Avalanche Forecast

Archived

Jan 1st, 2022–Jan 2nd, 2022

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 possible, human triggered probable.

Below Treeline

Natural avalanches unlikely, human triggered possible.

Alpine

Natural avalanches unlikely, human triggered possible.

Treeline

Natural avalanches unlikely, human triggered possible.

Below Treeline

Natural avalanches unlikely, human triggered possible.

Regions

Purcells.

Forecast snow and strong southwesterly winds on Sunday are expected to form fresh wind slabs on lee features at treeline and above.

Watch for newly formed and reactive wind slabs as you transition into wind affected terrain.

Confidence

Moderate - Uncertainty is due to the timing, track, & intensity of the incoming weather system.

Weather Forecast

SATURDAY NIGHT: Cloudy with isolated flurries; 0-5 cm / Strong southwest wind / Low of -21

SUNDAY: Snow; 5-15 cm / Strong southwest wind / High of -14

MONDAY: Snow; 5-15 cm / Moderate southwest wind / High of -9

TUESDAY: Cloudy / Light west wind / High of -10

Avalanche Summary

No new avalanches were reported on Friday.

We've had consistent reports of persistent slab avalanches on reloaded bed surface crusts from the Invermere area this month. On Thursday, a size 1 was triggered remotely by bootpacking on a thin northeast aspect in the alpine. Explosive control work on December 26th produced large avalanches (size 2) on the crust found 40-70 cm deep.

Snowpack Summary

Forecast snow and strong southwesterly winds on Sunday are expected to form fresh wind slabs on lee features at treeline and above.

A layer of weak surface hoar crystals may exist under the recent snow at treeline and below.

The most notable layer of concern in the snowpack is a crust that was formed in early December and is now down 60-120 cm. 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.

A late October facet/crust layer sits at the bottom of the snowpack above 1900m.

Terrain and Travel

Watch for newly formed and reactive wind slabs as you transition into wind affected terrain.
Fresh wind slabs will likely form throughout the day, diligently watch for changing conditions.
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 steep, rocky, and wind effected areas where triggering slabs is more likely.

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.