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Avalanche Forecast

Archived

Apr 16th, 2024–Apr 17th, 2024

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

Regions

Banff Yoho Kootenay, Little Yoho, Banff, East Side 93N, Kootenay, Lake Louise, LLSA, Sunshine, West Side 93N, Field.

A short return to winter has given us 5-15 cm of new snow, depending on location. Just enough for a refresh, although the spring crust is just under the surface. The next few days look good as the skies clear and temperatures remain cool with north winds, then the next spring warm-up happens through the weekend and into next week.

Confidence

Moderate

Avalanche Summary

Thin (5-10 cm) and soft windslabs and sluffs to size 1 were easily triggered today on open slopes from new snow and wind loading. The cool temperatures have temporarily slowed down the deeper avalanche activity, but expect this to spike up again when it warms up or gets direct sun. During the last warm spell, many avalanches stepped down to the Feb. 3/basal facet layer (See photos). These were a combination of solar triggered or cornice triggered on polar aspects.

Snowpack Summary

5-10 cm of new snow now covers previous surfaces of crust and wind effect. Small windslabs have formed in isolated areas above treeline and will react easily to human triggers since they're on a smooth crust - but the avalanches are small. The midpack is well settled down to the Feb 3 persistent weak layer which remains a concern in shallow snowpack areas on northerly alpine aspects. In these areas, no crusts are found in the upper snowpack and the midpack remains thin and weak.

Weather Summary

Tuesday's storm will end overnight and clearing arrives on Wednesday, setting up for a week of mostly sunny and slowly warming weather ahead. Wednesday will remain mostly cool except in the direct sun with freezing levels at 1600 m and moderate N winds keeping the snow cold. Then look for gradual warming starting Friday and with warm spring weather ahead next week.

Terrain and Travel Advice

  • Watch for wind-loaded pockets especially around ridgecrest and in extreme terrain.
  • Loose avalanches may start small but they can grow and push you into dangerous terrain.

Problems

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.

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.