ~200 cm.

In this thicker snowpack region, the facet/depth hoar basal layer is less prominent than it is East of the divide but likely exists in thin areas. Expect a surface crust on solar aspects at treeline and below.

Weather Summary

Friday - 5 cm of snow, moderate winds, and mainly cloudy. Treeline high temperatures around -4C.

Saturday - Trace amounts of snow and light to moderate winds.

See below for more details

Terrain and Travel Advice

  • Make conservative terrain choices and avoid overhead hazard.
  • Loose avalanches may step down to deeper layers, resulting in larger avalanches.
  • Wind slabs are isolated, but may remain reactive.

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.