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Avalanche Forecast

Archived

Dec 31st, 2021–Jan 1st, 2022

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

Regions

Lizard-Flathead.

Watch for fresh wind slab formation if you notice the wind pick up. Check out the latest Forecasters' Blog for tips on managing the ongoing persistent slab problem in this region.

Confidence

Moderate - Uncertainty is due to the fact that persistent slabs are particularly difficult to forecast.

Weather Forecast

Friday night: Clear. Light northwest wind. Alpine temperature around -25 C.

Saturday: A mix of sun and cloud. Moderate northwest to southwest wind. Alpine high around -18 C.

Sunday: Increasing cloud with flurries starting in the afternoon. Strong southwest wind. High of -10 C.

Monday: 10-20 cm new snow. Strong southwest wind. High of -7 C.

Avalanche Summary

On Thursday, small (size 1) natural and artificially triggered wind slabs were reported in the alpine.

A few surprisingly deep older crowns were observed between Fernie and Sparwood on Friday. These suspected persistent slab avalanches likely ran on the early December crust around the same time as the explosive triggered size 3 persistent slab reported on December 27th.

Snowpack Summary

Recent winds have created wind slabs on a variety of aspects and created a lot of variability in the upper snowpack.

The most notable layer of concern in the snowpack is a crust that was formed in early December and is now down 80-150 cm. The most recent reported avalanche on this layer was on December 27th. Activity on this layer has been sporadic. It has generally been triggered on steep, rocky slopes, with a shallow or thin to thick snowpack.

This layer has created a low likelihood, high consequence scenario which is best managed through conservative terrain choices and disciplined backcountry travel techniques.

Terrain and Travel

  • Pay attention to the wind, once it starts to blow fresh sensitive wind slabs are likely to form.
  • Seek out wind sheltered terrain below treeline where you can avoid wind slabs and find great riding.
  • Be aware of the potential for large avalanches due to the presence of a persistent slab.
  • Avoid shallow, rocky areas where the snowpack transitions from thick to thin.

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.